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Sample records for gaas atomic layer

  1. Photoelectrochemical Water Oxidation by GaAs Nanowire Arrays Protected with Atomic Layer Deposited NiO x Electrocatalysts

    Science.gov (United States)

    Zeng, Joy; Xu, Xiaoqing; Parameshwaran, Vijay; Baker, Jon; Bent, Stacey; Wong, H.-S. Philip; Clemens, Bruce

    2018-02-01

    Photoelectrochemical (PEC) hydrogen production makes possible the direct conversion of solar energy into chemical fuel. In this work, PEC photoanodes consisting of GaAs nanowire (NW) arrays were fabricated, characterized, and then demonstrated for the oxygen evolution reaction (OER). Uniform and periodic GaAs nanowire arrays were grown on a heavily n-doped GaAs substrates by metal-organic chemical vapor deposition selective area growth. The nanowire arrays were characterized using cyclic voltammetry and impedance spectroscopy in a non-aqueous electrochemical system using ferrocene/ferrocenium (Fc/Fc+) as a redox couple, and a maximum oxidation photocurrent of 11.1 mA/cm2 was measured. GaAs NW arrays with a 36 nm layer of nickel oxide (NiO x ) synthesized by atomic layer deposition were then used as photoanodes to drive the OER. In addition to acting as an electrocatalyst, the NiO x layer served to protect the GaAs NWs from oxidative corrosion. Using this strategy, GaAs NW photoanodes were successfully used for the oxygen evolution reaction. This is the first demonstration of GaAs NW arrays for effective OER, and the fabrication and protection strategy developed in this work can be extended to study any other nanostructured semiconductor materials systems for electrochemical solar energy conversion.

  2. Single-Crystal Y2O3 Epitaxially on GaAs(001 and (111 Using Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Y. H. Lin

    2015-10-01

    Full Text Available Single-crystal atomic-layer-deposited (ALD Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\ films 2 nm thick were epitaxially grown on molecular beam epitaxy (MBE GaAs(001-4 \\(\\times\\ 6 and GaAs(111A-2 \\(\\times\\ 2 reconstructed surfaces. The in-plane epitaxy between the ALD-oxide films and GaAs was observed using \\textit{in-situ} reflection high-energy electron diffraction in our uniquely designed MBE/ALD multi-chamber system. More detailed studies on the crystallography of the hetero-structures were carried out using high-resolution synchrotron radiation X-ray diffraction. When deposited on GaAs(001, the Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\ films are of a cubic phase and have (110 as the film normal, with the orientation relationship being determined: Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\(\\(110\\[\\(001\\][\\(\\overline{1}10\\]//GaAs(\\(001\\[\\(110\\][\\(1\\overline{1}0\\]. On GaAs(\\(111\\A, the Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\ films are also of a cubic phase with (\\(111\\ as the film normal, having the orientation relationship of Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\(\\(111\\[\\(2\\overline{1}\\overline{1}\\] [\\(01\\overline{1}\\]//GaAs (\\(111\\ [\\(\\overline{2}11\\][\\(0\\overline{1}1\\]. The relevant orientation for the present/future integrated circuit platform is (\\(001\\. The ALD-Y\\(_{\\mathrm{2}}\\O\\(_{\\mathrm{3}}\\/GaAs(\\(001\\-4 \\(\\times\\ 6 has shown excellent electrical properties. These include small frequency dispersion in the capacitance-voltage CV curves at accumulation of ~7% and ~14% for the respective p- and n-type samples with the measured frequencies of 1 MHz to 100 Hz. The interfacial trap density (Dit is low of ~10\\(^{12}\\ cm\\(^{−2}\\eV\\(^{−1}\\ as extracted from measured quasi-static CVs. The frequency dispersion at accumulation and the D\\(_{it}\\ are the lowest ever achieved among all the ALD-oxides on GaAs(\\(001\\.

  3. Dielectric functions, chemical and atomic compositions of the near surface layers of implanted GaAs by In+ ions

    Science.gov (United States)

    Kulik, M.; Kołodyńska, D.; Bayramov, A.; Drozdziel, A.; Olejniczak, A.; Żuk, J.

    2018-06-01

    The surfaces of (100) GaAs were irradiated with In+ ions. The implanted samples were isobaric annealed at 800 °C and then of dielectric function, the surface atomic concentrations of atoms and also the chemical composition of the near surface layers in these implanted semiconductor samples were obtained. The following investigation methods were used: spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry analyses (RBSA) and X-ray photoelectron spectroscopy (XPS) in the study of the above mentioned quantities, respectively. The change of the shape spectra of the dielectric functions at about 3.0 eV phonon energy, diffusion of In+ ions as well as chemical composition changes were observed after ion implantation and the thermal treatment. Due to displacement of Ga ions from GaAs by the In+ ions the new chemical compound InAs was formed. The relative amounts Ga2O3 and As2O3 ratio increase in the native oxide layers with the fluences increase after the thermal treatment of the samples. Additionally, it was noticed that the quantities of InO2 increase with the increasing values of the irradiated ions before thermal treatment.

  4. Photo-irradiation effects on GaAs atomic layer epitaxial growth. GaAs no genshiso epitaxial seicho ni okeru hikari reiki koka

    Energy Technology Data Exchange (ETDEWEB)

    Mashita, M.; Kawakyu, Y.; Sasaki, M.; Ishikawa, H. (Toshiba Corp., Kawasaki (Japan). Research and Development Center)

    1990-08-10

    Single atomic layer epitaxy (ALE) aims at controlling a growing film at a precision of single molecular layer. In this article, it is reported that the growth temperature range of ALE was expanded by the vertical irradiation of KrF exima laser (248 nm) onto the substrate for the ALE growth of GaAs using the metalorganic chemical vapor deposition (MOCVD) method. Thanks for the results of the above experiment, it was demonstrated that the irradiation effect was not thermal, but photochemical. In addition, this article studies the possibility of adsorption layer irradiation and surface irradiation as the photo-irradiation mechanism, and points out that coexistence of both irradiation mechanisms can be considered and, in case of exima laser, strong possibility of direct irradiation of the adsorption layer because of its high power density. Hereinafter, by using both optical growth ALE and thermal growth ALE jointly, the degree of freedom of combination of hetero ALE increases and its application to various material systems becomes possible. 16 refs., 6 figs.

  5. Electrical and physical characteristics for crystalline atomic layer deposited beryllium oxide thin film on Si and GaAs substrates

    International Nuclear Information System (INIS)

    Yum, J.H.; Akyol, T.; Lei, M.; Ferrer, D.A.; Hudnall, Todd W.; Downer, M.; Bielawski, C.W.; Bersuker, G.; Lee, J.C.; Banerjee, S.K.

    2012-01-01

    In a previous study, atomic layer deposited (ALD) BeO exhibited less interface defect density and hysteresis, as well as less frequency dispersion and leakage current density, at the same equivalent oxide thickness than Al 2 O 3 . Furthermore, its self-cleaning effect was better. In this study, the physical and electrical characteristics of ALD BeO grown on Si and GaAs substrates are further evaluated as a gate dielectric layer in III–V metal-oxide-semiconductor devices using transmission electron microscopy, selective area electron diffraction, second harmonic generation, and electrical analysis. An as-grown ALD BeO thin film was revealed as a layered single crystal structure, unlike the well-known ALD dielectrics that exhibit either poly-crystalline or amorphous structures. Low defect density in highly ordered ALD BeO film, less variability in electrical characteristics, and great stability under electrical stress were demonstrated. - Highlights: ► BeO is an excellent electrical insulator, but good thermal conductor. ► Highly crystalline film of BeO has been grown using atomic layer deposition. ► An ALD BeO precursor, which is not commercially available, has been synthesized. ► Physical and electrical characteristics have been investigated.

  6. Structural characterization of ZnTe grown by atomic-layer-deposition regime on GaAs and GaSb (100) oriented substrates

    Energy Technology Data Exchange (ETDEWEB)

    Castillo-Ojeda, Roberto Saúl [Universidad Politécnica de Pachuca (Mexico); Díaz-Reyes, Joel; Peralta-Clara, María de la Cruz; Veloz-Rendón, Julieta Salomé, E-mail: joel_diaz_reyes@hotmail.com [Centro de Investigación en Biotecnología Aplicada, Instituto Politécnico Nacional, Tlaxcala, (Mexico); Galván-Arellano, Miguel [Centro de Investigación y de Estudios Avanzados, Instituto Politécnico Nacional (Mexico); Anda-Salazar, Francisco de [Instituto de Investigación en Comunicación Óptica, Universidad Autónoma de San Luis Potosí (Mexico); Contreras-Rascon, Jorge Indalecio [Departamento de Física, Universidad de Sonora (Mexico)

    2017-10-15

    This work presents the characterization of ZnTe nano layers grown on GaAs and GaSb (100) substrates by the Atomic Layer Deposition (ALD) regime. Under certain conditions, the alternating exposition of a substrate surface to the element vapours makes possible the growth of atomic layers in a reactor where the atmosphere is high-purity hydrogen. ZnTe was grown simultaneously on GaAs and GaSb at the same run, allowing, a comparison between the effects produced by the superficial processes due to the different used substrates, thereby eliminating possible unintended changes of growth parameters. Nano layers on GaSb maintained their shiny appearance even at temperatures near 420°C. It was found that for exposure times below 2.5 s there was not growth on GaAs, while for GaSb the shortest time was 1.5 s at 385°C. By HRXRD the peak corresponding to (004) diffraction plane of ZnTe was identified and investigated, the FWHM resulted very wide (600-800 arcsec) indicating a highly distorted lattice mainly due to mosaicity. Raman scattering shows the peak corresponding to LO-ZnTe, which is weak and slightly shifted in comparison with the reported for the bulk ZnTe at 210 cm{sup -1}. Additionally, the measurements suggest that the crystalline quality have a dependence with the growth temperature. (author)

  7. Influence of a Thiolate Chemical Layer on GaAs (100 Biofunctionalization: An Original Approach Coupling Atomic Force Microscopy and Mass Spectrometry Methods

    Directory of Open Access Journals (Sweden)

    Alex Bienaime

    2013-10-01

    Full Text Available Widely used in microelectronics and optoelectronics; Gallium Arsenide (GaAs is a III-V crystal with several interesting properties for microsystem and biosensor applications. Among these; its piezoelectric properties and the ability to directly biofunctionalize the bare surface, offer an opportunity to combine a highly sensitive transducer with a specific bio-interface; which are the two essential parts of a biosensor. To optimize the biorecognition part; it is necessary to control protein coverage and the binding affinity of the protein layer on the GaAs surface. In this paper; we investigate the potential of a specific chemical interface composed of thiolate molecules with different chain lengths; possessing hydroxyl (MUDO; for 11-mercapto-1-undecanol (HS(CH211OH or carboxyl (MHDA; for mercaptohexadecanoic acid (HS(CH215CO2H end groups; to reconstitute a dense and homogeneous albumin (Rat Serum Albumin; RSA protein layer on the GaAs (100 surface. The protein monolayer formation and the covalent binding existing between RSA proteins and carboxyl end groups were characterized by atomic force microscopy (AFM analysis. Characterization in terms of topography; protein layer thickness and stability lead us to propose the 10% MHDA/MUDO interface as the optimal chemical layer to efficiently graft proteins. This analysis was coupled with in situ MALDI-TOF mass spectrometry measurements; which proved the presence of a dense and uniform grafted protein layer on the 10% MHDA/MUDO interface. We show in this study that a critical number of carboxylic docking sites (10% is required to obtain homogeneous and dense protein coverage on GaAs. Such a protein bio-interface is of fundamental importance to ensure a highly specific and sensitive biosensor.

  8. Electrical properties of GaAs metal–oxide–semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal–organic vapor deposition/atomic layer deposition hybrid system

    Directory of Open Access Journals (Sweden)

    Takeshi Aoki

    2015-08-01

    Full Text Available This paper presents a compressive study on the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD, with an AlN interfacial passivation layer prepared in situ via metal–organic chemical vapor deposition (MOCVD. The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance–voltage (C–V characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm−2 eV−1. Using a (111A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  9. Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping.

    Science.gov (United States)

    Dalapati, Goutam Kumar; Shun Wong, Terence Kin; Li, Yang; Chia, Ching Kean; Das, Anindita; Mahata, Chandreswar; Gao, Han; Chattopadhyay, Sanatan; Kumar, Manippady Krishna; Seng, Hwee Leng; Maiti, Chinmay Kumar; Chi, Dong Zhi

    2012-02-02

    Electrical and physical properties of a metal-oxide-semiconductor [MOS] structure using atomic layer-deposited high-k dielectrics (TiO2/Al2O3) and epitaxial GaAs [epi-GaAs] grown on Ge(100) substrates have been investigated. The epi-GaAs, either undoped or Zn-doped, was grown using metal-organic chemical vapor deposition method at 620°C to 650°C. The diffusion of Ge atoms into epi-GaAs resulted in auto-doping, and therefore, an n-MOS behavior was observed for undoped and Zn-doped epi-GaAs with the doping concentration up to approximately 1017 cm-3. This is attributed to the diffusion of a significant amount of Ge atoms from the Ge substrate as confirmed by the simulation using SILVACO software and also from the secondary ion mass spectrometry analyses. The Zn-doped epi-GaAs with a doping concentration of approximately 1018 cm-3 converts the epi-GaAs layer into p-type since the Zn doping is relatively higher than the out-diffused Ge concentration. The capacitance-voltage characteristics show similar frequency dispersion and leakage current for n-type and p-type epi-GaAs layers with very low hysteresis voltage (approximately 10 mV).PACS: 81.15.Gh.

  10. Atomic hydrogen cleaning of GaAs photocathodes

    International Nuclear Information System (INIS)

    Poelker, M.; Price, J.; Sinclair, C.

    1997-01-01

    It is well known that surface contaminants on semiconductors can be removed when samples are exposed to atomic hydrogen. Atomic H reacts with oxides and carbides on the surface, forming compounds that are liberated and subsequently pumped away. Experiments at Jefferson lab with bulk GaAs in a low-voltage ultra-high vacuum H cleaning chamber have resulted in the production of photocathodes with high photoelectron yield (i.e., quantum efficiency) and long lifetime. A small, portable H cleaning apparatus also has been constructed to successfully clean GaAs samples that are later removed from the vacuum apparatus, transported through air and installed in a high-voltage laser-driven spin-polarized electron source. These results indicate that this method is a versatile and robust alternative to conventional wet chemical etching procedures usually employed to clean bulk GaAs

  11. Structural and electronic properties of isovalent boron atoms in GaAs

    Science.gov (United States)

    Krammel, C. M.; Nattermann, L.; Sterzer, E.; Volz, K.; Koenraad, P. M.

    2018-04-01

    Boron containing GaAs, which is grown by metal organic vapour phase epitaxy, is studied at the atomic level by cross-sectional scanning tunneling microscopy (X-STM) and spectroscopy (STS). In topographic X-STM images, three classes of B related features are identified, which are attributed to individual B atoms on substitutional Ga sites down to the second layer below the natural {110} cleavage planes. The X-STM contrast of B atoms below the surface reflects primarily the structural modification of the GaAs matrix by the small B atoms. However, B atoms in the cleavage plane have in contrast to conventional isovalent impurities, such as Al and In, a strong influence on the local electronic structure similar to donors or acceptors. STS measurements show that B in the GaAs {110} surfaces gives rise to a localized state short below the conduction band (CB) edge while in bulk GaAs, the B impurity state is resonant with the CB. The analysis of BxGa1-xAs/GaAs quantum wells reveals a good crystal quality and shows that the incorporation of B atoms in GaAs can be controlled along the [001] growth direction at the atomic level. Surprisingly, the formation of the first and fourth nearest neighbor B pairs, which are oriented along the directions, is strongly suppressed at a B concentration of 1% while the third nearest neighbor B pairs are found more than twice as often than expected for a completely spatially random pattern.

  12. Economical Atomic Layer Deposition

    Science.gov (United States)

    Wyman, Richard; Davis, Robert; Linford, Matthew

    2010-10-01

    Atomic Layer Deposition is a self limiting deposition process that can produce films at a user specified height. At BYU we have designed a low cost and automated atomic layer deposition system. We have used the system to deposit silicon dioxide at room temperature using silicon tetrachloride and tetramethyl orthosilicate. Basics of atomic layer deposition, the system set up, automation techniques and our system's characterization are discussed.

  13. MBE growth and characterization of GaAs1-x Sb x epitaxial layers on Si (0 0 1) substrates

    International Nuclear Information System (INIS)

    Toda, T.; Nishino, F.; Kato, A.; Kambayashi, T.; Jinbo, Y.; Uchitomi, N.

    2006-01-01

    We investigated the growth of GaAs 1- x Sb x (x=1.0, 0.82, 0.69, 0.44, 0.0) layers on Si (0 0 1) substrates using AlSb as a buffer layer. Epilayers were grown as a function of As beam equivalent pressure (BEP) under a constant Sb BEP, and they were then characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), and micro-Raman scattering analysis. We confirmed that GaAs 1- x Sb x layers have been successfully grown on Si substrates by introducing AlSb layers

  14. Influence of implantation conditions of He+ ions on the structure of a damaged layer in GaAs(001)

    International Nuclear Information System (INIS)

    Shcherbachev, Kirill; Bailey, Melanie J.

    2011-01-01

    An investigation into the influence of implantation conditions (dose, energy, and target temperature) of He + ions on the damage structure of GaAs (100) substrates was performed by HRXRD, scanning electron microscopy, and Nomarski microscopy. Blistering is shown to become apparent as characteristic features of isolines in RSMs. We propose that the formation of the defects yielding a characteristic XRDS is defined by the behavior of implanted atoms in the GaAs matrix, depending on two competing processes: (1) formation of the gas-filled bubbles; (2) diffusion of the He atoms from the bubbles toward the surface and deep into the GaAs substrate. We conclude that the gas-filled bubbles change the structure of the irradiated layer, resulting in the formation of strained crystalline areas of the GaAs matrix. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Interface analysis of Ge ultra thin layers intercalated between GaAs substrates and oxide stacks

    Energy Technology Data Exchange (ETDEWEB)

    Molle, Alessandro, E-mail: alessandro.molle@mdm.infm.i [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (Italy); Lamagna, Luca; Spiga, Sabina [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (Italy); Fanciulli, Marco [Laboratorio Nazionale MDM, CNR-INFM, Via C. Olivetti 2, 20041 Agrate Brianza (MI) (Italy); Dipartimento di Scienza dei Materiali, Universita di Milano Bicocca, Milano (Italy); Brammertz, Guy; Meuris, Marc [IMEC, 75 Kapeldreef, B-3001 Leuven (Belgium)

    2010-01-01

    Capping III-V compound surfaces with Ge ultra-thin layer might be a viable pathway to passivate the electrically active interface traps which usually jeopardize the integration of III-V materials in metal-oxide-semiconductor devices. As the physical nature of such traps is intrinsically related to the chemical details of the interface composition, the structural and compositional features of the Ge/GaAs interface were thoroughly investigated in two different configurations, the atomic layer deposition of La-doped ZrO{sub 2} films on Ge-capped GaAs and the ultra-high vacuum based molecular beam deposition of GeO{sub 2}/Ge double stack on in situ prepared GaAs. In the former case, the intercalation of a Ge interface layer is shown to suppress the concentration of interface Ga-O, As-O and elemental As bonding which were significantly detected in case of the direct oxide deposition on GaAs. In the latter case, the incidence of two different in situ surface preparations, the Ar sputtering and the atomic H cleaning, on the interface composition is elucidated and the beneficial role played by the atomic H exposure in reducing the semiconductor-oxygen bonds at the interface level is demonstrated.

  16. Atomic-scale structure of self-assembled In(Ga)As quantum rings in GaAs

    NARCIS (Netherlands)

    Offermans, P.; Koenraad, P.M.; Wolter, J.H.; Granados, D.; Garcia, J.M.; Fomin, V.; Gladilin, V.N.; Devreese, J.T.

    2005-01-01

    We present an atomic-scale analysis of the indium distribution of self-assembled In(Ga)As quantum rings (QRs) which are formed from InAs quantum dots by capping with a thin layer of GaAs and subsequent annealing. We find that the size and shape of QRs as observed by cross-sectional scanning

  17. Electroless atomic layer deposition

    Science.gov (United States)

    Robinson, David Bruce; Cappillino, Patrick J.; Sheridan, Leah B.; Stickney, John L.; Benson, David M.

    2017-10-31

    A method of electroless atomic layer deposition is described. The method electrolessly generates a layer of sacrificial material on a surface of a first material. The method adds doses of a solution of a second material to the substrate. The method performs a galvanic exchange reaction to oxidize away the layer of the sacrificial material and deposit a layer of the second material on the surface of the first material. The method can be repeated for a plurality of iterations in order to deposit a desired thickness of the second material on the surface of the first material.

  18. Creation of oxygen-enriched layers at the surface of GaAs single crystal

    International Nuclear Information System (INIS)

    Kulik, M.; Maczka, D.; Kobzev, A.P.

    1999-01-01

    The optical properties and the element depth profiles at the (100) plane high resistant and noncomposite GaAs single crystals implanted with In ions were investigated. The results have been compared with those obtained for virgin samples. The optic properties for all of the samples (implanted and not implanted, annealed and not annealed) have been measured using the ellipsometric method. The element depth profiles for the same samples have been obtained by the RBS and NRA techniques. It has been shown that the post-implantation annealing at a temperature more than 600 deg C leads to a ten time increase in contents of oxygen atoms in the implanted layer with respect to the not annealed sample. The thickness of the transparence layer at the surface of GaAs single crystal increases also after implantation with In ions and subsequent annealing

  19. Synthesis of GaAs quantum dots on Si-layers on AlGaAs films grown on GaAs(100) substrates

    International Nuclear Information System (INIS)

    Mendez-Garcia, V. H.; Zamora-Peredo, L.; Saucedo-Zeni, N.

    2002-01-01

    In this work we report a novel method for obtaining GaAs quantum dots by molecular beam epitaxy (MBE) on an AlGaAs underlying film. We propose to use a Si monolayer (ML) grown on AlGaAs, in order to induce a 3D nucleation during the GaAs overgrowth. The samples were prepared in a Riber 32P MBE system employing undoped Si-GaAs(100) substrates. First, a 500 nm thick layer of Al x Ga 1-x As was grown with a nominal concentration x=0.35. Several samples were grown in order to analyze the effects of changing the Si interlayer thickness, and the amount of GaAs overgrowth, on the final structures. Previous to the Si-exposure, the AlGaAs presented a (1x3) surface reconstruction which gradually turned to a (3x1) structure when the Si-thickness was 1 ML, as observed in the reflection high-energy electron diffraction (RHEED) patterns. When the GaAs overgrowth started on this surface, transmission RHEED spots appeared and showed a considerable increase in intensity until reaching a maximum. This behavior is typical from a 3D island growth. If the GaAs overgrowth continues, the initial streaky RHEED patterns recovered indicating a 2D-growth. Thus, we prepared a sample stopping the GaAs overgrowth at the time when the diffraction 3D spot reached the maximum intensity, equivalent to 2ML of GaAs. The sample surface was analyzed in air by atomic force microscopy (AFM). Islands of 1.5 nm-height and 20x20 nm of base were clearly observed, these dimensions are suitable for applications in quantum dots. (Authors)

  20. Growth and characterization of molecular beam epitaxial GaAs layers on porous silicon

    Science.gov (United States)

    Lin, T. L.; Liu, J. K.; Sadwick, L.; Wang, K. L.; Kao, Y. C.

    1987-01-01

    GaAs layers have been grown on porous silicon (PS) substrates with good crystallinity by molecular beam epitaxy. In spite of the surface irregularity of PS substrates, no surface morphology deterioration was observed on epitaxial GaAs overlayers. A 10-percent Rutherford backscattering spectroscopy minimum channeling yield for GaAs-on-PS layers as compared to 16 percent for GaAs-on-Si layers grown under the same condition indicates a possible improvement of crystallinity when GaAs is grown on PS. Transmission electron microscopy reveals that the dominant defects in the GaAs-on-PS layers are microtwins and stacking faults, which originate from the GaAs/PS interface. GaAs is found to penetrate into the PS layers. n-type GaAs/p-type PS heterojunction diodes were fabricated with good rectifying characteristics.

  1. Manipulation and analysis of a single dopant atom in GaAs

    NARCIS (Netherlands)

    Wijnheijmer, A.P.

    2011-01-01

    This thesis focuses on the manipulation and analysis of single dopant atoms in GaAs by scanning tunneling microscopy (STM) and spectroscopy (STS) at low temperatures. The observation of ionization rings is one of the key results, showing that we can control the charge state of a single dopant atom

  2. Atomic structures of a monolayer of AlAs, GaAs, and InAs on Si(111)

    International Nuclear Information System (INIS)

    Lee, Geunjung; Yoon, Younggui

    2010-01-01

    We study atomic structures of a monolayer of AlAs, GaAs, and InAs on a Si(111) substrate from first-principles. The surface with the stacking sequence of ...SiSiMAsSiAs is energetically more stable than the surface with the stacking sequence of ...SiSiSiAsMAs, where M is Al, Ga, or In. The atomic structure of the three top layers of the low-energy surfaces are quite robust, irrespective of M, and the atomic structure of the AlAsSiAs terminated surface and that of the GaAsSiAs terminated surface are very similar. For the high-energy AsMAs terminated surfaces, the broken local tetrahedral symmetry plays an important role in the atomic structures. The calculated atomic structures of InAs on the Si(111) substrate depart most from the structure of crystalline Si.

  3. Microhardness of epitaxial layers of GaAs doped with rare earths

    International Nuclear Information System (INIS)

    Kulish, U.M.; Gamidov, Z.S.; Kuznetsova, I.Yu.; Petkeeva, L.N.; Borlikova, G.V.

    1989-01-01

    Results of the study of microhardness of GaAS layer doped by certain rare earths - Gd, Tb, Dy - are presented. The assumption is made that the higher is the value of the first potential of rare earth impurity ionization (i.e. the higher is the filling of 4f-shell), the lower is the effect of the element on electric and mechanical properties of GaAs epitaxial layers

  4. Dynamic grazing incidence fast atom diffraction during molecular beam epitaxial growth of GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Atkinson, P., E-mail: atkinson@insp.jussieu.fr; Eddrief, M. [Sorbonne Universités, UPMC Univ. Paris 06, UMR 7588, INSP, F-75005 Paris (France); CNRS, UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris (France); Etgens, V. H. [CNRS, UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris (France); VeDeCom-Université Versailles Saint-Quentin en Yvelines, Versailles (France); Khemliche, H., E-mail: hocine.khemliche@u-psud.fr; Debiossac, M.; Mulier, M.; Lalmi, B.; Roncin, P. [ISMO UMR8214 CNRS-Université Paris-Sud, Orsay F-91400 (France); Momeni, A. [ISMO UMR8214 CNRS-Université Paris-Sud, Orsay F-91400 (France); Univ. Cergy Pontoise, F-95031 Cergy (France)

    2014-07-14

    A Grazing Incidence Fast Atom Diffraction (GIFAD) system has been mounted on a commercial molecular beam epitaxy chamber and used to monitor GaAs growth in real-time. In contrast to the conventionally used Reflection High Energy Electron Diffraction, all the GIFAD diffraction orders oscillate in phase, with the change in intensity related to diffuse scattering at step edges. We show that the scattered intensity integrated over the Laue circle is a robust method to monitor the periodic change in surface roughness during layer-by-layer growth, with oscillation phase and amplitude independent of incidence angle and crystal orientation. When there is a change in surface reconstruction at the start of growth, GIFAD intensity oscillations show that there is a corresponding delay in the onset of layer-by-layer growth. In addition, changes in the relative intensity of different diffraction orders have been observed during growth showing that GIFAD has the potential to provide insight into the preferential adatom attachment sites on the surface reconstruction during growth.

  5. Atomic layer deposition for semiconductors

    CERN Document Server

    Hwang, Cheol Seong

    2014-01-01

    This edited volume discusses atomic layer deposition (ALD) for all modern semiconductor devices, moving from the basic chemistry of ALD and modeling of ALD processes to sections on ALD for memories, logic devices, and machines.

  6. Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

    Directory of Open Access Journals (Sweden)

    Takeo Ohno and Yutaka Oyama

    2012-01-01

    Full Text Available In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE, in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm-2. They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor.

  7. GaAs droplet quantum dots with nanometer-thin capping layer for plasmonic applications

    Science.gov (United States)

    In Park, Suk; Trojak, Oliver Joe; Lee, Eunhye; Song, Jin Dong; Kyhm, Jihoon; Han, Ilki; Kim, Jongsu; Yi, Gyu-Chul; Sapienza, Luca

    2018-05-01

    We report on the growth and optical characterization of droplet GaAs quantum dots (QDs) with extremely-thin (11 nm) capping layers. To achieve such result, an internal thermal heating step is introduced during the growth and its role in the morphological properties of the QDs obtained is investigated via scanning electron and atomic force microscopy. Photoluminescence measurements at cryogenic temperatures show optically stable, sharp and bright emission from single QDs, at visible wavelengths. Given the quality of their optical properties and the proximity to the surface, such emitters are good candidates for the investigation of near field effects, like the coupling to plasmonic modes, in order to strongly control the directionality of the emission and/or the spontaneous emission rate, crucial parameters for quantum photonic applications.

  8. Formation, atomic structure, and electronic properties of GaSb quantum dots in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Timm, R.

    2007-12-14

    In this work, cross-sectional scanning tunneling microscopy and spectroscopy are used for the first time to study the shape, size, strain, chemical composition, and electronic properties of capped GaSb/GaAs QDs at the atomic scale. By evaluating such structural results on a variety of nanostructures built using different epitaxy methods and growth conditions, details on the underlying QD formation processes can be revealed. A cross-over from flat quantum wells (QWs) to optically active QDs can be observed in samples grown by metalorganic chemical vapor deposition (MOCVD) with increasing amount of GaSb, including self-assembled Sb accumulations within a still two-dimensional layer and tiny three-dimensional GaSb islands probably acting as precursor structures. The QWs consist of significantly intermixed material with stoichiometries of maximally 50% GaSb, additionally exhibiting small gaps filled with GaAs. A higher GaSb content up to nearly pure material is found in the QDs, being characterized by small sizes of up to 8 nm baselength and about 2 nm height. In spite of the intermixing, all nanostructures have rather abrupt interfaces, and no significant Sb segregation in growth direction is observed. This changes completely when molecular beam epitaxy (MBE) is used as growth method, in which case individual Sb atoms are found to be distributed over several nm above the nanostructures. Massive group-V atomic exchange processes are causing this strong inter-mixing and Sb segregation during GaAs overgrowth. In combination with the large strain inherent to GaSb/GaAs QDs, this segregation upon overgrowth is assumed to be the reason for a unique structural phenomenon: All MBE-grown QDs, independent of the amount of deposited GaSb, exhibit a ring structure, consisting of a ring body of high GaSb content and a more or less extended central gap filled with GaAs. These rings have formed in a self-assembled way even when the initial GaSb layer was overgrown considerably fast

  9. Study on the GaAs(110) surface using emitted atom spectrometry

    International Nuclear Information System (INIS)

    Gayone, J.E.; Sanchez, E.A.; Grizzi, O.; Universidad Nacional de Cuyo, Mendoza

    1998-01-01

    The facilities implemented at Bariloche for the ion scattering spectrometry is described, and recent examples of the technique application to determine the atomic structure and the composition of metallic and semiconductor surfaces, pure and with different adsorbates. The surface analysis technique using emitted atom spectrometry is discussed. The sensitivity to the GaAs(110) surface atomic relaxation is presented, and the kinetic of hydrogen adsorption by the mentioned surface is studied

  10. High Ms Fe16N2 thin film with Ag under layer on GaAs substrate

    Energy Technology Data Exchange (ETDEWEB)

    Allard Jr, Lawrence Frederick [ORNL

    2016-01-01

    (001) textured Fe16N2 thin film with Ag under layer is successfully grown on GaAs substrate using a facing target sputtering (FTS) system. After post annealing, chemically ordered Fe16N2 phase is formed and detected by X-ray diffraction (XRD). High saturation magnetization (Ms) is measured by a vibrating sample magnetometer (VSM). In comparison with Fe16N2 with Ag under layer on MgO substrate and Fe16N2 with Fe under layer on GaAs substrate, the current layer structure shows a higher Ms value, with a magnetically softer feature in contrast to the above cases. In addition, X-ray photoelectron spectroscopy (XPS) is performed to characterize the binding energy of N atoms. To verify the role of strain that the FeN layer experiences in the above three structures, Grazing Incidence X-ray Diffraction (GIXRD) is conducted to reveal a large in-plane lattice constant due to the in-plane biaxial tensile strain. INTRODUCTION

  11. Lattice location of diffused Zn atoms in GaAs and InP single crystals

    International Nuclear Information System (INIS)

    Chan, L.Y.; Yu, K.M.; Ben-Tzur, M.; Haller, E.E.; Jaklevic, J.M.; Walukiewicz, W.; Hanson, C.M.

    1991-01-01

    We have investigated the saturation phenomenon of the free carrier concentration in p-type GaAs and InP single crystals doped by zinc diffusion. The free hole saturation occurs at 10 20 cm -3 for GaAs, but the maximum concentration for InP appears at mid 10 18 cm -3 . The difference in the saturation hole concentrations for these materials is investigated by studying the incorporation and the lattice location of the impurity zinc, an acceptor when located on a group III atom site. Zinc is diffused into the III-V wafers in a sealed quartz ampoule. Particle-induced x-ray emission with ion-channeling techniques are employed to determine the exact lattice location of the zinc atoms. We have found that over 90% of all zinc atoms occupy Ga sites in the diffused GaAs samples, while for the InP case, the zinc substitutionality is dependent on the cooling rate of the sample after high-temperature diffusion. For the slowly cooled sample, a large fraction (∼90%) of the zinc atoms form random precipitates of Zn 3 P 2 and elemental Zn. However, when rapidly cooled only 60% of the zinc forms such precipitates while the rest occupies specific sites in the InP. We analyze our results in terms of the amphoteric native defect model. We show that the difference in the electrical activity of the Zn atoms in GaAs and InP is a consequence of the different location of the Fermi level stabilization energy in these two materials

  12. Optical characterization of MOVPE grown δ-InAs layers in GaAs

    Czech Academy of Sciences Publication Activity Database

    Hazdra, P.; Voves, J.; Hulicius, Eduard; Pangrác, Jiří

    2005-01-01

    Roč. 2, č. 4 (2005), s. 1319-1324 ISSN 1610-1634 R&D Projects: GA AV ČR(CZ) IAA1010318; GA MŠk(CZ) LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : δ-layer * MOVPE * GaAs * photoluminescence * photocurrent * photoreflectance Subject RIV: BM - Solid Matter Physics ; Magnetism

  13. Modeling of altered layer formation during reactive ion etching of GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Mutzke, A. [Max-Planck-Institute of Plasmaphysics, EURATOM Association, D-17491 Greifswald (Germany); Rai, A., E-mail: Abha.Rai@ipp.mpg.de [Max-Planck-Institute of Plasmaphysics, EURATOM Association, D-17491 Greifswald (Germany); Schneider, R.; Angelin, E.J.; Hippler, R. [Institute of Physics, Ernst-Moritz-Arndt-University Greifswald, Felix-Hausdorff-Str.6, D-17489 Greifswald (Germany)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Experimental result showing the preferential sputtering of GaAs (150 keV Ar{sup +} and thermal O on GaAs) during reactive ion beam etching (RIBE) has been reported. Black-Right-Pointing-Pointer A model based on binary collisions (SDTrimSP) is presented to simulate RIBE. Black-Right-Pointing-Pointer The model is used to explain the reported experimental data and also the results by Grigonis and co-workers [1]. - Abstract: The binary collision based SDTrimSP model has been used to simulate the reactive ion beam etching (RIBE) of GaAs in the presence of energetic Ar ions and thermal O atoms. It includes the collisional effects, diffusive processes and chemical reactions taking place in the system. The model parameters are fitted using the experimental observations of Grigonis and co-workers [1] and validated with the experimental results obtained during the GaAs ion etching presented in this paper. A detailed analysis is presented to understand the effect of the diffusive processes and the role of O during RIBE of GaAs. It is shown how the presence of damage caused by the energetic Ar coupled with the presence of thermal O opens up chemical reaction channels which eventually leads to the preferential sputtering of Ga observed at the ion etching facility at University of Greifswald.

  14. Self-assisted GaAs nanowires with selectable number density on Silicon without oxide layer

    International Nuclear Information System (INIS)

    Bietti, S; Somaschini, C; Esposito, L; Sanguinetti, S; Frigeri, C; Fedorov, A; Geelhaar, L

    2014-01-01

    We present the growth of self-assisted GaAs nanowires (NWs) with selectable number density on bare Si(1 1 1), not covered by the silicon oxide. We determine the number density of the NWs by initially self-assembling GaAs islands on whose top a single NW is nucleated. The number density of the initial GaAs base islands can be tuned by droplet epitaxy and the same degree of control is then transferred to the NWs. This procedure is completely performed during a single growth in an ultra-high vacuum environment and requires neither an oxide layer covering the substrate, nor any pre-patterning technique. (paper)

  15. Determination of the thickness of chemically removed thin layers on GaAs VPE structures

    Energy Technology Data Exchange (ETDEWEB)

    Somogyi, K.; Nemeth-Sallay, M.; Nemcsics, A. (Research Inst. for Technical Physics, Hungarian Academy of Sciences, Budapest (Hungary))

    1991-01-01

    Thinning of epitaxial GaAs layers was studied during the surface etching, with a special attention to submicron epitaxial structures, like MESFET or varactor-type structures. Each chemical treatment influences the crystal surface during the device preparation processes, though the possible thinning of the active layer is small. Therefore a method allowing determination of thicknesses as small as at about 20 nm of the layer removed by chemical etching from GaAs VPE structures was applied. Using special multilayered structures and a continuous electrochemical carrier concentration depth profiling, the influence of the layer thickness inhomogeneity and of some measurement errors can be minimized. Some frequently used etchants and the influence of different - so called - non-etching processes were compared in different combinations. It was shown that besides the direct etching a change of the surface conditions occurs, which influences the etch rate in the succeeding etching procedure. (orig.).

  16. Photoacoustic study of the effect of doping concentration on the transport properties of GaAs epitaxial layers

    NARCIS (Netherlands)

    George, S.D.; Dilna, S.; Prasanth, R.; Radhakrishnan, P.; Vallabhan, C.P.G.; Nampoori, V.P.N.

    2003-01-01

    We report a photoacoustic (PA) study of the thermal and transport properties of a GaAs epitaxial layer doped with Si at varying doping concentration, grown on GaAs substrate by molecular beam epitaxy. The data are analyzed on the basis of Rosencwaig and Gersho's theory of the PA effect. The

  17. Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

    International Nuclear Information System (INIS)

    Krantz, Claude

    2009-01-01

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

  18. Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, Claude

    2009-10-28

    We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at usable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully. (orig.)

  19. STM studies of an atomic-scale gate electrode formed by a single charged vacancy in GaAs

    Science.gov (United States)

    Lee, Donghun; Daughton, David; Gupta, Jay

    2009-03-01

    Electric-field control of spin-spin interactions at the atomic level is desirable for the realization of spintronics and spin-based quantum computation. Here we demonstrate the realization of an atomic-scale gate electrode formed by a single charged vacancy on the GaAs(110) surface[1]. We can position these vacancies with atomic precision using the tip of a home-built, low temperature STM. Tunneling spectroscopy of single Mn acceptors is used to quantify the electrostatic field as a function of distance from the vacancy. Single Mn acceptors are formed by substituting Mn adatoms for Ga atoms in the first layer of the p-GaAs(110) surface[2]. Depending on the distance, the in-gap resonance of single Mn acceptors can shift as much as 200meV. Our data indicate that the electrostatic field decays according to a screened Coulomb potential. The charge state of the vacancy can be switched to neutral, as evidenced by the Mn resonance returning to its unperturbed position. Reversible control of the local electric field as well as charged states of defects in semiconductors can open new insights such as realizing an atomic-scale gate control and studying spin-spin interactions in semiconductors. http://www.physics.ohio-state.edu/sim jgupta [1] D. Lee and J.A. Gupta (in preparation) [2] D. Kitchen et al., Nature 442, 436-439 (2006)

  20. Atomic-scale structure of irradiated GaN compared to amorphised GaP and GaAs

    International Nuclear Information System (INIS)

    Ridgway, M.C.; Everett, S.E.; Glover, C.J.; Kluth, S.M.; Kluth, P.; Johannessen, B.; Hussain, Z.S.; Llewellyn, D.J.; Foran, G.J.; Azevedo, G. de M.

    2006-01-01

    We have compared the atomic-scale structure of ion irradiated GaN to that of amorphised GaP and GaAs. While continuous and homogenous amorphised layers were easily achieved in GaP and GaAs, ion irradiation of GaN yielded both structural and chemical inhomogeneities. Transmission electron microscopy revealed GaN crystallites and N 2 bubbles were interspersed within an amorphous GaN matrix. The crystallite orientation was random relative to the unirradiated epitaxial structure, suggesting their formation was irradiation-induced, while the crystallite fraction was approximately constant for all ion fluences beyond the amorphisation threshold, consistent with a balance between amorphisation and recrystallisation processes. Extended X-ray absorption fine structure measurements at the Ga K-edge showed short-range order was retained in the amorphous phase for all three binary compounds. For ion irradiated GaN, the stoichiometric imbalance due to N 2 bubble formation was not accommodated by Ga-Ga bonding in the amorphous phase or precipitation of metallic Ga but instead by a greater reduction in Ga coordination number

  1. Laser-excited photoluminescence of three-layer GaAs double-heterostructure laser material

    International Nuclear Information System (INIS)

    Nash, F.R.; Dixon, R.W.; Barnes, P.A.; Schumaker, N.E.

    1975-01-01

    The successful fabrication of high-quality DH GaAs lasers from a simplified three-layer structure is reported. A major asset of this structure is the transparency of its final layer to recombination radiation occurring in the active layer, thus permitting the use of nondestructive photoluminescent techniques for material evaluation prior to device fabrication. In the course of photoluminescence investigations on this material the additional important observation has been made that indirect excitation (in which photocarriers are generated in the top ternary layer) has significant advantages over direct excitation (in which photocarriers are generated directly in the active layer). These include (i) the direct measurement of Al concentrations in both upper layers, (ii) the measurements of the minority-carrier diffusion length in the upper layer, (iii) an easily obtained indication of taper in the thickness of the upper layer, and (iv) surprisingly effective excitation of the active layer. By combining direct and indirect excitation it is shown that a clearer understanding of the location and detrimental influences of defects in the GaAs laser structure may be obtained. For example, the width of the region of reduced luminescence associated with many defects is found to be very excitation dependent and is confirmed to arise fr []m reduced active region luminescence. The photoluminescent excitation techniques described should be useful in the study of other heterostructure devices and material systems

  2. Photoenhanced atomic layer epitaxy. Hikari reiki genshiso epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Mashita, M.; Kawakyu, Y. (Toshiba corp., Tokyo (Japan))

    1991-10-01

    The growth temperature range was greatly expanded of atomic layer epitaxy (ALE) expected as the growth process of ultra-thin stacks. Ga layers and As layers were formed one after the other on a GaAs substrate in the atmosphere of trimethylgallium (TMG) or AsH{sub 2} supplied alternately, by KrF excimer laser irradiation normal to the substrate. As a result, the growth temperature range was 460-540{degree}C nearly 10 times that of 500 {plus minus} several degrees centigrade in conventional thermal growth method. Based on the experimental result where light absorption of source molecules adsorbed on a substrate surface was larger than that under gaseous phase condition, new adsorbed layer enhancement model was proposed to explain above irradiation effect verifying it by experiments. As this photoenhancement technique is applied to other materials, possible fabrication of new crystal structures as a super lattice with ultra-thin stacks of single atomic layers is expected because of a larger freedom in material combination for hetero-ALE. 11 refs., 7 figs.

  3. Attractive interaction between Mn atoms on the GaAs(110) surface observed by scanning tunneling microscopy.

    Science.gov (United States)

    Taninaka, Atsushi; Yoshida, Shoji; Kanazawa, Ken; Hayaki, Eiko; Takeuchi, Osamu; Shigekawa, Hidemi

    2016-06-16

    Scanning tunneling microscopy/spectroscopy (STM/STS) was carried out to investigate the structures of Mn atoms deposited on a GaAs(110) surface at room temperature to directly observe the characteristics of interactions between Mn atoms in GaAs. Mn atoms were paired with a probability higher than the random distribution, indicating an attractive interaction between them. In fact, re-pairing of unpaired Mn atoms was observed during STS measurement. The pair initially had a new structure, which was transformed during STS measurement into one of those formed by atom manipulation at 4 K. Mn atoms in pairs and trimers were aligned in the direction, which is theoretically predicted to produce a high Curie temperature.

  4. Characterization of InSb layers on GaAs substrates using infrared reflectance and a modified oscillator formula

    Energy Technology Data Exchange (ETDEWEB)

    Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Wagener, M.C. [Physics Department, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa)

    2009-12-01

    InSb epilayers on GaAs substrates are analyzed using infrared reflectance spectroscopy, but employing a modified Drude oscillator formula. The modified formula enables the determination of 13 parameters: six dielectric parameters for both layer and substrate separately, as well as the thickness of the layer. The formula is tested against previously published data, and to characterize layers grown in this laboratory.

  5. Characterization of InSb layers on GaAs substrates using infrared reflectance and a modified oscillator formula

    International Nuclear Information System (INIS)

    Engelbrecht, J.A.A.; Wagener, M.C.

    2009-01-01

    InSb epilayers on GaAs substrates are analyzed using infrared reflectance spectroscopy, but employing a modified Drude oscillator formula. The modified formula enables the determination of 13 parameters: six dielectric parameters for both layer and substrate separately, as well as the thickness of the layer. The formula is tested against previously published data, and to characterize layers grown in this laboratory.

  6. Superconducting NbN single-photon detectors on GaAs with an AlN buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Ekkehart; Merker, Michael; Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut fuer Technologie, Hertzstrasse 16, 76187 Karlsruhe (Germany)

    2015-07-01

    GaAs is the material of choice for photonic integrated circuits. It allows the monolithic integration of single-photon sources like quantum dots, waveguide based optical circuits and detectors like superconducting nanowire single-photon detectors (SNSPDs) onto one chip. The growth of high quality NbN films on GaAs is challenging, due to natural occurring surface oxides and the large lattice mismatch of about 27%. In this work, we try to overcome these problems by the introduction of a 10 nm AlN buffer layer. Due to the buffer layer, the critical temperature of 6 nm thick NbN films was increased by about 1.5 K. Furthermore, the critical current density at 4.2 K of NbN flim deposited onto GaAs with AlN buffer is 50% higher than of NbN film deposited directly onto GaAs substrate. We successfully fabricated NbN SNSPDs on GaAs with a AlN buffer layer. SNSPDs were patterned using electron-beam lithography and reactive-ion etching techniques. Results on the study of detection efficiency and jitter of a NbN SNSPD on GaAs, with and without AlN buffer layer will be presented and discussed.

  7. Direct Growth of High-Quality InP Layers on GaAs Substrates by MOCVD

    Directory of Open Access Journals (Sweden)

    K. F. Yarn

    2003-01-01

    group V partial pressure, growth rate and V/III ratios. A mirror-like, uniform surface and high crystal quality of the metamorphic buffer layer directly grown on a GaAs substrate can be achieved. Finally, to investigate the performance of the metamorphic microwave devices, we also fabricate the InAlAs/InGaAs metamorphic HEMT on GaAs substrates.

  8. Growth of High-Quality GaAs on Ge by Controlling the Thickness and Growth Temperature of Buffer Layer

    Science.gov (United States)

    Zhou, Xu-Liang; Pan, Jiao-Qing; Yu, Hong-Yan; Li, Shi-Yan; Wang, Bao-Jun; Bian, Jing; Wang, Wei

    2014-12-01

    High-quality GaAs thin films grown on miscut Ge substrates are crucial for GaAs-based devices on silicon. We investigate the effect of different thicknesses and temperatures of GaAs buffer layers on the crystal quality and surface morphology of GaAs on Ge by metal-organic chemical vapor deposition. Through high resolution x-ray diffraction measurements, it is demonstrated that the full width at half maximum for the GaAs epilayer (Ge substrate) peak could achieve 19.3 (11.0) arcsec. The value of etch pit density could be 4×104 cm-2. At the same time, GaAs surfaces with no pyramid-shaped pits are obtained when the buffer layer growth temperature is lower than 360°C, due to effective inhibition of initial nucleation at terraces of the Ge surface. In addition, it is shown that large island formation at the initial stage of epitaxial growth is a significant factor for the final rough surface and that this initial stage should be carefully controlled when a device quality GaAs surface is desired.

  9. Epitaxial ferromagnetic Fe3Si on GaAs(111)A with atomically smooth surface and interface

    International Nuclear Information System (INIS)

    Liu, Y. C.; Hung, H. Y.; Kwo, J.; Chen, Y. W.; Lin, Y. H.; Cheng, C. K.; Hong, M.; Tseng, S. C.; Hsu, C. H.; Chang, M. T.; Lo, S. C.

    2015-01-01

    Single crystal ferromagnetic Fe 3 Si(111) films were grown epitaxially on GaAs(111)A by molecular beam epitaxy. These hetero-structures possess extremely low surface roughness of 1.3 Å and interfacial roughness of 1.9 Å, measured by in-situ scanning tunneling microscope and X-ray reflectivity analyses, respectively, showing superior film quality, comparing to those attained on GaAs(001) in previous publications. The atomically smooth interface was revealed by the atomic-resolution Z (atomic number)-contrast scanning transmission electron microscopy (STEM) images using the correction of spherical aberration (Cs)-corrected electron probe. Excellent crystallinity and perfect lattice match were both confirmed by high resolution x-ray diffraction. Measurements of magnetic property for the Fe 3 Si/GaAs(111) yielded a saturation moment of 990 emu/cm 3 with a small coercive field ≤1 Oe at room temperature

  10. Atomic layer deposition for graphene device integration

    NARCIS (Netherlands)

    Vervuurt, R.H.J.; Kessels, W.M.M.; Bol, A.A.

    2017-01-01

    Graphene is a two dimensional material with extraordinary properties, which make it an interesting material for many optical and electronic devices. The integration of graphene in these devices often requires the deposition of thin dielectric layers on top of graphene. Atomic layer deposition (ALD)

  11. Crystal structure of LT GaAs layers before and after annealing

    International Nuclear Information System (INIS)

    Litiental-Weber, Z.

    1992-01-01

    In this paper the structural quality of GaAs layers grown at low temperatures by solid-source and gas-source MBE at different growth conditions is described. Dependence on the growth temperature and concentration of As [expressed at As/Ga beam equivalent pressure (BEP)] used for the growth is discussed. A higher growth temperature is required top obtain the same monocrystalling layer thickness with increased BEP. The annealing of these layers is associated with the formation of As precipitates. Semicoherent precipitates with lowest formation energies are formed in the monocrystalline parts of the layers grown with the lowest BEP. Precipitates with higher formation energies are formed when higher BEP is applied; they are also formed in the vicinity of structural defects. Formation of As precipitates releases strain in the layers. Arsenic precipitates are not formed in annealed ternary (InAlAs) layers despite their semi-insulating properties. The role of As precipitates in semi-insulating properties and the short lifetime of minority carriers in these layers is discussed

  12. Shear deformation and relaxed lattice constant of (Ga,Mn)As layers on GaAs(113)A

    Energy Technology Data Exchange (ETDEWEB)

    Dreher, Lukas; Daeubler, Joachim; Glunk, Michael; Schoch, Wladimir; Limmer, Wolfgang; Sauer, Rolf [Institut fuer Halbleiterphysik, Universitaet Ulm, D-89069 Ulm (Germany)

    2008-07-01

    The shear deformation and the relaxed lattice constant of compressively strained (Ga,Mn)As layers with Mn concentrations of up to 5%, pseudomorphically grown on GaAs(113)A and GaAs(001) substrates by low-temperature molecular-beam epitaxy, have been studied by high resolution X-ray diffraction (HRXRD) measurements. Rocking curves reveal a triclinic distortion of the (113)A layers with a shear direction towards the [001] crystallographic axis, whereas the (001) layers are tetragonally distorted along [001]. The relaxed lattice constants were derived from {omega}-2{theta} scans for the symmetric (113) and (004) Bragg reflections, taking the elastic anisotropy of the cubic system into account. The increase of the lattice constant with Mn content has been found to be smaller for the (113)A layers than for the (001) layers, presumably due to the enhanced amount of excess As in the (113)A layers.

  13. Molecular beam epitaxial growth and characterization of GaSb layers on GaAs (0 0 1) substrates

    International Nuclear Information System (INIS)

    Li Yanbo; Zhang Yang; Zhang Yuwei; Wang Baoqiang; Zhu Zhanping; Zeng Yiping

    2012-01-01

    We report on the growth of GaSb layers on GaAs (0 0 1) substrates by molecular beam epitaxy (MBE). We investigate the influence of the GaAs substrate surface treatment, growth temperature, and V/III flux ratios on the crystal quality and the surface morphology of GaSb epilayers. Comparing to Ga-rich GaAs surface preparation, the Sb-rich GaAs surface preparation can promote the growth of higher-quality GaSb material. It is found that the crystal quality, electrical properties, and surface morphology of the GaSb epilayers are highly dependent on the growth temperature, and Sb/Ga flux ratios. Under the optimized growth conditions, we demonstrate the epitaxial growth of high quality GaSb layers on GaAs substrates. The p-type nature of the unintentionally doped GaSb is studied and from the growth conditions dependence of the hole concentrations of the GaSb, we deduce that the main native acceptor in the GaSb is the Ga antisite (Ga Sb ) defect.

  14. Diffusion of Ni, Ga, and As in the surface layer of GaAs and characteristics of the Ni/GaAs contact

    International Nuclear Information System (INIS)

    Uskov, V.A.; Fedotov, A.B.; Erofeeva, E.A.; Rodionov, A.I.; Dzhumakulov, D.T.

    1987-01-01

    The authors investigate the low-temperature codiffusion of Ni, Ga, and As in the surface layer of gallium arsenide and study its effect on the current-voltage characteristics of a Ni/GaAs rectifier contact. The concentration distribution of atoms in the function layer of a Ni-GaAs system was investigated by the methods of layerwise radiometric and neutron-activation analyses. It was found that interdiffusion of components takes place in the Ni-GaAs system in an elastic stress field, generated by the differences in the lattice parameters and thermal-expansion coefficients of Ni, GaAs, and the intermetallic compound which form. The form and parameters of the current-voltage characteristics of a Ni/GaAs contact are determined by the phase composition and the structure of the junction layer

  15. High Quality GaAs Epilayers Grown on Si Substrate Using 100 nm Ge Buffer Layer

    Directory of Open Access Journals (Sweden)

    Wei-Cheng Kuo

    2016-01-01

    Full Text Available We present high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers. The thin Ge buffer layers were modulated by hydrogen flow rate from 60 to 90 sccm to improve crystal quality by electron cyclotron resonance chemical vapor deposition (ECR-CVD at low growth temperature (180°C. The GaAs and Ge epilayers quality was verified by X-ray diffraction (XRD and spectroscopy ellipsometry (SE. The full width at half maximum (FWHM of the Ge and GaAs epilayers in XRD is 406 arcsec and 220 arcsec, respectively. In addition, the GaAs/Ge/Si interface is observed by transmission electron microscopy (TEM to demonstrate the epitaxial growth. The defects at GaAs/Ge interface are localized within a few nanometers. It is clearly showed that the dislocation is well suppressed. The quality of the Ge buffer layer is the key of III–V/Si tandem cell. Therefore, the high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers is suitable to develop the low cost and high efficiency III–V/Si tandem solar cells.

  16. Atomic layer deposition of nanostructured materials

    CERN Document Server

    Pinna, Nicola

    2012-01-01

    Atomic layer deposition, formerly called atomic layer epitaxy, was developed in the 1970s to meet the needs of producing high-quality, large-area fl at displays with perfect structure and process controllability. Nowadays, creating nanomaterials and producing nanostructures with structural perfection is an important goal for many applications in nanotechnology. As ALD is one of the important techniques which offers good control over the surface structures created, it is more and more in the focus of scientists. The book is structured in such a way to fi t both the need of the expert reader (du

  17. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.; Hoogland, Sjoerd; Adachi, Michael M.; Kanjanaboos, Pongsakorn; Wong, Chris T. O.; McDowell, Jeffrey J.; Xu, Jixian; Voznyy, Oleksandr; Ning, Zhijun; Houtepen, Arjan J.; Sargent, Edward H.

    2014-01-01

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  18. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.

    2014-10-30

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  19. Infrared reflection spectra of multilayer epitaxial heterostructures with embedded InAs and GaAs layers

    International Nuclear Information System (INIS)

    Seredin, P. V.; Domashevskaya, E. P.; Lukin, A. N.; Arsent'ev, I. N.; Vinokurov, D. A.; Tarasov, I. S.

    2008-01-01

    The effect of the thickness of embedded InAs and GaAs layers on the infrared reflection spectra of lattice vibrations for AlInAs/InAs/AlInAs, InGaAs/GaAs/InGaAs, and AlInAs/InGaAs/GaAs/InGaAs/AlInAs multilayer epitaxial heterostructures grown by MOC hydride epitaxy on InP (100) substrates is studied. Relative stresses emerging in the layers surrounding the embedded layers with variation in the number of monolayers from which the quantum dots are formed and with variation the thickness of the layers themselves surrounding the embedded layers are evaluated.

  20. Nano-soldering to single atomic layer

    Science.gov (United States)

    Girit, Caglar O [Berkeley, CA; Zettl, Alexander K [Kensington, CA

    2011-10-11

    A simple technique to solder submicron sized, ohmic contacts to nanostructures has been disclosed. The technique has several advantages over standard electron beam lithography methods, which are complex, costly, and can contaminate samples. To demonstrate the soldering technique graphene, a single atomic layer of carbon, has been contacted, and low- and high-field electronic transport properties have been measured.

  1. Conductive atomic force microscopy study of InAs growth kinetics on vicinal GaAs (110)

    International Nuclear Information System (INIS)

    Tejedor, Paloma; Diez-Merino, Laura; Beinik, Igor; Teichert, Christian

    2009-01-01

    Conductive atomic force microscopy has been used to investigate the effect of atomic hydrogen and step orientation on the growth behavior of InAs on GaAs (110) misoriented substrates. Samples grown by conventional molecular beam epitaxy exhibit higher conductivity on [110]-multiatomic step edges, where preferential nucleation of InAs nanowires takes place by step decoration. On H-terminated substrates with triangular terraces bounded by [115]-type steps, three-dimensional InAs clusters grow selectively at the terrace apices as a result of a kinetically driven enhancement in upward mass transport via AsH x intermediate species and a reduction in the surface free energy.

  2. Study of the process of positron annihilation in GaAs disturbed surface layers

    International Nuclear Information System (INIS)

    Vorob'ev, A.A.; Aref'ev, K.P.; Vorob'ev, S.A.; Karetnikov, A.S.; Prokop'ev, E.P.; Kuznetsov, Yu.N.; Khashimov, F.R.; Markova, T.I.

    1977-01-01

    The effect was investigated of single-crystal semiconductor surface treatment types on positron annihilation characteristics. CaAs single-crystal specimens were investigated with the following surface treatment types: (a) polishing with Al 2 O 3 abrasive powder water suspension; (b) mechanical polishing with diamond paste; (c) mechanical chemical polishing with Al 2 O 3 or ZrO 2 suspensions; (d) chemical polishing with the 1HF:3HNO 3 :2H 2 O mixture. The investigation of annihilation was performed by the method of distinguishing the narrow component Isub(N) from correlation curves in 14.5 kOc statical magnetic field and by that of measuring the relative value of friquantuum annihilation Psub(3γ). The maximum Isub(N) and Psub(3γ) values are shown to occur in GaAs specimens with the (d) type of treatment. The experimental data provided a conclusion about the presence of a maximum thickness oxide layer of complex composition on the surface of the specimens compared with oxide layer thicknesses on the surface of specimens with (a), (b), and (c) treatmens. It is concluded that the positron annihilation method may be successfully used for the study of semiconductor material oxide layers

  3. Defect characterization in compositionally graded InGaAs layers on GaAs(001) grown by MBE

    International Nuclear Information System (INIS)

    Sasaki, Takuo; Takahasi, Masamitu; Norman, Andrew G.; Romero, Manuel J.; Al-Jassim, Mowafak M.; Kojima, Nobuaki; Ohshita, Yoshio; Yamaguchi, Masafumi

    2013-01-01

    Defect characterization in molecular beam epitaxial (MBE) compositionally-graded In x Ga 1-x As layers on GaAs substrates consisting different thickness of overshooting (OS) layers was carried out using cathodoluminescence (CL) and transmission electron microscopy (TEM). We found that the thickness of the OS layer influences not only stress but also lattice defects generated in a top InGaAs layer. While the top InGaAs layer with a thin OS layer is under compression and has mainly threading dislocations, the top layer with a thick OS layer is under tension and exhibits inhomogeneous strain associating with phase separation. We will discuss the mechanisms of defect generation and their in-plane distribution based on strain relaxation at the top and OS layers. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Veer Dhaka

    2016-01-01

    Full Text Available Low temperature (∼200 °C grown atomic layer deposition (ALD films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP nanowires (NWs, and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL at low temperatures (15K, and the best passivation was achieved with a few monolayer thick (2Å film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  5. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dhaka, Veer, E-mail: veer.dhaka@aalto.fi; Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri [Department of Micro- and Nanosciences, Micronova, Aalto University, P.O. Box 13500, FI-00076 (Finland); Naureen, Shagufta; Shahid, Naeem [Research School of Physics & Engineering, Department of Electronic Materials Engineering, Australian National University, Canberra ACT 2601 (Australia); Jiang, Hua; Kauppinen, Esko [Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI-00076 (Finland); Srinivasan, Anand [School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, S-164 40 Kista (Sweden)

    2016-01-15

    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al{sub 2}O{sub 3}, GaN, and TiO{sub 2} were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al{sub 2}O{sub 3}. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al{sub 2}O{sub 3} layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al{sub 2}O{sub 3} provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  6. Atomic scale characterization of mismatched graphene layers

    International Nuclear Information System (INIS)

    Luican-Mayer, Adina; Li, Guohong; Andrei, Eva Y.

    2017-01-01

    Highlights: • Review of STM/STS of graphene with various degree of coupling. • Review of vertically twisted graphene with respect with each other. • Review of Landau levels in graphene layers weakly decoupled electronically. • Review of laterally twisted graphene forming grain boundaries. - Abstract: In the bourgeoning field of two dimensional layered materials and their atomically thin counterparts, it has been established that the electronic coupling between the layers of the material plays a key role in determining its properties [1,2]. We are just beginning to understand how each material is unique in that respect while working our way up to building new materials with functionalities enabled by interlayer interactions. In this review, we will focus on a system that despite its apparent simplicity possesses a wealth of intriguing physics: layers of graphene with various degree of coupling. The situations discussed here are graphene layers vertically twisted with respect with each other, weakly decoupled electronically and laterally twisted forming grain boundaries. We emphasize experiments that atomically resolve the electronic properties.

  7. Observation of linear I-V curves on vertical GaAs nanowires with atomic force microscope

    Science.gov (United States)

    Geydt, P.; Alekseev, P. A.; Dunaevskiy, M.; Lähderanta, E.; Haggrén, T.; Kakko, J.-P.; Lipsanen, H.

    2015-12-01

    In this work we demonstrate the possibility of studying the current-voltage characteristics for single vertically standing semiconductor nanowires on standard AFM equipped by current measuring module in PeakForce Tapping mode. On the basis of research of eight different samples of p-doped GaAs nanowires grown on different GaAs substrates, peculiar electrical effects were revealed. It was found how covering of substrate surface by SiOx layer increases the current, as well as phosphorous passivation of the grown nanowires. Elimination of the Schottky barrier between golden cap and the top parts of nanowires was observed. It was additionally studied that charge accumulation on the shell of single nanowires affects its resistivity and causes the hysteresis loops on I-V curves.

  8. Epitaxial growth of ZnO layers on (111) GaAs substrates by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ding Jian; Zhang Di; Konomi, Takaharu; Saito, Katsuhiko; Guo Qixin

    2012-01-01

    ZnO layers were grown on (111) GaAs substrates by laser molecular epitaxy at substrate temperatures between 200 and 550 °C. X-ray diffraction analysis revealed that c-axis of ZnO epilayer with a wurtzite structure is perpendicular to the substrate surface. X-ray rocking curves and Raman spectroscopy showed that the crystal quality of ZnO epilayers depends on the substrate temperature during the growth. Strong near-band-edge emission in the UV region without any deep-level emissions was observed from the ZnO epilayers at room temperature. The results indicate that laser molecular beam epitaxy is a promising growth method for obtaining high-quality ZnO layers on (111) GaAs substrates.

  9. Growth of thermal oxide layers on GaAs and InP in the presence of ammonium heptamolybdate

    International Nuclear Information System (INIS)

    Mittova, I.Ya.; Lavrushina, S.S.; Afonchikova, A.V.

    2004-01-01

    Processes of thermal oxidation of GaAs and InP in the presence of ammonium heptamolybdate were studied using the methods of X-ray fluorescence analysis and IR spectroscopy at temperatures 480-580 Deg C. It was ascertained that introduction of the activator into the system results in accelerated growth of layers on semiconductors due to participation of anionic component of the chemostimulator in oxidation processes. The activator is integrated into the salts formed [ru

  10. Epitaxial ferromagnetic Fe{sub 3}Si on GaAs(111)A with atomically smooth surface and interface

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y. C.; Hung, H. Y.; Kwo, J., E-mail: chsu@nsrrc.org.tw, E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Y. W.; Lin, Y. H.; Cheng, C. K.; Hong, M., E-mail: chsu@nsrrc.org.tw, E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Tseng, S. C.; Hsu, C. H., E-mail: chsu@nsrrc.org.tw, E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Chang, M. T.; Lo, S. C. [Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China)

    2015-09-21

    Single crystal ferromagnetic Fe{sub 3}Si(111) films were grown epitaxially on GaAs(111)A by molecular beam epitaxy. These hetero-structures possess extremely low surface roughness of 1.3 Å and interfacial roughness of 1.9 Å, measured by in-situ scanning tunneling microscope and X-ray reflectivity analyses, respectively, showing superior film quality, comparing to those attained on GaAs(001) in previous publications. The atomically smooth interface was revealed by the atomic-resolution Z (atomic number)-contrast scanning transmission electron microscopy (STEM) images using the correction of spherical aberration (Cs)-corrected electron probe. Excellent crystallinity and perfect lattice match were both confirmed by high resolution x-ray diffraction. Measurements of magnetic property for the Fe{sub 3}Si/GaAs(111) yielded a saturation moment of 990 emu/cm{sup 3} with a small coercive field ≤1 Oe at room temperature.

  11. Photoabsorption modulation in GaAs: Ga1-xInx as strained-layer superlattices

    International Nuclear Information System (INIS)

    Sella, I.; Watkins, D.E.; Laurich, B.K.; Smith, D.L.; Subbanna, S.; Kroemer, H.

    1990-01-01

    Photoabsorption modulation measurements have been made on Ga 1 -x In x As -- GaAs strained-layer superlattices using two approaches: In the first the modulating beam and the test beam have the same wavelength (near the exciton resonance). In the second, the modulation wavelength is much shorter than the test beam wavelength. A dramatic difference is observed in the modulated transmission spectra near the excitonic level for the two modulating wavelengths. The difference in behavior can be explained by screening of the residual surface electric field, which only occurs for the high photon energy modulating beam. This beam excites carriers that are free to drift in the surface field before they are captured in the quantum wells. Carriers excited by the low photon energy modulation beam are created in the wells and can not effectively screen the surface field. We describe a model which explains the nonlinear intensity saturation profile and qualitatively describes the spectral line shape. 4 refs., 4 figs

  12. Atomic-scale epitaxial aluminum film on GaAs substrate

    Directory of Open Access Journals (Sweden)

    Yen-Ting Fan

    2017-07-01

    Full Text Available Atomic-scale metal films exhibit intriguing size-dependent film stability, electrical conductivity, superconductivity, and chemical reactivity. With advancing methods for preparing ultra-thin and atomically smooth metal films, clear evidences of the quantum size effect have been experimentally collected in the past two decades. However, with the problems of small-area fabrication, film oxidation in air, and highly-sensitive interfaces between the metal, substrate, and capping layer, the uses of the quantized metallic films for further ex-situ investigations and applications have been seriously limited. To this end, we develop a large-area fabrication method for continuous atomic-scale aluminum film. The self-limited oxidation of aluminum protects and quantizes the metallic film and enables ex-situ characterizations and device processing in air. Structure analysis and electrical measurements on the prepared films imply the quantum size effect in the atomic-scale aluminum film. Our work opens the way for further physics studies and device applications using the quantized electronic states in metals.

  13. Predicting synergy in atomic layer etching

    Energy Technology Data Exchange (ETDEWEB)

    Kanarik, Keren J. [Lam Research Corp., Fremont, CA (United States); Tan, Samantha [Lam Research Corp., Fremont, CA (United States); Yang, Wenbing [Lam Research Corp., Fremont, CA (United States); Kim, Taeseung [Lam Research Corp., Fremont, CA (United States); Lill, Thorsten [Lam Research Corp., Fremont, CA (United States); Kabansky, Alexander [Lam Research Corp., Fremont, CA (United States); Hudson, Eric A. [Lam Research Corp., Fremont, CA (United States); Ohba, Tomihito [Lam Research Corp., Fremont, CA (United States); Nojiri, Kazuo [Lam Research Corp., Fremont, CA (United States); Yu, Jengyi [Lam Research Corp., Fremont, CA (United States); Wise, Rich [Lam Research Corp., Fremont, CA (United States); Berry, Ivan L. [Lam Research Corp., Fremont, CA (United States); Pan, Yang [Lam Research Corp., Fremont, CA (United States); Marks, Jeffrey [Lam Research Corp., Fremont, CA (United States); Gottscho, Richard A. [Lam Research Corp., Fremont, CA (United States)

    2017-03-27

    Atomic layer etching (ALE) is a multistep process used today in manufacturing for removing ultrathin layers of material. In this article, the authors report on ALE of Si, Ge, C, W, GaN, and SiO2 using a directional (anisotropic) plasma-enhanced approach. The authors analyze these systems by defining an “ALE synergy” parameter which quantifies the degree to which a process approaches the ideal ALE regime. This parameter is inspired by the ion-neutral synergy concept introduced in the 1979 paper by Coburn and Winters. ALE synergy is related to the energetics of underlying surface interactions and is understood in terms of energy criteria for the energy barriers involved in the reactions. Synergistic behavior is observed for all of the systems studied, with each exhibiting behavior unique to the reactant–material combination. By systematically studying atomic layer etching of a group of materials, the authors show that ALE synergy scales with the surface binding energy of the bulk material. This insight explains why some materials are more or less amenable to the directional ALE approach. Furthermore, they conclude that ALE is both simpler to understand than conventional plasma etch processing and is applicable to metals, semiconductors, and dielectrics.

  14. Atomic-scale luminescence measurement and theoretical analysis unveiling electron energy dissipation at a p-type GaAs(110) surface

    International Nuclear Information System (INIS)

    Imada, Hiroshi; Miwa, Kuniyuki; Jung, Jaehoon; Shimizu, Tomoko K; Kim, Yousoo; Yamamoto, Naoki

    2015-01-01

    Luminescence of p-type GaAs was induced by electron injection from the tip of a scanning tunnelling microscope into a GaAs(110) surface. Atomically-resolved photon maps revealed a significant reduction in luminescence intensity at surface electronic states localized near Ga atoms. Theoretical analysis based on first principles calculations and a rate equation approach was performed to describe the perspective of electron energy dissipation at the surface. Our study reveals that non-radiative recombination through the surface states (SS) is a dominant process for the electron energy dissipation at the surface, which is suggestive of the fast scattering of injected electrons into the SS. (paper)

  15. Analysis of mechanism of carbon removal from GaAs(1 0 0) surface by atomic hydrogen

    International Nuclear Information System (INIS)

    Tomkiewicz, P.; Winkler, A.; Krzywiecki, M.; Chasse, Th.; Szuber, J.

    2008-01-01

    Etching of carbon contaminations from the GaAs(1 0 0) surface by irradiating with atomic hydrogen, which is one of the key reactions to promote high-quality thin films growth by molecular beam epitaxy (MBE), has been investigated by mass spectrometry (MS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It is shown that during the cleaning process at room temperature a total reduction of the Auger carbon signal, accompanied by desorption of methane as major reaction product, can be observed. The reaction pathways as well as the processes responsible for the observed carbon removal are discussed in detail to give a support for etching and growth quality enhancement not only in thin films epitaxy but in all atomic hydrogen promoted gas-phase III-V semiconductor processes

  16. Spatial atomic layer deposition: a route towards further industrialization of atomic layer deposition

    NARCIS (Netherlands)

    Poodt, P.; Cameron, D.C.; Dickey, E.; George, S.M.; Kuznetsov, Vladimir; Parsons, G.N.; Roozeboom, F.; Sundaram, G.; Vermeer, A.

    2012-01-01

    Spatial atomic layer deposition can be used as a high-throughput manufacturing technique in functional thin film deposition for applications such as flexible electronics. This; however, requires low-temperature processing and handling of flexible substrates. The authors investigate the process

  17. Ab initio study of atomic disorder on as-rich GaAs(111)A surface

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Mutombo, Pingo; Grosse, F.

    2015-01-01

    Roč. 641, Nov (2015), s. 330-335 ISSN 0039-6028 R&D Projects: GA ČR GPP204/10/P028 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaAs(111) * surface reconstructions * surface kinetics * density functional theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.931, year: 2015

  18. Effect of rapid thermal annealing observed by photoluminescence measurement in GaAs1-xN x layers

    International Nuclear Information System (INIS)

    Bousbih, F.; Bouzid, S.B.; Hamdouni, A.; Chtourou, R.; Harmand, J.C.

    2005-01-01

    A set of GaAs 1-x N x samples with small nitrogen content were investigated by photoluminescence (PL) measurements as function of irradiance in order to investigate the effect of rapid thermal annealing (RTA) on photoluminescence (PL) properties. The analysis of PL spectra as function of irradiance and nitrogen content shows that the PL spectra associated to the GaAs 1- x N x layers are the result of the nitrogen localized state recombination. The results are examined as a consequence of a rapid thermal annealing (RTA). The variation of the emission band peak energy (E p ), at 10 K as a function of irradiance, is fitted by a theoretical model taking into account two types of nitrogen localized states. The variation of the PL intensity versus irradiance in the range from 1.59 to 159 W/cm 2 for different GaAs 1-x N x samples confirm that the PL spectra result from the nitrogen localized state recombination

  19. Atomic-layer deposition of silicon nitride

    CERN Document Server

    Yokoyama, S; Ooba, K

    1999-01-01

    Atomic-layer deposition (ALD) of silicon nitride has been investigated by means of plasma ALD in which a NH sub 3 plasma is used, catalytic ALD in which NH sub 3 is dissociated by thermal catalytic reaction on a W filament, and temperature-controlled ALD in which only a thermal reaction on the substrate is employed. The NH sub 3 and the silicon source gases (SiH sub 2 Cl sub 2 or SiCl sub 4) were alternately supplied. For all these methods, the film thickness per cycle was saturated at a certain value for a wide range of deposition conditions. In the catalytic ALD, the selective deposition of silicon nitride on hydrogen-terminated Si was achieved, but, it was limited to only a thin (2SiO (evaporative).

  20. Textured strontium titanate layers on platinum by atomic layer deposition

    International Nuclear Information System (INIS)

    Blomberg, T.; Anttila, J.; Haukka, S.; Tuominen, M.; Lukosius, M.; Wenger, Ch.; Saukkonen, T.

    2012-01-01

    Formation of textured strontium titanate (STO) layers with large lateral grain size (0.2–1 μm) and low X-ray reflectivity roughness (∼ 1.36 nm) on Pt electrodes by industry proven atomic layer deposition (ALD) method is demonstrated. Sr(t-Bu 3 Cp) 2 , Ti(OMe) 4 and O 3 precursors at 250 °C were used to deposit Sr rich STO on Pt/Ti/SiO 2 /Si ∅200 mm substrates. After crystallization post deposition annealing at 600 °C in air, most of the STO grains showed a preferential orientation of the {001} plane parallel to the substrate surface, although other orientations were also present. Cross sectional and plan view transmission electron microscopy and electron diffraction analysis revealed more than an order of magnitude larger lateral grain sizes for the STO compared to the underlying multicrystalline {111} oriented platinum electrode. The combination of platinum bottom electrodes with ALD STO(O 3 ) shows a promising path towards the formation of single oriented STO film. - Highlights: ► Amorphous strontium titanate (STO) on platinum formed a textured film after annealing. ► Single crystal domains in 60 nm STO film were 0.2–1 μm wide. ► Most STO grains were {001} oriented.

  1. Tungsten atomic layer deposition on polymers

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, C.A. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); McCormick, J.A. [Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309-0424 (United States); Cavanagh, A.S. [Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States); Goldstein, D.N. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); Weimer, A.W. [Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309-0424 (United States); George, S.M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309-0424 (United States)], E-mail: Steven.George@Colorado.Edu

    2008-07-31

    Tungsten (W) atomic layer deposition (ALD) was investigated on a variety of polymer films and polymer particles. These polymers included polyethylene, polyvinyl chloride, polystyrene, polycarbonate, polypropylene and polymethylmethacrylate. The W ALD was performed at 80 {sup o}C using WF{sub 6} and Si{sub 2}H{sub 6} as the gas phase reactants. W ALD on flat polymer films can eventually nucleate and grow after more than 60 AB cycles. X-ray photoelectron spectroscopy studies of W ALD on polystyrene after 50 AB cycles suggested that tungsten nanoclusters are present in the W ALD nucleation regime. The W ALD nucleation is greatly facilitated by a few cycles of Al{sub 2}O{sub 3} ALD. W ALD films were grown at 80 {sup o}C on spin-coated polymers on silicon wafers after 10 AB cycles of Al{sub 2}O{sub 3} ALD. The W ALD film was observed to grow linearly with a growth rate of 3.9 A per AB cycle on the polymer films treated with the Al{sub 2}O{sub 3} ALD seed layer. The W ALD films displayed an excellent, mirror-like optical reflectivity. The resistivity was 100-400 {mu}{omega} cm for W ALD films with thicknesses from 95-845 A. W ALD was also observed on polymer particles after W ALD in a rotary reactor. Without the Al{sub 2}O{sub 3} ALD seed layer, the nucleation of W ALD directly on the polymer particles at 80 {sup o}C required > 50 AB cycles. In contrast, the polymer particles treated with only 5 AB cycles of Al{sub 2}O{sub 3} ALD were observed to blacken after 25 AB cycles of W ALD. W ALD on polymers may have applications for flexible optical mirrors, electromagnetic interference shielding and gas diffusion barriers.

  2. Simulated non-contact atomic force microscopy for GaAs surfaces based on real-space pseudopotentials

    International Nuclear Information System (INIS)

    Kim, Minjung; Chelikowsky, James R.

    2014-01-01

    We simulate non-contact atomic force microscopy (AFM) with a GaAs(1 1 0) surface using a real-space ab initio pseudopotential method. While most ab initio simulations include an explicit model for the AFM tip, our method does not introduce the tip modeling step. This approach results in a considerable reduction of computational work, and also provides complete AFM images, which can be directly compared to experiment. By analyzing tip-surface interaction forces in both our results and previous ab initio simulations, we find that our method provides very similar force profile to the pure Si tip results. We conclude that our method works well for systems in which the tip is not chemically active.

  3. Atomic structure of the GaAs(001)-c(4x4) surface: first-principles evidence for diversity of heterodimer motifs.

    Science.gov (United States)

    Penev, E; Kratzer, P; Scheffler, M

    2004-10-01

    The GaAs(001)-c(4x4) surface was studied using ab initio atomistic thermodynamics based on density-functional theory calculations. We demonstrate that in a range of stoichiometries, between those of the conventional three As-dimer and the new three Ga-As-dimer models, there exists a diversity of atomic structures featuring Ga-As heterodimers. These results fully explain the experimental scanning tunneling microscopy images and are likely to be relevant also to the c(4x4)-reconstructed (001) surfaces of other III-V semiconductors.

  4. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota

    2012-12-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  5. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota; Al-Kassab, Talaat; Kirchheim, Reiner; Pundt, Astrid A.

    2012-01-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Textured strontium titanate layers on platinum by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Blomberg, T., E-mail: tom.blomberg@asm.com [ASM Microchemistry Ltd., Vaeinoe Auerin katu 12 A, 00560 Helsinki (Finland); Anttila, J.; Haukka, S.; Tuominen, M. [ASM Microchemistry Ltd., Vaeinoe Auerin katu 12 A, 00560 Helsinki (Finland); Lukosius, M.; Wenger, Ch. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Saukkonen, T. [Aalto University, Puumiehenkuja 3, 02150 Espoo (Finland)

    2012-08-31

    Formation of textured strontium titanate (STO) layers with large lateral grain size (0.2-1 {mu}m) and low X-ray reflectivity roughness ({approx} 1.36 nm) on Pt electrodes by industry proven atomic layer deposition (ALD) method is demonstrated. Sr(t-Bu{sub 3}Cp){sub 2}, Ti(OMe){sub 4} and O{sub 3} precursors at 250 Degree-Sign C were used to deposit Sr rich STO on Pt/Ti/SiO{sub 2}/Si Empty-Set 200 mm substrates. After crystallization post deposition annealing at 600 Degree-Sign C in air, most of the STO grains showed a preferential orientation of the {l_brace}001{r_brace} plane parallel to the substrate surface, although other orientations were also present. Cross sectional and plan view transmission electron microscopy and electron diffraction analysis revealed more than an order of magnitude larger lateral grain sizes for the STO compared to the underlying multicrystalline {l_brace}111{r_brace} oriented platinum electrode. The combination of platinum bottom electrodes with ALD STO(O{sub 3}) shows a promising path towards the formation of single oriented STO film. - Highlights: Black-Right-Pointing-Pointer Amorphous strontium titanate (STO) on platinum formed a textured film after annealing. Black-Right-Pointing-Pointer Single crystal domains in 60 nm STO film were 0.2-1 {mu}m wide. Black-Right-Pointing-Pointer Most STO grains were {l_brace}001{r_brace} oriented.

  7. Charge-collection efficiency of GaAs field effect transistors fabricated with a low temperature grown buffer layer: dependence on charge deposition profile

    International Nuclear Information System (INIS)

    McMorrow, D.; Knudson, A.R.; Melinger, J.S.; Buchner, S.

    1999-01-01

    The results presented here reveal a surprising dependence of the charge-collection efficiency of LT GaAs FETs (field effect transistors) on the depth profile of the deposited charge. Investigation of the temporal dependence of the signal amplitude, carrier density contours, and potential contours reveals different mechanisms for charge collection arising from carriers deposited above and below the LT GaAs buffer layer, respectively. In particular, carriers deposited below the LT GaAs buffer layer dissipate slowly and give rise to a persistent charge collection that is associated with a bipolar-like gain process. These results may be of significance in understanding the occurrence of single-event upsets from protons, neutrons, and large-angle, glancing heavy-ion strikes. (authors)

  8. A polarized photoluminescence study of strained layer GaAs photocathodes

    International Nuclear Information System (INIS)

    Mair, R.A.

    1996-07-01

    Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ∼0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, ∼78 K and ∼12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16±.21 eV, b = -2.00±.05 eV and d = -4.87±.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data

  9. Atomic layer epitaxy of ZnO for applications in molecular beam epitaxy growth of GaN and InGaN

    International Nuclear Information System (INIS)

    Godlewski, M.; Szczerbakow, A.; Ivanov, V. Yu.; Barski, A.; Goldys, E.M.

    2000-01-01

    We report the successful atomic layer epitaxy growth of thin ZnO films and their use for GaN and InGaN epitaxy. The properties of ZnO epilayers, obtained by four different procedures, are analysed, as well as of GaN and InGaN films grown on ZnO-coated Si and GaAs by MBE. (author)

  10. Studying the InAs quantum points on the vicinal surface of a GaAs crystal by the atomic force microscopy

    CERN Document Server

    Evtikhiev, V P; Kotelnikov, E Y; Matveentsev, A V; Titkov, A N; Shkolnik, A S

    2002-01-01

    The methodology for processing the images, obtained through the atomic force microscopy, is proposed. It is shown by the concrete example, how the parameters of the InAs clusters on the vicinal surface of the GaAs crystal are determined. This makes it possible to calculate the energy levels of the electrons and holes in the quantum point with application of the previously developed cluster spherical model

  11. Structure and homoepitaxial growth of GaAs(6 3 1)

    International Nuclear Information System (INIS)

    Mendez-Garcia, V.H.; Ramirez-Arenas, F.J.; Lastras-Martinez, A.; Cruz-Hernandez, E.; Pulzara-Mora, A.; Rojas-Ramirez, J.S.; Lopez-Lopez, M.

    2006-01-01

    We have studied the surface atomic structure of GaAs(6 3 1), and the GaAs growth by molecular beam epitaxy (MBE) on this plane. After the oxide desorption process at 585 deg. Creflection high-energy electron diffraction (RHEED) showed along the [-1 2 0] direction a 2x surface reconstruction for GaAs(6 3 1)A, and a 1x pattern was observed for GaAs(6 3 1)B. By annealing the substrates for 60 min, we observed that on the A surface appeared small hilly-like features, while on GaAs(6 3 1)B surface pits were formed. For GaAs(6 3 1)A, 500 nm-thick GaAs layers were grown at 585 deg. C. The atomic force microscopy (AFM) images at the end of growth showed the self-formation of nanoscale structures with a pyramidal shape enlarged along the [5-9-3] direction. Transversal views of the bulk-truncated GaAs(6 3 1) surface model showed arrays of atomic grooves along this direction, which could influence the formation of the pyramidal structures

  12. Change of the work function and potential barrier transparency of W(100) and GaAs(110) single crystals during removing the inherent surface oxide layer

    International Nuclear Information System (INIS)

    Asalkhanov, Yu.I.; Saneev, Eh.L.

    2002-01-01

    Changes of current voltage characteristics of slow monoenergetic electron beam through the surfaces of W(100) and GaAs(100) single crystals have been measured in the process of surface oxide layers elimination. It is shown that work function is decreased and transparency coefficient of surface potential barrier is increased under increasing the temperature of vacuum annealing. Peculiarities of surface potential change under oxide layer elimination in metals and semiconductors are discussed [ru

  13. Simulation of atomic layer deposition on nanoparticle agglomerates

    NARCIS (Netherlands)

    Jin, W.; van Ommen, J.R.; Kleijn, C.R.

    2016-01-01

    Coated nanoparticles have many potential applications; production of large quantities is feasible by atomic layer deposition (ALD) on nanoparticles in a fluidized bed reactor. However, due to the cohesive interparticle forces, nanoparticles form large agglomerates, which influences the coating

  14. Atomic layer deposition: prospects for solar cell manufacturing

    NARCIS (Netherlands)

    Kessels, W.M.M.; Hoex, B.; Sanden, van de M.C.M.

    2008-01-01

    Atomic layer deposition (ALD) is a thin film growth technology that is capable of depositing uniform and conformal films on complex, three-dimensional objects with atomic precision. ALD is a rapidly growing field and it is currently at the verge of being introduced in the semiconductor industry.

  15. Determination of the nitrogen concentration in epitaxial layers of GaAs /SUB 1-x/ p /SUB x/ by the optical method

    International Nuclear Information System (INIS)

    Lupal, M.V.; Klot, B; Nikhter, K.; Pikhtin, A.N.; Trapp, M.

    1986-01-01

    This paper determines the dependence of the cross section for absorption in the A /SUB N/ line of a bound exciton on the nitrogen content in the solid solution GaAs /SUB 1-x/ P /SUB x/ by comparing the results of optical measurements with the data from secondary ionic mass spectrometry, and these results are used to study the effect of technological factors on the nitrogen concentration epitaxial layers obtained by the gas-transport method. Doping was carried out with nitrogen by injecting ammonia into the reactor zone; the partial pressure of the ammonia was varied from 1 to 25 kPa. Aside from nitrogen, the authors doped the layers with shallow donor Te. It is established that the solubility of nitrogen in the solid solution decreases as the arsenic content increases when the convenient optical method for determining the nitrogen concentration in epitaxial GaAs /SUB 1-x/ P /SUB x/ layers is used

  16. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing.

    Science.gov (United States)

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-03

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

  17. Magnetic anisotropy and anisotropic magnetoresistance of (Ga,Mn)As Layers on (113)A GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Donhauser, Daniela; Dreher, Lukas; Daeubler, Joachim; Glunk, Michael; Rapp, Christoph; Schoch, Wladimir; Sauer, Rolf; Limmer, Wolfgang [Institut fuer Halbleiterphysik, Universitaet Ulm (Germany)

    2009-07-01

    We study the magnetic anisotropy and the anisotropic magnetoresistance of compressively strained (Ga,Mn)As films with various Mn concentrations, grown on (113)A-oriented GaAs substrates. High-resolution x-ray diffraction (HRXRD) studies reveal a monoclinic symmetry of the distorted (113)A layers in agreement with an explicit calculation of the strain tensor. Based on this result, general expressions for the resistivity tensor and the free energy of single-crystalline ferromagnets are derived from a series expansion with respect to the magnetization orientation, including terms up to the fourth order. With these expressions we are able to model the measured angular dependences of our magnetotransport data with the assumption of a single ferromagnetic domain model. In order to quantitatively derive the resistivity and anisotropy parameters the longitudinal and transverse resistivities are experimentally studied for magnetic fields rotated within the (113), (33 anti 2), and (anti 110) plane at various field strengths. It turned out that some of the resistivity parameters significantly depend on the strength of the external magnetic field. Furthermore we found that the layers exhibit a uniaxial anisotropy along the [001] crystallographic axis, which can be theoretically explained based on the explicit form of the strain tensor.

  18. Compositional characterization of atomic layer deposited alumina

    Energy Technology Data Exchange (ETDEWEB)

    Philip, Anu; Thomas, Subin; Kumar, K. Rajeev [Department of Instrumentation, Cochin University of Science and Technology, Cochin-22, Kerala (India)

    2014-01-28

    As the microelectronic industry demands feature size in the order of few and sub nanometer regime, the film composition and other film properties become critical issues and ALD has emerged as the choice of industry. Aluminum oxide is a material with wide applications in electronic and optoelectronic devices and protective and ion barrier layers. Al{sub 2}O{sub 3} is an excellent dielectric because of its large band gap (8.7eV), large band offsets with silicon. We have deposited thin layers of alumina on silicon wafer (p-type) for gate dielectric applications by ALD technique and compositional characterizations of the deposited thin films were done using EDS, XPS and FTIR spectra.

  19. Compositional characterization of atomic layer deposited alumina

    International Nuclear Information System (INIS)

    Philip, Anu; Thomas, Subin; Kumar, K. Rajeev

    2014-01-01

    As the microelectronic industry demands feature size in the order of few and sub nanometer regime, the film composition and other film properties become critical issues and ALD has emerged as the choice of industry. Aluminum oxide is a material with wide applications in electronic and optoelectronic devices and protective and ion barrier layers. Al 2 O 3 is an excellent dielectric because of its large band gap (8.7eV), large band offsets with silicon. We have deposited thin layers of alumina on silicon wafer (p-type) for gate dielectric applications by ALD technique and compositional characterizations of the deposited thin films were done using EDS, XPS and FTIR spectra

  20. Growth Interruption Effect on the Fabrication of GaAs Concentric Multiple Rings by Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Fedorov A

    2010-01-01

    Full Text Available Abstract We present the molecular beam epitaxy fabrication and optical properties of complex GaAs nanostructures by droplet epitaxy: concentric triple quantum rings. A significant difference was found between the volumes of the original droplets and the final GaAs structures. By means of atomic force microscopy and photoluminescence spectroscopy, we found that a thin GaAs quantum well-like layer is developed all over the substrate during the growth interruption times, caused by the migration of Ga in a low As background.

  1. Optical and electrical properties of disordered layers in GaAs crystals produced by Si+ ion implantation

    International Nuclear Information System (INIS)

    Shigetomi, S.; Matsumori, T.

    1981-01-01

    The ion dose dependence and the annealing behavior of GaAs after implantation with 200 keV 2 x 10 12 -2 x 10 16 Si + ions/cm 2 as studied by using optical absorption, reflection, photoluminescence, sheet-resistivity, Hall effect and field effect methods. The experimental results of the optical absorption and reflection indicate that, when annealed at about 400 0 C, the disordered layers produced by high-dose implantation (2 x 10 15 -2 x 10 16 ions/cm 2 ), reorder epitaxially on the underlying crystal leaving relatively little residual disorder in the near-surface. However, from the experimental results of optical reflection, 800 0 C annealing is required for perfect recrystallization. The temperature dependence of the sheet-resistivity, with annealing temperature as a parameter, indicates that, next to the variable-range hopping and phonon-assisted hopping regions, a new region is observed. Holes, thermally-activated from localized states near the Fermi level Esub(F) to the mobility edge Esub(V) near the valence band, are responsible for electrical conduction in this region. (orig.)

  2. Epitaxial growth of matched metallic ErP0.6As0.4 layers on GaAs

    International Nuclear Information System (INIS)

    Guivarc'h, A.; Le Corre, A.; Gaulet, J.; Guenais, B.; Minier, M.; Ropars, G.; Badoz, P.A.; Duboz, J.Y.

    1990-01-01

    Successful growth of (001)ErP 0.6 As 0.4 single crystal film on (001) GaAs has been demonstrated. The epitaxial metallic layers reproducibly showed lattice mismatch below 5 10 -4 . This is, to the authors' knowledge, the first report of a stable, epitaxial and lattice-matched metal/compound semiconductor heterostructure. The ErP 0.6 As 0.4 /n-GaAs diodes yielded excellent I-V characteristics with an ideality factor of 1.1 and barrier height of 0.88 eV. For a 240 Angstrom- thick film, metallic behavior was observed with resistivities of 25 and 86 μΩcm at 1.5 K and room temperature, respectively. As the other Er compounds ErP, ErAs, ErSb and ErSi 2 , ErP 0.6 As 0.4 presents an abrupt drop in resistivity in the vicinity of the liquid helium temperature, due to a paramagnetic to antiferromagnetic phase transition

  3. Effective deleting of residual photoconductivity in high-resistance layers GaAs

    International Nuclear Information System (INIS)

    Sadaev, B.S.; Kadirova, I.T.; Sharipov, E.I.

    2004-01-01

    Full text: The phenomenon of residual photoconductivity as the storage of optical memory (OM) represents practical interest in micro and optoelectronics. The finding - out of the nature OM represents undoubtedly and scientific interest. Now residual photoconductivity (RPC) is explained by potential barriers arising because of non-monocharacteristical of distribution components of the semiconductor or carriers of a current in volume. Depending on a nature non-monocharacteristical the time relaxation RPC changes in a wide limit. The special interest represents RPC created by impurity. In the given work the results of research of a nature RPC created photos by ionization of the filled centres of chrome in compensated epitaxilogic layers arsenide galls are resulted. Epitaxilogic layers were brought up by a vertical method ZFE. Highness was reached (achieved) by special indemnification of the residual donors deep acceptors of chrome. Substrates served n-GoAs. Lassitude of i-layers has made 70-80 microns. Specific resistance of layers has made (1/3) 108 om·sm. (T= 300 K). The structures were photosensitive as at low (T = 77 K) and at room temperatures. The photosensitivity of structures in impurity to a strip of absorption chrome (= 1,4 microns) was comparable (compared) with own. The researches show, that the structures have RPC. Size RPC the greatest ambassador impurity of illumination is carrying out photoionization Cr2 + - of the centres. That is established, RPC impurity of a photocurrent is effectively erased only at certain length of a wave of external illumination

  4. Interaction of GaN epitaxial layers with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S

    2004-08-15

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H{sub 2} plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states.

  5. Interaction of GaN epitaxial layers with atomic hydrogen

    International Nuclear Information System (INIS)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S.

    2004-01-01

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H 2 plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states

  6. Silicon protected with atomic layer deposited TiO2

    DEFF Research Database (Denmark)

    Seger, Brian; Tilley, David S.; Pedersen, Thomas

    2013-01-01

    The semiconducting materials used for photoelectrochemical (PEC) water splitting must withstand the corrosive nature of the aqueous electrolyte over long time scales in order to be a viable option for large scale solar energy conversion. Here we demonstrate that atomic layer deposited titanium di...

  7. Energy-enhanced atomic layer deposition : offering more processing freedom

    NARCIS (Netherlands)

    Potts, S.E.; Kessels, W.M.M.

    2013-01-01

    Atomic layer deposition (ALD) is a popular deposition technique comprising two or more sequential, self-limiting surface reactions, which make up an ALD cycle. Energy-enhanced ALD is an evolution of traditional thermal ALD methods, whereby energy is supplied to a gas in situ in order to convert a

  8. Atomic layer deposition for nanostructured Li-ion batteries

    NARCIS (Netherlands)

    Knoops, H.C.M.; Donders, M.E.; Sanden, van de M.C.M.; Notten, P.H.L.; Kessels, W.M.M.

    2012-01-01

    Nanostructuring is targeted as a solution to achieve the improvements required for implementing Li-ion batteries in a wide range of applications. These applications range in size from electrical vehicles down to microsystems. Atomic layer deposition (ALD) could be an enabling technology for

  9. Spatial Atomic Layer Deposition of transparent conductive oxides

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Poodt, P.; Roozeboom, F.

    2013-01-01

    Undoped and indium doped ZnO films have been grown by Spatial Atomic Layer Deposition at atmospheric pressure. The electrical properties of ZnO films are controlled by varying the indium content in the range from 0 to 15 %. A minimum resistivity value of 3 mΩ•cm is measured in 180 nm thick films for

  10. Vibration atomic layer deposition for conformal nanoparticle coating

    Energy Technology Data Exchange (ETDEWEB)

    Park, Suk Won; Woo Kim, Jun; Jong Choi, Hyung; Hyung Shim, Joon, E-mail: shimm@korea.ac.kr [School of Mechanical Engineering, Korea University, Seoul 136-701 (Korea, Republic of)

    2014-01-15

    A vibration atomic layer deposition reactor was developed for fabricating a conformal thin-film coating on nanosize particles. In this study, atomic layer deposition of 10–15-nm-thick Al{sub 2}O{sub 3} films was conducted on a high-surface-area acetylene black powder with particle diameters of 200–250 nm. Intense vibration during the deposition resulted in the effective separation of particles, overcoming the interparticle agglomeration force and enabling effective diffusion of the precursor into the powder chunk; this phenomenon led to the formation of a conformal film coating on the nanopowder particles. It was also confirmed that the atomic layer deposition Al{sub 2}O{sub 3} films initially grew on the high-surface-area acetylene black powder particles as discrete islands, presumably because chemisorption of the precursor and water occurred only on a few sites on the high-surface-area acetylene black powder surface. Relatively sluggish growth of the films during the initial atomic layer deposition cycles was identified from composition analysis.

  11. Spatial atmospheric atomic layer deposition of alxzn1-xo

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Wu, Y.; Roozeboom, F.; Poodt, P.

    2013-01-01

    The possibility of growing multicomponent oxides by spatial atmospheric atomic layer deposition has been investigated. To this end, Al xZn1-xO films have been deposited using diethyl zinc (DEZ), trimethyl aluminum (TMA), and water as Zn, Al, and O precursors, respectively. When the metal precursors

  12. NREL's Advanced Atomic Layer Deposition Enables Lithium-Ion Battery

    Science.gov (United States)

    Battery Technology News Release: NREL's Advanced Atomic Layer Deposition Enables Lithium-Ion Battery increasingly demanding needs of any battery application. These lithium-ion batteries feature a hybrid solid further customized lithium-ion battery materials for high performance devices by utilizing our patented

  13. A Review of Atomic Layer Deposition for Nanoscale Devices

    Directory of Open Access Journals (Sweden)

    Edy Riyanto

    2012-12-01

    Full Text Available Atomic layer deposition (ALD is a thin film growth technique that utilizes alternating, self-saturation chemical reactions between gaseous precursors to achieve a deposited nanoscale layers. It has recently become a subject of great interest for ultrathin film deposition in many various applications such as microelectronics, photovoltaic, dynamic random access memory (DRAM, and microelectromechanic system (MEMS. By using ALD, the conformability and extreme uniformity of layers can be achieved in low temperature process. It facilitates to be deposited onto the surface in many variety substrates that have low melting temperature. Eventually it has advantages on the contribution to the wider nanodevices.

  14. A combined scanning tunneling microscope-atomic layer deposition tool.

    Science.gov (United States)

    Mack, James F; Van Stockum, Philip B; Iwadate, Hitoshi; Prinz, Fritz B

    2011-12-01

    We have built a combined scanning tunneling microscope-atomic layer deposition (STM-ALD) tool that performs in situ imaging of deposition. It operates from room temperature up to 200 °C, and at pressures from 1 × 10(-6) Torr to 1 × 10(-2) Torr. The STM-ALD system has a complete passive vibration isolation system that counteracts both seismic and acoustic excitations. The instrument can be used as an observation tool to monitor the initial growth phases of ALD in situ, as well as a nanofabrication tool by applying an electric field with the tip to laterally pattern deposition. In this paper, we describe the design of the tool and demonstrate its capability for atomic resolution STM imaging, atomic layer deposition, and the combination of the two techniques for in situ characterization of deposition.

  15. Structural and optical properties of vapor-etched porous GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Smida, A.; Laatar, F. [Photovoltaic Laboratory, Centre for Research and Technology Energy, Tourist Route Soliman, BP 95, 2050 Hammam-Lif (Tunisia); Hassen, M., E-mail: mhdhassen@yahoo.fr [Photovoltaic Laboratory, Centre for Research and Technology Energy, Tourist Route Soliman, BP 95, 2050 Hammam-Lif (Tunisia); Higher Institute of Applied Science and Technology of Sousse, City Taffala (Ibn Khaldun), 4003 Sousse (Tunisia); Ezzaouia, H. [Photovoltaic Laboratory, Centre for Research and Technology Energy, Tourist Route Soliman, BP 95, 2050 Hammam-Lif (Tunisia)

    2016-08-15

    This paper consists to present first results concerning the structure of porous GaAs layer (por-GaAs-L) prepared by using HF/HNO{sub 3} as acidic solution in vapor etching (VE) method. In order to clarify this method, we detail here its principle and explain how por-GaAs-Ls are formed, taking into account the influencing of the exposure time of the GaAs substrate to the acid vapor. The etched GaAs layers have been investigated by UV–visible and PL analysis. One porous layer was performed to be characterised by Atomic Force Microscopy (AFM), FTIR spectroscopy, and X-Ray Diffraction (XRD). The porous structure was constituted by a nanocrystals with an average size about 6 nm. These nanocrystals were calculated from XRD peak using Scherrer's formula, AFM imaging, and also by using effective mass approximation model from effective band gap. - Highlights: • Porous GaAs layer was prepared by using Vapor etching (VE) method. • Effect of VE duration on the microstructural optical properties of the GaAs substrate • Porous structure of GaAs layer was demonstrated by using SEM and AFM microscopy.

  16. Structural and optical properties of vapor-etched porous GaAs

    International Nuclear Information System (INIS)

    Smida, A.; Laatar, F.; Hassen, M.; Ezzaouia, H.

    2016-01-01

    This paper consists to present first results concerning the structure of porous GaAs layer (por-GaAs-L) prepared by using HF/HNO 3 as acidic solution in vapor etching (VE) method. In order to clarify this method, we detail here its principle and explain how por-GaAs-Ls are formed, taking into account the influencing of the exposure time of the GaAs substrate to the acid vapor. The etched GaAs layers have been investigated by UV–visible and PL analysis. One porous layer was performed to be characterised by Atomic Force Microscopy (AFM), FTIR spectroscopy, and X-Ray Diffraction (XRD). The porous structure was constituted by a nanocrystals with an average size about 6 nm. These nanocrystals were calculated from XRD peak using Scherrer's formula, AFM imaging, and also by using effective mass approximation model from effective band gap. - Highlights: • Porous GaAs layer was prepared by using Vapor etching (VE) method. • Effect of VE duration on the microstructural optical properties of the GaAs substrate • Porous structure of GaAs layer was demonstrated by using SEM and AFM microscopy.

  17. Atomic and molecular layer deposition for surface modification

    Energy Technology Data Exchange (ETDEWEB)

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, PO Box 16100, FI‐00076 AALTO (Finland); Koskinen, Jorma T.; Harlin, Ali [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland)

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  18. Experimental investigations of atomic ordering effects in the epitaxial Ga{sub x}In{sub 1-x}P, coherently grown on GaAs (100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Seredin, P.V., E-mail: paul@phys.vsu.ru [Voronezh State University, Universitetskaya pl., 1, 394006 Voronezh (Russian Federation); Goloshchapov, D.L.; Khudyakov, Yu.Yu.; Lenshin, A.S.; Lukin, A.N. [Voronezh State University, Universitetskaya pl., 1, 394006 Voronezh (Russian Federation); Arsentyev, I.N., E-mail: arsentyev@mail.ioffe.ru [Ioffe Physical and Technical Institute, Polytekhnicheskaya, 26, 194021 St-Petersburg (Russian Federation); Prutskij, Tatiana, E-mail: prutskij@yahoo.com [Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Privada 17 Norte, No 3417, Col San Miguel Hueyotlipan, 72050 Puebla, Puebla (Mexico)

    2017-03-15

    A range of structural and spectroscopic techniques were used for the study of the properties of epitaxial Ga{sub x}In{sub 1-x}P alloys with an ordered arrangement of atoms in a crystal lattice grown by MOCVD on single-crystalline substrates of GaAs (100). The appearance of atomic ordering in the coherent growth conditions of the ordered Ga{sub x}In{sub 1-x}P alloy on GaAs (100) resulted in cardinal changes of the structural and optical properties of semiconductor in comparison to disordered alloys, including the change of the crystal lattice parameter and, consequently, reduced crystal symmetry, decreased band gap and formation of two different types of surface nanorelief. This is the first report of the calculation of parameters of the crystal lattice in Ga{sub x}In{sub 1-x}P with ordering taking into account the elastic stresses dependent on long-range ordering. Based on the variance analysis data with regard to the IR-reflection spectra as well as the UV-spectroscopy data obtained in the transmission-reflection mode, the main optical characteristics of the ordered Ga{sub x}In{sub 1-x}P alloys were determined for the first time, namely, refractive index dispersion and high-frequency dielectric constant. All of the experimental results were in good agreement with the previously developed theoretical beliefs.

  19. Influence of local irradiation by argon on structure of sulsurface layers in GaAs

    International Nuclear Information System (INIS)

    Uskov, V.A.; Krasnov, A.A.; Krivelevich, S.A.; Rats, Yu. V.; Sterkhov, A.L.; Trapeznikov, V.A.

    1986-01-01

    A study was made on the influence of irradiation by argon ions with energy from 5 up to 75 keV on the structure and surface layer properties of gallium arsenie in the vicinity of pseudoboundary exposed-unexposed surface. Methods of measuring contact potential difference, electron microscopy and electron diffraction were used. It was established that irradiation by low energy ions results to sharp increase of dislocation density both in exposed and unexposed crystal part. Space charge of the value proportional to the product of irradiation dose and ion energy occurs in pseudoboundary vicinity. Dislocation distribution in pseudoboundary vicinity is determined on condition that the force affecting length per unit of each dislocation equals zero

  20. Stop Band Gap in Periodic Layers of Confined Atomic Vapor/Dielectric Medium

    International Nuclear Information System (INIS)

    Li Yuan-Yuan; Li Li; Lu Yi-Xin; Zhang Yan-Peng; Xu Ke-Wei

    2013-01-01

    A stop band gap is predicted in periodic layers of a confined atomic vapor/dielectric medium. Reflection and transmission profile of the layers over the band gap can be dramatically modified by the confined atoms and the number of layer periods. These gap and line features can be ascribed to the enhanced contribution of slow atoms induced by atom-wall collision, transient behavior of atom-light interaction and Fabry—Pérot effects in a thermal confined atomic system

  1. Characterization of core/shell structures based on CdTe and GaAs nanocrystalline layers deposited on SnO2 microwires

    Science.gov (United States)

    Ghimpu, L.; Ursaki, V. V.; Pantazi, A.; Mesterca, R.; Brâncoveanu, O.; Shree, Sindu; Adelung, R.; Tiginyanu, I. M.; Enachescu, M.

    2018-04-01

    We report the fabrication and characterization of SnO2/CdTe and SnO2/GaAs core/shell microstructures. CdTe or GaAs shell layers were deposited by radio-frequency (RF) magnetron sputtering on core SnO2 microwires synthesized by a flame-based thermal oxidation method. The produced structures were characterized by scanning electron microscopy (SEM), high-resolution scanning transmission electron microscope (HR-STEM), X-ray diffraction (XRD), Raman scattering and FTIR spectroscopy. It was found that the SnO2 core is of the rutile type, while the shells are composed of CdTe or GaAs nanocrystallites of zincblende structure with the dimensions of crystallites in the range of 10-20 nm. The Raman scattering investigations demonstrated that the quality of the porous nanostructured shell is improved by annealing at temperatures of 420-450 °C. The prospects of implementing these microstructures in intrinsic type fiber optic sensors are discussed.

  2. Monocrystalline zinc oxide films grown by atomic layer deposition

    International Nuclear Information System (INIS)

    Wachnicki, L.; Krajewski, T.; Luka, G.; Witkowski, B.; Kowalski, B.; Kopalko, K.; Domagala, J.Z.; Guziewicz, M.; Godlewski, M.; Guziewicz, E.

    2010-01-01

    In the present work we report on the monocrystalline growth of (00.1) ZnO films on GaN template by the Atomic Layer Deposition technique. The ZnO films were obtained at temperature of 300 o C using dietylzinc (DEZn) as a zinc precursor and deionized water as an oxygen precursor. High resolution X-ray diffraction analysis proves that ZnO layers are monocrystalline with rocking curve FWHM of the 00.2 peak equals to 0.07 o . Low temperature photoluminescence shows a sharp and bright excitonic line with FWHM of 13 meV.

  3. Fabrication of Hyperbolic Metamaterials using Atomic Layer Deposition

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy

     technology allowing thickness control on atomic scale. As the deposition relies on a surface reaction, conformal pinhole free films can be deposited on various substrates with advanced topology. This method has been a central theme of the project and a core fabrication technique of plasmonic and dielectric...... in dielectric host, the fabrication is still challenging, since ultrathin, continuous, pinhole free nanometer-scale coatings are desired. The required high-quality thin layers have been fabricated using atomic layer deposition (ALD). It is a relatively new, cyclic, self-limiting thin film deposition......, especially in the infrared range, result in high loss and weak connement to the surface. Additionally, the most implemented metals in plasmonics such as Au and Ag are diffcult to pattern at nanoscale due to their limited chemistry, adhesion or oxidation issues. Therefore the implementation of...

  4. Carbon nanotube forests growth using catalysts from atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Bingan; Zhang, Can; Esconjauregui, Santiago; Xie, Rongsi; Zhong, Guofang; Robertson, John [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Bhardwaj, Sunil [Istituto Officina dei Materiali-CNR Laboratorio TASC, s.s. 14, km 163.4, I-34012 Trieste (Italy); Sincrotone Trieste S.C.p.A., s.s. 14, km 163.4, I-34149 Trieste (Italy); Cepek, Cinzia [Istituto Officina dei Materiali-CNR Laboratorio TASC, s.s. 14, km 163.4, I-34012 Trieste (Italy)

    2014-04-14

    We have grown carbon nanotubes using Fe and Ni catalyst films deposited by atomic layer deposition. Both metals lead to catalytically active nanoparticles for growing vertically aligned nanotube forests or carbon fibres, depending on the growth conditions and whether the substrate is alumina or silica. The resulting nanotubes have narrow diameter and wall number distributions that are as narrow as those grown from sputtered catalysts. The state of the catalyst is studied by in-situ and ex-situ X-ray photoemission spectroscopy. We demonstrate multi-directional nanotube growth on a porous alumina foam coated with Fe prepared by atomic layer deposition. This deposition technique can be useful for nanotube applications in microelectronics, filter technology, and energy storage.

  5. Overview of atomic layer etching in the semiconductor industry

    Energy Technology Data Exchange (ETDEWEB)

    Kanarik, Keren J., E-mail: keren.kanarik@lamresearch.com; Lill, Thorsten; Hudson, Eric A.; Sriraman, Saravanapriyan; Tan, Samantha; Marks, Jeffrey; Vahedi, Vahid; Gottscho, Richard A. [Lam Research Corporation, 4400 Cushing Parkway, Fremont, California 94538 (United States)

    2015-03-15

    Atomic layer etching (ALE) is a technique for removing thin layers of material using sequential reaction steps that are self-limiting. ALE has been studied in the laboratory for more than 25 years. Today, it is being driven by the semiconductor industry as an alternative to continuous etching and is viewed as an essential counterpart to atomic layer deposition. As we enter the era of atomic-scale dimensions, there is need to unify the ALE field through increased effectiveness of collaboration between academia and industry, and to help enable the transition from lab to fab. With this in mind, this article provides defining criteria for ALE, along with clarification of some of the terminology and assumptions of this field. To increase understanding of the process, the mechanistic understanding is described for the silicon ALE case study, including the advantages of plasma-assisted processing. A historical overview spanning more than 25 years is provided for silicon, as well as ALE studies on oxides, III–V compounds, and other materials. Together, these processes encompass a variety of implementations, all following the same ALE principles. While the focus is on directional etching, isotropic ALE is also included. As part of this review, the authors also address the role of power pulsing as a predecessor to ALE and examine the outlook of ALE in the manufacturing of advanced semiconductor devices.

  6. Overview of atomic layer etching in the semiconductor industry

    International Nuclear Information System (INIS)

    Kanarik, Keren J.; Lill, Thorsten; Hudson, Eric A.; Sriraman, Saravanapriyan; Tan, Samantha; Marks, Jeffrey; Vahedi, Vahid; Gottscho, Richard A.

    2015-01-01

    Atomic layer etching (ALE) is a technique for removing thin layers of material using sequential reaction steps that are self-limiting. ALE has been studied in the laboratory for more than 25 years. Today, it is being driven by the semiconductor industry as an alternative to continuous etching and is viewed as an essential counterpart to atomic layer deposition. As we enter the era of atomic-scale dimensions, there is need to unify the ALE field through increased effectiveness of collaboration between academia and industry, and to help enable the transition from lab to fab. With this in mind, this article provides defining criteria for ALE, along with clarification of some of the terminology and assumptions of this field. To increase understanding of the process, the mechanistic understanding is described for the silicon ALE case study, including the advantages of plasma-assisted processing. A historical overview spanning more than 25 years is provided for silicon, as well as ALE studies on oxides, III–V compounds, and other materials. Together, these processes encompass a variety of implementations, all following the same ALE principles. While the focus is on directional etching, isotropic ALE is also included. As part of this review, the authors also address the role of power pulsing as a predecessor to ALE and examine the outlook of ALE in the manufacturing of advanced semiconductor devices

  7. Atomic layer deposition of dielectrics for carbon-based electronics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J., E-mail: jiyoung.kim@utdallas.edu; Jandhyala, S.

    2013-11-01

    Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics.

  8. Atomic layer deposition of dielectrics for carbon-based electronics

    International Nuclear Information System (INIS)

    Kim, J.; Jandhyala, S.

    2013-01-01

    Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics

  9. Plasma atomic layer etching using conventional plasma equipment

    International Nuclear Information System (INIS)

    Agarwal, Ankur; Kushner, Mark J.

    2009-01-01

    The decrease in feature sizes in microelectronics fabrication will soon require plasma etching processes having atomic layer resolution. The basis of plasma atomic layer etching (PALE) is forming a layer of passivation that allows the underlying substrate material to be etched with lower activation energy than in the absence of the passivation. The subsequent removal of the passivation with carefully tailored activation energy then removes a single layer of the underlying material. If these goals are met, the process is self-limiting. A challenge of PALE is the high cost of specialized equipment and slow processing speed. In this work, results from a computational investigation of PALE will be discussed with the goal of demonstrating the potential of using conventional plasma etching equipment having acceptable processing speeds. Results will be discussed using inductively coupled and magnetically enhanced capacitively coupled plasmas in which nonsinusoidal waveforms are used to regulate ion energies to optimize the passivation and etch steps. This strategy may also enable the use of a single gas mixture, as opposed to changing gas mixtures between steps

  10. Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi [Department of Chemistry, Aalto University, FI-00076 Aalto (Finland)

    2014-01-15

    A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4′-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigated through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.

  11. Photoluminescence of phosphorus atomic layer doped Ge grown on Si

    Science.gov (United States)

    Yamamoto, Yuji; Nien, Li-Wei; Capellini, Giovanni; Virgilio, Michele; Costina, Ioan; Schubert, Markus Andreas; Seifert, Winfried; Srinivasan, Ashwyn; Loo, Roger; Scappucci, Giordano; Sabbagh, Diego; Hesse, Anne; Murota, Junichi; Schroeder, Thomas; Tillack, Bernd

    2017-10-01

    Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 × 1013 cm-2 separated by 4 nm Ge spacer are selectively deposited at 300 °C on a 700 nm thick P-doped Ge buffer layer of 1.4 × 1019 cm-3 on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 × 1020 cm-3 with abrupt P delta profiles is formed by the P-ALD process. Compared to the P-doped Ge buffer layer, a reduced PL intensity is observed, which might be caused by a higher density of point defects in the P delta doped Ge layer. The peak position is shifted by ˜0.1 eV towards lower energy, indicating an increased active carrier concentration in the P-delta doped Ge layer. By introducing annealing at 400 °C to 500 °C after each Ge spacer deposition, P desorption and diffusion is observed resulting in relatively uniform P profiles of ˜2 × 1019 cm-3. Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.

  12. Effect of thermal annealing on optical properties of implanted GaAs

    NARCIS (Netherlands)

    Kulik, M; Komarov, FF; Maczka, D

    GaAs samples doped with indium atoms by ion implantation and thermal annealed were studied using a channelling method, Rutherford backscattering, and an ellipsometry. From these measurements it was observed that the layer implanted with 3 x 10(16) cm(-2) indium dose was totally damaged and its

  13. On the optimization of asymmetric barrier layers in InAlGaAs/AlGaAs laser heterostructures on GaAs substrates

    International Nuclear Information System (INIS)

    Zhukov, A. E.; Asryan, L. V.; Semenova, E. S.; Zubov, F. I.; Kryzhanovskaya, N. V.; Maximov, M. V.

    2015-01-01

    Band offsets at the heterointerface are calculated for various combinations of InAlGaAs/AlGaAs heteropairs that can be synthesized on GaAs substrates in the layer-by-layer pseudomorphic growth mode. Patterns which make it possible to obtain an asymmetric barrier layer providing the almost obstruction-free transport of holes and the highest possible barrier height for electrons are found. The optimal compositions of both compounds (In 0.232 Al 0.594 Ga 0.174 As/Al 0.355 Ga 0.645 As) at which the flux of electrons across the barrier is at a minimum are determined with consideration for the critical thickness of the indium-containing quaternary solid solution

  14. Plasma treatment of porous GaAs surface formed by electrochemical etching method: Characterization and properties

    International Nuclear Information System (INIS)

    Naddaf, M.; Saloum, S.

    2008-12-01

    Porous GaAs samples were formed by electrochemical anodic etching of Zn doped p-type GaAs (100) wafers at different etching parameters (time, mode of applied voltage or current and electrolyte). The effect of etching parameters and plasma surface treatment on the optical properties of the prepared sample has been investigated by using room temperature photoluminescence (PL), Raman spectroscopy and reflectance spectroscopic measurements in the range (400-800 nm). The surface morphological changes were studied by using atomic force microscope. It has been found that etching parameters can be controlled to produce a considerably low optical reflectivity porous GaAs layer, attractive for use in solar cells. In addition, it has been observed that the deposition of plasma polymerized HMDSO thin film on porous GaAs surface can be utilized to produce a surface with novel optical properties interesting for solar cells and optoelectronic devices. (author)

  15. Deposition of HgTe by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-04-01

    Full Text Available This paper describes the first instance of HgTe growth by electrochemical atomic layer epitaxy (EC-ALE). EC-ALE is the electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), all of which are based on the growth...

  16. Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer

    Science.gov (United States)

    Li, Qiang; Lai, Billy; Lau, Kei May

    2017-10-01

    We report epitaxial growth of GaSb nano-ridge structures and planar thin films on V-groove patterned Si (001) substrates by leveraging the aspect ratio trapping technique. GaSb was deposited on {111} Si facets of the V-shaped trenches using metal-organic chemical vapor deposition with a 7 nm GaAs growth initiation layer. Transmission electron microscopy analysis reveals the critical role of the GaAs layer in providing a U-shaped surface for subsequent GaSb epitaxy. A network of misfit dislocations was uncovered at the GaSb/GaAs hetero-interface. We studied the evolution of the lattice relaxation as the growth progresses from closely pitched GaSb ridges to coalesced thin films using x-ray diffraction. The omega rocking curve full-width-at-half-maximum of the resultant GaSb thin film is among the lowest values reported by molecular beam epitaxy, substantiating the effectiveness of the defect necking mechanism. These results thus present promising opportunities for the heterogeneous integration of devices based on 6.1 Å family compound semiconductors.

  17. Issues involved in the atomic layer deposition of metals

    Science.gov (United States)

    Grubbs, Robert Kimes

    Auger Electron Spectroscopy (AES) was used to study the nucleation and growth of tungsten on aluminum oxide surfaces. Tungsten metal was deposited using Atomic Layer Deposition (ALD) techniques. ALD uses sequential surface reactions to deposit material with atomic layer control. W ALD is performed using sequential exposures of WF6 and Si2H6. The step-wise nature of W ALD allows nucleation studies to be performed by analyzing the W surface concentration after each ALD reaction. Nucleation and growth regions can be identified by quantifying the AES signal intensities from both the W surface and the Al2O3 substrate. W nucleation occurred in 3 ALD reaction cycles. The AES results yielded a nucleation rate of 1.0 A/ALD cycle and a growth rate of ≈3 A/ALD cycle. AES studies also explored the nucleation and growth of Al2O3 on W. Al2O3 nucleated in 1 ALD cycle giving a nucleation rate of 3.5 A/ALD cycle and a subsequent growth rate of 1.0 A/ALD cycle. Mass spectrometry was then used to study the ALD reaction chemistry of tungsten deposition. Because of the step-wise nature of the W ALD chemistry, each W ALD reaction could be studied independently. The gaseous mass products were identified from both the WF6 and Si2H6 reactions. H2, HF and SiF4 mass products were observed for the WF6 reaction. The Si2H6 reaction displayed a room temperature reaction and a 200°C reaction. Products from the room temperature Si2H6 reaction were H2 and SiF3H. The reaction at 200°C yielded only H2 as a reaction product. H2 desorption from the surface contributes to the 200°C Si2H6 reaction. AES was used to confirm that the gas phase reaction products are correlated with a change in the surface species. Atomic hydrogen reduction of metal halides and oganometallic compounds provides another method for depositing metals with atomic layer control. The quantity of atomic hydrogen necessary to perform this chemistry is critical to the metal ALD process. A thermocouple probe was constructed to

  18. Effects of spatial confinement and layer disorder in photoluminescence of GaAs1-xBix/GaAs heterostructures

    International Nuclear Information System (INIS)

    Mazur, Yu I; Dorogan, V G; Benamara, M; Ware, M E; Salamo, G J; Schmidbauer, M; Tarasov, G G; Johnson, S R; Lu, X; Yu, S-Q; Tiedje, T

    2013-01-01

    The structural and optical properties of a set of high-quality GaAs 1-x Bi x /GaAs quantum well (QW) heterostructures with Bi concentrations ranging from 3.5% to 6.7% are studied. The energies of the excitonic ground state transitions are determined as a function of Bi concentration and spatial confinement. The influence of material disorder on the optical properties of QWs is investigated. It is determined that trap-related luminescence responds differently to temperature changes depending on whether the Bi concentration is more or less than 5%. Below 5% it contributes significantly to the overall photoluminescence line shape whereas above 5%, it is insignificant.

  19. Atomic layer deposition of a MoS₂ film.

    Science.gov (United States)

    Tan, Lee Kheng; Liu, Bo; Teng, Jing Hua; Guo, Shifeng; Low, Hong Yee; Tan, Hui Ru; Chong, Christy Yuen Tung; Yang, Ren Bin; Loh, Kian Ping

    2014-09-21

    A mono- to multilayer thick MoS₂ film has been grown by using the atomic layer deposition (ALD) technique at 300 °C on a sapphire wafer. ALD provides precise control of the MoS₂ film thickness due to pulsed introduction of the reactants and self-limiting reactions of MoCl₅ and H₂S. A post-deposition annealing of the ALD-deposited monolayer film improves the crystallinity of the film, which is evident from the presence of triangle-shaped crystals that exhibit strong photoluminescence in the visible range.

  20. Effects of buffer layer on the structural and electrical properties of InAsSb epilayers grown on GaAs(001)

    International Nuclear Information System (INIS)

    Jayavel, P.; Nakamura, S.; Koyama, T.; Hayakawa, Y.

    2006-01-01

    InAsSb ternary epilayers with arsenic composition of 0.5 have been grown on GaAs(001) substrates. Linear-graded and step-graded InAsSb buffer layers with an InSb layer have been used to relax lattice mismatch between the epilayer and substrate. X-ray diffraction results of the epilayers indicate that an enhancement in the peak intensity of the buffer layer samples is due to improved crystalline quality of the epilayers. We find that the growth technique of the buffer layer strongly influences the surface morphology and roughness of the epilayer. Hall effect measurements of the step-graded buffer layer samples show an order of magnitude higher electron mobility than the direct and linear-graded buffer layer samples. These results demonstrate that high crystalline quality and electron mobility of the InAs 0.5 Sb 0.5 ternary epilayers can be achieved by using the step-graded InAsSb buffer layers. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Spectroscopic ellipsometry analysis of GaAs1-xNx layers grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ben Sedrine, N.; Rihani, J.; Stehle, J.L.; Harmand, J.C.; Chtourou, R.

    2008-01-01

    In this work, we present the effect of nitrogen incorporation on the dielectric function of GaAsN samples, grown by molecular beam epitaxy (MBE) followed by a rapid thermal annealing (for 90 s at 680 deg. C). The GaAs 1-x N x samples with N content up to 1.5% (x = 0.0%, 0.1%, 0.5%, 1.5%), are investigated using room temperature spectroscopic ellipsometry (SE). The optical transitions in the spectral region around 3 eV are analyzed by fitting analytical critical point line shapes to the second derivative of the dielectric function. It was found that the features associated with E 1 and E 1 + Δ 1 transitions are blue-shifted and become less sharp with increasing nitrogen incorporation, in contrast to the case of E 0 transition energy in GaAs 1-x N x . An increase of the split-off Δ 1 energy with nitrogen content was also obtained, in agreement to results found with MOVPE GaAs 1-x N x grown samples

  2. Atomic layer deposition of alternative glass microchannel plates

    Energy Technology Data Exchange (ETDEWEB)

    O' Mahony, Aileen, E-mail: aom@incomusa.com; Craven, Christopher A.; Minot, Michael J.; Popecki, Mark A.; Renaud, Joseph M.; Bennis, Daniel C.; Bond, Justin L.; Stochaj, Michael E.; Foley, Michael R.; Adams, Bernhard W. [Incom, Inc., 294 Southbridge Road, Charlton, Massachusetts 01507 (United States); Mane, Anil U.; Elam, Jeffrey W. [Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Ertley, Camden; Siegmund, Oswald H. W. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, California 94720 (United States)

    2016-01-15

    The technique of atomic layer deposition (ALD) has enabled the development of alternative glass microchannel plates (MCPs) with independently tunable resistive and emissive layers, resulting in excellent thickness uniformity across the large area (20 × 20 cm), high aspect ratio (60:1 L/d) glass substrates. Furthermore, the use of ALD to deposit functional layers allows the optimal substrate material to be selected, such as borosilicate glass, which has many benefits compared to the lead-oxide glass used in conventional MCPs, including increased stability and lifetime, low background noise, mechanical robustness, and larger area (at present up to 400 cm{sup 2}). Resistively stable, high gain MCPs are demonstrated due to the deposition of uniform ALD resistive and emissive layers on alternative glass microcapillary substrates. The MCP performance characteristics reported include increased stability and lifetime, low background noise (0.04 events cm{sup −2} s{sup −1}), and low gain variation (±5%)

  3. Atomic scale characterization of ion-induced amorphization of GaAs and InAs using PAC spectroscopy

    International Nuclear Information System (INIS)

    Dogra, R.; Byrne, A.P.; Ridgway, M.C.

    2005-01-01

    Single crystals of GaAs (100) and InAs (100) were implanted with 1-7 MeV 74 Ge ions over a wide dose range at liquid nitrogen temperature. The implanted substrates were investigated with respect to the damage production by means of perturbed angular correlation spectroscopy based upon hyperfine interactions of nuclear electromagnetic moments of probe nuclei with extra-nuclear fields. The perturbed angular correlation measurements were performed at room temperature utilizing the 111 In/Cd radioisotope probe nuclei. The crystalline, disordered and amorphous probe environments were identified from the measurements. The defect production is described within the framework of different amorphization models. (author). 6 refs., 2 figs

  4. Atomic layer deposition of GaN at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ozgit, Cagla; Donmez, Inci; Alevli, Mustafa; Biyikli, Necmi [UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey)

    2012-01-15

    The authors report on the self-limiting growth of GaN thin films at low temperatures. Films were deposited on Si substrates by plasma-enhanced atomic layer deposition using trimethylgallium (TMG) and ammonia (NH{sub 3}) as the group-III and -V precursors, respectively. GaN deposition rate saturated at 185 deg. C for NH{sub 3} doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to {approx}385 deg. C. Deposition rate, which is constant at {approx}0.51 A/cycle within the temperature range of 250 - 350 deg. C, increased slightly as the temperature decreased to 185 deg. C. In the bulk film, concentrations of Ga, N, and O were constant at {approx}36.6, {approx}43.9, and {approx}19.5 at. %, respectively. C was detected only at the surface and no C impurities were found in the bulk film. High oxygen concentration in films was attributed to the oxygen impurities present in group-V precursor. High-resolution transmission electron microscopy studies revealed a microstructure consisting of small crystallites dispersed in an amorphous matrix.

  5. Titanium dioxide thin films by atomic layer deposition: a review

    Science.gov (United States)

    Niemelä, Janne-Petteri; Marin, Giovanni; Karppinen, Maarit

    2017-09-01

    Within its rich phase diagram titanium dioxide is a truly multifunctional material with a property palette that has been shown to span from dielectric to transparent-conducting characteristics, in addition to the well-known catalytic properties. At the same time down-scaling of microelectronic devices has led to an explosive growth in research on atomic layer deposition (ALD) of a wide variety of frontier thin-film materials, among which TiO2 is one of the most popular ones. In this topical review we summarize the advances in research of ALD of titanium dioxide starting from the chemistries of the over 50 different deposition routes developed for TiO2 and the resultant structural characteristics of the films. We then continue with the doped ALD-TiO2 thin films from the perspective of dielectric, transparent-conductor and photocatalytic applications. Moreover, in order to cover the latest trends in the research field, both the variously constructed TiO2 nanostructures enabled by ALD and the Ti-based hybrid inorganic-organic films grown by the emerging ALD/MLD (combined atomic/molecular layer deposition) technique are discussed.

  6. Atomic layer deposition of superparamagnetic and ferrimagnetic magnetite thin films

    International Nuclear Information System (INIS)

    Zhang, Yijun; Liu, Ming; Ren, Wei; Zhang, Yuepeng; Chen, Xing; Ye, Zuo-Guang

    2015-01-01

    One of the key challenges in realizing superparamagnetism in magnetic thin films lies in finding a low-energy growth way to create sufficiently small grains and magnetic domains which allow the magnetization to randomly and rapidly reverse. In this work, well-defined superparamagnetic and ferrimagnetic Fe 3 O 4 thin films are successfully prepared using atomic layer deposition technique by finely controlling the growth condition and post-annealing process. As-grown Fe 3 O 4 thin films exhibit a conformal surface and poly-crystalline nature with an average grain size of 7 nm, resulting in a superparamagnetic behavior with a blocking temperature of 210 K. After post-annealing in H 2 /Ar at 400 °C, the as-grown α−Fe 2 O 3 sample is reduced to Fe 3 O 4 phase, exhibiting a ferrimagnetic ordering and distinct magnetic shape anisotropy. Atomic layer deposition of magnetite thin films with well-controlled morphology and magnetic properties provides great opportunities for integrating with other order parameters to realize magnetic nano-devices with potential applications in spintronics, electronics, and bio-applications

  7. Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

    OpenAIRE

    Lei, Qingyu; Golalikhani, Maryam; Davidson, Bruce A.; Liu, Guozhen; Schlom, D. G.; Qiao, Qiao; Zhu, Yimei; Chandrasena, Ravini U.; Yang, Weibing; Gray, Alexander X.; Arenholz, Elke; Farrar, Andrew K.; Tenne, Dmitri A.; Hu, Minhui; Guo, Jiandong

    2016-01-01

    Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show here, with examples of Sr1+xTi1-xO3+delta, Ruddlesden-Popper phase Lan+1NinO3n+1 (n = 4), and LaAl1+yO3(1+0.5y)/SrTiO3 interfaces, that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art...

  8. Atomic layer deposition of W - based layers on SiO2

    NARCIS (Netherlands)

    van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; Holleman, J.; Wolters, Robertus A.M.; Aarnink, Antonius A.I.

    2003-01-01

    W and W1-xNx , where x= 15- 22 at%, thin films were grown using the ALD (Atomic Layer Deposition) principle. Growth rate of W films is about 4- 5 monolayers/ cycle at 300- 350 ºC. Growth rate of W1-xNx is 0.5 monolayer/cycle at 325- 350 ºC. Standard Deviation (STDV) of thickness is about 2%

  9. Density of states of adsorbed sulphur atoms on pristine and defective graphene layers

    International Nuclear Information System (INIS)

    Arellano, J S

    2017-01-01

    The density of states for adsorbed sulphur atom on a graphene layer system is discussed for pristine graphene layer and for mono and divacancies on the graphene layer. To our knowledge this is the first time that an entire adsorption of the sulphur atom is reported at the plane of the carbon atoms, when there is a pair of closer vacancies at the graphene layer. (paper)

  10. Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

    Science.gov (United States)

    Cabrero-Vilatela, A.; Alexander-Webber, J. A.; Sagade, A. A.; Aria, A. I.; Braeuninger-Weimer, P.; Martin, M.-B.; Weatherup, R. S.; Hofmann, S.

    2017-12-01

    The transfer of chemical vapour deposited graphene from its parent growth catalyst has become a bottleneck for many of its emerging applications. The sacrificial polymer layers that are typically deposited onto graphene for mechanical support during transfer are challenging to remove completely and hence leave graphene and subsequent device interfaces contaminated. Here, we report on the use of atomic layer deposited (ALD) oxide films as protective interface and support layers during graphene transfer. The method avoids any direct contact of the graphene with polymers and through the use of thicker ALD layers (≥100 nm), polymers can be eliminated from the transfer-process altogether. The ALD film can be kept as a functional device layer, facilitating integrated device manufacturing. We demonstrate back-gated field effect devices based on single-layer graphene transferred with a protective Al2O3 film onto SiO2 that show significantly reduced charge trap and residual carrier densities. We critically discuss the advantages and challenges of processing graphene/ALD bilayer structures.

  11. Protective silicon coating for nanodiamonds using atomic layer deposition

    International Nuclear Information System (INIS)

    Lu, J.; Wang, Y.H.; Zang, J.B.; Li, Y.N.

    2007-01-01

    Ultrathin silicon coating was deposited on nanodiamonds using atomic layer deposition (ALD) from gaseous monosilane (SiH 4 ). The coating was performed by sequential reaction of SiH 4 saturated adsorption and in situ decomposition. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to investigate the structural and morphological properties of the coating. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to compare the thermal stability of nanodiamonds before and after silicon coating. The results confirmed that the deposited cubic phase silicon coating was even and continuous. The protective silicon coating could effectively improve the oxidation resistance of nanodiamonds in air flow, which facilitates the applications of nanodiamonds that are commonly hampered by their poor thermal stability

  12. Protective silicon coating for nanodiamonds using atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lu, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004 (China); College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004 (China); Wang, Y.H. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004 (China); College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004 (China); Zang, J.B. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004 (China) and College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004 (China)]. E-mail: diamondzjb@163.com; Li, Y.N. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004 (China); College of Materials Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004 (China)

    2007-01-30

    Ultrathin silicon coating was deposited on nanodiamonds using atomic layer deposition (ALD) from gaseous monosilane (SiH{sub 4}). The coating was performed by sequential reaction of SiH{sub 4} saturated adsorption and in situ decomposition. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to investigate the structural and morphological properties of the coating. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to compare the thermal stability of nanodiamonds before and after silicon coating. The results confirmed that the deposited cubic phase silicon coating was even and continuous. The protective silicon coating could effectively improve the oxidation resistance of nanodiamonds in air flow, which facilitates the applications of nanodiamonds that are commonly hampered by their poor thermal stability.

  13. Atomic layer deposition overcoating: tuning catalyst selectivity for biomass conversion.

    Science.gov (United States)

    Zhang, Hongbo; Gu, Xiang-Kui; Canlas, Christian; Kropf, A Jeremy; Aich, Payoli; Greeley, Jeffrey P; Elam, Jeffrey W; Meyers, Randall J; Dumesic, James A; Stair, Peter C; Marshall, Christopher L

    2014-11-03

    The terraces, edges, and facets of nanoparticles are all active sites for heterogeneous catalysis. These different active sites may cause the formation of various products during the catalytic reaction. Here we report that the step sites of Pd nanoparticles (NPs) can be covered precisely by the atomic layer deposition (ALD) method, whereas the terrace sites remain as active component for the hydrogenation of furfural. Increasing the thickness of the ALD-generated overcoats restricts the adsorption of furfural onto the step sites of Pd NPs and increases the selectivity to furan. Furan selectivities and furfural conversions are linearly correlated for samples with or without an overcoating, though the slopes differ. The ALD technique can tune the selectivity of furfural hydrogenation over Pd NPs and has improved our understanding of the reaction mechanism. The above conclusions are further supported by density functional theory (DFT) calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

    Science.gov (United States)

    Zuzuarregui, Ana; Coto, Borja; Rodríguez, Jorge; Gregorczyk, Keith E.; Ruiz de Gopegui, Unai; Barriga, Javier; Knez, Mato

    2015-08-01

    Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

  15. Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zuzuarregui, Ana, E-mail: a.zuzuarregui@nanogune.eu; Gregorczyk, Keith E. [CIC Nanogune Consolider, de Tolosa Hiribidea 76, 20018 San Sebastián (Spain); Coto, Borja; Ruiz de Gopegui, Unai; Barriga, Javier [IK4-Tekniker, Iñaki Goenaga 5, 20600 Eibar (Spain); Rodríguez, Jorge [Torresol Energy (SENER Group), Avda. de Zugazarte 61, 48930 Las Arenas (Spain); Knez, Mato [CIC Nanogune Consolider, de Tolosa Hiribidea 76, 20018 San Sebastián (Spain); IKERBASQUE Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao (Spain)

    2015-08-10

    Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

  16. Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

    International Nuclear Information System (INIS)

    Zuzuarregui, Ana; Gregorczyk, Keith E.; Coto, Borja; Ruiz de Gopegui, Unai; Barriga, Javier; Rodríguez, Jorge; Knez, Mato

    2015-01-01

    Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur

  17. Improvement of oxidation resistance of copper by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chang, M.L.; Cheng, T.C. [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China); Lin, M.C. [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, No. 250, Wu-Hsing Street, Taipei 110, Taiwan (China); Lin, H.C., E-mail: hclinntu@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China); Chen, M.J., E-mail: mjchen@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China)

    2012-10-01

    Graphical abstract: Results of glancing incident angle diffraction (GIXD) show the bare-Cu specimen was attacked by oxidation, whereas the coated-Cu specimens prevented from this problem. Highlights: Black-Right-Pointing-Pointer Deposition of Al{sub 2}O{sub 3} films on pure copper by an atomic layer deposition (ALD) technique. Black-Right-Pointing-Pointer Analysis of properties of the films coated at various substrate temperatures using the ALD technique. Black-Right-Pointing-Pointer Identification of the improvement of oxidation resistance of pure copper by the ALD-Al{sub 2}O{sub 3} films. Black-Right-Pointing-Pointer Assessment of the durability of the ALD-Al{sub 2}O{sub 3} films by adhesion strength. - Abstract: Al{sub 2}O{sub 3} films were deposited by the atomic layer deposition (ALD) technique onto pure copper at temperatures in the range 100-200 Degree-Sign C. The chemical composition, microstructure, and mechanic properties of the ALD-deposited Al{sub 2}O{sub 3} films were systematically analyzed. The variations in the film characteristics with substrate temperature were observed. Oxidation trials revealed that 20-nm-thick Al{sub 2}O{sub 3} films deposited at a substrate temperature as low as 100 Degree-Sign C suppress oxidative attack on pure copper. The Al{sub 2}O{sub 3} films also showed excellent durability of adhesion strength, according to predictions using the Coffin-Manson model based on the results of accelerated temperature cycling tests. These features indicate that ALD-deposited Al{sub 2}O{sub 3} film is a very promising candidate to be a protective coating for pure copper.

  18. Investigation of the fabrication mechanism of self-assembled GaAs quantum rings grown by droplet epitaxy.

    Science.gov (United States)

    Tong, C Z; Yoon, S F

    2008-09-10

    We have directly imaged the formation of a GaAs quantum ring (QR) using droplet epitaxy followed by annealing in arsenic ambient. Based on the atomic force micrograph measurement and the analysis of surface energy, we determine that the formation of self-assembled GaAs QRs is due to the gallium atom's diffusion and crystallization driven by the gradient of surface energy. The phenomenon that GaAs is etched by the gallium droplets is reported and analyzed. It has been demonstrated that the epitaxy layers, such as AlAs and InGaP, can be used as the etching stop layer and hence can be used to control the shape and height of the QRs.

  19. Scalable synthesis of palladium nanoparticle catalysts by atomic layer deposition

    International Nuclear Information System (INIS)

    Liang Xinhua; Lyon, Lauren B.; Jiang Yingbing; Weimer, Alan W.

    2012-01-01

    Atomic layer deposition (ALD) was used to produce Pd/Al 2 O 3 catalysts using sequential exposures of Pd(II) hexafluoroacetylacetonate and formalin at 200 °C in a fluidized bed reactor. The ALD-prepared Pd/alumina catalysts were characterized by various methods including hydrogen chemisorption, XPS, and TEM, and compared with a commercially available 1 wt% Pd/alumina catalyst, which was also characterized. The content of Pd on alumina support and the size of Pd nanoparticles can be controlled by the number of ALD-coating cycles and the dose time of the Pd precursor. One layer of organic component from the Pd precursor remained on the Pd particle surface. The ALD 0.9 wt% Pd/alumina had greater active metal surface area and percent metal dispersion than the commercial 1 wt% Pd/alumina catalyst. The ALD and commercial catalysts were subjected to catalytic testing to determine their relative activities for glucose oxidation to gluconic acid in aqueous solution. The ALD 0.9 wt% Pd/alumina catalyst had comparable activity as compared to the commercial 1 wt% Pd catalyst. No noticeable amount of Pd leaching was observed for the ALD-prepared catalysts during the vigorously stirred reaction.

  20. Atomic layer deposition of TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, Massimo; Dessmann, Nils; Staedter, Matthias; Friedrich, Daniel; Michling, Marcel; Schmeisser, Dieter [BTU-Cottbus, Konrad-Wachsmann-Allee 17, 03046 Cottbus (Germany)

    2011-07-01

    We present a study of the initial growth of TiO{sub 2} on Si(111) by atomic layer deposition (ALD). The Si substrate was etched with NH{sub 4}F before ALD to remove the native oxide film and to produce a Si-H termination. In-situ experiments by means of photoemission and X-ray absorption spectroscopy were conducted with synchrotron radiation on Ti-oxide films produced using Ti-tetra-iso-propoxide (TTIP) and water as precursors. O 1s, Ti 2p, C 1s, and S i2p core level, and O 1s and Ti 2p absorption edges show the transition of the Ti-oxide properties during the first layers. The growth starts with a very small growth rate (0.03 nm/cycle) due to the growth inhibition of the Si-H termination and proceeds with higher growth rate (0.1 nm/cycle) after 1.5 nm Ti-oxide has been deposited.

  1. Engineering Particle Surface Chemistry and Electrochemistry with Atomic Layer Deposition

    Science.gov (United States)

    Jackson, David Hyman Kentaro

    Atomic layer deposition (ALD) is a vapor phase thin film coating technique that relies on sequential pulsing of precursors that undergo self-limited surface reactions. The self- limiting reactions and gas phase diffusion of the precursors together enable the conformal coating of microstructured particles with a high degree of thickness and compositional control. ALD may be used to deposit thin films that introduce new functionalities to a particle surface. Examples of new functionalities include: chemical reactivity, a mechanically strong protective coating, and an electrically resistive layer. The coatings properties are often dependent on the bulk properties and microstructure of the particle substrate, though they usually do not affect its bulk properties or microstructure. Particle ALD finds utility in the ability to synthesize well controlled, model systems, though it is expensive due to the need for costly metal precursors that are dangerous and require special handling. Enhanced properties due to ALD coating of particles in various applications are frequently described empirically, while the details of their enhancement mechanisms often remain the focus of ongoing research in the field. This study covers the various types of particle ALD and attempts to describe them from the unifying perspective of surface science.

  2. Atomic Layer Deposition to Enable the Production, Optimization and Protection of Spaceflight Hardware

    Data.gov (United States)

    National Aeronautics and Space Administration — Atomic Layer Deposition (ALD) a cost effective nano-manufacturing technique allows for the conformal coating of substrates with atomic control in a benign...

  3. Atomic Layer Deposition to Enable the Production, Optimization and Protection of Spaceflight Hardware Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Atomic Layer Deposition (ALD) a cost effective nano-manufacturing technique allows for the conformal coating of substrates with atomic control in a benign...

  4. Biexciton emission from single isoelectronic traps formed by nitrogen-nitrogen pairs in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Takamiya, Kengo; Fukushima, Toshiyuki; Yagi, Shuhei; Hijikata, Yasuto; Yaguchi, Hiroyuki [Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku , Saitama 338-8570 (Japan); Mochizuki, Toshimitsu; Yoshita, Masahiro; Akiyama, Hidefumi [Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Kuboya, Shigeyuki; Onabe, Kentaro [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Katayama, Ryuji [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2013-12-04

    We have studied photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in GaAs. Sharp emission lines due to exciton and biexciton were observed from individual isoelectronic traps in nitrogen atomic-layer doped (ALD) GaAs. The binding energy of biexciton bound to individual isoelectronic traps was approximately 8 meV. Both the exciton and biexciton luminescence lines show completely random polarization and no fine-structure splitting. These results are desirable to the application to the quantum cryptography used in the field of quantum information technology.

  5. Characterization of hafnium oxide resistive memory layers deposited on copper by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Briggs, B.D.; Bishop, S.M. [SUNY College of Nanoscale Science and Engineering, 255 Fuller Road, Albany, NY 12203 (United States); Leedy, K.D. [Air Force Research Laboratory, 2241 Avionics Circle, Wright Patterson Air Force Base, Dayton, OH 45433 (United States); Cady, N.C., E-mail: ncady@albany.edu [SUNY College of Nanoscale Science and Engineering, 255 Fuller Road, Albany, NY 12203 (United States)

    2014-07-01

    Hafnium oxide-based resistive memory devices have been fabricated on copper bottom electrodes. The HfO{sub x} active layers in these devices were deposited by atomic layer deposition (ALD) at 250 °C with tetrakis(dimethylamido)hafnium(IV) as the metal precursor and an O{sub 2} plasma as the reactant. Depth profiles of the HfO{sub x} by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a copper concentration on the order of five atomic percent throughout the HfO{sub x} film. In addition to the Cu doped HfO{sub x}, a thin layer (20 nm) of Cu{sub x}O is present at the surface. This surface layer is believed to have formed during the ALD process, and greatly complicates the analysis of the switching mechanism. The resistive memory structures fabricated from the ALD HfO{sub x} exhibited non-polar resistive switching, independent of the top metal electrode (Ni, Pt, Al, Au). Resistive switching current voltage (I–V) curves were analyzed using Schottky emission and ionic hopping models to gain insight into the physical mechanisms underpinning the device behavior. During the forming process it was determined that, at voltages in excess of 2.5 V, an ionic hopping model is in good agreement with the I–V data. The extracted ion hopping distance ∼ 4 Å was within the range of interatomic spacing of HfO{sub 2} during the forming process consistent with ionic motion of Cu{sup 2+} ions. Lastly the on state I–V data was dominated at larger voltages by Schottky emission with an estimated barrier height of ∼ 0.5 eV and a refractive index of 2.59. The consequence of the Schottky emission analysis indicates the on state resistance to be a product of a Pt/Cu{sub 2}O/Cu filament(s)/Cu{sub 2}O/Cu structure. - Highlights: • HfO{sub 2} was grown via atomic layer deposition at 250 and 100 °C on Cu substrates. • A Cu{sub 2}O surface layer and Cu doping were observed in post-deposition of HfO{sub 2}. • Resistive memory devices were fabricated and

  6. Visualization of arrangements of carbon atoms in graphene layers by Raman mapping and atomic-resolution TEM

    KAUST Repository

    Cong, Chunxiao; Li, Kun; Zhang, Xixiang; Yu, Ting

    2013-01-01

    In-plane and out-of-plane arrangements of carbon atoms in graphene layers play critical roles in the fundamental physics and practical applications of these novel two-dimensional materials. Here, we report initial results on the edge

  7. Formation process and superparamagnetic properties of (Mn,Ga)As nanocrystals in GaAs fabricated by annealing of (Ga,Mn)As layers with low Mn content

    DEFF Research Database (Denmark)

    Sadowski, Janusz; Domagala, Jaroslaw Z.; Mathieu, Roland

    2011-01-01

    °C) annealing of (Ga,Mn)As layers with Mn concentrations between 0.1% and 2%, grown by molecular beam epitaxy at 270°C. Decomposition of (Ga,Mn)As is already observed at the lowest annealing temperature of 400°C for layers with initial Mn content of 1% and 2%. Both cubic and hexagonal (Mn......,Ga)As nanocrystals, with similar diameters of 7-10 nm, are observed to coexist in layers with an initial Mn content of 0.5% and 2% after higher-temperature annealing. Measurements of magnetization relaxation in the time span 0.1-10 000 s provide evidence for superparamagnetic properties of the (Mn,Ga)As nanocrystals......X-ray diffraction, transmission electron microscopy, and magnetization measurements are employed to study the structural and magnetic properties of Mn-rich (Mn,Ga)As nanocrystals embedded in GaAs. These nanocomposites are obtained by moderate-temperature (400°C) and high-temperature (560°C and 630...

  8. Many-electron effect in the Si K-LL resonant Auger-electron spectroscopy spectra of the Si delta layer in GaAs

    International Nuclear Information System (INIS)

    Ohno, Masahide

    2006-01-01

    The Si K-LL resonant Auger-electron spectroscopy (RAES) spectra of silicon delta dopped layers in GaAs with very thin capping layers show both normal Auger decay and resonant Auger decay, when the core-level electron is excited to the conduction band. The resonant Auger peak kinetic energy (KE) shows no dispersion with photon energy, except when excited by the highest energy photons [M.D. Jackson, J.M.C. Thornton, D. Lewis, A. Robinson, M. Fahy, A. Aviary, P. Weightman, Phys. Rev. B71 (2005) 075313]. The RAES spectra are analyzed using a many-body theory. The presence of resonant Auger decay and no dispersion of resonant Auger peak KE with photon energy is explained in terms of the relaxation of a metastable excited core-hole state to a stable one on the time scale of core-hole decay. The excited electron in the conduction band either delocalizes rapidly leaving the ionized Si to decay by a normal Auger decay or drops to a state localized in the Si delta layer before the core-hole decays so that the RAES spectrum has both normal Auger decay and resonant Auger decay. As a result of the relaxation, the resonant Auger peak KE does not show any dispersion with photon energy. The variations with photon energy of the normal or resonant Auger peak intensity, KE, and width are explained in a consistent manner by a many-body theory

  9. Possibility of a quasi-liquid layer of As on GaAs substrate grown by MBE as observed by enhancement of Ga desorption at high As pressure

    Science.gov (United States)

    Asai, K.; Feng, J. M.; Vaccaro, P. O.; Fujita, K.; Ohachi, T.

    2000-06-01

    The As vapor pressure dependence of the Ga desorption rate during molecular beam epitaxy (MBE) growth on GaAs( n11)A ( n=1-4 hereafter) substrates was studied by photoluminescence (PL) measurements at 12 K for undoped AlGaAs/GaAs asymmetric double quantum wells (ADQWs). Reflection high energy electron diffraction (RHEED) oscillation measurements on a GaAs(100) surface were also used. Two K-cells of As solid sources (corresponding to beam equivalent pressures (BEPs) of 9.0×10 -6 and 4.5×10 -5 Torr) were used to change the As pressure rapidly. The Ga flux and substrate temperature were kept constant at 0.76 ML/s and 12 K, respectively, while the As flux changed from 7.6 (BEP 9.0×10 -6 Torr) to 32 ML/s (4.5×10 -5 Torr). With increasing As pressure, two separated PL peaks for the wide well (WW) of high index substrates were observed. This peak separation is attributed to a reduced well depth from an increasing Ga desorption rate. The energy differences of the PL peak depending on the off-angle from (111)A to (100) plane indicates an orientation-dependent Ga desorption rate. Moreover, amongst all ( n11)A and (100) planes, the Ga desorption rate was smallest from the (111)A surface. The increase of Ga desorption from the surface at high As pressures probably arose from an increasing coverage with a quasi-liquid layer (QLL).

  10. Recent progress of atomic layer deposition on polymeric materials

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hong Chen; Ye, Enyi [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634 (Singapore); Li, Zibiao, E-mail: lizb@imre.a-star.edu.sg [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634 (Singapore); Han, Ming-Yong [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634 (Singapore); Loh, Xian Jun, E-mail: lohxj@imre.a-star.edu.sg [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634 (Singapore); Department of Materials Science and Engineering, National University of Singapore, Singapore 117574 (Singapore); Singapore Eye Research Institute, 20 College Road, Singapore 169856 (Singapore)

    2017-01-01

    As a very promising surface coating technology, atomic layer deposition (ALD) can be used to modify the surfaces of polymeric materials for improving their functions and expanding their application areas. Polymeric materials vary in surface functional groups (number and type), surface morphology and internal structure, and thus ALD deposition conditions that typically work on a normal solid surface, usually do not work on a polymeric material surface. To date, a large variety of research has been carried out to investigate ALD deposition on various polymeric materials. This paper aims to provide an in-depth review of ALD deposition on polymeric materials and its applications. Through this review, we will provide a better understanding of surface chemistry and reaction mechanism for controlled surface modification of polymeric materials by ALD. The integrated knowledge can aid in devising an improved way in the reaction between reactant precursors and polymer functional groups/polymer backbones, which will in turn open new opportunities in processing ALD materials for better inorganic/organic film integration and potential applications. - Highlights: • ALD deposition on different natural and synthetic polymer materials • Reaction mechanism based on the surface functional groups of polymers • Application of ALD-modified polymers in different fields.

  11. Continuous production of nanostructured particles using spatial atomic layer deposition

    International Nuclear Information System (INIS)

    Ommen, J. Ruud van; Kooijman, Dirkjan; Niet, Mark de; Talebi, Mojgan; Goulas, Aristeidis

    2015-01-01

    In this paper, the authors demonstrate a novel spatial atomic layer deposition (ALD) process based on pneumatic transport of nanoparticle agglomerates. Nanoclusters of platinum (Pt) of ∼1 nm diameter are deposited onto titania (TiO 2 ) P25 nanoparticles resulting to a continuous production of an active photocatalyst (0.12–0.31 wt. % of Pt) at a rate of about 1 g min −1 . Tuning the precursor injection velocity (10–40 m s −1 ) enhances the contact between the precursor and the pneumatically transported support flows. Decreasing the chemisorption temperature (from 250 to 100 °C) results in more uniform distribution of the Pt nanoclusters as it decreases the reaction rate as compared to the rate of diffusion into the nanoparticle agglomerates. Utilizing this photocatalyst in the oxidation reaction of Acid Blue 9 showed a factor of five increase of the photocatalytic activity compared to the native P25 nanoparticles. The use of spatial particle ALD can be further expanded to deposition of nanoclusters on porous, micron-sized particles and to the production of core–shell nanoparticles enabling the robust and scalable manufacturing of nanostructured powders for catalysis and other applications

  12. Inductively coupled plasma nanoetching of atomic layer deposition alumina

    DEFF Research Database (Denmark)

    Han, Anpan; Chang, Bingdong; Todeschini, Matteo

    2018-01-01

    such as silicon dioxide, silicon nitride, and diamond. In this report, we systematically study nanoscale plasma etching of Al2O3 with electron beam lithography and deep UV resist masks. The gas composition and pressure were tuned for optimal etching, and redeposition conditions were mapped. With a BCl3 and Ar...... the resist profile angle. For Al2O3 patterned with deep UV lithography, the smallest structures were 220 nm. For electron beam lithography patterns, the smallest gratings were 18-nm-wide with 50-nm-pitch. Using alumina as a hard mask, we show aspect ratio of 7-10 for subsequent silicon plasma etching, and we......Al2O3 thin-film deposited by atomic layer deposition is an attractive plasma etch mask for Micro and Nano Electro-Mechanical Systems (MEMS and NEMS). 20-nm-thick Al2O3 mask enables through silicon wafer plasma etching. Al2O3 is also an excellent etch mask for other important MEMS materials...

  13. Robust, functional nanocrystal solids by infilling with atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yao; Gibbs, Markelle; Perkins, Craig L.; Tolentino, Jason; Zarghami, Mohammad H.; Bustamante, Jr., J.; Law, Matt

    2011-12-14

    Thin films of colloidal semiconductor nanocrystals (NCs) are inherently metatstable materials prone to oxidative and photothermal degradation driven by their large surface-to-volume ratios and high surface energies. The fabrication of practical electronic devices based on NC solids hinges on preventing oxidation, surface diffusion, ripening, sintering, and other unwanted physicochemical changes that can plague these materials. Here we use low-temperature atomic layer deposition (ALD) to infill conductive PbSe NC solids with metal oxides to produce inorganic nanocomposites in which the NCs are locked in place and protected against oxidative and photothermal damage. Infilling NC field-effect transistors and solar cells with amorphous alumina yields devices that operate with enhanced and stable performance for at least months in air. Furthermore, ALD infilling with ZnO lowers the height of the inter-NC tunnel barrier for electron transport, yielding PbSe NC films with electron mobilities of 1 cm² V-1 s-1. Our ALD technique is a versatile means to fabricate robust NC solids for optoelectronic devices.

  14. Deposition of yttrium oxysulfide thin films by atomic layer epitaxy

    International Nuclear Information System (INIS)

    Kukli, K.; University of Tartu, Tartu,; Johansson, L-S.; Nykaenen, E.; Peussa, M.; Ninistoe, L.

    1998-01-01

    Full text: Yttrium oxysulfide is a highly interesting material for optoelectronic applications. It is industrially exploited in the form of doped powder in catholuminescent phosphors, e.g. Y 2 O 2 S: Eu 3+ for colour TV. Attempts to grow thin films of Y 2 O 2 S have not been frequent and only partially successful due to the difficulties in obtaining crystalline films at a reasonable temperature. Furthermore, sputtering easily leads to a sulphur deficiency. Evaporation of the elements from a multi-source offers a better control of the stoichiometry resulting in hexagonal (0002) oriented films at 580 deg C. In this paper we present the first successful thin film growth experiments using a chemical process with molecular precursors. Atomic layer epitaxy (ALE) allows the use of a relatively low deposition temperature and thus compatibility with other technologies. Already at 425 deg C the reaction between H 2 S and Y(thd) 3 (thd = 2,2,6,6 - tetramethyl-heptane-3,5- dione) yields a crystalline Y 2 O 2 S thin film which was characterized by XRD, XRF and XPS

  15. Atomic Layer Deposition in Bio-Nanotechnology: A Brief Overview.

    Science.gov (United States)

    Bishal, Arghya K; Butt, Arman; Selvaraj, Sathees K; Joshi, Bela; Patel, Sweetu B; Huang, Su; Yang, Bin; Shukohfar, Tolou; Sukotjo, Cortino; Takoudis, Christos G

    2015-01-01

    Atomic layer deposition (ALD) is a technique increasingly used in nanotechnology and ultrathin film deposition; it is ideal for films in the nanometer and Angstrom length scales. ALD can effectively be used to modify the surface chemistry and functionalization of engineering-related and biologically important surfaces. It can also be used to alter the mechanical, electrical, chemical, and other properties of materials that are increasingly used in biomedical engineering and biological sciences. ALD is a relatively new technique for optimizing materials for use in bio-nanotechnology. Here, after a brief review of the more widely used modes of ALD and a few of its applications in biotechnology, selected results that show the potential of ALD in bio-nanotechnology are presented. ALD seems to be a promising means for tuning the hydrophilicity/hydrophobicity characteristics of biomedical surfaces, forming conformal ultrathin coatings with desirable properties on biomedical substrates with a high aspect ratio, tuning the antibacterial properties of substrate surfaces of interest, and yielding multifunctional biomaterials for medical implants and other devices.

  16. Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

    International Nuclear Information System (INIS)

    Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; Macco, Bart; Kessels, W. M.; Geissbuhler, Jonas; De Wolf, Stefaan; Ballif, Christophe

    2014-01-01

    We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing, between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection

  17. Multilayer self-organization of InGaAs quantum wires on GaAs surfaces

    International Nuclear Information System (INIS)

    Wang, Zhiming M.; Kunets, Vasyl P.; Xie, Yanze Z.; Schmidbauer, Martin; Dorogan, Vitaliy G.; Mazur, Yuriy I.; Salamo, Gregory J.

    2010-01-01

    Molecular-Beam Epitaxy growth of multiple In 0.4 Ga 0.6 As layers on GaAs (311)A and GaAs (331)A has been investigated by Atomic Force Microscopy and Photoluminescence. On GaAs (311)A, uniformly distributed In 0.4 Ga 0.6 As quantum wires (QWRs) with wider lateral separation were achieved, presenting a significant improvement in comparison with the result on single layer [H. Wen, Z.M. Wang, G.J. Salamo, Appl. Phys. Lett. 84 (2004) 1756]. On GaAs (331)A, In 0.4 Ga 0.6 As QWRs were revealed to be much straighter than in the previous report on multilayer growth [Z. Gong, Z. Niu, Z. Fang, Nanotechnology 17 (2006) 1140]. These observations are discussed in terms of the strain-field interaction among multilayers, enhancement of surface mobility at high temperature, and surface stability of GaAs (311)A and (331)A surfaces.

  18. Formation and reconstruction of Se nanoislands at the surface of thin epitaxial ZnSe layers grown on GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kozlovskiy, V. I.; Krivobok, V. S., E-mail: krivobok@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kuznetsov, P. I.; Nikolaev, S. N.; Onistchenko, E. E.; Pruchkina, A. A.; Temiryazev, A. G. [Russian Academy of Sciences, Kotel’nikov Institute of Radio-Engineering and Electronics (Russian Federation)

    2016-05-15

    Strained epitaxial ZnSe layers are grown on GaAs substrates by the method of vapor-phase epitaxy from metal-organic compounds. It is found that Se nanoislands with a density of 10{sup 8} to 10{sup 9} cm{sup –2} are formed at the surface of such layers. It is established that an increase in the size of Se islands and a decrease in their density take place after completion of growth. Annealing in a H{sub 2} atmosphere at a temperature higher than 260°C leads to the disappearance of Se islands and to a decrease in the surface roughness. It is shown that annealing does not lead to deterioration of the structural perfection of the epitaxial ZnSe films; rather, annealing gives rise to a decrease in the intensity of impurity–defect luminescence and to an increase in the intensity of intrinsic radiation near the bottom of the exciton band.

  19. Pinning-free GaAs MIS structures with Si interface control layers formed on (4 x 6) reconstructed (0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Anantathanasarn, Sanguan; Hasegawa, Hideki

    2003-06-30

    (0 0 1)-Oriented GaAs metal-insulator-semiconductor (MIS) structures having a silicon interface control layer (Si ICL) were fabricated on surfaces having Ga-rich (4x6) reconstructions. Si ICL was grown by molecular beam epitaxy. MIS structures were fabricated by partially converting Si ICL to SiN{sub x} by direct nitridation, and further depositing a thick SiO{sub 2} layer on top as the main passivation dielectric by plasma-assisted chemical vapor deposition. Reflection high-energy electron diffraction, in situ X-ray photoelectron spectroscopy and MIS capacitance-voltage (C-V) techniques were used for characterization. The initial surface reconstruction was found to have a surprisingly strong effect on the degree of Fermi level pinning at the MIS interface. In contrast to the standard As-rich (2x4) surface, which results in strongly pinned MIS interfaces, the novel SiO{sub 2}/SiN{sub x}/Si ICL/GaAs MIS structures formed on ''genuine'' (4x6) surface realized complete unpinning of Fermi level over the entire band gap with a minimum interface state density of 4x10{sup 10} cm{sup -2} eV{sup -1} range.

  20. Visible-light electroluminescence in Mn-doped GaAs light-emitting diodes

    International Nuclear Information System (INIS)

    Nam Hai, Pham; Maruo, Daiki; Tanaka, Masaaki

    2014-01-01

    We observed visible-light electroluminescence (EL) due to d-d transitions in light-emitting diodes with Mn-doped GaAs layers (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show two peaks at 1.89 eV and 2.16 eV, which are exactly the same as 4 A 2 ( 4 F) → 4 T 1 ( 4 G) and 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transitions of Mn atoms doped in ZnS. The temperature dependence and the current-density dependence are consistent with the characteristics of d-d transitions. We explain the observed EL spectra by the p-d hybridized orbitals of the Mn d electrons in GaAs

  1. Atomic layer deposition on nanoparticles in a rotary reactor

    Science.gov (United States)

    McCormick, Jarod Alan

    Challenges are encountered during atomic layer deposition (ALD) on large quantities of nanoparticles. The particles must be agitated or vigorously mixed to perform the ALD surface reactions in reasonable times and to prevent the particles from being agglomerated by the ALD film. The high surface area of nanoparticles also demands efficient reactant usage because large quantities of reactant are required for the surface reactions to reach completion. To address these challenges, a novel rotary reactor was developed to achieve constant particle agitation during static ALD reactant exposures. In the design of this new reactor, a cylindrical drum with porous metal walls was positioned inside a vacuum chamber. The porous cylindrical drum was rotated by a magnetically coupled rotary feedthrough. By rotating the cylindrical drum to obtain a centrifugal force of less than one gravitational force, the particles were agitated by a continuous "avalanche" of particles. The effectiveness of this rotary reactor was demonstrated by Al 2O3 ALD on ZrO2 particles. A number of techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, scanning Auger spectroscopy and x-ray photoelectron spectroscopy confirmed that the Al2O3 ALD film conformally coats the ZrO 2 particles. Combining static reactant exposures with a very high surface area sample in the rotary reactor also provides unique opportunities for studying the surface chemistry during ALD. Sequential, subsaturating doses can be used to examine the self-limiting behavior of the ALD reactions in the rotary reactor. This dosing method is the first demonstration of self-limiting ALD on bulk quantities of nanoparticles. By combining these sequential, subsaturating doses with quadrupole mass spectrometry, ALD reactions can be analyzed from the gas phase using full mass spectrum analysis. The reaction products are present in a high enough concentration to discern a gas phase mechanism for reactions

  2. Terahertz radiation in In{sub 0.38}Ga{sub 0.62}As grown on a GaAs wafer with a metamorphic buffer layer under femtosecond laser excitation

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, D. S., E-mail: ponomarev-dmitr@mail.ru; Khabibullin, R. A.; Yachmenev, A. E.; Maltsev, P. P. [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation); Grekhov, M. M. [National Research Nuclear University “MEPhI” (Russian Federation); Ilyakov, I. E.; Shishkin, B. V.; Akhmedzhanov, R. A. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2017-04-15

    The results of time-domain spectroscopy of the terahertz (THz) generation in a structure with an In{sub 0.38}Ga{sub 0.62}As photoconductive layer are presented. This structure grown by molecular-beam epitaxy on a GaAs substrate using a metamorphic buffer layer allows THz generation with a wide frequency spectrum (to 6 THz). This is due to the additional contribution of the photo-Dember effect to THz generation. The measured optical-to-terahertz conversion efficiency in this structure is 10{sup –5} at a rather low optical fluence of ~40 μJ/cm{sup 2}, which is higher than that in low-temperature grown GaAs by almost two orders of magnitude.

  3. Area-selective atomic layer deposition of platinum using photosensitive polyimide

    NARCIS (Netherlands)

    Vervuurt, R.H.J.; Sharma, A.; Jiao, Y.; Kessels, W.M.M.; Bol, A.A.

    2016-01-01

    Area-selective atomic layer deposition (AS-ALD) of platinum (Pt) was studied using photosensitive polyimide as a masking layer. The polyimide films were prepared by spin-coating and patterned using photolithography. AS-ALD of Pt using poly(methyl-methacrylate) (PMMA) masking layers was used as a

  4. Reducing interface recombination for Cu(In,Ga)Se{sub 2} by atomic layer deposited buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Hultqvist, Adam; Bent, Stacey F. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States); Li, Jian V.; Kuciauskas, Darius; Dippo, Patricia; Contreras, Miguel A.; Levi, Dean H. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    2015-07-20

    Partial CuInGaSe{sub 2} (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnO{sub x} buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II–VI systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.

  5. Visualization of arrangements of carbon atoms in graphene layers by Raman mapping and atomic-resolution TEM

    KAUST Repository

    Cong, Chunxiao

    2013-02-01

    In-plane and out-of-plane arrangements of carbon atoms in graphene layers play critical roles in the fundamental physics and practical applications of these novel two-dimensional materials. Here, we report initial results on the edge/crystal orientations and stacking orders of bi-and tri-layer graphene (BLG and TLG) from Raman spectroscopy and transmission electron microscopy (TEM) experiments performed on the same sample. We introduce a new method of transferring graphene flakes onto a normal TEM grid. Using this novel method, we probed the BLG and TLG flakes that had been previously investigated by Raman scattering with high-resolution (atomic) TEM.

  6. GaSb and GaSb/AlSb Superlattice Buffer Layers for High-Quality Photodiodes Grown on Commercial GaAs and Si Substrates

    Science.gov (United States)

    Gutiérrez, M.; Lloret, F.; Jurczak, P.; Wu, J.; Liu, H. Y.; Araújo, D.

    2018-05-01

    The objective of this work is the integration of InGaAs/GaSb/GaAs heterostructures, with high indium content, on GaAs and Si commercial wafers. The design of an interfacial misfit dislocation array, either on GaAs or Si substrates, allowed growth of strain-free devices. The growth of purposely designed superlattices with their active region free of extended defects on both GaAs and Si substrates is demonstrated. Transmission electron microscopy technique is used for the structural characterization and plastic relaxation study. In the first case, on GaAs substrates, the presence of dopants was demonstrated to reduce several times the threading dislocation density through a strain-hardening mechanism avoiding dislocation interactions, while in the second case, on Si substrates, similar reduction of dislocation interactions is obtained using an AlSb/GaSb superlattice. The latter is shown to redistribute spatially the interfacial misfit dislocation array to reduce dislocation interactions.

  7. Conduction mechanisms in thin atomic layer deposited Al2O3 layers

    International Nuclear Information System (INIS)

    Spahr, Holger; Montzka, Sebastian; Reinker, Johannes; Hirschberg, Felix; Kowalsky, Wolfgang; Johannes, Hans-Hermann

    2013-01-01

    Thin Al 2 O 3 layers of 2–135 nm thickness deposited by thermal atomic layer deposition at 80 °C were characterized regarding the current limiting mechanisms by increasing voltage ramp stress. By analyzing the j(U)-characteristics regarding ohmic injection, space charge limited current (SCLC), Schottky-emission, Fowler-Nordheim-tunneling, and Poole-Frenkel-emission, the limiting mechanisms were identified. This was performed by rearranging and plotting the data in a linear scale, such as Schottky-plot, Poole-Frenkel-plot, and Fowler-Nordheim-plot. Linear regression then was applied to the data to extract the values of relative permittivity from Schottky-plot slope and Poole-Frenkel-plot slope. From Fowler-Nordheim-plot slope, the Fowler-Nordheim-energy-barrier was extracted. Example measurements in addition to a statistical overview of the results of all investigated samples are provided. Linear regression was applied to the region of the data that matches the realistic values most. It is concluded that ohmic injection and therefore SCLC only occurs at thicknesses below 12 nm and that the Poole-Frenkel-effect is no significant current limiting process. The extracted Fowler-Nordheim-barriers vary in the range of up to approximately 4 eV but do not show a specific trend. It is discussed whether the negative slope in the Fowler-Nordheim-plot could in some cases be a misinterpreted trap filled limit in the case of space charge limited current

  8. Formation of columnar (In,Ga)As quantum dots on GaAs(100)

    International Nuclear Information System (INIS)

    He, J.; Noetzel, R.; Offermans, P.; Koenraad, P.M.; Gong, Q.; Hamhuis, G.J.; Eijkemans, T.J.; Wolter, J.H.

    2004-01-01

    Columnar (In,Ga)As quantum dots (QDs) with homogeneous composition and shape in the growth direction are realized by molecular-beam epitaxy on GaAs(100) substrates. The columnar (In,Ga)As QDs are formed on InAs seed QDs by alternating deposition of thin GaAs intermediate layers and monolayers of InAs with extended growth interruptions after each layer. The height of the columnar (In,Ga)As QDs is controlled by varying the number of stacked GaAs/InAs layers. The structural and optical properties are studied by cross-sectional scanning tunneling microscopy, atomic force microscopy, and photoluminescence spectroscopy. With increase of the aspect ratio of the columnar QDs, the emission wavelength is redshifted and the linewidth is reduced

  9. Atomic Layer Deposition on Carbon Nanotubes and their Assemblies

    Science.gov (United States)

    Stano, Kelly Lynn

    Global issues related to energy and the environment have motivated development of advanced material solutions outside of traditional metals ceramics, and polymers. Taking inspiration from composites, where the combination of two or more materials often yields superior properties, the field of organic-inorganic hybrids has recently emerged. Carbon nanotube (CNT)-inorganic hybrids have drawn widespread and increasing interest in recent years due to their multifunctionality and potential impact across several technologically important application areas. Before the impacts of CNT-inorganic hybrids can be realized however, processing techniques must be developed for their scalable production. Optimization in chemical vapor deposition (CVD) methods for synthesis of CNTs and vertically aligned CNT arrays has created production routes both high throughput and economically feasible. Additionally, control of CVD parameters has allowed for growth of CNT arrays that are able to be drawn into aligned sheets and further processed to form a variety of aligned 1, 2, and 3-dimensional bulk assemblies including ribbons, yarns, and foams. To date, there have only been a few studies on utilizing these bulk assemblies for the production of CNT-inorganic hybrids. Wet chemical methods traditionally used for fabricating CNT-inorganic hybrids are largely incompatible with CNT assemblies, since wetting and drying the delicate structures with solvents can destroy their structure. It is therefore necessary to investigate alternative processing strategies in order to advance the field of CNT-inorganic hybrids. In this dissertation, atomic layer deposition (ALD) is evaluated as a synthetic route for the production of large-scale CNT-metal oxide hybrids as well as pure metal oxide architectures utilizing CNT arrays, ribbons, and ultralow density foams as deposition templates. Nucleation and growth behavior of alumina was evaluated as a function of CNT surface chemistry. While highly graphitic

  10. Atomic Layer Control of Thin Film Growth Using Binary Reaction Sequence Chemistry

    National Research Council Canada - National Science Library

    George, Steven

    1997-01-01

    Our research is focusing on the atomic layer control of thin film growth. Our goal is to deposit films with precise control of thickness and conformality on both flat and high aspect ratio structures...

  11. Effect of substrate composition on atomic layer deposition using self-assembled monolayers as blocking layers

    International Nuclear Information System (INIS)

    Zhang, Wenyu; Engstrom, James R.

    2016-01-01

    The authors have examined the effect of two molecules that form self-assembled monolayers (SAMs) on the subsequent growth of TaN x by atomic layer deposition (ALD) on two substrate surfaces, SiO 2 and Cu. The SAMs that the authors have investigated include two vapor phase deposited, fluorinated alkyl silanes: Cl 3 Si(CH 2 ) 2 (CF 2 ) 5 CF 3 (FOTS) and (C 2 H 5 O) 3 Si(CH 2 ) 2 (CF 2 ) 7 CF 3 (HDFTEOS). Both the SAMs themselves and the TaN x thin films, grown using Ta[N(CH 3 ) 2 ] 5 and NH 3 , were analyzed ex situ using contact angle, spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and low energy ion-scattering spectroscopy (LEISS). First, the authors find that both SAMs on SiO 2 are nominally stable at T s  ∼ 300 °C, the substrate temperature used for ALD, while on Cu, the authors find that HDFTEOS thermally desorbs, while FOTS is retained on the surface. The latter result reflects the difference in the head groups of these two molecules. The authors find that both SAMs strongly attenuate the ALD growth of TaN x on SiO 2 , by about a factor of 10, while on Cu, the SAMs have no effect on ALD growth. Results from LEISS and XPS are decisive in determining the nature of the mechanism of growth of TaN x on all surfaces. Growth on SiO 2 is 2D and approximately layer-by-layer, while on the surfaces terminated by the SAMs, it nucleates at defect sites, is islanded, and is 3D. In the latter case, our results support growth of the TaN x thin film over the SAM, with a considerable delay in formation of a continuous thin film. Growth on Cu, with or without the SAMs, is also 3D and islanded, and there is also a delay in the formation of a continuous thin film as compared to growth on SiO 2 . These results highlight the power of coupling measurements from both LEISS and XPS in examinations of ultrathin films formed by ALD

  12. Nano-scale patterning on sulfur terminated GaAs (0 0 1) surface by scanning tunneling microscope

    International Nuclear Information System (INIS)

    Yagishita, Yuki; Toda, Yusuke; Hirai, Masakazu; Fujishiro, Hiroki Inomata

    2004-01-01

    We perform nano-scale patterning on a sulfur (S) terminated GaAs (0 0 1) surface by a scanning tunneling microscope (STM) in ultra-high vacuum (UHV). A multi-layer of S deposited by using (NH 4 ) 2 S x solution is changed to a mono-layer after annealing at 560 deg. C for 15 h, which terminates the GaAs (0 0 1) surface. Groove structures with about 0.23 nm in depth and about 5 nm in width are patterned successfully on the S-terminated surface. We investigate dependences of both depth and width of the patterned groove on the tunneling current and the scanning speed of tip. It is observed that topmost S atoms are extracted together with first-layer Ga atoms, because of the larger binding energy of S-Ga bond

  13. Atomic layer deposition of epitaxial layers of anatase on strontium titanate single crystals: Morphological and photoelectrochemical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, Theodore J.; Nepomnyashchii, Alexander B.; Parkinson, B. A., E-mail: bparkin1@uwyo.edu [Department of Chemistry, School of Energy Resources, University of Wyoming, Laramie, Wyoming 82071 (United States)

    2015-01-15

    Atomic layer deposition was used to grow epitaxial layers of anatase (001) TiO{sub 2} on the surface of SrTiO{sub 3} (100) crystals with a 3% lattice mismatch. The epilayers grow as anatase (001) as confirmed by x-ray diffraction. Atomic force microscope images of deposited films showed epitaxial layer-by-layer growth up to about 10 nm, whereas thicker films, of up to 32 nm, revealed the formation of 2–5 nm anatase nanocrystallites oriented in the (001) direction. The anatase epilayers were used as substrates for dye sensitization. The as received strontium titanate crystal was not sensitized with a ruthenium-based dye (N3) or a thiacyanine dye (G15); however, photocurrent from excited state electron injection from these dyes was observed when adsorbed on the anatase epilayers. These results show that highly ordered anatase surfaces can be grown on an easily obtained substrate crystal.

  14. Plasma enhanced atomic layer deposited MoOx emitters for silicon heterojunction solar cells

    OpenAIRE

    Ziegler, J.; Mews, M.; Kaufmann, K.; Schneider, T.; Sprafke, A.N.; Korte, L.; Wehrsporn, R.B

    2015-01-01

    A method for the deposition of molybdenum oxide MoOx with high growth rates at temperatures below 200 C based on plasma enhanced atomic layer deposition is presented. The stoichiometry of the overstoichiometric MoOx films can be adjusted by the plasma parameters. First results of these layers acting as hole selective contacts in silicon heterojunction solar cells are presented and discussed

  15. Atomic-layer-resolved analysis of surface magnetism by diffraction spectroscopy

    International Nuclear Information System (INIS)

    Matsui, Fumihiko; Matsushita, Tomohiro; Daimon, Hiroshi

    2010-01-01

    X-ray absorption near edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) measurements by Auger-electron-yield detection are powerful analysis tools for the electronic and magnetic structures of surfaces, but all the information from atoms within the electron mean-free-path range is summed into the obtained spectrum. In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, diffraction spectroscopy, which is the combination of X-ray absorption spectroscopy and Auger electron diffraction (AED). From a series of measured thickness dependent AED patterns, we deduced a set of atomic-layer-specific AED patterns arithmetically. Based on these AED patterns, we succeeded in disentangling obtained XANES and XMCD spectra into those from different atomic layers.

  16. Modeling of atomic layer deposition on nanoparticle agglomerates

    NARCIS (Netherlands)

    Jin, W.

    2017-01-01

    Nanoparticles are increasingly applied in a range of fields, such as electronics, catalysis, energy and medicine, due to their small sizes and consequent high surface-volume ratio. In many applications, it is attractive to coat the nanoparticles with a layer of different materials in order to gain

  17. Silicon protected with atomic layer deposited TiO2

    DEFF Research Database (Denmark)

    Seger, Brian; Tilley, S. David; Pedersen, Thomas

    2013-01-01

    The present work demonstrates that tuning the donor density of protective TiO2 layers on a photocathode has dramatic consequences for electronic conduction through TiO2 with implications for the stabilization of oxidation-sensitive catalysts on the surface. Vacuum annealing at 400 °C for 1 hour o...

  18. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

    Science.gov (United States)

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2016-01-07

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.

  19. Modified energetics and growth kinetics on H-terminated GaAs (110)

    International Nuclear Information System (INIS)

    Galiana, B.; Benedicto, M.; Díez-Merino, L.; Tejedor, P.; Lorbek, S.; Hlawacek, G.; Teichert, C.

    2013-01-01

    Atomic hydrogen modification of the surface energy of GaAs (110) epilayers, grown at high temperatures from molecular beams of Ga and As 4 , has been investigated by friction force microscopy (FFM). The reduction of the friction force observed with longer exposures to the H beam has been correlated with the lowering of the surface energy originated by the progressive de-relaxation of the GaAs (110) surface occurring upon H chemisorption. Our results indicate that the H-terminated GaAs (110) epilayers are more stable than the As-stabilized ones, with the minimum surface energy value of 31 meV/Å 2 measured for the fully hydrogenated surface. A significant reduction of the Ga diffusion length on the H-terminated surface irrespective of H coverage has been calculated from the FFM data, consistent with the layer-by-layer growth mode and the greater As incorporation coefficient determined from real-time reflection high-energy electron diffraction studies. Arsenic incorporation through direct dissociative chemisorption of single As 4 molecules mediated by H on the GaAs (110) surface has been proposed as the most likely explanation for the changes in surface kinetics observed

  20. Modified energetics and growth kinetics on H-terminated GaAs (110)

    Energy Technology Data Exchange (ETDEWEB)

    Galiana, B. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Departamento de Física, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Madrid (Spain); Benedicto, M.; Díez-Merino, L.; Tejedor, P. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Lorbek, S.; Hlawacek, G.; Teichert, C. [Institut für Physik, Montanuniversität Leoben, Franz Josef St., 18A-8700 Leoben (Austria)

    2013-10-28

    Atomic hydrogen modification of the surface energy of GaAs (110) epilayers, grown at high temperatures from molecular beams of Ga and As{sub 4}, has been investigated by friction force microscopy (FFM). The reduction of the friction force observed with longer exposures to the H beam has been correlated with the lowering of the surface energy originated by the progressive de-relaxation of the GaAs (110) surface occurring upon H chemisorption. Our results indicate that the H-terminated GaAs (110) epilayers are more stable than the As-stabilized ones, with the minimum surface energy value of 31 meV/Å{sup 2} measured for the fully hydrogenated surface. A significant reduction of the Ga diffusion length on the H-terminated surface irrespective of H coverage has been calculated from the FFM data, consistent with the layer-by-layer growth mode and the greater As incorporation coefficient determined from real-time reflection high-energy electron diffraction studies. Arsenic incorporation through direct dissociative chemisorption of single As{sub 4} molecules mediated by H on the GaAs (110) surface has been proposed as the most likely explanation for the changes in surface kinetics observed.

  1. Magnetic dichroism in photoemission: a new element-specific magnetometer with atomic-layer resolution

    International Nuclear Information System (INIS)

    Starke, K.; Arenholz, E.; Kaindl, G.

    1998-01-01

    Full text: Magnetic coupling in layered metallic structures has become a key issue in thin-film magnetism since the observation of oscillatory exchange coupling across non-ferromagnetic spacer layers. Although this phenomenon was discovered in rare earths (RE) superlattices, mostly transition-metal systems have been studied and are now applied in data-storage industry. An understanding of the coupling mechanisms has been reached after a fabrication of high-quality interfaces became possible. It allowed, in particular, the experimental finding of induced ferromagnetic order in 'nonmagnetic' atomic layers near an interface, using element-specific probes such as magnetic circular dichroism in x-ray absorption. - In layered RE systems, by contrast, the well known intermiscibility has prevented a preparation of atomically sharp interfaces, and all RE superlattices studied so far showed interdiffusion zones of several atomic layers. In the present overview, we report the first fabrication of atomically flat heteromagnetic RE interfaces, their structural characterization and their magnetic analysis using magnetic dichroism in photoemission (MDPE). This new tool gives access to the magnetization of individual atomic layers near interfaces in favourite cases. Merits of MDPE as a magnetometer are demonstrated at the example of Eu/Gd(0001), where chemical shifts of core-level photoemission lines allow to spectroscopically separate up to four different atomic layers. The high surface sensitivity of MDPE, together with the well known dependence of the core-level binding energies on the coordination number of the photo emitting atom, opens the door to future site-specific studies of magnetism in sub-monolayer systems such as 'nanowires'

  2. Implementation of atomic layer etching of silicon: Scaling parameters, feasibility, and profile control

    Energy Technology Data Exchange (ETDEWEB)

    Ranjan, Alok, E-mail: alok.ranjan@us.tel.com; Wang, Mingmei; Sherpa, Sonam D.; Rastogi, Vinayak [TEL Technology Center, America LLC, 255 Fuller Road, Suite 214, Albany, New York 12203 (United States); Koshiishi, Akira [Tokyo Electron Miyagi, Ltd., 1 Techno-Hills, Taiwa-cho, Kurokawa-gun, Miyagi, 9813629 (Japan); Ventzek, Peter L. G. [Tokyo Electron America, Inc., 2400 Grove Blvd., Austin, Texas 78741 (United States)

    2016-05-15

    Atomic or layer by layer etching of silicon exploits temporally segregated self-limiting adsorption and material removal steps to mitigate the problems associated with continuous or quasicontinuous (pulsed) plasma processes: selectivity loss, damage, and profile control. Successful implementation of atomic layer etching requires careful choice of the plasma parameters for adsorption and desorption steps. This paper illustrates how process parameters can be arrived at through basic scaling exercises, modeling and simulation, and fundamental experimental tests of their predictions. Using chlorine and argon plasma in a radial line slot antenna plasma source as a platform, the authors illustrate how cycle time, ion energy, and radical to ion ratio can be manipulated to manage the deviation from ideality when cycle times are shortened or purges are incomplete. Cell based Monte Carlo feature scale modeling is used to illustrate profile outcomes. Experimental results of atomic layer etching processes are illustrated on silicon line and space structures such that iso-dense bias and aspect ratio dependent free profiles are produced. Experimental results also illustrate the profile control margin as processes move from atomic layer to multilayer by layer etching. The consequence of not controlling contamination (e.g., oxygen) is shown to result in deposition and roughness generation.

  3. Subnanometer Ga 2 O 3 Tunnelling Layer by Atomic Layer Deposition to Achieve 1.1 V Open-Circuit Potential in Dye-Sensitized Solar Cells

    KAUST Repository

    Chandiran, Aravind Kumar; Tetreault, Nicolas; Humphry-Baker, Robin; Kessler, Florian; Baranoff, Etienne; Yi, Chenyi; Nazeeruddin, Mohammad Khaja; Grä tzel, Michael

    2012-01-01

    Herein, we present the first use of a gallium oxide tunnelling layer to significantly reduce electron recombination in dye-sensitized solar cells (DSC). The subnanometer coating is achieved using atomic layer deposition (ALD) and leading to a new

  4. Atomic Layer Deposition Alumina-Passivated Silicon Nanowires: Probing the Transition from Electrochemical Double-Layer Capacitor to Electrolytic Capacitor.

    Science.gov (United States)

    Gaboriau, Dorian; Boniface, Maxime; Valero, Anthony; Aldakov, Dmitry; Brousse, Thierry; Gentile, Pascal; Sadki, Said

    2017-04-19

    Silicon nanowires were coated by a 1-5 nm thin alumina layer by atomic layer deposition (ALD) in order to replace poorly reproducible and unstable native silicon oxide by a highly conformal passivating alumina layer. The surface coating enabled probing the behavior of symmetric devices using such electrodes in the EMI-TFSI electrolyte, allowing us to attain a large cell voltage up to 6 V in ionic liquid, together with very high cyclability with less than 4% capacitance fade after 10 6 charge/discharge cycles. These results yielded fruitful insights into the transition between an electrochemical double-layer capacitor behavior and an electrolytic capacitor behavior. Ultimately, thin ALD dielectric coatings can be used to obtain hybrid devices exhibiting large cell voltage and excellent cycle life of dielectric capacitors, while retaining energy and power densities close to the ones displayed by supercapacitors.

  5. Young Investigator Proposal, Research Area 7.4 Reactive Chemical Systems: Multifunctional, Bimetallic Nanomaterials Prepared by Atomic Layer Electroless Deposition

    Science.gov (United States)

    2017-09-30

    Report: Young Investigator Proposal, Research Area 7.4 Reactive Chemical Systems: Multifunctional, Bimetallic Nanomaterials Prepared by Atomic Layer ...Chemical Systems: Multifunctional, Bimetallic Nanomaterials Prepared by Atomic Layer Electroless Deposition Report Term: 0-Other Email: pcappillino... Layer Electroless Deposition (ALED, Figure 1) is the ability to tune growth mechanism, hence growth morphology, by altering conditions. In this

  6. Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

    Science.gov (United States)

    Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

    2017-09-13

    Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

  7. Science and Emerging Technology of 2D Atomic Layered Materials and Devices

    Science.gov (United States)

    2017-09-09

    AFRL-AFOSR-JP-TR-2017-0067 Science & Emerging Technology of 2D Atomic Layered Materials and Devices Angel Rubio UNIVERSIDAD DEL PAIS VASCO - EUSKAL...DD-MM-YYYY)      27-09-2017 2.  REPORT TYPE      Final 3.  DATES COVERED (From - To)      19 Feb 2015 to 18 Feb 2017 4.  TITLE AND SUBTITLE Science ...reporting documents for AOARD project 144088, “2D Materials and Devices Beyond Graphene Science & Emerging Technology of 2D Atomic Layered Materials and

  8. Metal-Insulator-Metal Single Electron Transistors with Tunnel Barriers Prepared by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Golnaz Karbasian

    2017-03-01

    Full Text Available Single electron transistors are nanoscale electron devices that require thin, high-quality tunnel barriers to operate and have potential applications in sensing, metrology and beyond-CMOS computing schemes. Given that atomic layer deposition is used to form CMOS gate stacks with low trap densities and excellent thickness control, it is well-suited as a technique to form a variety of tunnel barriers. This work is a review of our recent research on atomic layer deposition and post-fabrication treatments to fabricate metallic single electron transistors with a variety of metals and dielectrics.

  9. Atomistics of Ge deposition on Si(100) by atomic layer epitaxy.

    Science.gov (United States)

    Lin, D S; Wu, J L; Pan, S Y; Chiang, T C

    2003-01-31

    Chlorine termination of mixed Ge/Si(100) surfaces substantially enhances the contrast between Ge and Si sites in scanning tunneling microscopy observations. This finding enables a detailed investigation of the spatial distribution of Ge atoms deposited on Si(100) by atomic layer epitaxy. The results are corroborated by photoemission measurements aided by an unusually large chemical shift between Cl adsorbed on Si and Ge. Adsorbate-substrate atomic exchange during growth is shown to be important. The resulting interface is thus graded, but characterized by a very short length scale of about one monolayer.

  10. Atomic emission spectroscopic investigations for determining depth profiles at boride layers on iron materials

    International Nuclear Information System (INIS)

    Danzer, K.; Marx, G.

    1980-01-01

    A combination of atomic emission spectroscopic surface analysis and mechanical removement of defined surface areas in layers by grinding yields information about the depth distribution of boron in iron. In addition, the evaluation with the aid of the two-dimensional variance analysis leads to statements on the homogeneous distribution within individual layers at different depth. The results obtained in this way are in agreement with those of other methods

  11. Antireflective conducting nanostructures with an atomic layer deposited an AlZnO layer on a transparent substrate

    International Nuclear Information System (INIS)

    Park, Hyun-Woo; Ji, Seungmuk; Herdini, Diptya Suci; Lim, Hyuneui; Park, Jin-Seong; Chung, Kwun-Bum

    2015-01-01

    Graphical abstract: - Highlights: • We investigated the antireflective conducting nanostructures on a transparent substrate using atomic layer deposited AlZnO films. • The conformal AlZnO layer on a transparent nanostructured substrate exhibited 5.52 × 10 −4 Ω cm in resistivity and 88% in average visible transmittance. • The improvement of transparency was explained by the gradual changes of the refractive index in the film depth direction. • The decrease in electrical resistivity is strongly correlated to the increased surface area with the nanostructure and the change of chemical bonding states. - Abstract: The antireflective conducting nanostructures on a transparent substrate were shown to have enhanced optical and electrical properties via colloidal lithography and atomic layer deposition. The conformal AlZnO layer on a transparent nanostructured substrate exhibited 5.52 × 10 −4 Ω cm in resistivity and 88% in average visible transmittance, both of which were superior to those of a flat transparent conducting substrate. The improvement of transparency was explained by the gradual changes of the refractive index in the film depth direction. The decrease in electrical resistivity is strongly correlated to the increased surface area with the nanostructure and the change of chemical bonding states.

  12. Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers

    Energy Technology Data Exchange (ETDEWEB)

    Puttaswamy, Manjunath; Vehkamäki, Marko [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Kukli, Kaupo, E-mail: kaupo.kukli@helsinki.fi [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); University of Tartu, Institute of Physics, W. Ostwald 1, EE-50411 Tartu (Estonia); Dimri, Mukesh Chandra [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Kemell, Marianna; Hatanpää, Timo; Heikkilä, Mikko J. [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki (Finland); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Ritala, Mikko; Leskelä, Markku [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland)

    2016-07-29

    Bismuth iron oxide films with varying contributions from Fe{sub 2}O{sub 3} or Bi{sub 2}O{sub 3} were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} layers. Films grown at 140 °C to the thickness of 200–220 nm were amorphous, but crystallized upon post-deposition annealing at 500 °C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5 μC/cm{sup 2} and magnetic coercivity varying from a few up to 8000 A/m. - Highlights: • Bismuth iron oxide thin films were grown by atomic layer deposition at 140 °C. • The major phase formed in the films upon annealing at 500 °C was BiFeO{sub 3}. • BiFeO{sub 3} films and films containing excess Bi favored electrical charge polarization. • Slight excess of iron oxide enhanced saturative magnetization behavior.

  13. Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers

    Energy Technology Data Exchange (ETDEWEB)

    Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Ghent (Belgium); Schaekers, Marc [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Blasco, Nicolas [Air Liquide Electronics US, L.P., 46401 Landing Parkway, Fremont, California 94538 (United States)

    2013-03-18

    Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH{sub 3} plasma at deposition temperatures between 70 Degree-Sign C and 150 Degree-Sign C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the {delta}-VN crystal structure. The resistivity was as low as 200 {mu}{Omega} cm for the as deposited films and further reduced to 143 {mu}{Omega} cm and 93 {mu}{Omega} cm by annealing in N{sub 2} and H{sub 2}/He/N{sub 2}, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 Degree-Sign C.

  14. Enhanced electrical properties of dual-layer channel ZnO thin film transistors prepared by atomic layer deposition

    Science.gov (United States)

    Li, Huijin; Han, Dedong; Dong, Junchen; Yu, Wen; Liang, Yi; Luo, Zhen; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2018-05-01

    The thin film transistors (TFTs) with a dual-layer channel structure combing ZnO thin layer grown at 200 °C and ZnO film grown at 120 °C by atomic layer deposition are fabricated. The dual-layer channel TFT exhibits a low leakage current of 2.8 × 10-13 A, Ion/Ioff ratio of 3.4 × 109, saturation mobility μsat of 12 cm2 V-1 s-1, subthreshold swing (SS) of 0.25 V/decade. The SS value decreases to 0.18 V/decade after the annealing treatment in O2 due to the reduction of the trap states at the channel/dielectric interface and in the bulk channel layer. The enhanced performance obtained from the dual-layer channel TFTs is due to the ability of maintaining high mobility and suppressing the increase in the off-current at the same time.

  15. Patterned deposition by atmospheric pressure plasma-enhanced spatial atomic layer deposition

    NARCIS (Netherlands)

    Poodt, P.; Kniknie, B.J.; Branca, A.; Winands, G.J.J.; Roozeboom, F.

    2011-01-01

    An atmospheric pressure plasma enhanced atomic layer deposition reactor has been developed, to deposit Al2O3 films from trimethyl aluminum and an He/O2 plasma. This technique can be used for 2D patterned deposition in a single in-line process by making use of switched localized plasma sources. It

  16. Low-temperature atomic layer deposition of MoOx for silicon heterojunction solar cells

    NARCIS (Netherlands)

    Macco, B.; Vos, M.; Thissen, N.F.W.; Bol, A.A.; Kessels, W.M.M.

    2015-01-01

    The preparation of high-quality molybdenum oxide (MoOx) is demonstrated by plasma-enhanced atomic layer deposition (ALD) at substrate temperatures down to 50 °C. The films are amorphous, slightly substoichiometric with respect to MoO3, and free of other elements apart from hydrogen (&11 at%). The

  17. Atomic Layer Deposition of SnO2 on MXene for Li-Ion Battery Anodes

    KAUST Repository

    Ahmed, Bilal; Anjum, Dalaver H.; Gogotsi, Yury; Alshareef, Husam N.

    2017-01-01

    In this report, we show that oxide battery anodes can be grown on two-dimensional titanium carbide sheets (MXenes) by atomic layer deposition. Using this approach, we have fabricated a composite SnO2/MXene anode for Li-ion battery applications

  18. Interfacial engineering of two-dimensional nano-structured materials by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhuiykov, Serge, E-mail: serge.zhuiykov@ugent.be [Ghent University Global Campus, Department of Applied Analytical & Physical Chemistry, Faculty of Bioscience Engineering, 119 Songdomunhwa-ro, Yeonsu-Gu, Incheon 406-840 (Korea, Republic of); Kawaguchi, Toshikazu [Global Station for Food, Land and Water Resources, Global Institution for Collaborative Research and Education, Hokkaido University, N10W5 Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Graduate School of Environmental Science, Hokkaido University, N10W5 Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Hai, Zhenyin; Karbalaei Akbari, Mohammad; Heynderickx, Philippe M. [Ghent University Global Campus, Department of Applied Analytical & Physical Chemistry, Faculty of Bioscience Engineering, 119 Songdomunhwa-ro, Yeonsu-Gu, Incheon 406-840 (Korea, Republic of)

    2017-01-15

    Highlights: • Advantages of atomic layer deposition technology (ALD) for two-dimensional nano-crystals. • Conformation of ALD technique and chemistry of precursors. • ALD of semiconductor oxide thin films. • Ultra-thin (∼1.47 nm thick) ALD-developed tungsten oxide nano-crystals on large area. - Abstract: Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise nanometer-thin two-dimensional (2D) nanostructures. It is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. ALD is especially advantageous when the film quality or thickness is critical, offering ultra-high aspect ratios. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even over a very large and complex areas. Digital control extends to sandwiches, hetero-structures, nano-laminates, metal oxides, graded index layers and doping, and it is perfect for conformal coating and challenging 2D electrodes for various functional devices. The technique’s capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO{sub 3}) over the large area of standard 4” Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.

  19. Atomic layer deposition for high-efficiency crystalline silicon solar cells

    NARCIS (Netherlands)

    Macco, B.; van de Loo, B.W.H.; Kessels, W.M.M.; Bachmann, J.

    2017-01-01

    This chapter illustrates that Atomic Layer Deposition (ALD) is in fact an enabler of novel high-efficiency Si solar cells, owing to its merits such as a high material quality, precise thickness control, and the ability to prepare film stacks in a well-controlled way. It gives an overview of the

  20. Atomic layer deposition of high-mobility hydrogen-doped zinc oxide

    NARCIS (Netherlands)

    Macco, B.; Knoops, H.C.M.; Verheijen, M.A.; Beyer, W.; Creatore, M.; Kessels, W.M.M.

    2017-01-01

    In this work, atomic layer deposition (ALD) has been employed to prepare high-mobility H-doped zinc oxide (ZnO:H) films. Hydrogen doping was achieved by interleaving the ZnO ALD cycles with H2 plasma treatments. It has been shown that doping with H2 plasma offers key advantages over traditional

  1. Fabrication of Nanolaminates with Ultrathin Nanolayers Using Atomic Layer Deposition: Nucleation & Growth Issues

    Science.gov (United States)

    2009-02-01

    Tecnologia de Superficies y Materiales (SMCTSM), XXVII Congreso Nacional, Oaxaca, Oaxaca, Mexico, September 26, 2007. 26. "Atomic Layer Deposition of...Nanolaminates: Fabrication and Properties" (Plenary Lecture), Sociedad Mexicana de Ciencia y Tecnologia de Superficies y Materiales (SMCTSM), XXVII

  2. Atomic layer deposition for photovoltaics : applications and prospects for solar cell manufacturing

    NARCIS (Netherlands)

    van Delft, J.A.; Garcia-Alonso Garcia, D.; Kessels, W.M.M.

    2012-01-01

    Atomic layer deposition (ALD) is a vapour-phase deposition technique capable of depositing high quality, uniform and conformal thin films at relatively low temperatures. These outstanding properties can be employed to face processing challenges for various types of next-generation solar cells;

  3. Atmospheric spatial atomic layer deposition of in-doped ZnO

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Roozeboom, F.; Poodt, P.

    2014-01-01

    Indium-doped zinc oxide (ZnO:In) has been grown by spatial atomic layer deposition at atmospheric pressure (spatial-ALD). Trimethyl indium (TMIn), diethyl zinc (DEZ) and deionized water have been used as In, Zn and O precursor, respectively. The metal content of the films is controlled in the range

  4. Growth and characterization of titanium oxide by plasma enhanced atomic layer deposition

    KAUST Repository

    Zhao, Chao; Hedhili, Mohamed N.; Li, Jingqi; Wang, Qingxiao; Yang, Yang; Chen, Long; LI, LIANG

    2013-01-01

    The growth of TiO2 films by plasma enhanced atomic layer deposition using Star-Ti as a precursor has been systematically studied. The conversion from amorphous to crystalline TiO2 was observed either during high temperature growth or annealing

  5. Electrocatalytic activity of atomic layer deposited Pt-Ru catalysts onto N-doped carbon nanotubes

    NARCIS (Netherlands)

    Johansson, A.-C.; Larsen, J.V.; Verheijen, M.A.; Haugshøj, K.B.; Clausen, H.; Kessels, W.M.M.; Christensen, L.H.; Thomsen, E.V.

    2014-01-01

    Pt-Ru catalysts of various compositions, between 0 and 100 at.% of Ru, were deposited onto N-doped multi-walled carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) at 250 C. The Pt and Ru precursors were trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3) and

  6. Atomic-scale structure of single-layer MoS2 nanoclusters

    DEFF Research Database (Denmark)

    Helveg, S.; Lauritsen, J. V.; Lægsgaard, E.

    2000-01-01

    We have studied using scanning tunneling microscopy (STM) the atomic-scale realm of molybdenum disulfide (MoS2) nanoclusters, which are of interest as a model system in hydrodesulfurization catalysis. The STM gives the first real space images of the shape and edge structure of single-layer MoS2...

  7. Atomic-layer deposited passivation schemes for c-Si solar cells

    NARCIS (Netherlands)

    van de Loo, B.W.H.; Macco, B.; Melskens, J.; Verheijen, M.A.; Kessels, W.M.M.E.

    2016-01-01

    A review of recent developments in the field of passivation of c-Si surfaces is presented, with a particular focus on materials that can be prepared by atomic layer deposition (ALD). Besides Al2O3, various other novel passivation schemes have recently been developed, such as Ga2O3, Ta2O5,

  8. Low temperature growth of gallium oxide thin films via plasma enhanced atomic layer deposition

    NARCIS (Netherlands)

    O'Donoghue, R.; Rechmann, J.; Aghaee, M.; Rogalla, D.; Becker, H.-W.; Creatore, M.; Wieck, A.D.; Devi, A.P.K.

    2017-01-01

    Herein we describe an efficient low temperature (60–160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (Ga2O3) thin films using hexakis(dimethylamido)digallium [Ga(NMe2)3]2 with oxygen (O2) plasma on Si(100). The use of O2 plasma was found to have a significant

  9. History of atomic layer deposition and its relationship with the American Vacuum Society

    NARCIS (Netherlands)

    Parsons, G.N.; Elam, J.W.; George, S.M.; Haukka, S.; Jeon, H.; Kessels, W.M.M.; Leskelä, M.; Poodt, P.; Ritala, M.; Rossnagel, S.M.

    2013-01-01

    This article explores the history of atomic layer deposition (ALD) and its relationship with the American Vacuum Society (AVS). The authors describe the origin and history of ALD science in the 1960s and 1970s. They also report on how the science and technology of ALD progressed through the 1990s

  10. Surface reactions during atomic layer deposition of Pt derived from gas phase infrared spectroscopy

    NARCIS (Netherlands)

    Kessels, W.M.M.; Knoops, H.C.M.; Dielissen, S.A.F.; Mackus, A.J.M.; Sanden, van de M.C.M.

    2009-01-01

    Infrared spectroscopy was used to obtain absolute number information on the reaction products during atomic layer deposition of Pt from (methylcyclopentadienyl)trimethylplatinum [(MeCp)PtMe3] and O2. From the detection of CO2 and H2O it was established that the precursor ligands are oxidatively

  11. Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Delabie, Annelies; Billen, Arne [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Dekkers, Harold; Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Caymax, Matty [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [KU Leuven, Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, Marc [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2015-01-01

    Highlights: • Atomic layer is deposited by O{sub 3} chemisorption reaction on H-terminated Si(100). • O-content has critical impact on the epitaxial thickness of the above-deposited Si. • Oxygen atoms at dimer/back bond configurations enable epitaxial Si on O atomic layer. • Oxygen atoms at hydroxyl and more back bonds, disable epitaxial Si on O atomic layer. - Abstract: Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.

  12. Atomic layer deposition grown composite dielectric oxides and ZnO for transparent electronic applications

    International Nuclear Information System (INIS)

    Gieraltowska, S.; Wachnicki, L.; Witkowski, B.S.; Godlewski, M.; Guziewicz, E.

    2012-01-01

    In this paper, we report on transparent transistor obtained using laminar structure of two high-k dielectric oxides (hafnium dioxide, HfO 2 and aluminum oxide, Al 2 O 3 ) and zinc oxide (ZnO) layer grown at low temperature (60 °C–100 °C) using Atomic Layer Deposition (ALD) technology. Our research was focused on the optimization of technological parameters for composite layers Al 2 O 3 /HfO 2 /Al 2 O 3 for thin film transistor structures with ZnO as a channel and a gate layer. We elaborate on the ALD growth of these oxides, finding that the 100 nm thick layers of HfO 2 and Al 2 O 3 exhibit fine surface flatness and required amorphous microstructure. Growth parameters are optimized for the monolayer growth mode and maximum smoothness required for gating.

  13. Molecular dynamics simulation of chemical sputtering of hydrogen atom on layer structured graphite

    International Nuclear Information System (INIS)

    Ito, A.; Wang, Y.; Irle, S.; Morokuma, K.; Nakamura, H.

    2008-10-01

    Chemical sputtering of hydrogen atom on graphite was simulated using molecular dynamics. Especially, the layer structure of the graphite was maintained by interlayer intermolecular interaction. Three kinds of graphite surfaces, flat (0 0 0 1) surface, armchair (1 1 2-bar 0) surface and zigzag (1 0 1-bar 0) surface, are dealt with as targets of hydrogen atom bombardment. In the case of the flat surface, graphene layers were peeled off one by one and yielded molecules had chain structures. On the other hand, C 2 H 2 and H 2 are dominant yielded molecules on the armchair and zigzag surfaces, respectively. In addition, the interaction of a single hydrogen isotope on a single graphene is investigated. Adsorption, reflection and penetration rates are obtained as functions of incident energy and explain hydrogen retention on layered graphite. (author)

  14. Self-cleaning and surface chemical reactions during hafnium dioxide atomic layer deposition on indium arsenide.

    Science.gov (United States)

    Timm, Rainer; Head, Ashley R; Yngman, Sofie; Knutsson, Johan V; Hjort, Martin; McKibbin, Sarah R; Troian, Andrea; Persson, Olof; Urpelainen, Samuli; Knudsen, Jan; Schnadt, Joachim; Mikkelsen, Anders

    2018-04-12

    Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor-oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.

  15. MIM capacitors with various Al2O3 thicknesses for GaAs RFIC application

    International Nuclear Information System (INIS)

    Zhou Jiahui; Xu Wenjun; Li Qi; Li Simin; He Zhiyi; Li Haiou; Chang Hudong; Liu Honggang; Liu Guiming

    2015-01-01

    The impact of various thicknesses of Al 2 O 3 metal—insulator—metal (MIM) capacitors on direct current and radio frequency (RF) characteristics is investigated. For 20 nm Al 2 O 3 , the fabricated capacitor exhibits a high capacitance density of 3850 pF/mm 2 and acceptable voltage coefficients of capacitance of 681 ppm/V 2 at 1 MHz. An outstanding VCC-α of 74 ppm/V 2 at 1 MHz, resonance frequency of 8.2 GHz and Q factor of 41 at 2 GHz are obtained by 100 nm Al 2 O 3 MIM capacitors. High-performance MIM capacitors using GaAs process and atomic layer deposition Al 2 O 3 could be very promising candidates for GaAs RFIC applications. (paper)

  16. ZnO: Hydroquinone superlattice structures fabricated by atomic/molecular layer deposition

    International Nuclear Information System (INIS)

    Tynell, Tommi; Karppinen, Maarit

    2014-01-01

    Here we employ atomic layer deposition in combination with molecular layer deposition to deposit crystalline thin films of ZnO interspersed with single layers of hydroquinone in an effort to create hybrid inorganic–organic superlattice structures. The ratio of the ZnO and hydroquinone deposition cycles is varied between 199:1 and 1:1, and the structure of the resultant thin films is verified with X-ray diffraction and reflectivity techniques. Clear evidence of the formation of a superlattice-type structure is observed in the X-ray reflectivity patterns and the presence of organic bonds in the films corresponding to the structure of hydroquinone is confirmed with Fourier transform infrared spectroscopy measurements. We anticipate that hybrid superlattice structures such as the ones described in this work have the potential to be of great importance for future applications where the precise control of different inorganic and organic layers in hybrid superlattice materials is required. - Highlights: • Inorganic–organic superlattices can be made by atomic/molecular layer deposition. • This is demonstrated here for ZnO and hydroquinone (HQ). • The ratio of the ZnO and HQ layers is varied between 199:1 and 14:1. • The resultant thin films are crystalline

  17. ZnO: Hydroquinone superlattice structures fabricated by atomic/molecular layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tynell, Tommi; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi

    2014-01-31

    Here we employ atomic layer deposition in combination with molecular layer deposition to deposit crystalline thin films of ZnO interspersed with single layers of hydroquinone in an effort to create hybrid inorganic–organic superlattice structures. The ratio of the ZnO and hydroquinone deposition cycles is varied between 199:1 and 1:1, and the structure of the resultant thin films is verified with X-ray diffraction and reflectivity techniques. Clear evidence of the formation of a superlattice-type structure is observed in the X-ray reflectivity patterns and the presence of organic bonds in the films corresponding to the structure of hydroquinone is confirmed with Fourier transform infrared spectroscopy measurements. We anticipate that hybrid superlattice structures such as the ones described in this work have the potential to be of great importance for future applications where the precise control of different inorganic and organic layers in hybrid superlattice materials is required. - Highlights: • Inorganic–organic superlattices can be made by atomic/molecular layer deposition. • This is demonstrated here for ZnO and hydroquinone (HQ). • The ratio of the ZnO and HQ layers is varied between 199:1 and 14:1. • The resultant thin films are crystalline.

  18. Two-Dimensional SnO Anodes with a Tunable Number of Atomic Layers for Sodium Ion Batteries

    KAUST Repository

    Zhang, Fan; Zhu, Jiajie; Zhang, Daliang; Schwingenschlö gl, Udo; Alshareef, Husam N.

    2017-01-01

    We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their sodium ion battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both

  19. Preface: Special Topic on Atomic and Molecular Layer Processing: Deposition, Patterning, and Etching

    Science.gov (United States)

    Engstrom, James R.; Kummel, Andrew C.

    2017-02-01

    Thin film processing technologies that promise atomic and molecular scale control have received increasing interest in the past several years, as traditional methods for fabrication begin to reach their fundamental limits. Many of these technologies involve at their heart phenomena occurring at or near surfaces, including adsorption, gas-surface reactions, diffusion, desorption, and re-organization of near-surface layers. Moreover many of these phenomena involve not just reactions occurring under conditions of local thermodynamic equilibrium but also the action of energetic species including electrons, ions, and hyperthermal neutrals. There is a rich landscape of atomic and molecular scale interactions occurring in these systems that is still not well understood. In this Special Topic Issue of The Journal of Chemical Physics, we have collected recent representative examples of work that is directed at unraveling the mechanistic details concerning atomic and molecular layer processing, which will provide an important framework from which these fields can continue to develop. These studies range from the application of theory and computation to these systems to the use of powerful experimental probes, such as X-ray synchrotron radiation, probe microscopies, and photoelectron and infrared spectroscopies. The work presented here helps in identifying some of the major challenges and direct future activities in this exciting area of research involving atomic and molecular layer manipulation and fabrication.

  20. Effect of GaAs interlayer thickness variations on the optical properties of multiple InAs QD structure

    International Nuclear Information System (INIS)

    Park, C.Y.; Park, K.W.; Kim, J.M.; Lee, Y.T.

    2009-01-01

    Multiple InAs/GaAs self-assembled quantum dots (QDs) with vertically stacked structure are grown by molecular beam epitaxy and the effects of GaAs interlayer thickness variation on optical properties are studied. The growth conditions are optimized by in-situ RHEED, AFM, and PL measurement. The five InAs QD layers are embedded in GaAs and Al0.3Ga0.7As layer. The PL intensity is increased with increasing GaAs interlayer thickness. The thin GaAs interlayer has strain field, the strain-induced intermixing of indium atoms in the InAs QDs (blue-shift) can overcompensate for the effect on the increased QD size (red-shift) (H. Heidemeyer et al. Appl. Phys. Lett. 80, 1544 (2002); T. Nakaoka et al. J. Appl. Phys. Lett. 96, 150 (2004)[1, 2], respectively). For the interlayer thickness larger than about 7 nm, the blue-shifts are correlated to the dominant high-energy excited state transitions due to the successive state filling of the ground and higher excited states in the QDs. The energy separation of double PL peaks, originated from two different excited states, was kept at around 50 meV at room temperature. A possible mechanism concerning this phenomenon is also discussed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel

    Science.gov (United States)

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially ‘clean’ strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2•- radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO-) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  2. TEM and ellipsometry studies of nanolaminate oxide films prepared using atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, D.R.G. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia)]. E-mail: drm@ansto.gov.au; Attard, D.J. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Finnie, K.S. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Triani, G. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Barbe, C.J. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Depagne, C. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Bartlett, J.R. [Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia)

    2005-04-30

    Nanolaminate oxide layers consisting of TiO{sub 2} and Al{sub 2}O{sub 3} have been deposited on silicon using atomic layer deposition (ALD). Characterisation of these films has been achieved by use of a range of modern transmission electron microscopy (TEM)-based techniques, including plasmon loss imaging, energy filtered imaging and scanning TEM (STEM) X-ray line profiling. These have shown that the target thickness of the individual layers in the nanolaminate structures (20 nm) has been met with a high degree of accuracy, that the layers are extremely flat and parallel and that the interfaces between the layers are compositionally abrupt. Localised crystallisation within the stacks, and responses to electron beam irradiation point to the presence of a stress gradient within the layers. The performance of ellipsometry in characterising multilayer stacks has been benchmarked against the TEM measurements. Errors in determination of individual layer thicknesses were found to increase with growing stack size, as expected given the increasing number of interfaces incorporated in each model. The most sophisticated model gave maximum deviations of {+-}4 nm from the TEM determined values for the 5- and 10-layer stacks.

  3. Fabrication of ultrathin multilayered superomniphobic nanocoatings by liquid flame spray, atomic layer deposition, and silanization

    Science.gov (United States)

    Sorvali, Miika; Vuori, Leena; Pudas, Marko; Haapanen, Janne; Mahlberg, Riitta; Ronkainen, Helena; Honkanen, Mari; Valden, Mika; Mäkelä, Jyrki M.

    2018-05-01

    Superomniphobic, i.e. liquid-repellent, surfaces have been an interesting area of research during recent years due to their various potential applications. However, producing such surfaces, especially on hard and resilient substrates like stainless steel, still remains challenging. We present a stepwise fabrication process of a multilayered nanocoating on a stainless steel substrate, consisting of a nanoparticle layer, a nanofilm, and a layer of silane molecules. Liquid flame spray was used to deposit a TiO2 nanoparticle layer as the bottom layer for producing a suitable surface structure. The interstitial Al2O3 nanofilm, fabricated by atomic layer deposition (ALD), stabilized the nanoparticle layer, and the topmost fluorosilane layer lowered the surface energy of the coating for enhanced omniphobicity. The coating was characterized with field emission scanning electron microscopy, focused ion beam scanning electron microscopy, x-ray photoelectron spectroscopy, contact angle (CA) and sliding angle (SA) measurements, and microscratch testing. The widely recognized requirements for superrepellency, i.e. CA > 150° and SA < 10°, were achieved for deioinized water, diiodomethane, and ethylene glycol. The mechanical stability of the coating could be varied by tuning the thickness of the ALD layer at the expense of repellency. To our knowledge, this is the thinnest superomniphobic coating reported so far, with the average thickness of about 70 nm.

  4. Fabrication of ultrathin multilayered superomniphobic nanocoatings by liquid flame spray, atomic layer deposition, and silanization.

    Science.gov (United States)

    Sorvali, Miika; Vuori, Leena; Pudas, Marko; Haapanen, Janne; Mahlberg, Riitta; Ronkainen, Helena; Honkanen, Mari; Valden, Mika; Mäkelä, Jyrki M

    2018-05-04

    Superomniphobic, i.e. liquid-repellent, surfaces have been an interesting area of research during recent years due to their various potential applications. However, producing such surfaces, especially on hard and resilient substrates like stainless steel, still remains challenging. We present a stepwise fabrication process of a multilayered nanocoating on a stainless steel substrate, consisting of a nanoparticle layer, a nanofilm, and a layer of silane molecules. Liquid flame spray was used to deposit a TiO 2 nanoparticle layer as the bottom layer for producing a suitable surface structure. The interstitial Al 2 O 3 nanofilm, fabricated by atomic layer deposition (ALD), stabilized the nanoparticle layer, and the topmost fluorosilane layer lowered the surface energy of the coating for enhanced omniphobicity. The coating was characterized with field emission scanning electron microscopy, focused ion beam scanning electron microscopy, x-ray photoelectron spectroscopy, contact angle (CA) and sliding angle (SA) measurements, and microscratch testing. The widely recognized requirements for superrepellency, i.e. CA > 150° and SA layer at the expense of repellency. To our knowledge, this is the thinnest superomniphobic coating reported so far, with the average thickness of about 70 nm.

  5. Magnetic resonance of rubidium atoms passing through a multi-layered transmission magnetic grating

    International Nuclear Information System (INIS)

    Nagata, Y; Kurokawa, S; Hatakeyama, A

    2017-01-01

    We measured the magnetic resonance of rubidium atoms passing through periodic magnetic fields generated by two types of multi-layered transmission magnetic grating. One of the gratings reported here was assembled by stacking four layers of magnetic films so that the direction of magnetization alternated at each level. The other grating was assembled so that the magnetization at each level was aligned. For both types of grating, the experimental results were in good agreement with our calculations. We studied the feasibility of extending the frequency band of the grating and narrowing its resonance linewidth by performing calculations. For magnetic resonance precision spectroscopy, we conclude that the multi-layered transmission magnetic grating can generate periodic fields with narrower linewidths at higher frequencies when a larger number of layers are assembled at a shorter period length. Moreover, the frequency band of this type of grating can potentially achieve frequencies of up to hundreds of PHz. (paper)

  6. Scalable control program for multiprecursor flow-type atomic layer deposition system

    Energy Technology Data Exchange (ETDEWEB)

    Selvaraj, Sathees Kannan [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Takoudis, Christos G., E-mail: takoudis@uic.edu [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 and Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)

    2015-01-01

    The authors report the development and implementation of a scalable control program to control flow type atomic layer deposition (ALD) reactor with multiple precursor delivery lines. The program logic is written and tested in LABVIEW environment to control ALD reactor with four precursor delivery lines to deposit up to four layers of different materials in cyclic manner. The programming logic is conceived such that to facilitate scale up for depositing more layers with multiple precursors and scale down for using single layer with any one precursor in the ALD reactor. The program takes precursor and oxidizer exposure and purging times as input and controls the sequential opening and closing of the valves to facilitate the complex ALD process in cyclic manner. The program could be used to deposit materials from any single line or in tandem with other lines in any combination and in any sequence.

  7. Interface magnetism of iron grown on sulfur and hydrogen passivated GaAs(001)

    International Nuclear Information System (INIS)

    Kardasz, B.; Watkins, S. P.; Montoya, E. A.; Burrowes, C.; Girt, E.; Heinrich, B.

    2012-01-01

    Sulfur (S) and hydrogen (H) atom passivated GaAs(001) templates were used for deposition of ultrathin crystalline Fe films using molecular beam epitaxy, where the Fe thickness ranged from 10 to 45 atomic layers. Reflection high-energy electron diffraction patterns showed that the S- and H-passivated surfaces had no and very weak (1 x 2) superlattice reconstructions, respectively. This indicates that these GaAs(001) templates have a square-like symmetry. Magnetic anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance at 36 GHz. The in-plane cubic and uniaxial anisotropies and perpendicular uniaxial field were described by bulk and interface contributions, indicating that the Fe films have a high lattice coherence. The magnetic properties of the Fe films were compared to those grown on more commonly used GaAs(001) templates having a (4 x 6) reconstruction with an As-rich in-plane uniaxial symmetry. The Fe films grown on S-passivated templates exhibited unique magnetic properties caused by a decreased lattice spacing compared to the bulk Fe.

  8. Interface magnetism of iron grown on sulfur and hydrogen passivated GaAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kardasz, B.; Watkins, S. P.; Montoya, E. A.; Burrowes, C.; Girt, E.; Heinrich, B.

    2012-04-01

    Sulfur (S) and hydrogen (H) atom passivated GaAs(001) templates were used for deposition of ultrathin crystalline Fe films using molecular beam epitaxy, where the Fe thickness ranged from 10 to 45 atomic layers. Reflection high-energy electron diffraction patterns showed that the S- and H-passivated surfaces had no and very weak (1 x 2) superlattice reconstructions, respectively. This indicates that these GaAs(001) templates have a square-like symmetry. Magnetic anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance at 36 GHz. The in-plane cubic and uniaxial anisotropies and perpendicular uniaxial field were described by bulk and interface contributions, indicating that the Fe films have a high lattice coherence. The magnetic properties of the Fe films were compared to those grown on more commonly used GaAs(001) templates having a (4 x 6) reconstruction with an As-rich in-plane uniaxial symmetry. The Fe films grown on S-passivated templates exhibited unique magnetic properties caused by a decreased lattice spacing compared to the bulk Fe.

  9. 2D-PES/XAS method for atomic-layer-resolved magnetic structure analysis

    International Nuclear Information System (INIS)

    Matsui, F.; Daimon, H.; Matsushita, T.; Guo, F.Z.

    2008-01-01

    Photoelectron and Auger electron angular distributions from a localized core level provide information on atomic configurations. Forward-focusing peaks indicate the directions of atoms surrounding the excited atom. X-ray absorption fine structure and X-ray magnetic circular dichroism measurements by Auger electron yield detection on the other hand are excellent methods for studying of the electronic and magnetic structures of surfaces, adsorbates, and thin films. However, all the information from atoms within the electron mean-free-path region is averaged into the obtained spectra. Here, we introduce a new method of X-ray absorption spectroscopy (XAS) combined with measurements of Auger electron angular distribution using a display-type analyzer. Taking advantage of the forward-focusing peak as an excellent element- and site-selective probe, 2D-XAS enables direct access to the individual electronic and magnetic structures of each atomic layer. This method was applied to studying the electronic and magnetic structures of Ni thin film at atomic level. (author)

  10. Atomic layer MoS2-graphene van der Waals heterostructure nanomechanical resonators.

    Science.gov (United States)

    Ye, Fan; Lee, Jaesung; Feng, Philip X-L

    2017-11-30

    Heterostructures play significant roles in modern semiconductor devices and micro/nanosystems in a plethora of applications in electronics, optoelectronics, and transducers. While state-of-the-art heterostructures often involve stacks of crystalline epi-layers each down to a few nanometers thick, the intriguing limit would be hetero-atomic-layer structures. Here we report the first experimental demonstration of freestanding van der Waals heterostructures and their functional nanomechanical devices. By stacking single-layer (1L) MoS 2 on top of suspended single-, bi-, tri- and four-layer (1L to 4L) graphene sheets, we realize an array of MoS 2 -graphene heterostructures with varying thickness and size. These heterostructures all exhibit robust nanomechanical resonances in the very high frequency (VHF) band (up to ∼100 MHz). We observe that fundamental-mode resonance frequencies of the heterostructure devices fall between the values of graphene and MoS 2 devices. Quality (Q) factors of heterostructure resonators are lower than those of graphene but comparable to those of MoS 2 devices, suggesting interface damping related to interlayer interactions in the van der Waals heterostructures. This study validates suspended atomic layer heterostructures as an effective device platform and provides opportunities for exploiting mechanically coupled effects and interlayer interactions in such devices.

  11. Reliably counting atomic planes of few-layer graphene (n > 4).

    Science.gov (United States)

    Koh, Yee Kan; Bae, Myung-Ho; Cahill, David G; Pop, Eric

    2011-01-25

    We demonstrate a reliable technique for counting atomic planes (n) of few-layer graphene (FLG) on SiO(2)/Si substrates by Raman spectroscopy. Our approach is based on measuring the ratio of the integrated intensity of the G graphene peak and the optical phonon peak of Si, I(G)/I(Si), and is particularly useful in the range n > 4 where few methods exist. We compare our results with atomic force microscopy (AFM) measurements and Fresnel equation calculations. Then, we apply our method to unambiguously identify n of FLG devices on SiO(2) and find that the mobility (μ ≈ 2000 cm(2) V(-1) s(-1)) is independent of layer thickness for n > 4. Our findings suggest that electrical transport in gated FLG devices is dominated by carriers near the FLG/SiO(2) interface and is thus limited by the environment, even for n > 4.

  12. Hydrothermal crystallization of amorphous titania films deposited using low temperature atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, D.R.G. [Institute of Materials Engineering, ANSTO, PMB 1, Menai, NSW 2234 (Australia)], E-mail: drm@ansto.gov.au; Triani, G.; Zhang, Z. [Institute of Materials Engineering, ANSTO, PMB 1, Menai, NSW 2234 (Australia)

    2008-10-01

    A two stage process (atomic layer deposition, followed by hydrothermal treatment) for producing crystalline titania thin films at temperatures compatible with polymeric substrates (< 130 deg. C) has been assessed. Titania thin films were deposited at 80 deg. C using atomic layer deposition. They were extremely flat, uniform and almost entirely amorphous. They also contained relatively high levels of residual Cl from the precursor. After hydrothermal treatment at 120 deg. C for 1 day, > 50% of the film had crystallized. Crystallization was complete after 10 days of hydrothermal treatment. Crystallization of the film resulted in the formation of coarse grained anatase. Residual Cl was completely expelled from the film upon crystallization. As a result of the amorphous to crystalline transformation voids formed at the crystallization front. Inward and lateral crystal growth resulted in voids being localized to the film/substrate interface and crystallite perimeters resulting in pinholing. Both these phenomena resulted in films with poor adhesion and film integrity was severely compromised.

  13. Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Adib Abou Chaaya

    2013-10-01

    Full Text Available A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near the edge. A high oxygen ratio and variable optical properties could be attractive for an application of atomic layer deposition (ALD deposited ultrathin ZnO films in optical sensors and biosensors.

  14. Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

    Science.gov (United States)

    Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

    2014-04-22

    Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

  15. Method to determine the sticking coefficient of precursor molecules in atomic layer deposition

    International Nuclear Information System (INIS)

    Rose, M.; Bartha, J.W.

    2009-01-01

    A method to determine the sticking coefficient of precursor molecules used in atomic layer deposition (ALD) will be introduced. The sticking coefficient is an interesting quantity for comparing different ALD processes and reactors but it cannot be observed easily. The method relies on free molecular flow in nanoscale cylindrical holes. The sticking coefficient is determined for tetrakis(dimethylamino)titanium in combination with ozone. The proposed method can be applied independent of the type of reactor, precursor delivery system and precursors.

  16. Dispersion engineering of thick high-Q silicon nitride ring-resonators via atomic layer deposition.

    Science.gov (United States)

    Riemensberger, Johann; Hartinger, Klaus; Herr, Tobias; Brasch, Victor; Holzwarth, Ronald; Kippenberg, Tobias J

    2012-12-03

    We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition. Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. The results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.

  17. Peeled film GaAs solar cell development

    International Nuclear Information System (INIS)

    Wilt, D.M.; Thomas, R.D.; Bailey, S.G.; Brinker, D.J.; DeAngelo, F.L.

    1990-01-01

    Thin film, single crystal gallium arsenide (GaAs) solar cells could exhibit a specific power approaching 700 W/Kg including coverglass. A simple process has been described whereby epitaxial GaAs layers are peeled from a reusable substrate. This process takes advantage of the extreme selectivity (>10 6 ) of the etching rate of aluminum arsenide (AlAs) over GaAs in dilute hydrofloric acid (HF). The intent of this work is to demonstrate the feasibility of using the peeled film technique to fabricate high efficiency, low mass GaAs solar cells. We have successfully produced a peeled film GaAs solar cell. The device, although fractured and missing the aluminum gallium arsenide (Al x Ga 1 - x As) window and antireflective (AR) coating, had a Voc of 874 mV and a fill factor of 68% under AMO illumination

  18. Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

    International Nuclear Information System (INIS)

    Kaeaeriaeinen, Tommi O.; Maydannik, Philipp; Cameron, David C.; Lahtinen, Kimmo; Johansson, Petri; Kuusipalo, Jurkka

    2011-01-01

    One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O 2 TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O 2 TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

  19. Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

    Energy Technology Data Exchange (ETDEWEB)

    Kaeaeriaeinen, Tommi O., E-mail: tommi.kaariainen@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Cameron, David C., E-mail: david.cameron@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Lahtinen, Kimmo, E-mail: kimmo.lahtinen@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Johansson, Petri, E-mail: petri.johansson@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland)

    2011-03-01

    One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O{sub 2}TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O{sub 2}TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

  20. Two-dimensional ferroelectric topological insulators in functionalized atomically thin bismuth layers

    Science.gov (United States)

    Kou, Liangzhi; Fu, Huixia; Ma, Yandong; Yan, Binghai; Liao, Ting; Du, Aijun; Chen, Changfeng

    2018-02-01

    We introduce a class of two-dimensional (2D) materials that possess coexisting ferroelectric and topologically insulating orders. Such ferroelectric topological insulators (FETIs) occur in noncentrosymmetric atomic layer structures with strong spin-orbit coupling (SOC). We showcase a prototype 2D FETI in an atomically thin bismuth layer functionalized by C H2OH , which exhibits a large ferroelectric polarization that is switchable by a ligand molecule rotation mechanism and a strong SOC that drives a band inversion leading to the topologically insulating state. An external electric field that switches the ferroelectric polarization also tunes the spin texture in the underlying atomic lattice. Moreover, the functionalized bismuth layer exhibits an additional quantum order driven by the valley splitting at the K and K' points in the Brillouin zone stemming from the symmetry breaking and strong SOC in the system, resulting in a remarkable state of matter with the simultaneous presence of the quantum spin Hall and quantum valley Hall effect. These phenomena are predicted to exist in other similarly constructed 2D FETIs, thereby offering a unique quantum material platform for discovering novel physics and exploring innovative applications.

  1. Imaging with Mass Spectrometry: A SIMS and VUV-Photoionization Study of Ion-Sputtered Atoms and Clusters from GaAs and Au

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Lynelle; Zhou, Jia; Wilson, Kevin R.; Leone, Stephen R.; Ahmed, Musahid

    2008-12-05

    A new mass spectrometry surface imaging method is presented in which ion-sputtered neutrals are postionized by wavelength-tunable vacuum ultraviolet (VUV) light from a synchrotron source. Mass spectra and signal counts of the photoionized neutrals from GaAs (100) and Au are compared to those of the secondary ions. While clusters larger than dimers are more efficiently detected as secondary ions, certain species, such as As2, Au and Au2, are more efficiently detected through the neutral channel. Continuously tuning the photon wavelength allows photoionization efficiency (PIE) curves to be obtained for sputtered Asm (m=1,2) and Aun (n=1-4). From the observed ionization thresholds, sputtered neutral As and Au show no clear evidence of electronic excitation, while neutral clusters have photoionization onsets shifted to lower energies by ~;;0.3 eV. These shifts are attributed to unresolved vibrational and rotational excitations. High-spatial resolution chemical imaging with synchrotron VUV postionization is demonstrated at two different photon energies using a copper TEM grid embedded in indium. The resulting images are used to illustrate the use of tunable VUV light for verifying mass peak assignments by exploiting the unique wavelength-dependent PIE of each sputtered neutral species. This capability is valuable for identifying compounds when imaging chemically complex systems with mass spectrometry-based techniques.

  2. The diffusion of a Ga atom on GaAs(001)β2(2 × 4): Local superbasin kinetic Monte Carlo

    Science.gov (United States)

    Lin, Yangzheng; Fichthorn, Kristen A.

    2017-10-01

    We use first-principles density-functional theory to characterize the binding sites and diffusion mechanisms for a Ga adatom on the GaAs(001)β 2(2 × 4) surface. Diffusion in this system is a complex process involving eleven unique binding sites and sixteen different hops between neighboring binding sites. Among the binding sites, we can identify four different superbasins such that the motion between binding sites within a superbasin is much faster than hops exiting the superbasin. To describe diffusion, we use a recently developed local superbasin kinetic Monte Carlo (LSKMC) method, which accelerates a conventional kinetic Monte Carlo (KMC) simulation by describing the superbasins as absorbing Markov chains. We find that LSKMC is up to 4300 times faster than KMC for the conditions probed in this study. We characterize the distribution of exit times from the superbasins and find that these are sometimes, but not always, exponential and we characterize the conditions under which the superbasin exit-time distribution should be exponential. We demonstrate that LSKMC simulations assuming an exponential superbasin exit-time distribution yield the same diffusion coefficients as conventional KMC.

  3. Preparation of GaAs photocathodes at low temperature

    International Nuclear Information System (INIS)

    Mulhollan, G.; Clendenin, J.; Tang, H.

    1996-10-01

    The preparation of an atomically clean surface is a necessary step in the formation of negative electron affinity (NEA) GaAs. Traditional methods to this end include cleaving, heat cleaning and epitaxial growth. Cleaving has the advantage of yielding a fresh surface after each cleave, but is limited to small areas and is not suitable for specialized structures. Heat cleaning is both simple and highly successful, so it is used as a preparation method in virtually all laboratories employing a NEA source on a regular basis. Due to its high cost and complexity, epitaxial growth of GaAs with subsequent in vacuo transfer is not a practical solution for most end users of GaAs as a NEA electron source. While simple, the heating cleaning process has a number of disadvantages. Here, a variety of cleaning techniques related to preparation of an atomically clean GaAs surface without heating to 600 C are discussed and evaluated

  4. Atomic Layer Deposition of Stable LiAlF4 Lithium Ion Conductive Interfacial Layer for Stable Cathode Cycling.

    Science.gov (United States)

    Xie, Jin; Sendek, Austin D; Cubuk, Ekin D; Zhang, Xiaokun; Lu, Zhiyi; Gong, Yongji; Wu, Tong; Shi, Feifei; Liu, Wei; Reed, Evan J; Cui, Yi

    2017-07-25

    Modern lithium ion batteries are often desired to operate at a wide electrochemical window to maximize energy densities. While pushing the limit of cutoff potentials allows batteries to provide greater energy densities with enhanced specific capacities and higher voltage outputs, it raises key challenges with thermodynamic and kinetic stability in the battery. This is especially true for layered lithium transition-metal oxides, where capacities can improve but stabilities are compromised as wider electrochemical windows are applied. To overcome the above-mentioned challenges, we used atomic layer deposition to develop a LiAlF 4 solid thin film with robust stability and satisfactory ion conductivity, which is superior to commonly used LiF and AlF 3 . With a predicted stable electrochemical window of approximately 2.0 ± 0.9 to 5.7 ± 0.7 V vs Li + /Li for LiAlF 4 , excellent stability was achieved for high Ni content LiNi 0.8 Mn 0.1 Co 0.1 O 2 electrodes with LiAlF 4 interfacial layer at a wide electrochemical window of 2.75-4.50 V vs Li + /Li.

  5. Atomic layer deposition and etching methods for far ultraviolet aluminum mirrors

    Science.gov (United States)

    Hennessy, John; Moore, Christopher S.; Balasubramanian, Kunjithapatham; Jewell, April D.; Carter, Christian; France, Kevin; Nikzad, Shouleh

    2017-09-01

    High-performance aluminum mirrors at far ultraviolet wavelengths require transparent dielectric materials as protective coatings to prevent oxidation. Reducing the thickness of this protective layer can result in additional performance gains by minimizing absorption losses, and provides a path toward high Al reflectance in the challenging wavelength range of 90 to 110 nm. We have pursued the development of new atomic layer deposition processes (ALD) for the metal fluoride materials of MgF2, AlF3 and LiF. Using anhydrous hydrogen fluoride as a reactant, these films can be deposited at the low temperatures required for large-area surface-finished optics and polymeric diffraction gratings. We also report on the development and application of an atomic layer etching (ALE) procedure to controllably etch native aluminum oxide. Our ALE process utilizes the same chemistry used in the ALD of AlF3 thin films, allowing for a combination of high-performance evaporated Al layers and ultrathin ALD encapsulation without requiring vacuum transfer. Progress in demonstrating the scalability of this approach, as well as the environmental stability of ALD/ALE Al mirrors are discussed in the context of possible future applications for NASA LUVOIR and HabEx mission concepts.

  6. Ti–Al–O nanocrystal charge trapping memory cells fabricated by atomic layer deposition

    International Nuclear Information System (INIS)

    Cao, Zheng-Yi; Li, Ai-Dong; Li, Xin; Cao, Yan-Qiang; Wu, Di

    2014-01-01

    Charge trapping memory cells using Ti–Al–O (TAO) film as charge trapping layer and amorphous Al 2 O 3 as the tunneling and blocking layers were fabricated on Si substrates by atomic layer deposition method. As-deposited TAO films were annealed at 700 °C, 800 °C and 900 °C for 3 min in N 2 with a rapid thermal annealing process to form nanocrystals. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize the microstructure and band diagram of the heterostructures. The electrical characteristics and charge storage properties of the Al 2 O 3 /TAO/Al 2 O 3 /Si stack structures were also evaluated. Compared to 700 °C and 900 °C samples, the memory cells annealed at 800 °C exhibit better memory performance with larger memory window of 4.8 V at ± 6 V sweeping, higher program/erase speed and excellent endurance. - Highlights: • The charge trapping memory cells were fabricated by atomic layer deposition method. • The anneal temperature plays a key role in forming nanocrystals. • The memory cells annealed at 800 °C exhibit better memory performance. • The band alignment is beneficial to enhance the retention characteristics

  7. Conduction and stability of holmium titanium oxide thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Castán, H., E-mail: helena@ele.uva.es [Department of Electronic, University of Valladolid, 47011 Valladolid (Spain); García, H.; Dueñas, S.; Bailón, L. [Department of Electronic, University of Valladolid, 47011 Valladolid (Spain); Miranda, E. [Departament d' Enginyería Electrònica, Universitat Autónoma de Barcelona, 08193 Bellaterra (Spain); Kukli, K. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland); Institute of Physics, University of Tartu, EE-50411,Tartu (Estonia); Kemell, M.; Ritala, M.; Leskelä, M. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland)

    2015-09-30

    Holmium titanium oxide (HoTiO{sub x}) thin films of variable chemical composition grown by atomic layer deposition are studied in order to assess their suitability as dielectric materials in metal–insulator–metal electronic devices. The correlation between thermal and electrical stabilities as well as the potential usefulness of HoTiO{sub x} as a resistive switching oxide are also explored. It is shown that the layer thickness and the relative holmium content play important roles in the switching behavior of the devices. Cycled current–voltage measurements showed that the resistive switching is bipolar with a resistance window of up to five orders of magnitude. In addition, it is demonstrated that the post-breakdown current–voltage characteristics in HoTiO{sub x} are well described by a power-law model in a wide voltage and current range which extends from the soft to the hard breakdown regimes. - Highlights: • Gate and memory suitabilities of atomic layer deposited holmium titanium oxide. • Holmium titanium oxide exhibits resistive switching. • Layer thickness and holmium content influence the resistive switching. • Low and high resistance regimes follow a power-law model. • The power-law model can be extended to the hard breakdown regime.

  8. Atomic scale imaging of competing polar states in a Ruddlesden–Popper layered oxide

    Science.gov (United States)

    Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J.; Schlom, Darrell G.; Alem, Nasim; Gopalan, Venkatraman

    2016-01-01

    Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden–Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure. PMID:27578622

  9. Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide.

    Science.gov (United States)

    Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J; Schlom, Darrell G; Alem, Nasim; Gopalan, Venkatraman

    2016-08-31

    Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden-Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure.

  10. Atomic layer deposited high-k dielectric on graphene by functionalization through atmospheric plasma treatment

    Science.gov (United States)

    Shin, Jeong Woo; Kang, Myung Hoon; Oh, Seongkook; Yang, Byung Chan; Seong, Kwonil; Ahn, Hyo-Sok; Lee, Tae Hoon; An, Jihwan

    2018-05-01

    Atomic layer-deposited (ALD) dielectric films on graphene usually show noncontinuous and rough morphology owing to the inert surface of graphene. Here, we demonstrate the deposition of thin and uniform ALD ZrO2 films with no seed layer on chemical vapor-deposited graphene functionalized by atmospheric oxygen plasma treatment. Transmission electron microscopy showed that the ALD ZrO2 films were highly crystalline, despite a low ALD temperature of 150 °C. The ALD ZrO2 film served as an effective passivation layer for graphene, which was shown by negative shifts in the Dirac voltage and the enhanced air stability of graphene field-effect transistors after ALD of ZrO2. The ALD ZrO2 film on the functionalized graphene may find use in flexible graphene electronics and biosensors owing to its low process temperature and its capacity to improve device performance and stability.

  11. Quantum Hall states of atomic Bose gases: Density profiles in single-layer and multilayer geometries

    International Nuclear Information System (INIS)

    Cooper, N. R.; Lankvelt, F. J. M. van; Reijnders, J. W.; Schoutens, K.

    2005-01-01

    We describe the density profiles of confined atomic Bose gases in the high-rotation limit, in single-layer and multilayer geometries. We show that, in a local-density approximation, the density in a single layer shows a landscape of quantized steps due to the formation of incompressible liquids, which are analogous to fractional quantum Hall liquids for a two-dimensional electron gas in a strong magnetic field. In a multilayered setup we find different phases, depending on the strength of the interlayer tunneling t. We discuss the situation where a vortex lattice in the three-dimensional condensate (at large tunneling) undergoes quantum melting at a critical tunneling t c 1 . For tunneling well below t c 1 one expects weakly coupled or isolated layers, each exhibiting a landscape of quantum Hall liquids. After expansion, this gives a radial density distribution with characteristic features (cusps) that provide experimental signatures of the quantum Hall liquids

  12. Aluminum oxide barrier coating on polyethersulfone substrate by atomic layer deposition for barrier property enhancement

    International Nuclear Information System (INIS)

    Kim, Hyun Gi; Kim, Sung Soo

    2011-01-01

    Aluminum oxide layers were deposited on flexible polyethersulfone (PES) substrates via plasma enhanced atomic layer deposition (PEALD) process using trimethylaluminum (TMA) and oxygen as precursor and reactant materials. Several process parameters in PEALD process were investigated in terms of refractive index and layer thickness. Number of process cycle increased the thickness and refractive index of the layer to enhance the barrier properties. Non-physisorbed TMA and unreacted oxygen were purged before and after the plasma reaction, respectively. Identical purge time was applied to TMA and oxygen and it was optimized for 10 s. Thinner and denser layer was formed as substrate temperature increased. However, the PES substrate could be deformed above 120 o C. Aluminum oxide layer formed on PES at optimized conditions have 11.8 nm of thickness and reduced water vapor transmission rate and oxygen transmission rate to below 4 x 10 -3 g/m 2 day and 4 x 10 -3 cm 3 /m 2 day, respectively. Polycarbonate and polyethylene naphthalate films were also tested at optimized conditions, and they also showed quite appreciable barrier properties to be used as plastic substrates.

  13. Atom-scale depth localization of biologically important chemical elements in molecular layers.

    Science.gov (United States)

    Schneck, Emanuel; Scoppola, Ernesto; Drnec, Jakub; Mocuta, Cristian; Felici, Roberto; Novikov, Dmitri; Fragneto, Giovanna; Daillant, Jean

    2016-08-23

    In nature, biomolecules are often organized as functional thin layers in interfacial architectures, the most prominent examples being biological membranes. Biomolecular layers play also important roles in context with biotechnological surfaces, for instance, when they are the result of adsorption processes. For the understanding of many biological or biotechnologically relevant phenomena, detailed structural insight into the involved biomolecular layers is required. Here, we use standing-wave X-ray fluorescence (SWXF) to localize chemical elements in solid-supported lipid and protein layers with near-Ångstrom precision. The technique complements traditional specular reflectometry experiments that merely yield the layers' global density profiles. While earlier work mostly focused on relatively heavy elements, typically metal ions, we show that it is also possible to determine the position of the comparatively light elements S and P, which are found in the most abundant classes of biomolecules and are therefore particularly important. With that, we overcome the need of artificial heavy atom labels, the main obstacle to a broader application of high-resolution SWXF in the fields of biology and soft matter. This work may thus constitute the basis for the label-free, element-specific structural investigation of complex biomolecular layers and biological surfaces.

  14. Electron-stimulated desorption of cesium atoms from cesium layers adsorbed on gold-covered tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Ageev, V N; Kuznetsov, Yu A; Potekhina, N D, E-mail: kuznets@ms.ioffe.r [A F Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021, St Petersburg (Russian Federation)

    2010-03-03

    The electron-stimulated desorption (ESD) yields and energy distributions (ED) for neutral cesium atoms have been measured from cesium layers adsorbed on a gold-covered tungsten surface as a function of electron energy, gold film thickness, cesium coverage and substrate temperature. The measurements have been carried out using a time-of-flight method and surface ionization detector in the temperature range 160-300 K. A measurable ESD yield for Cs atoms is observed only after deposition of more than one monolayer of gold and cesium on a tungsten surface at a temperature T = 300 K, which is accompanied by the formation of a CsAu semiconductor film covered with a cesium atom monolayer. The Cs atom ESD yield as a function of incident electron energy has a resonant character and consists of two peaks, the appearance of which depends on both electron energy and substrate temperature. The first peak has an appearance threshold at an electron energy of 57 eV and a substrate temperature of 300 K that is due to Au 5p{sub 3/2} core level excitation in the substrate. The second peak appears at an electron energy of 24 eV and a substrate temperature of 160 K. It is associated with a Cs 5s core level excitation in the Cs adsorbed layer. The Au 5p{sub 3/2} level excitation corresponds to a single broad peak in the ED with a maximum at a kinetic energy of 0.45 eV at a substrate temperature T = 300 K, which is split into two peaks with maxima at kinetic energies of 0.36 and 0.45 eV at a substrate temperature of 160 K, associated with different Cs atom ESD channels. The Cs 5s level excitation leads to an ED for Cs atoms with a maximum at a kinetic energy of approx 0.57 eV which exists only at T < 240 K and low Cs concentrations. The mechanisms for all the Cs atom ESD channels are proposed and compared with the Na atom ESD channels in the Na-Au-W system.

  15. Characterization of reclaimed GaAs substrates and investigation of reuse for thin film InGaAlP LED epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Englhard, M.; Klemp, C.; Behringer, M.; Rudolph, A. [OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany); Skibitzki, O.; Zaumseil, P. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Institute of Physics and Chemistry, BTU Cottbus-Senftenberg, Konrad-Zuse-Str. 1, 03046 Cottbus (Germany)

    2016-07-28

    This study reports a method to reuse GaAs substrates with a batch process for thin film light emitting diode (TF-LED) production. The method is based on an epitaxial lift-off technique. With the developed reclaim process, it is possible to get an epi-ready GaAs surface without additional time-consuming and expensive grinding/polishing processes. The reclaim and regrowth process was investigated with a one layer epitaxial test structure. The GaAs surface was characterized by an atomic force microscope directly after the reclaim process. The crystal structure of the regrown In{sub 0.5}(Ga{sub 0.45}Al{sub 0.55}){sub 0.5}P (Q{sub 55}) layer was investigated by high resolution x-ray diffraction and scanning transmission electron microscopy. In addition, a complete TF-LED grown on reclaimed GaAs substrates was electro-optically characterized on wafer level. The crystal structure of the epitaxial layers and the performance of the TF-LED grown on reclaimed substrates are not influenced by the developed reclaim process. This process would result in reducing costs for LEDs and reducing much arsenic waste for the benefit of a green semiconductor production.

  16. Atmospheric spatial atomic layer deposition of Zn(O,S) buffer layer for Cu(In,Ga)Se2 solar cells

    NARCIS (Netherlands)

    Frijters, C.H.; Poodt, P.; Illeberi, A.

    2016-01-01

    Zinc oxysulfide has been grown by spatial atomic layer deposition (S-ALD) and successfully applied as buffer layer in Cu(In, Ga)Se2 (CIGS) solar cells. S-ALD combines high deposition rates (up to nm/s) with the advantages of conventional ALD, i.e. excellent control of film composition and superior

  17. UV protective zinc oxide coating for biaxially oriented polypropylene packaging film by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lahtinen, Kimmo, E-mail: kimmo.lahtinen@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Kääriäinen, Tommi, E-mail: tommi.kaariainen@colorado.edu [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Johansson, Petri, E-mail: petri.johansson@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Kotkamo, Sami, E-mail: sami.kotkamo@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Seppänen, Tarja, E-mail: tarja.seppanen@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Cameron, David C., E-mail: david.cameron@miktech.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland)

    2014-11-03

    Biaxially oriented polypropylene (BOPP) packaging film was coated with zinc oxide (ZnO) coatings by atomic layer deposition (ALD) in order to protect the film from UV degradation. The coatings were made at a process temperature of 100 °C using diethylzinc and water as zinc and oxygen precursors, respectively. The UV protective properties of the coatings were tested by using UV–VIS and infrared spectrometry, differential scanning calorimetry (DSC) and a mechanical strength tester, which characterised the tensile and elastic properties of the film. The results obtained with 36 and 67 nm ZnO coatings showed that the ZnO UV protective layer is able to provide a significant decrease in photodegradation of the BOPP film under UV exposure. While the uncoated BOPP film suffered a complete degradation after a 4-week UV exposure, the 67 nm ZnO coated BOPP film was able to preserve half of its original tensile strength and 1/3 of its elongation at break after a 6-week exposure period. The infrared analysis and DSC measurements further proved the UV protection of the ZnO coatings. The results show that a nanometre scale ZnO coating deposited by ALD is a promising option when a transparent UV protection layer is sought for polymer substrates. - Highlights: • Atomic layer deposited zinc oxide coatings were used as UV protection layers. • Biaxially oriented polypropylene (BOPP) film was well protected against UV light. • Formation of UV degradation products in BOPP was significantly reduced. • Mechanical properties of the UV exposed BOPP film were significantly improved.

  18. Triboelectric charge generation by semiconducting SnO2 film grown by atomic layer deposition

    Science.gov (United States)

    Lee, No Ho; Yoon, Seong Yu; Kim, Dong Ha; Kim, Seong Keun; Choi, Byung Joon

    2017-07-01

    Improving the energy harvesting efficiency of triboelectric generators (TEGs) requires exploring new types of materials that can be used, and understanding their properties. In this study, we have investigated semiconducting SnO2 thin films as friction layers in TEGs, which has not been explored thus far. Thin films of SnO2 with various thicknesses were grown by atomic layer deposition on Si substrates. Either polymer or glass was used as counter friction layers. Vertical contact/separation mode was utilized to evaluate the TEG efficiency. The results indicate that an increase in the SnO2 film thickness from 5 to 25 nm enhances the triboelectric output voltage of the TEG. Insertion of a 400-nm-thick Pt sub-layer between the SnO2 film and Si substrate further increased the output voltage up to 120 V in a 2 cm × 2 cm contact area, while the enhancement was cancelled out by inserting a 10-nm-thick insulating Al2O3 film between SnO2 and Pt films. These results indicate that n-type semiconducting SnO2 films can provide triboelectric charge to counter-friction layers in TEGs.[Figure not available: see fulltext.

  19. Role of atomic layer deposited aluminum oxide as oxidation barrier for silicon based materials

    Energy Technology Data Exchange (ETDEWEB)

    Fiorentino, Giuseppe, E-mail: g.fiorentino@tudelft.nl; Morana, Bruno [Department of Microelectronic, Delft University of Technology, Feldmannweg 17, 2628 CT Delft (Netherlands); Forte, Salvatore [Department of Electronic, University of Naples Federico II, Piazzale Tecchio, 80125 Napoli (Italy); Sarro, Pasqualina Maria [Department of Microelectronic, Delft University of Technology, Feldmannweg 17, 2628 CT, Delft (Netherlands)

    2015-01-15

    In this paper, the authors study the protective effect against oxidation of a thin layer of atomic layer deposited (ALD) aluminum oxide (Al{sub 2}O{sub 3}). Nitrogen doped silicon carbide (poly-SiC:N) based microheaters coated with ALD Al{sub 2}O{sub 3} are used as test structure to investigate the barrier effect of the alumina layers to oxygen and water vapor at very high temperature (up to 1000 °C). Different device sets have been fabricated changing the doping levels, to evaluate possible interaction between the dopants and the alumina layer. The as-deposited alumina layer morphology has been evaluated by means of AFM analysis and compared to an annealed sample (8 h at 1000 °C) to estimate the change in the grain structure and the film density. The coated microheaters are subjected to very long oxidation time in dry and wet environment (up to 8 h at 900 and 1000 °C). By evaluating the electrical resistance variation between uncoated reference devices and the ALD coated devices, the oxide growth on the SiC is estimated. The results show that the ALD alumina coating completely prevents the oxidation of the SiC up to 900 °C in wet environment, while an oxide thickness reduction of 50% is observed at 1000 °C compared to uncoated devices.

  20. Atomic Layer-Deposited TiO2 Coatings on NiTi Surface

    Science.gov (United States)

    Vokoun, D.; Racek, J.; Kadeřávek, L.; Kei, C. C.; Yu, Y. S.; Klimša, L.; Šittner, P.

    2018-02-01

    NiTi shape-memory alloys may release poisonous Ni ions at the alloys' surface. In an attempt to prepare a well-performing surface layer on an NiTi sample, the thermally grown TiO2 layer, which formed during the heat treatment of NiTi, was removed and replaced with a new TiO2 layer prepared using the atomic layer deposition (ALD) method. Using x-ray photoelectron spectroscopy, it was found that the ALD layer prepared at as low a temperature as 100 °C contained Ti in oxidation states + 4 and + 3. As for static corrosion properties of the ALD-coated NiTi samples, they further improved compared to those covered by thermally grown oxide. The corrosion rate of samples with thermally grown oxide was 1.05 × 10-5 mm/year, whereas the corrosion rate of the ALD-coated samples turned out to be about five times lower. However, cracking of the ALD coating occurred at about 1.5% strain during the superelastic mechanical loading in tension taking place via the propagation of a localized martensite band.

  1. Atomic layer deposition for photovoltaics: applications and prospects for solar cell manufacturing

    International Nuclear Information System (INIS)

    Van Delft, J A; Garcia-Alonso, D; Kessels, W M M

    2012-01-01

    Atomic layer deposition (ALD) is a vapour-phase deposition technique capable of depositing high quality, uniform and conformal thin films at relatively low temperatures. These outstanding properties can be employed to face processing challenges for various types of next-generation solar cells; hence, ALD for photovoltaics (PV) has attracted great interest in academic and industrial research in recent years. In this review, the recent progress of ALD layers applied to various solar cell concepts and their future prospects are discussed. Crystalline silicon (c-Si), copper indium gallium selenide (CIGS) and dye-sensitized solar cells (DSSCs) benefit from the application of ALD surface passivation layers, buffer layers and barrier layers, respectively. ALD films are also excellent moisture permeation barriers that have been successfully used to encapsulate flexible CIGS and organic photovoltaic (OPV) cells. Furthermore, some emerging applications of the ALD method in solar cell research are reviewed. The potential of ALD for solar cells manufacturing is discussed, and the current status of high-throughput ALD equipment development is presented. ALD is on the verge of being introduced in the PV industry and it is expected that it will be part of the standard solar cell manufacturing equipment in the near future. (paper)

  2. Tuning the mechanical properties of vertical graphene sheets through atomic layer deposition

    International Nuclear Information System (INIS)

    Davami, Keivan; Jiang, Yijie; Cortes, John; Lin, Chen; Turner, Kevin T; Bargatin, Igor; Shaygan, Mehrdad

    2016-01-01

    We report the fabrication and characterization of graphene nanostructures with mechanical properties that are tuned by conformal deposition of alumina. Vertical graphene (VG) sheets, also called carbon nanowalls (CNWs), were grown on copper foil substrates using a radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique and conformally coated with different thicknesses of alumina (Al_2O_3) using atomic layer deposition (ALD). Nanoindentation was used to characterize the mechanical properties of pristine and alumina-coated VG sheets. Results show a significant increase in the effective Young’s modulus of the VG sheets with increasing thickness of deposited alumina. Deposition of only a 5 nm thick alumina layer on the VG sheets nearly triples the effective Young’s modulus of the VG structures. Both energy absorption and strain recovery were lower in VG sheets coated with alumina than in pure VG sheets (for the same peak force). This may be attributed to the increase in bending stiffness of the VG sheets and the creation of connections between the sheets after ALD deposition. These results demonstrate that the mechanical properties of VG sheets can be tuned over a wide range through conformal atomic layer deposition, facilitating the use of VG sheets in applications where specific mechanical properties are needed. (paper)

  3. Ionic double layer of atomically flat gold formed on mica templates

    International Nuclear Information System (INIS)

    Chilcott, Terry C.; Wong, Elicia L.S.; Coster, Hans G.L.; Coster, Adelle C.F.; James, Michael

    2009-01-01

    Electrical impedance spectroscopy characterisations of gold surfaces formed on mica templates in contact with potassium chloride electrolytes were performed at the electric potential of zero charge over a frequency range of 6 x 10 -3 to 100 x 10 3 Hz. They revealed constant-phase-angle (CPA) behaviour with a frequency exponent value of 0.96 for surfaces that were also characterised as atomically flat using atomic force microscopy (AFM). As the frequency exponent value was only marginally less than unity, the CPA behaviour yielded a realistic estimate for the capacitance of the ionic double layer. The retention of the CPA behaviour was attributed to specific adsorption of chloride ions which was detected as an adsorption conductance element in parallel with the CPA impedance element. Significant variations in the ionic double layer capacitance as well as the adsorption conductance were observed for electrolyte concentrations ranging from 33 μM to 100 mM, but neither of these variations correlated with concentration. This is consistent with the electrical properties of the interface deriving principally from the inner or Stern region of the double layer.

  4. Observation of anomalous Stokes versus anti-Stokes ratio in MoTe2 atomic layers

    Science.gov (United States)

    Goldstein, Thomas; Chen, Shao-Yu; Xiao, Di; Ramasubramaniam, Ashwin; Yan, Jun

    We grow hexagonal molybdenum ditelluride (MoTe2), a prototypical transition metal dichalcogenide (TMDC) semiconductor, with chemical vapor transport methods and investigate its atomic layers with Stokes and anti-Stokes Raman scattering. We report observation of all six types of zone center optical phonons. Quite remarkably, the anti-Stokes Raman intensity of the low energy layer-breathing mode becomes more intense than the Stokes peak under certain experimental conditions, creating an illusion of 'negative temperature'. This effect is tunable, and can be switched from anti-Stokes enhancement to suppression by varying the excitation wavelength. We interpret this observation to be a result of resonance effects arising from the C excitons in the vicinity of the Brillouin zone center, which are robust even for multiple layers of MoTe2. The intense anti-Stokes Raman scattering provides a cooling channel for the crystal and opens up opportunities for laser cooling of atomically thin TMDC semiconductor devices. Supported by the University of Massachusetts Amherst, the National Science Foundation Center for Hierarchical Manufacturing (CMMI-1025020) and Office of Emerging Frontiers in Research and Innovation (EFRI-1433496).

  5. Atomic Layer Deposition of SnO2 on MXene for Li-Ion Battery Anodes

    KAUST Repository

    Ahmed, Bilal

    2017-02-24

    In this report, we show that oxide battery anodes can be grown on two-dimensional titanium carbide sheets (MXenes) by atomic layer deposition. Using this approach, we have fabricated a composite SnO2/MXene anode for Li-ion battery applications. The SnO2/MXene anode exploits the high Li-ion capacity offered by SnO2, while maintaining the structural and mechanical integrity by the conductive MXene platform. The atomic layer deposition (ALD) conditions used to deposit SnO2 on MXene terminated with oxygen, fluorine, and hydroxyl-groups were found to be critical for preventing MXene degradation during ALD. We demonstrate that SnO2/MXene electrodes exhibit excellent electrochemical performance as Li-ion battery anodes, where conductive MXene sheets act to buffer the volume changes associated with lithiation and delithiation of SnO2. The cyclic performance of the anodes is further improved by depositing a very thin passivation layer of HfO2, in the same ALD reactor, on the SnO2/MXene anode. This is shown by high-resolution transmission electron microscopy to also improve the structural integrity of SnO2 anode during cycling. The HfO2 coated SnO2/MXene electrodes demonstrate a stable specific capacity of 843 mAh/g when used as Li-ion battery anodes.

  6. The Electrochemical Atomic Layer Deposition of Pt and Pd nanoparticles on Ni foam for the electrooxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2012-10-01

    Full Text Available Electrodeposition of Pt and Pd metal by surface limited redox replacement reactions was performed using the electrochemical atomic layer deposition. Carbon paper and Ni foam were used as substrates for metal deposition. Supported Pt and Pd...

  7. P-type Ge epitaxy on GaAs (100) substrate grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y.J.; Chia, C.K.; Liu, H.F.; Wong, L.M.; Chai, J.W.; Chi, D.Z.; Wang, S.J., E-mail: sj-wang@imre.a-star.edu.sg

    2016-07-15

    Highlights: • The heterogeneous integration of p-Ge/GaAs by MOCVD indicates significance for the application in optoelectronic devices such as p-MOSFET, dual band photodetector, etc. • Many undesired pillar-structures were observed on the p-Ge epilayers and we found that the cause of the pillar-like structures was related to the Ge-Ga dimers formed during the growth. • We found that a GaAs substrate with fewer Ga or Ge danglings was helpful in suppressing the formation of the unwanted pillar-like structures and thus obtaining high quality p-Ge epilayers. - Abstract: In this work, Ga-doped Geranium (Ge) films have been grown on GaAs (100) substrates by metal-organic chemical vapor deposition (MOCVD). Undesired pillar structures have been observed on the epilayers prepared at relatively lower temperatures. Energy dispersive X-ray spectroscopy (EDX) indicated that the pillars are mainly consisted of Ga atoms, which is totally different from that of the Ge film. It was demonstrated that the pillar structures could be reduced by simply raising the growth temperature while keeping the other growth conditions unchanged. In this regard, the growth mechanism of the pillars was related to the Ge-Ga dimers formed during the growth of p-Ge films. By further studying the influence of a GaAs or Ge buffer layer on the growth of p-Ge layers, we found that the GaAs substrate with lower density of Ga or Ge dangling bonds was helpful in suppressing the formation of the undesired pillar structures.

  8. Pt–Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

    International Nuclear Information System (INIS)

    Pardon, Gaspard; Gatty, Hithesh K; Stemme, Göran; Wijngaart, Wouter van der; Roxhed, Niclas

    2013-01-01

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al 2 O 3 ) on Pt in nanopores to form a metal–insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al 2 O 3 layer on such a Pt film forms a metal–insulator–electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al 2 O 3 using ALD. (paper)

  9. Pt-Al{sub 2}O{sub 3} dual layer atomic layer deposition coating in high aspect ratio nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Pardon, Gaspard; Gatty, Hithesh K; Stemme, Goeran; Wijngaart, Wouter van der; Roxhed, Niclas [KTH Royal Institute of Technology, School of Electrical Engineering, Micro and Nanosystems, Osquldas Vaeg 10, SE-10044 Stockholm (Sweden)

    2013-01-11

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al{sub 2}O{sub 3}) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al{sub 2}O{sub 3} layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 {mu}m thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al{sub 2}O{sub 3} using ALD. (paper)

  10. Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

    Science.gov (United States)

    Pardon, Gaspard; Gatty, Hithesh K.; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

    2013-01-01

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

  11. Coloration of metallic and/or ceramic surfaces obtained by atomic layer deposited nano-coatings

    International Nuclear Information System (INIS)

    Guzman, L.; Vettoruzzo, F.; Laidani, N.

    2016-01-01

    By depositing single layer coatings by means of physical vapor techniques, tailoring of their coloration is generally complex because a given color can be obtained only by very high composition control. Physical vapor deposition (PVD) processes are expensive and cannot be easily used for obtaining conformal coating on three-dimensional objects. Moreover PVD coatings exhibit intrinsic defects (columnar structures, pores) that affect their functional properties and applications such as barrier layers. Atomic layer deposition (ALD) technology delivers conformal coatings on different materials with very low defectiveness. A straightforward coloration can be obtained by a combination of two types of layers with different refraction index, deposited to high thickness precision. Computer simulation studies were performed to design the thickness and architecture of multilayer structures, to a total thickness of approximately 100 nm, suitable to modify the typical coloration of some materials, without altering their other physical and chemical properties. The most promising nano-layered structures were then deposited by ALD and tested with regard to their optical properties. Their total thicknesses were specified in such a way to be technically feasible and compatible with future industrial production. The materials employed in this study to build the optical coatings, are two oxides (Al_2O_3, TiO_2) deposited at 120 °C and two nitrides (AlN, TiN), which need a deposition temperature of 400 °C. The possibility of using such modern deposition technology for esthetic and decorative purposes, while maintaining the functional properties, opens perspectives of industrial applications. - Highlights: • Computer simulation is done to design multilayers made of Al_2O_3, TiO_2, AlN, and TiN. • Total thickness (< 120 nm) is specified to be compatible with industrial production. • The most promising nano-layered structures are then produced and optically tested. • An

  12. Role of plasma enhanced atomic layer deposition reactor wall conditions on radical and ion substrate fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Sowa, Mark J., E-mail: msowa@ultratech.com [Ultratech/Cambridge NanoTech, 130 Turner Street, Building 2, Waltham, Massachusetts 02453 (United States)

    2014-01-15

    Chamber wall conditions, such as wall temperature and film deposits, have long been known to influence plasma source performance on thin film processing equipment. Plasma physical characteristics depend on conductive/insulating properties of chamber walls. Radical fluxes depend on plasma characteristics as well as wall recombination rates, which can be wall material and temperature dependent. Variations in substrate delivery of plasma generated species (radicals, ions, etc.) impact the resulting etch or deposition process resulting in process drift. Plasma enhanced atomic layer deposition is known to depend strongly on substrate radical flux, but film properties can be influenced by other plasma generated phenomena, such as ion bombardment. In this paper, the chamber wall conditions on a plasma enhanced atomic layer deposition process are investigated. The downstream oxygen radical and ion fluxes from an inductively coupled plasma source are indirectly monitored in temperature controlled (25–190 °C) stainless steel and quartz reactors over a range of oxygen flow rates. Etch rates of a photoresist coated quartz crystal microbalance are used to study the oxygen radical flux dependence on reactor characteristics. Plasma density estimates from Langmuir probe ion saturation current measurements are used to study the ion flux dependence on reactor characteristics. Reactor temperature was not found to impact radical and ion fluxes substantially. Radical and ion fluxes were higher for quartz walls compared to stainless steel walls over all oxygen flow rates considered. The radical flux to ion flux ratio is likely to be a critical parameter for the deposition of consistent film properties. Reactor wall material, gas flow rate/pressure, and distance from the plasma source all impact the radical to ion flux ratio. These results indicate maintaining chamber wall conditions will be important for delivering consistent results from plasma enhanced atomic layer deposition

  13. TiO2 nanofiber solid-state dye sensitized solar cells with thin TiO2 hole blocking layer prepared by atomic layer deposition

    International Nuclear Information System (INIS)

    Li, Jinwei; Chen, Xi; Xu, Weihe; Nam, Chang-Yong; Shi, Yong

    2013-01-01

    We incorporated a thin but structurally dense TiO 2 layer prepared by atomic layer deposition (ALD) as an efficient hole blocking layer in the TiO 2 nanofiber based solid-state dye sensitized solar cell (ss-DSSC). The nanofiber ss-DSSCs having ALD TiO 2 layers displayed increased open circuit voltage, short circuit current density, and power conversion efficiency compared to control devices with blocking layers prepared by spin-coating liquid TiO 2 precursor. We attribute the improved photovoltaic device performance to the structural integrity of ALD-coated TiO 2 layer and consequently enhanced hole blocking effect that results in reduced dark leakage current and increased charge carrier lifetime. - Highlights: • TiO 2 blocking locking layer prepared by atomic layer deposition (ALD) method. • ALD-coated TiO 2 layer enhanced hole blocking effect. • ALD blocking layer improved the voltage, current and efficiency. • ALD blocking layer reduced dark leakage current and increased electron lifetime

  14. TiO{sub 2} nanofiber solid-state dye sensitized solar cells with thin TiO{sub 2} hole blocking layer prepared by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jinwei; Chen, Xi; Xu, Weihe [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Nam, Chang-Yong, E-mail: cynam@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973 (United States); Shi, Yong, E-mail: Yong.Shi@stevens.edu [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2013-06-01

    We incorporated a thin but structurally dense TiO{sub 2} layer prepared by atomic layer deposition (ALD) as an efficient hole blocking layer in the TiO{sub 2} nanofiber based solid-state dye sensitized solar cell (ss-DSSC). The nanofiber ss-DSSCs having ALD TiO{sub 2} layers displayed increased open circuit voltage, short circuit current density, and power conversion efficiency compared to control devices with blocking layers prepared by spin-coating liquid TiO{sub 2} precursor. We attribute the improved photovoltaic device performance to the structural integrity of ALD-coated TiO{sub 2} layer and consequently enhanced hole blocking effect that results in reduced dark leakage current and increased charge carrier lifetime. - Highlights: • TiO{sub 2} blocking locking layer prepared by atomic layer deposition (ALD) method. • ALD-coated TiO{sub 2} layer enhanced hole blocking effect. • ALD blocking layer improved the voltage, current and efficiency. • ALD blocking layer reduced dark leakage current and increased electron lifetime.

  15. Improvement and protection of niobium surface superconductivity by atomic layer deposition and heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Proslier, T.; /IIT, Chicago /Argonne; Zasadzinski, J.; /IIT, Chicago; Moore, J.; Pellin, M.; Elam, J.; /Argonne; Cooley, L.; /Fermilab; Antoine, C.; /Saclay

    2008-11-01

    A method to treat the surface of Nb is described, which potentially can improve the performance of superconducting rf cavities. We present tunneling and x-ray photoemission spectroscopy measurements at the surface of cavity-grade niobium samples coated with a 3 nm alumina overlayer deposited by atomic layer deposition. The coated samples baked in ultrahigh vacuum at low temperature degraded superconducting surface. However, at temperatures above 450 C, the tunneling conductance curves show significant improvements in the superconducting density of states compared with untreated surfaces.

  16. Atomic layer epitaxy of hematite on indium tin oxide for application in solar energy conversion

    Science.gov (United States)

    Martinson, Alex B.; Riha, Shannon; Guo, Peijun; Emery, Jonathan D.

    2016-07-12

    A method to provide an article of manufacture of iron oxide on indium tin oxide for solar energy conversion. An atomic layer epitaxy method is used to deposit an uncommon bixbytite-phase iron (III) oxide (.beta.-Fe.sub.2O.sub.3) which is deposited at low temperatures to provide 99% phase pure .beta.-Fe.sub.2O.sub.3 thin films on indium tin oxide. Subsequent annealing produces pure .alpha.-Fe.sub.2O.sub.3 with well-defined epitaxy via a topotactic transition. These highly crystalline films in the ultra thin film limit enable high efficiency photoelectrochemical chemical water splitting.

  17. Quantum chemical study of the elementary reactions in zirconium oxide atomic layer deposition

    International Nuclear Information System (INIS)

    Widjaja, Yuniarto; Musgrave, Charles B.

    2002-01-01

    Elementary reactions in atomic layer deposition of zirconia using zirconium tetrachloride and water are investigated using the density functional theory. The atomistic mechanisms of the two deposition half cycles on the Zr-OH and Zr-Cl surface sites are investigated. Both half reactions proceed through the formation of stable intermediates, resulting in high barriers for HCl formation. We find that the intermediate stability is lowered as the surface temperature is raised. However, increasing temperature also increases the dissociation free-energy barrier, which in turn results in increased desorption of adsorbed precursors

  18. Metallic nanoparticle-based strain sensors elaborated by atomic layer deposition

    Science.gov (United States)

    Puyoo, E.; Malhaire, C.; Thomas, D.; Rafaël, R.; R'Mili, M.; Malchère, A.; Roiban, L.; Koneti, S.; Bugnet, M.; Sabac, A.; Le Berre, M.

    2017-03-01

    Platinum nanoparticle-based strain gauges are elaborated by means of atomic layer deposition on flexible polyimide substrates. Their electro-mechanical response is tested under mechanical bending in both buckling and conformational contact configurations. A maximum gauge factor of 70 is reached at a strain level of 0.5%. Although the exponential dependence of the gauge resistance on strain is attributed to the tunneling effect, it is shown that the majority of the junctions between adjacent Pt nanoparticles are in a short circuit state. Finally, we demonstrate the feasibility of an all-plastic pressure sensor integrating Pt nanoparticle-based strain gauges in a Wheatstone bridge configuration.

  19. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    Science.gov (United States)

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.

  20. Growth and characterization of titanium oxide by plasma enhanced atomic layer deposition

    KAUST Repository

    Zhao, Chao

    2013-09-01

    The growth of TiO2 films by plasma enhanced atomic layer deposition using Star-Ti as a precursor has been systematically studied. The conversion from amorphous to crystalline TiO2 was observed either during high temperature growth or annealing process of the films. The refractive index and bandgap of TiO2 films changed with the growth and annealing temperatures. The optimization of the annealing conditions for TiO2 films was also done by morphology and density studies. © 2013 Elsevier B.V. All rights reserved.

  1. (Invited) Atomic Layer Deposition for Novel Dye-Sensitized Solar Cells

    KAUST Repository

    Tétreault, Nicolas

    2011-01-01

    Herein we present the latest fabrication and characterization techniques for atomic layer deposition of Al 2O 3, ZnO, SnO 2, Nb 2O 5, HfO 2, Ga 2O 3 and TiO 2 for research on dye-sensitized solar cell. In particular, we review the fabrication of state-of-the-art 3D host-passivation-guest photoanodes and ZnO nanowires as well as characterize the deposited thin films using spectroscopic ellipsometry, X-ray diffraction, Hall effect, J-V curves and electrochemical impedance spectroscopy. ©The Electrochemical Society.

  2. Implantation annealing in GaAs by incoherent light

    International Nuclear Information System (INIS)

    Davies, D.E.; Ryan, T.G.; Soda, K.J.; Comer, J.J.

    1983-01-01

    Implanted GaAs has been successfully activated through concentrating the output of quartz halogen lamps to anneal in times of the order of 1 sec. The resulting layers are not restricted by the reduced mobilities and thermal instabilities of laser annealed GaAs. Better activation can be obtained than with furnace annealing but this generally requires maximum temperatures >= 1050degC. (author)

  3. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan; Chang, Chih-Yuan S.; Ghosh, Ram Krishna; Li, Jie; Zhu, Hui; Addou, Rafik; Diaconescu, Bogdan; Ohta, Taisuke; Peng, Xin; Lu, Ning; Kim, Moon J.; Robinson, Jeremy T.; Wallace, Robert M; Mayer, Theresa S.; Datta, Suman; Li, Lain-Jong; Robinson, Joshua A.

    2014-01-01

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green's function (NEGF).

  4. TiO2 nanosheets synthesized by atomic layer deposition for photocatalysis

    Directory of Open Access Journals (Sweden)

    Riyanto Edy

    2016-10-01

    Full Text Available Two-dimensional TiO2 nanosheets were synthesized by atomic layer deposition (ALD on dissolvable sacrificial polymer layer. The photocatalytic performance of free-standing TiO2 nanosheets prepared with different numbers of ALD cycles (100, 300, 500, and 1000 were investigated by evaluating the degradation rates of methyl orange solutions. It is shown that the photocatalytic activity increases due to Ti3+ defect and the locally ordered structures in amorphous TiO2 nanosheets. The difference in the surface areas of nanosheets may also play a crucial role in the photocatalytic activity. The results obtained in this work can have potential applications in fields like water splitting and dye-sensitized solar cells.

  5. Intrinsic electron traps in atomic-layer deposited HfO{sub 2} insulators

    Energy Technology Data Exchange (ETDEWEB)

    Cerbu, F.; Madia, O.; Afanas' ev, V. V.; Houssa, M.; Stesmans, A. [Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, 3001 Leuven (Belgium); Andreev, D. V. [Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, 3001 Leuven (Belgium); Bauman Moscow State Technical University—Kaluga Branch, 248000 Kaluga, Moscow obl. (Russian Federation); Fadida, S.; Eizenberg, M. [Department of Materials Science and Engineering, Technion-Israel Institute of Technology, 32000 Haifa (Israel); Breuil, L. [imec, 3001 Leuven (Belgium); Lisoni, J. G. [imec, 3001 Leuven (Belgium); Institute of Physics and Mathematics, Faculty of Science, Universidad Austral de Chile, Valdivia (Chile); Kittl, J. A. [Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, 3001 Leuven (Belgium); Advanced Logic Lab, Samsung Semiconductor, Inc., Austin, 78754 Texas (United States); Strand, J.; Shluger, A. L. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

    2016-05-30

    Analysis of photodepopulation of electron traps in HfO{sub 2} films grown by atomic layer deposition is shown to provide the trap energy distribution across the entire oxide bandgap. The presence is revealed of two kinds of deep electron traps energetically distributed at around E{sub t} ≈ 2.0 eV and E{sub t} ≈ 3.0 eV below the oxide conduction band. Comparison of the trapped electron energy distributions in HfO{sub 2} layers prepared using different precursors or subjected to thermal treatment suggests that these centers are intrinsic in origin. However, the common assumption that these would implicate O vacancies cannot explain the charging behavior of HfO{sub 2}, suggesting that alternative defect models should be considered.

  6. The possibility of multi-layer nanofabrication via atomic force microscope-based pulse electrochemical nanopatterning

    Science.gov (United States)

    Kim, Uk Su; Morita, Noboru; Lee, Deug Woo; Jun, Martin; Park, Jeong Woo

    2017-05-01

    Pulse electrochemical nanopatterning, a non-contact scanning probe lithography process using ultrashort voltage pulses, is based primarily on an electrochemical machining process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through non-contact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration. Additionally, protruding nanoscale oxides were removed completely by simple chemical etching, showing a depressed pattern on the sample substrate surface. Nanoscale two-dimensional oxides, prepared by a localized electrochemical reaction, can be defined easily by controlling physical and electrical variables, before proceeding further to a layer-by-layer nanofabrication process.

  7. Atomic layer deposited TiO{sub 2} for implantable brain-chip interfacing devices

    Energy Technology Data Exchange (ETDEWEB)

    Cianci, E., E-mail: elena.cianci@mdm.imm.cnr.it [Laboratorio MDM, IMM-CNR, 20864 Agrate Brianza (MB) (Italy); Lattanzio, S. [Istituto di Fisiologia, Dipartimento di Anatomia Umana e Fisiologia, Universita di Padova, 35131 Padova (Italy); Dipartimento di Ingegneria dell' Informazione, Universita di Padova, 35131 Padova (Italy); Seguini, G. [Laboratorio MDM, IMM-CNR, 20864 Agrate Brianza (Italy); Vassanelli, S. [Istituto di Fisiologia, Dipartimento di Anatomia Umana e Fisiologia, Universita di Padova, 35131 Padova (Italy); Fanciulli, M. [Laboratorio MDM, IMM-CNR, 20864 Agrate Brianza (Italy); Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano-Bicocca, 20126 Milano (Italy)

    2012-05-01

    In this paper we investigated atomic layer deposition (ALD) TiO{sub 2} thin films deposited on implantable neuro-chips based on electrolyte-oxide-semiconductor (EOS) junctions, implementing both efficient capacitive neuron-silicon coupling and biocompatibility for long-term implantable functionality. The ALD process was performed at 295 Degree-Sign C using titanium tetraisopropoxide and ozone as precursors on needle-shaped silicon substrates. Engineering of the capacitance of the EOS junctions introducing a thin Al{sub 2}O{sub 3} buffer layer between TiO{sub 2} and silicon resulted in a further increase of the specific capacitance. Biocompatibility for long-term implantable neuroprosthetic systems was checked upon in-vitro treatment.

  8. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan

    2014-11-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green\\'s function (NEGF).

  9. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Nuri Yazdani

    2014-03-01

    Full Text Available Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD. Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays.

  10. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes.

    Science.gov (United States)

    Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa; Park, Hyung Gyu; Utke, Ivo

    2014-01-01

    Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays.

  11. Atomic layer deposited TiO2 for implantable brain-chip interfacing devices

    International Nuclear Information System (INIS)

    Cianci, E.; Lattanzio, S.; Seguini, G.; Vassanelli, S.; Fanciulli, M.

    2012-01-01

    In this paper we investigated atomic layer deposition (ALD) TiO 2 thin films deposited on implantable neuro-chips based on electrolyte-oxide-semiconductor (EOS) junctions, implementing both efficient capacitive neuron-silicon coupling and biocompatibility for long-term implantable functionality. The ALD process was performed at 295 °C using titanium tetraisopropoxide and ozone as precursors on needle-shaped silicon substrates. Engineering of the capacitance of the EOS junctions introducing a thin Al 2 O 3 buffer layer between TiO 2 and silicon resulted in a further increase of the specific capacitance. Biocompatibility for long-term implantable neuroprosthetic systems was checked upon in-vitro treatment.

  12. Interlayer electron-hole pair multiplication by hot carriers in atomic layer semiconductor heterostructures

    Science.gov (United States)

    Barati, Fatemeh; Grossnickle, Max; Su, Shanshan; Lake, Roger; Aji, Vivek; Gabor, Nathaniel

    Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides provide the opportunity to design novel devices for the study of electron-hole pair multiplication. We report on highly efficient multiplication of interlayer electron-hole pairs at the interface of a tungsten diselenide / molybdenum diselenide heterostructure. Electronic transport measurements of the interlayer current-voltage characteristics indicate that layer-indirect electron-hole pairs are generated by hot electron impact excitation. Our findings, which demonstrate an efficient energy relaxation pathway that competes with electron thermalization losses, make 2D semiconductor heterostructures viable for a new class of hot-carrier energy harvesting devices that exploit layer-indirect electron-hole excitations. SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Air Force Office of Scientific Research.

  13. Coking- and sintering-resistant palladium catalysts achieved through atomic layer deposition.

    Science.gov (United States)

    Lu, Junling; Fu, Baosong; Kung, Mayfair C; Xiao, Guomin; Elam, Jeffrey W; Kung, Harold H; Stair, Peter C

    2012-03-09

    We showed that alumina (Al(2)O(3)) overcoating of supported metal nanoparticles (NPs) effectively reduced deactivation by coking and sintering in high-temperature applications of heterogeneous catalysts. We overcoated palladium NPs with 45 layers of alumina through an atomic layer deposition (ALD) process that alternated exposures of the catalysts to trimethylaluminum and water at 200°C. When these catalysts were used for 1 hour in oxidative dehydrogenation of ethane to ethylene at 650°C, they were found by thermogravimetric analysis to contain less than 6% of the coke formed on the uncoated catalysts. Scanning transmission electron microscopy showed no visible morphology changes after reaction at 675°C for 28 hours. The yield of ethylene was improved on all ALD Al(2)O(3) overcoated Pd catalysts.

  14. Atomic layer deposition of Al-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro [Department of Chemistry, Aalto University, FI-00076 Aalto (Finland); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2013-01-15

    Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

  15. Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics.

    Science.gov (United States)

    Wu, Wenzhuo; Wang, Lei; Li, Yilei; Zhang, Fan; Lin, Long; Niu, Simiao; Chenet, Daniel; Zhang, Xian; Hao, Yufeng; Heinz, Tony F; Hone, James; Wang, Zhong Lin

    2014-10-23

    The piezoelectric characteristics of nanowires, thin films and bulk crystals have been closely studied for potential applications in sensors, transducers, energy conversion and electronics. With their high crystallinity and ability to withstand enormous strain, two-dimensional materials are of great interest as high-performance piezoelectric materials. Monolayer MoS2 is predicted to be strongly piezoelectric, an effect that disappears in the bulk owing to the opposite orientations of adjacent atomic layers. Here we report the first experimental study of the piezoelectric properties of two-dimensional MoS2 and show that cyclic stretching and releasing of thin MoS2 flakes with an odd number of atomic layers produces oscillating piezoelectric voltage and current outputs, whereas no output is observed for flakes with an even number of layers. A single monolayer flake strained by 0.53% generates a peak output of 15 mV and 20 pA, corresponding to a power density of 2 mW m(-2) and a 5.08% mechanical-to-electrical energy conversion efficiency. In agreement with theoretical predictions, the output increases with decreasing thickness and reverses sign when the strain direction is rotated by 90°. Transport measurements show a strong piezotronic effect in single-layer MoS2, but not in bilayer and bulk MoS2. The coupling between piezoelectricity and semiconducting properties in two-dimensional nanomaterials may enable the development of applications in powering nanodevices, adaptive bioprobes and tunable/stretchable electronics/optoelectronics.

  16. Consequences of atomic layer etching on wafer scale uniformity in inductively coupled plasmas

    Science.gov (United States)

    Huard, Chad M.; Lanham, Steven J.; Kushner, Mark J.

    2018-04-01

    Atomic layer etching (ALE) typically divides the etching process into two self-limited reactions. One reaction passivates a single layer of material while the second preferentially removes the passivated layer. As such, under ideal conditions the wafer scale uniformity of ALE should be independent of the uniformity of the reactant fluxes onto the wafers, provided all surface reactions are saturated. The passivation and etch steps should individually asymptotically saturate after a characteristic fluence of reactants has been delivered to each site. In this paper, results from a computational investigation are discussed regarding the uniformity of ALE of Si in Cl2 containing inductively coupled plasmas when the reactant fluxes are both non-uniform and non-ideal. In the parameter space investigated for inductively coupled plasmas, the local etch rate for continuous processing was proportional to the ion flux. When operated with saturated conditions (that is, both ALE steps are allowed to self-terminate), the ALE process is less sensitive to non-uniformities in the incoming ion flux than continuous etching. Operating ALE in a sub-saturation regime resulted in less uniform etching. It was also found that ALE processing with saturated steps requires a larger total ion fluence than continuous etching to achieve the same etch depth. This condition may result in increased resist erosion and/or damage to stopping layers using ALE. While these results demonstrate that ALE provides increased etch depth uniformity, they do not show an improved critical dimension uniformity in all cases. These possible limitations to ALE processing, as well as increased processing time, will be part of the process optimization that includes the benefits of atomic resolution and improved uniformity.

  17. Low-temperature atomic layer deposition of MgO thin films on Si

    International Nuclear Information System (INIS)

    Vangelista, S; Mantovan, R; Lamperti, A; Tallarida, G; Kutrzeba-Kotowska, B; Spiga, S; Fanciulli, M

    2013-01-01

    Magnesium oxide (MgO) films have been grown by atomic layer deposition in the wide deposition temperature window of 80–350 °C by using bis(cyclopentadienyl)magnesium and H 2 O precursors. MgO thin films are deposited on both HF-last Si(1 0 0) and SiO 2 /Si substrates at a constant growth rate of ∼0.12 nm cycle −1 . The structural, morphological and chemical properties of the synthesized MgO thin films are investigated by x-ray reflectivity, grazing incidence x-ray diffraction, time-of-flight secondary ion mass spectrometry and atomic force microscopy measurements. MgO layers are characterized by sharp interface with the substrate and limited surface roughness, besides good chemical uniformity and polycrystalline structure for thickness above 7 nm. C–V measurements performed on Al/MgO/Si MOS capacitors, with MgO in the 4.6–11 nm thickness range, allow determining a dielectric constant (κ) ∼ 11. Co layers are grown by chemical vapour deposition in direct contact with MgO without vacuum-break (base pressure 10 −5 –10 −6  Pa). The as-grown Co/MgO stacks show sharp interfaces and no elements interdiffusion among layers. C–V and I–V measurements have been conducted on Co/MgO/Si MOS capacitors. The dielectric properties of MgO are not influenced by the further process of Co deposition. (paper)

  18. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jixian; Sutherland, Brandon R.; Hoogland, Sjoerd; Fan, Fengjia; Sargent, Edward H., E-mail: ted.sargent@utoronto.ca [Department of Electrical and Computer Engineering, University of Toronto, 10 King' s College Road, Toronto, Ontario M5S 3G4 (Canada); Kinge, Sachin [Advanced Technology, Materials and Research, Research and Development, Hoge Wei 33- Toyota Technical Centre, B-1930 Zaventem (Belgium)

    2015-10-12

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO{sub 2} layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10{sup −2} A W{sup −1} and a shot-derived specific detectivity of 3 × 10{sup 9} Jones at 1530 nm wavelength.

  19. Sealing of hard CrN and DLC coatings with atomic layer deposition.

    Science.gov (United States)

    Härkönen, Emma; Kolev, Ivan; Díaz, Belén; Swiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Marcus, Philippe; Fenker, Martin; Toth, Lajos; Radnoczi, György; Vehkamäki, Marko; Ritala, Mikko

    2014-02-12

    Atomic layer deposition (ALD) is a thin film deposition technique that is based on alternating and saturating surface reactions of two or more gaseous precursors. The excellent conformality of ALD thin films can be exploited for sealing defects in coatings made by other techniques. Here the corrosion protection properties of hard CrN and diamond-like carbon (DLC) coatings on low alloy steel were improved by ALD sealing with 50 nm thick layers consisting of Al2O3 and Ta2O5 nanolaminates or mixtures. In cross sectional images the ALD layers were found to follow the surface morphology of the CrN coatings uniformly. Furthermore, ALD growth into the pinholes of the CrN coating was verified. In electrochemical measurements the ALD sealing was found to decrease the current density of the CrN coated steel by over 2 orders of magnitude. The neutral salt spray (NSS) durability was also improved: on the best samples the appearance of corrosion spots was delayed from 2 to 168 h. On DLC coatings the adhesion of the ALD sealing layers was weaker, but still clear improvement in NSS durability was achieved indicating sealing of the pinholes.

  20. Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study

    Energy Technology Data Exchange (ETDEWEB)

    Bilo, Fabjola [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy); Borgese, Laura, E-mail: laura.borgese@unibs.itl [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy); Prost, Josef; Rauwolf, Mirjam; Turyanskaya, Anna; Wobrauschek, Peter; Kregsamer, Peter; Streli, Christina [Atominstitut, TU Wien, Stadionallee 2, 1020 Vienna (Austria); Pazzaglia, Ugo [Dipartimento Specialità Medico Chirurgiche Sc. Radiol. e Sanità Pubblica, University of Brescia, v.le Europa, 11, 25121 Brescia (Italy); Depero, Laura E. [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy)

    2015-12-30

    Highlights: • Co and Cr migrate from bare alloy implant to the surrounding tissue showing a cluster distribution. • Co and Cr migrate from the TiO{sub 2} coated implant to the surrounding tissue showing a decreasing gradient distribution from the alloy surface. • TiO{sub 2} coating layers obtained by ALD on Co–Cr alloy show a barrier effect for the migration of metals. • The thicker the TiO{sub 2} layer deposited by ALD, the lower the metal migration. • The migration of metals from bare alloy toward the surrounding tissue increases with time. This effect is not detected in the coated samples. - Abstract: We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co–Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO{sub 2}. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO{sub 2} layer, the lower is the metal migration.

  1. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    International Nuclear Information System (INIS)

    Xu, Jixian; Sutherland, Brandon R.; Hoogland, Sjoerd; Fan, Fengjia; Sargent, Edward H.; Kinge, Sachin

    2015-01-01

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO 2 layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10 −2  A W −1 and a shot-derived specific detectivity of 3 × 10 9  Jones at 1530 nm wavelength

  2. Design optimization of GaAs betavoltaic batteries

    International Nuclear Information System (INIS)

    Chen Haiyanag; Jiang Lan; Chen Xuyuan

    2011-01-01

    GaAs junctions are designed and fabricated for betavoltaic batteries. The design is optimized according to the characteristics of GaAs interface states and the diffusion length in the depletion region of GaAs carriers. Under an illumination of 10 mCi cm -2 63 Ni, the open circuit voltage of the optimized batteries is about ∼0.3 V. It is found that the GaAs interface states induce depletion layers on P-type GaAs surfaces. The depletion layer along the P + PN + junction edge isolates the perimeter surface from the bulk junction, which tends to significantly reduce the battery dark current and leads to a high open circuit voltage. The short circuit current density of the optimized junction is about 28 nA cm -2 , which indicates a carrier diffusion length of less than 1 μm. The overall results show that multi-layer P + PN + junctions are the preferred structures for GaAs betavoltaic battery design.

  3. The photovoltaic impact of atomic layer deposited TiO2 interfacial layer on Si-based photodiodes

    Science.gov (United States)

    Karabulut, Abdulkerim; Orak, İkram; Türüt, Abdulmecit

    2018-06-01

    In present work, photocurrent, current-voltage (I-V) and capacitance/conductance-voltage-frequency (C/G-V-f) measurements were analyzed for the photodiode and diode parameters of Al/TiO2/p-Si structure. The TiO2 thin film structure was deposited on p-Si by using atomic layer deposition technique (ALD) and its thickness was about 10 nm. The surface morphology of TiO2 coated on p-Si structure was observed via atomic force microscope (AFM). Barrier height (Φb) and ideality factor (n) values of device were found to be 0.80 eV, 0.70 eV, 0.56 eV and 1.04, 2.24, 10.27 under dark, 10 and 100 mW/cm2, respectively. Some photodiodes parameters such as fill factor (FF), power efficiency (%η), open circuit voltage (Voc), short circuit current (Isc) were obtained from I-V measurement under different light intensity. FF and η were accounted 49.2, 39,0 and 0.05, 0.45 under 10 and 100 mW/cm2 light power intensity, respectively. C-2-V graph was plotted from C-V-f measurements and zero bias voltage (V0), donor concentration (Nd), Fermi energy (EF), barrier height (Φb) and maximum electric field (Em) were determined from C-2-V data for different frequencies. The electrical and photocurrent values demonstrated that it can be used for photodiode, photo detector and photo sensing applications.

  4. Hollow inorganic nanospheres and nanotubes with tunable wall thicknesses by atomic layer deposition on self-assembled polymeric templates

    NARCIS (Netherlands)

    Ras, Robin H. A.; Kemell, Marianna; de Wit, Joost; Ritala, Mikko; ten Brinke, Gerrit; Leskela, Markku; Ikkala, Olli; Leskelä, Markku

    2007-01-01

    The construction of inorganic nanostructures with hollow interiors is demonstrated by coating self-assembled polymeric nano-objects with a thin Al2O3 layer by atomic layer deposition (ALD), followed by removal of the polymer template upon heating. The morphology of the nano-object (i.e., spherical

  5. Tolerance of GaAs as an original substrate for HVPE growth of free standing GaN

    Science.gov (United States)

    Suzuki, Mio; Sato, T.; Suemasu, T.; Hasegawa, F.

    2004-09-01

    In order to investigate possibility of thick GaN growth on a GaAs substrate by halide vapar phase epitaxy (HVPE), GaN was grown on GaAs(111)/Ti wafer with Ti deposited by E-gun. It was found that surface treatment of the GaAs substrate by HF solution deteriorated greatly the tolerence of GaAs and that Ti can protected GaAs from erosion by NH3. By depositing Ti on GaAs(111)A surface, a millor-like GaN layer could be grown at 1000 °C for 1 hour without serious deterioration of the original GaAs substrate. By increasing the growth rate, a thick free standing GaN will be obtained with GaAs as an original substrate in near future.

  6. Tolerance of GaAs as an original substrate for HVPE growth of free standing GaN

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Mio; Sato, T.; Suemasu, T.; Hasegawa, F. [University of Tsukuba, Institute of Applied Physics, Tsukuba, Ibaraki 305-8573 (Japan)

    2004-09-01

    In order to investigate possibility of thick GaN growth on a GaAs substrate by halide vapar phase epitaxy (HVPE), GaN was grown on GaAs(111)/Ti wafer with Ti deposited by E-gun. It was found that surface treatment of the GaAs substrate by HF solution deteriorated greatly the tolerance of GaAs and that Ti can protected GaAs from erosion by NH{sub 3}. By depositing Ti on GaAs(111)A surface, a mirror-like GaN layer could be grown at 1000 C for 1 hour without serious deterioration of the original GaAs substrate. By increasing the growth rate, a thick free standing GaN will be obtained with GaAs as an original substrate in near future. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Atomic-Layer-Deposited AZO Outperforms ITO in High-Efficiency Polymer Solar Cells

    KAUST Repository

    Kan, Zhipeng

    2018-05-11

    Tin-doped indium oxide (ITO) transparent conducting electrodes are widely used across the display industry, and are currently the cornerstone of photovoltaic device developments, taking a substantial share in the manufacturing cost of large-area modules. However, cost and supply considerations are set to limit the extensive use of indium for optoelectronic device applications and, in turn, alternative transparent conducting oxide (TCO) materials are required. In this report, we show that aluminum-doped zinc oxide (AZO) thin films grown by atomic layer deposition (ALD) are sufficiently conductive and transparent to outperform ITO as the cathode in inverted polymer solar cells. Reference polymer solar cells made with atomic-layer-deposited AZO cathodes, PCE10 as the polymer donor and PC71BM as the fullerene acceptor (model systems), reach power conversion efficiencies of ca. 10% (compared to ca. 9% with ITO-coated glass), without compromising other figures of merit. These ALD-grown AZO electrodes are promising for a wide range of optoelectronic device applications relying on TCOs.

  8. MoS2 solid-lubricating film fabricated by atomic layer deposition on Si substrate

    Science.gov (United States)

    Huang, Yazhou; Liu, Lei; Lv, Jun; Yang, Junjie; Sha, Jingjie; Chen, Yunfei

    2018-04-01

    How to reduce friction for improving efficiency in the usage of energy is a constant challenge. Layered material like MoS2 has long been recognized as an effective surface lubricant. Due to low interfacial shear strengths, MoS2 is endowed with nominal frictional coefficient. In this work, MoS2 solid-lubricating film was directly grown by atomic layer deposition (ALD) on Si substrate using MoCl5 and H2S. Various methods were used to observe the grown MoS2 film. Moreover, nanotribological properties of the film were observed by an atomic force microscope (AFM). Results show that MoS2 film can effectively reduce the friction force by about 30-45% under different loads, indicating the huge application value of the film as a solid lubricant. Besides the interlayer-interfaces-sliding, the smaller capillary is another reason why the grown MoS2 film has smaller friction force than that of Si.

  9. Tailoring properties of lossy-mode resonance optical fiber sensors with atomic layer deposition technique

    Science.gov (United States)

    Kosiel, Kamil; Koba, Marcin; Masiewicz, Marcin; Śmietana, Mateusz

    2018-06-01

    The paper shows application of atomic layer deposition (ALD) technique as a tool for tailoring sensorial properties of lossy-mode-resonance (LMR)-based optical fiber sensors. Hafnium dioxide (HfO2), zirconium dioxide (ZrO2), and tantalum oxide (TaxOy), as high-refractive-index dielectrics that are particularly convenient for LMR-sensor fabrication, were deposited by low-temperature (100 °C) ALD ensuring safe conditions for thermally vulnerable fibers. Applicability of HfO2 and ZrO2 overlays, deposited with ALD-related atomic level thickness accuracy for fabrication of LMR-sensors with controlled sensorial properties was presented. Additionally, for the first time according to our best knowledge, the double-layer overlay composed of two different materials - silicon nitride (SixNy) and TaxOy - is presented for the LMR fiber sensors. The thin films of such overlay were deposited by two different techniques - PECVD (the SixNy) and ALD (the TaxOy). Such approach ensures fast overlay fabrication and at the same time facility for resonant wavelength tuning, yielding devices with satisfactory sensorial properties.

  10. Simulation and growing study of Cu–Al–S thin films deposited by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Duclaux, L., E-mail: loraine-externe.duclaux@edf.fr [Institute of Research and Development on Photovoltaic Energy (IRDEP), EDF R& D/CNRS/ChimieParistech, UMR 7174, 6 quai Watier, 78401 Chatou (France); Donsanti, F.; Vidal, J. [Institute of Research and Development on Photovoltaic Energy (IRDEP), EDF R& D/CNRS/ChimieParistech, UMR 7174, 6 quai Watier, 78401 Chatou (France); Bouttemy, M. [Lavoisier Institute of Versailles, UMR 8180, 45 avenue des Etats-Unis, 78035 Versailles cedex (France); Schneider, N.; Naghavi, N. [Institute of Research and Development on Photovoltaic Energy (IRDEP), EDF R& D/CNRS/ChimieParistech, UMR 7174, 6 quai Watier, 78401 Chatou (France)

    2015-11-02

    In this paper, we have explored the potential of Cu–Al–S compounds as p-type transparent conducting material by means of atomistic simulation using CuAlS{sub 2} as a reference ternary compound and atomic layer deposition (ALD) growth. We have identified key intrinsic point defects acting either as shallow acceptor or deep donor which define the conductivity of CuAlS{sub 2}. Higher p-type conductivity was found to be achievable under metal-poor and chalcogen-rich growth conditions. According to this precept, ALD growth of Cu{sub x}Al{sub y}S{sub z} was attempted using Cu(acac){sub 2} and Al(CH{sub 3}){sub 3} as precursors for Cu and Al respectively and under H{sub 2}S atmosphere. While as grown thin films present low content of Al, it influences the band gap values as well as the obtained structures. - Highlights: • Ab-initio investigation of CuAlS{sub 2} • Indentification of two opposite main-contributive intrinsic defects on the conductivity: V{sub Cu} and Al{sub Cu} • Synthesis of Cu-Al-S ternary compound using atomic layer deposition • Impact of aluminum insertion on the optical and structural properties of the films.

  11. Kinetic study on hot-wire-assisted atomic layer deposition of nickel thin films

    International Nuclear Information System (INIS)

    Yuan, Guangjie; Shimizu, Hideharu; Momose, Takeshi; Shimogaki, Yukihiro

    2014-01-01

    High-purity Ni films were deposited using hot-wire-assisted atomic layer deposition (HW-ALD) at deposition temperatures of 175, 250, and 350 °C. Negligible amount of nitrogen or carbon contamination was detected, even though the authors used NH 2 radical as the reducing agent and nickelocene as the precursor. NH 2 radicals were generated by the thermal decomposition of NH 3 with the assist of HW and used to reduce the adsorbed metal growth precursors. To understand and improve the deposition process, the kinetics of HW-ALD were analyzed using a Langmuir-type model. Unlike remote-plasma-enhanced atomic layer deposition, HW-ALD does not lead to plasma-induced damage. This is a significant advantage, because the authors can supply sufficient NH 2 radicals to deposit high-purity metallic films by adjusting the distance between the hot wire and the substrate. NH 2 radicals have a short lifetime, and it was important to use a short distance between the radical generation site and substrate. Furthermore, the impurity content of the nickel films was independent of the deposition temperature, which is evidence of the temperature-independent nature of the NH 2 radical flux and the reactivity of the NH 2 radicals

  12. Chemical resistance of thin film materials based on metal oxides grown by atomic layer deposition

    International Nuclear Information System (INIS)

    Sammelselg, Väino; Netšipailo, Ivan; Aidla, Aleks; Tarre, Aivar; Aarik, Lauri; Asari, Jelena; Ritslaid, Peeter; Aarik, Jaan

    2013-01-01

    Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of < 5 pm/s. - Highlights: • Etching of atomic layer deposited thin metal oxide films in hot H 2 SO 4 was studied. • Smallest etching rates of < 5 pm/s for TiO 2 , Al 2 O 3 , and Cr 2 O 3 were reached. • Highest etching rate of 2.8 nm/s for Al 2 O 3 was occurred. • Remarkable differences in etching of non- and crystalline films were observed

  13. Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption.

    Science.gov (United States)

    Hägglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; Thomann, Isabell; Lee, Han-Bo-Ram; Brongersma, Mark L; Bent, Stacey F

    2013-07-10

    Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

  14. ATOMIC LAYER DEPOSITION OF TITANIUM OXIDE THIN FILMS ONNANOPOROUS ALUMINA TEMPLATES FOR MEDICAL APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Brigmon, R.

    2009-05-05

    Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of the nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Both the 20 nm and 100 nm titanium oxide-coated nanoporous alumina membranes did not exhibit statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. In addition, 20 nm pore size titanium oxide-coated nanoporous alumina membranes exposed to ultraviolet light demonstrated activity against Escherichia coli and Staphylococcus aureus bacteria. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for 'smart' drug delivery devices, orthopedic implants, or self-sterilizing medical devices.

  15. Selective deposition contact patterning using atomic layer deposition for the fabrication of crystalline silicon solar cells

    International Nuclear Information System (INIS)

    Cho, Young Joon; Shin, Woong-Chul; Chang, Hyo Sik

    2014-01-01

    Selective deposition contact (SDC) patterning was applied to fabricate the rear side passivation of crystalline silicon (Si) solar cells. By this method, using screen printing for contact patterning and atomic layer deposition for the passivation of Si solar cells with Al 2 O 3 , we produced local contacts without photolithography or any laser-based processes. Passivated emitter and rear-contact solar cells passivated with ozone-based Al 2 O 3 showed, for the SDC process, an up-to-0.7% absolute conversion-efficiency improvement. The results of this experiment indicate that the proposed method is feasible for conversion-efficiency improvement of industrial crystalline Si solar cells. - Highlights: • We propose a local contact formation process. • Local contact forms a screen print and an atomic layer deposited-Al 2 O 3 film. • Ozone-based Al 2 O 3 thin film was selectively deposited onto patterned silicon. • Selective deposition contact patterning method can increase cell-efficiency by 0.7%

  16. Modular injector integrated linear apparatus with motion profile optimization for spatial atomic layer deposition

    Science.gov (United States)

    Wang, Xiaolei; Li, Yun; Lin, Jilong; Shan, Bin; Chen, Rong

    2017-11-01

    A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

  17. Atomic-Layer-Deposited AZO Outperforms ITO in High-Efficiency Polymer Solar Cells

    KAUST Repository

    Kan, Zhipeng; Wang, Zhenwei; Firdaus, Yuliar; Babics, Maxime; Alshareef, Husam N.; Beaujuge, Pierre

    2018-01-01

    Tin-doped indium oxide (ITO) transparent conducting electrodes are widely used across the display industry, and are currently the cornerstone of photovoltaic device developments, taking a substantial share in the manufacturing cost of large-area modules. However, cost and supply considerations are set to limit the extensive use of indium for optoelectronic device applications and, in turn, alternative transparent conducting oxide (TCO) materials are required. In this report, we show that aluminum-doped zinc oxide (AZO) thin films grown by atomic layer deposition (ALD) are sufficiently conductive and transparent to outperform ITO as the cathode in inverted polymer solar cells. Reference polymer solar cells made with atomic-layer-deposited AZO cathodes, PCE10 as the polymer donor and PC71BM as the fullerene acceptor (model systems), reach power conversion efficiencies of ca. 10% (compared to ca. 9% with ITO-coated glass), without compromising other figures of merit. These ALD-grown AZO electrodes are promising for a wide range of optoelectronic device applications relying on TCOs.

  18. Low-temperature atomic layer deposition of TiO2 thin layers for the processing of memristive devices

    International Nuclear Information System (INIS)

    Porro, Samuele; Conti, Daniele; Guastella, Salvatore; Ricciardi, Carlo; Jasmin, Alladin; Pirri, Candido F.; Bejtka, Katarzyna; Perrone, Denis; Chiolerio, Alessandro

    2016-01-01

    Atomic layer deposition (ALD) represents one of the most fundamental techniques capable of satisfying the strict technological requirements imposed by the rapidly evolving electronic components industry. The actual scaling trend is rapidly leading to the fabrication of nanoscaled devices able to overcome limits of the present microelectronic technology, of which the memristor is one of the principal candidates. Since their development in 2008, TiO 2 thin film memristors have been identified as the future technology for resistive random access memories because of their numerous advantages in producing dense, low power-consuming, three-dimensional memory stacks. The typical features of ALD, such as self-limiting and conformal deposition without line-of-sight requirements, are strong assets for fabricating these nanosized devices. This work focuses on the realization of memristors based on low-temperature ALD TiO 2 thin films. In this process, the oxide layer was directly grown on a polymeric photoresist, thus simplifying the fabrication procedure with a direct liftoff patterning instead of a complex dry etching process. The TiO 2 thin films deposited in a temperature range of 120–230 °C were characterized via Raman spectroscopy and x-ray photoelectron spectroscopy, and electrical current–voltage measurements taken in voltage sweep mode were employed to confirm the existence of resistive switching behaviors typical of memristors. These measurements showed that these low-temperature devices exhibit an ON/OFF ratio comparable to that of a high-temperature memristor, thus exhibiting similar performances with respect to memory applications

  19. Oxygen vacancy defect engineering using atomic layer deposited HfAlOx in multi-layered gate stack

    Science.gov (United States)

    Bhuyian, M. N.; Sengupta, R.; Vurikiti, P.; Misra, D.

    2016-05-01

    This work evaluates the defects in high quality atomic layer deposited (ALD) HfAlOx with extremely low Al (estimated by the high temperature current voltage measurement shows that the charged oxygen vacancies, V+/V2+, are the primary source of defects in these dielectrics. When Al is added in HfO2, the V+ type defects with a defect activation energy of Ea ˜ 0.2 eV modify to V2+ type to Ea ˜ 0.1 eV with reference to the Si conduction band. When devices were stressed in the gate injection mode for 1000 s, more V+ type defects are generated and Ea reverts back to ˜0.2 eV. Since Al has a less number of valence electrons than do Hf, the change in the co-ordination number due to Al incorporation seems to contribute to the defect level modifications. Additionally, the stress induced leakage current behavior observed at 20 °C and at 125 °C demonstrates that the addition of Al in HfO2 contributed to suppressed trap generation process. This further supports the defect engineering model as reduced flat-band voltage shifts were observed at 20 °C and at 125 °C.

  20. Atomic layer deposition assisted pattern transfer technology for ultra-thin block copolymer films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wenhui; Luo, Jun; Meng, Lingkuan; Li, Junjie; Xiang, Jinjuan; Li, Junfeng; Wang, Wenwu; Chen, Dapeng; Ye, Tianchun; Zhao, Chao

    2016-08-31

    As an emerging developing technique for next-generation lithography, directed self-assembly (DSA) of block copolymer (BCP) has attracted numerous attention and has been a potential alternative to supplement the intrinsic limitations of conventional photolithography. In this work, the self-assembling properties of a lamellar diblock copolymer poly(styrene-b-methylmethacrylate) (PS-b-PMMA, 22k-b-22k, L{sub 0} = 25 nm) on Si substrate and an atomic layer deposition (ALD)-assisted pattern transfer technology for the application of DSA beyond 16/14 nm complementary metal oxide semiconductor (CMOS) technology nodes, were investigated. Firstly, two key processing parameters of DSA, i.e. annealing temperatures and durations of BCP films, were optimized to achieve low defect density and high productivity. After phase separation of BCP films, self-assembling patterns of low defect density should be transferred to the substrate. However, due to the nano-scale thickness and the weak resistance of BCP films to dry etching, it is nearly impossible to transfer the BCP patterns directly to the substrate. Therefore, an ALD-based technology was explored in this work, in which deposited Al{sub 2}O{sub 3} selectively reacts with PMMA blocks thus hardening the PMMA patterns. After removing PS blocks by plasma etching, hardened PMMA patterns were left and transferred to underneath SiO{sub 2} hard mask layer. Using this patterned hard mask, nanowire array of 25 nm pitch were realized on Si substrate. From this work, a high-throughput DSA baseline flow and related ALD-assisted pattern transfer technique were developed and proved to have good capability with the mainstream CMOS technology. - Highlights: • Optimization on self-assembly process for high productivity and low defectivity • Enhancement of etching ratio and resistance by atomic layer deposition (ALD) • A hard mask was used for pattern quality improvement and contamination control.

  1. Atomic layer deposition of zirconium dioxide from zirconium tetrachloride and ozone

    Energy Technology Data Exchange (ETDEWEB)

    Kukli, Kaupo, E-mail: kaupo.kukli@helsinki.fi [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland); Kemell, Marianna; Köykkä, Joel [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [Accelerator Laboratory, Department of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki (Finland); Vehkamäki, Marko; Ritala, Mikko; Leskelä, Markku [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland)

    2015-08-31

    ZrO{sub 2} films were grown by atomic layer deposition using ZrCl{sub 4} and O{sub 3} as precursors. The films were grown on silicon substrates in the temperature range of 220–500 °C. The ALD rate was monotonously decreasing from 0.085 to 0.060 nm/cycle in this temperature range towards the highest temperatures studied. The content of chlorine in the films did not exceed 0.2 at.% as measured by elastic recoil detection analysis. The content of hydrogen was 0.30 and 0.14 at.% in the films grown at 300 and 400 °C, respectively. Structural studies revealed the films consisting of mixtures of stable monoclinic and metastable tetragonal/cubic polymorphs of ZrO{sub 2}, and dominantly metastable phases of ZrO{sub 2} below and above 300 °C, respectively. Permittivity of dielectric layers in Al/Ti/ZrO{sub 2}/(TiN/)Si capacitors with 15–40 nm thick ZrO{sub 2} ranged between 12 and 25 at 100 kHz and the dielectric breakdown fields were in the range of 1.5–3.0 MV/cm. - Highlights: • ZrO{sub 2} thin films were grown by atomic layer deposition from ZrCl{sub 4} and O{sub 3}. • Relatively high substrate temperatures promoted growth of metastable ZrO{sub 2} phases. • ZrO{sub 2} films exhibited electric properties characteristic of dielectric metal oxides. • ZrO{sub 2} grown in hydrogen- and carbon free process contained low amounts of impurities.

  2. Atoms

    International Nuclear Information System (INIS)

    Fuchs, Alain; Villani, Cedric; Guthleben, Denis; Leduc, Michele; Brenner, Anastasios; Pouthas, Joel; Perrin, Jean

    2014-01-01

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  3. From Single Atoms to Nanoparticles : Autocatalysis and Metal Aggregation in Atomic Layer Deposition of Pt on TiO2 Nanopowder

    NARCIS (Netherlands)

    Grillo, Fabio; Van Bui, Hao; La Zara, Damiano; Aarnink, Antonius A.I.; Kovalgin, Alexey Y.; Kooyman, Patricia; Kreutzer, Michiel T.; van Ommen, Jan Rudolf

    2018-01-01

    A fundamental understanding of the interplay between ligand-removal kinetics and metal aggregation during the formation of platinum nanoparticles (NPs) in atomic layer deposition of Pt on TiO2 nanopowder using trimethyl(methylcyclo-pentadienyl)platinum(IV) as the precursor and O2 as the coreactant

  4. In-situ atomic layer deposition growth of Hf-oxide

    International Nuclear Information System (INIS)

    Karavaev, Konstantin

    2010-01-01

    We have grown HfO 2 on Si(001) by atomic layer deposition (ALD) using HfCl 4 , TEMAHf, TDMAHf and H 2 O as precursors. The early stages of the ALD were investigated with high-resolution photoelectron spectroscopy and X-ray absorption spectroscopy. We observed the changes occurring in the Si 2p, O 1s, Hf 4f, Hf 4d, and Cl 2p (for HfCl 4 experiment) core level lines after each ALD cycle up to the complete formation of two layers of HfO 2 . The investigation was carried out in situ giving the possibility to determine the properties of the grown film after every ALD cycle or even after a half cycle. This work focused on the advantages in-situ approach in comparison with ex-situ experiments. The study provides to follow the evolution of the important properties of HfO 2 : contamination level, density and stoichiometry, and influence of the experimental parameters to the interface layer formation during ALD. Our investigation shows that in-situ XPS approach for ALD gives much more information than ex-situ experiments. (orig.)

  5. In-situ atomic layer deposition growth of Hf-oxide

    Energy Technology Data Exchange (ETDEWEB)

    Karavaev, Konstantin

    2010-06-17

    We have grown HfO{sub 2} on Si(001) by atomic layer deposition (ALD) using HfCl{sub 4}, TEMAHf, TDMAHf and H{sub 2}O as precursors. The early stages of the ALD were investigated with high-resolution photoelectron spectroscopy and X-ray absorption spectroscopy. We observed the changes occurring in the Si 2p, O 1s, Hf 4f, Hf 4d, and Cl 2p (for HfCl{sub 4} experiment) core level lines after each ALD cycle up to the complete formation of two layers of HfO{sub 2}. The investigation was carried out in situ giving the possibility to determine the properties of the grown film after every ALD cycle or even after a half cycle. This work focused on the advantages in-situ approach in comparison with ex-situ experiments. The study provides to follow the evolution of the important properties of HfO{sub 2}: contamination level, density and stoichiometry, and influence of the experimental parameters to the interface layer formation during ALD. Our investigation shows that in-situ XPS approach for ALD gives much more information than ex-situ experiments. (orig.)

  6. Atomic Layer Deposition of Nickel on ZnO Nanowire Arrays for High-Performance Supercapacitors.

    Science.gov (United States)

    Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Wang, Yong-Ping; Liu, Wen-Jun; Ji, Xin-Ming; Devi, Anjana; Jiang, An-Quan; Zhang, David Wei

    2018-01-10

    A novel hybrid core-shell structure of ZnO nanowires (NWs)/Ni as a pseudocapacitor electrode was successfully fabricated by atomic layer deposition of a nickel shell, and its capacitive performance was systemically investigated. Transmission electron microscopy and X-ray photoelectron spectroscopy results indicated that the NiO was formed at the interface between ZnO and Ni where the Ni was oxidized by ZnO during the ALD of the Ni layer. Electrochemical measurement results revealed that the Ti/ZnO NWs/Ni (1500 cycles) electrode with a 30 nm thick Ni-NiO shell layer had the best supercapacitor properties including ultrahigh specific capacitance (∼2440 F g -1 ), good rate capability (80.5%) under high current charge-discharge conditions, and a relatively better cycling stability (86.7% of the initial value remained after 750 cycles at 10 A g -1 ). These attractive capacitive behaviors are mainly attributed to the unique core-shell structure and the combined effect of ZnO NW arrays as short charge transfer pathways for ion diffusion and electron transfer as well as conductive Ni serving as channel for the fast electron transport to Ti substrate. This high-performance Ti/ZnO NWs/Ni hybrid structure is expected to be one of a promising electrodes for high-performance supercapacitor applications.

  7. Area-selective atomic layer deposition of platinum using photosensitive polyimide.

    Science.gov (United States)

    Vervuurt, René H J; Sharma, Akhil; Jiao, Yuqing; Kessels, Wilhelmus Erwin M M; Bol, Ageeth A

    2016-10-07

    Area-selective atomic layer deposition (AS-ALD) of platinum (Pt) was studied using photosensitive polyimide as a masking layer. The polyimide films were prepared by spin-coating and patterned using photolithography. AS-ALD of Pt using poly(methyl-methacrylate) (PMMA) masking layers was used as a reference. The results show that polyimide has excellent selectivity towards the Pt deposition, after 1000 ALD cycles less than a monolayer of Pt is deposited on the polyimide surface. The polyimide film could easily be removed after ALD using a hydrogen plasma, due to a combination of weakening of the polyimide resist during Pt ALD and the catalytic activity of Pt traces on the polyimide surface. Compared to PMMA for AS-ALD of Pt, polyimide has better temperature stability. This resulted in an improved uniformity of the Pt deposits and superior definition of the Pt patterns. In addition, due to the absence of reflow contamination using polyimide the nucleation phase during Pt ALD is drastically shortened. Pt patterns down to 3.5 μm were created with polyimide, a factor of ten smaller than what is possible using PMMA, at the typical Pt ALD processing temperature of 300 °C. Initial experiments indicate that after further optimization of the polyimide process Pt features down to 100 nm should be possible, which makes AS-ALD of Pt using photosensitive polyimide a promising candidate for patterning at the nanoscale.

  8. Coloration of metallic and/or ceramic surfaces obtained by atomic layer deposited nano-coatings

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, L., E-mail: luisg47@gmail.com [Fondazione Bruno Kessler (FBK), Centro Materiali e Microsistemi, Functional Materials & Photonic Structures Unit, via Sommarive 18, 38123 Trento (Italy); Vettoruzzo, F. [Ronda High Tech, via Vegri 83, 36010 Zane’, Vicenza (Italy); Laidani, N. [Fondazione Bruno Kessler (FBK), Centro Materiali e Microsistemi, Functional Materials & Photonic Structures Unit, via Sommarive 18, 38123 Trento (Italy)

    2016-02-29

    By depositing single layer coatings by means of physical vapor techniques, tailoring of their coloration is generally complex because a given color can be obtained only by very high composition control. Physical vapor deposition (PVD) processes are expensive and cannot be easily used for obtaining conformal coating on three-dimensional objects. Moreover PVD coatings exhibit intrinsic defects (columnar structures, pores) that affect their functional properties and applications such as barrier layers. Atomic layer deposition (ALD) technology delivers conformal coatings on different materials with very low defectiveness. A straightforward coloration can be obtained by a combination of two types of layers with different refraction index, deposited to high thickness precision. Computer simulation studies were performed to design the thickness and architecture of multilayer structures, to a total thickness of approximately 100 nm, suitable to modify the typical coloration of some materials, without altering their other physical and chemical properties. The most promising nano-layered structures were then deposited by ALD and tested with regard to their optical properties. Their total thicknesses were specified in such a way to be technically feasible and compatible with future industrial production. The materials employed in this study to build the optical coatings, are two oxides (Al{sub 2}O{sub 3}, TiO{sub 2}) deposited at 120 °C and two nitrides (AlN, TiN), which need a deposition temperature of 400 °C. The possibility of using such modern deposition technology for esthetic and decorative purposes, while maintaining the functional properties, opens perspectives of industrial applications. - Highlights: • Computer simulation is done to design multilayers made of Al{sub 2}O{sub 3}, TiO{sub 2}, AlN, and TiN. • Total thickness (< 120 nm) is specified to be compatible with industrial production. • The most promising nano-layered structures are then produced and

  9. Atomic layer deposition of calcium oxide and calcium hafnium oxide films using calcium cyclopentadienyl precursor

    International Nuclear Information System (INIS)

    Kukli, Kaupo; Ritala, Mikko; Sajavaara, Timo; Haenninen, Timo; Leskelae, Markku

    2006-01-01

    Calcium oxide and calcium hafnium oxide thin films were grown by atomic layer deposition on borosilicate glass and silicon substrates in the temperature range of 205-300 o C. The calcium oxide films were grown from novel calcium cyclopentadienyl precursor and water. Calcium oxide films possessed refractive index 1.75-1.80. Calcium oxide films grown without Al 2 O 3 capping layer occurred hygroscopic and converted to Ca(OH) 2 after exposure to air. As-deposited CaO films were (200)-oriented. CaO covered with Al 2 O 3 capping layers contained relatively low amounts of hydrogen and re-oriented into (111) direction upon annealing at 900 o C. In order to examine the application of CaO in high-permittivity dielectric layers, mixtures of Ca and Hf oxides were grown by alternate CaO and HfO 2 growth cycles at 230 and 300 o C. HfCl 4 was used as a hafnium precursor. When grown at 230 o C, the films were amorphous with equal amounts of Ca and Hf constituents (15 at.%). These films crystallized upon annealing at 750 o C, showing X-ray diffraction peaks characteristic of hafnium-rich phases such as Ca 2 Hf 7 O 16 or Ca 6 Hf 19 O 44 . At 300 o C, the relative Ca content remained below 8 at.%. The crystallized phase well matched with rhombohedral Ca 2 Hf 7 O 16 . The dielectric films grown on Si(100) substrates possessed effective permittivity values in the range of 12.8-14.2

  10. Al2 O3 Underlayer Prepared by Atomic Layer Deposition for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Zhang, Jinbao; Hultqvist, Adam; Zhang, Tian; Jiang, Liangcong; Ruan, Changqing; Yang, Li; Cheng, Yibing; Edoff, Marika; Johansson, Erik M J

    2017-10-09

    Perovskite solar cells, as an emergent technology for solar energy conversion, have attracted much attention in the solar cell community by demonstrating impressive enhancement in power conversion efficiencies. However, the high temperature and manually processed TiO 2 underlayer prepared by spray pyrolysis significantly limit the large-scale application and device reproducibility of perovskite solar cells. In this study, lowtemperature atomic layer deposition (ALD) is used to prepare a compact Al 2 O 3 underlayer for perovskite solar cells. The thickness of the Al 2 O 3 layer can be controlled well by adjusting the deposition cycles during the ALD process. An optimal Al 2 O 3 layer effectively blocks electron recombination at the perovskite/fluorine-doped tin oxide interface and sufficiently transports electrons through tunneling. Perovskite solar cells fabricated with an Al 2 O 3 layer demonstrated a highest efficiency of 16.2 % for the sample with 50 ALD cycles (ca. 5 nm), which is a significant improvement over underlayer-free PSCs, which have a maximum efficiency of 11.0 %. Detailed characterization confirms that the thickness of the Al 2 O 3 underlayer significantly influences the charge transfer resistance and electron recombination processes in the devices. Furthermore, this work shows the feasibility of using a high band-gap semiconductor such as Al 2 O 3 as the underlayer in perovskite solar cells and opens up pathways to use ALD Al 2 O 3 underlayers for flexible solar cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Tribological Properties of Nanometric Atomic Layer Depositions Applied on AISI 420 Stainless Steel

    Directory of Open Access Journals (Sweden)

    E. Marin

    2013-09-01

    Full Text Available Atomic Layer Deposition ( ALD is a modern technique that Allows to deposit nanometric, conformal coatings on almost any kind of substrates, from plastics to ceramic, metals or even composites. ALD coatings are not dependent on the morphology of the substrate and are only regulated by the composition of the precursors, the chamber temperature and the number of cycles. In this work, mono- and bi -layer nanometric, protective low-temperature ALD Coatings, based on Al2O3 and TiO2 were applied on AISI 420 Stainless Steel in orderto enhance its relatively low corrosion resistance in chloride containing environments. Tribological testing were also performed on the ALD coated AISI 420 in order to evaluate the wear and scratch resistance of these nanometric layers and thus evaluate their durability. Scratch tests were performed using a standard Rockwell C indenter, under a variable load condition, in order to evaluate the critical loading condition for each coating. Wear testing were performed using a stainless steel counterpart, in ball-on-discconfiguration, in order to measure the friction coefficient and wear to confront the resistance. All scratch tests scars and wear tracks were then observed by means of Scanning Electron Microscopy (SEM in order to understand the wear mechanisms that occurred on the sample surfaces. Corrosion testing, performed under immersion in 0.2 M NaCl solutions, clearly showed that the ALD coatings have a strong effect in protecting the Stainless Steel Substrate against corrosion, reducing the corrosion current density by two orders of magnitude.Tribological The preliminary results showed that ALD depositions obtained at low Temperatures have a brittle behavior caused by the amorphous nature of their structure, and thus undergo delamination phenomena during Scratch Testing at relatively low applied loads. During ball-on-disc testing, the coatings were removed from the substrate, in particular for monolayer ALD configurations

  12. Alkali-resistant low-temperature atomic-layer-deposited oxides for optical fiber sensor overlays

    Science.gov (United States)

    Kosiel, K.; Dominik, M.; Ściślewska, I.; Kalisz, M.; Guziewicz, M.; Gołaszewska, K.; Niedziółka-Jonsson, J.; Bock, W. J.; Śmietana, M.

    2018-04-01

    This paper presents an investigation of properties of selected metallic oxides deposited at a low temperature (100 °C) by atomic layer deposition (ALD) technique, relating to their applicability as thin overlays for optical fiber sensors resistant in alkaline environments. Hafnium oxide (Hf x O y with y/x approx. 2.70), tantalum oxide (Ta x O y with y/x approx. 2.75) and zirconium oxide (Zr x O y with y/x approx. 2.07), which deposition was based, respectively, on tetrakis(ethylmethyl)hafnium, tantalum pentachloride and tetrakis(ethylmethyl)zirconium with deionized water, were tested as thin layers on planar Si (100) and glass substrates. Growth per cycle (GPC) in the ALD processes was 0.133-0.150 nm/cycle. Run-to-run GPC reproducibility of the ALD processes was best for Hf x O y (0.145 ± 0.001 nm/cycle) and the poorest for Ta x O y (0.133 ± 0.003 nm/cycle). Refractive indices n of the layers were 2.00-2.10 (at the wavelength λ = 632 nm), with negligible k value (at λ for 240-930 nm). The oxides examined by x-ray diffractometry proved to be amorphous, with only small addition of crystalline phases for the Zr x O y . The surfaces of the oxides had grainy but smooth topographies with root-mean square roughness ˜0.5 nm (at 10 × 10 μm2 area) according to atomic force microscopy. Ellipsometric measurements, by contrast, suggest rougher surfaces for the Zr x O y layers. The surfaces were also slightly rougher on the glass-based samples than on the Si-based ones. Nanohardness and Young modules were 4.90-8.64 GPa and 83.7-104.4 GPa, respectively. The tests of scratch resistance revealed better tribological properties for the Hf x O y and the Ta x O y than for the Zr x O y . The surfaces were hydrophilic, with wetting angles of 52.5°-62.9°. The planar oxides on Si, being resistive even to concentrated alkali (pH 14), proved to be significantly more alkali-resistive than Al2O3. The Ta x O y overlay was deposited on long-period grating sensor induced in optical

  13. Quantum size effects in TiO2 thin films grown by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Massimo Tallarida

    2014-01-01

    Full Text Available We study the atomic layer deposition of TiO2 by means of X-ray absorption spectroscopy. The Ti precursor, titanium isopropoxide, was used in combination with H2O on Si/SiO2 substrates that were heated at 200 °C. The low growth rate (0.15 Å/cycle and the in situ characterization permitted to follow changes in the electronic structure of TiO2 in the sub-nanometer range, which are influenced by quantum size effects. The modified electronic properties may play an important role in charge carrier transport and separation, and increase the efficiency of energy conversion systems.

  14. Using atomic layer deposited tungsten to increase thermal conductivity of a packed bed

    Energy Technology Data Exchange (ETDEWEB)

    Van Norman, Staci A.; Falconer, John L.; Weimer, Alan W., E-mail: alan.weimer@colorado.edu [Department of Chemical and Biological Engineering, University of Colorado, UCB 596, Boulder, Colorado 80309-0596 (United States); Tringe, Joseph W.; Sain, John D. [Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550 (United States); Yang, Ronggui [Department of Mechanical Engineering, University of Colorado, UCB 427, Boulder, Colorado 80309-0427 (United States)

    2015-04-13

    This study investigated the effective thermal conductivity (k{sub eff}) of packed-beds that contained porous particles with nanoscale tungsten (W) films of different thicknesses formed by atomic layer deposition (ALD). A continuous film on the particles is vital towards increasing k{sub eff} of the packed beds. For example, the k{sub eff} of an alumina packed bed was increased by three times after an ∼8-nm continuous W film with 20 cycles of W ALD, whereas k{sub eff} was decreased on a polymer packed bed with discontinuous, evenly dispersed W-islands due to nanoparticle scattering of phonons. For catalysts, understanding the thermal properties of these packed beds is essential for developing thermally conductive supports as alternatives to structured supports.

  15. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28

    A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.

  16. Monolithic Laser Scribed Graphene Scaffold with Atomic Layer Deposited Platinum for Hydrogen Evolution Reaction

    KAUST Repository

    Nayak, Pranati; Jiang, Qiu; Kurra, Narendra; Buttner, Ulrich; Wang, Xianbin; Alshareef, Husam N.

    2017-01-01

    The use of three-dimensional (3D) electrode architectures as scaffolds for conformal deposition of catalysts is an emerging research area with significant potential for electrocatalytic applications. In this study, we report the fabrication of monolithic, self-standing, 3D graphitic carbon scaffold with conformally deposited Pt by atomic layer deposition (ALD) as a hydrogen evolution reaction catalyst. Laser scribing is employed to transform polyimide into 3D porous graphitic carbon, which possesses good electronic conductivity and numerous edge plane sites. This laser scribed graphene (LSG) architecture makes it possible to fabricate monolithic electrocatalyst support without any binders or conductive additives. The synergistic effect between ALD of Pt on 3D network of LSG provides an avenue for minimal yet effective Pt usage, leading to an enhanced HER activity. This strategy establish a general approach for inexpensive and large scale HER device fabrication with minimum catalyst cost.

  17. Thin films of In2O3 by atomic layer deposition using In(acac)3

    International Nuclear Information System (INIS)

    Nilsen, O.; Balasundaraprabhu, R.; Monakhov, E.V.; Muthukumarasamy, N.; Fjellvag, H.; Svensson, B.G.

    2009-01-01

    Thin films of indium oxide have been deposited using the atomic layer deposition (ALD) technique using In(acac) 3 (acac = acetylacetonate, pentane-2,4-dione) and either H 2 O or O 3 as precursors. Successful growth using In(acac) 3 is contradictory to what has been reported previously in the literature [J.W. Elam, A.B.F. Martinson, M.J. Pellin, J.T. Hupp, Chem. Mater. 18 (2006) 3571.]. Investigation of the dependence of temperature on the deposition shows windows where the growth rates are relatively unaffected by temperature in the ranges 165-200 o C for In(acac) 3 and H 2 O, 165-225 o C for In(acac) 3 and O 3 . The growth rates obtained are of the order 20 pm/cycle for In(acac) 3 and H 2 O, 12 pm/cycle for In(acac) 3 .

  18. Thermal stability of atomic layer deposition Al2O3 film on HgCdTe

    Science.gov (United States)

    Zhang, P.; Sun, C. H.; Zhang, Y.; Chen, X.; He, K.; Chen, Y. Y.; Ye, Z. H.

    2015-06-01

    Thermal stability of Atomic Layer Deposition Al2O3 film on HgCdTe was investigated by Al2O3 film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al2O3 film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

  19. Femtosecond laser patterning, synthesis, defect formation, and structural modification of atomic layered materials

    International Nuclear Information System (INIS)

    Yoo, Jae-Hyuck; Kim, Eunpa; Hwang, David J.

    2016-01-01

    This article summarizes recent research on laser-based processing of twodimensional (2D) atomic layered materials, including graphene and transition metal dichalcogenides (TMDCs). Ultrafast lasers offer unique processing routes that take advantage of distinct interaction mechanisms with 2D materials to enable extremely localized energy deposition. Experiments have shown that ablative direct patterning of graphene by ultrafast lasers can achieve resolutions of tens of nanometers, as well as single-step pattern transfer. Ultrafast lasers also induce non-thermal excitation mechanisms that are useful for the thinning of TMDCs to tune the 2D material bandgap. Laser-assisted site-specific doping was recently demonstrated where ultrafast laser radiation under ambient air environment could be used for the direct writing of high-quality graphene patterns on insulating substrates. This article concludes with an outlook towards developing further advanced laser processing with scalability, in situ monitoring strategies and potential applications.

  20. Enhancing the platinum atomic layer deposition infiltration depth inside anodic alumina nanoporous membrane

    Energy Technology Data Exchange (ETDEWEB)

    Vaish, Amit, E-mail: anv@udel.edu; Krueger, Susan; Dimitriou, Michael; Majkrzak, Charles [National Institute of Standards and Technology (NIST) Center for Neutron Research, Gaithersburg, MD 20899-8313 (United States); Vanderah, David J. [Institute for Bioscience and Biotechnology Research, NIST, Rockville, Maryland 20850 (United States); Chen, Lei, E-mail: lei.chen@nist.gov [NIST Center for Nanoscale Science and Technology, Gaithersburg, Maryland 20899-8313 (United States); Gawrisch, Klaus [Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892 (United States)

    2015-01-15

    Nanoporous platinum membranes can be straightforwardly fabricated by forming a Pt coating inside the nanopores of anodic alumina membranes (AAO) using atomic layer deposition (ALD). However, the high-aspect-ratio of AAO makes Pt ALD very challenging. By tuning the process deposition temperature and precursor exposure time, enhanced infiltration depth along with conformal coating was achieved for Pt ALD inside the AAO templates. Cross-sectional scanning electron microscopy/energy dispersive x-ray spectroscopy and small angle neutron scattering were employed to analyze the Pt coverage and thickness inside the AAO nanopores. Additionally, one application of platinum-coated membrane was demonstrated by creating a high-density protein-functionalized interface.

  1. Low-temperature atomic layer deposition of MoS{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Jurca, Titel; Wang, Binghao; Tan, Jeffrey M.; Lohr, Tracy L.; Marks, Tobin J. [Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL (United States); Moody, Michael J.; Henning, Alex; Emery, Jonathan D.; Lauhon, Lincoln J. [Department of Materials Science and Engineering, and the Materials Research Center, Northwestern University, Evanston, IL (United States)

    2017-04-24

    Wet chemical screening reveals the very high reactivity of Mo(NMe{sub 2}){sub 4} with H{sub 2}S for the low-temperature synthesis of MoS{sub 2}. This observation motivated an investigation of Mo(NMe{sub 2}){sub 4} as a volatile precursor for the atomic layer deposition (ALD) of MoS{sub 2} thin films. Herein we report that Mo(NMe{sub 2}){sub 4} enables MoS{sub 2} film growth at record low temperatures - as low as 60 C. The as-deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift-off patterning for the straightforward fabrication of diverse device structures. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Stacking and electric field effects in atomically thin layers of GaN

    International Nuclear Information System (INIS)

    Xu, Dongwei; He, Haiying; Pandey, Ravindra; Karna, Shashi P

    2013-01-01

    Atomically thin layers of nitrides are a subject of interest due to their novel applications. In this paper, we focus on GaN multilayers, investigating their stability and the effects of stacking and electric fields on their electronic properties in the framework of density functional theory. Both bilayers and trilayers prefer a planar configuration rather than a buckled bulk-like configuration. The application of an external perpendicular electric field induces distinct stacking-dependent features in the electronic properties of nitride multilayers: the band gap of a monolayer does not change whereas that of a trilayer is significantly reduced. Such a stacking-dependent tunability of the band gap in the presence of an applied field suggests that multilayer GaN is a good candidate material for next generation devices at the nanoscale. (paper)

  3. Designing high performance precursors for atomic layer deposition of silicon oxide

    Energy Technology Data Exchange (ETDEWEB)

    Mallikarjunan, Anupama, E-mail: mallika@airproducts.com; Chandra, Haripin; Xiao, Manchao; Lei, Xinjian; Pearlstein, Ronald M.; Bowen, Heather R.; O' Neill, Mark L. [Air Products and Chemicals, Inc., 1969 Palomar Oaks Way, Carlsbad, California 92011 (United States); Derecskei-Kovacs, Agnes [Air Products and Chemicals, Inc., 7201 Hamilton Blvd., Allentown, Pennsylvania 18195 (United States); Han, Bing [Air Products and Chemicals, Inc., 2 Dongsanhuan North Road, Chaoyang District, Beijing 100027 (China)

    2015-01-15

    Conformal and continuous silicon oxide films produced by atomic layer deposition (ALD) are enabling novel processing schemes and integrated device structures. The increasing drive toward lower temperature processing requires new precursors with even higher reactivity. The aminosilane family of precursors has advantages due to their reactive nature and relative ease of use. In this paper, the authors present the experimental results that reveal the uniqueness of the monoaminosilane structure [(R{sub 2}N)SiH{sub 3}] in providing ultralow temperature silicon oxide depositions. Disubstituted aminosilanes with primary amines such as in bis(t-butylamino)silane and with secondary amines such as in bis(diethylamino)silane were compared with a representative monoaminosilane: di-sec-butylaminosilane (DSBAS). DSBAS showed the highest growth per cycle in both thermal and plasma enhanced ALD. These findings show the importance of the arrangement of the precursor's organic groups in an ALD silicon oxide process.

  4. Monolithic Laser Scribed Graphene Scaffold with Atomic Layer Deposited Platinum for Hydrogen Evolution Reaction

    KAUST Repository

    Nayak, Pranati

    2017-09-01

    The use of three-dimensional (3D) electrode architectures as scaffolds for conformal deposition of catalysts is an emerging research area with significant potential for electrocatalytic applications. In this study, we report the fabrication of monolithic, self-standing, 3D graphitic carbon scaffold with conformally deposited Pt by atomic layer deposition (ALD) as a hydrogen evolution reaction catalyst. Laser scribing is employed to transform polyimide into 3D porous graphitic carbon, which possesses good electronic conductivity and numerous edge plane sites. This laser scribed graphene (LSG) architecture makes it possible to fabricate monolithic electrocatalyst support without any binders or conductive additives. The synergistic effect between ALD of Pt on 3D network of LSG provides an avenue for minimal yet effective Pt usage, leading to an enhanced HER activity. This strategy establish a general approach for inexpensive and large scale HER device fabrication with minimum catalyst cost.

  5. Control of thermal deformation in dielectric mirrors using mechanical design and atomic layer deposition.

    Science.gov (United States)

    Gabriel, Nicholas T; Kim, Sangho S; Talghader, Joseph J

    2009-07-01

    A mechanical design technique for optical coatings that simultaneously controls thermal deformation and optical reflectivity is reported. The method requires measurement of the refractive index and thermal stress of single films prior to the design. Atomic layer deposition was used for deposition because of the high repeatability of the film constants. An Al2O3/HfO2 distributed Bragg reflector was deposited with a predicted peak reflectivity of 87.9% at 542.4 nm and predicted edge deformation of -360 nm/K on a 10 cm silicon substrate. The measured peak reflectivity was 85.7% at 541.7 nm with an edge deformation of -346 nm/K.

  6. An atomic-force-microscopy study of the structure of surface layers of intact fibroblasts

    Science.gov (United States)

    Khalisov, M. M.; Ankudinov, A. V.; Penniyaynen, V. A.; Nyapshaev, I. A.; Kipenko, A. V.; Timoshchuk, K. I.; Podzorova, S. A.; Krylov, B. V.

    2017-02-01

    Intact embryonic fibroblasts on a collagen-treated substrate have been studied by atomic-force microscopy (AFM) using probes of two types: (i) standard probes with tip curvature radii of 2-10 nm and (ii) special probes with a calibrated 325-nm SiO2 ball radius at the tip apex. It is established that, irrespective of probe type, the average maximum fibroblast height is on a level of 1.7 μm and the average stiffness of the probe-cell contact amounts to 16.5 mN/m. The obtained AFM data reveal a peculiarity of the fibroblast structure, whereby its external layers move as a rigid shell relative to the interior and can be pressed inside to a depth dependent on the load only.

  7. Atomic layer deposition of HfO2 on graphene through controlled ion beam treatment

    International Nuclear Information System (INIS)

    Kim, Ki Seok; Oh, Il-Kwon; Jung, Hanearl; Kim, Hyungjun; Yeom, Geun Young; Kim, Kyong Nam

    2016-01-01

    The polymer residue generated during the graphene transfer process to the substrate tends to cause problems (e.g., a decrease in electron mobility, unwanted doping, and non-uniform deposition of the dielectric material). In this study, by using a controllable low-energy Ar + ion beam, we cleaned the polymer residue without damaging the graphene network. HfO 2 grown by atomic layer deposition on graphene cleaned using an Ar + ion beam showed a dense uniform structure, whereas that grown on the transferred graphene (before Ar + ion cleaning) showed a non-uniform structure. A graphene–HfO 2 –metal capacitor fabricated by growing 20-nm thick HfO 2 on graphene exhibited a very low leakage current (<10 −11 A/cm 2 ) for Ar + ion-cleaned graphene, whereas a similar capacitor grown using the transferred graphene showed high leakage current.

  8. Graphene Coatings: Probing the Limits of the One Atom Thick Protection Layer

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Balog, Richard

    2012-01-01

    The limitations of graphene as an effective corrosion-inhibiting coating on metal surfaces, here exemplified by the hex-reconstructed Pt(100) surface, are probed by scanning tunneling microscopy measurements and density functional theory calculations. While exposure of small molecules directly onto...... against CO is observed at CO pressures below 106 mbar. However, at higher pressures CO is observed to intercalate under the graphene coating layer, thus lifting the reconstruction. The limitations of the coating effect are further tested by exposure to hot atomic hydrogen. While the coating can withstand...... these extreme conditions for a limited amount of time, after substantial exposure, the Pt(100) reconstruction is lifted. Annealing experiments and density functional theory calculations demonstrate that the basal plane of the graphene stays intact and point to a graphene-mediated mechanism for the H...

  9. Dynamic Modeling for the Design and Cyclic Operation of an Atomic Layer Deposition (ALD Reactor

    Directory of Open Access Journals (Sweden)

    Curtisha D. Travis

    2013-08-01

    Full Text Available A laboratory-scale atomic layer deposition (ALD reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to simulate the complete reactor system. Limit-cycle solutions defining continuous cyclic ALD reactor operation are computed with a fixed point algorithm based on collocation discretization in time, resulting in an unambiguous definition of film growth-per-cycle (gpc. A key finding of this study is that unintended chemical vapor deposition conditions can mask regions of operation that would otherwise correspond to ideal saturating ALD operation. The use of the simulator for assisting in process design decisions is presented.

  10. Pulsed Plasma with Synchronous Boundary Voltage for Rapid Atomic Layer Etching

    Energy Technology Data Exchange (ETDEWEB)

    Economou, Demetre J.; Donnelly, Vincent M.

    2014-05-13

    Atomic Layer ETching (ALET) of a solid with monolayer precision is a critical requirement for advancing nanoscience and nanotechnology. Current plasma etching techniques do not have the level of control or damage-free nature that is needed for patterning delicate sub-20 nm structures. In addition, conventional ALET, based on pulsed gases with long reactant adsorption and purging steps, is very slow. In this work, novel pulsed plasma methods with synchronous substrate and/or “boundary electrode” bias were developed for highly selective, rapid ALET. Pulsed plasma and tailored bias voltage waveforms provided controlled ion energy and narrow energy spread, which are critical for highly selective and damage-free etching. The broad goal of the project was to investigate the plasma science and engineering that will lead to rapid ALET with monolayer precision. A combined experimental-simulation study was employed to achieve this goal.

  11. Atomic-layer-deposited WNxCy thin films as diffusion barrier for copper metallization

    Science.gov (United States)

    Kim, Soo-Hyun; Oh, Su Suk; Kim, Ki-Bum; Kang, Dae-Hwan; Li, Wei-Min; Haukka, Suvi; Tuominen, Marko

    2003-06-01

    The properties of WNxCy films deposited by atomic layer deposition (ALD) using WF6, NH3, and triethyl boron as source gases were characterized as a diffusion barrier for copper metallization. It is noted that the as-deposited film shows an extremely low resistivity of about 350 μΩ cm with a film density of 15.37 g/cm3. The film composition measured from Rutherford backscattering spectrometry shows W, C, and N of ˜48, 32, and 20 at. %, respectively. Transmission electron microscopy analyses show that the as-deposited film is composed of face-centered-cubic phase with a lattice parameter similar to both β-WC1-x and β-W2N with an equiaxed microstructure. The barrier property of this ALD-WNxCy film at a nominal thickness of 12 nm deposited between Cu and Si fails only after annealing at 700 °C for 30 min.

  12. Building a Better Capacitor with Thin-Film Atomic Layer Deposition Processing

    Energy Technology Data Exchange (ETDEWEB)

    Pike, Christopher [North Seattle College, WA (United States)

    2015-08-28

    The goal of this research is to determine procedures for creating ultra-high capacity supercapacitors by using nanofabrication techniques and high k-value dielectrics. One way to potentially solve the problem of climate change is to switch the source of energy to a source that doesn’t release many tons of greenhouse gases, gases which cause global warming, into the Earth’s atmosphere. These trap in more heat from the Sun’s solar energy and cause global temperatures to rise. Atomic layer deposition will be used to create a uniform thin-film of dielectric to greatly enhance the abilities of our capacitors and will build them on the nanoscale.

  13. Controlled dielectrophoretic nanowire self-assembly using atomic layer deposition and suspended microfabricated electrodes

    International Nuclear Information System (INIS)

    Baca, Alicia I; Brown, Joseph J; Bright, Victor M; Bertness, Kris A

    2012-01-01

    Effects of design and materials on the dielectrophoretic self-assembly of individual gallium nitride nanowires (GaN NWs) onto microfabricated electrodes have been experimentally investigated. The use of TiO 2 surface coating generated by atomic layer deposition (ALD) improves dielectrophoretic assembly yield of individual GaN nanowires on microfabricated structures by as much as 67%. With a titanium dioxide coating, individual nanowires were placed across suspended electrode pairs in 46% of tests (147 out of 320 total), versus 28% of tests (88 out of 320 total tests) that used uncoated GaN NWs. An additional result from these tests was that suspending the electrodes 2.75 μm above the substrate corresponded with up to 15.8% improvement in overall assembly yield over that of electrodes fabricated directly on the substrate. (paper)

  14. Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

    International Nuclear Information System (INIS)

    Yong Shee Meng, Alvin; Zainal, Norzaini; Hassan, Zainuriah; Ibrahim, Kamarulazizi

    2015-01-01

    Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH_3 annealing thermal has been successfully demonstrated. • NH_3 annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH_3) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

  15. Angular behavior of the Berreman effect investigated in uniform Al2O3 layers formed by atomic layer deposition.

    Science.gov (United States)

    Scarel, Giovanna; Na, Jeong-Seok; Parsons, Gregory N

    2010-04-21

    Experimental transmission absorbance infrared spectra of γ-Al(2)O(3) showing evidence of the angular dependence of the peaks of surface modes appearing next to the longitudinal optical phonon frequency ω(LO) (the Berreman effect) are collected from heat-treated thin oxide films deposited with thickness uniformity on Si(100) using atomic layer deposition. The peak area of the most intense surface longitudinal optical mode is plotted versus the infrared beam incidence angle θ(0). The experimental points closely follow the sin(4)(θ(0)) function in a broad thickness range. The best match occurs at a critical thickness, where a linear relationship exists between the surface longitudinal optical mode intensity and film thickness. Simulations suggest that below the critical thickness the sin(4)(θ(0)) behavior can be explained by refraction phenomena at the air/thin film and thin film/substrate interfaces. Above the critical thickness, the experimentally obtained result is derived from field boundary conditions at the air/thin film interface. The sin(4)(θ(0)) functional trend breaks down far above the critical thickness. This picture indicates that infrared radiation has a limited penetration depth into the oxide film, similarly to electromagnetic waves in conductors. Consequently, surface longitudinal optical modes are viewed as bulk phonons excited down to the penetration depth of the infrared beam. Comparison with simulated data suggests that the infrared radiation absorptance of surface longitudinal optical modes tends to approach the sin(2)(θ(0)) trend. Reflection phenomena are considered to be the origin of the deviation from the sin(4)(θ(0)) trend related to refraction.

  16. Phosphorus atomic layer doping in SiGe using reduced pressure chemical vapor deposition

    International Nuclear Information System (INIS)

    Yamamoto, Yuji; Heinemann, Bernd; Murota, Junichi; Tillack, Bernd

    2014-01-01

    Phosphorus (P) atomic layer doping in SiGe is investigated at temperatures between 100 °C to 600 °C using a single wafer reduced pressure chemical vapor deposition system. SiGe(100) surface is exposed to PH 3 at different PH 3 partial pressures by interrupting SiGe growth. The impact of the SiGe buffer/cap growth condition (total pressure/SiGe deposition precursors) on P adsorption, incorporation, and segregation are investigated. In the case of SiH 4 -GeH 4 -H 2 gas system, steeper P spikes due to lower segregation are observed by SiGe cap deposition at atmospheric (ATM) pressure compared with reduced pressure (RP). The steepness of P spike of ∼ 5.7 nm/dec is obtained for ATM pressure without reducing deposition temperature. This result may be due to the shift of equilibrium of P adsorption/desorption to desorption direction by higher H 2 pressure. Using Si 2 H 6 -GeH 4 -H 2 gas system for SiGe cap deposition in RP, lowering the SiGe growth temperature is possible, resulting in higher P incorporation and steeper P profile due to reduced desorption and segregation. In the case of Si 2 H 6 -GeH 4 -H 2 gas system, the P dose could be simulated assuming a Langmuir-type kinetics model. Incorporated P shows high electrical activity, indicating P is adsorbed mostly in lattice position. - Highlights: • Phosphorus (P) atomic layer doping in SiGe (100) is investigated using CVD. • P adsorption is suppressed by the hydrogen termination of Ge surface. • By SiGe cap deposition at atmospheric pressure, P segregation was suppressed. • By using Si 2 H 6 -based SiGe cap, P segregation was also suppressed. • The P adsorption process is self-limited and follows Langmuir-type kinetics model

  17. The effect of substrate temperature on atomic layer deposited zinc tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Lindahl, Johan, E-mail: johan.lindahl@angstrom.uu.se; Hägglund, Carl, E-mail: carl.hagglund@angstrom.uu.se; Wätjen, J. Timo, E-mail: timo.watjen@angstrom.uu.se; Edoff, Marika, E-mail: marika.edoff@angstrom.uu.se; Törndahl, Tobias, E-mail: tobias.torndahl@angstrom.uu.se

    2015-07-01

    Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 °C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnO{sub x} ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm{sup 3} in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (~ 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature. - Highlights: • Zinc tin oxide thin films were deposited by atomic layer deposition. • The structure and optical properties were studied at different growth temperatures. • The growth temperature had only a small effect on the composition of the films. • Small ZnO or ZnO(Sn) crystallites were observed by TEM in zinc rich ZTO films. • The growth temperature affects the crystallite size, which influences the band gap.

  18. The effect of substrate temperature on atomic layer deposited zinc tin oxide

    International Nuclear Information System (INIS)

    Lindahl, Johan; Hägglund, Carl; Wätjen, J. Timo; Edoff, Marika; Törndahl, Tobias

    2015-01-01

    Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 °C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnO x ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm 3 in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (~ 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature. - Highlights: • Zinc tin oxide thin films were deposited by atomic layer deposition. • The structure and optical properties were studied at different growth temperatures. • The growth temperature had only a small effect on the composition of the films. • Small ZnO or ZnO(Sn) crystallites were observed by TEM in zinc rich ZTO films. • The growth temperature affects the crystallite size, which influences the band gap

  19. Protective coatings of hafnium dioxide by atomic layer deposition for microelectromechanical systems applications

    Energy Technology Data Exchange (ETDEWEB)

    Berdova, Maria, E-mail: maria.berdova@aalto.fi [Aalto University, Department of Materials Science and Engineering, 02150, Espoo (Finland); Wiemer, Claudia; Lamperti, Alessio; Tallarida, Grazia; Cianci, Elena [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864, Agrate Brianza, MB (Italy); Lamagna, Luca; Losa, Stefano; Rossini, Silvia; Somaschini, Roberto; Gioveni, Salvatore [STMicroelectronics, Via C. Olivetti 2, 20864, Agrate Brianza, MB (Italy); Fanciulli, Marco [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864, Agrate Brianza, MB (Italy); Università degli studi di Milano Bicocca, Dipartimento di Scienza dei Materiali, 20126, Milano (Italy); Franssila, Sami, E-mail: sami.franssila@aalto.fi [Aalto University, Department of Materials Science and Engineering, 02150, Espoo (Finland)

    2016-04-15

    Graphical abstract: - Highlights: • Atomic layer deposition of HfO{sub 2} from (CpMe){sub 2}Hf(OMe)Me or Hf(NMeEt){sub 4} and ozone for potential applications in microelectromechanical systems. • ALD HfO{sub 2} protects aluminum substrates from degradation in moist environment and at the same time retains good reflectance properties of the underlying material. • The resistance of hafnium dioxide to moist environment is independent of chosen precursors. - Abstract: This work presents the investigation of HfO{sub 2} deposited by atomic layer deposition (ALD) from either HfD-CO4 or TEMAHf and ozone for microelectromechanical systems (MEMS) applications, in particular, for environmental protection of aluminum micromirrors. This work shows that HfO{sub 2} films successfully protect aluminum in moist environment and at the same time retain good reflectance properties of underlying material. In our experimental work, the chemical composition, crystal structure, electronic density and roughness of HfO{sub 2} films remained the same after one week of humidity treatment (relative humidity of 85%, 85 °C). The reflectance properties underwent only minor changes. The observed shift in reflectance was only from 80–90% to 76–85% in 400–800 nm spectral range when coated with ALD HfO{sub 2} films grown with Hf(NMeEt){sub 4} and no shift (remained in the range of 68–83%) for films grown from (CpMe){sub 2}Hf(OMe)Me.

  20. Self-limiting atomic layer deposition of conformal nanostructured silver films

    International Nuclear Information System (INIS)

    Golrokhi, Zahra; Chalker, Sophia; Sutcliffe, Christopher J.; Potter, Richard J.

    2016-01-01

    Graphical abstract: - Highlights: • We grow metallic silver by direct liquid injection thermal atomic layer deposition. • Highly conformal silver nanoparticle coatings on high aspect ratio surfaces. • An ALD temperature growth window between 123 and 128 °C is established. • ALD cycles provides sub nanometre control of silver growth. • Catalytic dehydrogenation ALD mechanism has been elucidated by in-situ QCM. - Abstract: The controlled deposition of ultra-thin conformal silver nanoparticle films is of interest for applications including anti-microbial surfaces, plasmonics, catalysts and sensors. While numerous techniques can produce silver nanoparticles, few are able to produce highly conformal coatings on high aspect ratio surfaces, together with sub-nanometre control and scalability. Here we develop a self-limiting atomic layer deposition (ALD) process for the deposition of conformal metallic silver nanoparticle films. The films have been deposited using direct liquid injection ALD with ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) and propan-1-ol. An ALD temperature window between 123 and 128 °C is identified and within this range self-limiting growth is confirmed with a mass deposition rate of ∼17.5 ng/cm"2/cycle. The effects of temperature, precursor dose, co-reactant dose and cycle number on the deposition rate and on the properties of the films have been systematically investigated. Under self-limiting conditions, films are metallic silver with a nano-textured surface topography and nanoparticle size is dependent on the number of ALD cycles. The ALD reaction mechanisms have been elucidated using in-situ quartz crystal microbalance (QCM) measurements, showing chemisorption of the silver precursor, followed by heterogeneous catalytic dehydrogenation of the alcohol to form metallic silver and an aldehyde.

  1. Rapid capless annealing of28Si,64Zn, and9Be implants in GaAs

    Science.gov (United States)

    Liu, S. G.; Narayan, S. Y.

    1984-11-01

    We report the use of tungsten-halogen lamps for rapid (-10 s) thermal annealing of ion-implanted (100) GaAs under AsH3/Ar and N2 atmospheres. Annealing under flowing AsH3/Ar was carried out without wafer encapsulation. Rapid capless annealing activated implants in GaAs with good mobility and surface morphology. Typical mobilities were 3700 4500 cm2/V-s for n-layers with about 2×1017cm-3 carrier concentration and 50 150 cm2/v-s for 0.1 5xl019 cm-3 doped p-layers. Rapid thermal annealing was performed in a vertical quartz tube where different gases (N2, AsH3/H2, AsH3/Ar) can be introduced. Samples were encapsulated with SiO when N2 was used. Tungsten-halogen lamps of 600 or 1000 W were utilized for annealing GaAs wafers ranging from 1 to 10 cm2 in area and 0.025 to 0.040 cm in thickness. The transient temperature at the wafer position was monitored using a fine thermocouple. We carried out experiments for energies of 30 to 200 keV, doses of 2×1012 to 1×1015 cm-2, and peak temperatures ranging from 600 to 1000‡C. Most results quoted are in the 700 to 870‡C temperature range. Data on implant conditions, optimum anneal conditions, electrical characteristics, carrier concentration profiles, and atomic profiles of the implanted layers are described.

  2. Pt thermal atomic layer deposition for silicon x-ray micropore optics.

    Science.gov (United States)

    Takeuchi, Kazuma; Ezoe, Yuichiro; Ishikawa, Kumi; Numazawa, Masaki; Terada, Masaru; Ishi, Daiki; Fujitani, Maiko; Sowa, Mark J; Ohashi, Takaya; Mitsuda, Kazuhisa

    2018-04-20

    We fabricated a silicon micropore optic using deep reactive ion etching and coated by Pt with atomic layer deposition (ALD). We confirmed that a metal/metal oxide bilayer of Al 2 O 3 ∼10  nm and Pt ∼20  nm was successfully deposited on the micropores whose width and depth are 20 μm and 300 μm, respectively. An increase of surface roughness of sidewalls of the micropores was observed with a transmission electron microscope and an atomic force microscope. X-ray reflectivity with an Al Kα line at 1.49 keV before and after the deposition was measured and compared to ray-tracing simulations. The surface roughness of the sidewalls was estimated to increase from 1.6±0.2  nm rms to 2.2±0.2  nm rms. This result is consistent with the microscope measurements. Post annealing of the Pt-coated optic at 1000°C for 2 h showed a sign of reduced surface roughness and better angular resolution. To reduce the surface roughness, possible methods such as the annealing after deposition and a plasma-enhanced ALD are discussed.

  3. Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage.

    Science.gov (United States)

    Guan, Cao; Wang, John

    2016-10-01

    Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

  4. Uniform GaN thin films grown on (100) silicon by remote plasma atomic layer deposition

    International Nuclear Information System (INIS)

    Shih, Huan-Yu; Chen, Miin-Jang; Lin, Ming-Chih; Chen, Liang-Yih

    2015-01-01

    The growth of uniform gallium nitride (GaN) thin films was reported on (100) Si substrate by remote plasma atomic layer deposition (RP-ALD) using triethylgallium (TEG) and NH 3 as the precursors. The self-limiting growth of GaN was manifested by the saturation of the deposition rate with the doses of TEG and NH 3 . The increase in the growth temperature leads to the rise of nitrogen content and improved crystallinity of GaN thin films, from amorphous at a low deposition temperature of 200 °C to polycrystalline hexagonal structures at a high growth temperature of 500 °C. No melting-back etching was observed at the GaN/Si interface. The excellent uniformity and almost atomic flat surface of the GaN thin films also infer the surface control mode of the GaN thin films grown by the RP-ALD technique. The GaN thin films grown by RP-ALD will be further applied in the light-emitting diodes and high electron mobility transistors on (100) Si substrate. (paper)

  5. Atomic layer deposition of copper thin film and feasibility of deposition on inner walls of waveguides

    Science.gov (United States)

    Yuqing, XIONG; Hengjiao, GAO; Ni, REN; Zhongwei, LIU

    2018-03-01

    Copper thin films were deposited by plasma-enhanced atomic layer deposition at low temperature, using copper(I)-N,N‧-di-sec-butylacetamidinate as a precursor and hydrogen as a reductive gas. The influence of temperature, plasma power, mode of plasma, and pulse time, on the deposition rate of copper thin film, the purity of the film and the step coverage were studied. The feasibility of copper film deposition on the inner wall of a carbon fibre reinforced plastic waveguide with high aspect ratio was also studied. The morphology and composition of the thin film were studied by atomic force microscopy and x-ray photoelectron spectroscopy, respectively. The square resistance of the thin film was also tested by a four-probe technique. On the basis of on-line diagnosis, a growth mechanism of copper thin film was put forward, and it was considered that surface functional group played an important role in the process of nucleation and in determining the properties of thin films. A high density of plasma and high free-radical content were helpful for the deposition of copper thin films.

  6. Atomic diffusion induced degradation in bimetallic layer coated cemented tungsten carbide

    International Nuclear Information System (INIS)

    Peng, Zirong; Rohwerder, Michael; Choi, Pyuck-Pa; Gault, Baptiste; Meiners, Thorsten; Friedrichs, Marcel; Kreilkamp, Holger; Klocke, Fritz; Raabe, Dierk

    2017-01-01

    Highlights: • We study the temporal degradation of PtIr/Cr/WC and PtIr/Ni/WC systems. • Short cut diffusion, segregation, oxidation and interdiffusion reactions occurred. • Outward diffusion of Cr (Ni) via PtIr grain boundaries triggered the degradation. • The microstructure of the PtIr layer controlled the systems stability. • We propose an atomic diffusion induced degradation mechanism. - Abstract: We investigated the temporal degradation of glass moulding dies, made of cemented tungsten carbide coated with PtIr on an adhesive Cr or Ni interlayer, by electron microscopy and atom probe tomography. During the exposure treatments at 630 °C under an oxygen partial pressure of 1.12 × 10"−"2"3 bar, Cr (Ni) was found to diffuse outwards via grain boundaries in the PtIr, altering the surface morphology. Upon dissolution of the interlayer, the WC substrate also started degrading. Extensive interdiffusion processes involving PtIr, Cr (Ni) and WC took place, leading to the formation of intermetallic phases and voids, deteriorating the adhesion of the coating.

  7. Growth kinetics and initial stage growth during plasma-enhanced Ti atomic layer deposition

    CERN Document Server

    Kim, H

    2002-01-01

    We have investigated the growth kinetics of plasma-enhanced Ti atomic layer deposition (ALD) using a quartz crystal microbalance. Ti ALD films were grown at temperatures from 20 to 200 deg. C using TiCl sub 4 as a source gas and rf plasma-produced atomic H as the reducing agent. Postdeposition ex situ chemical analyses of thin films showed that the main impurity is oxygen, mostly incorporated during the air exposure prior to analysis. The thickness per cycle, corresponding to the growth rate, was measured by quartz crystal microbalance as a function of various key growth parameters, including TiCl sub 4 and H exposure time, rf plasma power, and sample temperature. The growth rates were independent of TiCl sub 4 exposure above 1x10 sup 3 L, indicating typical ALD mode growth. The key kinetic parameters for Cl extraction reaction and TiCl sub 4 adsorption kinetics were obtained and the growth kinetics were modeled to predict the growth rates based upon these results. Also, the dependency of growth kinetics on d...

  8. Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

    KAUST Repository

    Kim, Hyunho

    2017-02-27

    Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as a zinc precursor. No substitutional atoms have been added to the ZnO films. By using ozone as an oxidant instead of water, a thermoelectric power factor (σS) of 5.76 × 10 W m K is obtained at 705 K for undoped ZnO films. In contrast, the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn-related defects present in the ZnO films. The data suggest that the strong oxidant effect on thermoelectric performance can be explained by a mechanism involving point defect-induced differences in carrier concentration between these two oxides and a self-compensation effect in water-based ZnO due to the competitive formations of both oxygen and zinc vacancies. This strong oxidant effect on the thermoelectric properties of undoped ZnO films provides a pathway to improve the thermoelectric performance of this important material.

  9. Computer simulations of an oxygen inductively coupled plasma used for plasma-assisted atomic layer deposition

    International Nuclear Information System (INIS)

    Tinck, S; Bogaerts, A

    2011-01-01

    In this paper, an O 2 inductively coupled plasma used for plasma enhanced atomic layer deposition of Al 2 O 3 thin films is investigated by means of modeling. This work intends to provide more information about basic plasma properties such as species densities and species fluxes to the substrate as a function of power and pressure, which might be hard to measure experimentally. For this purpose, a hybrid model developed by Kushner et al is applied to calculate the plasma characteristics in the reactor volume for different chamber pressures ranging from 1 to 10 mTorr and different coil powers ranging from 50 to 500 W. Density profiles of the various oxygen containing plasma species are reported as well as fluxes to the substrate under various operating conditions. Furthermore, different orientations of the substrate, which can be placed vertically or horizontally in the reactor, are taken into account. In addition, special attention is paid to the recombination process of atomic oxygen on the different reactor walls under the stated operating conditions. From this work it can be concluded that the plasma properties change significantly in different locations of the reactor. The plasma density near the cylindrical coil is high, while it is almost negligible in the neighborhood of the substrate. Ion and excited species fluxes to the substrate are found to be very low and negligible. Finally, the orientation of the substrate has a minor effect on the flux of O 2 , while it has a significant effect on the flux of O. In the horizontal configuration, the flux of atomic oxygen can be up to one order of magnitude lower than in the vertical configuration.

  10. Atomic Layer Deposition of Chemical Passivation Layers and High Performance Anti-Reflection Coatings on Back-Illuminated Detectors

    Science.gov (United States)

    Hoenk, Michael E. (Inventor); Greer, Frank (Inventor); Nikzad, Shouleh (Inventor)

    2014-01-01

    A back-illuminated silicon photodetector has a layer of Al2O3 deposited on a silicon oxide surface that receives electromagnetic radiation to be detected. The Al2O3 layer has an antireflection coating deposited thereon. The Al2O3 layer provides a chemically resistant separation layer between the silicon oxide surface and the antireflection coating. The Al2O3 layer is thin enough that it is optically innocuous. Under deep ultraviolet radiation, the silicon oxide layer and the antireflection coating do not interact chemically. In one embodiment, the silicon photodetector has a delta-doped layer near (within a few nanometers of) the silicon oxide surface. The Al2O3 layer is expected to provide similar protection for doped layers fabricated using other methods, such as MBE, ion implantation and CVD deposition.

  11. Atmospheric spatial atomic-layer-deposition of Zn(O, S) buffer layer for flexible Cu(In, Ga)Se2 solar cells: From lab-scale to large area roll to roll processing

    NARCIS (Netherlands)

    Frijters, C.H.; Bolt, P.J.; Poodt, P.W.G.; Knaapen, R.; Brink, J. van den; Ruth, M.; Bremaud, D.; Illiberi, A.

    2016-01-01

    In this manuscript we present the first successful application of a spatial atomic-layer-deposition process to thin film solar cells. Zn(O,S) has been grown by spatial atomic layer deposition (S-ALD) at atmospheric pressure and applied as buffer layer in rigid and flexible CIGS cells by a lab-scale

  12. The fabrication of a double-layer atom chip with through silicon vias for an ultra-high-vacuum cell

    International Nuclear Information System (INIS)

    Chuang, Ho-Chiao; Lin, Yun-Siang; Lin, Yu-Hsin; Huang, Chi-Sheng

    2014-01-01

    This study presents a double-layer atom chip that provides users with increased diversity in the design of the wire patterns and flexibility in the design of the magnetic field. It is more convenient for use in atomic physics experiments. A negative photoresist, SU-8, was used as the insulating layer between the upper and bottom copper wires. The electrical measurement results show that the upper and bottom wires with a width of 100 µm can sustain a 6 A current without burnout. Another focus of this study is the double-layer atom chips integrated with the through silicon via (TSV) technique, and anodically bonded to a Pyrex glass cell, which makes it a desired vacuum chamber for atomic physics experiments. Thus, the bonded glass cell not only significantly reduces the overall size of the ultra-high-vacuum (UHV) chamber but also conducts the high current from the backside to the front side of the atom chip via the TSV under UHV (9.5 × 10 −10  Torr). The TSVs with a diameter of 70 µm were etched through by the inductively coupled plasma ion etching and filled by the bottom-up copper electroplating method. During the anodic bonding process, the electroplated copper wires and TSVs on atom chips also need to pass the examination of the required bonding temperature of 250 °C, under an applied voltage of 1000 V. Finally, the UHV test of the double-layer atom chips with TSVs at room temperature can be reached at 9.5 × 10 −10  Torr, thus satisfying the requirements of atomic physics experiments under an UHV environment. (paper)

  13. Stabilizing nanostructured solid oxide fuel cell cathode with atomic layer deposition.

    Science.gov (United States)

    Gong, Yunhui; Palacio, Diego; Song, Xueyan; Patel, Rajankumar L; Liang, Xinhua; Zhao, Xuan; Goodenough, John B; Huang, Kevin

    2013-09-11

    We demonstrate that the highly active but unstable nanostructured intermediate-temperature solid oxide fuel cell cathode, La0.6Sr0.4CoO3-δ (LSCo), can retain its high oxygen reduction reaction (ORR) activity with exceptional stability for 4000 h at 700 °C by overcoating its surfaces with a conformal layer of nanoscale ZrO2 films through atomic layer deposition (ALD). The benefits from the presence of the nanoscale ALD-ZrO2 overcoats are remarkable: a factor of 19 and 18 reduction in polarization area-specific resistance and degradation rate over the pristine sample, respectively. The unique multifunctionality of the ALD-derived nanoscaled ZrO2 overcoats, that is, possessing porosity for O2 access to LSCo, conducting both electrons and oxide-ions, confining thermal growth of LSCo nanoparticles, and suppressing surface Sr-segregation is deemed the key enabler for the observed stable and active nanostructured cathode.

  14. Fluidized bed coupled rotary reactor for nanoparticles coating via atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Chen-Long; Liu, Xiao; Chen, Rong, E-mail: rongchen@mail.hust.edu.cn, E-mail: bshan@mail.hust.edu.cn [State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074 (China); Shan, Bin, E-mail: rongchen@mail.hust.edu.cn, E-mail: bshan@mail.hust.edu.cn [State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074 (China)

    2015-07-15

    A fluidized bed coupled rotary reactor has been designed for coating on nanoparticles (NPs) via atomic layer deposition. It consists of five major parts: reaction chamber, dosing and fluidizing section, pumping section, rotary manipulator components, as well as a double-layer cartridge for the storage of particles. In the deposition procedure, continuous fluidization of particles enlarges and homogenizes the void fraction in the particle bed, while rotation enhances the gas-solid interactions to stabilize fluidization. The particle cartridge presented here enables both the fluidization and rotation acting on the particle bed, demonstrated by the analysis of pressure drop. Moreover, enlarged interstitials and intense gas–solid contact under sufficient fluidizing velocity and proper rotation speed facilitate the precursor delivery throughout the particle bed and consequently provide a fast coating process. The cartridge can ensure precursors flowing through the particle bed exclusively to achieve high utilization without static exposure operation. By optimizing superficial gas velocities and rotation speeds, minimum pulse time for complete coating has been shortened in experiment, and in situ mass spectrometry showed the precursor usage can reach 90%. Inductively coupled plasma-optical emission spectroscopy results suggested a saturated growth of nanoscale Al{sub 2}O{sub 3} films on spherical SiO{sub 2} NPs. Finally, the uniformity and composition of the shells were characterized by high angle annular dark field-transmission electron microscopy and energy dispersive X-ray spectroscopy.

  15. Atomic layer deposition in nanostructured photovoltaics: tuning optical, electronic and surface properties

    Science.gov (United States)

    Palmstrom, Axel F.; Santra, Pralay K.; Bent, Stacey F.

    2015-07-01

    Nanostructured materials offer key advantages for third-generation photovoltaics, such as the ability to achieve high optical absorption together with enhanced charge carrier collection using low cost components. However, the extensive interfacial areas in nanostructured photovoltaic devices can cause high recombination rates and a high density of surface electronic states. In this feature article, we provide a brief review of some nanostructured photovoltaic technologies including dye-sensitized, quantum dot sensitized and colloidal quantum dot solar cells. We then introduce the technique of atomic layer deposition (ALD), which is a vapor phase deposition method using a sequence of self-limiting surface reaction steps to grow thin, uniform and conformal films. We discuss how ALD has established itself as a promising tool for addressing different aspects of nanostructured photovoltaics. Examples include the use of ALD to synthesize absorber materials for both quantum dot and plasmonic solar cells, to grow barrier layers for dye and quantum dot sensitized solar cells, and to infiltrate coatings into colloidal quantum dot solar cell to improve charge carrier mobilities as well as stability. We also provide an example of monolayer surface modification in which adsorbed ligand molecules on quantum dots are used to tune the band structure of colloidal quantum dot solar cells for improved charge collection. Finally, we comment on the present challenges and future outlook of the use of ALD for nanostructured photovoltaics.

  16. Environmental sensing with optical fiber sensors processed with focused ion beam and atomic layer deposition

    Science.gov (United States)

    Flores, Raquel; Janeiro, Ricardo; Dahlem, Marcus; Viegas, Jaime

    2015-03-01

    We report an optical fiber chemical sensor based on a focused ion beam processed optical fiber. The demonstrated sensor is based on a cavity formed onto a standard 1550 nm single-mode fiber by either chemical etching, focused ion beam milling (FIB) or femtosecond laser ablation, on which side channels are drilled by either ion beam milling or femtosecond laser irradiation. The encapsulation of the cavity is achieved by optimized fusion splicing onto a standard single or multimode fiber. The empty cavity can be used as semi-curved Fabry-Pérot resonator for gas or liquid sensing. Increased reflectivity of the formed cavity mirrors can be achieved with atomic layer deposition (ALD) of alternating metal oxides. For chemical selective optical sensors, we demonstrate the same FIB-formed cavity concept, but filled with different materials, such as polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA) which show selective swelling when immersed in different solvents. Finally, a reducing agent sensor based on a FIB formed cavity partially sealed by fusion splicing and coated with a thin ZnO layer by ALD is presented and the results discussed. Sensor interrogation is achieved with spectral or multi-channel intensity measurements.

  17. Ru nanostructure fabrication using an anodic aluminum oxide nanotemplate and highly conformal Ru atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo-Hee; Park, Sang-Joon; Son, Jong-Yeog; Kim, Hyungjun [Department of Material Science and Engineering, POSTECH Pohang University of Science and Technology, San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea, Republic of)

    2008-01-30

    We fabricated metallic nanostructures directly on Si substrates through a hybrid nanoprocess combining atomic layer deposition (ALD) and a self-assembled anodic aluminum oxide (AAO) nanotemplate. ALD Ru films with Ru(DMPD)(EtCp) as a precursor and O{sub 2} as a reactant exhibited high purity and low resistivity with negligible nucleation delay and low roughness. These good growth characteristics resulted in the excellent conformality for nanometer-scale vias and trenches. Additionally, AAO nanotemplates were fabricated directly on Si and Ti/Si substrates through a multiple anodization process. AAO nanotemplates with various hole sizes (30-100 nm) and aspect ratios (2:1-20:1) were fabricated by controlling the anodizing process parameters. The barrier layers between AAO nanotemplates and Si substrates were completely removed by reactive ion etching (RIE) using BCl{sub 3} plasma. By combining the ALD Ru and the AAO nanotemplate, Ru nanostructures with controllable sizes and shapes were prepared on Si and Ti/Si substrates. The Ru nanowire array devices as a platform for sensor devices exhibited befitting properties of good ohmic contact and high surface/volume ratio.

  18. Atomic layer deposition synthesis and evaluation of core–shell Pt-WC electrocatalysts

    International Nuclear Information System (INIS)

    Hsu, Irene J.; Chen, Jingguang G.; Jiang, Xiaoqiang; Willis, Brian G.

    2015-01-01

    Pt-WC core shell particles were produced using atomic layer deposition (ALD) to deposit Pt layers onto WC particle substrates. A range of Pt depositions were used to determine the growth mechanism for the Pt-WC powder system. TEM imaging and Cu stripping voltammetry found that Pt ALD growth on WC powder substrates was similar to that on WC thin films. However, excess free carbon was found to affect Pt ALD by blocking adsorption sites on WC. The Pt-WC samples were evaluated for the oxygen reduction reaction using a rotating disk electrode to obtain quantitative activity information. The mass and specific activities for the 30 and 50 ALD cycle samples were found to be comparable to a 10 wt. % Pt/C catalyst. However, higher overpotentials and lower limiting currents were observed with ALD Pt-WC compared to Pt/C catalysts, indicating that the oxygen reduction mechanism is not as efficient on Pt-WC as on bulk Pt. Additionally, these Pt-WC catalysts were used to demonstrate hydrogen evolution reaction activity and were found to perform as well as bulk Pt catalyst but with a fraction of the Pt loading, in agreement with the previous work on Pt-WC thin film catalysts

  19. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber.

    Science.gov (United States)

    Dechana, A; Thamboon, P; Boonyawan, D

    2014-10-01

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films-analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques-will be discussed.

  20. An Experiment to Study Sporadic Atom Layers in the Earth's Mesosphere and Lower Thermosphere (SAL)

    Science.gov (United States)

    Kelley, Michael C.

    1999-01-01

    The Sudden Atom Layer (SAL) Rocket was successfully launched in February 1998. All instruments worked well except those supplied by NASA Goddard Space Flight Center. (A dummy weight was launched for the neutral mass spectrometer and the ion version died shortly after lift-off.) A paper has already been published in GRL concerning the dust layer detected by an on board instrument and compared to ground-based observations made at the Arecibo Observatory by Cornell graduate student S. Collins (lidar) and Q. Zhou (radar). Collins presented a comparison of the sodium lidar data and onboard observations with a theoretical model by Plane and Cox at the Fan AGU Meeting. In addition Gelinas and Kelley presented a review paper dealing with the entire SAL instrument complement at the same meeting. An unexpected new explanation for the outer scale of E region plasma irregularities has come out of the data set. We anticipate at least a total of four papers will be published within a year of launch.

  1. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    Energy Technology Data Exchange (ETDEWEB)

    Dechana, A. [Program of Physics and General Science, Faculty of Science and Technology, Songkhla Rajabhat University, Songkhla 90000 (Thailand); Thamboon, P. [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50200 (Thailand); Boonyawan, D., E-mail: dheerawan.b@cmu.ac.th [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2014-10-15

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al{sub 2}O{sub 3} layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al{sub 2}O{sub 3} films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

  2. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    Science.gov (United States)

    Dechana, A.; Thamboon, P.; Boonyawan, D.

    2014-10-01

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

  3. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    International Nuclear Information System (INIS)

    Dechana, A.; Thamboon, P.; Boonyawan, D.

    2014-01-01

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al 2 O 3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al 2 O 3 films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed

  4. Atomic Layer Deposition of Silicon Nitride from Bis(tert-butylamino)silane and N2 Plasma.

    Science.gov (United States)

    Knoops, Harm C M; Braeken, Eline M J; de Peuter, Koen; Potts, Stephen E; Haukka, Suvi; Pore, Viljami; Kessels, Wilhelmus M M

    2015-09-09

    Atomic layer deposition (ALD) of silicon nitride (SiNx) is deemed essential for a variety of applications in nanoelectronics, such as gate spacer layers in transistors. In this work an ALD process using bis(tert-butylamino)silane (BTBAS) and N2 plasma was developed and studied. The process exhibited a wide temperature window starting from room temperature up to 500 °C. The material properties and wet-etch rates were investigated as a function of plasma exposure time, plasma pressure, and substrate table temperature. Table temperatures of 300-500 °C yielded a high material quality and a composition close to Si3N4 was obtained at 500 °C (N/Si=1.4±0.1, mass density=2.9±0.1 g/cm3, refractive index=1.96±0.03). Low wet-etch rates of ∼1 nm/min were obtained for films deposited at table temperatures of 400 °C and higher, similar to that achieved in the literature using low-pressure chemical vapor deposition of SiNx at >700 °C. For novel applications requiring significantly lower temperatures, the temperature window from room temperature to 200 °C can be a solution, where relatively high material quality was obtained when operating at low plasma pressures or long plasma exposure times.

  5. Photoluminescence enhancement in porous SiC passivated by atomic layer deposited Al2O3 films

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    2016-01-01

    Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved.......Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved....

  6. Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

    Energy Technology Data Exchange (ETDEWEB)

    Yong Shee Meng, Alvin [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia); Zainal, Norzaini, E-mail: norzaini@usm.my [Nano Optoelectronics Research and Laboratory, Universiti Sains Malaysia, sains@usm, Persiaran Bukit Jambul, 11900, Bayan Lepas, Penang (Malaysia); Hassan, Zainuriah; Ibrahim, Kamarulazizi [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia)

    2015-12-30

    Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH{sub 3} annealing thermal has been successfully demonstrated. • NH{sub 3} annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH{sub 3}) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

  7. Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications

    International Nuclear Information System (INIS)

    Maydannik, Philipp S.; Kääriäinen, Tommi O.; Lahtinen, Kimmo; Cameron, David C.; Söderlund, Mikko; Soininen, Pekka; Johansson, Petri; Kuusipalo, Jurkka; Moro, Lorenza; Zeng, Xianghui

    2014-01-01

    At present flexible electronic devices are under extensive development and, among them, flexible organic light-emitting diode displays are the closest to a large market deployment. One of the remaining unsolved challenges is high throughput production of impermeable flexible transparent barrier layers that protect sensitive light-emitting materials against ambient moisture. The present studies deal with the adaptation of the atomic layer deposition (ALD) process to high-throughput roll-to-roll production using the spatial ALD concept. We report the development of such a process for the deposition of 20 nm thickness Al 2 O 3 diffusion barrier layers on 500 mm wide polymer webs. The process uses trimethylaluminum and water as precursors at a substrate temperature of 105 °C. The observation of self-limiting film growth behavior and uniformity of thickness confirms the ALD growth mechanism. Water vapor transmission rates for 20 nm Al 2 O 3 films deposited on polyethylene naphthalate (PEN) substrates were measured as a function of substrate residence time, that is, time of exposure of the substrate to one precursor zone. Moisture permeation levels measured at 38 °C/90% relative humidity by coulometric isostatic–isobaric method were below the detection limit of the instrument ( −4  g/m 2 day) for films coated at web moving speed of 0.25 m/min. Measurements using the Ca test indicated water vapor transmission rates ∼5 × 10 −6 g/m 2 day. Optical measurements on the coated web showed minimum transmission of 80% in the visible range that is the same as the original PEN substrate

  8. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Michael, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Schlaf, Rudy, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States)

    2015-08-14

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru{sup 0}) and its oxide (RuO{sub 2}) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru{sup 0} and RuO{sub 2} films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO{sub 2} and 0.04 Å/cycle for Ru.{sup 0} An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO{sub 2}/OH compound whose surface is saturated with hydroxyl groups.

  9. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Science.gov (United States)

    Schaefer, Michael; Schlaf, Rudy

    2015-08-01

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru0) and its oxide (RuO2) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru0 and RuO2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO2 and 0.04 Å/cycle for Ru.0 An interface dipole of up to -0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO2/OH compound whose surface is saturated with hydroxyl groups.

  10. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    International Nuclear Information System (INIS)

    Schaefer, Michael; Schlaf, Rudy

    2015-01-01

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru 0 ) and its oxide (RuO 2 ) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru 0 and RuO 2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO 2 and 0.04 Å/cycle for Ru. 0 An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO 2 /OH compound whose surface is saturated with hydroxyl groups

  11. Highly efficient computer algorithm for identifying layer thickness of atomically thin 2D materials

    Science.gov (United States)

    Lee, Jekwan; Cho, Seungwan; Park, Soohyun; Bae, Hyemin; Noh, Minji; Kim, Beom; In, Chihun; Yang, Seunghoon; Lee, Sooun; Seo, Seung Young; Kim, Jehyun; Lee, Chul-Ho; Shim, Woo-Young; Jo, Moon-Ho; Kim, Dohun; Choi, Hyunyong

    2018-03-01

    The fields of layered material research, such as transition-metal dichalcogenides (TMDs), have demonstrated that the optical, electrical and mechanical properties strongly depend on the layer number N. Thus, efficient and accurate determination of N is the most crucial step before the associated device fabrication. An existing experimental technique using an optical microscope is the most widely used one to identify N. However, a critical drawback of this approach is that it relies on extensive laboratory experiences to estimate N; it requires a very time-consuming image-searching task assisted by human eyes and secondary measurements such as atomic force microscopy and Raman spectroscopy, which are necessary to ensure N. In this work, we introduce a computer algorithm based on the image analysis of a quantized optical contrast. We show that our algorithm can apply to a wide variety of layered materials, including graphene, MoS2, and WS2 regardless of substrates. The algorithm largely consists of two parts. First, it sets up an appropriate boundary between target flakes and substrate. Second, to compute N, it automatically calculates the optical contrast using an adaptive RGB estimation process between each target, which results in a matrix with different integer Ns and returns a matrix map of Ns onto the target flake position. Using a conventional desktop computational power, the time taken to display the final N matrix was 1.8 s on average for the image size of 1280 pixels by 960 pixels and obtained a high accuracy of 90% (six estimation errors among 62 samples) when compared to the other methods. To show the effectiveness of our algorithm, we also apply it to TMD flakes transferred on optically transparent c-axis sapphire substrates and obtain a similar result of the accuracy of 94% (two estimation errors among 34 samples).

  12. Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications

    Energy Technology Data Exchange (ETDEWEB)

    Maydannik, Philipp S., E-mail: philipp.maydannik@lut.fi; Kääriäinen, Tommi O.; Lahtinen, Kimmo; Cameron, David C. [Advanced Surface Technology Research Laboratory, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli (Finland); Söderlund, Mikko; Soininen, Pekka [Beneq Oy, P.O. Box 262, 01511 Vantaa (Finland); Johansson, Petri; Kuusipalo, Jurkka [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 589, 33101 Tampere (Finland); Moro, Lorenza; Zeng, Xianghui [Samsung Cheil Industries, San Jose R and D Center, 2186 Bering Drive, San Jose, California 95131 (United States)

    2014-09-01

    At present flexible electronic devices are under extensive development and, among them, flexible organic light-emitting diode displays are the closest to a large market deployment. One of the remaining unsolved challenges is high throughput production of impermeable flexible transparent barrier layers that protect sensitive light-emitting materials against ambient moisture. The present studies deal with the adaptation of the atomic layer deposition (ALD) process to high-throughput roll-to-roll production using the spatial ALD concept. We report the development of such a process for the deposition of 20 nm thickness Al{sub 2}O{sub 3} diffusion barrier layers on 500 mm wide polymer webs. The process uses trimethylaluminum and water as precursors at a substrate temperature of 105 °C. The observation of self-limiting film growth behavior and uniformity of thickness confirms the ALD growth mechanism. Water vapor transmission rates for 20 nm Al{sub 2}O{sub 3} films deposited on polyethylene naphthalate (PEN) substrates were measured as a function of substrate residence time, that is, time of exposure of the substrate to one precursor zone. Moisture permeation levels measured at 38 °C/90% relative humidity by coulometric isostatic–isobaric method were below the detection limit of the instrument (<5 × 10{sup −4} g/m{sup 2} day) for films coated at web moving speed of 0.25 m/min. Measurements using the Ca test indicated water vapor transmission rates ∼5 × 10{sup −6} g/m{sup 2} day. Optical measurements on the coated web showed minimum transmission of 80% in the visible range that is the same as the original PEN substrate.

  13. Atomic Layer Deposited Thin Films for Dielectrics, Semiconductor Passivation, and Solid Oxide Fuel Cells

    Science.gov (United States)

    Xu, Runshen

    Atomic layer deposition (ALD) utilizes sequential precursor gas pulses to deposit one monolayer or sub-monolayer of material per cycle based on its self-limiting surface reaction, which offers advantages, such as precise thickness control, thickness uniformity, and conformality. ALD is a powerful means of fabricating nanoscale features in future nanoelectronics, such as contemporary sub-45 nm metal-oxide-semiconductor field effect transistors, photovoltaic cells, near- and far-infrared detectors, and intermediate temperature solid oxide fuel cells. High dielectric constant, kappa, materials have been recognized to be promising candidates to replace traditional SiO2 and SiON, because they enable good scalability of sub-45 nm MOSFET (metal-oxide-semiconductor field-effect transistor) without inducing additional power consumption and heat dissipation. In addition to high dielectric constant, high-kappa materials must meet a number of other requirements, such as low leakage current, high mobility, good thermal and structure stability with Si to withstand high-temperature source-drain activation annealing. In this thesis, atomic layer deposited Er2O3 doped TiO2 is studied and proposed as a thermally stable amorphous high-kappa dielectric on Si substrate. The stabilization of TiO2 in its amorphous state is found to achieve a high permittivity of 36, a hysteresis voltage of less than 10 mV, and a low leakage current density of 10-8 A/cm-2 at -1 MV/cm. In III-V semiconductors, issues including unsatisfied dangling bonds and native oxides often result in inferior surface quality that yields non-negligible leakage currents and degrades the long-term performance of devices. The traditional means for passivating the surface of III-V semiconductors are based on the use of sulfide solutions; however, that only offers good protection against oxidation for a short-term (i.e., one day). In this work, in order to improve the chemical passivation efficacy of III-V semiconductors

  14. Growth of AlN/Pt heterostructures on amorphous substrates at low temperatures via atomic layer epitaxy

    International Nuclear Information System (INIS)

    Nepal, N.; Goswami, R.; Qadri, S.B.; Mahadik, N.A.; Kub, F.J.; Eddy, C.R.

    2014-01-01

    Recent results on atomic layer epitaxy (ALE) growth and characterization of (0 0 0 1)AlN on highly oriented (1 1 1)Pt layers on amorphous HfO 2 /Si(1 0 0) are reported. HfO 2 was deposited by atomic layer deposition on Si(1 0 0) followed by ALE growth of Pt(15 nm) and, subsequently, AlN(60 nm) at 500 °C. Based on the X-ray diffraction and transmission electron microscopy measurements, the Pt and AlN layers are highly oriented along the (1 1 1) and (0 0 0 2) directions, respectively. Demonstrations of AlN/Pt heterostructures open up the possibility of new state-of-the-art microelectromechanical systems devices

  15. Plasma-enhanced atomic-layer-deposited MoO{sub x} emitters for silicon heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, Johannes; Schneider, Thomas; Sprafke, Alexander N. [Martin-Luther-University Halle-Wittenberg, mu-MD Group, Institute of Physics, Halle (Germany); Mews, Mathias; Korte, Lars [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Institute for Silicon-Photovoltaics, Berlin (Germany); Kaufmann, Kai [Fraunhofer Center for Silicon Photovoltaics CSP, Halle (Germany); University of Applied Sciences, Hochschule Anhalt Koethen, Koethen (Germany); Wehrspohn, Ralf B. [Martin-Luther-University Halle-Wittenberg, mu-MD Group, Institute of Physics, Halle (Germany); Fraunhofer Institute for Mechanics of Materials IWM Halle, Halle (Germany)

    2015-09-15

    A method for the deposition of molybdenum oxide (MoO{sub x}) with high growth rates at temperatures below 200 C based on plasma-enhanced atomic layer deposition is presented. The stoichiometry of the over-stoichiometric MoO{sub x} films can be adjusted by the plasma parameters. First results of these layers acting as hole-selective contacts in silicon heterojunction solar cells are presented and discussed. (orig.)

  16. TiN films by Atomic Layer Deposition: Growth and electrical characterization down to sub-nm thickness

    NARCIS (Netherlands)

    Van Hao, B.; Wolters, Robertus A.M.; Kovalgin, Alexeij Y.

    2012-01-01

    This study reports on the growth and characterization of TiN thib films obtained by atomic layer deposition at 350-425 ◦C. We observe a growth of the continuous layers from the very beginning of the process, i.e. for a thickness of 0.65 nm, which is equivalent to 3 monolayers of TiN. The film growth

  17. Comparison of MOVPE grown GaAs, InGaAs and GaAsSb covering layers for different InAs/GaAs quantum dot applications

    Czech Academy of Sciences Publication Activity Database

    Zíková, Markéta; Hospodková, Alice; Pangrác, Jiří; Oswald, Jiří; Hulicius, Eduard

    2017-01-01

    Roč. 464, Apr (2017), s. 59-63 ISSN 0022-0248 R&D Projects: GA MŠk LO1603 Institutional support: RVO:68378271 Keywords : MOVPE * quantum dot * strain reducing layer * InAs * GaAsSb * InGaAs Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.751, year: 2016

  18. Atomic layer deposition and post-growth thermal annealing of ultrathin MoO3 layers on silicon substrates: Formation of surface nanostructures

    Science.gov (United States)

    Liu, Hongfei; Yang, Ren Bin; Yang, Weifeng; Jin, Yunjiang; Lee, Coryl J. J.

    2018-05-01

    Ultrathin MoO3 layers have been grown on Si substrates at 120 °C by atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo(CO)6] and ozone (O3) as the Mo- and O-source precursors, respectively. The ultrathin films were further annealed in air at Tann = 550-750 °C for 15 min. Scanning-electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy have been employed to evaluate the morphological and elemental properties as well as their evolutions upon annealing of the thin films. They revealed an interfacial SiOx layer in between the MoO3 layer and the Si substrate; this SiOx layer converted into SiO2 during the annealing; and the equivalent thickness of the MoO3 (SiO2) layer decreased (increased) with the increase in Tann. Particles with diameters smaller than 50 nm emerged at Tann = 550 °C and their sizes (density) were reduced (increased) by increasing Tann to 650 °C. A further increase of Tann to 750 °C resulted in telephone-cord-like MoO3 structures, initiated from isolated particles on the surface. These observations have been discussed and interpreted based on temperature-dependent atomic interdiffusions, surface evaporations, and/or melting of MoO3, which shed new light on ALD MoO3 towards its electronic applications.

  19. Atomic layer-deposited Al–HfO{sub 2}/SiO{sub 2} bi-layers towards 3D charge trapping non-volatile memory

    Energy Technology Data Exchange (ETDEWEB)

    Congedo, Gabriele, E-mail: gabriele.congedo@mdm.imm.cnr.it; Wiemer, Claudia; Lamperti, Alessio; Cianci, Elena; Molle, Alessandro; Volpe, Flavio G.; Spiga, Sabina, E-mail: sabina.spiga@mdm.imm.cnr

    2013-04-30

    A metal/oxide/high-κ dielectric/oxide/silicon (MOHOS) planar charge trapping memory capacitor including SiO{sub 2} as tunnel oxide, Al–HfO{sub 2} as charge trapping layer, SiO{sub 2} as blocking oxide and TaN metal gate was fabricated and characterized as test vehicle in the view of integration into 3D cells. The thin charge trapping layer and blocking oxide were grown by atomic layer deposition, the technique of choice for the implementation of these stacks into 3D structures. The oxide stack shows a good thermal stability for annealing temperature of 900 °C in N{sub 2}, as required for standard complementary metal–oxide–semiconductor processes. MOHOS capacitors can be efficiently programmed and erased under the applied voltages of ± 20 V to ± 12 V. When compared to a benchmark structure including thin Si{sub 3}N{sub 4} as charge trapping layer, the MOHOS cell shows comparable program characteristics, with the further advantage of the equivalent oxide thickness scalability due to the high dielectric constant (κ) value of 32, and an excellent retention even for strong testing conditions. Our results proved that high-κ based oxide structures grown by atomic layer deposition can be of interest for the integration into three dimensionally stacked charge trapping devices. - Highlights: ► Charge trapping device with Al–HfO{sub 2} storage layer is fabricated and characterized. ► Al–HfO{sub 2} and SiO{sub 2} blocking oxides are deposited by atomic layer deposition. ► The oxide stack shows a good thermal stability after annealing at 900 °C. ► The device can be efficiently programmed/erased and retention is excellent. ► The oxide stack could be used for 3D-stacked Flash non-volatile memories.

  20. Atom

    International Nuclear Information System (INIS)

    Auffray, J.P.

    1997-01-01

    The atom through centuries, has been imagined, described, explored, then accelerated, combined...But what happens truly inside the atom? And what are mechanisms who allow its stability? Physicist and historian of sciences, Jean-Paul Auffray explains that these questions are to the heart of the modern physics and it brings them a new lighting. (N.C.)

  1. Heavily doped GaAs:Te layers grown by MOVPE using diisopropyl telluride as a source

    Energy Technology Data Exchange (ETDEWEB)

    Daniltsev, V. M.; Demidov, E. V.; Drozdov, M. N.; Drozdov, Yu. N., E-mail: drozdyu@ipmras.ru; Kraev, S. A.; Surovegina, E. A.; Shashkin, V. I.; Yunin, P. A. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2016-11-15

    The capabilities of GaAs epitaxial layers extremely heavily doped with tellurium by metal-organic vapor-phase epitaxy using diisopropyl telluride as a source are studied. It is shown that tellurium incorporation into GaAs occurs to an atomic concentration of 10{sup 21} cm{sup –3} without appreciable diffusion and segregation effects. Good carrier concentrations (2 × 10{sup 19} cm{sup –3}) and specific contact resistances of non-alloyed ohmic contacts (1.7 × 10{sup –6} Ω cm{sup 2}) give grounds to use such layers to create non-alloyed ohmic contacts in electronic devices. A sharp decrease in the electrical activity of Te atoms, a decrease in the electron mobility, and an increase in the contact resistance at atomic concentrations above 2 × 10{sup 20} cm{sup –3} are detected.

  2. Nitridation of porous GaAs by an ECR ammonia plasma

    International Nuclear Information System (INIS)

    Naddaf, M; Hullavarad, S S; Ganesan, V; Bhoraskar, S V

    2006-01-01

    The effect of surface porosity of GaAs on the nature of growth of GaN, by use of plasma nitridation of GaAs, has been investigated. Porous GaAs samples were prepared by anodic etching of n-type (110) GaAs wafers in HCl solution. Nitridation of porous GaAs samples were carried out by using an electron-cyclotron resonance-induced ammonia plasma. The formation of mixed phases of GaN was investigated using the grazing angle x-ray diffraction method. A remarkable improvement in the intensity of photoluminescence (PL) compared with that of GaN synthesized by direct nitriding of GaAs surface has been observed. The PL intensity of nitrided porous GaAs at the temperature of 380 deg. C was found to be about two orders of magnitude higher as compared with the directly nitrided GaAs at the temperature of 500 deg. C. The changes in the morphology of nitrided porous GaAs have been investigated using both scanning electron microscopy and atomic force microscopy

  3. Nitridation of porous GaAs by an ECR ammonia plasma

    Energy Technology Data Exchange (ETDEWEB)

    Naddaf, M [Center for Advanced Studies in Material Science and Solid State Physics, University of Pune, Pune 411 007 (India); Department of Physics, Atomic Energy Commission of Syria, PO Box 6091, Damascus (Syrian Arab Republic); Hullavarad, S S [Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742 (United States); Ganesan, V [Inter University Consortium, Indore (India); Bhoraskar, S V [Center for Advanced Studies in Material Science and Solid State Physics, University of Pune, Pune 411 007 (India)

    2006-02-15

    The effect of surface porosity of GaAs on the nature of growth of GaN, by use of plasma nitridation of GaAs, has been investigated. Porous GaAs samples were prepared by anodic etching of n-type (110) GaAs wafers in HCl solution. Nitridation of porous GaAs samples were carried out by using an electron-cyclotron resonance-induced ammonia plasma. The formation of mixed phases of GaN was investigated using the grazing angle x-ray diffraction method. A remarkable improvement in the intensity of photoluminescence (PL) compared with that of GaN synthesized by direct nitriding of GaAs surface has been observed. The PL intensity of nitrided porous GaAs at the temperature of 380 deg. C was found to be about two orders of magnitude higher as compared with the directly nitrided GaAs at the temperature of 500 deg. C. The changes in the morphology of nitrided porous GaAs have been investigated using both scanning electron microscopy and atomic force microscopy.

  4. Nitridation of porous GaAs by an ECR ammonia plasma

    Science.gov (United States)

    Naddaf, M.; Hullavarad, S. S.; Ganesan, V.; Bhoraskar, S. V.

    2006-02-01

    The effect of surface porosity of GaAs on the nature of growth of GaN, by use of plasma nitridation of GaAs, has been investigated. Porous GaAs samples were prepared by anodic etching of n-type (110) GaAs wafers in HCl solution. Nitridation of porous GaAs samples were carried out by using an electron-cyclotron resonance-induced ammonia plasma. The formation of mixed phases of GaN was investigated using the grazing angle x-ray diffraction method. A remarkable improvement in the intensity of photoluminescence (PL) compared with that of GaN synthesized by direct nitriding of GaAs surface has been observed. The PL intensity of nitrided porous GaAs at the temperature of 380 °C was found to be about two orders of magnitude higher as compared with the directly nitrided GaAs at the temperature of 500 °C. The changes in the morphology of nitrided porous GaAs have been investigated using both scanning electron microscopy and atomic force microscopy.

  5. Remarkable effects of disorder on superconductivity of single atomic layers of lead on silicon

    Science.gov (United States)

    Brun, Christophe

    2015-03-01

    It is well known that conventional superconductivity is very robust against non-magnetic disorder. Nevertheless for thin and ultrathin films the structural properties play a major role in determining the superconducting properties, through a subtle interplay between disorder and Coulomb interactions. Unexpectedly, in 2010 superconductivity was discovered in single atomic layers of lead and indium grown on silicon substrate using scanning tunneling spectroscopy and confirmed later on by macroscopic transport measurements. Such well-controlled and tunable crystalline monolayers are ideal systems for studying the influence of various kinds of structural defects on the superconducting properties at the atomic and mesoscopic scale. In particular, Pb monolayers offer the opportunity of probing new effects of disorder because not only superconductivity is 2D but also the electronic wave functions are 2D. Our study of two Pb monolayers of different crystal structures by very-low temperature STM (300 mK) under magnetic field reveals unexpected results involving new spatial spectroscopic variations. Our results show that although the sheet resistance of the Pb monolayers is much below the resistance quantum, strong non-BCS corrections appear leading to peak heights fluctuations in the dI/dV tunneling spectra at a spatial scale much smaller than the superconducting coherence length. Furthermore, strong local evidence of the signature of Rashba effect on the superconductivity of the Pb/Si(111) monolayer is revealed through filling of in gap states and local spatial variations of this filling. Finally the nature of vortices in a monolayer is found to be very sensitive to the properties of step edges areas. This work was supported by University Pierre et Marie Curie UPMC `Emergence' project, French ANR Project `ElectroVortex,' ANR-QuDec and Templeton Foundation (40381), ARO (W911NF-13-1-0431) and CNRS PICS funds. Partial funding by US-DOE Grant DE-AC02-07CH1.

  6. Atomic-Layer-Deposition of Indium Oxide Nano-films for Thin-Film Transistors.

    Science.gov (United States)

    Ma, Qian; Zheng, He-Mei; Shao, Yan; Zhu, Bao; Liu, Wen-Jun; Ding, Shi-Jin; Zhang, David Wei

    2018-01-09

    Atomic-layer-deposition (ALD) of In 2 O 3 nano-films has been investigated using cyclopentadienyl indium (InCp) and hydrogen peroxide (H 2 O 2 ) as precursors. The In 2 O 3 films can be deposited preferentially at relatively low temperatures of 160-200 °C, exhibiting a stable growth rate of 1.4-1.5 Å/cycle. The surface roughness of the deposited film increases gradually with deposition temperature, which is attributed to the enhanced crystallization of the film at a higher deposition temperature. As the deposition temperature increases from 150 to 200 °C, the optical band gap (E g ) of the deposited film rises from 3.42 to 3.75 eV. In addition, with the increase of deposition temperature, the atomic ratio of In to O in the as-deposited film gradually shifts towards that in the stoichiometric In 2 O 3 , and the carbon content also reduces by degrees. For 200 °C deposition temperature, the deposited film exhibits an In:O ratio of 1:1.36 and no carbon incorporation. Further, high-performance In 2 O 3 thin-film transistors with an Al 2 O 3 gate dielectric were achieved by post-annealing in air at 300 °C for appropriate time, demonstrating a field-effect mobility of 7.8 cm 2 /V⋅s, a subthreshold swing of 0.32 V/dec, and an on/off current ratio of 10 7 . This was ascribed to passivation of oxygen vacancies in the device channel.

  7. Electrode surface engineering by atomic layer deposition: A promising pathway toward better energy storage

    KAUST Repository

    Ahmed, Bilal

    2016-04-29

    Research on electrochemical energy storage devices including Li ion batteries (LIBs), Na ion batteries (NIBs) and supercapacitors (SCs) has accelerated in recent years, in part because developments in nanomaterials are making it possible to achieve high capacities and energy and power densities. These developments can extend battery life in portable devices, and open new markets such as electric vehicles and large-scale grid energy storage. It is well known that surface reactions largely determine the performance and stability of electrochemical energy storage devices. Despite showing impressive capacities and high energy and power densities, many of the new nanostructured electrode materials suffer from limited lifetime due to severe electrode interaction with electrolytes or due to large volume changes. Hence control of the surface of the electrode material is essential for both increasing capacity and improving cyclic stability of the energy storage devices.Atomic layer deposition (ALD) which has become a pervasive synthesis method in the microelectronics industry, has recently emerged as a promising process for electrochemical energy storage. ALD boasts excellent conformality, atomic scale thickness control, and uniformity over large areas. Since ALD is based on self-limiting surface reactions, complex shapes and nanostructures can be coated with excellent uniformity, and most processes can be done below 200. °C. In this article, we review recent studies on the use of ALD coatings to improve the performance of electrochemical energy storage devices, with particular emphasis on the studies that have provided mechanistic insight into the role of ALD in improving device performance. © 2016 Elsevier Ltd.

  8. Atomic layer deposition of cerium oxide for potential use in diesel soot combustion

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, Tatiana V., E-mail: tatiana.ivanova@lut.fi, E-mail: ivanova.tatyana.v@gmail.com; Toivonen, Jenni; Maydannik, Philipp S.; Kääriäinen, Tommi; Sillanpää, Mika [ASTRaL Team, Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Homola, Tomáš; Cameron, David C. [R& D Centre for Low-Cost Plasma and Nanotechnology Surface Modification, Masaryk University, Kotlářská 267/2, 611 37 Brno (Czech Republic)

    2016-05-15

    The particulate soot emission from diesel motors has a severe impact on the environment and people's health. The use of catalytic convertors is one of the ways to minimize the emission and decrease the hazard level. In this paper, the activity of cerium oxide for catalytic combustion of diesel soot was studied. Thin films of cerium dioxide were synthesized by atomic layer deposition using tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)cerium [Ce(thd){sub 4}] and ozone as precursors. The characteristics of the films were studied as a function of deposition conditions within the reaction temperature range of 180–350 °C. Thickness, crystallinity, elemental composition, and morphology of the CeO{sub 2} films deposited on Si (100) were characterized by ellipsometry, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy, respectively. The growth rate of CeO{sub 2} was observed to be 0.30 Å/cycle at temperatures up to 250 °C with a slight increase to 0.37 Å/cycle at 300 °C. The effect of CeO{sub 2} films grown on stainless steel foil supports on soot combustion was measured with annealing tests. Based on the analysis of these, in catalytic applications, CeO{sub 2} has been shown to be effective in lowering the soot combustion temperature from 600 °C for the uncoated substrates to 370 °C for the CeO{sub 2} coated ones. It was found that the higher deposition temperatures had a positive effect on the catalyst performance.

  9. Ultrafast triggered transient energy storage by atomic layer deposition into porous silicon for integrated transient electronics

    Science.gov (United States)

    Douglas, Anna; Muralidharan, Nitin; Carter, Rachel; Share, Keith; Pint, Cary L.

    2016-03-01

    Here we demonstrate the first on-chip silicon-integrated rechargeable transient power source based on atomic layer deposition (ALD) coating of vanadium oxide (VOx) into porous silicon. A stable specific capacitance above 20 F g-1 is achieved until the device is triggered with alkaline solutions. Due to the rational design of the active VOx coating enabled by ALD, transience occurs through a rapid disabling step that occurs within seconds, followed by full dissolution of all active materials within 30 minutes of the initial trigger. This work demonstrates how engineered materials for energy storage can provide a basis for next-generation transient systems and highlights porous silicon as a versatile scaffold to integrate transient energy storage into transient electronics.Here we demonstrate the first on-chip silicon-integrated rechargeable transient power source based on atomic layer deposition (ALD) coating of vanadium oxide (VOx) into porous silicon. A stable specific capacitance above 20 F g-1 is achieved until the device is triggered with alkaline solutions. Due to the rational design of the active VOx coating enabled by ALD, transience occurs through a rapid disabling step that occurs within seconds, followed by full dissolution of all active materials within 30 minutes of the initial trigger. This work demonstrates how engineered materials for energy storage can provide a basis for next-generation transient systems and highlights porous silicon as a versatile scaffold to integrate transient energy storage into transient electronics. Electronic supplementary information (ESI) available: (i) Experimental details for ALD and material fabrication, ellipsometry film thickness, preparation of gel electrolyte and separator, details for electrochemical measurements, HRTEM image of VOx coated porous silicon, Raman spectroscopy for VOx as-deposited as well as annealed in air for 1 hour at 450 °C, SEM and transient behavior dissolution tests of uniformly coated VOx on

  10. Local deposition of high-purity Pt nanostructures by combining electron beam induced deposition and atomic layer deposition

    NARCIS (Netherlands)

    Mackus, A.J.M.; Mulders, J.J.L.; Sanden, van de M.C.M.; Kessels, W.M.M.

    2010-01-01

    An approach for direct-write fabrication of high-purity platinum nanostructures has been developed by combining nanoscale lateral patterning by electron beam induced deposition (EBID) with area-selective deposition of high quality material by atomic layer deposition (ALD). Because virtually pure,

  11. Optimization studies of HgSe thin film deposition by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-06-01

    Full Text Available Studies of the optimization of HgSe thin film deposition using electrochemical atomic layer epitaxy (EC-ALE) are reported. Cyclic voltammetry was used to obtain approximate deposition potentials for each element. These potentials were then coupled...

  12. Piezophototronic Effect in Single-Atomic-Layer MoS 2 for Strain-Gated Flexible Optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Wenzhuo [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta GA 30332-0245 USA; Wang, Lei [Department of Electrical Engineering, Columbia University, New York NY 10027 USA; Yu, Ruomeng [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta GA 30332-0245 USA; Liu, Yuanyue [National Renewable Energy Laboratory (NREL), Golden CO 80401 USA; Wei, Su-Huai [National Renewable Energy Laboratory (NREL), Golden CO 80401 USA; Hone, James [Department of Mechanical Engineering, Columbia University, New York NY 10027 USA; Wang, Zhong Lin [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta GA 30332-0245 USA; Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, 100083 Beijing China

    2016-08-03

    Strain-gated flexible optoelectronics are reported based on monolayer MoS2. Utilizing the piezoelectric polarization created at metal-MoS2 interface to modulate the separation/transport of photogenerated carriers, the piezophototronic effect is applied to implement atomic-layer-thick phototransistor. Coupling between piezoelectricity and photogenerated carriers may enable the development of novel optoelectronics.

  13. High mobility In2O3:H transparent conductive oxides prepared by atomic layer deposition and solid phase crystallization

    NARCIS (Netherlands)

    Macco, B.; Wu, Y.; Vanhemel, D.; Kessels, W.M.M.

    2014-01-01

    The preparation of high-quality In2O3:H, as transparent conductive oxide (TCO), is demonstrated at low temperatures. Amorphous In2O3:H films were deposited by atomic layer deposition at 100 °C, after which they underwent solid phase crystallization by a short anneal at 200 °C. TEM analysis has shown

  14. Substrate-biasing during plasma-assisted atomic layer deposition to tailor metal-oxide thin film growth

    NARCIS (Netherlands)

    Profijt, H. B.; M. C. M. van de Sanden,; Kessele, W. M. M.

    2013-01-01

    Two substrate-biasing techniques, i.e., substrate-tuned biasing and RF biasing, have been implemented in a remote plasma configuration, enabling control of the ion energy during plasma-assisted atomic layer deposition (ALD). With both techniques, substrate bias voltages up to -200 V have been

  15. Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

    2016-01-01

    Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface fo...

  16. Epitaxial TiO 2/SnO 2 core-shell heterostructure by atomic layer deposition

    KAUST Repository

    Nie, Anmin; Liu, Jiabin; Li, Qianqian; Cheng, Yingchun; Dong, Cezhou; Zhou, Wu; Wang, Pengfei; Wang, Qingxiao; Yang, Yang; Zhu, Yihan; Zeng, Yuewu; Wang, Hongtao

    2012-01-01

    Taking TiO 2/SnO 2 core-shell nanowires (NWs) as a model system, we systematically investigate the structure and the morphological evolution of this heterostructure synthesized by atomic layer deposition/epitaxy (ALD/ALE). All characterizations

  17. Effective optimization of surface passivation on porous silicon carbide using atomic layer deposited Al2O3

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    2017-01-01

    Porous silicon carbide (B–N co-doped SiC) produced by anodic oxidation showed strong photoluminescence (PL) at around 520 nm excited by a 375 nm laser. The porous SiC samples were passivated by atomic layer deposited (ALD) aluminum oxide (Al2O3) films, resulting in a significant enhancement...

  18. Atomic-layer deposited Nb2O5 as transparent passivating electron contact for c-Si solar cells

    NARCIS (Netherlands)

    Macco, Bart; Black, Lachlan E.; Melskens, Jimmy; van de Loo, Bas W.H.; Berghuis, Willem Jan H.; Verheijen, Marcel A.; Kessels, Wilhelmus M.M.

    2018-01-01

    Passivating contacts based on metal oxides have proven to enable high energy conversion efficiencies for crystalline silicon (c-Si) solar cells at low processing complexity. In this work, the potential of atomic-layer deposited (ALD) Nb2O5 as novel electron-selective passivating contact is explored

  19. Atomic-Layer-Deposited SnO2 as Gate Electrode for Indium-Free Transparent Electronics

    KAUST Repository

    Alshammari, Fwzah Hamud; Hota, Mrinal Kanti; Wang, Zhenwei; Aljawhari, Hala; Alshareef, Husam N.

    2017-01-01

    Atomic-layer-deposited SnO2 is used as a gate electrode to replace indium tin oxide (ITO) in thin-film transistors and circuits for the first time. The SnO2 films deposited at 200 °C show low electrical resistivity of ≈3.1 × 10−3 Ω cm with ≈93

  20. Impacts of Thermal Atomic Layer-Deposited AlN Passivation Layer on GaN-on-Si High Electron Mobility Transistors.

    Science.gov (United States)

    Zhao, Sheng-Xun; Liu, Xiao-Yong; Zhang, Lin-Qing; Huang, Hong-Fan; Shi, Jin-Shan; Wang, Peng-Fei

    2016-12-01

    Thermal atomic layer deposition (ALD)-grown AlN passivation layer is applied on AlGaN/GaN-on-Si HEMT, and the impacts on drive current and leakage current are investigated. The thermal ALD-grown 30-nm amorphous AlN results in a suppressed off-state leakage; however, its drive current is unchanged. It was also observed by nano-beam diffraction method that thermal ALD-amorphous AlN layer barely enhanced the polarization. On the other hand, the plasma-enhanced chemical vapor deposition (PECVD)-deposited SiN layer enhanced the polarization and resulted in an improved drive current. The capacitance-voltage (C-V) measurement also indicates that thermal ALD passivation results in a better interface quality compared with the SiN passivation.

  1. Enhanced Performance of Nanowire-Based All-TiO2 Solar Cells using Subnanometer-Thick Atomic Layer Deposited ZnO Embedded Layer

    International Nuclear Information System (INIS)

    Ghobadi, Amir; Yavuz, Halil I.; Ulusoy, T. Gamze; Icli, K. Cagatay; Ozenbas, Macit; Okyay, Ali K.

    2015-01-01

    In this paper, the effect of angstrom-thick atomic layer deposited (ALD) ZnO embedded layer on photovoltaic (PV) performance of Nanowire-Based All-TiO 2 solar cells has been systematically investigated. Our results indicate that by varying the thickness of ZnO layer the efficiency of the solar cell can be significantly changed. It is shown that the efficiency has its maximum for optimal thickness of 1 ALD cycle in which this ultrathin ZnO layer improves device performance through passivation of surface traps without hampering injection efficiency of photogenerated electrons. The mechanisms contributing to this unprecedented change in PV performance of the cell have been scrutinized and discussed

  2. Evaluation of atomic layer deposited alumina as a protective layer for domestic silver articles: Anti-corrosion test in artificial sweat

    Science.gov (United States)

    Park, Suk Won; Han, Gwon Deok; Choi, Hyung Jong; Prinz, Fritz B.; Shim, Joon Hyung

    2018-05-01

    This study evaluated the effectiveness of alumina fabricated by atomic layer deposition (ALD) as a protective coating for silver articles against the corrosion caused by body contact. An artificial sweat solution was used to simulate body contact. ALD alumina layers of varying thicknesses ranging from 20 to 80 nm were deposited on sputtered silver samples. The stability of the protective layer was evaluated by immersing the coated samples in the artificial sweat solution at 25 and 35 °C for 24 h. We confirmed that a sufficiently thick layer of ALD alumina is effective in protecting the shape and light reflectance of the underlying silver, whereas the uncoated bare silver is severely degraded by the artificial sweat solution. Inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy were used for in-depth analyses of the chemical stability of the ALD-coated silver samples after immersion in the sweat solution.

  3. Atomic layer deposition on polymer fibers and fabrics for multifunctional and electronic textiles

    Energy Technology Data Exchange (ETDEWEB)

    Brozena, Alexandra H.; Oldham, Christopher J.; Parsons, Gregory N., E-mail: gnp@ncsu.edu [Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)

    2016-01-15

    Textile materials, including woven cotton, polymer knit fabrics, and synthetic nonwoven fiber mats, are being explored as low-cost, flexible, and light-weight platforms for wearable electronic sensing, communication, energy generation, and storage. The natural porosity and high surface area in textiles is also useful for new applications in environmental protection, chemical decontamination, pharmaceutical and chemical manufacturing, catalytic support, tissue regeneration, and others. These applications raise opportunities for new chemistries, chemical processes, biological coupling, and nanodevice systems that can readily combine with textile manufacturing to create new “multifunctional” fabrics. Atomic layer deposition (ALD) has a unique ability to form highly uniform and conformal thin films at low processing temperature on nonuniform high aspect ratio surfaces. Recent research shows how ALD can coat, modify, and otherwise improve polymer fibers and textiles by incorporating new materials for viable electronic and other multifunctional capabilities. This article provides a current overview of the understanding of ALD coating and modification of textiles, including current capabilities and outstanding problems, with the goal of providing a starting point for further research and advances in this field. After a brief introduction to textile materials and current textile treatment methods, the authors discuss unique properties of ALD-coated textiles, followed by a review of recent electronic and multifunctional textiles that use ALD coatings either as direct functional components or as critical nucleation layers for active materials integration. The article concludes with possible future directions for ALD on textiles, including the challenges in materials, manufacturing, and manufacturing integration that must be overcome for ALD to reach its full potential in electronic and other emerging multifunctional textile systems.

  4. Effective coating of titania nanoparticles with alumina via atomic layer deposition

    Science.gov (United States)

    Azizpour, H.; Talebi, M.; Tichelaar, F. D.; Sotudeh-Gharebagh, R.; Guo, J.; van Ommen, J. R.; Mostoufi, N.

    2017-12-01

    Alumina films were deposited on titania nanoparticles via atomic layer deposition (ALD) in a fluidized bed reactor at 180 °C and 1 bar. Online mass spectrometry was used for real time monitoring of effluent gases from the reactor during each reaction cycle in order to determine the optimal dosing time of precursors. Different oxygen sources were used to see which oxygen source, in combination with trimethyl aluminium (TMA), provides the highest alumina growth per cycle (GPC). Experiments were carried out in 4, 7 and 10 cycles using the optimal dosing time of precursors. Several characterization methods, such as high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and instrumental neutron activation analysis (INAA), were conducted on the products. Formation of the alumina film was confirmed by EDX mapping and EDX line profiling, FTIR and TEM. When using either water or deuterium oxide as the oxygen source, the thickness of the alumina film was greater than that of ozone. The average GPC measured by TEM for the ALD of TMA with water, deuterium oxide and ozone was about 0.16 nm, 0.15 nm and 0.11 nm, respectively. The average GPC calculated using the mass fraction of aluminum from INAA was close to those measured from TEM images. Excess amounts of precursors lead to a higher average growth of alumina film per cycle due to insufficient purging time. XRD analysis demonstrated that amorphous alumina was coated on titania nanoparticles. This amorphous layer was easily distinguished from the crystalline core in the TEM images. Decrease in the photocatalytic activity of titania nanoparticles after alumina coating was confirmed by measuring degradation of Rhodamine B by ultraviolet irradiation.

  5. Plasma enhanced atomic layer batch processing of aluminum doped titanium dioxide

    International Nuclear Information System (INIS)

    Lehnert, Wolfgang; Ruhl, Guenther; Gschwandtner, Alexander

    2012-01-01

    Among many promising high-k dielectrics, TiO 2 is an interesting candidate because of its relatively high k value of over 40 and its easy integration into existing semiconductor manufacturing schemes. The most critical issues of TiO 2 are its low electrical stability and its high leakage current density. However, doping TiO 2 with Al has shown to yield significant improvement of layer quality on Ru electrodes [S. K. Kim et al., Adv. Mater. 20, 1429 (2008)]. In this work we investigated if atomic layer deposition (ALD) of Al doped TiO 2 is feasible in a batch system. Electrical characterizations were done using common electrode materials like TiN, TaN, or W. Additionally, the effect of plasma enhanced processing in this reactor was studied. For this investigation a production batch ALD furnace has been retrofitted with a plasma source which can be used for post deposition anneals with oxygen radicals as well as for directly plasma enhanced ALD. After evaluation of several Ti precursors a deposition process for AlTiO x with excellent film thickness and composition uniformity was developed. The effects of post deposition anneals, Al 2 O 3 interlayers between electrode and TiO 2 , Al doping concentration, plasma enhanced deposition and electrode material type on leakage current density are shown. An optimized AlTiO x deposition process on TaN electrodes yields to leakage current density of 5 x 10 -7 A/cm 2 at 2 V and k values of about 35. Thus, it could be demonstrated that a plasma enhanced batch ALD process for Al doped TiO 2 is feasible with acceptable leakage current density on a standard electrode material.

  6. Atomistic kinetic Monte Carlo study of atomic layer deposition derived from density functional theory.

    Science.gov (United States)

    Shirazi, Mahdi; Elliott, Simon D

    2014-01-30

    To describe the atomic layer deposition (ALD) reactions of HfO2 from Hf(N(CH3)2)4 and H2O, a three-dimensional on-lattice kinetic Monte-Carlo model is developed. In this model, all atomistic reaction pathways in density functional theory (DFT) are implemented as reaction events on the lattice. This contains all steps, from the early stage of adsorption of each ALD precursor, kinetics of the surface protons, interaction between the remaining precursors (steric effect), influence of remaining fragments on adsorption sites (blocking), densification of each ALD precursor, migration of each ALD precursors, and cooperation between the remaining precursors to adsorb H2O (cooperative effect). The essential chemistry of the ALD reactions depends on the local environment at the surface. The coordination number and a neighbor list are used to implement the dependencies. The validity and necessity of the proposed reaction pathways are statistically established at the mesoscale. The formation of one monolayer of precursor fragments is shown at the end of the metal pulse. Adsorption and dissociation of the H2O precursor onto that layer is described, leading to the delivery of oxygen and protons to the surface during the H2O pulse. Through these processes, the remaining precursor fragments desorb from the surface, leaving the surface with bulk-like and OH-terminated HfO2, ready for the next cycle. The migration of the low coordinated remaining precursor fragments is also proposed. This process introduces a slow reordering motion (crawling) at the mesoscale, leading to the smooth and conformal thin film that is characteristic of ALD. Copyright © 2013 Wiley Periodicals, Inc.

  7. Selenium passivation of GaAs(001): a combined experimental and theoretical study

    International Nuclear Information System (INIS)

    Gonzalez, C; Benito, I; Ortega, J; Jurczyszyn, L; Blanco, J M; Perez, R; Flores, F; Kampen, T U; Zahn, D R T; Braun, W

    2004-01-01

    The chemical and electronic properties of selenium passivated GaAs(001)-2 x 1 surfaces were investigated by a combination of theoretical calculations and core level photoemission experiments. An anion exchange results in gallium-selenide like layers showing a 2 x 1 reconstruction in low energy electron diffraction (LEED). The analysis of the different components in the core level spectra of As 3d, Ga 3d and Se 3d limits the number of possible structural models. The Se/GaAs(001)-2 x 1 reconstruction has been also analysed by means of DFT-LDA calculations and theoretical STM currents. In a first step, different geometries are considered and the most stable one, from the point of view of the thermodynamic potential, is determined. Then, STM currents and the corresponding surface corrugation are calculated and compared with the experimental evidence. We conclude that the Se/GaAs(001)-2 x 1 reconstruction has a single Se atom in the last crystal layer, bonded to two Ga atoms of the second layer, and another Se layer replacing the third As layer of the crystal. These surfaces may be considered as chemically stable because they withstand considerable exposure to air. In terms of electronic passivation, i.e. the removal of any surface band bending, the selenium modification is not successful. Band bending on n-type doped samples is reduced while band bending on the p-type doped samples is further increased

  8. Growth mechanisms for Si epitaxy on O atomic layers: Impact of O-content and surface structure

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Billen, Arne [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Moussa, Alain; Caymax, Matty; Bender, Hugo [Imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Heyns, Marc [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Delabie, Annelies [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium)

    2016-10-30

    Highlights: • O{sub 3} or O{sub 2} exposures on H-Si(100) result in O ALs with different surface structures. • Si-EPI on O AL using O{sub 3} process is by direct epitaxial growth mechanism. • Si-EPI on O AL using O{sub 2} process is by epitaxial lateral overgrowth mechanism. • Distortions by O AL, SiH{sub 4} flux rate and Si thickness has an impact on Si-EPI quality. - Abstract: The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O{sub 3}) or oxygen (O{sub 2}) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH{sub 4}) at 500 °C. After O{sub 3} exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH{sub 4} reactants, allowing more time for surface diffusion. After O{sub 2} exposure, the O atoms are present in the form of SiO{sub x} clusters. Regions of hydrogen-terminated Si remain present between the SiO{sub x} clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

  9. Plasma-assisted atomic layer deposition of TiO2 compact layers for flexible mesostructured perovskite solar cells

    NARCIS (Netherlands)

    Zardetto, V.; Di Giacomo, F.; Lucarelli, G.; Kessels, W.M.M.; Brown, T.M.; Creatore, M.

    2017-01-01

    In mesostructured perovskite solar cell devices, charge recombination processes at the interface between the transparent conductive oxide, perovskite and hole transport layer are suppressed by depositing an efficient compact TiO2 blocking layer. In this contribution we investigate the role of the

  10. Texture variations and atomic dislocations by Ar-irradiation in Au and NbN sputtered layers

    International Nuclear Information System (INIS)

    Jung, V.

    1988-02-01

    Irradiation of Au and NbN sputtered layers with Ar ++ ions of 600 keV leads to a narrower orientation distribution of the [111] direction of the Au layers from 12 0 FWHM to 6 0 and to only very small FWHM changes in texture distributions of the NbN layers. But the FWHM of the reflex distribution of the irradiated NbN layers is increased significantly from ΔΘ = 0.65 0 to 1.17 0 for one sample position. This is caused by small atomic dislocations in the NbN lattice. The FWHM of reflex distribution of the Au layers increased only from ΔΘ = 0.60 0 to 0.65 0 after irradiation. Oblique incidence of Ar ++ ions causes, by absence of channeling, stronger distortions than perpendicular incidence. (orig.) [de

  11. Atomic layer deposition of Pd and Pt nanoparticles for catalysis: on the mechanisms of nanoparticle formation

    International Nuclear Information System (INIS)

    Mackus, Adriaan J M; Weber, Matthieu J; Thissen, Nick F W; Garcia-Alonso, Diana; Vervuurt, René H J; Assali, Simone; Bol, Ageeth A; Verheijen, Marcel A; Kessels, Wilhelmus M M

    2016-01-01

    The deposition of Pd and Pt nanoparticles by atomic layer deposition (ALD) has been studied extensively in recent years for the synthesis of nanoparticles for catalysis. For these applications, it is essential to synthesize nanoparticles with well-defined sizes and a high density on large-surface-area supports. Although the potential of ALD for synthesizing active nanocatalysts for various chemical reactions has been demonstrated, insight into how to control the nanoparticle properties (i.e. size, composition) by choosing suitable processing conditions is lacking. Furthermore, there is little understanding of the reaction mechanisms during the nucleation stage of metal ALD. In this work, nanoparticles synthesized with four different ALD processes (two for Pd and two for Pt) were extensively studied by transmission electron spectroscopy. Using these datasets as a starting point, the growth characteristics and reaction mechanisms of Pd and Pt ALD relevant for the synthesis of nanoparticles are discussed. The results reveal that ALD allows for the preparation of particles with control of the particle size, although it is also shown that the particle size distribution is strongly dependent on the processing conditions. Moreover, this paper discusses the opportunities and limitations of the use of ALD in the synthesis of nanocatalysts. (paper)

  12. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G., E-mail: ekerdt@utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-12-15

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al{sub 2}O{sub 3} and HfO{sub 2}. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO{sub 3}), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  13. Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Zhou Kai

    2010-01-01

    Full Text Available Abstract The structure of vertically aligned carbon nanotubes (CNTs severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD was employed to deposit uniform Fe2O3 film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe2O3 catalyst films with different thicknesses were obtained on Si/SiO2 substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.

  14. Atomic layer deposition of HfO{sub 2} on graphene through controlled ion beam treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki Seok [School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419 (Korea, Republic of); Oh, Il-Kwon; Jung, Hanearl; Kim, Hyungjun [School of Electrical and Electronics Engineering, Yonsei University, 50 Yonsei Ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Yeom, Geun Young, E-mail: knam1004@dju.kr, E-mail: gyyeom@skku.edu [School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419 (Korea, Republic of); SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419 (Korea, Republic of); Kim, Kyong Nam, E-mail: knam1004@dju.kr, E-mail: gyyeom@skku.edu [School of Advanced Materials Science and Engineering, Daejeon University, Yongun-dong, Dong-gu, Daejeon 34520 (Korea, Republic of)

    2016-05-23

    The polymer residue generated during the graphene transfer process to the substrate tends to cause problems (e.g., a decrease in electron mobility, unwanted doping, and non-uniform deposition of the dielectric material). In this study, by using a controllable low-energy Ar{sup +} ion beam, we cleaned the polymer residue without damaging the graphene network. HfO{sub 2} grown by atomic layer deposition on graphene cleaned using an Ar{sup +} ion beam showed a dense uniform structure, whereas that grown on the transferred graphene (before Ar{sup +} ion cleaning) showed a non-uniform structure. A graphene–HfO{sub 2}–metal capacitor fabricated by growing 20-nm thick HfO{sub 2} on graphene exhibited a very low leakage current (<10{sup −11} A/cm{sup 2}) for Ar{sup +} ion-cleaned graphene, whereas a similar capacitor grown using the transferred graphene showed high leakage current.

  15. Atomic layer deposition-A novel method for the ultrathin coating of minitablets.

    Science.gov (United States)

    Hautala, Jaana; Kääriäinen, Tommi; Hoppu, Pekka; Kemell, Marianna; Heinämäki, Jyrki; Cameron, David; George, Steven; Juppo, Anne Mari

    2017-10-05

    We introduce atomic layer deposition (ALD) as a novel method for the ultrathin coating (nanolayering) of minitablets. The effects of ALD coating on the tablet characteristics and taste masking were investigated and compared with the established coating method. Minitablets containing bitter tasting denatonium benzoate were coated by ALD using three different TiO 2 nanolayer thicknesses (number of deposition cycles). The established coating of minitablets was performed in a laboratory-scale fluidized-bed apparatus using four concentration levels of aqueous Eudragit ® E coating polymer. The coated minitablets were studied with respect to the surface morphology, taste masking capacity, in vitro disintegration and dissolution, mechanical properties, and uniformity of content. The ALD thin coating resulted in minimal increase in the dimensions and weight of minitablets in comparison to original tablet cores. Surprisingly, ALD coating with TiO 2 nanolayers decreased the mechanical strength, and accelerated the in vitro disintegration of minitablets. Unlike previous studies, the studied levels of TiO 2 nanolayers on tablets were also inadequate for effective taste masking. In summary, ALD permits a simple and rapid method for the ultrathin coating (nanolayering) of minitablets, and provides nanoscale-range TiO 2 coatings on porous minitablets. More research, however, is needed to clarify its potential in tablet taste masking applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Conformity and structure of titanium oxide films grown by atomic layer deposition on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jogi, Indrek [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia)], E-mail: indrek.jogi@ut.ee; Paers, Martti; Aarik, Jaan; Aidla, Aleks [University of Tartu, Institute of Physics, Riia 142, 51014, Tartu (Estonia); Laan, Matti [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia); Sundqvist, Jonas; Oberbeck, Lars; Heitmann, Johannes [Qimonda Dresden GmbH and Co. OHG, Koenigsbruecker Strasse 180, 01099, Dresden (Germany); Kukli, Kaupo [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia)

    2008-06-02

    Conformity and phase structure of atomic layer deposited TiO{sub 2} thin films grown on silicon substrates were studied. The films were grown using TiCl{sub 4} and Ti(OC{sub 2}H{sub 5}){sub 4} as titanium precursors in the temperature range from 125 to 500 {sup o}C. In all cases perfect conformal growth was achieved on patterned substrates with elliptical holes of 7.5 {mu}m depth and aspect ratio of about 1:40. Conformal growth was achieved with process parameters similar to those optimized for the growth on planar wafers. The dominant crystalline phase in the as-grown films was anatase, with some contribution from rutile at relatively higher temperatures. Annealing in the oxygen ambient resulted in (re)crystallization whereas the effect of annealing depended markedly on the precursors used in the deposition process. Compared to films grown from TiCl{sub 4}, the films grown from Ti(OC{sub 2}H{sub 5}){sub 4} were transformed into rutile in somewhat greater extent, whereas in terms of step coverage the films grown from Ti(OC{sub 2}H{sub 5}){sub 4} remained somewhat inferior compared to the films grown from TiCl{sub 4}.

  17. Catalyst synthesis and evaluation using an integrated atomic layer deposition synthesis–catalysis testing tool

    International Nuclear Information System (INIS)

    Camacho-Bunquin, Jeffrey; Shou, Heng; Marshall, Christopher L.; Aich, Payoli; Beaulieu, David R.; Klotzsch, Helmut; Bachman, Stephen; Hock, Adam; Stair, Peter

    2015-01-01

    An integrated atomic layer deposition synthesis-catalysis (I-ALD-CAT) tool was developed. It combines an ALD manifold in-line with a plug-flow reactor system for the synthesis of supported catalytic materials by ALD and immediate evaluation of catalyst reactivity using gas-phase probe reactions. The I-ALD-CAT delivery system consists of 12 different metal ALD precursor channels, 4 oxidizing or reducing agents, and 4 catalytic reaction feeds to either of the two plug-flow reactors. The system can employ reactor pressures and temperatures in the range of 10 −3 to 1 bar and 300–1000 K, respectively. The instrument is also equipped with a gas chromatograph and a mass spectrometer unit for the detection and quantification of volatile species from ALD and catalytic reactions. In this report, we demonstrate the use of the I-ALD-CAT tool for the synthesis of platinum active sites and Al 2 O 3 overcoats, and evaluation of catalyst propylene hydrogenation activity

  18. All-gas-phase synthesis of UiO-66 through modulated atomic layer deposition

    Science.gov (United States)

    Lausund, Kristian Blindheim; Nilsen, Ola

    2016-11-01

    Thin films of stable metal-organic frameworks (MOFs) such as UiO-66 have enormous application potential, for instance in microelectronics. However, all-gas-phase deposition techniques are currently not available for such MOFs. We here report on thin-film deposition of the thermally and chemically stable UiO-66 in an all-gas-phase process by the aid of atomic layer deposition (ALD). Sequential reactions of ZrCl4 and 1,4-benzenedicarboxylic acid produce amorphous organic-inorganic hybrid films that are subsequently crystallized to the UiO-66 structure by treatment in acetic acid vapour. We also introduce a new approach to control the stoichiometry between metal clusters and organic linkers by modulation of the ALD growth with additional acetic acid pulses. An all-gas-phase synthesis technique for UiO-66 could enable implementations in microelectronics that are not compatible with solvothermal synthesis. Since this technique is ALD-based, it could also give enhanced thickness control and the possibility to coat irregular substrates with high aspect ratios.

  19. Standing and sitting adlayers in atomic layer deposition of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhengning; Banerjee, Parag, E-mail: parag.banerjee@wustl.edu [Department of Mechanical Engineering & Material Science, Washington University in St. Louis, Missouri 63130 and Institute of Materials Science & Engineering, Washington University in St. Louis, Missouri 63130 (United States); Wu, Fei; Myung, Yoon [Department of Mechanical Engineering & Material Science, Washington University in St. Louis, Missouri 63130 (United States); Fei, Ruixiang [Department of Physics, Washington University in St. Louis, Missouri 63130 (United States); Kanjolia, Ravindra [SAFC Hitech, 1429 Hilldale Ave., Haverhill, Massachusetts 01832 (United States); Yang, Li [Institute of Materials Science & Engineering, Washington University in St. Louis, Missouri 63130 and Department of Physics, Washington University in St. Louis, Missouri 63130 (United States)

    2016-01-15

    The extent of reactivity of diethyl zinc (DEZ) with a hydroxylated surface during atomic layer deposition (ALD) of ZnO using DEZ and water is measured. Two adlayer configurations of DEZ are possible. The “standing” adlayer releases one ethyl group from DEZ. The “sitting” adlayer releases both ethyl groups, thus forming a Zn bridge between two O anions. Density functional theory calculations suggest the sitting configuration is more stable than the standing configuration by 790 meV. In situ quadrupole mass spectroscopy of by-product ethane generated in ALD half cycles indicate that ∼1.56 OH sites react with a DEZ molecule resulting in 71.6% of sitting sites. A simple simulation of a “ball-and-stick” DEZ molecule randomly collapsing on a neighboring site remarkably captures this adlayer behavior. It is concluded that DEZ fraction sitting is a competitive process of a standing DEZ molecule collapsing onto an available neighboring hydroxyl site, as sites vie for occupancy via adsorption and surface diffusion.

  20. Aligned carbon nanotube array functionalization for enhanced atomic layer deposition of platinum electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Dameron, Arrelaine A., E-mail: arrelaine.dameron@nrel.gov [National Renewable Energy Laboratory, 1617 Cole Blvd Golden, Golden, CO 80401 (United States); Pylypenko, Svitlana; Bult, Justin B.; Neyerlin, K.C.; Engtrakul, Chaiwat; Bochert, Christopher; Leong, G. Jeremy; Frisco, Sarah L.; Simpson, Lin; Dinh, Huyen N.; Pivovar, Bryan [National Renewable Energy Laboratory, 1617 Cole Blvd Golden, Golden, CO 80401 (United States)

    2012-04-15

    Uniform metal deposition onto high surface area supports is a key challenge of developing successful efficient catalyst materials. Atomic layer deposition (ALD) circumvents permeation difficulties, but relies on gas-surface reactions to initiate growth. Our work demonstrates that modified surfaces within vertically aligned carbon nanotube (CNT) arrays, from plasma and molecular precursor treatments, can lead to improved catalyst deposition. Gas phase functionalization influences the number of ALD nucleation sites and the onset of ALD growth and, in turn, affects the uniformity of the coating along the length of the CNTs within the aligned arrays. The induced chemical changes for each functionalization route are identified by X-ray photoelectron and Raman spectroscopies. The most effective functionalization routes increase the prevalence of oxygen moieties at defect sites on the carbon surfaces. The striking effects of the functionalization are demonstrated with ALD Pt growth as a function of surface treatment and ALD cycles examined by electron microscopy of the arrays and the individual CNTs. Finally, we demonstrate applicability of these materials as fuel cell electrocatalysts and show that surface functionalization affects their performance towards oxygen reduction reaction.

  1. Conformal atomic layer deposition of alumina on millimeter tall, vertically-aligned carbon nanotube arrays.

    Science.gov (United States)

    Stano, Kelly L; Carroll, Murphy; Padbury, Richard; McCord, Marian; Jur, Jesse S; Bradford, Philip D

    2014-11-12

    Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.

  2. Characterization of ZnO film grown on polycarbonate by atomic layer deposition at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gyeong Beom; Han, Gwon Deok; Shim, Joon Hyung; Choi, Byoung-Ho, E-mail: bhchoi@korea.ac.kr [School of Mechanical Engineering, Korea University, Seoul 136-707 (Korea, Republic of)

    2015-01-15

    ZnO is an attractive material for use in various technological products such as phosphors, gas sensors, and transparent conductors. Recently, aluminum-doped zinc oxide has received attention as a potential replacement for indium tin oxide, which is one of the transparent conductive oxides used in flat panel displays, organic light-emitting diodes, and organic solar cells. In this study, the characteristics of ZnO films deposited on polycarbonate (PC) substrates by atomic layer deposition (ALD) are investigated for various process temperatures. The growth mechanism of these films was investigated at low process temperatures using x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). XRD and XPS were used to determine the preferred orientation and chemical composition of the films, respectively. Furthermore, the difference of the deposition mechanisms on an amorphous organic material, i.e., PC substrate and an inorganic material such as silicon was discussed from the viewpoint of the diffusion and deposition of precursors. The structure of the films was also investigated by chemical analysis in order to determine the effect of growth temperature on the films deposited by ALD.

  3. Ultraviolet optical properties of aluminum fluoride thin films deposited by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hennessy, John, E-mail: john.j.hennessy@jpl.nasa.gov; Jewell, April D.; Balasubramanian, Kunjithapatham; Nikzad, Shouleh [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

    2016-01-15

    Aluminum fluoride (AlF{sub 3}) is a low refractive index material with promising optical applications for ultraviolet (UV) wavelengths. An atomic layer deposition process using trimethylaluminum and anhydrous hydrogen fluoride has been developed for the deposition of AlF{sub 3} at substrate temperatures between 100 and 200 °C. This low temperature process has resulted in thin films with UV-optical properties that have been characterized by ellipsometric and reflection/transmission measurements at wavelengths down to 200 nm. The optical loss for 93 nm thick films deposited at 100 °C was measured to be less than 0.2% from visible wavelengths down to 200 nm, and additional microstructural characterization demonstrates that the films are amorphous with moderate tensile stress of 42–105 MPa as deposited on silicon substrates. X-ray photoelectron spectroscopy analysis shows no signature of residual aluminum oxide components making these films good candidates for a variety of applications at even shorter UV wavelengths.

  4. NiO/nanoporous graphene composites with excellent supercapacitive performance produced by atomic layer deposition

    International Nuclear Information System (INIS)

    Chen, Caiying; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Qin, Yong; Huang, Peipei; Li, Ping; Fan, Jinchuan; Song, Weiguo

    2014-01-01

    Nickel oxide (NiO) is a promising electrode material for supercapacitors because of its low cost and high theoretical specific capacitance of 2573 F g −1 . However, the low electronic conductivity and poor cycling stability of NiO limit its practical applications. To overcome these limitations, an efficient atomic layer deposition (ALD) method is demonstrated here for the fabrication of NiO/nanoporous graphene (NG) composites as electrode materials for supercapacitors. ALD allows uniform deposition of NiO nanoparticles with controlled sizes on the surface of NG, thus offering a novel route to design NiO/NG composites for supercapacitor applications with high surface areas and greatly improved electrical conductivity and cycle stability. Electrochemical measurements reveal that the NiO/NG composites obtained by ALD exhibited excellent specific capacitance of up to ∼1005.8 F g −1 per mass of the composite electrode (the specific capacitance value is up to ∼1897.1 F g −1 based on the active mass of NiO), and stable performance after 1500 cycles. Furthermore, electrochemical performance of the NiO/NG composites is found to strongly depend on the size of NiO nanoparticles. (paper)

  5. Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Broas, Mikael, E-mail: mikael.broas@aalto.fi; Vuorinen, Vesa [Department of Electrical Engineering and Automation, Aalto University, P.O. Box 13500, FIN-00076 Aalto, Espoo (Finland); Sippola, Perttu; Pyymaki Perros, Alexander; Lipsanen, Harri [Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FIN-00076 Aalto, Espoo (Finland); Sajavaara, Timo [Department of Physics, University of Jyväskylä, P.O. Box 35, FIN-40014 Jyväskylä (Finland); Paulasto-Kröckel, Mervi [Department of Electrical Engineering and Automation, Aalto University. P.O. Box 13500, FIN-00076 Aalto, Espoo (Finland)

    2016-07-15

    Plasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N{sub 2}:H{sub 2} plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the AlN films. Furthermore, dinitrogen triple bonds were identified with infrared spectroscopy in the films. The triple bonds broke after annealing at 1000 °C for 1 h which likely caused enhanced hydrolysis of the films. The nanostructure of the films was identified to be amorphous in the as-deposited state and to become nanocrystalline after 1 h of annealing at 1000 °C.

  6. Novel Antimicrobial Titanium Dioxide Nanotubes Obtained through a Combination of Atomic Layer Deposition and Electrospinning Technologies

    Science.gov (United States)

    Patiño, Cristian; Galotto, María Jose; Palma, Juan Luis; Alburquenque, Daniela

    2018-01-01

    The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 μg/mL concentration. PMID:29495318

  7. Atomic Layer Etching of Silicon to Solve ARDE-Selectivity-Profile-Uniformity Trade-Offs

    Science.gov (United States)

    Wang, Mingmei; Ranjan, Alok; Ventzek, Peter; Koshiishi, Akira

    2014-10-01

    With shrinking critical dimensions, dry etch faces more and more challenges. Minimizing each of aspect ratio dependent etching (ARDE), bowing, undercut, selectivity, and within die uniformly across a wafer are met by trading off one requirement against another. At the root of the problem is that roles radical flux, ion flux and ion energy play may be both good and bad. Increasing one parameter helps meeting one requirement but hinders meeting the other. Self-limiting processes like atomic layer etching (ALE) promise a way to escape the problem of balancing trade-offs. ALE was realized in the mid-1990s but the industrial implementation has been slow. In recent years interest in ALE has revived. We present how ARDE, bowing/selectivity trade-offs may be overcome by varying radical/ion ratio, byproduct re-deposition. We overcome many of the practical implementation issues associated with ALE by precise passivation process control. The Monte Carlo Feature Profile Model (MCFPM) is used to illustrate realistic scenarios built around an Ar/Cl2 chemistry driven etch of Si masked by SiO2. We demonstrate that ALE can achieve zero ARDE and infinite selectivity. Profile control depends on careful management of the ion energies and angles. For ALE to be realized in production environment, tight control of IAD is a necessary. Experimental results are compared with simulation results to provide context to the work.

  8. Low-Temperature Crystalline Titanium Dioxide by Atomic Layer Deposition for Dye-Sensitized Solar Cells

    KAUST Repository

    Chandiran, Aravind Kumar

    2013-04-24

    Low-temperature processing of dye-sensitized solar cells (DSCs) is crucial to enable commercialization with low-cost, plastic substrates. Prior studies have focused on mechanical compression of premade particles on plastic or glass substrates; however, this did not yield sufficient interconnections for good carrier transport. Furthermore, such compression can lead to more heterogeneous porosity. To circumvent these problems, we have developed a low-temperature processing route for photoanodes where crystalline TiO2 is deposited onto well-defined, mesoporous templates. The TiO2 is grown by atomic layer deposition (ALD), and the crystalline films are achieved at a growth temperature of 200 C. The ALD TiO2 thickness was systematically studied in terms of charge transport and performance to lead to optimized photovoltaic performance. We found that a 15 nm TiO2 overlayer on an 8 μm thick SiO2 film leads to a high power conversion efficiency of 7.1% with the state-of-the-art zinc porphyrin sensitizer and cobalt bipyridine redox mediator. © 2013 American Chemical Society.

  9. Effect of atomic layer deposition coatings on the surface structure of anodic aluminum oxide membranes.

    Science.gov (United States)

    Xiong, Guang; Elam, Jeffrey W; Feng, Hao; Han, Catherine Y; Wang, Hsien-Hau; Iton, Lennox E; Curtiss, Larry A; Pellin, Michael J; Kung, Mayfair; Kung, Harold; Stair, Peter C

    2005-07-28

    Anodic aluminum oxide (AAO) membranes were characterized by UV Raman and FT-IR spectroscopies before and after coating the entire surface (including the interior pore walls) of the AAO membranes by atomic layer deposition (ALD). UV Raman reveals the presence of aluminum oxalate in bulk AAO, both before and after ALD coating with Al2O3, because of acid anion incorporation during the anodization process used to produce AAO membranes. The aluminum oxalate in AAO exhibits remarkable thermal stability, not totally decomposing in air until exposed to a temperature >900 degrees C. ALD was used to cover the surface of AAO with either Al2O3 or TiO2. Uncoated AAO have FT-IR spectra with two separate types of OH stretches that can be assigned to isolated OH groups and hydrogen-bonded surface OH groups, respectively. In contrast, AAO surfaces coated by ALD with Al2O3 display a single, broad band of hydrogen-bonded OH groups. AAO substrates coated with TiO2 show a more complicated behavior. UV Raman results show that very thin TiO2 coatings (1 nm) are not stable upon annealing to 500 degrees C. In contrast, thicker coatings can totally cover the contaminated alumina surface and are stable at temperatures in excess of 500 degrees C.

  10. Direct Measurements of Half-Cycle Reaction Heats during Atomic Layer Deposition by Calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Lownsbury, James M. [Department; Gladden, James A. [Department; Campbell, Charles T. [Department; Department; Kim, In Soo [Materials; Martinson, Alex B. F. [Materials

    2017-10-05

    We introduce a new high-temperature adsorption calorimeter that approaches the ideal limit of a heat detector whereby the signal at any time is proportional to the heat power being delivered to the sample and prove its sensitivity for measuring pulse-to-pulse heats of half-reactions during atomic layer deposition (ALD) at 400 K. The heat dynamics of amorphous Al2O3 growth via sequential self-limiting surface reaction of trimethylaluminum (TMA) and H2O is clearly resolved. Calibration enables quantitation of the exothermic TMA and H2O half-reactions with high precision, -343 kJ/mol TMA and -251 kJ/mol H2O, respectively. A time resolution better than 1 ms is demonstrated, allowing for the deconvolution of at least two distinct surface reactions during TMA microdosing. It is further demonstrated that this method can provide the heat of reaction versus extent of reaction during each precursors half-reaction, thus providing even richer mechanistic information on the surface processes involved. The broad applicability of this novel calorimeter is demonstrated through excellent signal-to-noise ratios of less exothermic ALD half-reactions to produce TiO2 and MnO.

  11. Catalyst synthesis and evaluation using an integrated atomic layer deposition synthesis–catalysis testing tool

    Energy Technology Data Exchange (ETDEWEB)

    Camacho-Bunquin, Jeffrey; Shou, Heng; Marshall, Christopher L. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Aich, Payoli [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Beaulieu, David R.; Klotzsch, Helmut; Bachman, Stephen [Arradiance Inc., Sudbury, Massachusetts 01776 (United States); Hock, Adam [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Stair, Peter [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-08-15

    An integrated atomic layer deposition synthesis-catalysis (I-ALD-CAT) tool was developed. It combines an ALD manifold in-line with a plug-flow reactor system for the synthesis of supported catalytic materials by ALD and immediate evaluation of catalyst reactivity using gas-phase probe reactions. The I-ALD-CAT delivery system consists of 12 different metal ALD precursor channels, 4 oxidizing or reducing agents, and 4 catalytic reaction feeds to either of the two plug-flow reactors. The system can employ reactor pressures and temperatures in the range of 10{sup −3} to 1 bar and 300–1000 K, respectively. The instrument is also equipped with a gas chromatograph and a mass spectrometer unit for the detection and quantification of volatile species from ALD and catalytic reactions. In this report, we demonstrate the use of the I-ALD-CAT tool for the synthesis of platinum active sites and Al{sub 2}O{sub 3} overcoats, and evaluation of catalyst propylene hydrogenation activity.

  12. Direct imaging of atomic-scale ripples in few-layer graphene.

    Science.gov (United States)

    Wang, Wei L; Bhandari, Sagar; Yi, Wei; Bell, David C; Westervelt, Robert; Kaxiras, Efthimios

    2012-05-09

    Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberration-corrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.

  13. α-Ga2O3 grown by low temperature atomic layer deposition on sapphire

    Science.gov (United States)

    Roberts, J. W.; Jarman, J. C.; Johnstone, D. N.; Midgley, P. A.; Chalker, P. R.; Oliver, R. A.; Massabuau, F. C.-P.

    2018-04-01

    α-Ga2O3 is a metastable phase of Ga2O3 of interest for wide bandgap engineering since it is isostructural with α-In2O3 and α-Al2O3. α-Ga2O3 is generally synthesised under high pressure (several GPa) or relatively high temperature (∼500 °C). In this study, we report the growth of α-Ga2O3 by low temperature atomic layer deposition (ALD) on sapphire substrate. The film was grown at a rate of 0.48 Å/cycle, and predominantly consists of α-Ga2O3 in the form of (0001) -oriented columns originating from the interface with the substrate. Some inclusions were also present, typically at the tips of the α phase columns and most likely comprising ε-Ga2O3. The remainder of the Ga2O3 film - i.e. nearer the surface and between the α-Ga2O3 columns, was amorphous. The film was found to be highly resistive, as is expected for undoped material. This study demonstrates that α-Ga2O3 films can be grown by low temperature ALD and suggests the possibility of a new range of ultraviolet optoelectronic and power devices grown by ALD. The study also shows that scanning electron diffraction is a powerful technique to identify the different polymorphs of Ga2O3 present in multiphase samples.

  14. Thermal stability of atomic layer deposited WCxNy electrodes for metal oxide semiconductor devices

    Science.gov (United States)

    Zonensain, Oren; Fadida, Sivan; Fisher, Ilanit; Gao, Juwen; Danek, Michal; Eizenberg, Moshe

    2018-01-01

    This study is a thorough investigation of the chemical, structural, and electrical stability of W based organo-metallic films, grown by atomic layer deposition, for future use as gate electrodes in advanced metal oxide semiconductor structures. In an earlier work, we have shown that high effective work-function (4.7 eV) was produced by nitrogen enriched films (WCxNy) dominated by W-N chemical bonding, and low effective work-function (4.2 eV) was produced by hydrogen plasma resulting in WCx films dominated by W-C chemical bonding. In the current work, we observe, using x-ray diffraction analysis, phase transformation of the tungsten carbide and tungsten nitride phases after 900 °C annealing to the cubic tungsten phase. Nitrogen diffusion is also observed and is analyzed with time-of-flight secondary ion mass spectroscopy. After this 900 °C anneal, WCxNy effective work function tunability is lost and effective work-function values of 4.7-4.8 eV are measured, similar to stable effective work function values measured for PVD TiN up to 900 °C anneal. All the observed changes after annealing are discussed and correlated to the observed change in the effective work function.

  15. Thickness dependent growth of low temperature atomic layer deposited zinc oxide films

    International Nuclear Information System (INIS)

    Montiel-González, Z.; Castelo-González, O.A.; Aguilar-Gama, M.T.; Ramírez-Morales, E.; Hu, H.

    2017-01-01

    Highlights: • Polycrystalline columnar ZnO thin films deposited by ALD at low temperatures. • Higher deposition temperature leads to a greater surface roughness in the ALD ZnO films. • Higher temperature originates larger refractive index values of the ALD ZnO films. • ZnO thin films were denser as the numbers of ALD deposition cycles were larger. • XPS analysis revels mayor extent of the DEZ reaction during the ALD process. - Abstract: Zinc oxide films are promising to improve the performance of electronic devices, including those based on organic materials. However, the dependence of the ZnO properties on the preparation conditions represents a challenge to obtain homogeneous thin films that satisfy specific applications. Here, we prepared ZnO films of a wide range of thicknesses by atomic layer deposition (ALD) at relatively low temperatures, 150 and 175 °C. From the results of X-ray photoelectron spectroscopy, X-ray diffraction and Spectroscopic Ellipsometry it is concluded that the polycrystalline structure of the wurtzite is the main phase of the ALD samples, with OH groups on their surface. Ellipsometry revealed that the temperature and the deposition cycles have a strong effect on the films roughness. Scanning electron micrographs evidenced such effect, through the large pyramids developed at the surface of the films. It is concluded that crystalline ZnO thin films within a broad range of thickness and roughness can be obtained for optic or optoelectronic applications.

  16. Atomic-layer-deposited WNxCy thin films as diffusion barrier for copper metallization

    International Nuclear Information System (INIS)

    Kim, Soo-Hyun; Oh, Su Suk; Kim, Ki-Bum; Kang, Dae-Hwan; Li, Wei-Min; Haukka, Suvi; Tuominen, Marko

    2003-01-01

    The properties of WN x C y films deposited by atomic layer deposition (ALD) using WF 6 , NH 3 , and triethyl boron as source gases were characterized as a diffusion barrier for copper metallization. It is noted that the as-deposited film shows an extremely low resistivity of about 350 μΩ cm with a film density of 15.37 g/cm 3 . The film composition measured from Rutherford backscattering spectrometry shows W, C, and N of ∼48, 32, and 20 at. %, respectively. Transmission electron microscopy analyses show that the as-deposited film is composed of face-centered-cubic phase with a lattice parameter similar to both β-WC 1-x and β-W 2 N with an equiaxed microstructure. The barrier property of this ALD-WN x C y film at a nominal thickness of 12 nm deposited between Cu and Si fails only after annealing at 700 deg. C for 30 min

  17. Synthesis of Functional Ceramic Supports by Ice Templating and Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Michaela Klotz

    2018-05-01

    Full Text Available In this work, we report an innovative route for the manufacturing of functional ceramic supports, by combining ice templating of yttria stabilized zirconia (YSZ and atomic layer deposition (ALD of Al2O3 processes. Ceramic YSZ monoliths are prepared using the ice-templating process, which is based on the controlled crystallization of water following a thermal gradient. Sublimation of the ice and the sintering of the material reveal the straight micrometer sized pores shaped by the ice crystal growth. The high temperature sintering allows for the ceramic materials to present excellent mechanical strength and porosities of 67%. Next, the conformality benefit of ALD is used to deposit an alumina coating at the surface of the YSZ pores, in order to obtain a functional material. The Al2O3 thin films obtained by ALD are 100 nm thick and conformally deposited within the macroporous ceramic supports, as shown by SEM and EDS analysis. Mercury intrusion experiments revealed a reduction of the entrance pore diameter, in line with the growth per cycle of 2 Å of the ALD process. In addition to the manufacture of the innovative ceramic nanomaterials, this article also describes the fine characterization of the coatings obtained using mercury intrusion, SEM and XRD analysis.

  18. Silicon surface passivation using thin HfO2 films by atomic layer deposition

    International Nuclear Information System (INIS)

    Gope, Jhuma; Vandana; Batra, Neha; Panigrahi, Jagannath; Singh, Rajbir; Maurya, K.K.; Srivastava, Ritu; Singh, P.K.

    2015-01-01

    Graphical abstract: - Highlights: • HfO 2 films using thermal ALD are studied for silicon surface passivation. • As-deposited thin film (∼8 nm) shows better passivation with surface recombination velocity (SRV) <100 cm/s. • Annealing improves passivation quality with SRV ∼20 cm/s for ∼8 nm film. - Abstract: Hafnium oxide (HfO 2 ) is a potential material for equivalent oxide thickness (EOT) scaling in microelectronics; however, its surface passivation properties particularly on silicon are not well explored. This paper reports investigation on passivation properties of thermally deposited thin HfO 2 films by atomic layer deposition system (ALD) on silicon surface. As-deposited pristine film (∼8 nm) shows better passivation with <100 cm/s surface recombination velocity (SRV) vis-à-vis thicker films. Further improvement in passivation quality is achieved with annealing at 400 °C for 10 min where the SRV reduces to ∼20 cm/s. Conductance measurements show that the interface defect density (D it ) increases with film thickness whereas its value decreases after annealing. XRR data corroborate with the observations made by FTIR and SRV data.

  19. Coating and functionalization of high density ion track structures by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mättö, Laura [Department of Physics, University of Jyväskylä, P.O. Box 35 (YFL), FI-40014 (Finland); Szilágyi, Imre M., E-mail: imre.szilagyi@mail.bme.hu [Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4, Budapest H-1111 (Hungary); MTA-BME Technical Analytical Research Group, Szent Gellért tér 4, Budapest H-1111 (Hungary); Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014 (Finland); Laitinen, Mikko [Department of Physics, University of Jyväskylä, P.O. Box 35 (YFL), FI-40014 (Finland); Ritala, Mikko; Leskelä, Markku [Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014 (Finland); Sajavaara, Timo [Department of Physics, University of Jyväskylä, P.O. Box 35 (YFL), FI-40014 (Finland)

    2016-10-01

    In this study flexible TiO{sub 2} coated porous Kapton membranes are presented having electron multiplication properties. 800 nm crossing pores were fabricated into 50 μm thick Kapton membranes using ion track technology and chemical etching. Consecutively, 50 nm TiO{sub 2} films were deposited into the pores of the Kapton membranes by atomic layer deposition using Ti({sup i}OPr){sub 4} and water as precursors at 250 °C. The TiO{sub 2} films and coated membranes were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectometry (XRR). Au metal electrode fabrication onto both sides of the coated foils was achieved by electron beam evaporation. The electron multipliers were obtained by joining two coated membranes separated by a conductive spacer. The results show that electron multiplication can be achieved using ALD-coated flexible ion track polymer foils. - Highlights: • Porous Kapton membranes were obtained by ion track technology and chemical etching. • TiO{sub 2} films were deposited by ALD into the pores of the Kapton membranes. • TiO{sub 2} nanotube array was prepared by removing the polymer core. • MCP structures were obtained from the coated membranes. • Electron multiplication was achieved using the ALD-coated Kapton foils.

  20. In situ measurement of fixed charge evolution at silicon surfaces during atomic layer deposition

    International Nuclear Information System (INIS)

    Ju, Ling; Watt, Morgan R.; Strandwitz, Nicholas C.

    2015-01-01

    Interfacial fixed charge or interfacial dipoles are present at many semiconductor-dielectric interfaces and have important effects upon device behavior, yet the chemical origins of these electrostatic phenomena are not fully understood. We report the measurement of changes in Si channel conduction in situ during atomic layer deposition (ALD) of aluminum oxide using trimethylaluminum and water to probe changes in surface electrostatics. Current-voltage data were acquired continually before, during, and after the self-limiting chemical reactions that result in film growth. Our measurements indicated an increase in conductance on p-type samples with p + ohmic contacts and a decrease in conductance on analogous n-type samples. Further, p + contacted samples with n-type channels exhibited an increase in measured current and n + contacted p-type samples exhibited a decrease in current under applied voltage. Device physics simulations, where a fixed surface charge was parameterized on the channel surface, connect the surface charge to changes in current-voltage behavior. The simulations and analogous analytical relationships for near-surface conductance were used to explain the experimental results. Specifically, the changes in current-voltage behavior can be attributed to the formation of a fixed negative charge or the modification of a surface dipole upon chemisorption of trimethylaluminum. These measurements allow for the observation of fixed charge or dipole formation during ALD and provide further insight into the electrostatic behavior at semiconductor-dielectric interfaces during film nucleation

  1. Development of TiO2 containing hardmasks through plasma-enhanced atomic layer deposition

    Science.gov (United States)

    De Silva, Anuja; Seshadri, Indira; Chung, Kisup; Arceo, Abraham; Meli, Luciana; Mendoza, Brock; Sulehria, Yasir; Yao, Yiping; Sunder, Madhana; Truong, Hoa; Matham, Shravan; Bao, Ruqiang; Wu, Heng; Felix, Nelson M.; Kanakasabapathy, Sivananda

    2017-04-01

    With the increasing prevalence of complex device integration schemes, trilayer patterning with a solvent strippable hardmask can have a variety of applications. Spin-on metal hardmasks have been the key enabler for selective removal through wet strip when active areas need to be protected from dry etch damage. As spin-on metal hardmasks require a dedicated track to prevent metal contamination and are limited in their ability to scale down thickness without compromising on defectivity, there has been a need for a deposited hardmask solution. Modulation of film composition through deposition conditions enables a method to create TiO2 films with wet etch tunability. This paper presents a systematic study on development and characterization of plasma-enhanced atomic layer deposited (PEALD) TiO2-based hardmasks for patterning applications. We demonstrate lithographic process window, pattern profile, and defectivity evaluation for a trilayer scheme patterned with PEALD-based TiO2 hardmask and its performance under dry and wet strip conditions. Comparable structural and electrical performance is shown for a deposited versus a spin-on metal hardmask.

  2. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    International Nuclear Information System (INIS)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G.; Posadas, Agham; Demkov, Alexander A.

    2015-01-01

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al 2 O 3 and HfO 2 . However, there has been much effort to deposit ternary oxides, such as perovskites (ABO 3 ), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable

  3. Impact of Atomic Layer Deposition to NanoPhotonic Structures and Devices: A Review

    Directory of Open Access Journals (Sweden)

    Muhammad Rizwan eSaleem

    2014-10-01

    Full Text Available We review the significance of optical thin films by Atomic Layer Deposition (ALD method to fabricate nanophotonic devices and structures. ALD is a versatile technique to deposit functional coatings on reactive surfaces with conformal growth of compound materials, precise thickness control capable of angstrom resolution and coverage of high aspect ratio nanostructures using wide range of materials. ALD has explored great potential in the emerging fields of photonics, plasmonics, nano-biotechnology, and microelectronics. ALD technique uses sequential reactive chemical reactions to saturate a surface with a monolayer by pulsing of a first precursor (metal alkoxides or covalent halides, followed by reaction with second precursor molecules such as water to form the desired compound coatings. The targeted thickness of the desired compound material is controlled by the number of ALD cycles of precursor molecules that ensures the self limiting nature of reactions. The conformal growth and filling of TiO2 and Al2O3 optical material on nanostructures and their resulting optical properties have been described. The low temperature ALD-growth on various replicated sub-wavelength polymeric gratings is discussed.

  4. Growth of Fe2O3 thin films by atomic layer deposition

    International Nuclear Information System (INIS)

    Lie, M.; Fjellvag, H.; Kjekshus, A.

    2005-01-01

    Thin films of α-Fe 2 O 3 (α-Al 2 O 3 -type crystal structure) and γ-Fe 2 O 3 (defect-spinel-type crystal structure) have been grown by the atomic layer deposition (ALD) technique with Fe(thd) 3 (iron derivative of Hthd = 2,2,6,6-tetramethylheptane-3,5-dione) and ozone as precursors. It has been shown that an ALD window exists between 160 and 210 deg. C. The films have been characterized by various techniques and are shown to comprise (001)-oriented columns of α-Fe 2 O 3 with no in-plane orientation when grown on soda-lime-glass and Si(100) substrates. Good quality films have been made with thicknesses ranging from 10 to 130 nm. Films grown on α-Al 2 O 3 (001) and MgO(100) substrates have the α-Fe 2 O 3 and γ-Fe 2 O 3 crystal structure, respectively, and consist of highly oriented columns with in-plane orientations matching those of the substrates

  5. Development of Nitride Coating Using Atomic Layer Deposition for Low-Enriched Uranium Fuel Powder

    Science.gov (United States)

    Bhattacharya, Sumit

    High-performance research reactors require fuel that operates at high specific power and can withstand high fission density, but at relatively low temperatures. The design of the research reactor fuels is done for efficient heat emission, and consists of assemblies of thin-plates cladding made from aluminum alloy. The low-enriched fuels (LEU) were developed for replacing high-enriched fuels (HEU) for these reactors necessitates a significantly increased uranium density in the fuel to counterbalance the decrease in enrichment. One of the most promising new fuel candidate is U-Mo alloy, in a U-Mo/Al dispersion fuel form, due to its high uranium loading as well as excellent irradiation resistance performance, is being developed extensively to convert from HEU fuel to LEU fuel for high-performance research reactors. However, the formation of an interaction layer (IL) between U-Mo particles and the Al matrix, and the associated pore formation, under high heat flux and high burnup conditions, degrade the irradiation performance of the U-Mo/Al dispersion fuel. From the recent tests results accumulated from the surface engineering of low enriched uranium fuel (SELENIUM) and MIR reactor displayed that a surface barrier coating like physical vapor deposited (PVD) zirconium nitride (ZrN) can significantly reduce the interaction layer. The barrier coating performed well at low burn up but above a fluence rate of 5x 1021 ions/cm2 the swelling reappeared due to formation interaction layer. With this result in mind the objective of this research was to develop an ultrathin ZrN coating over particulate uranium-molybdenum nuclear fuel using a modified savannah 200 atomic layer deposition (ALD) system. This is done in support of the US Department of Energy's (DOE) effort to slow down the interaction at fluence rate and reach higher burn up for high power research reactor. The low-pressure Savannah 200 ALD system is modified to be designed as a batch powder coating system using the

  6. Efficiency Enhancement of Nanotextured Black Silicon Solar Cells Using Al2O3/TiO2 Dual-Layer Passivation Stack Prepared by Atomic Layer Deposition.

    Science.gov (United States)

    Wang, Wei-Cheng; Tsai, Meng-Chen; Yang, Jason; Hsu, Chuck; Chen, Miin-Jang

    2015-05-20

    In this study, efficient nanotextured black silicon (NBSi) solar cells composed of silicon nanowire arrays and an Al2O3/TiO2 dual-layer passivation stack on the n(+) emitter were fabricated. The highly conformal Al2O3 and TiO2 surface passivation layers were deposited on the high-aspect-ratio surface of the NBSi wafers using atomic layer deposition. Instead of the single Al2O3 passivation layer with a negative oxide charge density, the Al2O3/TiO2 dual-layer passivation stack treated with forming gas annealing provides a high positive oxide charge density and a low interfacial state density, which are essential for the effective field-effect and chemical passivation of the n(+) emitter. In addition, the Al2O3/TiO2 dual-layer passivation stack suppresses the total reflectance over a broad range of wavelengths (400-1000 nm). Therefore, with the Al2O3/TiO2 dual-layer passivation stack, the short-circuit current density and efficiency of the NBSi solar cell were increased by 11% and 20%, respectively. In conclusion, a high efficiency of 18.5% was achieved with the NBSi solar cells by using the n(+)-emitter/p-base structure passivated with the Al2O3/TiO2 stack.

  7. Influence of titanium-substrate roughness on Ca–P–O thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ananda Sagari, A.R., E-mail: arsagari@gmail.com [Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä (Finland); Malm, Jari [Department of Chemistry, P.O. Box 16100, FI-00076 Aalto University, Espoo (Finland); Laitinen, Mikko [Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä (Finland); Rahkila, Paavo [Department of Biology of Physical Activity, P.O. Box 35, FIN-40014 University of Jyväskylä (Finland); Hongqiang, Ma [Department of Health Sciences, P.O. Box 35 (L), FIN-40014 University of Jyväskylä (Finland); Putkonen, Matti [Department of Chemistry, P.O. Box 16100, FI-00076 Aalto University, Espoo (Finland); Beneq Oy, P.O. Box 262, FI-01511 Vantaa (Finland); Karppinen, Maarit [Department of Chemistry, P.O. Box 16100, FI-00076 Aalto University, Espoo (Finland); Whitlow, Harry J.; Sajavaara, Timo [Department of Physics, P.O. Box 35 (YFL), FIN-40014 University of Jyväskylä (Finland)

    2013-03-01

    Amorphous Ca–P–O films were deposited on titanium substrates using atomic layer deposition, while maintaining a uniform Ca/P pulsing ratio of 6/1 with varying number of atomic layer deposition cycles starting from 10 up to 208. Prior to film deposition the titanium substrates were mechanically abraded using SiC abrasive paper of 600, 1200, 2000 grit size and polished with 3 μm diamond paste to obtain surface roughness R{sub rms} values of 0.31 μm, 0.26 μm, 0.16 μm, and 0.10 μm, respectively. The composition and film thickness of as-deposited amorphous films were studied using Time-Of-Flight Elastic Recoil Detection Analysis. The results showed that uniform films could be deposited on rough metal surfaces with a clear dependence of substrate roughness on the Ca/P atomic ratio of thin films. The in vitro cell-culture studies using MC3T3 mouse osteoblast showed a greater coverage of cells on the surface polished with diamond paste in comparison to rougher surfaces after 24 h culture. No statistically significant difference was observed between Ca–P–O coated and un-coated Ti surfaces for the measured roughness value. The deposited 50 nm thick films did not dissolve during the cell culture experiment. - Highlights: ► Atomic layer deposition of Ca–P–O films on abraded Ti substrate ► Surface analysis using Time-Of-Flight Elastic Recoil Detection Analysis ► Dependence of substrate roughness on the Ca/P atomic ratio of thin films ► An increase in Ca/P atomic ratio with decreasing roughness ► Mouse osteoblast showed greater coverage of cells in polished surface.

  8. Phase time delay and Hartman effect in a one-dimensional photonic crystal with four-level atomic defect layer

    Science.gov (United States)

    Jamil, Rabia; Ali, Abu Bakar; Abbas, Muqaddar; Badshah, Fazal; Qamar, Sajid

    2017-08-01

    The Hartman effect is revisited using a Gaussian beam incident on a one-dimensional photonic crystal (1DPC) having a defect layer doped with four-level atoms. It is considered that each atom of the defect layer interacts with three driving fields, whereas a Gaussian beam of width w is used as a probe light to study Hartman effect. The atom-field interaction inside the defect layer exhibits electromagnetically induced transparency (EIT). The 1DPC acts as positive index material (PIM) and negative index material (NIM) corresponding to the normal and anomalous dispersion of the defect layer, respectively, via control of the phase associated with the driving fields and probe detuning. The positive and negative Hartman effects are noticed for PIM and NIM, respectively, via control of the relative phase corresponding to the driving fields and probe detuning. The advantage of using four-level EIT system is that a much smaller absorption of the transmitted beam occurs as compared to three-level EIT system corresponding to the anomalous dispersion, leading to negative Hartman effect.

  9. Breakthrough to Non-Vacuum Deposition of Single-Crystal, Ultra-Thin, Homogeneous Nanoparticle Layers: A Better Alternative to Chemical Bath Deposition and Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Yu-Kuang Liao

    2017-04-01

    Full Text Available Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin films with the thickness of a few nanometers on rough surfaces. We present a new ”paradigm shift” non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD and chemical bath deposition (CBD as used by the Cu(In,GaSe2 (CIGS thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase.

  10. Atomic to Nanoscale Investigation of Functionalities of Al2O3 Coating Layer on Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, Jie; Zhang, Jiguang; Wang, Chong M.

    2016-01-06

    Surface coating of cathode has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin layer of coating, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration corrected scanning transmission electron microscopy and high efficient spectroscopy to probe the delicate functioning mechanism of Al2O3 coating layer on Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between cathode and the electrolyte upon the battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore avoiding the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will initiate from the particle surface and propagate towards the interior of the particle with the progression of the battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight for optimized design of coating layer on cathode to enhance the battery properties.

  11. Self-assembly of alkanethiolates directs sulfur bonding with GaAs(100)

    Energy Technology Data Exchange (ETDEWEB)

    Mancheno-Posso, Pablo; Muscat, Anthony J., E-mail: muscat@email.arizona.edu

    2017-03-01

    Highlights: • Alkanethiolate monolayers were formed on GaAs(100) using a 20 min liquid immersion. • The longest chain containing 20 CH{sub 2} groups protected the surface for 30 min from reoxidation. • A reaction-diffusion model shows that oxygen diffusion through the carbon chains is fast. • Alkanethiolates protect the surface by reducing the reaction rate of oxygen with the surface. • Assembly of the alkane chains directs sulfur atoms to bond to the surface. - Abstract: Molecules that contain linear alkane chains self-assemble on a variety of surfaces changing the degree of wetting, lubricity, and reactivity. We report on the reoxidation of GaAs(100) in air after adsorbing five alkanethiols (C{sub n}H{sub 2n+1}-SH where n = 3, 6, 12, 18, 20) and one alkanedithiol (HS-(CH{sub 2}){sub 8}-SH) deposited from the liquid phase. The alignment of the alkane chains forms a self-assembled layer, however, air diffuses readily through the carbon layer and reaches the surface. The impact of alignment is to improve the bonding of sulfur with the surface atoms which reduces the oxidation rate based on fitting the data to a reaction-diffusion model. The layer thickness and molecular density scale linearly with the number of carbon atoms in the alkane chain. The thickness of the alkanethiolate (RS{sup −}) layer grows by 0.87 ± 0.06 Å for each C atom in the chain and the surface density by 0.13 ± 0.03 molecule per nm{sup 2} per C atom up to a coverage of 5.0 molecules/nm{sup 2} for n = 20 or 0.8 monolayer. The surface coverage increases with length because interactions between methylene (CH{sub 2}) groups in neighboring chains reduce the tilt angle of the molecules with the surface normal. The tight packing yields areas per alkanethiolate as low as 20 Å{sup 2} for n = 20. The amount of C in the layer divided by the chain length is approximately constant up to n = 12 but increases sharply by a factor of 2–4× for n = 18 and 20 based on the C 1s X

  12. Effect of ozone concentration on silicon surface passivation by atomic layer deposited Al2O3

    International Nuclear Information System (INIS)

    Gastrow, Guillaume von; Li, Shuo; Putkonen, Matti; Laitinen, Mikko; Sajavaara, Timo; Savin, Hele

    2015-01-01

    Highlights: • The ALD Al 2 O 3 passivation quality can be controlled by the ozone concentration. • Ozone concentration affects the Si/Al 2 O 3 interface charge and defect density. • A surface recombination velocity of 7 cm/s is reached combining ozone and water ALD. • Carbon and hydrogen concentrations correlate with the surface passivation quality. - Abstract: We study the impact of ozone-based Al 2 O 3 Atomic Layer Deposition (ALD) on the surface passivation quality of crystalline silicon. We show that the passivation quality strongly depends on the ozone concentration: the higher ozone concentration results in lower interface defect density and thereby improved passivation. In contrast to previous studies, our results reveal that too high interface hydrogen content can be detrimental to the passivation. The interface hydrogen concentration can be optimized by the ozone-based process; however, the use of pure ozone increases the harmful carbon concentration in the film. Here we demonstrate that low carbon and optimal hydrogen concentration can be achieved by a single process combining the water- and ozone-based reactions. This process results in an interface defect density of 2 × 10 11 eV −1 cm −2 , and maximum surface recombination velocities of 7.1 cm/s and 10 cm/s, after annealing and after an additional firing at 800 °C, respectively. In addition, our results suggest that the effective oxide charge density can be optimized in a simple way by varying the ozone concentration and by injecting water to the ozone process.

  13. Atomic layer deposition: an enabling technology for the growth of functional nanoscale semiconductors

    Science.gov (United States)

    Biyikli, Necmi; Haider, Ali

    2017-09-01

    In this paper, we present the progress in the growth of nanoscale semiconductors grown via atomic layer deposition (ALD). After the adoption by semiconductor chip industry, ALD became a widespread tool to grow functional films and conformal ultra-thin coatings for various applications. Based on self-limiting and ligand-exchange-based surface reactions, ALD enabled the low-temperature growth of nanoscale dielectric, metal, and semiconductor materials. Being able to deposit wafer-scale uniform semiconductor films at relatively low-temperatures, with sub-monolayer thickness control and ultimate conformality, makes ALD attractive for semiconductor device applications. Towards this end, precursors and low-temperature growth recipes are developed to deposit crystalline thin films for compound and elemental semiconductors. Conventional thermal ALD as well as plasma-assisted and radical-enhanced techniques have been exploited to achieve device-compatible film quality. Metal-oxides, III-nitrides, sulfides, and selenides are among the most popular semiconductor material families studied via ALD technology. Besides thin films, ALD can grow nanostructured semiconductors as well using either template-assisted growth methods or bottom-up controlled nucleation mechanisms. Among the demonstrated semiconductor nanostructures are nanoparticles, nano/quantum-dots, nanowires, nanotubes, nanofibers, nanopillars, hollow and core-shell versions of the afore-mentioned nanostructures, and 2D materials including transition metal dichalcogenides and graphene. ALD-grown nanoscale semiconductor materials find applications in a vast amount of applications including functional coatings, catalysis and photocatalysis, renewable energy conversion and storage, chemical sensing, opto-electronics, and flexible electronics. In this review, we give an overview of the current state-of-the-art in ALD-based nanoscale semiconductor research including the already demonstrated and future applications.

  14. In situ metrology to characterize water vapor delivery during atomic layer deposition

    International Nuclear Information System (INIS)

    Ahmido, Tariq; Kimes, William A.; Sperling, Brent A.; Hodges, Joseph T.; Maslar, James E.

    2016-01-01

    Water is often employed as the oxygen source in metal oxide atomic layer deposition (ALD) processes. It has been reported that variations in the amount of water delivered during metal oxide ALD can impact the oxide film properties. Hence, one contribution to optimizing metal oxide ALD processes would be to identify methods to better control water dose. The development of rapid, quantitative techniques for in situ water vapor measurements during ALD processes would be beneficial to achieve this goal. In this report, the performance of an in situ tunable diode laser absorption spectroscopy (TDLAS) scheme for performing rapid, quantitative water partial pressure measurements in a representative quarter-inch ALD delivery line is described. This implementation of TDLAS, which utilizes a near-infrared distributed-feedback diode laser and wavelength modulation spectroscopy, provides measurements of water partial pressure on a timescale comparable to or shorter than the timescale of the gas dynamics in typical ALD systems. Depending on the degree of signal averaging, this TDLAS system was capable of measuring the water partial pressure with a detection limit in the range of ∼0.80 to ∼0.08 Pa. The utility of this TDLAS scheme was demonstrated by using it to identify characteristics of a representative water delivery system that otherwise would have been difficult to predict. Those characteristics include (1) the magnitude and time dependence of the pressure transient that can occur during water injection, and (2) the dependence of the steady-state water partial pressure on the carrier gas flow rate and the setting of the water ampoule flow restriction.

  15. Rotary reactor for atomic layer deposition on large quantities of nanoparticles

    International Nuclear Information System (INIS)

    McCormick, J. A.; Cloutier, B. L.; Weimer, A. W.; George, S. M.

    2007-01-01

    Challenges are encountered during atomic layer deposition (ALD) on large quantities of nanoparticles. The particles must be agitated or fluidized to perform the ALD surface reactions in reasonable times and to prevent the particles from being agglomerated by the ALD film. The high surface area of nanoparticles also demands efficient reactant usage because large quantities of reactant are required for the surface reactions to reach completion. The residence time of the reactant in a fluidized particle bed reactor may be too short for high efficiency if the ALD surface reactions have low reactive sticking coefficients. To address these challenges, a novel rotary reactor was developed to achieve constant particle agitation during static ALD reactant exposures. In the design of this new reactor, a cylindrical drum with porous metal walls was positioned inside a vacuum chamber. The porous cylindrical drum was rotated by a magnetically coupled rotary feedthrough. By rotating the cylindrical drum to obtain a centrifugal force of less than one gravitational force, the particles were agitated by a continuous 'avalanche' of particles. In addition, an inert N 2 gas pulse helped to dislodge the particles from the porous walls and provided an efficient method to purge reactants and products from the particle bed. The effectiveness of this rotary reactor was demonstrated by Al 2 O 3 ALD on ZrO 2 particles. A number of techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy confirmed that the Al 2 O 3 ALD film conformally coats the ZrO 2 particles. Combining static reactant exposures with a very high surface area sample in the rotary reactor also provides unique opportunities for studying the surface chemistry during ALD

  16. Spatial atomic layer deposition on flexible substrates using a modular rotating cylinder reactor

    International Nuclear Information System (INIS)

    Sharma, Kashish; Hall, Robert A.; George, Steven M.

    2015-01-01

    Spatial atomic layer deposition (ALD) is a new version of ALD based on the separation of reactant gases in space instead of time. In this paper, the authors present results for spatial ALD on flexible substrates using a modular rotating cylinder reactor. The design for this reactor is based on two concentric cylinders. The outer cylinder remains fixed and contains a series of slits. These slits can accept a wide range of modules that attach from the outside. The modules can easily move between the various slit positions and perform precursor dosing, purging, or pumping. The inner cylinder rotates with the flexible substrate and passes underneath the various spatially separated slits in the outer cylinder. Trimethyl aluminum and ozone were used to grow Al 2 O 3 ALD films at 40 °C on metallized polyethylene terephthalate (PET) substrates to characterize this spatial ALD reactor. Spectroscopic ellipsometry measurements revealed a constant Al 2 O 3 ALD growth rate of 1.03 Å/cycle with rotation speeds from 40 to 100 RPM with the outer cylinder configured for one Al 2 O 3 ALD cycle per rotation. The Al 2 O 3 ALD growth rate then decreased at higher rotation rates for reactant residence times < 5 ms. The Al 2 O 3 ALD films were also uniform to within <1% across the central portion of metallized PET substrate. Fixed deposition time experiments revealed that Al 2 O 3 ALD films could be deposited at 2.08 Å/s at higher rotation speeds of 175 RPM. Even faster deposition rates are possible by adding more modules for additional Al 2 O 3 ALD cycles for every one rotation of the inner cylinder

  17. Thin film growth into the ion track structures in polyimide by atomic layer deposition

    Science.gov (United States)

    Mättö, L.; Malm, J.; Arstila, K.; Sajavaara, T.

    2017-09-01

    High-aspect ratio porous structures with controllable pore diameters and without a stiff substrate can be fabricated using the ion track technique. Atomic layer deposition is an ideal technique for depositing thin films and functional surfaces on complicated 3D structures due to the high conformality of the films. In this work, we studied Al2O3 and TiO2 films grown by ALD on pristine polyimide (Kapton HN) membranes as well as polyimide membranes etched in sodium hypochlorite (NaOCl) and boric acid (BO3) solution by means of RBS, PIXE, SEM-EDX and helium ion microcopy (HIM). The focus was on the first ALD growth cycles. The areal density of Al2O3 film in the 400 cycle sample was determined to be 51 ± 3 × 1016 at./cm2, corresponding to the thickness of 55 ± 3 nm. Furthermore, the growth per cycle was 1.4 Å/cycle. The growth is highly linear from the first cycles. In the case of TiO2, the growth per cycle is clearly slower during the first 200 cycles but then it increases significantly. The growth rate based on RBS measurements is 0.24 Å/cycle from 3 to 200 cycles and then 0.6 Å/cycle between 200 and 400 cycles. The final areal density of TiO2 film after 400 cycles is 148 ± 3 × 1015 at./cm2 which corresponds to the thickness of 17.4 ± 0.4 nm. The modification of the polyimide surface by etching prior to the deposition did not have an effect on the Al2O3 and TiO2 growth.

  18. Metalorganic atomic layer deposition of TiN thin films using TDMAT and NH3

    International Nuclear Information System (INIS)

    Kim, Hyo Kyeom; Kim, Ju Youn; Park, Jin Yong; Kim, Yang Do; Kim, Young Do; Jeon, Hyeong Tag; Kim, Won Mok

    2002-01-01

    TiN films were deposited by using the metalorganic atomic layer deposition (MOALD) method using tetrakis-dimethyl-amino-titanium (TDMAT) as the titanium precursor and ammonia (NH 3 ) as the reactant gas. Two saturated TiN film growth regions were observed in the temperature ranges from 175 and 190 .deg. C and from 200 and 210 .deg. C. TiN films deposited by the MOALD technique showed relatively lower carbon content than films deposited by metalorganic chemical vapor deposition (MOCVD) method. TiN films deposited at around 200 .deg. C under standard conditions showed the resistivity values as low as 500 μΩ-cm, which is about one order lower than the values for TiN films deposited by MOCVD using TDMAT or TDMAT with NH 3 . Also, the carbon incorporation and the resistivity were further decreased with increasing Ar purge time and flow rate. TiN films deposited at temperature below 300 .deg. C showed amorphous characteristics. TiN film deposited on contact holes, about 0.4-μm wide and 0.8-μm deep, by using the MOALD method showed excellent conformal deposition with almost 100% step coverage. This study demonstrates that the processing parameters need to be carefully controlled to optimize the film properties that the processing parameters need to be carefully controlled to optimize the film properties when using the ALD technique and that TiN films deposited by using the MOALD method exhibited excellent film properties compared to those of films deposited by using other CVD methods

  19. Scanning microwave microscopy applied to semiconducting GaAs structures

    Science.gov (United States)

    Buchter, Arne; Hoffmann, Johannes; Delvallée, Alexandra; Brinciotti, Enrico; Hapiuk, Dimitri; Licitra, Christophe; Louarn, Kevin; Arnoult, Alexandre; Almuneau, Guilhem; Piquemal, François; Zeier, Markus; Kienberger, Ferry

    2018-02-01

    A calibration algorithm based on one-port vector network analyzer (VNA) calibration for scanning microwave microscopes (SMMs) is presented and used to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample. This robust and versatile algorithm is instrument and frequency independent, as we demonstrate by analyzing experimental data from two different, cantilever- and tuning fork-based, microscope setups operating in a wide frequency range up to 27.5 GHz. To benchmark the SMM results, comparison with secondary ion mass spectrometry is undertaken. Furthermore, we show SMM data on a GaAs p-n junction distinguishing p- and n-doped layers.

  20. Effect of atomic layer deposited Al2O3:ZnO alloys on thin-film silicon photovoltaic devices

    Science.gov (United States)

    Abdul Hadi, Sabina; Dushaq, Ghada; Nayfeh, Ammar

    2017-12-01

    In this work, we present the effects of the Al2O3:ZnO ratio on the optical and electrical properties of aluminum doped ZnO (AZO) layers deposited by atomic layer deposition, along with AZO application as the anti-reflective coating (ARC) layer and in heterojunction configurations. Here, we report complex refractive indices for AZO layers with different numbers of aluminum atomic cycles (ZnO:Al2O3 = 1:0, 39:1, 19:1, and 9:1) and we confirm their validity by fitting models to experimental data. Furthermore, the most conductive layer (ZnO:Al2O3 = 19:1, conductivity ˜4.6 mΩ cm) is used to fabricate AZO/n+/p-Si thin film solar cells and AZO/p-Si heterojunction devices. The impact of the AZO layer on the photovoltaic properties of these devices is studied by different characterization techniques, resulting in the extraction of recombination and energy band parameters related to the AZO layer. Our results confirm that AZO 19:1 can be used as a low cost and effective conductive ARC layer for solar cells. However, AZO/p-Si heterojunctions suffer from an insufficient depletion region width (˜100 nm) and recombination at the interface states, with an estimated potential barrier of ˜0.6-0.62 eV. The work function of AZO (ZnO:Al2O3 = 19:1) is estimated to be in the range between 4.36 and 4.57 eV. These material properties limit the use of AZO as an emitter in Si solar cells. However, the results imply that AZO based heterojunctions could have applications as low-cost photodetectors or photodiodes, operating under relatively low reverse bias.