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Sample records for bscf epitaxial thin

  1. Thin epitaxial silicon detectors

    International Nuclear Information System (INIS)

    Stab, L.

    1989-01-01

    Manufacturing procedures of thin epitaxial surface barriers will be given. Some improvements have been obtained: larger areas, lower leakage currents and better resolutions. New planar epitaxial dE/dX detectors, made in a collaboration work with ENERTEC-INTERTECHNIQUE, and a new application of these thin planar diodes to EXAFS measurements, made in a collaboration work with LURE (CNRS,CEA,MEN) will also be reported

  2. Epitaxy, thin films and superlattices

    International Nuclear Information System (INIS)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au)

  3. Epitaxy, thin films and superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au) 14 tabs.; 58 ills., 96 refs.

  4. Ion beam deposited epitaxial thin silicon films

    International Nuclear Information System (INIS)

    Orrman-Rossiter, K.G.; Al-Bayati, A.H.; Armour, D.G.; Donnelly, S.E.; Berg, J.A. van den

    1991-01-01

    Deposition of thin films using low energy, mass-separated ion beams is a potentially important low temperature method of producing epitaxial layers. In these experiments silicon films were grown on Si (001) substrates using 10-200 eV 28 Si + and 30 Si + ions at substrate temperatures in the range 273-1073 K, under ultrahigh-vacuum conditions (deposition pressure -7 Pa). The film crystallinity was assessed in situ using medium energy ion scattering (MEIS). Films of crystallinity comparable to bulk samples were grown using 10-40 eV 28 Si + and 30 Si + ions at deposition temperatures in the range 623-823 K. These experiments confirmed the role of key experimental parameters such as ion energy, substrate temperature during deposition, and the surface treatment prior to deposition. It was found that a high temperature in situ anneal (1350-1450 K) gave the best results for epitaxial nucleation, whereas low energy (20-40 eV) Cl + ion bombardment resulted in amorphous film growth. The deposition energy for good epitaxial growth indicates that it is necessary to provide enough energy to induce local mobility but not to cause atomic displacements leading to the buildup of stable defects, e.g. divacancies, below the surface layer of the growing film. (orig.)

  5. Strain quantification in epitaxial thin films

    International Nuclear Information System (INIS)

    Cushley, M

    2008-01-01

    Strain arising in epitaxial thin films can be beneficial in some cases but devastating in others. By altering the lattice parameters, strain may give a thin film properties hitherto unseen in the bulk material. On the other hand, heavily strained systems are prone to develop lattice defects in order to relieve the strain, which can cause device failure or, at least, a decrease in functionality. Using convergent beam electron diffraction (CBED) and high-resolution transmission electron microscopy (HRTEM), it is possible to determine local strains within a material. By comparing the results from CBED and HRTEM experiments, it is possible to gain a complete view of a material, including the strain and any lattice defects present. As well as looking at how the two experimental techniques differ from each other, I will also look at how results from different image analysis algorithms compare. Strain in Si/SiGe samples and BST/SRO/MgO capacitor structures will be discussed.

  6. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José ; Burriel, Mó nica

    2010-01-01

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation

  7. Yttrium doped BSCF membranes for oxygen separation

    DEFF Research Database (Denmark)

    Haworth, P.; Smart, S.; Glasscock, Julie

    2011-01-01

    This work investigates the partial substitution of yttrium in place of iron in BSCF to form Ba0.5Sr0.5Co0.8Fe0.2−xYxO3−δ, where x varied between 0 and 0.2. X-ray diffraction patterns showed the formation of a perovskite cubic phase structure up to x = 0.15, whilst the full substitution of yttrium...

  8. Electrical properties of epitaxially grown VOx thin films

    NARCIS (Netherlands)

    Rata, A.D.; Chezan, A.R; Presura, C.N.; Hibma, T

    2003-01-01

    High quality VOx thin films on MgO(100) substrates were prepared and studied from the structural and electronic point of view. Epitaxial growth was confirmed by RHEED and XRD techniques. The oxygen content of VOx thin films as a function of oxygen flux was determined using RBS. The upper and lower

  9. Epitaxial patterning of thin-films: conventional lithographies and beyond

    International Nuclear Information System (INIS)

    Zhang, Wei; Krishnan, Kannan M

    2014-01-01

    Thin-film based novel magnetic and electronic devices have entered a new era in which the film crystallography, structural coherence, and epitaxy play important roles in determining their functional properties. The capabilities of controlling such structural and functional properties are being continuously developed by various physical deposition technologies. Epitaxial patterning strategies further allow the miniaturization of such novel devices, which incorporates thin-film components into nanoscale architectures while keeping their functional properties unmodified from their ideal single-crystal values. In the past decade, epitaxial patterning methods on the laboratory scale have been reported to meet distinct scientific inquires, in which the techniques and processes used differ from one to the other. In this review we summarize many of these pioneering endeavors in epitaxial patterning of thin-film devices that use both conventional and novel lithography techniques. These methods demonstrate epitaxial patterning for a broad range of materials (metals, oxides, and semiconductors) and cover common device length scales from micrometer to sub-hundred nanometer. Whilst we have been motivated by magnetic materials and devices, we present our outlook on developing systematic-strategies for epitaxial patterning of functional materials which will pave the road for the design, discovery and industrialization of next-generation advanced magnetic and electronic nano-devices. (topical review)

  10. Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

    Science.gov (United States)

    Xia, Wei; Chen, Qiusong; Zhang, Jian; Wang, Hui; Cheng, Qian; Jiang, Yulong; Zhu, Guodong

    2018-04-01

    In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

  11. Strain-induced properties of epitaxial VOx thin films

    NARCIS (Netherlands)

    Rata, AD; Hibma, T

    We have grown VOx thin films on different substrates in order to investigate the influence of epitaxial strain on the transport properties. We found that the electric conductivity is much larger for films grown under compressive strain on SrTiO3 substrates, as compared to bulk material and VOx films

  12. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya; Shekhah, Osama; Spanopoulos, Ioannis; Trikalitis, Pantelis N.; Eddaoudi, Mohamed

    2017-01-01

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  13. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya

    2017-05-10

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  14. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José

    2010-10-24

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation and strain in oxide ionic conducting materials used as electrolytes, such as fluorites, and in mixed ionic and electronic conducting materials used as electrodes, typically oxides with perovskite or perovskite-related layered structures. The recent effort towards the enhancement of the electrochemical performance of SOFC materials through the deposition of artificial film heterostructures is also presented. These thin films have been engineered at a nanoscale level, such as the case of epitaxial multilayers or nanocomposite cermet materials. The recent progress in the implementation of thin films in SOFC devices is also reported. © 2010 Springer-Verlag.

  15. Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

    Science.gov (United States)

    Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

    2018-04-25

    In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

  16. Single-domain epitaxial silicene on diboride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fleurence, A., E-mail: antoine@jaist.ac.jp; Friedlein, R.; Aoyagi, K.; Yamada-Takamura, Y. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Gill, T. G. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Sadowski, J. T. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Copel, M.; Tromp, R. M. [IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Hirjibehedin, C. F. [London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Department of Physics and Astronomy, UCL, London WC1E 6BT (United Kingdom)

    2016-04-11

    Epitaxial silicene, which forms spontaneously on ZrB{sub 2}(0001) thin films grown on Si(111) wafers, has a periodic stripe domain structure. By adsorbing additional Si atoms on this surface, we find that the domain boundaries vanish, and a single-domain silicene sheet can be prepared without altering its buckled honeycomb structure. The amount of Si required to induce this change suggests that the domain boundaries are made of a local distortion of the silicene honeycomb lattice. The realization of a single domain sheet with structural and electronic properties close to those of the original striped state demonstrates the high structural flexibility of silicene.

  17. Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering

    KAUST Repository

    Pergolesi, Daniele; Roddatis, Vladimir; Fabbri, Emiliana; Schneider, Christof W; Lippert, Thomas; Traversa, Enrico; Kilner, John A

    2015-01-01

    Highly textured thin films with small grain boundary regions can be used as model systems to directly measure the bulk conductivity of oxygen ion conducting oxides. Ionic conducting thin films and epitaxial heterostructures are also widely used

  18. High performance yttrium-doped BSCF hollow fibre membranes

    DEFF Research Database (Denmark)

    Haworth, P.; Smart, S.; Glasscock, Julie

    2012-01-01

    measurements in air was similar for both compositions, suggesting that the higher oxygen fluxes obtained for BSCFY hollow fibres could be attributed to the higher non-stoichiometry due to yttrium addition to the BSCF crystal structure. In addition, the improvement of oxygen fluxes for small wall thickness (∼0...

  19. Chemically stabilized epitaxial wurtzite-BN thin film

    Science.gov (United States)

    Vishal, Badri; Singh, Rajendra; Chaturvedi, Abhishek; Sharma, Ankit; Sreedhara, M. B.; Sahu, Rajib; Bhat, Usha; Ramamurty, Upadrasta; Datta, Ranjan

    2018-03-01

    We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

  20. Resistance switching in epitaxial SrCoOx thin films

    Science.gov (United States)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-08-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO2.5) and conducting perovskite (SrCoO3-δ) depending on the oxygen content. The current-voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoOx thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO2.5.

  1. Resistance switching in epitaxial SrCoOx thin films

    International Nuclear Information System (INIS)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-01-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO 3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO 2.5 ) and conducting perovskite (SrCoO 3−δ ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO 2.5

  2. 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

  3. Epitaxial ternary nitride thin films prepared by a chemical solution method

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Hongmei [Los Alamos National Laboratory; Feldmann, David M [Los Alamos National Laboratory; Wang, Haiyan [TEXAS A& M; Bi, Zhenxing [TEXAS A& M

    2008-01-01

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

  4. Epitaxial growth of SrTiO3 thin film on Si by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhou, X. Y.; Miao, J.; Dai, J. Y.; Chan, H. L. W.; Choy, C. L.; Wang, Y.; Li, Q.

    2007-01-01

    SrTiO 3 thin films have been deposited on Si (001) wafers by laser molecular beam epitaxy using an ultrathin Sr layer as the template. X-ray diffraction measurements indicated that SrTiO 3 was well crystallized and epitaxially aligned with Si. Cross-sectional observations in a transmission electron microscope revealed that the SrTiO 3 /Si interface was sharp, smooth, and fully crystallized. The thickness of the Sr template was found to be a critical factor that influenced the quality of SrTiO 3 and the interfacial structure. Electrical measurements revealed that the SrTiO 3 film was highly resistive

  5. Magnetoresistance at artificial interfaces in epitaxial ferromagnetic thin films

    International Nuclear Information System (INIS)

    Fontcuberta, J.; Bibes, M.; Martinez, B.; Trtik, V.; Ferrater, C.; Sanchez, F.; Varela, M.

    2000-01-01

    Epitaxial La 2/3 Sr 1/3 MnO 3 and SrRuO 3 thin films have been grown by laser ablation on single-crystalline SrTiO 3 substrates. Prior to manganite or ruthenate deposition tracks have been patterned on the SrTiO 3 substrate by using an appropriately focused laser beam. In the experiments here reported linear tracks have been formed. The magnetotransport properties of the films, particularly the magnetoresistance, along paths parallel and perpendicular to the track have been extensively investigated and compared to similar data recorded on films grown on bicrystalline STO substrates. Whereas in LSMO a significant low-field tunnel magnetoresistance develops across the artificial interface, in SRO this tunnel contribution is absent. However, a significant high-field magnetoresistance is observed for both metallic and ferromagnetic systems. The results are analysed and discussed within the framework of the current understanding of double exchange and itinerant ferromagnets. Magnetoresistance data for various configurations of the track array are presented

  6. Epitaxially grown strained pentacene thin film on graphene membrane.

    Science.gov (United States)

    Kim, Kwanpyo; Santos, Elton J G; Lee, Tae Hoon; Nishi, Yoshio; Bao, Zhenan

    2015-05-06

    Organic-graphene system has emerged as a new platform for various applications such as flexible organic photovoltaics and organic light emitting diodes. Due to its important implication in charge transport, the study and reliable control of molecular packing structures at the graphene-molecule interface are of great importance for successful incorporation of graphene in related organic devices. Here, an ideal membrane of suspended graphene as a molecular assembly template is utilized to investigate thin-film epitaxial behaviors. Using transmission electron microscopy, two distinct molecular packing structures of pentacene on graphene are found. One observed packing structure is similar to the well-known bulk-phase, which adapts a face-on molecular orientation on graphene substrate. On the other hand, a rare polymorph of pentacene crystal, which shows significant strain along the c-axis, is identified. In particular, the strained film exhibits a specific molecular orientation and a strong azimuthal correlation with underlying graphene. Through ab initio electronic structure calculations, including van der Waals interactions, the unusual polymorph is attributed to the strong graphene-pentacene interaction. The observed strained organic film growth on graphene demonstrates the possibility to tune molecular packing via graphene-molecule interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Effect of extrapolation length on the phase transformation of epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Hu, Z.S.; Tang, M.H.; Wang, J.B.; Zheng, X.J.; Zhou, Y.C.

    2008-01-01

    Effects of extrapolation length on the phase transformation of epitaxial ferroelectric thin films on dissimilar cubic substrates have been studied on the basis of the mean-field Landau-Ginzburg-Devonshire (LGD) thermodynamic theory by taking an uneven distribution of the interior stress with thickness into account. It was found that the polarization of epitaxial ferroelectric thin films is strongly dependent on the extrapolation length of films. The physical origin of the extrapolation length during the phase transformation from paraelectric to ferroelectric was revealed in the case of ferroelectric thin films

  8. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    International Nuclear Information System (INIS)

    Krockenberger, Y.

    2006-01-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  9. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    Energy Technology Data Exchange (ETDEWEB)

    Krockenberger, Y.

    2006-07-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  10. Growth of epitaxial thin films by pulsed laser ablation

    International Nuclear Information System (INIS)

    Lowndes, D.H.

    1992-01-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs

  11. Process for forming epitaxial perovskite thin film layers using halide precursors

    Science.gov (United States)

    Clem, Paul G.; Rodriguez, Mark A.; Voigt, James A.; Ashley, Carol S.

    2001-01-01

    A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

  12. Thickness-modulated anisotropic ferromagnetism in Fe-doped epitaxial HfO2 thin films

    Science.gov (United States)

    Liu, Wenlong; Liu, Ming; Zhang, Ruyi; Ma, Rong; Wang, Hong

    2017-10-01

    Epitaxial tetragonal Fe-doped Hf0.95Fe0.05O2 (FHO) thin films with various thicknesses were deposited on (001)-oriented NdCaAlO4 (NCAO) substrates by using a pulsed laser deposition (PLD) system. The crystal structure and epitaxial nature of the FHO thin films were confirmed by typical x-ray diffraction (XRD) θ-2θ scan and reciprocal space mapping (RSM). The results indicate that two sets of lattice sites exist with two different crystal orientations [(001) and (100)] in the thicker FHO thin films. Further, the intensity of the (100) direction increases with the increase in thicknesses, which should have a significant effect on the anisotropic magnetization of the FHO thin films. Meanwhile, all the FHO thin films possess a tetragonal phase structure. An anisotropy behavior in magnetization has been observed in the FHO thin films. The anisotropic magnetization of the FHO thin films is slowly weakened as the thickness increases. Meanwhile, the saturation magnetization (Ms) of both in-plane and out-of-plane decreases with the increase in the thickness. The change in the anisotropic magnetization and Ms is attributed to the crystal lattice and the variation in the valence of Fe ions. These results indicate that the thickness-modulated anisotropic ferromagnetism of the tetragonal FHO epitaxial thin films is of potential use for the integration of metal-oxide semiconductors with spintronics.

  13. Microstructure of epitaxial YBa2Cu3O7-x thin films grown on LaAlO3 (001)

    International Nuclear Information System (INIS)

    Hsieh, Y.; Siegal, M.P.; Hull, R.; Phillips, J.M.

    1990-01-01

    We report a microstructural investigation of the epitaxial growth of YBa 2 Cu 3 O 7-x (YBCO) thin films on LaAlO 3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c (axis normal to the surface and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35--200 nm thick. In 35 nm YBCO films annealed at 850 degree C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy

  14. Anatase thin film with diverse epitaxial relationship grown on yttrium stabilized zirconia substrate by chemical vapor deposition

    International Nuclear Information System (INIS)

    Miyagi, Takahira; Ogawa, Tomoyuki; Kamei, Masayuki; Wada, Yoshiki; Mitsuhashi, Takefumi; Yamazaki, Atsushi

    2003-01-01

    An anatase epitaxial thin film with diverse epitaxial relationship, YSZ (001) // anatase (001), YSZ (010) // anatase (110), was grown on a single crystalline yttrium stabilized zirconia (YSZ) (001) substrate by metal organic chemical vapor deposition (MOCVD). The full width at half maximum (FWHM) of the (004) reflection of this anatase epitaxial film was 0.4deg, and the photoluminescence of this anatase epitaxial film showed visible emission with broad spectral width and large Stokes shift at room temperature. These results indicate that this anatase epitaxial film possessed almost equal crystalline quality compared with that grown under identical growth conditions on single crystalline SrTiO 3 substrate. (author)

  15. Film-thickness and composition dependence of epitaxial thin-film PZT-based

    NARCIS (Netherlands)

    Nguyen, Duc Minh; Dekkers, Jan M.; Vu, Hung Ngoc; Rijnders, Augustinus J.H.M.

    2013-01-01

    The transverse piezoelectric coefficient e31,f and mass-sensitivity were measured on piezoelectric cantilevers based on epitaxial PZT thin-films with film-thicknesses ranging from 100 to 2000 nm. The highest values of e31,f and mass-sensitivity were observed at a film thickness of 500–750 nm, while

  16. Determination of the Young's modulus of pulsed laser deposited epitaxial PZT thin films

    NARCIS (Netherlands)

    Nazeer, H.; Nguyen, Duc Minh; Woldering, L.A.; Abelmann, Leon; Rijnders, Augustinus J.H.M.; Elwenspoek, Michael Curt

    2011-01-01

    We determined the Young’s modulus of pulsed laser deposited epitaxially grown PbZr0.52Ti0.48O3 (PZT) thin films on microcantilevers by measuring the difference in cantilever resonance frequency before and after deposition. By carefully optimizing the accuracy of this technique, we were able to show

  17. Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

    2012-01-01

    The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies

  18. Molecular beam epitaxy growth of InSb1−xBix thin films

    DEFF Research Database (Denmark)

    Song, Yuxin; Wang, Shumin; Saha Roy, Ivy

    2013-01-01

    Molecular beam epitaxy growth for InSb1−xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology are stu...

  19. Epitaxial growth of "infinite layer” thin films and multilayers by rf magnetron sputtering

    OpenAIRE

    Fàbrega, L.; Koller, E.; Triscone, J. M.; Fischer, Ø.

    2017-01-01

    We report on the preparation and characterization of epitaxial ACuO2 (A = Sr, Ca, Ba) thin films and multilayers with the so- called infinite layer (IL) structure, by rf magnetron sputtering. Films and multilayers without Ba have a remarkable crystal quality, whereas those containing this large ion are often multiphased and unstable. In spite of the excellent crystalline quality of these samples, obtaining thin films having both IL structure and displaying superconducting properties has not s...

  20. High-rate deposition of epitaxial layers for efficient low-temperature thin film epitaxial silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Oberbeck, L.; Schmidt, J.; Wagner, T.A.; Bergmann, R.B. [Stuttgart Univ. (Germany). Inst. of Physical Electronics

    2001-07-01

    Low-temperature deposition of Si for thin-film solar cells has previously been hampered by low deposition rates and low material quality, usually reflected by a low open-circuit voltage of these solar cells. In contrast, ion-assisted deposition produces Si films with a minority-carrier diffusion length of 40 {mu}m, obtained at a record deposition rate of 0.8 {mu}m/min and a deposition temperature of 650{sup o}C with a prebake at 810{sup o}C. A thin-film Si solar cell with a 20-{mu}m-thick epitaxial layer achieves an open-circuit voltage of 622 mV and a conversion efficiency of 12.7% without any light trapping structures and without high-temperature solar cell process steps. (author)

  1. Optimization of BSCF-SDC composite air electrode for intermediate temperature solid oxide electrolyzer cell

    International Nuclear Information System (INIS)

    Heidari, Dorna; Javadpour, Sirus; Chan, Siew Hwa

    2017-01-01

    Highlights: • Effect of BSCF-SDC composite air electrode on SOEC electrochemical performance. • Effects on performance of BSCF-SDC air electrode, fuel humidity and temperature. • Desired IT-SOEC performance by compositing the BSCF air electrode with SDC. - Abstract: Solid oxide electrolyzer cells (SOECs) are devises which recently have attracted lots of attention due to their advantages. Their high operating temperature leads to mechanical compatibility issues such as thermal expansion mismatch between layers of material in the cell. The aim of this study is to mitigate the issue of thermal expansion mismatch between Ba_0_._5Sr_0_._5Co_0_._8Fe_0_._2O_3_−_δ (BSCF) and samaria doped ceria, Sm_0_._2Ce_0_._8O_1_._9 (SDC), enhance the triple-phase boundaries and improve the adhesion of the electrode to the electrolytes, hence improve the cell performance. To make BSCF more thermo-mechanically compatible with the SDC electrolyte, the formation of a composite electrode by introducing SDC as the compositing material is proposed. In this study, 10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%, and 50 wt.% of commercial SDC powder was mixed with BSCF powder, prepared by sol-gel method, to make the composite air electrode. After successfully synthesizing the BSCF-SDC/YSZ-SDC/Ni-YSZ electrolyzer cell, the electrochemical performance was tested for the intermediate-temperature SOEC (IT-SOEC), over the temperature range of 650–800 °C. The microstructure of each sample was studied by field emission electron microscopy (FESEM, JEOL, JSM 6340F) for possible pin holes. The result of this study proves that the sample with 20% SDC-80% BSCF shows the highest performance among the investigated cells.

  2. Zirconia thin films from aqueous precursors: Processing, microstructural development, and epitaxial growth

    International Nuclear Information System (INIS)

    Miller, K.T.

    1991-01-01

    Thin films of ZrO 2 (Y 2 O 3 ) were prepared from aqueous salt precursors by spin coating. Films were pyrolyzed to produce porous polycrystalline thin films of 5-10 nm grain size. Subsequent microstructural development depends greatly upon the nature of the substrate. Upon randomly oriented sapphire, the films initially sintered to full density; further heat treatment and grain growth causes these films to break into interconnected islands and finally isolated particles. Thermodynamic calculations predict that breakup is energetically favorable when the grain-size film-thickness ratio exceeds a critical value. Upon basal-plane-oriented sapphire, grain growth and breakup prefer the (100) oriented grains, presumably because this orientation is a special interface of low energy. The isolated, oriented grains produced by film breakup act as seeds for the growth of newly deposited material. Upon (100) cubic zirconia, true epitaxial films develop. Epitaxial growth was observed for lattice mismatches up to 1.59%. Growth proceeds from a fine epitaxial layer which is produced during the initial stages of heat treatment, consuming the porous polycrystalline material and producing a dense epitaxial thin film whose misfit is accommodated by a combination of film strain and misfit dislocations

  3. The origin of local strain in highly epitaxial oxide thin films.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Chen, Chonglin; Lin, Yuan; Li, Yanrong; Horwitz, J S; Jiang, Jiechao; Meletis, E I; Zhang, Qingyu

    2013-10-31

    The ability to control the microstructures and physical properties of hetero-epitaxial functional oxide thin films and artificial structures is a long-sought goal in functional materials research. Normally, only the lattice misfit between the film and the substrate is considered to govern the physical properties of the epitaxial films. In fact, the mismatch of film unit cell arrangement and the Surface-Step-Terrace (SST) dimension of the substrate, named as "SST residual matching", is another key factor that significantly influence the properties of the epitaxial film. The nature of strong local strain induced from both lattice mismatch and the SST residual matching on ferroelectric (Ba,Sr)TiO3 and ferromagnetic (La,Ca)MnO3 thin films are systematically investigated and it is demonstrated that this combined effect has a dramatic impact on the physical properties of highly epitaxial oxide thin films. A giant anomalous magnetoresistance effect (~10(10)) was achieved from the as-designed vicinal surfaces.

  4. High quality atomically thin PtSe2 films grown by molecular beam epitaxy

    Science.gov (United States)

    Yan, Mingzhe; Wang, Eryin; Zhou, Xue; Zhang, Guangqi; Zhang, Hongyun; Zhang, Kenan; Yao, Wei; Lu, Nianpeng; Yang, Shuzhen; Wu, Shilong; Yoshikawa, Tomoki; Miyamoto, Koji; Okuda, Taichi; Wu, Yang; Yu, Pu; Duan, Wenhui; Zhou, Shuyun

    2017-12-01

    Atomically thin PtSe2 films have attracted extensive research interests for potential applications in high-speed electronics, spintronics and photodetectors. Obtaining high quality thin films with large size and controlled thickness is critical. Here we report the first successful epitaxial growth of high quality PtSe2 films by molecular beam epitaxy. Atomically thin films from 1 ML to 22 ML have been grown and characterized by low-energy electron diffraction, Raman spectroscopy and x-ray photoemission spectroscopy. Moreover, a systematic thickness dependent study of the electronic structure is revealed by angle-resolved photoemission spectroscopy (ARPES), and helical spin texture is revealed by spin-ARPES. Our work provides new opportunities for growing large size single crystalline films to investigate the physical properties and potential applications of PtSe2.

  5. General Top-Down Ion Exchange Process for the Growth of Epitaxial Chalcogenide Thin Films and Devices

    KAUST Repository

    Xia, Chuan; Li, Peng; Li, Jun; Jiang, Qiu; Zhang, Xixiang; Alshareef, Husam N.

    2016-01-01

    ) epitaxial chalcogenide metallic and semiconducting films and (2) free-standing chalcogenide films and (3) completed in situ formation of atomically sharp heterojunctions by selective ion exchange. Epitaxial NiCo2S4 thin films prepared by our process show 115

  6. Laser molecular beam epitaxy of ZnO thin films and heterostructures

    International Nuclear Information System (INIS)

    Opel, Matthias; Geprägs, Stephan; Althammer, Matthias; Brenninger, Thomas; Gross, Rudolf

    2014-01-01

    We report on the growth of epitaxial ZnO thin films and ZnO-based heterostructures on sapphire substrates by laser molecular beam epitaxy (MBE). We first discuss some recent developments in laser-MBE such as flexible ultraviolet laser beam optics, infrared laser heating systems or the use of atomic oxygen and nitrogen sources, and describe the technical realization of our advanced laser-MBE system. Then we describe the optimization of the deposition parameters for ZnO films such as laser fluence and substrate temperature and the use of buffer layers. The detailed structural characterization by x-ray analysis and transmission electron microscopy shows that epitaxial ZnO thin films with high structural quality can be achieved, as demonstrated by a small out-of-plane and in-plane mosaic spread as well as the absence of rotational domains. We also demonstrate the heteroepitaxial growth of ZnO-based multilayers as a prerequisite for spin transport experiments and the realization of spintronic devices. As an example, we show that TiN/Co/ZnO/Ni/Au multilayer stacks can be grown on (0 0 0 1)-oriented sapphire with good structural quality of all layers and well defined in-plane epitaxial relations. (paper)

  7. Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

    Science.gov (United States)

    Meng, Siqin; Yue, Zhenxing; Zhang, Xiaozhi; Li, Longtu

    2014-01-01

    Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

  8. Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Siqin; Yue, Zhenxing, E-mail: yuezhx@tsinghua.edu.cn; Zhang, Xiaozhi; Li, Longtu

    2014-01-30

    Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

  9. Pulsed laser deposition of air-sensitive hydride epitaxial thin films: LiH

    Energy Technology Data Exchange (ETDEWEB)

    Oguchi, Hiroyuki, E-mail: oguchi@nanosys.mech.tohoku.ac.jp [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Micro System Integration Center (muSIC), Tohoku University, Sendai 980-0845 (Japan); Isobe, Shigehito [Creative Research Institution, Hokkaido University, Sapporo 001-0021 (Japan); Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Kuwano, Hiroki [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Shiraki, Susumu; Hitosugi, Taro [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Orimo, Shin-ichi [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2015-09-01

    We report on the epitaxial thin film growth of an air-sensitive hydride, lithium hydride (LiH), using pulsed laser deposition (PLD). We first synthesized a dense LiH target, which is key for PLD growth of high-quality hydride films. Then, we obtained epitaxial thin films of [100]-oriented LiH on a MgO(100) substrate at 250 °C under a hydrogen pressure of 1.3 × 10{sup −2} Pa. Atomic force microscopy revealed that the film demonstrates a Stranski-Krastanov growth mode and that the film with a thickness of ∼10 nm has a good surface flatness, with root-mean-square roughness R{sub RMS} of ∼0.4 nm.

  10. Optical and electro-optic anisotropy of epitaxial PZT thin films

    Science.gov (United States)

    Zhu, Minmin; Du, Zehui; Jing, Lin; Yoong Tok, Alfred Iing; Tong Teo, Edwin Hang

    2015-07-01

    Strong optical and electro-optic (EO) anisotropy has been investigated in ferroelectric Pb(Zr0.48Ti0.52)O3 thin films epitaxially grown on Nb-SrTiO3 (001), (011), and (111) substrates using magnetron sputtering. The refractive index, electro-optic, and ferroelectric properties of the samples demonstrate the significant dependence on the growth orientation. The linear electro-optic coefficients of the (001), (011), and (111)-oriented PZT thin films were 270.8, 198.8, and 125.7 pm/V, respectively. Such remarkable anisotropic EO behaviors have been explained according to the structure correlation between the orientation dependent distribution, spontaneous polarization, epitaxial strain, and domain pattern.

  11. Fluorination of an epitaxial YBaCuO thin film with controlled oxygen vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, C. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Pena, O. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Mokhtari, M. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Thivet, C. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Guilloux-Viry, M. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Perrin, A. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France)); Sergent, M. (Lab. de Chimie du Solide et Inorganique Moleculaire, Univ. de Rennes 1, 35 (France))

    1993-05-10

    An intentionally oxygen-deficient thin film, epitaxially grown in-situ on a (100) MgO substrate by laser ablation at 750 C under a low pressure oxygen atmosphere, has been treated under NF[sub 3] diluted in N[sub 2] at temperatures not exceeding 280 C. During the fluorination process the epitaxy of the thin film is maintained; its Tc onset progressively increases from 54 K up to 85.6 K and the width of the inductive transition is narrow at the end of treatment (1.2 K). These results are discussed and compared to those obtained during the fluorination of oxygen-deficient YBa[sub 2]Cu[sub 3]O[sub x] ceramics. (orig.)

  12. Pulsed laser deposition of air-sensitive hydride epitaxial thin films: LiH

    International Nuclear Information System (INIS)

    Oguchi, Hiroyuki; Isobe, Shigehito; Kuwano, Hiroki; Shiraki, Susumu; Hitosugi, Taro; Orimo, Shin-ichi

    2015-01-01

    We report on the epitaxial thin film growth of an air-sensitive hydride, lithium hydride (LiH), using pulsed laser deposition (PLD). We first synthesized a dense LiH target, which is key for PLD growth of high-quality hydride films. Then, we obtained epitaxial thin films of [100]-oriented LiH on a MgO(100) substrate at 250 °C under a hydrogen pressure of 1.3 × 10 −2 Pa. Atomic force microscopy revealed that the film demonstrates a Stranski-Krastanov growth mode and that the film with a thickness of ∼10 nm has a good surface flatness, with root-mean-square roughness R RMS of ∼0.4 nm

  13. Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Anupam, E-mail: anupam@austin.utexas.edu; Dey, Rik, E-mail: rikdey@utexas.edu; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C.P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

    2017-09-01

    Highlights: • Perpendicular magnetic anisotropy in epitaxial Cr{sub 2}Te{sub 3} has been investigated. • Presence of a relatively strong second order anisotropy contribution is observed. • Magnetization reversal is explained quantitatively using a 1D defect model. • Relative roles of nucleation and pinning in magnetization reversal are discussed. • Domain structures and switching process are visualized by micromagnetic simulation. - Abstract: We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

  14. Domain structure and magnetotransport in epitaxial colossal magnetoresistance thin films

    OpenAIRE

    Suzuki, Yuri; Wu, Yan; Yu, Jun; Rüdiger, Ulrich; Kent, Andrew D.; Nath, Tapan K.; Eom, Chang-Beom

    2000-01-01

    Our studies of compressively strained La0.7 Sr0.3 MnO7 (LSMO) thin films reveal the importance of domain structure and strain effects in the magnetization reversal and magnetotransport. Normal and grazing incidence x-ray diffraction indicate that the compressive strain on these LSMO thin films on (100) LaAlO3 is not completely relaxed up to thicknesses on the order of 1000 Å. The effect of the compressive strain is evident in the shape of the magnetization loops and the magnetotransport measu...

  15. Growth of Sr2CrReO6 epitaxial thin films by pulsed laser deposition

    International Nuclear Information System (INIS)

    Orna, J.; Morellon, L.; Algarabel, P.A.; Pardo, J.A.; Magen, C.; Varela, M.; Pennycook, S.J.; De Teresa, J.M.; Ibarra, M.R.

    2010-01-01

    We report the growth, structural, magnetic, and electrical transport properties of epitaxial Sr 2 CrReO 6 thin films. We have succeeded in depositing films with a high crystallinity and a relatively large cationic order in a narrow window of growth parameters. The epitaxy relationship is Sr 2 CrReO 6 (SCRO) (0 0 1) [1 0 0]-parallel SrTiO 3 (STO) (0 0 1) [1 1 0] as determined by high-resolution X-ray diffraction and scanning transmission electron microscopy (STEM). Typical values of saturation magnetization of M S (300 K)=1 μ B /f.u. and ρ (300 K)=2.8 mΩ cm have been obtained in good agreement with previous published results in sputtered epitaxial thin films. We estimate that the antisite defects concentration in our thin films is of the order of 14%, and the measured Curie temperature is T C =481(2) K. We believe these materials be of interest as electrodes in spintronic devices.

  16. Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering

    KAUST Repository

    Pergolesi, Daniele

    2015-02-01

    Highly textured thin films with small grain boundary regions can be used as model systems to directly measure the bulk conductivity of oxygen ion conducting oxides. Ionic conducting thin films and epitaxial heterostructures are also widely used to probe the effect of strain on the oxygen ion migration in oxide materials. For the purpose of these investigations a good lattice matching between the film and the substrate is required to promote the ordered film growth. Moreover, the substrate should be a good electrical insulator at high temperature to allow a reliable electrical characterization of the deposited film. Here we report the fabrication of an epitaxial heterostructure made with a double buffer layer of BaZrO3 and SrTiO3 grown on MgO substrates that fulfills both requirements. Based on such template platform, highly ordered (001) epitaxially oriented thin films of 15% Sm-doped CeO2 and 8 mol% Y2O3 stabilized ZrO2 are grown. Bulk conductivities as well as activation energies are measured for both materials, confirming the success of the approach. The reported insulating template platform promises potential application also for the electrical characterization of other novel electrolyte materials that still need a thorough understanding of their ionic conductivity.

  17. Preparation of YBa2Cu3O7-δ epitaxial thin films by pulsed ion-beam evaporation

    International Nuclear Information System (INIS)

    Sorasit, S.; Yoshida, G.; Suzuki, T.; Suematsu, H.; Jiang, W.; Yatsui, K.

    2001-01-01

    Thin films of YBa 2 Cu 3 O 7-δ (Y-123) grown epitaxially have been successfully deposited by ion-beam evaporation (IBE). The c-axis oriented YBa 2 Cu 3 O 7-δ thin films were successfully deposited on MgO and SrTiO 3 substrates. The Y-123 thin films which were prepared on the SrTiO 3 substrates were confirmed to be epitaxially grown, by X-ray diffraction analysis. The instantaneous deposition rate of the Y-123 thin films was estimated as high as 4 mm/s. (author)

  18. Quasi van der Waals epitaxy of copper thin film on single-crystal graphene monolayer buffer

    Science.gov (United States)

    Lu, Zonghuan; Sun, Xin; Washington, Morris A.; Lu, Toh-Ming

    2018-03-01

    Quasi van der Waals epitaxial growth of face-centered cubic Cu (~100 nm) thin films on single-crystal monolayer graphene is demonstrated using thermal evaporation at an elevated substrate temperature of 250 °C. The single-crystal graphene was transferred to amorphous (glass) and crystalline (quartz) SiO2 substrates for epitaxy study. Raman analysis showed that the thermal evaporation method had minimal damage to the graphene lattice during the Cu deposition. X-ray diffraction and electron backscatter diffraction analyses revealed that both Cu films are single-crystal with (1 1 1) out-of-plane orientation and in-plane Σ3 twin domains of 60° rotation. The crystallinity of the SiO2 substrates has a negligible effect on the Cu crystal orientation during the epitaxial growth, implying the strong screening effect of graphene. We also demonstrate the epitaxial growth of polycrystalline Cu on a commercial polycrystalline monolayer graphene consisting of two orientation domains offset 30° to each other. It confirms that the crystal orientation of the epitaxial Cu film follows that of graphene, i.e. the Cu film consists of two orientation domains offset 30° to each other when deposited on polycrystalline graphene. Finally, on the contrary to the report in the literature, we show that the direct current and radio frequency flip sputtering method causes significant damage to the graphene lattice during the Cu deposition process, and therefore neither is a suitable method for Cu epitaxial growth on graphene.

  19. Magnetism and deformation of epitaxial Pd and Rh thin films

    Czech Academy of Sciences Publication Activity Database

    Káňa, Tomáš; Hüger, E.; Legut, D.; Čák, M.; Šob, Mojmír

    2016-01-01

    Roč. 93, č. 13 (2016), č. článku Art. number 134422. ISSN 2469-9950 R&D Projects: GA MŠk(CZ) LQ1601; GA ČR(CZ) GA16-24711S Institutional support: RVO:68081723 Keywords : ab initio calculations * magnetism * palladium * rhodium * thin films * deformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  20. Growth of conductive HfO{sub 2-x} thin films by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany); Kleebe, Hans-Joachim [Institut fuer Angewandte Geowissenschaften, TU Darmstadt (Germany)

    2009-07-01

    Thin films of oxygen deficient hafnium oxide were grown on single crystal c-cut and r-cut sapphire substrates by reactive molecular beam epitaxy. The oxidation conditions during growth were varied within a wide range using RF-activated oxygen. Hafnium oxide thin films were characterized using X-ray diffraction, resistivity measurements ({rho}-T) and transmission electron microscopy (TEM). The results show a dramatic increase in conductivity of the deposited oxygen deficient hafnium oxide thin films with decreasing oxidation conditions during growth. The electrical properties of deficient hafnium oxide thin films varied from insulating over semiconducting to conducting. X-ray diffraction data as well as TEM data rule out the possibility of conductivity due to metallic hafnium.

  1. Reversal of lattice, electronic structure, and magnetism in epitaxial SrCoOx thin films

    Science.gov (United States)

    Jeen, H.; Choi, W. S.; Lee, J. H.; Cooper, V. R.; Lee, H. N.; Seo, S. S. A.; Rabe, K. M.

    2014-03-01

    SrCoOx (x = 2.5 - 3.0, SCO) is an ideal material to study the role of oxygen content for electronic structure and magnetism, since SCO has two distinct topotactic phases: the antiferromagnetic insulating brownmillerite SrCoO2.5 and the ferromagnetic metallic perovskite SrCoO3. In this presentation, we report direct observation of a reversible lattice and electronic structure evolution in SrCoOx epitaxial thin films as well as different magnetic and electronic ground states between the topotactic phases.[2] By magnetization measurements, optical absorption, and transport measurements drastically different electronic and magnetic ground states are found in the epitaxially grown SrCoO2.5 and SrCoO3 thin films by pulsed laser epitaxy. First-principles calculations confirm substantial, which originate from the modification in the Co valence states and crystallographic structures. By real-time spectroscopic ellipsometry, the two electronically and magnetically different phases can be reversibly changed by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides. The work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

  2. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films.

    Science.gov (United States)

    Kaspar, Tiffany C; Hong, Seungbum; Bowden, Mark E; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R; Comes, Ryan B; Ramuhalli, Pradeep; Henager, Charles H

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200 °C due to the low Curie temperature of the piezoelectric material. Strengthening the piezoelectric coupling of high-temperature piezoelectric materials, such as La 2 Ti 2 O 7 (LTO), would allow sensors to operate across a broad temperature range. The crystalline orientation and piezoelectric coupling direction of LTO thin films can be controlled by epitaxial matching to SrTiO 3 (001), SrTiO 3 (110), and rutile TiO 2 (110) substrates via pulsed laser deposition. The structure and phase purity of the films are investigated by x-ray diffraction and scanning transmission electron microscopy. Piezoresponse force microscopy is used to measure the in-plane and out-of-plane piezoelectric coupling in the films. The strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO 2 (110) results in epitaxial La 2/3 TiO 3 , an orthorhombic perovskite of interest as a microwave dielectric material and an ion conductor. La 2/3 TiO 3 can be difficult to stabilize in bulk form, and epitaxial stabilization on TiO 2 (110) is a promising route to realize La 2/3 TiO 3 for both fundamental studies and device applications. Overall, these results confirm that control of the crystalline orientation of epitaxial LTO-based materials can govern the resulting functional properties.

  3. Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei, E-mail: weili.unsw@gmail.com; Varlamov, Sergey; Xue, Chaowei

    2014-09-30

    Highlights: • Crystallisation kinetic is used to analyse seed layer surface cleanliness. • Simplified RCA cleaning for the seed layer can shorten the epitaxy annealing duration. • RTA for the seed layer can improve the quality for both seed layer and epi-layer. • Epitaxial poly-Si solar cell performance is improved by RTA treated seed layer. - Abstract: This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, V{sub oc} and J{sub sc} than the one on the seed layer without RTA treatment.

  4. Superconductivity of Rock-Salt Structure LaO Epitaxial Thin Film.

    Science.gov (United States)

    Kaminaga, Kenichi; Oka, Daichi; Hasegawa, Tetsuya; Fukumura, Tomoteru

    2018-06-06

    We report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temperature ( T c ) at around 5 K. This T c is higher than those of other lanthanum monochalcogenides and opposite to their chemical trend: T c = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), respectively. The carrier control resulted in a dome-shaped T c as a function of electron carrier density. In addition, the T c was significantly sensitive to epitaxial strain in spite of the highly symmetric crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors.

  5. Squid measurement of the Verwey transition on epitaxial (1 0 0) magnetite thin films

    International Nuclear Information System (INIS)

    Dediu, V.; Arisi, E.; Bergenti, I.; Riminucci, A.; Solzi, M.; Pernechele, C.; Natali, M.

    2007-01-01

    We report results on epitaxial magnetite (Fe 3 O 4 ) thin films grown by electron beam ablation on (1 0 0) MgAl 2 O 4 substrates. At 120 K magnetite undergoes a structural and electronic transition, the so-called Verwey transition, at which magnetic and conducting properties of the material change. We observed the Verwey transition on epitaxial films with a thickness of 50 nm by comparing zero-field cooling (ZFC) and field cooling (FC) curves measured with a superconducting quantum interference device (SQUID) magnetometer. Observation of the Verwey transition by SQUID measurements in the films is sign of their high crystalline quality. Room temperature ferromagnetism has also been found by magneto-optical Kerr rotation (MOKE) and confirmed by SQUID measurements, with a hysteresis loop showing a coercive field of hundreds of Oe

  6. Magnetic domains in epitaxial (100) Fe thin films

    International Nuclear Information System (INIS)

    Florczak, J.M.; Dahlberg, E.D.; Ryan, P.J.; White, R.M.; Kuznia, J.N.; Wowchak, A.M.; Cohen, P.I.

    1989-01-01

    This paper discusses the investigation of the domain patterns of thin Fe films (10 nm) grown on In x Ga 1 - x As (0.09< x<0.25)/GaAs substrates by use of Kerr microscopy. For this investigation, two types of InGaAs buffer layers were prepared. One consisted of a single, thick InGaAs layer and the second composed of an InGaAs strained layer superlattice. Both were grown on (100) GaAs substrates. The study showed that many of the domain walls were approximately parallel to the easy axis of Fe for those films grown on the low x alloy, e.g. x = 0.1, InGaAs buffer layers

  7. The liquid phase epitaxy method for the construction of oriented ZIF-8 thin films with controlled growth on functionalized surfaces

    KAUST Repository

    Shekhah, Osama; Eddaoudi, Mohamed

    2013-01-01

    Highly-oriented ZIF-8 thin films with controllable thickness were grown on an -OH-functionalized Au substrate using the liquid phase epitaxy method at room temperature, as evidenced by SEM and PXRD. The adsorption-desorption properties of the resulting ZIF-8 thin film were investigated for various VOCs using the QCM technique. © The Royal Society of Chemistry 2013.

  8. Epitaxial growth of thin single-crystals and their quality study by Rutherford scattering in channeling conditions

    International Nuclear Information System (INIS)

    Kirsch, Robert.

    1975-01-01

    Some aspects of thin crystalline layers are reminded: vacuum deposition, epitaxial growth, annealing and interdiffusion ion channeling and scattering of 1-2MeV helium ions are used to study the crystalline quality, the annealing effects and in some cases the interdiffusion in epitaxial multilayers of silver, copper gold and nickel. Thin single-crystals of gold and nickel oriented (III) plan parallel to the surface were obtained by successive epitaxial growth from muscovite mica clivages. The mounting techniques of single crystalline, self-supporting, 300 to 1200 Angstroems thick, gold and nickel targets of 3mm diameter are described. The gold single-crystals have dislocation densities of 10 8 cm -2 and the various epitaxial layers are obtained without twinning [fr

  9. YCo5±x thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Sharath, S. U.; Radulov, I.; Alff, L.

    2017-06-01

    The synthesis conditions of buffer-free (00l) oriented YCo5 and Y2Co17 thin films onto Al2O3 (0001) substrates have been explored by molecular beam epitaxy (MBE). The manipulation of the ratio of individual atomic beams of Yttrium, Y and Cobalt, Co, as well as growth rate variations allows establishing a thin film phase diagram. Highly textured YCo5±x thin films were stabilized with saturation magnetization of 517 emu/cm3 (0.517 MA/m), coercivity of 4 kOe (0.4 T), and anisotropy constant, K1, equal to 5.34 ×106 erg/cm3 (0.53 MJ/m3). These magnetic parameters and the perpendicular anisotropy obtained without additional underlayers make the material system interesting for application in magnetic recording devices.

  10. Thin film phase diagram of iron nitrides grown by molecular beam epitaxy

    Science.gov (United States)

    Gölden, D.; Hildebrandt, E.; Alff, L.

    2017-01-01

    A low-temperature thin film phase diagram of the iron nitride system is established for the case of thin films grown by molecular beam epitaxy and nitrided by a nitrogen radical source. A fine-tuning of the nitridation conditions allows for growth of α ‧ -Fe8Nx with increasing c / a -ratio and magnetic anisotropy with increasing x until almost phase pure α ‧ -Fe8N1 thin films are obtained. A further increase of nitrogen content below the phase decomposition temperature of α ‧ -Fe8N (180 °C) leads to a mixture of several phases that is also affected by the choice of substrate material and symmetry. At higher temperatures (350 °C), phase pure γ ‧ -Fe4N is the most stable phase.

  11. Epitaxial stabilization of ultra thin films of electron doped manganites

    Energy Technology Data Exchange (ETDEWEB)

    Middey, S., E-mail: smiddey@uark.edu; Kareev, M.; Meyers, D.; Liu, X.; Cao, Y.; Tripathi, S.; Chakhalian, J. [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Yazici, D.; Maple, M. B. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Ryan, P. J.; Freeland, J. W. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2014-05-19

    Ultra-thin films of the electron doped manganite La{sub 0.8}Ce{sub 0.2}MnO{sub 3} were grown in a layer-by-layer growth mode on SrTiO{sub 3} (001) substrates by pulsed laser interval deposition. High structural quality and surface morphology were confirmed by a combination of synchrotron based x-ray diffraction and atomic force microscopy. Resonant X-ray absorption spectroscopy measurements confirm the presence of Ce{sup 4+} and Mn{sup 2+} ions. In addition, the electron doping signature was corroborated by Hall effect measurements. All grown films show a ferromagnetic ground state as revealed by both dc magnetization and x-ray magnetic circular dichroism measurements and remain insulating contrary to earlier reports of a metal-insulator transition. Our results hint at the possibility of electron-hole asymmetry in the colossal magnetoresistive manganite phase diagram akin to the high-T{sub c} cuprates.

  12. Epitaxial growth of Fe-based superconductor thin films

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Sven; Haenisch, Jens; Holzapfel, Bernhard [Institut fuer Technische Physik, Karlsruher Institut fuer Technologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2016-07-01

    The Fe-based superconductors (FBS), discovered in 2008, are not only interesting for possible applications due to their large upper critical fields and low anisotropies, but also for basic understanding of unconventional superconductivity. With their properties, they constitute a link between the classic low-T{sub c} superconductors (low anisotropies, low thermal fluctuations, s-wave type symmetry) and the oxocuprates (T{sub c} up to 55 K, large H{sub c2}, unconventional pairing). Their multi-band nature reminds of MgB{sub 2}. We prepare thin films of FBS in the so called 122 family, namely Co- and P-doped BaFe{sub 2}As{sub 2} to investigate application relevant properties, such as critical current density J{sub c}, by pulsed laser deposition using a frequency-tripled Nd:YAG laser (λ = 355 nm). Microstructure and chemical composition will be investigated by XRD, AFM and SEM, and electrical transport using a 14 T PPMS. The results are compared to literature data on films grown at different wavelengths.

  13. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose; Ahn, Sung-Jin; Crumlin, Ethan; Orikasa, Yuki; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

    2010-01-01

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  14. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose

    2010-06-22

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  15. From epitaxial growth of ferrite thin films to spin-polarized tunnelling

    International Nuclear Information System (INIS)

    Moussy, Jean-Baptiste

    2013-01-01

    This paper presents a review of the research which is focused on ferrite thin films for spintronics. First, I will describe the potential of ferrite layers for the generation of spin-polarized currents. In the second step, the structural and chemical properties of epitaxial thin films and ferrite-based tunnel junctions will be presented. Particular attention will be given to ferrite systems grown by oxygen-assisted molecular beam epitaxy. The analysis of the structure and chemistry close to the interfaces, a key-point for understanding the spin-polarized tunnelling measurements, will be detailed. In the third part, the magnetic and magneto-transport properties of magnetite (Fe 3 O 4 ) thin films as a function of structural defects such as the antiphase boundaries will be explained. The spin-polarization measurements (spin-resolved photoemission, tunnel magnetoresistance) on this oxide predicted to be half-metallic will be discussed. Fourth, the potential of magnetic tunnel barriers, such as CoFe 2 O 4 , NiFe 2 O 4 or MnFe 2 O 4 , whose insulating behaviour and the high Curie temperatures make it exciting candidates for spin filtering at room temperature will be described. Spin-polarized tunnelling experiments, involving either Meservey–Tedrow or tunnel magnetoresistance measurements, will reveal significant spin-polarizations of the tunnelling current at low temperatures but also at room temperatures. Finally, I will mention a few perspectives with ferrite-based heterostructures. (topical review)

  16. Bulk photovoltaic effect in epitaxial (K, Nb) substituted BiFeO3 thin films

    Science.gov (United States)

    Agarwal, Radhe; Zheng, Fan; Sharma, Yogesh; Hong, Seungbum; Rappe, Andrew; Katiyar, Ram

    We studied the bulk photovoltaic effect in epitaxial (K, Nb) modified BiFeO3 (BKFNO) thin films using theoretical and experimental methods. Epitaxial BKFNO thin films were grown by pulsed laser deposition (PLD). First, we have performed first principles density function theory (DFT) using DFT +U method to calculate electronic band structure, including Hubbard-Ueff (Ueff =U-J) correction into Hamiltonian. The electronic band structure calculations showed a direct band gap at 1.9 eV and a defect level at 1.7 eV (in a 40 atom BKFNO supercell), sufficiently lower in comparison to the experimentally observed values. Furthermore, the piezoforce microscopy (PFM) measurements indicated the presence of striped polydomains in BKFNO thin films. Angle-resolved PFM measurements were also performed to find domain orientation and net polarization directions in these films. The experimental studies of photovoltaic effect in BKNFO films showed a short circuit current of 59 micro amp/cm2 and open circuit voltage of 0.78 V. We compared our experimental results with first principles shift current theory calculations of bulk photovoltaic effect (BPVE).The synergy between theory and experimental results provided a realization of significant role of BPVE in order to understand the photovoltaic mechanism in ferroelectrics.

  17. Synchrotron X-ray studies of epitaxial ferroelectric thin films and nanostructures

    Science.gov (United States)

    Klug, Jeffrey A.

    The study of ferroelectric thin films is a field of considerable scientific and technological interest. In this dissertation synchrotron x-ray techniques were applied to examine the effects of lateral confinement and epitaxial strain in ferroelectric thin films and nanostructures. Three materials systems were investigated: laterally confined epitaxial BiFeO3 nanostructures on SrTiO3 (001), ultra-thin commensurate SrTiO 3 films on Si (001), and coherently strained films of BaTiO3 on DyScO3 (110). Epitaxial films of BiFeO3 were deposited by radio frequency magnetron sputtering on SrRuO3 coated SrTiO 3 (001) substrates. Laterally confined nanostructures were fabricated using focused ion-beam processing and subsequently characterized with focused beam x-ray nanodiffraction measurements with unprecedented spatial resolution. Results from a series of rectangular nanostructures with lateral dimensions between 500 nm and 1 mum and a comparably-sized region of the unpatterned BiFeO3 film revealed qualitatively similar distributions of local strain and lattice rotation with a 2-3 times larger magnitude of variation observed in those of the nanostructures compared to the unpatterned film. This indicates that lateral confinement leads to enhanced variation in the local strain and lattice rotation fields in epitaxial BiFeO3 nanostructures. A commensurate 2 nm thick film of SrTiO3 on Si was characterized by the x-ray standing wave (XSW) technique to determine the Sr and Ti cation positions in the strained unit cell in order to verify strain-induced ferroelectricity in SrTiO3/Si. A Si (004) XSW measurement at 10°C indicated that the average Ti displacement from the midpoint between Sr planes was consistent in magnitude to that predicted by a density functional theory (DFT) calculated ferroelectric structure. The Ti displacement determined from a 35°C measurement better matched a DFT-predicted nonpolar structure. The thin film extension of the XSW technique was employed to

  18. Irradiation induced improvement in crystallinity of epitaxially grown Ag thin films on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Takahiro, Katsumi; Nagata, Shinji; Yamaguchi, Sadae [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    1997-03-01

    We report the improvement in crystallinity of epitaxially grown Ag films on Si(100) substrates with ion irradiation. The irradiation of 0.5 MeV Si ions to 2x10{sup 16}/cm{sup 2} at 200degC, for example, reduces the channeling minimum yield from 60% to 6% at Ag surface. The improvement originates from the decrease of mosaic spread in the Ag thin film. In our experiments, ion energy, ion species and irradiation temperature have been varied. The better crystallinity is obtained as the higher concentration of defect is generated. The mechanism involved in the irradiation induced improvement is discussed. (author)

  19. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Zhou Hao; Hong Jiawang; Zhang Yihui; Li Faxin; Pei Yongmao; Fang Daining

    2012-01-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO 3 thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  20. Optimized electrode coverage of membrane actuators based on epitaxial PZT thin films

    International Nuclear Information System (INIS)

    Nguyen, M D; Dekkers, M; Blank, D H A; Rijnders, G; Nazeer, H

    2013-01-01

    This research presents an optimization of piezoelectric membrane actuators by maximizing the actuator displacement. Membrane actuators based on epitaxial Pb(Zr,Ti)O 3 thin films grown on all-oxide electrodes and buffer layers using silicon technology were fabricated. Electrode coverage was found to be an important factor in the actuation displacement of the piezoelectric membranes. The optimum electrode coverage for maximum displacement was theoretically determined to be 39%, which is in good agreement with the experimental results. Dependences of membrane displacement and optimum electrode coverage on membrane diameter and PZT-film/Si-device-layer thickness ratio have also been investigated. (paper)

  1. Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2012-04-18

    The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies that influence the effective mass of carriers in SLTO films can be tuned by varying the laser energy. The highest power factor of 0.433 W K−1 m−1 has been achieved at 636 K for a filmdeposited using the highest laser fluence of 7 J cm−2 pulse−1.

  2. Mechanical properties of metal-organic frameworks: An indentation study on epitaxial thin films

    Science.gov (United States)

    Bundschuh, S.; Kraft, O.; Arslan, H. K.; Gliemann, H.; Weidler, P. G.; Wöll, C.

    2012-09-01

    We have determined the hardness and Young's modulus of a highly porous metal-organic framework (MOF) using a standard nanoindentation technique. Despite the very low density of these films, 1.22 g cm-3, Young's modulus reaches values of almost 10 GPa for HKUST-1, demonstrating that this porous coordination polymer is substantially stiffer than normal polymers. This progress in characterizing mechanical properties of MOFs has been made possible by the use of high quality, oriented thin films grown using liquid phase epitaxy on modified Au substrates.

  3. Oxygen pressure-tuned epitaxy and magnetic properties of magnetite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junran [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu, Wenqing [York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom); Zhang, Minhao; Zhang, Xiaoqian; Niu, Wei; Gao, Ming [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wang, Xuefeng, E-mail: xfwang@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Du, Jun [School of Physics, Nanjing University, Nanjing 210093 (China); Zhang, Rong [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Yongbing, E-mail: ybxu@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom)

    2017-06-15

    Highlights: • Quasi-2D Fe{sub 3}O{sub 4} films were obtained by PLD. • RHEED under different oxygen pressure were observed. • Influence of oxygen pressure on Fe{sub 3}O{sub 4} films were investigated. • Epitaxy and magnetic properties were tuned by oxygen pressure. • The ratio of Fe{sup 2+}/Fe{sup 3+} fitted by XPS is the tuned factor of M{sub s}. - Abstract: Quasi-two-dimensional magnetite epitaxial thin films have been synthesized by pulsed laser deposition technique at various oxygen pressures. The saturation magnetizations of the magnetite films were found to decrease from 425 emu/cm{sup 3}, which is close to the bulk value, to 175 emu/cm{sup 3} as the growth atmospheres varying from high vacuum (∼1 × 10{sup −8} mbar) to oxygen pressure of 1 × 10{sup −3} mbar. The ratio of the Fe{sup 3+} to Fe{sup 2+} increases from 2 to 2.7 as oxygen pressure increasing shown by XPS fitting, which weakens the net magnetic moment generated by Fe{sup 2+} at octahedral sites as the spins of the Fe{sup 3+} ions at octahedral and tetrahedral sites are aligned in antiparallel. The results offer direct experimental evidence of the influence to the Fe{sup 3+}/Fe{sup 2+} ratio and the magnetic moment in magnetite epitaxy films by oxygen pressure, which is significant for spintronic applications.

  4. Epitaxial Growth of Permalloy Thin Films on MgO Single-Crystal Substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Matsubara, Katsuki; Futamoto, Masaaki; Kirino, Fumiyoshi

    2011-01-01

    Permalloy (Py: Ni - 20 at. % Fe) thin films were prepared on MgO single-crystal substrates of (100), (110), and (111) orientations by molecular beam epitaxy. Py crystals consisting of fcc(100) and hcp(112-bar 0) orientations epitaxially nucleate on MgO(100) substrates. With increasing the substrate temperature, the volume ratio of fcc(100) to hcp(112-bar 0) crystal increases. The metastable hcp(112-bar 0) structure transforms into more stable fcc(110) structure with increasing the film thickness. Py(110) fcc single-crystal films are obtained on MgO(110) substrates, whereas Py films epitaxially grow on MgO(111) substrates with two types of fcc(111) variants whose orientations are rotated around the film normal by 180 deg. each other. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of these fcc-Py films agree within ±0.4% with the values of bulk fcc-Py crystal, suggesting that the strains in the films are very small. High-resolution transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the films around the Py/MgO(100) and the Py/MgO(110) interfaces to reduce the lattice mismatches. The magnetic properties are considered to be reflecting the magnetocrystalline anisotropies of bulk fcc-Py and/or metastable hcp-Py crystals and the shape anisotropy caused by the surface undulations.

  5. Epitaxial Growth of Permalloy Thin Films on MgO Single-Crystal Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Matsubara, Katsuki; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2011-07-06

    Permalloy (Py: Ni - 20 at. % Fe) thin films were prepared on MgO single-crystal substrates of (100), (110), and (111) orientations by molecular beam epitaxy. Py crystals consisting of fcc(100) and hcp(112-bar 0) orientations epitaxially nucleate on MgO(100) substrates. With increasing the substrate temperature, the volume ratio of fcc(100) to hcp(112-bar 0) crystal increases. The metastable hcp(112-bar 0) structure transforms into more stable fcc(110) structure with increasing the film thickness. Py(110){sub fcc} single-crystal films are obtained on MgO(110) substrates, whereas Py films epitaxially grow on MgO(111) substrates with two types of fcc(111) variants whose orientations are rotated around the film normal by 180 deg. each other. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of these fcc-Py films agree within {+-}0.4% with the values of bulk fcc-Py crystal, suggesting that the strains in the films are very small. High-resolution transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the films around the Py/MgO(100) and the Py/MgO(110) interfaces to reduce the lattice mismatches. The magnetic properties are considered to be reflecting the magnetocrystalline anisotropies of bulk fcc-Py and/or metastable hcp-Py crystals and the shape anisotropy caused by the surface undulations.

  6. BiFeO3 epitaxial thin films and devices: past, present and future

    Science.gov (United States)

    Sando, D.; Barthélémy, A.; Bibes, M.

    2014-11-01

    The celebrated renaissance of the multiferroics family over the past ten years has also been that of its most paradigmatic member, bismuth ferrite (BiFeO3). Known since the 1960s to be a high temperature antiferromagnet and since the 1970s to be ferroelectric, BiFeO3 only had its bulk ferroic properties clarified in the mid-2000s. It is however the fabrication of BiFeO3 thin films and their integration into epitaxial oxide heterostructures that have fully revealed its extraordinarily broad palette of functionalities. Here we review the first decade of research on BiFeO3 films, restricting ourselves to epitaxial structures. We discuss how thickness and epitaxial strain influence not only the unit cell parameters, but also the crystal structure, illustrated for instance by the discovery of the so-called T-like phase of BiFeO3. We then present its ferroelectric and piezoelectric properties and their evolution near morphotropic phase boundaries. Magnetic properties and their modification by thickness and strain effects, as well as optical parameters, are covered. Finally, we highlight various types of devices based on BiFeO3 in electronics, spintronics, and optics, and provide perspectives for the development of further multifunctional devices for information technology and energy harvesting.

  7. Growth of HfO{sub x} thin films by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU Darmstadt (Germany)

    2008-07-01

    Thin films of hafnium oxide were grown on single crystal r-cut and c-cut sapphire by reactive molecular beam epitaxy. The conditions for the growth of single oriented hafnium oxide thin films have been established. Hafnium oxide thin films were characterized by X-ray diffraction and optical absorption measurements. It was found that hafnium oxide thin films grown on r-cut sapphire were (00l) oriented whereas, on c-cut sapphire, hafnium oxide films showed different orientations depending on the growth temperature and oxidation conditions. The hafnium oxide films grown at higher temperature and under strong oxidation conditions yielded (001) oriented films on c-cut sapphire whereas slightly weaker oxidation condition leads to (111) oriented hafnium oxide films. The bandgap deducted from optical absorption measurement carried out on hafnium oxide films grown under optimized conditions agreed well with the values reported in literature. A range of oxygen deficient thin films of hafnium oxide were also grown on single crystal sapphire substrates in order to investigate the effect of oxygen vacancies on dielectric properties of hafnium oxide. The oxygen deficient thin films of hafnium oxide show a decrease in bandgap with increase in oxygen deficiency.

  8. Ion Beam Assisted Deposition of Thin Epitaxial GaN Films.

    Science.gov (United States)

    Rauschenbach, Bernd; Lotnyk, Andriy; Neumann, Lena; Poppitz, David; Gerlach, Jürgen W

    2017-06-23

    The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy GaN thin films on (0001)-oriented 6H-SiC substrates at 700 °C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality.

  9. Epitaxially influenced boundary layer model for size effect in thin metallic films

    International Nuclear Information System (INIS)

    Bazant, Zdenek P.; Guo Zaoyang; Espinosa, Horacio D.; Zhu Yong; Peng Bei

    2005-01-01

    It is shown that the size effect recently observed by Espinosa et al., [J. Mech. Phys. Solids51, 47 (2003)] in pure tension tests on free thin metallic films can be explained by the existence of a boundary layer of fixed thickness, located at the surface of the film that was attached onto the substrate during deposition. The boundary layer is influenced by the epitaxial effects of crystal growth on the dislocation density and texture (manifested by prevalent crystal plane orientations). This influence is assumed to cause significantly elevated yield strength. Furthermore, the observed gradual postpeak softening, along with its size independence, which is observed in short film strips subjected to pure tension, is explained by slip localization, originating at notch-like defects, and by damage, which can propagate in a stable manner when the film strip under pure tension is sufficiently thin and short. For general applications, the present epitaxially influenced boundary layer model may be combined with the classical strain-gradient plasticity proposed by Gao et al., [J. Mech. Phys. Solids 47, 1239 (1999)], and it is shown that this combination is necessary to fit the test data on both pure tension and bending of thin films by one and the same theory. To deal with films having different crystal grain sizes, the Hall-Petch relation for the yield strength dependence on the grain size needs to be incorporated into the combined theory. For very thin films, in which a flattened grain fills the whole film thickness, the Hall-Petch relation needs a cutoff, and the asymptotic increase of yield strength with diminishing film thickness is then described by the extension of Nix's model of misfit dislocations by Zhang and Zhou [J. Adv. Mater. 38, 51 (2002)]. The final result is a proposal of a general theory for strength, size effect, hardening, and softening of thin metallic films

  10. Epitaxially influenced boundary layer model for size effect in thin metallic films

    Science.gov (United States)

    Bažant, Zdeněk P.; Guo, Zaoyang; Espinosa, Horacio D.; Zhu, Yong; Peng, Bei

    2005-04-01

    It is shown that the size effect recently observed by Espinosa et al., [J. Mech. Phys. Solids51, 47 (2003)] in pure tension tests on free thin metallic films can be explained by the existence of a boundary layer of fixed thickness, located at the surface of the film that was attached onto the substrate during deposition. The boundary layer is influenced by the epitaxial effects of crystal growth on the dislocation density and texture (manifested by prevalent crystal plane orientations). This influence is assumed to cause significantly elevated yield strength. Furthermore, the observed gradual postpeak softening, along with its size independence, which is observed in short film strips subjected to pure tension, is explained by slip localization, originating at notch-like defects, and by damage, which can propagate in a stable manner when the film strip under pure tension is sufficiently thin and short. For general applications, the present epitaxially influenced boundary layer model may be combined with the classical strain-gradient plasticity proposed by Gao et al., [J. Mech. Phys. Solids 47, 1239 (1999)], and it is shown that this combination is necessary to fit the test data on both pure tension and bending of thin films by one and the same theory. To deal with films having different crystal grain sizes, the Hall-Petch relation for the yield strength dependence on the grain size needs to be incorporated into the combined theory. For very thin films, in which a flattened grain fills the whole film thickness, the Hall-Petch relation needs a cutoff, and the asymptotic increase of yield strength with diminishing film thickness is then described by the extension of Nix's model of misfit dislocations by Zhang and Zhou [J. Adv. Mater. 38, 51 (2002)]. The final result is a proposal of a general theory for strength, size effect, hardening, and softening of thin metallic films.

  11. Strain dependent microstructural modifications of BiCrO{sub 3} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, Vijayanandhini, E-mail: kvnandhini@gmail.com [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Arredondo, Miryam; Johann, Florian; Hesse, Dietrich [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Labrugere, Christine [CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); CeCaMA, University of Bordeaux, ICMCB, F-33600 Pessac (France); Maglione, Mario [CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Vrejoiu, Ionela [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany)

    2013-10-31

    Strain-dependent microstructural modifications were observed in epitaxial BiCrO{sub 3} (BCO) thin films fabricated on single crystalline substrates, utilizing pulsed laser deposition. The following conditions were employed to modify the epitaxial-strain: (i) in-plane tensile strain, BCO{sub STO} [BCO grown on buffered SrTiO{sub 3} (001)] and in-plane compressive strain, BCO{sub NGO} [BCO grown on buffered NdGaO{sub 3} (110)] and (ii) varying BCO film thickness. A combination of techniques like X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (TEM) was used to analyse the epitaxial growth quality and the microstructure of BCO. Our studies revealed that in the case of BCO{sub STO}, a coherent interface with homogeneous orthorhombic phase is obtained only for BCO film with thicknesses, d < 50 nm. All the BCO{sub STO} films with d ≥ 50 nm were found to be strain-relaxed with an orthorhombic phase showing 1/2 <100> and 1/4 <101> satellite reflections, the latter oriented at 45° from orthorhombic diffraction spots. High angle annular dark field scanning TEM of these films strongly suggested that the satellite reflections, 1/2 <100> and 1/4 <101>, originate from the atomic stacking sequence changes (or “modulated structure”) as reported for polytypes, without altering the chemical composition. The unaltered stoichiometry was confirmed by estimating both valency of Bi and Cr cations by surface and in-depth XPS analysis as well as the stoichiometric ratio (1 Bi:1 Cr) using scanning TEM–energy dispersive X-ray analysis. In contrast, compressively strained BCO{sub NGO} films exhibited monoclinic symmetry without any structural modulations or interfacial defects, up to d ∼ 200 nm. Our results indicate that both the substrate-induced in-plane epitaxial strain and the BCO film thickness are the crucial parameters to stabilise a homogeneous BCO phase in an epitaxially grown film. - Highlights: • Phase pure

  12. Epitaxial growth and characterization of CoO/Fe(001) thin film layered structures

    International Nuclear Information System (INIS)

    Brambilla, A.; Sessi, P.; Cantoni, M.; Duo, L.; Finazzi, M.; Ciccacci, F.

    2008-01-01

    By means of X-ray photoemission spectroscopy and low energy electron diffraction, we show that it is possible to grow good quality thin epitaxial CoO films on Fe(001) substrates, through deposition in oxygen atmosphere. In particular, the composition and the structure of CoO(001)/Fe(001) bilayer systems and Fe(001)/CoO(001)/Fe(001) trilayer systems have been investigated by monitoring the evolution of the chemical interactions at the interfaces as a function of CoO thickness and growth temperature. We observe the presence of Fe oxides at the CoO/Fe interface and of a thin layer of metallic cobalt at the upper Fe/CoO interface of trilayer systems

  13. Strain Induced Magnetism in SrRuO3 Epitaxial Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Grutter, A.; Wong, F.; Arenholz, E.; Liberati, M.; Suzuki, Y.

    2010-01-10

    Epitaxial SrRuO{sub 3} thin films were grown on SrTiO{sub 3}, (LaAlO{sub 3}){sub 0.3}(SrAlO{sub 3}){sub 0.7} and LaAlO{sub 3} substrates inducing different biaxial compressive strains. Coherently strained SrRuO{sub 3} films exhibit enhanced magnetization compared to previously reported bulk and thin film values of 1.1-1.6 {micro}{sub B} per formula unit. A comparison of (001) and (110) SrRuO{sub 3} films on each substrate indicates that films on (110) oriented have consistently higher saturated moments than corresponding (001) films. These observations indicate the importance of lattice distortions in controlling the magnetic ground state in this transitional metal oxide.

  14. Molecular-Beam Epitaxially Grown MgB2 Thin Films and Superconducting Tunnel Junctions

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Laloë

    2011-01-01

    Full Text Available Since the discovery of its superconducting properties in 2001, magnesium diboride has generated terrific scientific and engineering research interest around the world. With a of 39 K and two superconducting gaps, MgB2 has great promise from the fundamental point of view, as well as immediate applications. Several techniques for thin film deposition and heterojunction formation have been established, each with its own advantages and drawbacks. Here, we will present a brief overview of research based on MgB2 thin films grown by molecular beam epitaxy coevaporation of Mg and B. The films are smooth and highly crystalline, and the technique allows for virtually any heterostructure to be formed, including all-MgB2 tunnel junctions. Such devices have been characterized, with both quasiparticle and Josephson tunneling reported. MgB2 remains a material of great potential for a multitude of further characterization and exploration research projects and applications.

  15. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    KAUST Repository

    Sarath Kumar, S. R.

    2012-02-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258–133 S cm−1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8–3.2 me ), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  16. MnSi nanostructures obtained from epitaxially grown thin films: magnetotransport and Hall effect

    Science.gov (United States)

    Schroeter, D.; Steinki, N.; Schilling, M.; Fernández Scarioni, A.; Krzysteczko, P.; Dziomba, T.; Schumacher, H. W.; Menzel, D.; Süllow, S.

    2018-06-01

    We present a comparative study of the (magneto)transport properties, including Hall effect, of bulk, epitaxially grown thin film and nanostructured MnSi. In order to set our results in relation to published data we extensively characterize our materials, this way establishing a comparatively good sample quality. Our analysis reveals that in particular for thin film and nanostructured material, there are extrinsic and intrinsic contributions to the electronic transport properties, which by modeling the data we separate out. Finally, we discuss our Hall effect data of nanostructured MnSi under consideration of the extrinsic contributions and with respect to the question of the detection of a topological Hall effect in a skyrmionic lattice.

  17. Tuning of Transport and Magnetic Properties in Epitaxial LaMnO3+δ Thin Films

    Directory of Open Access Journals (Sweden)

    J. Chen

    2014-01-01

    Full Text Available The effect of compressive strain on the transport and magnetic properties of epitaxial LaMnO3+δ thin films has been investigated. It is found that the transport and magnetic properties of the LaMnO3+δ thin films grown on the LaAlO3 substrates can be tuned by the compressive strain through varying film thickness. And the insulator-metal transition, charge/orbital ordering transition, and paramagnetic-ferromagnetic transition are suppressed by the compressive strain. Consequently, the related electronic and magnetic transition temperatures decrease with an increase in the compressive strain. The present results can be explained by the strain-controlled lattice deformation and the consequent orbital occupation. It indicates that the lattice degree of freedom is crucial for understanding the transport and magnetic properties of the strongly correlated LaMnO3+δ.

  18. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    KAUST Repository

    Sarath Kumar, S. R.; Abutaha, Anas I.; Hedhili, Mohamed N.; Alshareef, Husam N.

    2012-01-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258–133 S cm−1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8–3.2 me ), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  19. Diamagnetism to ferromagnetism in Sr-substituted epitaxial BaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu; Prater, John T. [Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Punugupati, Sandhyarani; Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2016-04-04

    We report on the ferromagnetic-like behavior in otherwise diamagnetic BaTiO{sub 3} (BTO) thin films upon doping with non-magnetic element Sr having the composition Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} (BST). The epitaxial integration of BST (∼800 nm) thick films on Si (100) substrate was achieved using MgO (40 nm) and TiN (20 nm) as buffer layers to prepare BST/MgO/TiN/Si (100) heterostructure by pulsed laser deposition. The c-axis oriented and cube-on-cube epitaxial BST is formed on Si (100) as evidenced by the in-plane and out-of-plane X-ray diffraction. All the deposited films are relaxed through domain matching epitaxy paradigm as observed from X-ray diffraction pattern and A{sub 1}TO{sub 3} mode (at 521.27 cm{sup −1}) of Raman spectra. As-deposited BST thin films reveal ferromagnetic-like properties, which persist up to 400 K. The magnetization decreases two-fold upon oxygen annealing. In contrast, as-deposited un-doped BTO films show diamagnetism. Electron spin resonance measurements reveal no evidence of external magnetic impurities. XRD and X-ray photoelectron spectroscopy spectra show significant changes influenced by Sr doping in BTO. The ferromagnetic-like behavior in BST could be due to the trapped electron donors from oxygen vacancies resulting from Sr-doping.

  20. Preparation and characterization of epitaxially grown unsupported yttria-stabilized zirconia (YSZ) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Götsch, Thomas; Mayr, Lukas [Institute of Physical Chemistry, Universität Innsbruck, A-6020 Innsbruck (Austria); Stöger-Pollach, Michael [University Service Center for Transmission Electron Microscopy (USTEM), Vienna University of Technology, A-1040 Vienna (Austria); Klötzer, Bernhard [Institute of Physical Chemistry, Universität Innsbruck, A-6020 Innsbruck (Austria); Penner, Simon, E-mail: simon.penner@uibk.ac.at [Institute of Physical Chemistry, Universität Innsbruck, A-6020 Innsbruck (Austria)

    2015-03-15

    Highlights: • Preparation of unsupported yttrium-stabilized zirconia films. • Control of ordering and epitaxy by temperature of deposition template. • Adjustment of film defectivity by deposition and post-oxidation temperature. • Reproducibility of target stoichiometry in the deposited films. • Lateral and vertical chemical homogeneity. - Abstract: Epitaxially grown, chemically homogeneous yttria-stabilized zirconia thin films (“YSZ”, 8 mol% Y{sub 2}O{sub 3}) are prepared by direct-current sputtering onto a single-crystalline NaCl(0 0 1) template at substrate temperatures ≥493 K, resulting in unsupported YSZ films after floating off NaCl in water. A combined methodological approach by dedicated (surface science) analytical characterization tools (transmission electron microscopy and diffraction, atomic force microscopy, angle-resolved X-ray photoelectron spectroscopy) reveals that the film grows mainly in a [0 0 1] zone axis and no Y-enrichment in surface or bulk regions takes place. In fact, the Y-content of the sputter target is preserved in the thin films. Analysis of the plasmon region in EEL spectra indicates a defective nature of the as-deposited films, which can be suppressed by post-deposition oxidation at 1073 K. This, however, induces considerable sintering, as deduced from surface morphology measurements by AFM. In due course, the so-prepared unsupported YSZ films might act as well-defined model systems also for technological applications.

  1. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    Energy Technology Data Exchange (ETDEWEB)

    Oguchi, Hiroyuki, E-mail: oguchi@nanosys.mech.tohoku.ac.jp [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Micro System Integration Center (muSIC), Tohoku University, Sendai 980-0845 (Japan); Ikeshoji, Tamio; Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Kuwano, Hiroki [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2014-11-24

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al{sub 2}O{sub 3} substrates indicated polycrystalline films with a LiAlO{sub 2} secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides.

  2. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    International Nuclear Information System (INIS)

    Oguchi, Hiroyuki; Ikeshoji, Tamio; Orimo, Shin-ichi; Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro; Kuwano, Hiroki

    2014-01-01

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al 2 O 3 substrates indicated polycrystalline films with a LiAlO 2 secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides

  3. Self-regulated growth of LaVO3 thin films by hybrid molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhang, Hai-Tian; Engel-Herbert, Roman; Dedon, Liv R.; Martin, Lane W.

    2015-01-01

    LaVO 3 thin films were grown on SrTiO 3 (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO 3 films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application

  4. Epitaxial Fe16N2 thin film on nonmagnetic seed layer

    Science.gov (United States)

    Hang, Xudong; Zhang, Xiaowei; Ma, Bin; Lauter, Valeria; Wang, Jian-Ping

    2018-05-01

    Metastable α″ -Fe16N2 has attracted much interest as a candidate for rare-earth-free hard magnetic materials. We demonstrate that Fe16N2 thin films were grown epitaxially on Cr seed layers with MgO (001) substrates by facing-target sputtering. Good crystallinity with the epitaxial relation MgO (001 )[110 ] ∥ Cr (001 )[100 ] ∥ Fe16N2 (001 )[100 ] was obtained. The chemical order parameter, which quantifies the degree of N ordering in the Fe16N2 (the N-disordered phase is α' -Fe8N martensite), reaches 0.75 for Cr-seeded samples. Cr has a perfect lattice constant match with Fe16N2, and no noticeable strain can be assigned to Fe16N2. The intrinsic saturation magnetization of this non-strained Fe16N2 thin film at room temperature is determined to be 2.31 T by polarized neutron reflectometry and confirmed with vibrating sample magnetometry. Our work provides a platform to directly study the magnetic properties of high purity Fe16N2 films with a high order parameter.

  5. Non-Epitaxial Thin-Film Indium Phosphide Photovoltaics: Growth, Devices, and Cost Analysis

    Science.gov (United States)

    Zheng, Maxwell S.

    In recent years, the photovoltaic market has grown significantly as module prices have continued to come down. Continued growth of the field requires higher efficiency modules at lower manufacturing costs. In particular, higher efficiencies reduce the area needed for a given power output, thus reducing the downstream balance of systems costs that scale with area such as mounting frames, installation, and soft costs. Cells and modules made from III-V materials have the highest demonstrated efficiencies to date but are not yet at the cost level of other thin film technologies, which has limited their large-scale deployment. There is a need for new materials growth, processing and fabrication techniques to address this major shortcoming of III-V semiconductors. Chapters 2 and 3 explore growth of InP on non-epitaxial Mo substrates by MOCVD and CSS, respectively. The results from these studies demonstrate that InP optoelectronic quality is maintained even by growth on non-epitaxial metal substrates. Structural characterization by SEM and XRD show stoichiometric InP can be grown in complete thin films on Mo. Photoluminescence measurements show peak energies and widths to be similar to those of reference wafers of similar doping concentrations. In chapter 4 the TF-VLS growth technique is introduced and cells fabricated from InP produced by this technique are characterized. The TF-VLS method results in lateral grain sizes of >500 mum and exhibits superior optoelectronic quality. First generation devices using a n-TiO2 window layer along with p-type TF-VLS grown InP have reached ˜12.1% power conversion efficiency under 1 sun illumination with VOC of 692 mV, JSC of 26.9 mA/cm2, and FF of 65%. The cells are fabricated using all non-epitaxial processing. Optical measurements show the InP in these cells have the potential to support a higher VOC of ˜795 mV, which can be achieved by improved device design. Chapter 5 describes a cost analysis of a manufacturing process using an

  6. Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wei, X. H.; Li, Y. R.; Zhu, J.; Huang, W.; Zhang, Y.; Luo, W. B.; Ji, H.

    2007-01-01

    Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)- (011)-, and (111)-orientated SrTiO 3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO 3 (001), four orthogonal domains coexisted in the ZnO epilayer, i.e., ZnO(110) parallel SrTiO 3 (001) and ZnO[-111] parallel SrTiO 3 . For (011)- and (111)-orientated substrates, single-domain epitaxy with c axial orientation was observed, in which the in-plane relationship was ZnO[110] parallel SrTiO 3 [110] irrespective of the substrate orientations. Additionally, the crystalline quality of ZnO on SrTiO 3 (111) was better than that of ZnO on SrTiO 3 (011) because of the same symmetry between the (111) substrates and (001) films. The obtained results can be attributed to the difference of the in-plane crystallographic symmetry. Furthermore, those alignments can be explained by the interface stress between the substrates and the films

  7. Development of thin pixel detectors on epitaxial silicon for HEP experiments

    International Nuclear Information System (INIS)

    Boscardin, Maurizio; Calvo, Daniela; Giacomini, Gabriele; Wheadon, Richard; Ronchin, Sabina; Zorzi, Nicola

    2013-01-01

    The foreseen luminosity of the new experiments in High Energy Physics will require that the innermost layer of vertex detectors will be able to sustain fluencies up to 10 16 n eq /cm 2 . Moreover, in many experiments there is a demand for the minimization of the material budget of the detectors. Therefore, thin pixel devices fabricated on n-type silicon are a natural choice to fulfill these requirements due to their rad-hard performances and low active volume. We present an R and D activity aimed at developing a new thin hybrid pixel device in the framework of PANDA experiments. The detector of this new device is a p-on-n pixel sensor realized starting from epitaxial silicon wafers and back thinned up to 50–100 μm after process completion. We present the main technological steps and some electrical characterization on the fabricated devices before and after back thinning and after bump bonding to the front-end electronics

  8. Development of thin pixel detectors on epitaxial silicon for HEP experiments

    Energy Technology Data Exchange (ETDEWEB)

    Boscardin, Maurizio, E-mail: boscardi@fbk.eu [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy); Calvo, Daniela [INFN and Dipartimento di Fisica, Università di Torino, Via Pietro Giuria, I-10125 Torino (Italy); Giacomini, Gabriele [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy); Wheadon, Richard [INFN and Dipartimento di Fisica, Università di Torino, Via Pietro Giuria, I-10125 Torino (Italy); Ronchin, Sabina; Zorzi, Nicola [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy)

    2013-08-01

    The foreseen luminosity of the new experiments in High Energy Physics will require that the innermost layer of vertex detectors will be able to sustain fluencies up to 10{sup 16} n{sub eq}/cm{sup 2}. Moreover, in many experiments there is a demand for the minimization of the material budget of the detectors. Therefore, thin pixel devices fabricated on n-type silicon are a natural choice to fulfill these requirements due to their rad-hard performances and low active volume. We present an R and D activity aimed at developing a new thin hybrid pixel device in the framework of PANDA experiments. The detector of this new device is a p-on-n pixel sensor realized starting from epitaxial silicon wafers and back thinned up to 50–100 μm after process completion. We present the main technological steps and some electrical characterization on the fabricated devices before and after back thinning and after bump bonding to the front-end electronics.

  9. The preparation of Zn-ferrite epitaxial thin film from epitaxial Fe3O4:ZnO multilayers by ion beam sputtering deposition

    International Nuclear Information System (INIS)

    Su, Hui-Chia; Dai, Jeng-Yi; Liao, Yen-Fa; Wu, Yu-Han; Huang, J.C.A.; Lee, Chih-Hao

    2010-01-01

    A new method to grow a well-ordered epitaxial ZnFe 2 O 4 thin film on Al 2 O 3 (0001) substrate is described in this work. The samples were made by annealing the ZnO/Fe 3 O 4 multilayer which was grown with low energy ion beam sputtering deposition. Both the Fe 3 O 4 and ZnO layers were found grown epitaxially at low temperature and an epitaxial ZnFe 2 O 4 thin film was formed after annealing at 1000 o C. X-ray diffraction shows the ZnFe 2 O 4 film is grown with an orientation of ZnFe 2 O 4 (111)//Al 2 O 3 (0001) and ZnFe 2 O 4 (1-10)//Al 2 O 3 (11-20). X-ray absorption spectroscopy studies show that Zn 2+ atoms replace the tetrahedral Fe 2+ atoms in Fe 3 O 4 during the annealing. The magnetic properties measured by vibrating sample magnetometer show that the saturation magnetization of ZnFe 2 O 4 grown from ZnO/Fe 3 O 4 multilayer reaches the bulk value after the annealing process.

  10. 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...

  11. Molecular beam epitaxy growth of InSb1-xBix thin films

    DEFF Research Database (Denmark)

    Yuxin Song; Shumin Wang; Saha Roy, Ivy

    2013-01-01

    Molecular beam epitaxy growth for InSb1-xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology are stu...

  12. Microstructure and magnetic properties of FeCo epitaxial thin films grown on MgO single-crystal substrates

    International Nuclear Information System (INIS)

    Shikada, Kouhei; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    FeCo epitaxial films were prepared on MgO(100), MgO(110), and MgO(111) substrates by ultrahigh vacuum molecular beam epitaxy. FeCo thin films with (100), (211), and (110) planes parallel to the substrate surface grow on respective MgO substrates. FeCo/MgO interface structures are studied by high-resolution cross-sectional transmission electron microscopy and the epitaxial growth mechanism is discussed. Atomically sharp boundaries are recognized between the FeCo thin films and the MgO substrates where misfit dislocations are introduced in the FeCo thin films presumably to decrease the lattice misfits. Misfit dislocations are observed approximately every 9 and 1.4 nm in FeCo thin film at the FeCo/MgO(100) and the FeCo/MgO(110) interfaces, respectively. X-ray diffraction analysis indicates that the lattice spacing measured parallel to the single-crystal substrate surfaces are in agreement within 0.1% with those of the respective bulk values of Fe 50 Co 50 alloy crystal, showing that the FeCo film strain is very small. The magnetic anisotropies of these epitaxial films basically reflect the magnetocrystalline anisotropy of bulk FeCo alloy crystal

  13. Quantized dissipation and random telegraph voltage noise in epitaxial BiSrCaCuO thin films

    International Nuclear Information System (INIS)

    Jung, G.; Savo, B.; Vecchione, A.

    1993-01-01

    In this paper we report on the observation of correlated multiple-voltage RTN switching in high quality epitaxial BiSrCaCuO thin film. We ascribe the correlated noise to the quantization of flux flow dissipation in the film. (orig.)

  14. Advanced fabrication method for the preparation of MOF thin films: Liquid-phase epitaxy approach meets spin coating method.

    KAUST Repository

    Chernikova, Valeriya; Shekhah, Osama; Eddaoudi, Mohamed

    2016-01-01

    Here we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method

  15. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.; Hsu, W.; James, J.; Onyegam, E. U.; Guchhait, S.; Banerjee, S. K.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm

  16. Unit cell determination of epitaxial thin films based on reciprocal space vectors by high-resolution X-ray diffractometry

    OpenAIRE

    Yang, Ping; Liu, Huajun; Chen, Zuhuang; Chen, Lang; Wang, John

    2013-01-01

    A new approach, based on reciprocal space vectors (RSVs), is developed to determine Bravais lattice types and accurate lattice parameters of epitaxial thin films by high-resolution X-ray diffractometry (HR-XRD). The lattice parameters of single crystal substrates are employed as references to correct the systematic experimental errors of RSVs of thin films. The general procedure is summarized, involving correction of RSVs, derivation of raw unit cell, subsequent conversion to the Niggli unit ...

  17. Microstructure evolution in pulsed laser deposited epitaxial Ge-Sb-Te chalcogenide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Ulrich; Lotnyk, Andriy, E-mail: andriy.lotnyk@iom-leipzig.de; Thelander, Erik; Rauschenbach, Bernd

    2016-08-15

    The thin film deposition and structure of highly oriented telluride compounds is of particular interest for phase-change applications in next-generation non-volatile memory such as heterostructure designs, as well as for the investigation of novel optical, thermoelectric and ferroelectric properties in layered telluride compounds. In this work, epitaxial Ge-Sb-Te thin films were successfully produced by pulsed laser deposition on silicon with and without amorphous SiO{sub x} interlayer at elevated process temperatures from a Ge{sub 2}Sb{sub 2}Te{sub 5} target. Aberration-corrected high-resolution scanning transmission electron microscopy (STEM) imaging reveals a distinct interface configuration of the trigonal phase connected by a quasi van der Waals gap (vacancy) to the Sb/Te-passivated single crystalline Si substrate, yet also an intermediate textured growth regime in which the substrate symmetry is only weakly coupled to the thin film orientation, as well as strong deviation of composition at high deposition temperatures. Textured growth of Ge-Sb-Te thin film was also observed on SiO{sub x}/Si substrate with no evidence of an intermediate Sb/Te surface layer on top of an SiO{sub x} layer. In addition, particular defect structures formed by local reorganization of the stacking sequence across the vacancy gap are observed and appear to be intrinsic to these van der Waals-layered compounds. Theoretical image simulations of preferred stacking sequences can be matched to individual building blocks in the Ge-Sb-Te grain. - Highlights: • Atomic-resolution Cs-corrected STEM imaging of PLD deposited Ge-Sb-Te thin films. • Changing of overall composition with increasing deposition temperature. • Direct imaging of surface passivation Sb/Te layer at the Ge-Sb-Te/Si(111) interface. • The Sb/Te passivation layer is not a prerequisite for highly oriented growth of Ge-Sb-Te thin films.

  18. In-plane microwave dielectric properties of paraelectric barium strontium titanate thin films with anisotropic epitaxy

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.; Bellotti, J. A.

    2005-08-01

    In-plane dielectric properties of ⟨110⟩ oriented epitaxial (Ba0.60Sr0.40)TiO3 thin films in the thickness range from 25-1200nm have been investigated under the influence of anisotropic epitaxial strains from ⟨100⟩ NdGaO3 substrates. The measured dielectric properties show strong residual strain and in-plane directional dependence. Below 150nm film thickness, there appears to be a phase transition due to the anisotropic nature of the misfit strain relaxation. In-plane relative permittivity is found to vary from as much as 500-150 along [11¯0] and [001] respectively, in 600nm thick films, and from 75 to 500 overall. Tunability was found to vary from as much as 54% to 20% in all films and directions, and in a given film the best tunability is observed along the compressed axis in a mixed strain state, 54% along [11¯0] in the 600nm film for example.

  19. Strain induced room temperature ferromagnetism in epitaxial magnesium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Zhenghe; Kim, Ki Wook [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nori, Sudhakar; Lee, Yi-Fang; Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kumar, D. [Department of Mechanical Engineering, North Carolina A & T State University, Greensboro, North Carolina 27411 (United States); Wu, Fan [Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey 08540 (United States); Prater, J. T. [Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States)

    2015-10-28

    We report on the epitaxial growth and room-temperature ferromagnetic properties of MgO thin films deposited on hexagonal c-sapphire substrates by pulsed laser deposition. The epitaxial nature of the films has been confirmed by both θ-2θ and φ-scans of X-ray diffraction pattern. Even though bulk MgO is a nonmagnetic insulator, we have found that the MgO films exhibit ferromagnetism and hysteresis loops yielding a maximum saturation magnetization up to 17 emu/cc and large coercivity, H{sub c} = 1200 Oe. We have also found that the saturation magnetization gets enhanced and that the crystallization degraded with decreased growth temperature, suggesting that the origin of our magnetic coupling could be point defects manifested by the strain in the films. X-ray (θ-2θ) diffraction peak shift and strain analysis clearly support the presence of strain in films resulting from the presence of point defects. Based on careful investigations using secondary ion mass spectrometer and X-ray photoelectron spectroscopy studies, we have ruled out the possibility of the presence of any external magnetic impurities. We discuss the critical role of microstructural characteristics and associated strain on the physical properties of the MgO films and establish a correlation between defects and magnetic properties.

  20. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dangwal Pandey, A., E-mail: arti.pandey@desy.de; Grånäs, E.; Shayduk, R.; Noei, H.; Vonk, V. [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Krausert, K.; Franz, D.; Müller, P.; Keller, T. F.; Stierle, A., E-mail: andreas.stierle@desy.de [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Fachbereich Physik, Universität Hamburg, D-22607 Hamburg (Germany)

    2016-08-21

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene.

  1. Wet chemical deposition of single crystalline epitaxial manganite thin films with atomically flat surface

    International Nuclear Information System (INIS)

    Mishra, Amita; Dutta, Anirban; Samaddar, Sayanti; Gupta, Anjan K.

    2013-01-01

    We report the wet chemical deposition of single crystalline epitaxial thin films of the colossal magneto-resistive manganite La 0.67 Sr 0.33 MnO 3 on the lattice-matched (001)-face of a La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 substrate. Topographic images of these films taken with a scanning tunneling microscope show atomically flat terraces separated by steps of monatomic height. The resistivity of these films shows an insulator-metal transition at 310 K, nearly coincident with the Curie temperature of 340 K, found from magnetization measurements. The films show a magnetoresistance of 7% at 300 K and 1.2 T. Their saturation magnetization value at low temperatures is consistent with that of the bulk. - Highlights: ► Wet chemical deposition of La 0.67 Sr 0.33 MnO 3 (LSMO) on a lattice-matched substrate. ► Single crystalline epitaxial LSMO films obtained. ► Flat terraces separated by monatomic steps observed by scanning tunneling microscope

  2. Compliant ferroelastic domains in epitaxial Pb(Zr,Ti)O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Feigl, L.; McGilly, L. J.; Sandu, C. S.; Setter, N. [Ceramics Laboratory, EPFL - Swiss Federal Institute of Technology, Lausanne CH-1015 (Switzerland)

    2014-04-28

    Ordered patterns of highly compliant ferroelastic domains have been created by use of tensile strained epitaxial Pb(Zr,Ti)O{sub 3} thin films, of very low defect density, grown on DyScO{sub 3} substrates. The effect of 180° switching on well-ordered a/c 90° domain patterns is investigated by a combination of transmission electron microscopy, piezoelectric force microscopy, and X-ray diffraction. It is shown that ferroelastic a-domains, having an in-plane polarization, can be created and completely removed on a local level by an out-of-plane electric field. The modifications of the ferroelastic domain pattern can be controlled by varying the parameters used during switching with a piezoresponse force microscope to produce the desired arrangement.

  3. Epitaxial TiN(001) wetting layer for growth of thin single-crystal Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, J. S.; Zhang, X. Y.; Gall, D. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2011-08-15

    Single-crystal Cu(001) layers, 4-1400 nm thick, were deposited on MgO(001) with and without a 2.5-nm-thick TiN(001) buffer layer. X-ray diffraction and reflection indicate that the TiN(001) surface suppresses Cu-dewetting, yielding a 4 x lower defect density and a 9 x smaller surface roughness than if grown on MgO(001) at 25 deg. C. In situ and low temperature electron transport measurements indicate that ultra-thin (4 nm) Cu(001) remains continuous and exhibits partial specular scattering at the Cu-vacuum boundary with a Fuchs-Sondheimer specularity parameter p = 0.6 {+-} 0.2, suggesting that the use of epitaxial wetting layers is a promising approach to create low-resistivity single-crystal Cu nanoelectronic interconnects.

  4. Synthesis and electronic properties of Fe2TiO5 epitaxial thin films

    Science.gov (United States)

    Osada, Motoki; Nishio, Kazunori; Hwang, Harold Y.; Hikita, Yasuyuki

    2018-05-01

    We investigate the growth phase diagram of pseudobrookite Fe2TiO5 epitaxial thin films on LaAlO3 (001) substrates using pulsed laser deposition. Control of the oxygen partial pressure and temperature during deposition enabled selective stabilization of (100)- and (230)-oriented films. In this regime, we find an optical gap of 2.1 eV and room temperature resistivity in the range of 20-80 Ω cm, which are significantly lower than α-Fe2O3, making Fe2TiO5 potentially an ideal inexpensive visible-light harvesting semiconductor. These results provide a basis to incorporate Fe2TiO5 in oxide heterostructures for photocatalytic and photoelectrochemical applications.

  5. Carbon dioxide and water adsorption on highly epitaxial Delafossite CuFeO2 thin film

    Science.gov (United States)

    Rojas, S.; Joshi, T.; Borisov, P.; Sarabia, M.; Lederman, D.; Cabrera, A. L.

    2015-03-01

    Thermal programmed desorption (TPD) of CO2 and H2O from a 200 nm thick CuFeO2 Delafossite surface was performed in a standard UHV chamber, The CuFeO2 thin film grown using Pulsed Laser Deposition (PLD) over an Al2O3 (0001) substrate with controlled O2 atmosphere resulted with highly epitaxial crystal structure. The adsorption/desorption of CO2 and H2O process was also monitored with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Our results revealed that carbon dioxide interacts with CuFeO2 forming Fe carbonates compounds on its surface. Hydroxides were also formed on the surface due to water presence. Using TPD data, Arrhenius plots for CO2 and water desorption were done and activation energy for desorption was obtained. Funds FONDECyT 1130372; Thanks to P. Ferrari.

  6. CeCo5 thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Major, M.; Komissinskiy, P.; Radulov, I.; Alff, L.

    2018-04-01

    Buffer-free, highly textured (0 0 1) oriented CeCo5 thin films showing perpendicular magnetic anisotropy were synthesized on (0 0 1) Al2O3 substrates by molecular beam epitaxy. Ce exists in a mixture of Ce3+ and Ce4+ valence states as shown by X-ray photoelectron spectroscopy. The first anisotropy constant, K1, as measured by torque magnetometry was 0.82 MJ/m3 (8.2 ×106erg /cm3) . A maximum coercivity of 5.16 kOe with a negative temperature coefficient of -0.304%K-1 and a magnetization of 527.30 emu/cm3 was measured perpendicular to the film plane at 5 K. In addition, a large anisotropy of the magnetic moment of 15.5% was observed. These magnetic parameters make CeCo5 a potential candidate material for spintronic and magnetic recording applications.

  7. The effect of a thin silver layer on the critical current of epitaxial YBCO films

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Cohen, D.; Cohen, D.; Snapiro, I.

    1992-01-01

    We compare measurements of the critical current density of an epitaxial YBCO film with that of an identical film overlaid by a thin silver layer. We find that the presence of the silver lowers Tc of the film by about 1.5 K, which is two orders of magnitude larger than predicted by the theory of the proximity effect for our experimental conditions. In addition, J c of the Ag/YBCO film near Tc is also significantly lower than that of the bare YBCO film. We propose two alternate interpretations of this effect, one in terms of destabilization of the flux distribution in the film and the other making use of the effect of the silver on the Bean-Livingston surface barrier for the initial penetration of flux. The latter seems the more plausible explanation of our results. (orig.)

  8. Resistance switching in epitaxial SrCoO{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk, E-mail: cu-jung@hufs.ac.kr [Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Kim, Yeon Soo; Park, Bae Ho [Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-791 (Korea, Republic of); Jeong, Huiseong; Park, Ji-Yong [Department of Physics and Division of Energy System Research, Ajou University, Suwon 443-749 (Korea, Republic of); Cho, Myung Rae; Park, Yun Daniel [Department of Physics and Astronomy and Center for Subwavelength Optics, Seoul National University, Seoul 151-747 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Dong-Wook [Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Jin, Hyunwoo; Lee, Suyoun [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong [Department of Material Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-08-11

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO{sub 3} (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO{sub 2.5}) and conducting perovskite (SrCoO{sub 3−δ}) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO{sub x} thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO{sub 2.5}.

  9. Epitaxial growth and electronic structure of oxyhydride SrVO{sub 2}H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tsukasa; Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Yamada, Keisuke; Onozuka, Tomoya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shigematsu, Kei [Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan); Minohara, Makoto; Kumigashira, Hiroshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Mikazuki-cho, Hyogo 679-5198 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan)

    2016-08-28

    Oxyhydride SrVO{sub 2}H epitaxial thin films were fabricated on SrTiO{sub 3} substrates via topotactic hydridation of oxide SrVO{sub 3} films using CaH{sub 2}. Structural and composition analyses suggested that the SrVO{sub 2}H film possessed one-dimensionally ordered V-H{sup −}-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO{sub 2}H film was reversible to SrVO{sub 3} by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V{sup 3+} valence state in the SrVO{sub 2}H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  10. Epitaxial growth and electronic structure of oxyhydride SrVO2H thin films

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Yamada, Keisuke; Shigematsu, Kei; Onozuka, Tomoya; Minohara, Makoto; Kumigashira, Hiroshi; Ikenaga, Eiji; Hasegawa, Tetsuya

    2016-08-01

    Oxyhydride SrVO2H epitaxial thin films were fabricated on SrTiO3 substrates via topotactic hydridation of oxide SrVO3 films using CaH2. Structural and composition analyses suggested that the SrVO2H film possessed one-dimensionally ordered V-H--V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO2H film was reversible to SrVO3 by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V3+ valence state in the SrVO2H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  11. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Hao [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Hong Jiawang; Zhang Yihui [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Li Faxin [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Pei Yongmao, E-mail: peiym@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Fang Daining, E-mail: fangdn@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2012-09-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO{sub 3} thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  12. Polarized Raman scattering study of PSN single crystals and epitaxial thin films

    Directory of Open Access Journals (Sweden)

    J. Pokorný

    2015-06-01

    Full Text Available This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc0.5Nb0.5O3 (PSN single crystals and epitaxially compressed thin films grown on (100-oriented MgO substrates. It is found that there are significant differences between the properties of the crystals and films, and that these differences can be attributed to the anticipated structural differences between these two forms of the same material. In particular, the scattering characteristics of the oxygen octahedra breathing mode near 810 cm-1 indicate a ferroelectric state for the crystals and a relaxor state for the films, which is consistent with the dielectric behaviors of these materials.

  13. Structural analysis of LaVO3 thin films under epitaxial strain

    Directory of Open Access Journals (Sweden)

    H. Meley

    2018-04-01

    Full Text Available Rare earth vanadate perovskites exhibit a phase diagram in which two different types of structural distortions coexist: the strongest, the rotation of the oxygen octahedra, comes from the small tolerance factor of the perovskite cell (t = 0.88 for LaVO3 and the smaller one comes from inter-site d-orbital interactions manifesting as a cooperative Jahn-Teller effect. Epitaxial strain acts on octahedral rotations and crystal field symmetry to alter this complex lattice-orbit coupling. In this study, LaVO3 thin film structures have been investigated by X-ray diffraction and scanning transmission electron microscopy. The analysis shows two different orientations of octahedral tilt patterns, as well as two distinct temperature behaviors, for compressive and tensile film strain states. Ab initio calculations capture the strain effect on the tilt pattern orientation in agreement with experimental data.

  14. Doping site dependent thermoelectric properties of epitaxial strontium titanate thin films

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Mehdizadeh Dehkordi, Arash; Tritt, Terry M.; Alshareef, Husam N.

    2014-01-01

    We demonstrate that the thermoelectric properties of epitaxial strontium titanate (STO) thin films can be improved by additional B-site doping of A-site doped ABO3 type perovskite STO. The additional B-site doping of A-site doped STO results in increased electrical conductivity, but at the expense of Seebeck coefficient. However, doping on both sites of the STO lattice significantly reduces the lattice thermal conductivity of STO by adding more densely and strategically distributed phononic scattering centers that attack wider phonon spectra. The additional B-site doping limits the trade-off relationship between the electrical conductivity and total thermal conductivity of A-site doped STO, leading to an improvement in the room-temperature thermoelectric figure of merit, ZT. The 5% Pr3+ and 20% Nb5+ double-doped STO film exhibits the best ZT of 0.016 at room temperature. This journal is

  15. Spin Seebeck effect in insulating epitaxial γ−Fe2O3 thin films

    Directory of Open Access Journals (Sweden)

    P. Jiménez-Cavero

    2017-02-01

    Full Text Available We report the fabrication of high crystal quality epitaxial thin films of maghemite (γ−Fe2O3, a classic ferrimagnetic insulating iron oxide. Spin Seebeck effect (SSE measurements in γ−Fe2O3/Pt bilayers as a function of sample preparation conditions and temperature yield a SSE coefficient of 0.5(1 μV/K at room temperature. Dependence on temperature allows us to estimate the magnon diffusion length in maghemite to be in the range of tens of nanometers, in good agreement with that of conducting iron oxide magnetite (Fe3O4, establishing the relevance of spin currents of magnonic origin in magnetic iron oxides.

  16. High efficiency thin film solar cells grown by molecular beam epitaxy (HEFTY)

    Energy Technology Data Exchange (ETDEWEB)

    Mason, N.B.; Barnham, K.W.J.; Ballard, I.M.; Zhang, J. [Imperial College, London (United Kingdom)

    2006-05-04

    The project sought to show the UK as a world leader in the field of thin film crystalline solar cells. A premise was that the cell design be suitable for large-scale manufacturing and provide a basis for industrial exploitation. The study demonstrated (1) that silicon films grown at temperatures suitable for deposition on glass by Gas Phase Molecular Beam Epitaxy gives better PV cells than does Ultra Low Pressure Chemical Vapor Deposition; (2) a conversion energy of 15 per cent was achieved - the project target was 18 per cent and (3) one of the highest reported conversion efficiencies for a 15 micrometre silicon film was achieved. The study was carried out by BP Solar Limited under contract to the DTI.

  17. Epitaxial Pb(Zr,Ti)O3 thin films for a MEMS application

    International Nuclear Information System (INIS)

    Nguyen, Minh D; Vu, Hung N; Blank, Dave H A; Rijnders, Guus

    2011-01-01

    This research presents the deposition and device fabrication of epitaxial Pb(Zr,Ti)O 3 (PZT) thin films for applications in microelectromechanical systems (MEMS). A piezoelectric micro-membrane is described as an example. Using the pulsed laser deposition (PLD) technique and the MEMS microfabrication process, the piezo-membranes with diameters ranging from 200 to 500 μm were obtained. The displacement of piezo-membranes increased from 5.1 to 17.5 nm V −1 with a piezoelectric-membrane diameter in the range of 200–500 μm. Furthermore, the effect of PZT film-thickness on the mechanical properties has been investigated. By using the conductive-oxide SrRuO 3 (SRO) layers as the electrodes, the degradation of both ferroelectric and piezoelectric properties is prevented up to 10 10 switching cycles

  18. Chemical solution synthesis and ferromagnetic resonance of epitaxial thin films of yttrium iron garnet

    Science.gov (United States)

    Lucas, Irene; Jiménez-Cavero, Pilar; Vila-Fungueiriño, J. M.; Magén, Cesar; Sangiao, Soraya; de Teresa, José Maria; Morellón, Luis; Rivadulla, Francisco

    2017-12-01

    We report the fabrication of epitaxial Y3F e5O12 (YIG) thin films on G d3G a5O12 (111) using a chemical solution method. Cubic YIG is a ferrimagnetic material at room temperature, with excellent magneto-optical properties, high electrical resistivity, and a very narrow ferromagnetic resonance, which makes it particularly suitable for applications in filters and resonators at microwave frequencies. But these properties depend on the precise stoichiometry and distribution of F e3 + ions among the octahedral/tetrahedral sites of a complex structure, which hampered the production of high-quality YIG thin films by affordable chemical methods. Here we report the chemical solution synthesis of YIG thin films, with excellent chemical, crystalline, and magnetic homogeneity. The films show a very narrow ferromagnetic resonance (long spin relaxation time), comparable to that obtained from high-vacuum physical deposition methods. These results demonstrate that chemical methods can compete to develop nanometer-thick YIG films with the quality required for spintronic devices and other high-frequency applications.

  19. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  20. Interface formation and defect structures in epitaxial La2Zr2O7 thin films on (111) Si

    International Nuclear Information System (INIS)

    Seo, J.W.; Fompeyrine, J.; Guiller, A.; Norga, G.; Marchiori, C.; Siegwart, H.; Locquet, J.-P.

    2003-01-01

    We have studied the growth of epitaxial La 2 Zr 2 O 7 thin films on (111) Si. Although the interface structure can be strongly affected by the Si oxidation during the deposition process, epitaxial growth of La 2 Zr 2 O 7 was obtained. A detailed study by means of transmission electron microscopy reveals two types of structures (pyrochlore and fluorite) with the same average chemical composition but strong differences in reactivity and interface formation. The structural complexity of the ordered pyrochlore structure seems to prevent excess oxygen diffusion and interfacial SiO 2 formation

  1. Epitaxial growth of cubic Gd{sub 2}O{sub 3} thin films on Ge substrates

    Energy Technology Data Exchange (ETDEWEB)

    Molle, A; Wiemer, C; Bhuiyan, M D N K; Tallarida, G; Fanciulli, M [CNR-INFM, Laboratorio Nazionale MDM, via C. Olivetti 2, I-20041 Agrate Brianza (Italy)], E-mail: alessandro.molle@mdm.infm.it

    2008-03-15

    Gd{sub 2}O{sub 3} thin films were grown on Ge (001) substrates by molecular beam epitaxy. The epitaxial character of the film is demonstrated by electron diffraction during the growth. The structural characterization of the films shows that the Gd{sub 2}O{sub 3} forms a bixbyite polymorph with a (110) out-of-plane orientation. The formation of bixbyite structured Gd{sub 2}O{sub 3} is discussed in terms of the atomic arrangement of the oxide planes on the Ge(001) surface.

  2. Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

    OpenAIRE

    Kawashima, Kazuhiro; Okamoto, Yuji; Annayev, Orazmuhammet; Toyokura, Nobuo; Takahashi, Ryota; Lippmaa, Mikk; Itaka, Kenji; Suzuki, Yoshikazu; Matsuki, Nobuyuki; Koinuma, Hideomi

    2017-01-01

    Abstract As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic?inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thic...

  3. Metallic transport and large anomalous Hall effect at room temperature in ferrimagnetic Mn{sub 4}N epitaxial thin film

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xi; Shigematsu, Kei [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Fukumura, Tomoteru [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2014-08-18

    We report the electrical transport properties of ferrimagnetic Mn{sub 4}N (001) epitaxial thin films grown by pulsed laser deposition on MgO (001) substrates. The Mn{sub 4}N thin films were tetragonally distorted with a ratio of out-of-plane to in-plane lattice constants of 0.987 and showed perpendicular magnetic anisotropy with an effective magnetic anisotropy constant of 0.16 MJ/m{sup 3}, which is comparable with that of a recently reported molecular-beam-epitaxy-grown film. The thin films exhibited metallic transport with a room temperature resistivity of 125 μΩ cm in addition to a large anomalous Hall effect with a Hall angle tangent of 0.023.

  4. Metallic transport and large anomalous Hall effect at room temperature in ferrimagnetic Mn4N epitaxial thin film

    International Nuclear Information System (INIS)

    Shen, Xi; Shigematsu, Kei; Chikamatsu, Akira; Fukumura, Tomoteru; Hirose, Yasushi; Hasegawa, Tetsuya

    2014-01-01

    We report the electrical transport properties of ferrimagnetic Mn 4 N (001) epitaxial thin films grown by pulsed laser deposition on MgO (001) substrates. The Mn 4 N thin films were tetragonally distorted with a ratio of out-of-plane to in-plane lattice constants of 0.987 and showed perpendicular magnetic anisotropy with an effective magnetic anisotropy constant of 0.16 MJ/m 3 , which is comparable with that of a recently reported molecular-beam-epitaxy-grown film. The thin films exhibited metallic transport with a room temperature resistivity of 125 μΩ cm in addition to a large anomalous Hall effect with a Hall angle tangent of 0.023.

  5. Preparation and structure characterization of SmCo5(0001) epitaxial thin films grown on Cu(111) underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    SmCo 5 (0001) epitaxial films were prepared on Cu(111) single-crystal underlayers formed on Al 2 O 3 (0001) substrates at 500 deg. C. The nucleation and growth mechanism of (0001)-oriented SmCo 5 crystal on Cu(111) underlayer is investigated and a method to control the nucleation is proposed. The SmCo 5 epitaxial thin film formed directly on Cu underlayer consists of two types of domains whose orientations are rotated around the film normal by 30 deg. each other. By introducing a thin Co seed layer on the Cu underlayer, a SmCo 5 (0001) single-crystal thin film is successfully obtained. Nucleation of SmCo 5 crystal on Cu underlayer seems controllable by varying the interaction between the Cu underlayer and the SmCo 5 layer

  6. General Top-Down Ion Exchange Process for the Growth of Epitaxial Chalcogenide Thin Films and Devices

    KAUST Repository

    Xia, Chuan

    2016-12-30

    We demonstrate a versatile top-down ion exchange process, done at ambient temperature, to form epitaxial chalcogenide films and devices, with nanometer scale thickness control. To demonstrate the versatility of our process we have synthesized (1) epitaxial chalcogenide metallic and semiconducting films and (2) free-standing chalcogenide films and (3) completed in situ formation of atomically sharp heterojunctions by selective ion exchange. Epitaxial NiCo2S4 thin films prepared by our process show 115 times higher mobility than NiCo2S4 pellets (23 vs 0.2 cm(2) V-1 s(-1)) prepared by previous reports. By controlling the ion exchange process time, we made free-standing epitaxial films of NiCo2S4 and transferred them onto different substrates. We also demonstrate in situ formation of atomically sharp, lateral Schottky diodes based on NiCo2O4/NiCo2S4 heterojunction, using a single ion exchange step. Additionally, we show that our approach can be easily extended to other chalcogenide semiconductors. Specifically, we used our process to prepare Cu1.8S thin films with mobility that matches single crystal Cu1.8S (25 cm(2) V-1 s(-1)), which is ca. 28 times higher than the previously reported Cu1.8S thin film mobility (0.58 cm(2) V-1 s(-1)), thus demonstrating the universal nature of our process. This is the first report in which chalcogenide thin films retain the epitaxial nature of the precursor oxide films, an approach that will be useful in many applications.

  7. Multiferroic fluoride BaCoF4 Thin Films Grown Via Molecular Beam Epitaxy

    Science.gov (United States)

    Borisov, Pavel; Johnson, Trent; García-Castro, Camilo; Kc, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo; Lederman, David

    Multiferroic materials exhibit exciting physics related to the simultaneous presence of multiple long-range orders, in many cases consisting of antiferromagnetic (AF) and ferroelectric (FE) orderings. In order to provide a new, promising route for fluoride-based multiferroic material engineering, we grew multiferroic fluoride BaCoF4 in thin film form on Al2O3 (0001) substrates by molecular beam epitaxy. The films grow with the orthorhombic b-axis out-of-plane and with three in-plane structural twin domains along the polar c-axis directions. The FE ordering in thin films was verified by FE remanent hysteresis loops measurements at T = 14 K and by room temperature piezoresponse force microscopy (PFM). An AF behavior was found below Neel temperature TN ~ 80 K, which is in agreement with the bulk properties. At lower temperatures two additional magnetic phase transitions at 19 K and 41 K were found. First-principles calculations demonstrated that the growth strain applied to the bulk BaCoF4 indeed favors two canted spin orders, along the b- and a-axes, respectively, in addition to the main AF spin order along the c-axis. Supported by FAME (Contract 2013-MA-2382), WV Research Challenge Grant (HEPC.dsr.12.29), and DMREF-NSF 1434897.

  8. InGaN-based thin film solar cells: Epitaxy, structural design, and photovoltaic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Liwen, E-mail: SANG.Liwen@nims.go.jp [International Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); JST-PRESTO, The Japan Science and Technology Agency, Tokyo 102-0076 (Japan); Liao, Meiyong; Koide, Yasuo [Wide Bandgap Materials Group, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sumiya, Masatomo [Wide Bandgap Materials Group, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); JST-ALCA, The Japan Science and Technology Agency, Tokyo 102-0076 (Japan)

    2015-03-14

    In{sub x}Ga{sub 1−x}N, with the tunable direct bandgaps from ultraviolet to near infrared region, offers a promising candidate for the high-efficiency next-generation thin-film photovoltaic applications. Although the adoption of thick InGaN film as the active region is desirable to obtain efficient light absorption and carrier collection compared to InGaN/GaN quantum wells structure, the understanding on the effect from structural design is still unclear due to the poor-quality InGaN films with thickness and difficulty of p-type doping. In this paper, we comprehensively investigate the effects from film epitaxy, doping, and device structural design on the performances of the InGaN-based solar cells. The high-quality InGaN thick film is obtained on AlN/sapphire template, and p-In{sub 0.08}Ga{sub 0.92}N is achieved with a high hole concentration of more than 10{sup 18 }cm{sup −3}. The dependence of the photovoltaic performances on different structures, such as active regions and p-type regions is analyzed with respect to the carrier transport mechanism in the dark and under illumination. The strategy of improving the p-i interface by using a super-thin AlN interlayer is provided, which successfully enhances the performance of the solar cells.

  9. InGaN-based thin film solar cells: Epitaxy, structural design, and photovoltaic properties

    Science.gov (United States)

    Sang, Liwen; Liao, Meiyong; Koide, Yasuo; Sumiya, Masatomo

    2015-03-01

    InxGa1-xN, with the tunable direct bandgaps from ultraviolet to near infrared region, offers a promising candidate for the high-efficiency next-generation thin-film photovoltaic applications. Although the adoption of thick InGaN film as the active region is desirable to obtain efficient light absorption and carrier collection compared to InGaN/GaN quantum wells structure, the understanding on the effect from structural design is still unclear due to the poor-quality InGaN films with thickness and difficulty of p-type doping. In this paper, we comprehensively investigate the effects from film epitaxy, doping, and device structural design on the performances of the InGaN-based solar cells. The high-quality InGaN thick film is obtained on AlN/sapphire template, and p-In0.08Ga0.92N is achieved with a high hole concentration of more than 1018 cm-3. The dependence of the photovoltaic performances on different structures, such as active regions and p-type regions is analyzed with respect to the carrier transport mechanism in the dark and under illumination. The strategy of improving the p-i interface by using a super-thin AlN interlayer is provided, which successfully enhances the performance of the solar cells.

  10. Topotactic Metal-Insulator Transition in Epitaxial SrFeOx Thin Films.

    Science.gov (United States)

    Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; Kim, Minu; Kang, Tae Dong; Lee, Jaekwang; Roh, Seulki; Jung, In-Ho; Hwang, Jungseek; Kim, Sung Wng; Noh, Tae Won; Ohta, Hiromichi; Choi, Woo Seok

    2017-10-01

    Topotactic phase transformation enables structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for elucidating the redox reaction and oxygen diffusion within transition metal oxides. In addition, it enables tuning of the emergent physical properties of complex oxides, through strong interaction between the lattice and electronic degrees of freedom. In this communication, the electronic structure evolution of SrFeO x epitaxial thin films is identified in real-time, during the progress of reversible topotactic phase transformation. Using real-time optical spectroscopy, the phase transition between the two structurally distinct phases (i.e., brownmillerite and perovskite) is quantitatively monitored, and a pressure-temperature phase diagram of the topotactic transformation is constructed for the first time. The transformation at relatively low temperatures is attributed to a markedly small difference in Gibbs free energy compared to the known similar class of materials to date. This study highlights the phase stability and reversibility of SrFeO x thin films, which is highly relevant for energy and environmental applications exploiting the redox reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films

    International Nuclear Information System (INIS)

    Biswas, Abhijit; Jeong, Yoon Hee

    2015-01-01

    Strong spin-orbit coupled 5d transition metal based ABO 3 oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO 3 . Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO 3 thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics

  12. Thin film growth of CaFe2As2 by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Hatano, T; Fujimoto, R; Nakamura, I; Mori, Y; Ikuta, H; Kawaguchi, T; Harada, S; Ujihara, T

    2016-01-01

    Film growth of CaFe 2 As 2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe 2 As 2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch. (paper)

  13. Thin film growth of CaFe2As2 by molecular beam epitaxy

    Science.gov (United States)

    Hatano, T.; Kawaguchi, T.; Fujimoto, R.; Nakamura, I.; Mori, Y.; Harada, S.; Ujihara, T.; Ikuta, H.

    2016-01-01

    Film growth of CaFe2As2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe2As2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch.

  14. Oxygen engineering of HfO{sub 2-x} thin films grown by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institut fuer Materialwissenschaft, TU-Darmstadt (Germany); Zaumseil, Peter; Schroeder, Thomas [IHP, Frankfurt, Oder (Germany)

    2010-07-01

    Reactive molecular beam epitaxy (R-MBE) is an ideal tool for tailoring physical properties of thin films to specific needs. For the development of cutting-edge oxides for thin film applications a precise control of oxygen defects is crucial. R-MBE in combination with rf-activated oxygen allows reproducibly growing oxide thin films with precise oxidation conditions enabling oxygen engineering. R-MBE was used to grow Hf and HfO{sub 2{+-}}{sub x} thin films with different oxidation conditions on sapphire single crystal substrates. Structural characterization was carried out using rotating anode x-ray diffraction revealing highly textured to epitaxial thin films on c-cut sapphire. Furthermore, switching of film orientation by varying the oxidation conditions was observed demonstrating the role of oxygen in the growth procedure. The investigation of electrical properties using a four probe measurement setup showed conductivities in the range of 1000 {mu}{omega}cm for oxygen deficient HfO{sub 2-x} thin films. Optical properties were investigated using a photospectrometer and additionally x-ray photoelectron spectroscopy was carried out to study the band gap and valence states. Both techniques were used to monitor the oxygen content in deficient HfO{sub 2-x} thin films. Our results demonstrate the importance of oxygen engineering even in the case of 'simple' oxides.

  15. Bi-epitaxial YBa2Cu3Ox Thin Films on Tilted-axes NdGaO3 Substrates with CeO2 Seeding Layer

    International Nuclear Information System (INIS)

    Mozhaev, P B; Mozhaeva, J E; Jacobsen, C S; Hansen, J Bindslev; Bdikin, I K; Luzanov, V A; Kotelyanskii, I M; Zybtsev, S G

    2006-01-01

    Bi-epitaxial YBa 2 Cu 3 O x (YBCO) thin films with out-of-plane tilt angle in the range 18 - 27 0 were manufactured using pulsed laser deposition on NdGaO 3 tilted-axes substrates with CeO 2 seeding layers. The YBCO thin film orientation over the seeding layer depended on deposition conditions. Removal of the seeding layer from part of the substrate surface by ionbeam etching resulted in formation of a bi-epitaxial thin film with different c-axis orientation of two parts of the film. The bi-epitaxial film orientation and structure were studied using X-ray diffraction techniques, and surface morphology was observed with atomic force microscope (AFM). Photolithography and ion-beam etching techniques were used for patterning bi-epitaxial thin films. Electrical characterization of the obtained structures was performed

  16. Stranski-Krastanow islanding initiated on the stochastic rough surfaces of the epitaxially strained thin films

    International Nuclear Information System (INIS)

    Tarik Ogurtani, Omer; Celik, Aytac; Emre Oren, Ersin

    2014-01-01

    Quantum dots (QD) have discrete energy spectrum, which can be adjusted over a wide range by tuning composition, density, size, lattice strain, and morphology. These features make quantum dots attractive for the design and fabrication of novel electronic, magnetic and photonic devices and other functional materials used in cutting-edge applications. The formation of QD on epitaxially strained thin film surfaces, known as Stranski-Krastanow (SK) islands, has attracted great attention due to their unique electronic properties. Here, we present a systematic dynamical simulation study for the spontaneous evolution of the SK islands on the stochastically rough surfaces (nucleationless growth). During the development of SK islands through the mass accumulation at randomly selected regions of the film via surface drift-diffusion (induced by the capillary and mismatch stresses) with and/or without growth, one also observes the formation of an extremely thin wetting layer having a thickness of a few Angstroms. Above a certain threshold level of the mismatch strain and/or the size of the patch, the formation of multiple islands separated by shallow wetting layers is also observed as metastable states such as doublets even multiplets. These islands are converted into a distinct SK islands after long annealing times by coalescence through the long range surface diffusion. Extensive computer simulation studies demonstrated that after an initial transient regime, there is a strong quadratic relationship between the height of the SK singlet and the intensity of the lattice mismatch strain (in a wide range of stresses up to 8.5 GPa for germanium thin crystalline films), with the exception at those critical points where the morphological (shape change with necking) transition takes place.

  17. Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al2O3(0001) substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

    2007-01-01

    Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al 2 O 3 (0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively

  18. Tensile strain induced changes in the optical spectra of SrTiO.sub.3./sub. epitaxial thin films

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Tyunina, M.; Narkilahti, J.; Levoska, J.; Chvostová, Dagmar; Jastrabík, Lubomír; Trepakov, Vladimír

    2010-01-01

    Roč. 52, č. 10 (2010), 2082-2089 ISSN 1063-7834 R&D Projects: GA ČR GA202/08/1009; GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : SrTiO 3 epitaxial thin films * effect of biaxial tensile strains on optical spectra Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.727, year: 2010

  19. Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon Jun; Lee, Sung Su; Kwak, Jeong Hun; Kim, Young-Min; Jeong, Hu Young; Borisevich, Albina Y.; Lee, Su Yong; Noh, Do Young; Kwon, Owoong; Kim, Yunseok; Jo, Ji Young

    2016-12-01

    For epitaxial films, a critical thickness (tc) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling.

  20. Oxygen incorporation effects in annealed epitaxial La(1-x)SrxMnO3 thin films

    International Nuclear Information System (INIS)

    Petrisor, T.; Gabor, M. S.; Tiusan, C.; Boulle, A.; Bellouard, C.; Pana, O.; Petrisor, T.

    2011-01-01

    This paper presents our results regarding oxygen incorporation effects in epitaxial La (1-x) Sr x MnO 3 thin films, deposited on SrTiO 3 (001) single crystal substrates, by annealing in different gas mixtures of argon and oxygen. A particular emphasis is placed on the correlation of structural properties with the magnetic properties of the films, Curie temperature, and coercive field. In this sense, we demonstrate that the evolution of the diffuse part of the ω-scans performed on the films are due to oxygen excess in the film lattice, which creates cationic vacancies within the films. Also, we show that two regimes of oxygen incorporation in the films exist, one in which the films evolve toward a single phase and oxygen stoichiometry is recovered, and a second one dominated by oxygen over-doping effects. In order to support our study, XPS measurements were performed, from which we have evaluated the Mn 3+ /Mn 4+ ionic ratio.

  1. Anisotropic ferromagnetic behaviors in highly orientated epitaxial NiO-based thin films

    Directory of Open Access Journals (Sweden)

    Yu-Jun Zhang

    2015-07-01

    Full Text Available Antiferromagnetic materials attract a great amount of attention recently for promising antiferromagnet-based spintronics applications. NiO is a conventional antiferromagnetic semiconductor material and can show ferromagnetism by doping other magnetic elements. In this work, we synthesized epitaxial Fe-doped NiO thin films on SrTiO3 substrates with various crystal orientations by pulsed laser deposition. The room-temperature ferromagnetism of these films is anisotropic, including the saturated magnetization and the coercive field. The anisotropic magnetic behaviors of Fe-doped NiO diluted magnetic oxide system should be closely correlated to the magnetic structure of antiferromagnetic NiO base. Within the easy plane of NiO, the coercive field of the films becomes smaller, and larger coercive field while tested out of the easy plane of NiO. The saturated magnetization anisotropy is due to different strain applied by different substrates. These results lead us to more abundant knowledge of the exchange interactions in this conventional antiferromagnetic system.

  2. Epitaxial growth and properties of YBaCuO thin films

    International Nuclear Information System (INIS)

    Geerk, J.; Linker, G.; Meyer, O.

    1989-08-01

    The growth quality of YBaCuO thin films deposited by sputtering on different substrates (Al 2 O 3 , MgO, SrTiO 3 , Zr(Y)O 2 ) has been studied by X-ray diffraction and channeling experiments as a function of the deposition temperature. Besides the substrate orientation, the substrate temperature is the parameter determining whether films grow in c-, a-, (110) or mixed directions. Epitaxial growth correlates with high critical current values in the films of up to 5.5x10 6 A/cm 2 at 77 K. Ultrathin films with thicknesses down to 2 nm were grown revealing three-dimensional superconducting behaviour. Films on (100) SrTiO 3 of 9 nm thickness and below are partially strained indicating commensurate growth. From the analysis of the surface disorder 1 displaced Ba atom per Ba 2 Y row was obtained indicating that the disordered layer thickness is about 0.6 nm. Tunnel junctions fabricated on these films reveal gap-like structures near ±16 mV and ±30 mV. (orig.) [de

  3. Magnetic and magnetoelastic properties of epitaxial SmFe{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    Fuente, C de la; Arnaudas, J I; Ciria, M; Del Moral, A [Departamento de Magnetismo de Solidos and Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de los Materiales de Aragon and Universidad de Zaragoza, 50071, Zaragoza (Spain); Dufour, C; Dumesnil, K, E-mail: cesar@unizar.e [Laboratoire de Metallurgie Physique et de Science des Materiaux, Universite Henry Poincare, Nancy 1, BP 239, 54506 (France)

    2010-02-03

    We report on magnetic and magnetoelastic measurements for a 5000 A (110) SmFe{sub 2} thin film, which was successfully analyzed by means of a point charge model for describing the effect of the epitaxial growth in this kind of system. Some of the main conclusions of the Moessbauer and magnetoelastic results and the new magnetization results up to 5 T allow us to get a full description of the crystal electric field, exchange, and magnetoelastic behavior in this compound. So, new single-ion parameters are obtained for the crystal field interaction of samarium ions, A{sub 4}(r{sup 4}) = +755 K/ion and A{sub 6}(r{sup 6}) = -180 K/ion, and new single-ion magnetoelastic coupling B{sup gamma}{sup ,2}approx =-200 MPa and B{sup epsilon}{sup ,2}approx =800 MPa, which represent the tetragonal and the in-plane shear deformations, respectively. Moreover, the new thermal behavior of the samarium magnetic moment, the exchange coupling parameter, and the magnetocrystalline anisotropy of the iron sublattice are obtained too. From these, the softening of the spin reorientation transition with respect to the bulk case could be accounted for.

  4. Structural characterization of epitaxial LiFe_5O_8 thin films grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Loukya, B.; Negi, D.S.; Sahu, R.; Pachauri, N.; Gupta, A.; Datta, R.

    2016-01-01

    We report on detailed microstructural and atomic ordering characterization by transmission electron microscopy in epitaxial LiFe_5O_8 (LFO) thin films grown by chemical vapor deposition (CVD) on MgO (001) substrates. The experimental results of LFO thin films are compared with those for bulk LFO single crystal. Electron diffraction studies indicate weak long-range ordering in LFO (α-phase) thin films in comparison to bulk crystal where strong ordering is observed in optimally annealed samples. The degree of long-range ordering depends on the growth conditions and the thickness of the film. Annealing experiment along with diffraction study confirms the formation of α-Fe_2O_3 phase in some regions of the films. This suggests that under certain growth conditions γ-Fe_2O_3-like phase forms in some pockets in the as-grown LFO thin films that then convert to α-Fe_2O_3 on annealing. - Highlights: • Atomic ordering in LiFe_5O_8 bulk single crystal and epitaxial thin films. • Electron diffraction studies reveal different level of ordering in the system. • Formation of γ-Fe_2O_3 like phase has been observed.

  5. Microstructure of epitaxial SrRuO 3 thin films on MgO substrates

    Science.gov (United States)

    Ai, Wan Yong; Zhu, Jun; Zhang, Ying; Li, Yan Rong; Liu, Xing Zhao; Wei, Xian Hua; Li, Jin Long; Zheng, Liang; Qin, Wen Feng; Liang, Zhu

    2006-09-01

    SrRuO 3 thin films have been grown on singular (1 0 0) MgO substrates using pulsed laser deposition (PLD) in 30 Pa oxygen ambient and at a temperature of 400-700 °C. Ex situ reflection high-energy electron diffraction (RHEED) as well as X-ray diffraction (XRD) θ/2 θ scan indicated that the films deposited above 650 °C were well crystallized though they had a rough surface as shown by atom force microscopy (AFM). XRD Φ scans revealed that these films were composed of all three different types of orientation domains, which was further confirmed by the RHEED patterns. The heteroepitaxial relationship between SrRuO 3 and MgO was found to be [1 1 0] SRO//[1 0 0] MgO and 45°-rotated cube-on-cube [0 0 1] SRO//[1 0 0] MgO. These domain structures and surface morphology are similar to that of ever-reported SrRuO 3 thin films deposited on the (0 0 1) LaAlO 3 substrates, and different from those deposited on (0 0 1) SrTiO 3 substrates that have an atomically flat surface and are composed of only the [1 1 0]-type domains. The reason for this difference was ascribed to the effect of lattice mismatch across the film/substrate interface. The room temperature resistivity of SrRuO 3 films fabricated at 700 °C was 300 μΩ cm. Therefore, epitaxial SrRuO 3 films on MgO substrate could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.

  6. Optical properties of aluminum nitride thin films grown by direct-current magnetron sputtering close to epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, A. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Soltani, A., E-mail: ali.soltani@iemn.univ-lille1.fr [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Abdallah, B. [Department of Materials Physics, Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON (FOTON), UMR CNRS 6082, 6, rue de Kerampont CS 80518, 22305 Lannion Cedex (France); Deresmes, D. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Jouan, P.-Y.; Djouadi, M.A. [Institut des Matériaux Jean Rouxel – IMN, UMR CNRS 6502, 2, rue de la Houssinère BP 32229, 44322 Nantes (France); Dogheche, E.; De Jaeger, J.-C. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France)

    2013-05-01

    Low-temperature Aluminum Nitride (AlN) thin films with a thickness of 3 μm were deposited by Direct-Current magnetron sputtering on sapphire substrate. They present optical properties similar to those of epitaxially grown films. Different characterization methods such as X-Ray Diffraction, Transmission Electron Microscopy and Atomic Force Microscopy were used to determine the structural properties of the films such as its roughness and crystallinity. Newton interferometer was used for stress measurement of the films. Non-destructive prism-coupling technique was used to determine refractive index and thickness homogeneity by a mapping on the whole sample area. Results show that AlN films grown on AlGaN layer have a high crystallinity close to epitaxial films, associated to a low intrinsic stress for low thickness. These results highlight that it is possible to grow thick sample with microstructure and optical properties close to epitaxy, even on a large surface. - Highlights: ► Aluminum Nitride sputtering technique with a low temperature growth process ► Epitaxial quality of two microns sputtered Aluminum Nitride film ► Optics as a non-destructive accurate tool for acoustic wave investigation.

  7. Growth and characterization of III-N ternary thin films by plasma assisted atomic layer epitaxy at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Nepal, Neeraj; Anderson, Virginia R.; Hite, Jennifer K.; Eddy, Charles R.

    2015-08-31

    We report the growth and characterization of III-nitride ternary thin films (Al{sub x}Ga{sub 1−x}N, In{sub x}Al{sub 1−x}N and In{sub x}Ga{sub 1−x}N) at ≤ 500 °C by plasma assisted atomic layer epitaxy (PA-ALE) over a wide stoichiometric range including the range where phase separation has been an issue for films grown by molecular beam epitaxy and metal organic chemical vapor deposition. The composition of these ternaries was intentionally varied through alterations in the cycle ratios of the III-nitride binary layers (AlN, GaN, and InN). By this digital alloy growth method, we are able to grow III-nitride ternaries by PA-ALE over nearly the entire stoichiometry range including in the spinodal decomposition region (x = 15–85%). These early efforts suggest great promise of PA-ALE at low temperatures for addressing miscibility gap challenges encountered with conventional growth methods and realizing high performance optoelectronic and electronic devices involving ternary/binary heterojunctions, which are not currently possible. - Highlights: • III-N ternaries grown at ≤ 500 °C by plasma assisted atomic layer epitaxy • Growth of InGaN and AlInN in the spinodal decomposition region (15–85%) • Epitaxial, smooth and uniform III-N film growth at low temperatures.

  8. Growth and characterization of III-N ternary thin films by plasma assisted atomic layer epitaxy at low temperatures

    International Nuclear Information System (INIS)

    Nepal, Neeraj; Anderson, Virginia R.; Hite, Jennifer K.; Eddy, Charles R.

    2015-01-01

    We report the growth and characterization of III-nitride ternary thin films (Al x Ga 1−x N, In x Al 1−x N and In x Ga 1−x N) at ≤ 500 °C by plasma assisted atomic layer epitaxy (PA-ALE) over a wide stoichiometric range including the range where phase separation has been an issue for films grown by molecular beam epitaxy and metal organic chemical vapor deposition. The composition of these ternaries was intentionally varied through alterations in the cycle ratios of the III-nitride binary layers (AlN, GaN, and InN). By this digital alloy growth method, we are able to grow III-nitride ternaries by PA-ALE over nearly the entire stoichiometry range including in the spinodal decomposition region (x = 15–85%). These early efforts suggest great promise of PA-ALE at low temperatures for addressing miscibility gap challenges encountered with conventional growth methods and realizing high performance optoelectronic and electronic devices involving ternary/binary heterojunctions, which are not currently possible. - Highlights: • III-N ternaries grown at ≤ 500 °C by plasma assisted atomic layer epitaxy • Growth of InGaN and AlInN in the spinodal decomposition region (15–85%) • Epitaxial, smooth and uniform III-N film growth at low temperatures

  9. Epitaxial growth and magnetic properties of Fe4-xMnxN thin films grown on MgO(0 0 1) substrates by molecular beam epitaxy

    Science.gov (United States)

    Anzai, Akihito; Takata, Fumiya; Gushi, Toshiki; Toko, Kaoru; Suemasu, Takashi

    2018-05-01

    Epitaxial Fe4-xMnxN (x = 0, 1, 2, 3, and 4) thin films were successfully grown on MgO(0 0 1) single-crystal substrates by molecular beam epitaxy, and their crystalline qualities and magnetic properties were investigated. It was found that the lattice constants of Fe4-xMnxN obtained from X-ray diffraction measurement increased with the Mn content. The ratio of the perpendicular lattice constant c to the in-plane lattice constant a of Fe4-xMnxN was found to be about 0.99 at x ⩾ 2. The magnetic properties evaluated using a vibrating sample magnetometer at room temperature revealed that all of the Fe4-xMnxN films exhibited ferromagnetic behavior regardless of the value of x. In addition, the saturation magnetization decreased non-linearly as the Mn content increased. Finally, FeMn3N and Mn4N exhibited perpendicular anisotropy and their uniaxial magnetic anisotropy energies were 2.2 × 105 and 7.5 × 105 erg/cm3, respectively.

  10. Uniaxial stress influence on electrical conductivity of thin epitaxial lanthanum-strontium manganite films

    Energy Technology Data Exchange (ETDEWEB)

    Stankevič, V., E-mail: wstan@pfi.lt [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Šimkevičius, Č.; Balevičius, S.; Žurauskienė, N. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Cimmperman, P. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Abrutis, A. [Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania); Plaušinaitienė, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania)

    2013-07-01

    This is a study of the influence of external uniaxial mechanical strains on the transport properties of thin epitaxial La{sub 0.83}Sr{sub 0.17}MnO{sub 3} (LSMO) films. Our measurements were carried out using standard isosceles triangle-shaped cantilever. Films which were tensed in-plane or compressed or were subjected to both tension and compression strains were grown onto SrTiO{sub 3} (STO), LaAlO{sub 3} (LAO) and (001) NdGaO{sub 3} (NGO) substrates, respectively. It was found that for thin films (less than 100 nm), the uniaxial compression of such films which were initially tensed in-plane (grown onto STO substrates) produces a decrease of their resistance, whereas the compression of initially compressed films (on LAO substrates) produces an increase of the films' resistance. The same results were obtained for LSMO films grown onto (001) NGO substrates when they were compressed along the [010] and [100] directions, respectively. For thicker films (more than 100 nm), the resistance behavior after uniaxial compression was found to be identical to that produced by hydrostatic compression, namely, the resistance decreases irrespective of the substrate. These experiments also reveal an increase of resistance and a shift of metal–insulator transition temperature T{sub m} to lower temperatures corresponding to a decrease of the film thickness. The occurrence of this effect is also independent of the kind of substrate used. Thus it was concluded that the influence of film thickness on its resistance as well as on the behavior of such films while under external uniaxial compression cannot be explained fully by only the presence of residual stress in these films. A possible reason is that the inhomogeneous distribution of the mechanical stresses in the films can lead to the appearance of two conductivity phases, each having a different mechanism. The results which were obtained when these films were subjected to hydrostatic compression were also explained by this

  11. EuO and Gd-doped EuO thin films. Epitaxial growth and properties

    International Nuclear Information System (INIS)

    Sutarto, Ronny

    2009-01-01

    quality of many of the doped EuO samples used in the past bulk studies. The focus of this thesis is on the preparation and the properties of high-quality single-crystalline EuO and Gd-doped EuO thin films. The so-called Eu-distillation-assisted molecular beam epitaxy (MBE) has been employed to achieve full control of the stoichiometry. The films have been epitaxially grown on yttria-stabilized cubic zirconia (YSZ) (001) substrates. By a systematic variation of the oxygen deposition rates, we have been able to observe sustained oscillations in the intensity of the reflection high-electron energy diffraction (RHEED) pattern during growth. We thus have demonstrated that layer-by-layer growth has been achieved for the first time. We also have confirmed that YSZ indeed supplies oxygen during the initial stages of growth, yet the EuO stoichiometry can still be well maintained. In the case of Gd-doped EuO films, the presence of Gd even helps to stabilize the layer-by-layer growth mode. It is important to achieve this growth mode, since it enables the preparation of films with very smooth and at surfaces. This in turn facilitates the capping of the films with a thin Al overlayer in order to protect the films against degradation under ambient conditions. More important, the smoothness of the lm will enable the preparation of high quality device structures. By using ex-situ soft x-ray absorption spectroscopy (XAS) at the Eu and Gd M 4,5 edges, we have confirmed that the films are completely free from Eu 3+ contaminants, and we were able to determine reliably the actual Gd concentration. This actual Gd concentration could in fact significantly deviate from the nominal Gd/Eu evaporation ratio. From magnetization and susceptibility measurements, we found the Curie temperature to increase smoothly as a function of doping from 69 K up to a maximum of 125 K, all with a saturation moment of 7 μB. A threshold behavior was not observed for Gd concentrations as low as 0.2 %. Analysis of the

  12. EuO and Gd-doped EuO thin films. Epitaxial growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Sutarto, Ronny

    2009-07-06

    this respect the quality of many of the doped EuO samples used in the past bulk studies. The focus of this thesis is on the preparation and the properties of high-quality single-crystalline EuO and Gd-doped EuO thin films. The so-called Eu-distillation-assisted molecular beam epitaxy (MBE) has been employed to achieve full control of the stoichiometry. The films have been epitaxially grown on yttria-stabilized cubic zirconia (YSZ) (001) substrates. By a systematic variation of the oxygen deposition rates, we have been able to observe sustained oscillations in the intensity of the reflection high-electron energy diffraction (RHEED) pattern during growth. We thus have demonstrated that layer-by-layer growth has been achieved for the first time. We also have confirmed that YSZ indeed supplies oxygen during the initial stages of growth, yet the EuO stoichiometry can still be well maintained. In the case of Gd-doped EuO films, the presence of Gd even helps to stabilize the layer-by-layer growth mode. It is important to achieve this growth mode, since it enables the preparation of films with very smooth and at surfaces. This in turn facilitates the capping of the films with a thin Al overlayer in order to protect the films against degradation under ambient conditions. More important, the smoothness of the lm will enable the preparation of high quality device structures. By using ex-situ soft x-ray absorption spectroscopy (XAS) at the Eu and Gd M{sub 4,5} edges, we have confirmed that the films are completely free from Eu{sup 3+} contaminants, and we were able to determine reliably the actual Gd concentration. This actual Gd concentration could in fact significantly deviate from the nominal Gd/Eu evaporation ratio. From magnetization and susceptibility measurements, we found the Curie temperature to increase smoothly as a function of doping from 69 K up to a maximum of 125 K, all with a saturation moment of 7 {mu}B. A threshold behavior was not observed for Gd concentrations

  13. Epitaxial growth of YBa2Cu3O7-δ thin films on LiNbO3 substrates

    International Nuclear Information System (INIS)

    Lee, S.G.; Koren, G.; Gupta, A.; Segmuller, A.; Chi, C.C.

    1989-01-01

    In situ epitaxial growth of YBa 2 Cu 3 O 7-δ thin films on Y-cut LiNbO 3 substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp ( c (R=0) of 92 K. High critical current density of J c (77 K)=2x10 5 A/cm 2 is observed, which is in accordance with epitaxial growth. Film orientation observed from x-ray diffraction spectra indicates that the c axis is normal to the substrate plane and the a axis is at 45 degree to the [11.0] direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane

  14. Resistivity Effects of Cation Ordering in Highly-Doped La2-xSrxCu4 Epitaxial Thin Films

    Science.gov (United States)

    Burquest, Franklin; Marmol, Rodrigo; Cox, Nicholas; Nelson-Cheeseman, Brittany

    Highly-doped La2-xSrxCuO4 (LSCO) films (0.5 causes internal polar electrostatic forces, which have been shown to cause stretching of the apical oxygen bond in analogous epitaxial nickelate films. Thin film samples are grown concurrently to minimize extraneous effects on film structure and properties. Atomic force microscopy and x-ray reflectivity demonstrate that the films are single crystalline, epitaxial, and smooth. X-ray diffraction is used to measure the c-axis of the films as a function of doping and dopant cation ordering. Electrical transport data of the ordered samples is compared with transport data of conventional disordered cation samples. Preliminary data indicates significant differences in resistivity at both 300K and 10K between the cation-ordered and cation-disordered samples. This work indicates that dopant cation ordering within the layered cuprates could significantly modify the conduction mechanisms at play in these materials.

  15. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  16. Epitaxial growth and control of the sodium content in Na{sub x}CoO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Sandra; Komissinskiy, Philipp [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Major, Marton [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); WIGNER RCP, RMKI, H-1525 Budapest, P.O.B. 49 (Hungary); Donner, Wolfgang [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Alff, Lambert, E-mail: alff@oxide.tu-darmstadt.de [Institute for Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2013-10-31

    Single-phase c-axis oriented Na{sub x}CoO{sub 2} thin films were grown on (001) SrTiO{sub 3} single-crystal substrates, using pulsed laser deposition. X-ray diffraction analysis indicates the epitaxial growth of Na{sub x}CoO{sub 2} thin films in two domains, rotated in-plane by 15 and 45 degrees relative to [100] SrTiO{sub 3}. The sodium stoichiometry x of the films can be controlled in a range of 0.38 < x < 0.84 by in-situ post-deposition annealing the Na{sub x}CoO{sub 2} films at 720 – 760 °C in oxygen for 10 – 30 min. γ - Na{sub x}CoO{sub 2} films are obtained with a full width at half maximum of the (002) Na{sub x}CoO{sub 2} rocking curve below 0.2 degrees. The post-deposition annealing can substitute commonly used chemical deintercalation of Na which is typically associated with a loss in crystallinity. - Highlights: • Single phase Na{sub x}CoO{sub 2} thin films grown by pulsed laser deposition • Epitaxial relations of Na{sub x}CoO{sub 2} thin films on (001) SrTiO{sub 3} substrates • Multi-domain thin films • Control of sodium content by in-situ annealing of Na{sub x}CoO{sub 2} thin films.

  17. Epitaxial growth and structural characterization of Pb(Fe1/2Nb1/2)O3 thin films

    International Nuclear Information System (INIS)

    Peng, W.; Lemee, N.; Holc, J.; Kosec, M.; Blinc, R.; Karkut, M.G.

    2009-01-01

    We have grown lead iron niobate thin films with composition Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) on (0 0 1) SrTiO 3 substrates by pulsed laser deposition. The influence of the deposition conditions on the phase purity was studied. Due to similar thermodynamic stability spaces, a pyrochlore phase often coexists with the PFN perovskite phase. By optimizing the kinetic parameters, we succeeded in identifying a deposition window which resulted in epitaxial perovskite-phase PFN thin films with no identifiable trace of impurity phases appearing in the X-ray diffractograms. PFN films having thicknesses between 20 and 200 nm were smooth and epitaxially oriented with the substrate and as demonstrated by RHEED streaks which were aligned with the substrate axes. X-ray diffraction showed that the films were completely c-axis oriented and of excellent crystalline quality with low mosaicity (X-ray rocking curve FWHM≤0.09 deg.). The surface roughness of thin films was also investigated by atomic force microscopy. The root-mean-square roughness varies between 0.9 nm for 50-nm-thick films to 16 nm for 100-nm-thick films. We also observe a correlation between grain size, surface roughness and film thickness.

  18. Pseudomorphic growth of organic semiconductor thin films driven by incommensurate epitaxy

    International Nuclear Information System (INIS)

    Sassella, A.; Campione, M.; Raimondo, L.; Borghesi, A.; Bussetti, G.; Cirilli, S.; Violante, A.; Goletti, C.; Chiaradia, P.

    2009-01-01

    A stable pseudomorphic phase of α-quaterthiophene, a well known organic semiconductor, is obtained by growing films with organic molecular beam epitaxy (OMBE) on a single crystal of another organic semiconductor, namely, tetracene. The structural characteristics of the new phase are investigated by monitoring in situ the OMBE process by reflectance anisotropy spectroscopy; thus assessing that incommensurate epitaxy is in this case, the driving force for tuning the molecular packing in organic molecular films and in turn, their solid state properties

  19. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    International Nuclear Information System (INIS)

    Wang, J. S.; Shen, J. L.; Chen, W. J.; Tsai, Y. H.; Wang, H. H.; Yang, C. S.; Chen, R. H.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm 2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 deg. C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  20. Advanced fabrication method for the preparation of MOF thin films: Liquid-phase epitaxy approach meets spin coating method.

    KAUST Repository

    Chernikova, Valeriya

    2016-07-14

    Here we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method was implemented to generate MOF thin films in a high-throughput fashion. Advantageously, this approach offers a great prospective to cost-effectively construct thin-films with a significantly shortened preparation time and a lessened chemicals and solvents consumption, as compared to the conventional LPE-process. Certainly, this new spin-coating approach has been implemented successfully to construct various MOF thin films, ranging in thickness from a few micrometers down to the nanometer scale, spanning 2-D and 3-D benchmark MOF materials including Cu2(bdc)2•xH2O, Zn2(bdc)2•xH2O, HKUST-1 and ZIF-8. This method was appraised and proved effective on a variety of substrates comprising functionalized gold, silicon, glass, porous stainless steel and aluminum oxide. The facile, high-throughput and cost-effective nature of this approach, coupled with the successful thin film growth and substrate versatility, represents the next generation of methods for MOF thin film fabrication. Thereby paving the way for these unique MOF materials to address a wide range of challenges in the areas of sensing devices and membrane technology.

  1. A novel epitaxially grown LSO-based thin-film scintillator for micro-imaging using hard synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Douissard, P.A.; Martin, T.; Chevalier, V.; Rack, A. [European Synchrotron Radiat Facil, F-38043 Grenoble, (France); Cecilia, A.; Baumbach, T.; Rack, A. [Karlsruhe Inst Technol ANKA, D-76021 Karlsruhe, (Germany); Couchaud, M. [CEA LETI, F-38054 Grenoble, (France); Dupre, K. [FEE GmbH, D-55743 Idar Oberstein, (Germany); Kuhbacher, M. [Helmholtz Zentrum Berlin Mat and Energie, D-14109 Berlin, (Germany)

    2010-07-01

    The efficiency of high-resolution pixel detectors for hard X-rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron-based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency a novel scintillator based on doped Lu{sub 2}SiO{sub 5} (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO-based thin crystal together with the high stopping power of the material allows for high-performance indirect X-ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible-light and the afterglow are investigated. A set-up to study the effect of the thin-film scintillator's temperature on its conversion efficiency is described as well it delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X-ray imaging systems based on different diffraction-limited visible-light optics and CCD cameras using among others LSO-based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high-resolution computed tomography for life sciences. (authors)

  2. As-free pnictide LaNi{sub 1-x}Sb{sub 2} thin films grown by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Retzlaff, Reiner; Buckow, Alexander; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany)

    2012-07-01

    We use reactive molecular beam epitaxy (RMBE) as synthesis technique for the search of arsenic free pnictide superconductors. Epitaxial thin films of LaNi{sub 1-x}Sb{sub 2} were grown on (100)MgO substrates from elemental sources by simultaneous evaporation of high purity La, Ni and Sb metals by e-gun. The LaNi{sub 1-x}Sb{sub 2} thin films grow epitaxially and are (00l) oriented with high crystalline quality, as evident from RHEED and X-Ray diffraction studies. The Ni deficient LaNi{sub 1-x}Sb{sub 2} thin films show metallic behavior with a room temperature resistivity of 110 {mu}{Omega} cm, while the stoichiometric compound is a semiconductor/insulator. The isostructural compound with Bi as pnictide shows a superconducting transition with a T{sub C}(0) of 3.1 K.

  3. Highly Crystalline C8-BTBT Thin-Film Transistors by Lateral Homo-Epitaxial Growth on Printed Templates.

    Science.gov (United States)

    Janneck, Robby; Pilet, Nicolas; Bommanaboyena, Satya Prakash; Watts, Benjamin; Heremans, Paul; Genoe, Jan; Rolin, Cedric

    2017-11-01

    Highly crystalline thin films of organic semiconductors offer great potential for fundamental material studies as well as for realizing high-performance, low-cost flexible electronics. The fabrication of these films directly on inert substrates is typically done by meniscus-guided coating techniques. The resulting layers show morphological defects that hinder charge transport and induce large device-to-device variability. Here, a double-step method for organic semiconductor layers combining a solution-processed templating layer and a lateral homo-epitaxial growth by a thermal evaporation step is reported. The epitaxial regrowth repairs most of the morphological defects inherent to meniscus-guided coatings. The resulting film is highly crystalline and features a mobility increased by a factor of three and a relative spread in device characteristics improved by almost half an order of magnitude. This method is easily adaptable to other coating techniques and offers a route toward the fabrication of high-performance, large-area electronics based on highly crystalline thin films of organic semiconductors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Growth of epitaxial Pt thin films on (0 0 1) SrTiO{sub 3} by rf magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kahsay, A. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Polo, M.C., E-mail: mcpolo@ub.edu [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Ferrater, C.; Ventura, J. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Rebled, J.M. [Departament d’Electrònica, Universitat de Barcelona Institut de Nanociència i Nanotecnologia IN 2UB, 08028 Barcelona (Spain); Varela, M. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain)

    2014-07-01

    The growth of platinum thin film by rf magnetron sputtering on SrTiO{sub 3}(0 0 1) substrates for oxide based devices was investigated. Platinum films grown at temperatures higher than 750 °C were epitaxial ([1 0 0]Pt(0 0 1)//[1 0 0]STO(0 0 1)), whereas at lower temperatures Pt(1 1 1) films were obtained. The surface morphology of the Pt films showed a strong dependence on the deposition temperature as was revealed by atomic force microscopy (AFM). At elevated temperatures there is a three-dimensional (3D) growth of rectangular atomically flat islands with deep boundaries between them. On the other hand, at low deposition temperatures, a two-dimensional (2D) layered growth was observed. The transition from 2D to 3D growth modes was observed that occurs for temperatures around 450 °C. The obtained epitaxial thin films also formed an atomically sharp interface with the SrTiO{sub 3}(0 0 1) substrate as confirmed by HRTEM.

  5. Epitaxial strain-engineered self-assembly of magnetic nanostructures in FeRh thin films

    International Nuclear Information System (INIS)

    Witte, Ralf; Kruk, Robert; Molinari, Alan; Wang, Di; Brand, Richard A; Hahn, Horst; Schlabach, Sabine; Provenzano, Virgil

    2017-01-01

    In this paper we introduce an innovative bottom–up approach for engineering self-assembled magnetic nanostructures using epitaxial strain-induced twinning and phase separation. X-ray diffraction, 57 Fe Mössbauer spectroscopy, scanning tunneling microscopy, and transmission electron microscopy show that epitaxial films of a near-equiatomic FeRh alloy respond to the applied epitaxial strain by laterally splitting into two structural phases on the nanometer length scale. Most importantly, these two structural phases differ with respect to their magnetic properties, one being paramagnetic and the other ferromagnetic, thus leading to the formation of a patterned magnetic nanostructure. It is argued that the phase separation directly results from the different strain-dependence of the total energy of the two competing phases. This straightforward relation directly enables further tailoring and optimization of the nanostructures’ properties. (paper)

  6. Epitaxial effects in thin films of high-Tc cuprates with the K2NiF4 structure

    Science.gov (United States)

    Naito, Michio; Sato, Hisashi; Tsukada, Akio; Yamamoto, Hideki

    2018-03-01

    La2-xSrxCuO4 (LSCO) and La2-xBaxCuO4 (LBCO) have been recognized as the archetype materials of "hole-doped" high-Tc superconductors. Their crystal structures are relatively simple with a small number of constituent cation elements. In addition, the doping level can be varied by the chemical substitution over a wide range enough to obtain the full spectrum of doping-dependent electronic and magnetic properties. These attractive features have dedicated many researchers to thin-film growth of LSCO and LBCO. The critical temperature (Tc) of LSCO and LBCO is sensitive to strain as manifested by a positive pressure coefficient of Tc in bulk samples. In general, films are strained if they are grown on lattice-mismatched substrates (epitaxial strain). Early attempts (before 1997) at the growth of LSCO and LBCO films resulted in depressed Tc below 30 K as they were grown on a commonly used SrTiO3 substrate (in-plane lattice parameter asub = 3.905 Å): the in-plane lattice parameters of LSCO and LBCO are ≤3.80 Å, and hence tensile epitaxial strain is introduced. The situation was changed by the use of LaSrAlO4 substrates with a slightly shorter in-plane lattice constant (asub = 3.756 Å). On LaSrAlO4 substrates, the Tc reaches 45 K in La1.85Sr0.15CuO4, 47 K in La1.85Ba0.15CuO4, and 56 K in ozone-oxidized La2CuO4+δ films, substantially higher than the Tc's of the bulk compounds. The Tc increase in La1.85Sr0.15CuO4 films on LaSrAlO4 and decrease on SrTiO3 are semi-quantitatively in accord with the phenomenological estimations based on the anisotropic strain coefficients of Tc (dTc/dεi). In this review article, we describe the growth and properties of films of cuprates having the K2NiF4 structure, mainly focusing on the increase/decrease of Tc by epitaxial strain and quasi-stable phase formation by epitaxial stabilization. We further extract the structural and/or physical parameters controlling Tc toward microscopic understanding of the variation of Tc by epitaxial strain.

  7. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Hong, Seungbum; Bowden, Mark E.; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R.; Comes, Ryan B.; Ramuhalli, Pradeep; Henager, Charles H.

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200°C due to the low Curie temperature of the piezoelectric material. High temperature piezoelectric materials such as La2Ti2O7 (LTO) would facilitate the development of high-temperature sensors if the piezoelectric coupling coefficient could be maximized. We have deposited epitaxial LTO films on SrTiO3(001), SrTiO3(110), and rutile TiO2(110) substrates by pulsed laser deposition, and show that the crystalline orientation of the LTO film, and thus its piezoelectric coupling direction, can be controlled by epitaxial matching to the substrate. The structure and phase purity of the films were investigated by x-ray diffraction and scanning transmission electron microscopy. To characterize the piezoelectric properties, piezoresponse force microscopy was used to measure the in-plane and out-of-plane piezoelectric coupling in the films. We find that the strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric crystalline direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO2(110) results in epitaxial La2/3TiO3, an orthorhombic perovskite of interest as a microwave dielectric material. La2/3TiO3 can be difficult to stabilize in bulk form, and epitaxial deposition has not been previously reported. These results confirm that control of the crystalline orientation of LTO-based materials can increase the out-of-plane strength of its piezoelectric coupling, which can be exploited in piezoelectric devices.

  8. Superconducting thin films of As-free pnictide LaPd{sub 1-x}Sb{sub 2} grown by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Retzlaff, Reiner; Buckow, Alexander; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany)

    2013-07-01

    We use reactive molecular beam epitaxy as synthesis technique for the search of arsenic free pnictide superconductors. Epitaxial thin films of LaPd{sub 1-x}Sb{sub 2} were grown on (100) MgO substrates from elemental sources by simultaneous evaporation of high purity La, Pd and Sb metals by e-gun. LaPd{sub 1-x}Sb{sub 2} belongs to a novel class of pnictide superconductors with a peculiar pnictide square net layer. Previously, we have reported epitaxial growth of isostructural Bi based compounds. The substitution of Bi by Sb leads to thin films with metallic behavior and room temperature resistivity of about 85 μΩ cm. The highest observed transition temperature T{sub c} inLaPd{sub 1-x}Sb{sub 2} is 3.1 K and does not depend on x. We discuss strategies to increase T{sub c} in this pnictide subfamily.

  9. Misfit strain-film thickness phase diagrams and related electromechanical properties of epitaxial ultra-thin lead zirconate titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Q.Y.; Mahjoub, R. [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Alpay, S.P. [Materials Science and Engineering Program and Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States); Nagarajan, V., E-mail: nagarajan@unsw.edu.au [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2010-02-15

    The phase stability of ultra-thin (0 0 1) oriented ferroelectric PbZr{sub 1-x}Ti{sub x}O{sub 3} (PZT) epitaxial thin films as a function of the film composition, film thickness, and the misfit strain is analyzed using a non-linear Landau-Ginzburg-Devonshire thermodynamic model taking into account the electrical and mechanical boundary conditions. The theoretical formalism incorporates the role of the depolarization field as well as the possibility of the relaxation of in-plane strains via the formation of microstructural features such as misfit dislocations at the growth temperature and ferroelastic polydomain patterns below the paraelectric-ferroelectric phase transformation temperature. Film thickness-misfit strain phase diagrams are developed for PZT films with four different compositions (x = 1, 0.9, 0.8 and 0.7) as a function of the film thickness. The results show that the so-called rotational r-phase appears in a very narrow range of misfit strain and thickness of the film. Furthermore, the in-plane and out-of-plane dielectric permittivities {epsilon}{sub 11} and {epsilon}{sub 33}, as well as the out-of-plane piezoelectric coefficients d{sub 33} for the PZT thin films, are computed as a function of misfit strain, taking into account substrate-induced clamping. The model reveals that previously predicted ultrahigh piezoelectric coefficients due to misfit-strain-induced phase transitions are practically achievable only in an extremely narrow range of film thickness, composition and misfit strain parameter space. We also show that the dielectric and piezoelectric properties of epitaxial ferroelectric films can be tailored through strain engineering and microstructural optimization.

  10. Effect of carbon additive on microstructure evolution and magnetic properties of epitaxial FePt (001) thin films

    International Nuclear Information System (INIS)

    Ding, Y.F.; Chen, J.S.; Liu, E.; Lim, B.C.; Hu, J.F.; Liu, B.

    2009-01-01

    FePt:C thin films were deposited on CrRu underlayers by DC magnetron co-sputtering. The effects of C content, FePt:C film thickness and substrate temperature on the microstructural and magnetic properties of the epitaxial FePt (001) films were studied. Experimental results showed that even with 30 vol.% C doping, the FePt films could keep a (001) preferred orientation at 350 deg. C . When a FePt:C film was very thin (< 5 nm), the film had a continuous microstructure instead of a granual structure with C diffused onto the film surface. With further increased film thickness, the film started to nucleate and formed a column microstructure over continuous FePt films. A strong exchange coupling in the FePt:C films was believed to be due to the presence of a thin continuous FePt layer attributed to the carbon diffusion during the initial stage of the FePt:C film growth. Despite the presence of a strong exchange coupling in the FePt:C (20 vol.% C) film, the SNR ratio of the FePt:C media was about 10 dB better than that of the pure FePt media. The epitaxial growth of the FePt:C films on the Pt layers was observed from high resolution TEM cross sectional images even for the films grown at about 200 deg. C . The TEM images did not show an obvious change in the morphology of the FePt:C films deposited at different temperatures (from 200 deg. C to 350 deg. C ), though the ordering degree and coercivity of the films increased with increased substrate temperature

  11. Photon confinement in high-efficiency, thin-film III-V solar cells obtained by epitaxial lift-off

    International Nuclear Information System (INIS)

    Schermer, J.J.; Bauhuis, G.J.; Mulder, P.; Haverkamp, E.J.; Deelen, J. van; Niftrik, A.T.J. van; Larsen, P.K.

    2006-01-01

    Using the epitaxial lift-off (ELO) technique, a III-V device structure can be separated from its GaAs substrate by selective wet etching of a thin release layer. The thin-film structures obtained by the ELO process can be cemented or van der Waals bonded on arbitrary smooth surface carriers for further processing. It is shown that the ELO method, initially able to separate millimetre-sized GaAs layers with a lateral etch rate of about 1 mm/h, has been developed to a process capable to free the entire 2-in. epitaxial structures from their substrates with etch rates up to 30 mm/h. With these characteristics the method has a large potential for the production of high efficiency thin-film solar cells. By choosing the right deposition and ELO strategy, the thin-film III-V cells can be adequately processed on both sides allowing for an entire range of new cell structures. In the present work, the performance of semi-transparent bifacial solar cells, produced by the deposition of metal grid contacts on both sides, was evaluated. Reflection of light at the rear side of the bifacial GaAs solar cells was found to result in an enhanced collection probability of the photon-induced carriers compared to that of regular III-V cells on a GaAs substrate. To enhance this effect, thin-film GaAs cells with gold mirror back contacts were prepared. Even in their present premature stage of development, these single-junction thin-film cells reached a record efficiency of 24.5% which is already very close to the 24.9% efficiency that was obtained with a regular GaAs cell on a GaAs substrate. From this it could be concluded that, as a result of the photon confinement, ELO cells require a significantly thinner base layer than regular GaAs cells while at the same time they have the potential to reach a higher efficiency

  12. Enhanced piezoelectric properties of (110)-oriented PbZr1−xTixO3 epitaxial thin films on silicon substrates at shifted morphotropic phase boundary

    NARCIS (Netherlands)

    Wan, X.; Houwman, Evert Pieter; Steenwelle, Ruud Johannes Antonius; van Schaijk, R.; Nguyen, Duc Minh; Dekkers, Jan M.; Rijnders, Augustinus J.H.M.

    2014-01-01

    Piezoelectrical, ferroelectrical, and structural properties of epitaxial pseudocubic (110)pc oriented 500 nm thick PbZr1−xTixO3 thin films, prepared by pulsed laser deposition on (001) silicon substrates, were measured as a function of composition. The dependence of the measurement data on the Ti

  13. Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: nukaga@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 {sup 0}C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90{sup 0} each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

  14. Epitaxial growth of fcc-CoxNi100-x thin films on MgO(110) single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nukaga, Yuri; Sato, Yoichi; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    Co x Ni 100-x (x=100, 80, 20, 0 at. %) epitaxial thin films were prepared on MgO(110) single-crystal substrates heated at 300 deg. C by ultrahigh vacuum molecular beam epitaxy. The growth mechanism is discussed based on lattice strain and crystallographic defects. CoNi(110) single-crystal films with a fcc structure are obtained for all compositions. Co x Ni 100-x film growth follows the Volmer-Weber mode. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the Co x Ni 100-x films are in agreement within ±0.5% with the values of the respective bulk Co x Ni 100-x crystals, suggesting that the strain in the film is very small. High-resolution cross-sectional transmission microscopy shows that an atomically sharp boundary is formed between a Co(110) fcc film and a MgO(110) substrate, where periodical misfit dislocations are preferentially introduced in the film at the Co/MgO interface. The presence of such periodical misfit dislocations relieves the strain caused by the lattice mismatch between the film and the substrate.

  15. Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

    International Nuclear Information System (INIS)

    Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90 0 each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

  16. Magneto-transport and thermoelectric properties of epitaxial FeSb{sub 2} thin film on MgO substrate

    Energy Technology Data Exchange (ETDEWEB)

    Duong, Anh Tuan; Rhim, S. H., E-mail: sonny@ulsan.ac.kr; Shin, Yooleemi; Nguyen, Van Quang; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 680-749 (Korea, Republic of)

    2015-01-19

    We report magneto-transport and thermoelectric properties of FeSb{sub 2} thin film epitaxially grown on the MgO substrate using molecular beam epitaxy. The film exhibits compressive strain of 1.74% owing to large lattice mismatch, whose physical consequences are nontrivial. Magnetic phase has been changed from diamagnetic in bulk, as evidenced by anomalous Hall effect (AHE) and negative magneto-resistance (MR). The FeSb{sub 2} film is semiconducting without any metallic transition unlike the bulk counterpart. In particular, hysteresis in MR with distinct feature of AHE is evident with coercive field of 500 and 110 Oe for T = 20 and 50 K, respectively. Furthermore, from the Seebeck coefficients and temperature dependence of the resistivity, it is evident that the film is semiconducting with small band gap: 3.76 meV for T < 40 K and 13.48 meV for T > 40 K, respectively, where maximum thermoelectric power factor of 12 μV/cm·K at T = 50 K.

  17. Thin film evolution equations from (evaporating) dewetting liquid layers to epitaxial growth

    International Nuclear Information System (INIS)

    Thiele, U

    2010-01-01

    In the present contribution we review basic mathematical results for three physical systems involving self-organizing solid or liquid films at solid surfaces. The films may undergo a structuring process by dewetting, evaporation/condensation or epitaxial growth, respectively. We highlight similarities and differences of the three systems based on the observation that in certain limits all of them may be described using models of similar form, i.e. time evolution equations for the film thickness profile. Those equations represent gradient dynamics characterized by mobility functions and an underlying energy functional. Two basic steps of mathematical analysis are used to compare the different systems. First, we discuss the linear stability of homogeneous steady states, i.e. flat films, and second the systematics of non-trivial steady states, i.e. drop/hole states for dewetting films and quantum-dot states in epitaxial growth, respectively. Our aim is to illustrate that the underlying solution structure might be very complex as in the case of epitaxial growth but can be better understood when comparing the much simpler results for the dewetting liquid film. We furthermore show that the numerical continuation techniques employed can shed some light on this structure in a more convenient way than time-stepping methods. Finally we discuss that the usage of the employed general formulation does not only relate seemingly unrelated physical systems mathematically, but does allow as well for discussing model extensions in a more unified way.

  18. Controlling plasmonic properties of epitaxial thin films of indium tin oxide in the near-infrared region

    Science.gov (United States)

    Kamakura, R.; Fujita, K.; Murai, S.; Tanaka, K.

    2015-06-01

    Epitaxial thin films of indium tin oxide (ITO) were grown on yttria-stabilized zirconia single-crystal substrates by using a pulsed laser deposition to examine their plasmonic properties. The dielectric function of ITO was characterized by spectroscopic ellipsometry. Through the concentration of SnO2 in the target, the carrier concentration in the films was modified, which directly leads to the tuning of the dielectric function in the near-infrared region. Variable-angle reflectance spectroscopy in the Kretschmann geometry shows the dip in the reflection spectrum of p-polarized light corresponding to the excitation of surface plasmon polaritions (SPPs) in the near-infrared region. The excitation wavelength of the SPPs was shifted with changing the dielectric functions of ITO, which is reproduced by the calculation using transfer matrix method.

  19. Upper-critical fields of YBa2Cu3O7-δ epitaxial thin films with variable oxygen deficiency δ

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Ossandon, J.G.; Feenstra, R.; Phillips, J.M.; Siegal, M.P.

    1994-01-01

    Fluctuation analysis in the limit of high magnetic fields was performed on three epitaxial thin films of YBa 2 Cu 3 O 7-δ for various oxygen deficiencies δ c2 (T) slope of -1.7 T/K for H parallel c, consistent with previous observations of transport and magnetic properties. Moreover, the 3D scaling showed better convergence than the 2D scaling, which gave relatively low values of H c2 . In contrast, the transitions were not adequately described by either scaling for T c off the 90-K plateau; it is speculated that this is due to an extrinsic broadening of the transitions, possibly due to the lack of a complete percolation path of the ortho-I phase (δ=0)

  20. Normal-state transport parameters of epitaxial thin films of YBa2Cu3O/sub 7-//sub δ/

    International Nuclear Information System (INIS)

    Stormer, H.L.; Levi, A.F.J.; Baldwin, K.W.; Anzlowar, M.; Boebinger, G.S.

    1988-01-01

    We report on a striking correlation in the electrical transport behavior of very high-quality (j/sub c/∼3.4 x 10 6 A/cm 2 at T = 77 K) epitaxial thin films of high-T/sub c/ Y-Ba-Cu-O in the normal state. With increasing superconducting performance, as characterized by the transition temperature, transition-temperature width, and critical current density, the resistivity rho, and the Hall coefficient R/sub H/, both assume remarkably simple temperature dependences rho = αT and R/sub H//sup -1/ = βT leading to a Hall mobility μ/sub H/proportionalT/sup -2/. The magnetoresistance at 10 T is less than Δrho/rho<10/sup -3/. We discuss an extreme two-carrier model to assess the T dependence of R/sub H/. .AE

  1. Epitaxial growth of high temperature superconductors by cathodic sputtering I: thin films of YBaCuO

    International Nuclear Information System (INIS)

    Navacerrada, M.A.; Sefrioui, Z.; Arias, D.; Varela, M.; Loos, G.; Leon, C.; Lucia, M.L.; Santamaria, J.; Sanchez-Quesada, F.

    1998-01-01

    High quality c-oriented YBa 2 Cu 3 O 7 -x thin films have been grown on SrTiO 3 (100)substrates by high pressure sputtering in pure oxygen atmosphere. Low angle X-ray diffraction and atomic force microscopy were performed on films less than 250 angstrom thick showing a plenitude better than one unit cell. Moreover, the structural characterization by means of X ray φ scans showed that growth is epitaxial. The critical temperature has been measured by different ways and was always in the range 89.5-90.5K. the resistance transition is sharper than 1K and the mutual inductance response always shows magnetic losses peaks narrower than 0.3K. Critical current densities are in excess of 10''''6 angstrom/cm''''2 at 77K. (Author) 8 refs

  2. Structure and chemistry of epitaxial ceria thin films on yttria-stabilized zirconia substrates, studied by high resolution electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, Robert, E-mail: bobsinc@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, Sang Chul, E-mail: sclee99@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Shi, Yezhou; Chueh, William C. [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States)

    2017-05-15

    We have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e{sup -}/Å{sup 2}s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering. The ordered structure does not appear at lower lose rates (ca. 2600 e{sup -}/Å{sup 2}s) and can be removed by imaging under 1 mbar oxygen gas in an environmental TEM. EELS confirms that there is both oxygen deficiency and the associated increase in Ce{sup 3+} versus Ce{sup 4+} cations in the ordered domains. In situ high resolution TEM recordings show the formation of the ordered domains as well as atomic migration along the ceria thin film (001) surface. - Highlights: • The local structure and chemistry of ceria can be studied by TEM combined with EELS. • At lower electron, there are no observable changes in the ceria thin films. • At higher dose rates, an ordered phase is created due to oxygen vacancy ordering. • In situ HRTEM shows the oxygen vacancy ordering and the movement of surface atoms.

  3. Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

    Energy Technology Data Exchange (ETDEWEB)

    Okazaki, Sohei [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yang, Chang [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [Tandem Accelerator Complex, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577 (Japan); Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2014-05-30

    InO{sub x}F{sub y} thin films were epitaxially grown on Y-stabilized ZrO{sub 2} (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (T{sub S}), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high T{sub S} (≥ 240 °C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y / (x + y) ∼ 0.3. By decreasing T{sub S}, y / (x + y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at T{sub S} ≤ 150 °C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films. - Highlights: • InO{sub x}F{sub y} epitaxial thin films with high fluorine concentration were grown on Y:ZrO{sub 2}. • Anion composition and structural, optical and transport properties were studied. • Fluorine is topotactically inserted into the oxygen vacancy sites in bixbyite cell. • Bixbyite-like ordering of the anion site occupancy was conserved in y / (x + y) ≤ ∼ 0.3.

  4. Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

    International Nuclear Information System (INIS)

    Okazaki, Sohei; Hirose, Yasushi; Nakao, Shoichiro; Yang, Chang; Harayama, Isao; Sekiba, Daiichiro; Hasegawa, Tetsuya

    2014-01-01

    InO x F y thin films were epitaxially grown on Y-stabilized ZrO 2 (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (T S ), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high T S (≥ 240 °C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y / (x + y) ∼ 0.3. By decreasing T S , y / (x + y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at T S ≤ 150 °C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films. - Highlights: • InO x F y epitaxial thin films with high fluorine concentration were grown on Y:ZrO 2 . • Anion composition and structural, optical and transport properties were studied. • Fluorine is topotactically inserted into the oxygen vacancy sites in bixbyite cell. • Bixbyite-like ordering of the anion site occupancy was conserved in y / (x + y) ≤ ∼ 0.3

  5. Growth of CrTe thin films by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Sreenivasan, M.G.; Hou, X.J.; Teo, K.L.; Jalil, M.B.A.; Liew, T.; Chong, T.C.

    2006-01-01

    We report the growth of Cr 1-δ Te films on (100) GaAs substrates using ZnTe buffer layers by solid-source molecular-beam epitaxial technique. RHEED patterns indicate a clear structural change during the initial stages of deposition. Temperature-dependent magnetization results reveal that different NiAs-related phases of Cr 1-δ Te can be obtained at different substrate temperatures. By varying the film thickness, a metastable zinc blende structure of CrTe could be obtained at lower substrate temperature

  6. Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

    International Nuclear Information System (INIS)

    Sandstrom, R.L.; Giess, E.A.; Gallagher, W.J.; Segmueller, A.; Cooper, E.I.; Chisholm, M.F.; Gupta, A.; Shinde, S.; Laibowitz, R.B.

    1988-01-01

    We demonstrate that lanthanum gallate (LaGaO 3 ) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa 2 Cu 3 O/sub 7-//sub x/, can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant (ε≅25) and low dielectric losses. Epitaxial YBa 2 Cu 3 O/sub 7-//sub x/ films grown on LaGaO 3 single-crystal substrates by three techniques have zero resistance between 87 and 91 K

  7. Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

    Science.gov (United States)

    Sandstrom, R. L.; Giess, E. A.; Gallagher, W. J.; Segmuller, A.; Cooper, E. I.

    1988-11-01

    It is demonstrated that lanthanum gallate (LaGaO3) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa2Cu3O(7-x), can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant and low dielectric losses. Epitaxial YBa2Cu3O(7-x) films grown on LaGaO3 single-crystal substrates by three techniques have zero resistance between 87 and 91 K.

  8. Origin of green luminescence in ZnO thin film grown by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Heo, Y.W.; Norton, D.P.; Pearton, S.J.

    2005-01-01

    The properties of ZnO films grown by molecular-beam epitaxy are reported. The primary focus was on understanding the origin of deep-level luminescence. A shift in deep-level emission from green to yellow is observed with reduced Zn pressure during the growth. Photoluminescence and Hall measurements were employed to study correlations between deep-level/near-band-edge emission and carrier density. With these results, we suggest that the green emission is related to donor-deep acceptor (Zn vacancy V Zn - ) and the yellow to donor-deep acceptor (oxygen vacancy, O i - )

  9. Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Schou, Jørgen

    2011-01-01

    Epitaxial growth of Ce0.8Gd0.2O2(CGO) films on (001) TiO2-terminated SrTiO3 substrates by pulsed laser deposition was investigated using in situ reflective high energy electron diffraction. The initial film growth shows a Stransky–Krastanov growth mode. However, this three-dimensional island...... formation is replaced by a two-dimensional island nucleation during further deposition, which results in atomically smooth CGO films. The obtained high-quality CGO films may be attractive for the electrolyte of solid-oxide fuel cells operating at low temperature....

  10. Broadband nanophotonic waveguides and resonators based on epitaxial GaN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bruch, Alexander W.; Xiong, Chi; Leung, Benjamin; Poot, Menno; Han, Jung; Tang, Hong X., E-mail: hong.tang@yale.edu [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States)

    2015-10-05

    We demonstrate broadband, low loss optical waveguiding in single crystalline GaN grown epitaxially on c-plane sapphire wafers through a buffered metal-organic chemical vapor phase deposition process. High Q optical microring resonators are realized in near infrared, infrared, and near visible regimes with intrinsic quality factors exceeding 50 000 at all the wavelengths we studied. TEM analysis of etched waveguide reveals growth and etch-induced defects. Reduction of these defects through improved material and device processing could lead to even lower optical losses and enable a wideband photonic platform based on GaN-on-sapphire material system.

  11. Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

    Science.gov (United States)

    Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

    2015-08-26

    Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Cariou, R., E-mail: romain.cariou@polytechnique.edu [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); III-V lab a joint laboratory between Alcatel-Lucent Bell Labs France, Thales Research and Technology and CEA-LETI, route de Nozay, 91460, Marcoussis, France. (France); Ruggeri, R. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy); Tan, X.; Nassar, J.; Roca i Cabarrocas, P. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); Mannino, Giovanni [CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy)

    2014-07-15

    We report on unusual low temperature (175 °C) heteroepitaxial growth of germanium thin films using a standard radio-frequency plasma process. Spectroscopic ellipsometry and transmission electron microscopy (TEM) reveal a perfect crystalline quality of epitaxial germanium layers on (100) c-Ge wafers. In addition direct germanium crystal growth is achieved on (100) c-Si, despite 4.2% lattice mismatch. Defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and threading dislocation density (TDD) values as low as 10{sup 6} cm{sup −2} are obtained. Misfit stress is released fast: residual strain of −0.4% is calculated from Moiré pattern analysis. Moreover we demonstrate a striking feature of low temperature plasma epitaxy, namely the fact that crystalline quality improves with thickness without epitaxy breakdown, as shown by TEM and depth profiling of surface TDD.

  13. Fabrication of fully epitaxial magnetic tunnel junctions with a Co2MnSi thin film and a MgO tunnel barrier

    International Nuclear Information System (INIS)

    Kijima, H.; Ishikawa, T.; Marukame, T.; Matsuda, K.-I.; Uemura, T.; Yamamoto, M.

    2007-01-01

    Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with a Co-based full-Heusler alloy Co 2 MnSi (CMS) thin film having the ordered L2 1 structure as a lower electrode, a MgO tunnel barrier, and a Co 50 Fe 50 upper electrode. Reflection high-energy electron diffraction patterns observed in situ for each layer in the MTJ layer structure during fabrication clearly indicated that all layers of the CMS lower electrode, MgO tunnel barrier, and Co 50 Fe 50 upper electrode grew epitaxially. The microfabricated fully epitaxial CMS/MgO/Co 50 Fe 50 MTJs demonstrated relatively high tunnel magnetoresistance ratios of 90% at room temperature and 192% at 4.2 K

  14. Effects of substrate temperature and Cu underlayer thickness on the formation of SmCo5(0001) epitaxial thin films

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    SmCo 5 (0001) epitaxial thin films were prepared on Cu(111) underlayers heteroepitaxially grown on Al 2 O 3 (0001) single-crystal substrates by molecular beam epitaxy. The effects of substrate temperature and Cu underlayer thickness on the crystallographic properties of SmCo 5 (0001) epitaxial films were investigated. The Cu atoms of underlayer diffuse into the SmCo 5 film and substitute the Co sites in SmCo 5 structure forming an alloy compound of Sm(Co,Cu) 5 . The ordered phase formation is enhanced with increasing the substrate temperature and with increasing the Cu underlayer thickness. The Cu atom diffusion into the SmCo 5 film is assisting the formation of Sm(Co,Cu) 5 ordered phase.

  15. Solid phase epitaxial growth of high mobility La:BaSnO_3 thin films co-doped with interstitial hydrogen

    International Nuclear Information System (INIS)

    Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Moram, Michelle A.; Ide, Keisuke; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-01

    This work presents the solid phase epitaxial growth of high mobility La:BaSnO_3 thin films on SrTiO_3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO_3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm"2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO_3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO_3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO_3 thin films were increased to 3 × 10"1"9" cm"−"3 and in La:BaSnO_3 thin films from 6 × 10"1"9" cm"−"3 to 1.5 × 10"2"0" cm"−"3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO_3 electron effective mass of 0.27 ± 0.05 m_0 and an optical mobility of 26 ± 7 cm"2/Vs. As compared to La:BaSnO_3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO_3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

  16. Microstructure of epitaxial thin films of the ferromagnetic shape memory alloy Ni{sub 2}MnGa

    Energy Technology Data Exchange (ETDEWEB)

    Eichhorn, Tobias

    2011-12-09

    This work is concerned with the preparation and detailed characterization of epitaxial thin films of the Heusler compound Ni{sub 2}MnGa. This multiferroic compound is of both technological and scientific interest due to the outstanding magnetic shape memory (MSM) behavior. Huge magnetic-field-induced strains up to 10 % have been observed for single crystals close to a Ni{sub 2}MnGa composition. The effect is based on a redistribution of crystallographic twin variants of tetragonal or orthorhombic symmetry. Under the driving force of the external magnetic field twin boundaries can move through the crystal, which largely affects the macroscopic shape. The unique combination of large reversible strain, high switching frequency and high work output makes the alloy a promising actuator material. Since the MSM effect results from an intrinsic mechanism, MSM devices possess great potential for implementation in microsystems, e.g. microfluidics. So far significant strains, in response to an external magnetic field, have been observed for bulk single crystals and foams solely. In order to take advantage of the effect in applications concepts for miniaturization are needed. The rather direct approach, based on epitaxial thin films, is explored in the course of this work. This involves sample preparation under optimized deposition parameters and fabrication of freestanding single-crystalline films. Different methods to achieve freestanding microstructures such as bridges and cantilevers are presented. The complex crystal structure is extensively studied by means of X-ray diffraction. Thus, the different crystallographic twin variants that are of great importance for the MSM effect are identified. In combination with microscopy the twinning architecture for films of different crystallographic orientation is clarified. Intrinsic blocking effects in samples of (100) orientation are explained on basis of the variant configuration. In contrast, a promising twinning microstructure

  17. Interplay of uniaxial and cubic anisotropy in epitaxial Fe thin films on MgO (001 substrate

    Directory of Open Access Journals (Sweden)

    Srijani Mallik

    2014-09-01

    Full Text Available Epitaxial Fe thin films were grown on annealed MgO(001 substrates at oblique incidence by DC magnetron sputtering. Due to the oblique growth configuration, uniaxial anisotropy was found to be superimposed on the expected four-fold cubic anisotropy. A detailed study of in-plane magnetic hysteresis for Fe on MgO thin films has been performed by Magneto Optic Kerr Effect (MOKE magnetometer. Both single step and double step loops have been observed depending on the angle between the applied field and easy axis i.e. along ⟨100⟩ direction. Domain images during magnetization reversal were captured by Kerr microscope. Domain images clearly evidence two successive and separate 90° domain wall (DW nucleation and motion along cubic easy cum uniaxial easy axis and cubic easy cum uniaxial hard axis, respectively. However, along cubic hard axis two 180° domain wall motion dominate the magnetization reversal process. In spite of having four-fold anisotropy it is essential to explain magnetization reversal mechanism in 0°< ϕ < 90° span as uniaxial anisotropy plays a major role in this system. Also it is shown that substrate rotation can suppress the effect of uniaxial anisotropy superimposed on four-fold anisotropy.

  18. The α-particle excited scintillation response of YAG:Ce thin films grown by liquid phase epitaxy

    International Nuclear Information System (INIS)

    Prusa, Petr; Nikl, Martin; Mares, Jiri A.; Nitsch, Karel; Beitlerova, Alena; Kucera, Miroslav

    2009-01-01

    Y 3 Al 5 O 12 :Ce (YAG:Ce) thin films were grown from PbO-,BaO-, and MoO 3 -based fluxes using the liquid phase epitaxy (LPE) method. Photoelectron yield, its time dependence within 0.5-10 μs shaping time, and energy resolution of these samples were measured under α-particle excitation. For comparison a sample of the Czochralski grown bulk YAG:Ce single crystal was measured as well. Photoelectron yield values of samples grown from the BaO-based flux were found superior to other LPE films and comparable with that of the bulk single crystal. The same is valid also for the time dependence of photoelectron yield. Obtained results are discussed taking into account the influence of the flux and technology used. Additionally, α particle energy deposition in very thin films is modelled and discussed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Study of electronic structure and magnetic properties of epitaxial Co{sub 2}FeAl Heusler Alloy Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Soni, S. [Department of Pure & Applied Physics, University of Kota, Kota 324007 (India); Dalela, S., E-mail: sdphysics@rediffmail.com [Department of Pure & Applied Physics, University of Kota, Kota 324007 (India); Sharma, S.S. [Department of Physics, Govt. Women Engineering College, Ajmer (India); Liu, E.K.; Wang, W.H.; Wu, G.H. [State Key Laboratory for Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Kumar, M. [Department of Physics, Malviya National Institute of Technology, Jaipur-302017 (India); Garg, K.B. [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

    2016-07-25

    This work reports the magnetic and electronic characterization of plane magnetized buried Heusler Co{sub 2}FeAl nano thin films of different thickness by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements. . The spectra on both Fe- and Co L{sub 2,3} edges show a pronounced magnetic dichroic signal in remanence, corresponding to a ferromagnetically-aligned moments on Fe and Co atoms conditioning the peculiar characteristics of the Co{sub 2}FeAl Heusler compound (a half-metallic ferromagnet). The detailed knowledge of the related magnetic and electronic properties of these samples over a wide range of thickness of films are indispensable for achieving a higher tunnel magnetoresistance ratio, and thus for spintronics device applications. - Highlights: • Electronic structure and Magnetic Properties of Epitaxial Co{sub 2}FeAl Heusler Films. • X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). • Fe- and Co L{sub 2,3} edges show a pronounced magnetic dichroic signal in remanence. • Calculated Orbital, Spin and total magnetic moments of Fe and Co for 30 nm Co{sub 2}FeAl thin film. • The total magnetic moment of Fe at L{sub 2,3} edges increases with the thickness of the Co2FeAl films.

  20. Nanoscale monoclinic domains in epitaxial SrRuO3 thin films deposited by pulsed laser deposition

    Science.gov (United States)

    Ghica, C.; Negrea, R. F.; Nistor, L. C.; Chirila, C. F.; Pintilie, L.

    2014-07-01

    In this paper, we analyze the structural distortions observed by transmission electron microscopy in thin epitaxial SrRuO3 layers used as bottom electrodes in multiferroic coatings onto SrTiO3 substrates for future multiferroic devices. Regardless of the nature and architecture of the multilayer oxides deposited on the top of the SrRuO3 thin films, selected area electron diffraction patterns systematically revealed the presence of faint diffraction spots appearing in forbidden positions for the SrRuO3 orthorhombic structure. High-resolution transmission electron microscopy (HRTEM) combined with Geometric Phase Analysis (GPA) evidenced the origin of these forbidden diffraction spots in the presence of structurally disordered nanometric domains in the SrRuO3 bottom layers, resulting from a strain-driven phase transformation. The local high compressive strain (-4% ÷ -5%) measured by GPA in the HRTEM images induces a local orthorhombic to monoclinic phase transition by a cooperative rotation of the RuO6 octahedra. A further confirmation of the origin of the forbidden diffraction spots comes from the simulated diffraction patterns obtained from a monoclinic disordered SrRuO3 structure.

  1. Persistent semi-metal-like nature of epitaxial perovskite CaIrO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit; Jeong, Yoon Hee, E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2015-05-21

    Strong spin-orbit coupled 5d transition metal based ABO{sub 3} oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO{sub 3}. Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO{sub 3} thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics.

  2. Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

    Science.gov (United States)

    Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

    2018-04-01

    Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

  3. Bi-epitaxial YBa{sub 2}Cu{sub 3}O{sub x} Thin Films on Tilted-axes NdGaO{sub 3} Substrates with CeO{sub 2} Seeding Layer

    Energy Technology Data Exchange (ETDEWEB)

    Mozhaev, P B [Institute of Physics and Technology RAS, 117218, Moscow (Russian Federation); Mozhaeva, J E [Institute of Physics and Technology RAS, 117218, Moscow (Russian Federation); Jacobsen, C S [Technical University of Denmark, Physics Department, Lyngby, DK-2800, Denmark (Denmark); Hansen, J Bindslev [Technical University of Denmark, Physics Department, Lyngby, DK-2800, Denmark (Denmark); Bdikin, I K [CICECO, University of Aveiro, Aveiro, 3810-193 (Portugal); Luzanov, V A [Institute of Radio Engineering and Electronics, Moscow, 125009 (Russian Federation); Kotelyanskii, I M [Institute of Radio Engineering and Electronics, Moscow, 125009 (Russian Federation); Zybtsev, S G [Institute of Radio Engineering and Electronics, Moscow, 125009 (Russian Federation)

    2006-06-01

    Bi-epitaxial YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) thin films with out-of-plane tilt angle in the range 18 - 27{sup 0} were manufactured using pulsed laser deposition on NdGaO{sub 3} tilted-axes substrates with CeO{sub 2} seeding layers. The YBCO thin film orientation over the seeding layer depended on deposition conditions. Removal of the seeding layer from part of the substrate surface by ionbeam etching resulted in formation of a bi-epitaxial thin film with different c-axis orientation of two parts of the film. The bi-epitaxial film orientation and structure were studied using X-ray diffraction techniques, and surface morphology was observed with atomic force microscope (AFM). Photolithography and ion-beam etching techniques were used for patterning bi-epitaxial thin films. Electrical characterization of the obtained structures was performed.

  4. Anisotropic strain relaxation in (Ba0.6Sr0.4)TiO3 epitaxial thin films

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.

    2005-05-01

    We have studied the evolution of anisotropic epitaxial strains in ⟨110⟩-oriented (Ba0.60Sr0.40)TiO3 paraelectric (m3m) thin films grown on orthorhombic (mm2) ⟨100⟩-oriented NdGaO3 by high-resolution x-ray diffractometry. All the six independent components of the three-dimensional strain tensor were measured in films with 25-1200-nm thickness, from which the principal stresses and strains were obtained. Pole figure analysis indicated that the epitaxial relations are [001]m3m‖[001]mm2 and [1¯10]m3m‖[010]mm2 in the plane of the film, and [110]m3m‖[100]mm2 along the growth direction. The dislocation system responsible for strain relief along [001] has been determined to be ∣b ∣(001)=3/4∣b∣. Strain relief along the [1¯10] direction, on the other hand, has been determined to be due to a coupled mechanism given by ∣b∣(1¯10)=∣b∣ and ∣b∣(1¯10)=√3 /4∣b∣. Critical thicknesses, as determined from nonlinear regression using the Matthews-Blakeslee equation, for misfit dislocation formation along [001] and [1¯10] direction were found to be 5 and 7 nm, respectively. The residual strain energy density was calculated as ˜2.9×106J/m3 at 25 nm, which was found to relax an order of magnitude by 200 nm. At 200 nm, the linear dislocation density along [001] and [1¯10] are ˜6.5×105 and ˜6×105cm-1, respectively. For films thicker than 600 nm, additional strain relief occurred through surface undulations, indicating that this secondary strain-relief mechanism is a volume effect that sets in upon cooling from the growth temperature.

  5. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    Science.gov (United States)

    Siegal, Michelle F.; Martínez-Miranda, L. J.; Santiago-Avilés, J. J.; Graham, W. R.; Siegal, M. P.

    1994-02-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 Å. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 Å. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films.

  6. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    International Nuclear Information System (INIS)

    Siegal, M.F.; Martinez-Miranda, L.J.; Santiago-Aviles, J.J.; Graham, W.R.; Siegal, M.P.

    1994-01-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 A. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 A. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films

  7. Hydrogen reduction in GaAsN thin films by flow rate modulated chemical beam epitaxy

    International Nuclear Information System (INIS)

    Saito, K.; Nishimura, K.; Suzuki, H.; Ohshita, Y.; Yamaguchi, M.

    2008-01-01

    The amount of residual H in the GaAsN film grown by chemical beam epitaxy (CBE) can be decreased by flow rate modulation growth. Many H atoms in the films grown by CBE exist as N-H or N-H 2 structures. Although a higher growth temperature was required for decreasing the H concentration ([H]), it caused a decrease in the N concentration ([N]). A reduction in [H] while keeping [N] constant was necessary. By providing an intermittent supply of Ga source while continuously supplying As and N sources, [H] effectively decreased in comparison with the [H] value in the film grown at the same temperature by conventional CBE without reducing [N

  8. Dynamic Atomic Reconstruction: How Fe_{3}O_{4} Thin Films Evade Polar Catastrophe for Epitaxy

    Directory of Open Access Journals (Sweden)

    C. F. Chang

    2016-10-01

    Full Text Available Polar catastrophe at the interface of oxide materials with strongly correlated electrons has triggered a flurry of new research activities. The expectations are that the design of such advanced interfaces will become a powerful route to engineer devices with novel functionalities. Here, we investigate the initial stages of growth and the electronic structure of the spintronic Fe_{3}O_{4}/MgO(001 interface. Using soft x-ray absorption spectroscopy, we have discovered that the so-called A-sites are completely missing in the first Fe_{3}O_{4} monolayer. This discovery allows us to develop an unexpected but elegant growth principle in which, during deposition, the Fe atoms are constantly on the move to solve the divergent electrostatic potential problem, thereby ensuring epitaxy and stoichiometry at the same time. This growth principle provides a new perspective for the design of interfaces.

  9. Tailoring the physical properties of manganite thin films by tuning the epitaxial strain

    International Nuclear Information System (INIS)

    Zhang, P.X.; Zhang, H.; Cha, L.M.; Habermeier, H.-U.

    2003-01-01

    Through a proper choice of the mismatch between substrate and films, the physical properties of manganite thin films can be tailored We show that two types of manganite thin films of the Ruddlesden-Popper family, n=∞ and n=2, demonstrate a dramatic variation of their physical properties. It is proved that the property variation can be tuned precisely by controlling the lattice mismatch and/or the film thickness

  10. Vacancy defects in epitaxial La0.7Sr0.3MnO3 thin films probed by a slow positron beam

    International Nuclear Information System (INIS)

    Jin, S W; Zhou, X Y; Wu, W B; Zhu, C F; Weng, H M; Wang, H Y; Zhang, X F; Ye, B J; Han, R D

    2004-01-01

    Vacancy defects in epitaxial La 0.7 Sr 0.3 MnO 3 (LSMO) thin films on LaAlO 3 substrates were detected using a variable energy positron beam. The line-shape S parameter of the epitaxial thin films deposited at different oxygen pressures was measured as a function of the implanting positron energy E. Our results show that the S parameter of the films changes non-monotonically with their deposition oxygen pressures. For the films deposited at lower oxygen pressures, the increase in S value in the films is attributed to the increase in oxygen vacancies and/or related defect-V O complexes, and for those deposited at higher oxygen pressures, the larger S parameter of the films is caused by the grain boundaries and/or metallic ion vacancies. The surface morphology of the films was also characterized to analyse the open volume defects in the LSMO films

  11. Formation of defect-fluorite structured NdNiOxHy epitaxial thin films via a soft chemical route from NdNiO3 precursors.

    Science.gov (United States)

    Onozuka, T; Chikamatsu, A; Katayama, T; Fukumura, T; Hasegawa, T

    2016-07-26

    A new phase of oxyhydride NdNiOxHy with a defect-fluorite structure was obtained by a soft chemical reaction of NdNiO3 epitaxial thin films on a substrate of SrTiO3 (100) with CaH2. The epitaxial relationship of this phase relative to SrTiO3 could be controlled by changing the reaction temperature. At 240 °C, NdNiOxHy grew with a [001] orientation, forming a thin layer of infinite-layer NdNiO2 at the interface between the NdNiOxHy and the substrate. Meanwhile, a high-temperature reaction at 400 °C formed [110]-oriented NdNiOxHy without NdNiO2.

  12. Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T

    Directory of Open Access Journals (Sweden)

    Wei Niu

    2017-05-01

    Full Text Available We report on the temperature and field dependence of resistance of La0.7Sr0.3MnO3 thin films over a wide temperature range and in pulsed magnetic fields up to 60 T. The epitaxial La0.7Sr0.3MnO3 thin films were deposited by laser molecular beam epitaxy. High magnetic field magnetoresistance curves were fitted by the Brillouin function, which indicated the existence of magnetically polarized regions and the underlying hopping mechanism. The unsaturated magnetoconductance was the most striking finding observed in pulsed magnetic fields up to 60 T. These observations can deepen the fundamental understanding of the colossal magnetoresistance in manganites with strong correlation of transport properties and magnetic ordering.

  13. Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films

    Science.gov (United States)

    Nguyen, Minh D.; Dekkers, Matthijn; Houwman, Evert; Steenwelle, Ruud; Wan, Xin; Roelofs, Andreas; Schmitz-Kempen, Thorsten; Rijnders, Guus

    2011-12-01

    A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.

  14. Angle-resolved photoemission spectroscopy of strontium lanthanum copper oxide thin films grown by molecular-beam epitaxy

    Science.gov (United States)

    Harter, John Wallace

    Among the multitude of known cuprate material families and associated structures, the archetype is "infinite-layer" ACuO2, where perfectly square and flat CuO2 planes are separated by layers of alkaline earth atoms. The infinite-layer structure is free of magnetic rare earth ions, oxygen chains, orthorhombic distortions, incommensurate superstructures, ordered vacancies, and other complications that abound among the other material families. Furthermore, it is the only cuprate that can be made superconducting by both electron and hole doping, making it a potential platform for decoding the complex many-body interactions responsible for high-temperature superconductivity. Research on the infinite-layer compound has been severely hindered by the inability to synthesize bulk single crystals, but recent progress has led to high-quality superconducting thin film samples. Here we report in situ angle-resolved photoemission spectroscopy measurements of epitaxially-stabilized Sr1-chiLa chiCuO2 thin films grown by molecular-beam epitaxy. At low doping, the material exhibits a dispersive lower Hubbard band typical of other cuprate parent compounds. As carriers are added to the system, a continuous evolution from Mott insulator to superconducting metal is observed as a coherent low-energy band develops on top of a concomitant remnant lower Hubbard band, gradually filling in the Mott gap. For chi = 0.10, our results reveal a strong coupling between electrons and (pi,pi) anti-ferromagnetism, inducing a Fermi surface reconstruction that pushes the nodal states below the Fermi level and realizing nodeless superconductivity. Electron diffraction measurements indicate the presence of a surface reconstruction that is consistent with the polar nature of Sr1-chiLachiCuO2. Most knowledge about the electron-doped side of the cuprate phase diagram has been deduced by generalizing from a single material family, Re2-chi CechiCuO4, where robust antiferromagnetism has been observed past chi

  15. Ultrahigh vacuum dc magnetron sputter-deposition of epitaxial Pd(111)/Al2O3(0001) thin films.

    Science.gov (United States)

    Aleman, Angel; Li, Chao; Zaid, Hicham; Kindlund, Hanna; Fankhauser, Joshua; Prikhodko, Sergey V; Goorsky, Mark S; Kodambaka, Suneel

    2018-05-01

    Pd(111) thin films, ∼245 nm thick, are deposited on Al 2 O 3 (0001) substrates at ≈0.5 T m , where T m is the Pd melting point, by ultrahigh vacuum dc magnetron sputtering of Pd target in pure Ar discharges. Auger electron spectra and low-energy electron diffraction patterns acquired in situ from the as-deposited samples reveal that the surfaces are compositionally pure 111-oriented Pd. Double-axis x-ray diffraction (XRD) ω-2θ scans show only the set of Pd 111 peaks from the film. In triple-axis high-resolution XRD, the full width at half maximum intensity Γ ω of the Pd 111 ω-rocking curve is 630 arc sec. XRD 111 pole figure obtained from the sample revealed six peaks 60°-apart at a tilt angles corresponding to Pd 111 reflections. XRD ϕ scans show six 60°-rotated 111 peaks of Pd at the same ϕ angles for 11[Formula: see text]3 of Al 2 O 3 based on which the epitaxial crystallographic relationships between the film and the substrate are determined as [Formula: see text]ǁ[Formula: see text] with two in-plane orientations of [Formula: see text]ǁ[Formula: see text] and [Formula: see text]ǁ[Formula: see text]. Using triple axis symmetric and asymmetric reciprocal space maps, interplanar spacings of out-of-plane (111) and in-plane (11[Formula: see text]) are found to be 0.2242 ± 0.0003 and 0.1591 ± 0.0003 nm, respectively. These values are 0.18% lower than 0.2246 nm for (111) and the same, within the measurement uncertainties, as 0.1588 nm for (11[Formula: see text]) calculated from the bulk Pd lattice parameter, suggesting a small out-of-plane compressive strain and an in-plane tensile strain related to the thermal strain upon cooling the sample from the deposition temperature to room temperature. High-resolution cross-sectional transmission electron microscopy coupled with energy dispersive x-ray spectra obtained from the Pd(111)/Al 2 O 3 (0001) samples indicate that the Pd-Al 2 O 3 interfaces are essentially atomically abrupt and

  16. Near-surface effects of transient oxidation and reduction on Nb-doped SrTiO3 epitaxial thin films

    Science.gov (United States)

    Chang, C. F.; Chen, Q. Y.; Wadekar, P. V.; Lozano, O.; Wong, M. S.; Hsieh, W. C.; Lin, W. Y.; Ko, H. H.; Lin, Q. J.; Huang, H. C.; Ho, N. J.; Tu, L. W.; Liao, H. H.; Chinta, P. V.; Chu, W. K.; Seo, H. W.

    2014-03-01

    We studied the effects of transient oxidation and reduction of Nb-doped epitaxial thin films through variations of PAr and PO2. The samples were prepared by co-sputtering of Nb and SrTiO3 on LaAlO3 substrates. The Nb-content were varied from 0-33.7%, as determined by PIXE. Contact resistance, sheet resistance, and optical properties are used to discriminate the effects.

  17. Low-temperature liquid-phase epitaxy and optical waveguiding of rare-earth-ion-doped KY(WO4)2 thin layers

    NARCIS (Netherlands)

    Romanyuk, Y.E.; Utke, I.; Ehrentraut, D.; Apostolopoulos, V.; Pollnau, Markus; Garcia-Revilla, S.; Valiente, B.

    2004-01-01

    Crystalline $KY(WO_{4})_{2}$ thin layers doped with different rare-earth ions were grown on b-oriented, undoped $KY(WO_{4})_{2}$ substrates by liquid-phase epitaxy employing a low-temperature flux. The ternary chloride mixture of NaCl, KCl, and CsCl with a melting point of 480°C was used as a

  18. On the Novel Biaxial Strain Relaxation Mechanism in Epitaxial Composition Graded La1−xSrxMnO3 Thin Film Synthesized by RF Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Yishu Wang

    2015-11-01

    Full Text Available We report on a novel method to fabricate composition gradient, epitaxial La1−xSrxMnO3 thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1−xSrxMnO3, and pure LaMnO3 and La0.67Sr0.33MnO3 thin films were deposited by radio frequency (RF magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ–2θ X-ray diffraction (XRD and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La1−xSrxMnO3 film ranging from LaMnO3 rich to La0.67Sr0.33MnO3 at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La1−xSrxMnO3 thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties.

  19. Epitaxial growth and magnetic properties of ultraviolet transparent Ga2O3/(Ga1−xFex)2O3 multilayer thin films

    Science.gov (United States)

    Guo, Daoyou; An, Yuehua; Cui, Wei; Zhi, Yusong; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Li, Peigang; Wu, Zhenping; Tang, Weihua

    2016-01-01

    Multilayer thin films based on the ferromagnetic and ultraviolet transparent semiconductors may be interesting because their magnetic/electronic/photonic properties can be manipulated by the high energy photons. Herein, the Ga2O3/(Ga1−xFex)2O3 multilayer epitaxial thin films were obtained by alternating depositing of wide band gap Ga2O3 layer and Fe ultrathin layer due to inter diffusion between two layers at high temperature using the laser molecular beam epitaxy technique. The multilayer films exhibits a preferred growth orientation of crystal plane, and the crystal lattice expands as Fe replaces Ga site. Fe ions with a mixed valence of Fe2+ and Fe3+ are stratified distributed in the film and exhibit obvious agglomerated areas. The multilayer films only show a sharp absorption edge at about 250 nm, indicating a high transparency for ultraviolet light. What’s more, the Ga2O3/(Ga1−xFex)2O3 multilayer epitaxial thin films also exhibits room temperature ferromagnetism deriving from the Fe doping Ga2O3. PMID:27121446

  20. Epitaxial growth and magnetic properties of ultraviolet transparent Ga2O3/(Ga1-xFex)2O3 multilayer thin films.

    Science.gov (United States)

    Guo, Daoyou; An, Yuehua; Cui, Wei; Zhi, Yusong; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Li, Peigang; Wu, Zhenping; Tang, Weihua

    2016-04-28

    Multilayer thin films based on the ferromagnetic and ultraviolet transparent semiconductors may be interesting because their magnetic/electronic/photonic properties can be manipulated by the high energy photons. Herein, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films were obtained by alternating depositing of wide band gap Ga2O3 layer and Fe ultrathin layer due to inter diffusion between two layers at high temperature using the laser molecular beam epitaxy technique. The multilayer films exhibits a preferred growth orientation of crystal plane, and the crystal lattice expands as Fe replaces Ga site. Fe ions with a mixed valence of Fe(2+) and Fe(3+) are stratified distributed in the film and exhibit obvious agglomerated areas. The multilayer films only show a sharp absorption edge at about 250 nm, indicating a high transparency for ultraviolet light. What's more, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films also exhibits room temperature ferromagnetism deriving from the Fe doping Ga2O3.

  1. Epitaxial growth of Sb-doped nonpolar a-plane ZnO thin films on r-plane sapphire substrates by RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hou-Guang, E-mail: houguang@isu.edu.tw [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China); Hung, Sung-Po [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China)

    2014-02-15

    Highlights: ► Sb-doped nonpolar a-plane ZnO layers were epitaxially grown on sapphire substrates. ► Crystallinity and electrical properties were studied upon growth condition and doping concentration. ► The out-of-plane lattice spacing of ZnO films reduces monotonically with increasing Sb doping level. ► The p-type conductivity of ZnO:Sb film is closely correlated with annealing condition and Sb doping level. -- Abstract: In this study, the epitaxial growth of Sb-doped nonpolar a-plane (112{sup ¯}0) ZnO thin films on r-plane (11{sup ¯}02) sapphire substrates was performed by radio-frequency magnetron sputtering. The influence of the sputter deposition conditions and Sb doping concentration on the microstructural and electrical properties of Sb-doped ZnO epitaxial films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Hall-effect measurement. The measurement of the XRD phi-scan indicated that the epitaxial relationship between the ZnO:Sb layer and sapphire substrate was (112{sup ¯}0){sub ZnO}//(11{sup ¯}02){sub Al{sub 2O{sub 3}}} and [11{sup ¯}00]{sub ZnO}//[112{sup ¯}0]{sub Al{sub 2O{sub 3}}}. The out-of-plane a-axis lattice parameter of ZnO films was reduced monotonically with the increasing Sb doping level. The cross-sectional transmission electron microscopy (XTEM) observation confirmed the absence of any significant antimony oxide phase segregation across the thickness of the Sb-doped ZnO epitaxial film. However, the epitaxial quality of the films deteriorated as the level of Sb dopant increased. The electrical properties of ZnO:Sb film are closely correlated with post-annealing conditions and Sb doping concentrations.

  2. Low-temperature technique of thin silicon ion implanted epitaxial detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kordyasz, A.J.; Bednarek, A. [Warsaw University, Heavy Ion Laboratory, Warsaw (Poland); Le Neindre, N.; Bougault, R.; Lopez, O.; Merrer, Y.; Vient, E. [Universite de Caen, LPC, IN2P3-CNRS, ENSICAEN, Caen-Cedex (France); Parlog, M. [Universite de Caen, LPC, IN2P3-CNRS, ENSICAEN, Caen-Cedex (France); ' ' Horia Hulubei' ' National Institute of Physics and Nuclear Engineering (IFIN-HH), Bucharest Magurele (Romania); Casini, G.; Poggi, G.; Bini, M.; Valdre, S.; Scarlini, E.; Pasquali, G.; Pastore, G.; Piantelli, S.; Stefanini, A.; Olmi, A.; Barlini, S. [INFN Firenze, Sesto Fiorentino (Italy); Universita di Firenze, Sesto Fiorentino (Firenze) (Italy); Kowalczyk, M. [Warsaw University, Heavy Ion Laboratory, Warsaw (Poland); University of Warsaw, Institute of Experimental Physics, Warsaw (Poland); Frankland, J.D.; Bonnet, E.; Chbihi, A.; Gruyer, D. [CEA et IN2P3-CNRS, GANIL, Caen-Cedex 05 (France); Borderie, B.; Ademard, G.; Edelbruck, P.; Rivet, M.F.; Salomon, F. [IN2P3-CNRS, Institut de Physique Nucleaire, Orsay-Cedex (France); Boiano, A.; Rosato, E.; Meoli, A.; Ordine, A.; Spadaccini, G.; Tortone, G.; Vigilante, M.; Vanzanella, E. [Universita di Napoli ' ' Federico II' ' , Dipartimento di Scienze Fisiche, Napoli (Italy); INFN, Napoli (Italy); Bruno, M.; Serra, S.; Morelli, L.; Guerzoni, M. [INFN, Bologna (Italy); Universita di Bologna, Bologna (Italy); Alba, R.; Santonocito, D.; Maiolino, C. [INFN, Catania (Italy); Universita di Catania, LNS, Catania (Italy); Cinausero, M.; Gramegna, F.; Marchi, T. [INFN LNL Legnaro, Legnaro (Padova) (Italy); Kozik, T.; Kulig, P.; Twarog, T.; Sosin, Z. [Jagiellonian University, Cracow (Poland); Gasior, K.; Grzeszczuk, A.; Zipper, W. [University of Silesia, Silesian University, Katowice (Poland); Sarnecki, J.; Lipinski, D.; Wodzinska, H.; Brzozowski, A.; Teodorczyk, M.; Gajewski, M.; Zagojski, A.; Krzyzak, K. [Institute of Electronic Materials Technology, Warsaw (Poland); Tarasiuk, K.J. [University of Warsaw, Institute of Experimental Physics, Warsaw (Poland); Khabanowa, Z. [Faculty of Physics, Warsaw University of Technology, Warsaw (Poland); Kordyasz, L. [Warsaw University of Technology, Faculty of Mechatronics, Institute of Mikromechanics and Photonics, Department of Design of Precision Devices, Warsaw (Poland)

    2015-02-01

    A new technique of large-area thin ion implanted silicon detectors has been developed within the R and D performed by the FAZIA Collaboration. The essence of the technique is the application of a low-temperature baking process instead of high-temperature annealing. This thermal treatment is performed after B{sup +} ion implantation and Al evaporation of detector contacts, made by using a single adjusted Al mask. Extremely thin silicon pads can be therefore obtained. The thickness distribution along the X and Y directions was measured for a prototype chip by the energy loss of α-particles from {sup 241}Am (left angle E{sub α} right angle = 5.5 MeV). Preliminary tests on the first thin detector (area ∼ 20 x 20 mm{sup 2}) were performed at the INFN-LNS cyclotron in Catania (Italy) using products emitted in the heavy-ion reaction {sup 84}Kr (E = 35 A MeV) + {sup 112}Sn. The ΔE - E ion identification plot was obtained using a telescope consisting of our thin ΔE detector (21 μm thick) followed by a typical FAZIA 510 μm E detector of the same active area. The charge distribution of measured ions is presented together with a quantitative evaluation of the quality of the Z resolution. The threshold is lower than 2 A MeV depending on the ion charge. (orig.)

  3. Planar Hall effect and magnetic anisotropy in epitaxially strained chromium dioxide thin films

    NARCIS (Netherlands)

    Goennenwein, S.T.B.; Keizer, R.S.; Schink, S.W.; Van Dijk, I.; Klapwijk, T.M.; Miao, G.X.; Xiao, G.; Gupta, A.

    2007-01-01

    We have measured the in-plane anisotropic magnetoresistance of 100?nm thick CrO2 thin films at liquid He temperatures. In low magnetic fields H, both the longitudinal and the transverse (planar Hall) resistance show abrupt switches, which characteristically depend on the orientation of H. All the

  4. Magnetic properties of epitaxial MnAs thin films on GaAs (001)

    CERN Document Server

    Park, Y S

    2000-01-01

    The magnetic properties of two types of epitaxial MnAs films on GaAs (001) substrates in the thickness range of 20 approx 200 nm were studied. Using longitudinal a magneto-optical Kerr-effect(MOKE) apparatus at lambda=632.8 nm, we determined the Curie temperatures of the 100-nm thick films to be 54.0+-0.5 .deg. C and 63.7+-0.5 .deg. C for type A films and type B films, respectively. The observed Curie temperatures corresponded to increases of 36.8 .deg. C and 33.9 .deg. C per one percent increase in the unit cell volume for type A and B, respectively. The normalized maximum MOKE signal from the type A film exhibited a first-order-like magnetic transition while that of type B underwent a second-order-like transition. These different behaviors between types A and B stem from different residual stresses being exerted on the hexagonal phase. Utilizing a Foner-type vibrating sample magnetometer at room temperature, we examined the thickness dependence of the coercive force and the saturation magnetization of the f...

  5. STM studies of GeSi thin layers epitaxially grown on Si(111)

    Science.gov (United States)

    Motta, N.; Sgarlata, A.; De Crescenzi, M.; Derrien, J.

    1996-08-01

    Ge/Si alloys were prepared in UHV by solid phase epitaxy on Si(111) substrates. The alloy formation, as a function of the evaporation rate and the Ge layer thickness has been followed in situ by RHEED and scanning tunneling microscopy. The 5 × 5 surface reconstruction appeared after annealing at 450°C Ge layers (up to 10 Å thick), obtained from a low rate Knudsen cell evaporator. In this case a nearly flat and uniform layer of reconstructed alloy was observed. When using an e-gun high rate evaporator we needed to anneal the Ge layer up to 780°C to obtain a 5 × 5 reconstruction. The grown layer was not flat, with many steps and Ge clusters; at high coverages (10 Å and more) large Ge islands appeared. Moreover, we then succeeded in visualizing at atomic resolution the top of some of these Ge islands which displayed a 2 × 1 reconstruction, probably induced from the high compressive strain due to the lattice mismatch with the substrate. We suggest that this unusual behavior could be connected to the high evaporation rate, which helped the direct formation of Ge microcrystals on the Si substrate during the deposition process.

  6. Thin film epitaxy and structure property correlations for non-polar ZnO films

    International Nuclear Information System (INIS)

    Pant, P.; Budai, J.D.; Aggarwal, R.; Narayan, Roger J.; Narayan, J.

    2009-01-01

    Heteroepitaxial growth and strain relaxation were investigated in non-polar a-plane (1 1 -2 0)ZnO films grown on r-plane (1 0 -1 2)sapphire substrates in the temperature range 200-700 deg. C by pulsed laser deposition. The lattice misfit in the plane of the film for this orientation varied from -1.26% in [0 0 0 1] to -18.52% in the [-1 1 0 0] direction. The alignment of (1 1 -2 0)ZnO planes parallel to (1 0 -1 2)sapphire planes was confirmed by X-ray diffraction θ-2θ scans over the entire temperature range. X-ray φ-scans revealed the epitaxial relationship:[0 0 0 1]ZnO-parallel [-1 1 0 1]sap; [-1 1 0 0]ZnO-parallel [-1 -1 2 0]sap. Depending on the growth temperature, variations in the structural, optical and electrical properties were observed in the grown films. Room temperature photoluminescence for films grown at 700 deg. C shows a strong band-edge emission. The ratio of the band-edge emission to green band emission is 135:1, indicating reduced defects and excellent optical quality of the films. The resistivity data for the films grown at 700 deg. C shows semiconducting behavior with room temperature resistivity of 2.2 x 10 -3 Ω-cm.

  7. Photoluminescence study of epitaxially grown ZnSnAs2:Mn thin films

    International Nuclear Information System (INIS)

    Mammadov, E; Haneta, M; Toyota, H; Uchitomi, N

    2011-01-01

    The photoluminescence (PL) properties of heavily Mn-doped ZnSnAs 2 layers epitaxially grown on nearly lattice-matched semi-insulating InP substrates are studied. PL spectra are obtained for samples with Mn concentrations of 5, 12 and 24 mol% relative to the combined concentrations of Zn and Sn. A broad emission band centered at ∼ 1 eV is detected for Mn-doped layers at room temperature. The emission is a intense broad asymmetric line at low temperatures. The line is reconstructed by superposition of two bands with peak energies of ∼ 0.99 and 1.07 eV, similar to those reported for InP. These bands are superimposed onto a 1.14 eV band with well-resolved phonon structure for the layer doped with 12 % Mn. Recombination mechanism involving the split-off band of the ZnSnAs 2 is suggested. Temperature dependence of integrated intensities of the PL bands indicates to thermally activated emission with activation energies somewhat different from those found for InP. Mn substitution at cationic sites increases the concentration of holes which may act as recombination centers. Recombination to the holes bound to Mn ions with the ground state located below the top of the valence band has been proposed as a possible PL mechanism.

  8. Direct observation of fatigue in epitaxially grown Pb(Zr,Ti)O3 thin films using second harmonic piezoresponse force microscopy

    Science.gov (United States)

    Murari, Nishit M.; Hong, Seungbum; Lee, Ho Nyung; Katiyar, Ram. S.

    2011-08-01

    Here, we present a direct observation of fatigue phenomena in epitaxially grown Pb(Zr0.2Ti0.8)O3 (PZT) thin films using second harmonic piezoresponse force microscopy (SH-PFM). We observed strong correlation between the SH-PFM amplitude and phase signals with the remnant piezoresponse at different switching cycles. The SH-PFM results indicate that the average fraction of switchable domains decreases globally and the phase delays of polarization switching differ locally. In addition, we found that the fatigue developed uniformly over the whole area without developing region-by-region suppression of switchable polarization as in polycrystalline PZT thin films.

  9. Direct Demonstration of the Emergent Magnetism Resulting from the Multivalence Mn in a LaMnO3 Epitaxial Thin Film System

    DEFF Research Database (Denmark)

    Niu, Wei; Liu, Wenqing; Gu, Min

    2018-01-01

    that play a decisive role in the emergence of ferromagnetism in the otherwise antiferromagnetic LaMnO3 thin films are found. Combining spatially resolved electron energy‐loss spectroscopy, X‐ray absorption spectroscopy, and X‐ray magnetic circular dichroism techniques, it is determined unambiguously...... provide a hitherto‐unexplored multivalence state of Mn on the emergent magnetism in undoped manganite epitaxial thin films, such as LaMnO3 and BiMnO3, and shed new light on all‐oxide spintronic devices....

  10. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin; Bowden, Mark E.; Varga, Tamas; Shutthanandan, Vaithiyalingam; Spurgeon, Steven R.; Yan, Pengfei; Wang, Chongmin; Ramuhalli, Pradeep; Henager, Charles H.

    2017-05-01

    Pyrochlore-structure oxides, A2B2O7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. The mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La2Zr2O7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr+ at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopy (STEM). At lower doses, the surface of the La2Zr2O7 film amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La2Zr2O7, the bandgap of a thick La2Zr2O7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.

  11. Dynamics of ferroelectric nanodomains in BaTiO3 epitaxial thin films via piezoresponse force microscopy

    International Nuclear Information System (INIS)

    Pertsev, N A; Petraru, A; Kohlstedt, H; Waser, R; Bdikin, I K; Kiselev, D; Kholkin, A L

    2008-01-01

    Ferroelectric nanodomains were created in BaTiO 3 thin films by applying a voltage to a sharp conducting tip of a scanning force microscope (SFM). The films were epitaxially grown on SrRuO 3 -covered (001)-oriented SrTiO 3 substrates by a high-pressure sputtering. They appeared to be single-crystalline with the (001) crystallographic orientation relative to the substrate. Using the piezoresponse mode of the SFM to detect the out-of-plane film polarization, the domain sizes were measured as a function of the applied writing voltage and the pulse time. It was found that the time dependence of the domain diameter in a 60 nm thick BaTiO 3 film deviates significantly from the logarithmic law observed earlier in Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) films. At a given writing time, the domain size increases nonlinearly with increasing applied voltage, in contrast to the linear behavior reported earlier for PZT films and LiNbO 3 single crystals. The dynamics of domain growth is analyzed theoretically taking into account the strong inhomogeneity of the external electric field in the film and the influence of the bottom electrode. It is shown that the observed writing time and voltage dependences of the domain size can be explained by the domain-wall creep in the presence of random-bond disorder

  12. Frequency response improvement of a two-port surface acoustic wave device based on epitaxial AlN thin film

    Science.gov (United States)

    Gao, Junning; Hao, Zhibiao; Luo, Yi; Li, Guoqiang

    2018-01-01

    This paper presents an exploration on improving the frequency response of the symmetrical two-port AlN surface acoustic wave (SAW) device, using epitaxial AlN thin film on (0001) sapphire as the piezoelectric substrate. The devices were fabricated by lift-off processes with Ti/Al composite electrodes as interleaved digital transducers (IDT). The impact of DL and the number of the IDT finger pairs on the frequency response was carefully investigated. The overall properties of the device are found to be greatly improved with DL elongation, indicated by the reduced pass band ripple and increased stop band rejection ratio. The rejection increases by 8.3 dB when DL elongates from 15.5λ to 55.5λ and 4.4 dB further accompanying another 50λ elongation. This is because larger DL repels the stray acoustic energy out of the propagation path and provides a cleaner traveling channel for functional SAW, and at the same time restrains electromagnetic feedthrough. It is also found that proper addition of the IDT finger pairs is beneficial for the device response, indicated by the ripple reduction and the insertion loss drop.

  13. Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yang, H. F.; Liu, Z. T.; Fan, C. C.; Xiang, P.; Zhang, K. L.; Li, M. Y.; Liu, J. S.; Yao, Q.; Shen, D. W.

    2016-01-01

    By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO 3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO 3 and iso-polarity LaAlO 3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO 3 (111) substrate was more suitable than Nb-doped SrTiO 3 . In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO 3 based superlattices.

  14. Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xianzhong; Matthes, Frank; Bürgler, Daniel E., E-mail: d.buergler@fz-juelich.de; Schneider, Claus M. [Peter Grünberg Institut, Electronic Properties (PGI-6) and Jülich-Aachen Research Alliance, Fundamentals of Future Information Technology (JARA-FIT), Forschungszentrum Jülich, D-52425 Jülich (Germany)

    2016-01-15

    The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  15. Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoran; Cao, Yanwei; Pal, B.; Middey, S.; Kareev, M.; Choi, Y.; Shafer, P.; Haskel, D.; Arenholz, E.; Chakhalian, J.

    2017-12-01

    We report on the selective fabrication of high-quality Sr2IrO4 and SrIrO3 epitaxial thin films from a single polycrystalline Sr2IrO4 target by pulsed laser deposition. Using a combination of x-ray diffraction and photoemission spectroscopy characterizations, we discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films, and triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant x-ray absorption spectroscopy measurements taken at the Ir L edge and the O K edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structures of both compounds. These results suggest that in addition to the conventional thermodynamics consideration, higher members of the Srn+1IrnO3n+1 series can possibly be achieved by kinetic control away from the thermodynamic limit. These findings offer an approach to the synthesis of ultrathin films of the RP series of iridates and can be extended to other complex oxides with layered structure.

  16. Structural sensitivity of x-ray Bragg projection ptychography to domain patterns in epitaxial thin films

    International Nuclear Information System (INIS)

    Hruszkewycz, S. O.; Zhang, Q.; Holt, M. V.; Highland, M. J.

    2016-01-01

    Bragg projection ptychography (BPP) is a coherent diffraction imaging technique capable of mapping the spatial distribution of the Bragg structure factor in nanostructured thin films. Here, we show that, because these images are projections, the structural sensitivity of the resulting images depends on the film thickness and the aspect ratio and orientation of the features of interest and that image interpretation depends on these factors. Lastly, we model changes in contrast in the BPP reconstructions of simulated PbTiO_3 ferroelectric thin films with meandering 180° stripe domains as a function of film thickness, discuss their origin, and comment on the implication of these factors on the design of BPP experiments of general nanostructured films.

  17. Theoretical studies of epitaxially grown Co and Ni thin films on (111) metallic substrates

    Czech Academy of Sciences Publication Activity Database

    Zelený, Martin; Šob, Mojmír

    2008-01-01

    Roč. 77, č. 15 (2008), 155435/1-155435/6 ISSN 1098-0121 R&D Projects: GA AV ČR IAA1041302; GA ČR GD106/05/H008; GA MŠk OC 147 Institutional research plan: CEZ:AV0Z20410507 Keywords : Thin metallic films * Ab initio calculations * Electronic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  18. Epitaxial Lift-Off of Centimeter-Scaled Spinel Ferrite Oxide Thin Films for Flexible Electronics.

    Science.gov (United States)

    Shen, Lvkang; Wu, Liang; Sheng, Quan; Ma, Chunrui; Zhang, Yong; Lu, Lu; Ma, Ji; Ma, Jing; Bian, Jihong; Yang, Yaodong; Chen, Aiping; Lu, Xiaoli; Liu, Ming; Wang, Hong; Jia, Chun-Lin

    2017-09-01

    Mechanical flexibility of electronic devices has attracted much attention from research due to the great demand in practical applications and rich commercial value. Integration of functional oxide materials in flexible polymer materials has proven an effective way to achieve flexibility of functional electronic devices. However, the chemical and mechanical incompatibilities at the interfaces of dissimilar materials make it still a big challenge to synthesize high-quality single-crystalline oxide thin film directly on flexible polymer substrates. This study reports an improved method that is employed to successfully transfer a centimeter-scaled single-crystalline LiFe 5 O 8 thin film on polyimide substrate. Structural characterizations show that the transferred films have essentially no difference in comparison with the as-grown films with respect to the microstructure. In particular, the transferred LiFe 5 O 8 films exhibit excellent magnetic properties under various mechanical bending statuses and show excellent fatigue properties during the bending cycle tests. These results demonstrate that the improved transfer method provides an effective way to compose single-crystalline functional oxide thin films onto flexible substrates for applications in flexible and wearable electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Structural and electrical properties of c-axis epitaxial and polycrystalline Sr sub 3 Bi sub 4 Ti sub 6 O sub 2 sub 1 thin films

    CERN Document Server

    Zhang, S T; Sun, H P; Pan Xiao Qing; Tan, W S; Liu, Z G; Ming, N B

    2003-01-01

    c-axis epitaxial and polycrystalline Sr sub 3 Bi sub 4 Ti sub 6 O sub 2 sub 1 (SBTi) thin films were fabricated on (001)SrTiO sub 3 (STO) single-crystal substrates and Pt/Ti sub 2 /SiO sub 2 /Si substrates respectively, by pulsed laser deposition (PLD). Structures of the films were systematically characterized by x-ray diffraction (XRD), including theta-2 theta-scans, rocking curve scans and phi-scans, atomic force microscopy and transmission electron microscopy (TEM). The epitaxial orientation relation of the SBTi films on STO is established by selected-area electron diffraction and XRD phi-scans to be (001)SBTi || (001)STO, [11-bar 0]SBTi || [010]STO. Cross-sectional high-resolution TEM studies on the epitaxial SBTi film revealed that SBTi is a single-phase material. A special kind of irrational atomic shift along the [001] direction was observed and is discussed in detail. By using an evanescent microwave probe (EMP), the room-temperature dielectric constant of the epitaxial SBTi film was measured to be 21...

  20. Epitaxial Oxide Thin Films Grown by Solid Source Metal-Organic Chemical Vapor Deposition.

    Science.gov (United States)

    Lu, Zihong

    1995-01-01

    The conventional liquid source metal-organic chemical vapor deposition (MOCVD) technique is capable of producing large area, high quality, single crystal semiconductor films. However, the growth of complex oxide films by this method has been hampered by a lack of suitable source materials. While chemists have been actively searching for new source materials, the research work reported here has demonstrated the successful application of solid metal-organic sources (based on tetramethylheptanedionate) to the growth of high quality thin films of binary compound cerium dioxide (CeO_2), and two more complex materials, the ternary compound lithium niobate (LiNbO_3), with two cations, and the quaternary compound strontium barium niobate (SBN), with three cations. The growth of CeO_2 thin films on (1012)Al_2O_3 substrates has been used as a model to study the general growth behavior of oxides. Factors affecting deposition rate, surface morphology, out-of-plane mosaic structure, and film orientation have been carefully investigated. A kinetic model based on gas phase prereaction is proposed to account for the substrate temperature dependence of film orientation found in this system. Atomically smooth, single crystal quality cerium dioxide thin films have been obtained. Superconducting YBCO films sputtered on top of solid source MOCVD grown thin cerium dioxide buffer layers on sapphire have been shown to have physical properties as good as those of YBCO films grown on single crystal MgO substrates. The thin film growth of LiNbO_3 and Sr_{1-x}Ba _{x}Nb_2 O_6 (SBN) was more complex and challenging. Phase purity, transparency, in-plane orientation, and the ferroelectric polarity of LiNbO _3 films grown on sapphire substrates was investigated. The first optical quality, MOCVD grown LiNbO _3 films, having waveguiding losses of less than 2 dB/cm, were prepared. An important aspect of the SBN film growth studies involved finding a suitable single crystal substrate material. Mg

  1. Dielectric and ferroelectric properties of strain-relieved epitaxial lead-free KNN-LT-LS ferroelectric thin films on SrTiO3 substrates

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-05-01

    We report the growth of single-phase (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated ⟨001⟩ oriented SrTiO3 substrates by using pulsed laser deposition. Films grown at 600°C under low laser fluence exhibit a ⟨001⟩ textured columnar grained nanostructure, which coalesce with increasing deposition temperature, leading to a uniform fully epitaxial highly stoichiometric film at 750°C. However, films deposited at lower temperatures exhibit compositional fluctuations as verified by Rutherford backscattering spectroscopy. The epitaxial films of 400-600nm thickness have a room temperature relative permittivity of ˜750 and a loss tangent of ˜6% at 1kHz. The room temperature remnant polarization of the films is 4μC /cm2, while the saturation polarization is 7.1μC/cm2 at 24kV/cm and the coercive field is ˜7.3kV/cm. The results indicate that approximately 50% of the bulk permittivity and 20% of bulk spontaneous polarization can be retained in submicron epitaxial KNN-LT-LS thin film, respectively. The conductivity of the films remains to be a challenge as evidenced by the high loss tangent, leakage currents, and broad hysteresis loops.

  2. Ambiguous Role of Growth-Induced Defects on the Semiconductor-to-Metal Characteristics in Epitaxial VO2/TiO2 Thin Films.

    Science.gov (United States)

    Mihailescu, Cristian N; Symeou, Elli; Svoukis, Efthymios; Negrea, Raluca F; Ghica, Corneliu; Teodorescu, Valentin; Tanase, Liviu C; Negrila, Catalin; Giapintzakis, John

    2018-04-25

    Controlling the semiconductor-to-metal transition temperature in epitaxial VO 2 thin films remains an unresolved question both at the fundamental as well as the application level. Within the scope of this work, the effects of growth temperature on the structure, chemical composition, interface coherency and electrical characteristics of rutile VO 2 epitaxial thin films grown on TiO 2 substrates are investigated. It is hereby deduced that the transition temperature is lower than the bulk value of 340 K. However, it is found to approach this value as a function of increased growth temperature even though it is accompanied by a contraction along the V 4+ -V 4+ bond direction, the crystallographic c-axis lattice parameter. Additionally, it is demonstrated that films grown at low substrate temperatures exhibit a relaxed state and a strongly reduced transition temperature. It is suggested that, besides thermal and epitaxial strain, growth-induced defects may strongly affect the electronic phase transition. The results of this work reveal the difficulty in extracting the intrinsic material response to strain, when the exact contribution of all strain sources cannot be effectively determined. The findings also bear implications on the limitations in obtaining the recently predicted novel semi-Dirac point phase in VO 2 /TiO 2 multilayer structures.

  3. Buffer-layer enhanced crystal growth of BaB6 (1 0 0) thin films on MgO (1 0 0) substrates by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Kato, Yushi; Yamauchi, Ryosuke; Arai, Hideki; Tan, Geng; Tsuchimine, Nobuo; Kobayashi, Susumu; Saeki, Kazuhiko; Takezawa, Nobutaka; Mitsuhashi, Masahiko; Kaneko, Satoru; Yoshimoto, Mamoru

    2012-01-01

    Crystalline BaB 6 (1 0 0) thin films can be fabricated on MgO (1 0 0) substrates by inserting a 2-3 nm-thick epitaxial SrB 6 (1 0 0) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB 6 (1 0 0)/SrB 6 (1 0 0)/MgO (1 0 0) with the single domain of the epitaxial relationship. Conversely, BaB 6 thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB 6 thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB 6 epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90 × 10 -1 Ω cm at room temperature.

  4. Epitaxial growth of YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films on LiNbO sub 3 substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.G.; Koren, G.; Gupta, A.; Segmuller, A.; Chi, C.C. (IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (US))

    1989-09-18

    {ital In} {ital situ} epitaxial growth of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films on {ital Y}-cut LiNbO{sub 3} substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp ({lt}1 K) superconducting transition with {ital T}{sub {ital c}}({ital R}=0) of 92 K. High critical current density of {ital J}{sub {ital c}}(77 K)=2{times}10{sup 5} A/cm{sup 2} is observed, which is in accordance with epitaxial growth. Film orientation observed from x-ray diffraction spectra indicates that the {ital c} axis is normal to the substrate plane and the {ital a} axis is at 45{degree} to the (11.0) direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane.

  5. Growth of Pb(Ti,Zr)O 3 thin films by metal-organic molecular beam epitaxy

    Science.gov (United States)

    Avrutin, V.; Liu, H. Y.; Izyumskaya, N.; Xiao, B.; Özgür, Ü.; Morkoç, H.

    2009-02-01

    Single-crystal Pb(Zr xTi 1-x)O 3 thin films have been grown on (0 0 1) SrTiO 3 and SrTiO 3:Nb substrates by molecular beam epitaxy using metal-organic source of Zr and two different sources of reactive oxygen—RF plasma and hydrogen-peroxide sources. The same growth modes and comparable structural properties were observed for the films grown with both oxygen sources, while the plasma source allowed higher growth rates. The films with x up to 0.4 were single phase, while attempts to increase x beyond gave rise to the ZrO 2 second phase. The effects of growth conditions on growth modes, Zr incorporation, and phase composition of the Pb(Zr xTi 1-x)O 3 films are discussed. Electrical and ferroelectric properties of the Pb(Zr xTi 1-x)O 3 films of ~100 nm in thickness grown on SrTiO 3:Nb were studied using current-voltage, capacitance-voltage, and polarization-field measurements. The single-phase films show low leakage currents and large breakdown fields, while the values of remanent polarization are low (around 5 μC/cm 2). It was found that, at high sweep fields, the contribution of the leakage current to the apparent values of remanent polarization can be large, even for the films with large electrical resistivity (˜10 8-10 9 Ω cm at an electric filed of 1 MV/cm). The measured dielectric constant ranges from 410 to 260 for Pb(Zr 0.33Ti 0.67)O 3 and from 313 to 213 for Pb(Zr 0.2Ti 0.8)O 3 in the frequency range from 100 to 1 MHz.

  6. Aspects of 'low field' magnetotransport in epitaxial thin films of the ferromagnetic metallic oxide SrRuO3

    International Nuclear Information System (INIS)

    Moran, O.; Saldarriaga, W.; Baca, E.

    2007-01-01

    Epitaxial thin films of the conductive ferromagnetic oxide SrRuO 3 were grown on an (001) SrTiO 3 (STO) substrate by using DC sputtering technique. The magnetic and magnetoresistive properties of the films were measured by applying the magnetic field both perpendicular (out-of-plane) and parallel (in-plane) to the film plane and ever maintaining the direction of the applied field perpendicular to that of the transport current. The films grown on an (001) STO substrate showed identical magnetization properties in two orthogonal crystallographic directions of the substrate, [100] S and [001] S (in-plane and out-of-plane geometry), which suggests the presence of a multi domain structure within the plane of the film. For such samples, no anisotropic field (hard axis) along de [001]s direction, i.e., perpendicular to the film-plane could be detected. Nevertheless, a distinguishable temperature dependent out-of-plane anisotropic magnetoresistance (MR) along with strong temperature dependent low field hysteretic MR(H) behavior was detected for the studied films. A negative MR ratio MR(T)=[ρ(μ 0 H=9T; T)-ρ( μ 0 H=0T; T)]/ρ( μ 0 H=0T; T) on the order of a few percent, with maximums of ∼6% and ∼4% (right at the Curie temperature, T C ∼160K) was calculated for an in-plane and out-of plane measuring geometry, respectively. In addition there is an equally strong MR effect at low temperatures, which might be related to the temperature dependence of the magnetocrystalline anisotropy together with a magnetization rotation. Both the MR(T) behavior and the achieved values (except for T 3 films grown on 2 o miscut (001) STO substrates with the current parallel to the field and parallel to the [1-bar11] direction, which was identified as the easier axis for magnetization

  7. Superconducting spin valves based on epitaxial Fe/V-hybrid thin film heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Gregor

    2010-12-10

    This study presents a systematic investigation of the SSV effect in FM/SC/FM and FM/N/FM/SC heterostructures. Before investigating the actual SSV effect, we first pre-analyzed structural, magnetic and superconducting properties of the Fe/V system. In these preliminary studies we demonstrated, that epitaxial Fe/V heterostructures of superior crystalline quality can be grown by DC sputter deposition. With a Fe/V interface thickness of only one monolayer, the chemical separation of the Fe and V layers is extremely sharp. Moreover, the magnetic investigation showed that from thicknesses of two Fe(001) monolayers on the Fe layers in the superlattice possess a magnetic moment. Furthermore, we demonstrated the interlayer exchange coupling as oscillatory function of the V interlayer thickness. The investigations of the superconducting parameters of the Fe/V system revealed a non-monotonic T{sub S} vs. d{sub Fe} dependence in sample series (1). This observation proves the presence of the FM/SC proximity effect. The studies of various heterostructures of the design AFM/FM/SC/FM revealed a strong counteracting influence on the SSV effect, the stray field effect. The sample containing Fe{sub 25}V{sub 75} alloy layers, has the highest ratio of Cooper pair coherence length and superconductor thickness (ξ{sub S})/(d{sub S}), and its superconducting transition temperature is comparable to the sample with Fe{sub 35}V{sub 65} alloy layers. Nevertheless, the SSV effect in sample Fe{sub 25}V{sub 75} with alloy layers is much smaller than in sample with Fe{sub 35}V{sub 65} alloy layers. For a high-performance superconducting spin valve based on a FM1/SC/FM2 heterostructure at least four parameters have to be optimized simultaneously. 1. The magnetic domain size in FM1 and FM2 has to be as large as possible in order to reduce the stray field effect resulting from magnetization components in the FM domain walls perpendicular to the SC layer. 2. When using ferromagnetic alloys as

  8. THERMAL EXPANSION BEHAVIOR OF THE Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF WITH Sm0.2Ce0.8O1.9

    Directory of Open Access Journals (Sweden)

    M. AHMADREZAEI

    2014-03-01

    Full Text Available Nanostructured perovskite oxides of Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF were synthesized through the co-precipitation method. The thermal decomposition, phase formation and thermal expansion behavior of BSCF were characterized by thermogravimetric analysis, X-ray diffraction (XRD, and dilatometry, respectively. XRD peaks were indexed to a cubic perovskite structure with a Pm3m (221 space group. All the combined oxides produced the desired perovskite-phase BSCF. The microstructures were characterized by scanning electron microscopy (SEM and transmission electron microscopy (TEM. The TEM analysis showed that BSCF powders had uniform nanoparticle sizes and high homogeneity. The cross-sectional SEM micrograph of BSCF exhibited a continuous and no delaminated layer from the electrolyte-supported cell. The thermal expansion coefficient (TEC of BSCF was 16.2×10-6 K-1 at a temperature range of 600°C to 800°C. Additional experiments showed that the TEC of BSCF is comparable to that of Sm0.2Ce0.8O1.9 (SDC within the same temperature range. The results demonstrate that BSFC is a promising cathode material for intermediate-temperature solid-oxide fuel cells.

  9. Scintillation efficiency and X-ray imaging with the RE-Doped LuAG thin films grown by liquid phase epitaxy

    International Nuclear Information System (INIS)

    Tous, Jan; Blazek, Karel; Kucera, Miroslav; Nikl, Martin; Mares, Jiri A.

    2012-01-01

    Very thin scintillator imaging plates have recently become of great interest. In high resolution X-ray radiography, very thin scintillator layers of about 5–20 μm are used to achieve 2D-spatial resolutions below 1 μm. Thin screens can be prepared by mechanical polishing from single crystals or by epitaxial growth on single-crystal substrates using the Liquid Phase Epitaxy technique (LPE). Other types of screens (e.g. deposited powder) do no reach required spatial resolutions. This work compares LPE-grown YAG and LuAG scintillator films doped with different rare earth ions (Cerium, Terbium and Europium). Two different fluxes were used in the LPE growth procedure. These LPE films are compared to YAG:Ce and LuAG:Ce screens made from bulk single crystals. Relative light yield was detected by a highly sensitive CCD camera. Scintillator screens were excited by a micro-focus X-ray source and the generated light was gathered by the CCD camera’s optical system. Scintillator 2D-homogeneity is examined in an X-ray imaging setup also using the CCD camera.

  10. Interdiffusion in epitaxial, single-crystalline Au/Ag thin films studied by Auger electron spectroscopy sputter-depth profiling and positron annihilation

    International Nuclear Information System (INIS)

    Noah, Martin A.; Flötotto, David; Wang, Zumin; Reiner, Markus; Hugenschmidt, Christoph; Mittemeijer, Eric J.

    2016-01-01

    Interdiffusion in epitaxial, single-crystalline Au/Ag bilayered thin films on Si (001) substrates was investigated by Auger electron spectroscopy (AES) sputter-depth profiling and by in-situ positron annihilation Doppler broadening spectroscopy (DBS). By the combination of these techniques identification of the role of vacancy sources and sinks on interdiffusion in the Au/Ag films was possible. It was found that with precise knowledge of the concentration-dependent self-diffusion and impurity diffusion coefficients a distinction between the Darken-Manning treatment and Nernst-Planck treatment can be made, which is not possible on the basis of the determined concentration-depth profiles alone.

  11. Reversible pyroelectric and photogalvanic current in epitaxial Pb(Zr0.52Ti0.48)O3 thin films

    Science.gov (United States)

    Lee, J.; Esayan, S.; Prohaska, J.; Safari, A.

    1994-01-01

    The pyroelectric and photogalvanic effects have been studied in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. Photoinduced currents, which were completely reversible by electrical voltage, were observed. The photoinduced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 s) and slow (˜hours) relaxation times. The mechanisms of the photoinduced currents in PZT films and their possible applications in nondestructive readout ferroelectric memory are discussed.

  12. Reversal of the lattice structure in SrCoOx epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations

    OpenAIRE

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

    2013-01-01

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x = 2.5 - 3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases, i.e. the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator tran...

  13. Growth and characterization of epitaxial ultra-thin NbN films on 3C-SiC/Si substrate for terahertz applications

    International Nuclear Information System (INIS)

    Dochev, D; Desmaris, V; Pavolotsky, A; Meledin, D; Belitsky, V; Lai, Z; Henry, A; Janzen, E; Pippel, E; Woltersdorf, J

    2011-01-01

    We report on electrical properties and microstructure of epitaxial thin NbN films grown on 3C-SiC/Si substrates by means of reactive magnetron sputtering. A complete epitaxial growth at the NbN/3C-SiC interface has been confirmed by means of high resolution transmission electron microscopy (HRTEM) along with x-ray diffractometry (XRD). Resistivity measurements of the films have shown that the superconducting transition onset temperature (T C ) for the best specimen is 11.8 K. Using these epitaxial NbN films, we have fabricated submicron-size hot-electron bolometer (HEB) devices on 3C-SiC/Si substrate and performed their complete DC characterization. The observed critical temperature T C = 11.3 K and critical current density of about 2.5 MA cm -2 at 4.2 K of the submicron-size bridges were uniform across the sample. This suggests that the deposited NbN films possess the necessary homogeneity to sustain reliable hot-electron bolometer device fabrication for THz mixer applications.

  14. Growth and characterization of epitaxial ultra-thin NbN films on 3C-SiC/Si substrate for terahertz applications

    Energy Technology Data Exchange (ETDEWEB)

    Dochev, D; Desmaris, V; Pavolotsky, A; Meledin, D; Belitsky, V [Group for Advanced Receiver Development, Department of Earth and Space Sciences, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Lai, Z [Nanofabrication Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Henry, A; Janzen, E [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Pippel, E; Woltersdorf, J, E-mail: dimitar.dochev@chalmers.se [Max-Planck-Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany)

    2011-03-15

    We report on electrical properties and microstructure of epitaxial thin NbN films grown on 3C-SiC/Si substrates by means of reactive magnetron sputtering. A complete epitaxial growth at the NbN/3C-SiC interface has been confirmed by means of high resolution transmission electron microscopy (HRTEM) along with x-ray diffractometry (XRD). Resistivity measurements of the films have shown that the superconducting transition onset temperature (T{sub C}) for the best specimen is 11.8 K. Using these epitaxial NbN films, we have fabricated submicron-size hot-electron bolometer (HEB) devices on 3C-SiC/Si substrate and performed their complete DC characterization. The observed critical temperature T{sub C} = 11.3 K and critical current density of about 2.5 MA cm{sup -2} at 4.2 K of the submicron-size bridges were uniform across the sample. This suggests that the deposited NbN films possess the necessary homogeneity to sustain reliable hot-electron bolometer device fabrication for THz mixer applications.

  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. Characterization of structural defects in SnSe2 thin films grown by molecular beam epitaxy on GaAs (111)B substrates

    Science.gov (United States)

    Tracy, Brian D.; Li, Xiang; Liu, Xinyu; Furdyna, Jacek; Dobrowolska, Margaret; Smith, David J.

    2016-11-01

    Tin selenide thin films have been grown by molecular beam epitaxy on GaAs (111)B substrates at a growth temperature of 150 °C, and a microstructural study has been carried out, primarily using the technique of transmission electron microscopy. The Se:Sn flux ratio during growth was systematically varied and found to have a strong impact on the resultant crystal structure and quality. Low flux ratios (Se:Sn=3:1) led to defective films consisting primarily of SnSe, whereas high flux ratios (Se:Sn>10:1) gave higher quality, single-phase SnSe2. The structure of the monoselenide films was found to be consistent with the Space Group Pnma with the epitaxial growth relationship of [011]SnSe// [ 1 1 bar 0 ] GaAs, while the diselenide films were consistent with the Space Group P 3 bar m1 , and had the epitaxial growth relationship [ 2 1 bar 1 bar 0 ]SnSe2// [ 1 1 bar 0 ] GaAs.

  17. Epitaxial growth of bcc-FexCo100-x thin films on MgO(1 1 0) single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nishiyama, Tsutomu; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2010-01-01

    Fe x Co 100-x (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe x Co 100-x film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe x Co 100-x crystals with very small errors less than ±0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe 50 Co 50 /MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  18. Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2010-07-15

    Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  19. Epitaxy physical principles and technical implementation

    CERN Document Server

    Herman, Marian A; Sitter, Helmut

    2004-01-01

    Epitaxy provides readers with a comprehensive treatment of the modern models and modifications of epitaxy, together with the relevant experimental and technological framework. This advanced textbook describes all important aspects of the epitaxial growth processes of solid films on crystalline substrates, including a section on heteroepitaxy. It covers and discusses in details the most important epitaxial growth techniques, which are currently widely used in basic research as well as in manufacturing processes of devices, namely solid-phase epitaxy, liquid-phase epitaxy, vapor-phase epitaxy, including metal-organic vapor-phase epitaxy and molecular-beam epitaxy. Epitaxy’s coverage of science and texhnology thin-film is intended to fill the need for a comprehensive reference and text examining the variety of problems related to the physical foundations and technical implementation of epitaxial crystallization. It is intended for undergraduate students, PhD students, research scientists, lecturers and practic...

  20. Low-field tunnel-type magnetoresistance properties of polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 thin films

    CERN Document Server

    Shim, I B; Choi, S Y

    2000-01-01

    The low-field tunnel-type magnetoresistance (TMB) properties of sol-gel derived polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 (LSMO) thin films were investigated. The polycrystalline thin films were fabricated on Si (100) with a thermally oxidized SiO sub 2 layer while the epitaxial thin films were grown on LaAlO sub 3 (001) single-crystal substrates. The epitaxial thin films displayed both typical intrinsic colossal magnetoresistance (CMR) and abnormal extrinsic tunnel-type magnetoresistance behaviors. Tunnel-type MR ratio as high as 0.4% were observed in the polycrystalline thin films at a field of 120 Oe at room temperature (300 K) whereas the ratios were less than 0.1% for the epitaxial films in the same field range. The low-field tunnel-type MR of polycrystalline LSMO/SiO sub 2 ?Si (100) thin films originated from the behaviors of the grain-boundary properties.

  1. Effects of strain on the magnetic and transport properties of the epitaxial La0.5Ca0.5MnO3 thin films

    International Nuclear Information System (INIS)

    Zarifi, M.; Kameli, P.; Ehsani, M.H.; Ahmadvand, H.; Salamati, H.

    2016-01-01

    The epitaxial strain can considerably modify the physical properties of thin films compared to the bulk. This paper reports the effects of substrate-induced strain on La 0.5 Ca 0.5 MnO 3 (LCMO) thin films, grown on (100) SrTiO 3 (STO) and LaAlO 3 (LAO) substrates by pulsed laser deposition technique. Transport and magnetic properties were found to be strongly dependent on strain type. It is also shown that compressive (tensile) strain leads to the increase (decrease) in the magnetization of the films. Moreover, it was observed that all LCMO films deposited on both LAO and STO substrates behave as an insulator, but LCMO/LAO thin films with compressive strain have lower resistivity than LCMO/STO thin films with tensile strain. Applying magnetic field to LCMO/STO thin films with thickness of 25 and 50 nm leads to very small change in the resistivity, while the effects of magnetic field on the sample with thickness of 125 nm leads to an insulator–metal transition. For LCMO/LAO thin films, the magnetic field has a strong impact on the resistivity of samples. The results show that the magnetoresistance (MR) is enhanced by increasing film thickness for LCMO/LAO samples, due to the relatively stronger phase separation. For LCMO/STO thin films MR is drastically decreased by reduction of film thickness, which is attributed to the enhancement of the charge–orbital order (CO–O) accompanying the complex spin order (the so-called CE type). The changes of the antiferromagnetic structure from the CE to C type and the enhancement of the CE type could be attributed to the in-plane compressive and tensile strain, respectively. - Highlights: • Epitaxial La 0.5 Ca 0.5 MnO 3 thin films, grown on (100) SrTiO 3 and LaAlO 3 substrates. • The compressive strain leads to the increase in the magnetization of the films. • The tensile strain leads to the decrease in the magnetization of the films. • The magnetoresistance is enhanced by increasing film thickness.

  2. X-ray characterization of CdO thin films grown on a-, c-, r- and m-plane sapphire by metalorganic vapour phase-epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zuniga-Perez, J.; Martinez-Tomas, C.; Munoz-Sanjose, V. [Departamento de Fisica Aplicada y Electromagnetismo, Universitat de Valencia, C/Dr. Moliner 50, 46100 Burjassot (Spain)

    2005-02-01

    CdO thin films have been grown on a-plane (11 anti 20), c-plane (0001), r-plane (01 anti 12) and m-plane (10 anti 10) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including {theta}-2{theta} scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the presence or absence of extended defects. The rocking curves indicate that high quality thin films, in terms of tilt and twist, can be obtained on r-, c- and m-plane sapphire, while further improvement is needed over the a-orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. X-ray characterization of CdO thin films grown on a-, c-, r- and m-plane sapphire by metalorganic vapour phase-epitaxy

    International Nuclear Information System (INIS)

    Zuniga-Perez, J.; Martinez-Tomas, C.; Munoz-Sanjose, V.

    2005-01-01

    CdO thin films have been grown on a-plane (11 anti 20), c-plane (0001), r-plane (01 anti 12) and m-plane (10 anti 10) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including θ-2θ scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the presence or absence of extended defects. The rocking curves indicate that high quality thin films, in terms of tilt and twist, can be obtained on r-, c- and m-plane sapphire, while further improvement is needed over the a-orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Effect of epitaxial strain and lattice mismatch on magnetic and transport behaviors in metamagnetic FeRh thin films

    Science.gov (United States)

    Xie, Yali; Zhan, Qingfeng; Shang, Tian; Yang, Huali; Wang, Baomin; Tang, Jin; Li, Run-Wei

    2017-05-01

    We grew 80 nm FeRh films on different single crystals with various lattice constants. FeRh films on SrTiO3 (STO) and MgO substrates exhibit an epitaxial growth of 45° in-plane structure rotation. In contrast, FeRh on LaAlO3 (LAO) displays a mixed epitaxial growth of both 45° in-plane structure rotation and cube-on-cube relationships. Due to the different epitaxial growth strains and lattice mismatch values, the critical temperature for the magnetic phase transition of FeRh can be changed between 405 and 360 K. In addition, the external magnetic field can shift this critical temperature to low temperature in different rates for FeRh films grown on different substrates. The magnetoresistance appears a maximum value at different temperatures between 320 and 380 K for FeRh films grown on different substrates.

  5. Effect of epitaxial strain and lattice mismatch on magnetic and transport behaviors in metamagnetic FeRh thin films

    Directory of Open Access Journals (Sweden)

    Yali Xie

    2017-05-01

    Full Text Available We grew 80 nm FeRh films on different single crystals with various lattice constants. FeRh films on SrTiO3 (STO and MgO substrates exhibit an epitaxial growth of 45° in-plane structure rotation. In contrast, FeRh on LaAlO3 (LAO displays a mixed epitaxial growth of both 45° in-plane structure rotation and cube-on-cube relationships. Due to the different epitaxial growth strains and lattice mismatch values, the critical temperature for the magnetic phase transition of FeRh can be changed between 405 and 360 K. In addition, the external magnetic field can shift this critical temperature to low temperature in different rates for FeRh films grown on different substrates. The magnetoresistance appears a maximum value at different temperatures between 320 and 380 K for FeRh films grown on different substrates.

  6. Epitaxial Fe3Si/Ge/Fe3Si thin film multilayers grown on GaAs(001)

    International Nuclear Information System (INIS)

    Jenichen, B.; Herfort, J.; Jahn, U.; Trampert, A.; Riechert, H.

    2014-01-01

    We demonstrate Fe 3 Si/Ge/Fe 3 Si/GaAs(001) structures grown by molecular-beam epitaxy and characterized by transmission electron microscopy, electron backscattered diffraction, and X-ray diffraction. The bottom Fe 3 Si epitaxial film on GaAs is always single crystalline. The structural properties of the Ge film and the top Fe 3 Si layer depend on the substrate temperature during Ge deposition. Different orientation distributions of the grains in the Ge and the upper Fe 3 Si film were found. The low substrate temperature T s of 150 °C during Ge deposition ensures sharp interfaces, however, results in predominantly amorphous films. We find that the intermediate T s (225 °C) leads to a largely [111] oriented upper Fe 3 Si layer and polycrystal films. The high T s of 325 °C stabilizes the [001] oriented epitaxial layer structure, i.e., delivers smooth interfaces and single crystal films over as much as 80% of the surface area. - Highlights: • Fe 3 Si/Ge/Fe 3 Si/GaAs(001) structures are grown by MBE. • The bottom Fe 3 Si film is always single crystalline. • The properties of the Ge film depend on the substrate temperature during deposition. • Optimum growth conditions lead to almost perfect epitaxy of Ge on Fe 3 Si

  7. Effects of strain on the magnetic and transport properties of the epitaxial La0.5Ca0.5MnO3 thin films

    Science.gov (United States)

    Zarifi, M.; Kameli, P.; Ehsani, M. H.; Ahmadvand, H.; Salamati, H.

    2016-12-01

    The epitaxial strain can considerably modify the physical properties of thin films compared to the bulk. This paper reports the effects of substrate-induced strain on La0.5Ca0.5MnO3 (LCMO) thin films, grown on (100) SrTiO3 (STO) and LaAlO3 (LAO) substrates by pulsed laser deposition technique. Transport and magnetic properties were found to be strongly dependent on strain type. It is also shown that compressive (tensile) strain leads to the increase (decrease) in the magnetization of the films. Moreover, it was observed that all LCMO films deposited on both LAO and STO substrates behave as an insulator, but LCMO/LAO thin films with compressive strain have lower resistivity than LCMO/STO thin films with tensile strain. Applying magnetic field to LCMO/STO thin films with thickness of 25 and 50 nm leads to very small change in the resistivity, while the effects of magnetic field on the sample with thickness of 125 nm leads to an insulator-metal transition. For LCMO/LAO thin films, the magnetic field has a strong impact on the resistivity of samples. The results show that the magnetoresistance (MR) is enhanced by increasing film thickness for LCMO/LAO samples, due to the relatively stronger phase separation. For LCMO/STO thin films MR is drastically decreased by reduction of film thickness, which is attributed to the enhancement of the charge-orbital order (CO-O) accompanying the complex spin order (the so-called CE type). The changes of the antiferromagnetic structure from the CE to C type and the enhancement of the CE type could be attributed to the in-plane compressive and tensile strain, respectively.

  8. High-Performance Flexible Thin-Film Transistors Based on Single-Crystal-like Silicon Epitaxially Grown on Metal Tape by Roll-to-Roll Continuous Deposition Process.

    Science.gov (United States)

    Gao, Ying; Asadirad, Mojtaba; Yao, Yao; Dutta, Pavel; Galstyan, Eduard; Shervin, Shahab; Lee, Keon-Hwa; Pouladi, Sara; Sun, Sicong; Li, Yongkuan; Rathi, Monika; Ryou, Jae-Hyun; Selvamanickam, Venkat

    2016-11-02

    Single-crystal-like silicon (Si) thin films on bendable and scalable substrates via direct deposition are a promising material platform for high-performance and cost-effective devices of flexible electronics. However, due to the thick and unintentionally highly doped semiconductor layer, the operation of transistors has been hampered. We report the first demonstration of high-performance flexible thin-film transistors (TFTs) using single-crystal-like Si thin films with a field-effect mobility of ∼200 cm 2 /V·s and saturation current, I/l W > 50 μA/μm, which are orders-of-magnitude higher than the device characteristics of conventional flexible TFTs. The Si thin films with a (001) plane grown on a metal tape by a "seed and epitaxy" technique show nearly single-crystalline properties characterized by X-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction, and transmission electron microscopy. The realization of flexible and high-performance Si TFTs can establish a new pathway for extended applications of flexible electronics such as amplification and digital circuits, more than currently dominant display switches.

  9. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    International Nuclear Information System (INIS)

    Takahashi, Jumpei; Oka, Daichi; Hirose, Yasushi; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya; Nakao, Shoichiro; Harayama, Isao; Sekiba, Daiichiro

    2015-01-01

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO x N y ) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO x N y thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO x N y thin films monotonically decreased from the order of 10 5  Ω cm to 10 −4  Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO x N y phase, which has not yet been reported in Co 2+ /Co 3+ mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO x N y phase, on the 10 −3  Ω cm order, may have originated from the intermediate spin state of Co 3+ stabilized by the lowered crystal field symmetry of the CoO 6−n N n octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO x N y films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides

  10. Growth and characterization of β-Ga2O3 thin films by molecular beam epitaxy for deep-UV photodetectors

    Science.gov (United States)

    Ghose, Susmita; Rahman, Shafiqur; Hong, Liang; Rojas-Ramirez, Juan Salvador; Jin, Hanbyul; Park, Kibog; Klie, Robert; Droopad, Ravi

    2017-09-01

    The growth of high quality epitaxial beta-gallium oxide (β-Ga2O3) using a compound source by molecular beam epitaxy has been demonstrated on c-plane sapphire (Al2O3) substrates. The compound source provides oxidized gallium molecules in addition to oxygen when heated from an iridium crucible in a high temperature effusion cell enabling a lower heat of formation for the growth of Ga2O3, resulting in a more efficient growth process. This source also enabled the growth of crystalline β-Ga2O3 without the need for additional oxygen. The influence of the substrate temperatures on the crystal structure and quality, chemical bonding, surface morphology, and optical properties has been systematically evaluated by x-ray diffraction, scanning transmission electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, spectroscopic ellipsometry, and UV-vis spectroscopy. Under optimized growth conditions, all films exhibited pure (" separators="|2 ¯01 ) oriented β-Ga2O3 thin films with six-fold rotational symmetry when grown on a sapphire substrate. The thin films demonstrated significant absorption in the deep-ultraviolet (UV) region with an optical bandgap around 5.0 eV and a refractive index of 1.9. A deep-UV photodetector fabricated on the high quality β-Ga2O3 thin film exhibits high resistance and small dark current (4.25 nA) with expected photoresponse for 254 nm UV light irradiation suggesting that the material grown using the compound source is a potential candidate for deep-ultraviolet photodetectors.

  11. Orientation-dependent physical properties of layered perovskite La{sub 1.3}Sr{sub 1.7}Mn{sub 2}O{sub 7} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Li-Wei; Guo, Bing; Chen, Chang-Le, E-mail: chenchl@nwpu.edu.cn; Luo, Bing-Cheng; Dong, Xiang-Lei; Jin, Ke-Xin

    2017-04-01

    In this paper, the resistivity and magnetization of orientation-engineered layered perovskite La{sub 1.3}Sr{sub 1.7}Mn{sub 2}O{sub 7} epitaxial thin films have been investigated. Epitaxial thin films were deposited on single-crystalline LaAlO{sub 3} (LAO) (001), (110) and (111) substrates by pulse laser deposition (PLD) technique. It is found that only the (100)-oriented thin film performs insulator behavior, whereas the (110) and (111)-oriented thin films exhibit obvious metal-insulator transition at 70 K and between 85 and 120 K, respectively. Moreover, the same spin freezing temperature and different spin-glass-like transition temperatures have been observed in various oriented films. The observed experimental results were discussed according to the electron-transport mechanism and spin dynamics.

  12. FY 1997 report on the study on lamination control technology for functional multi-element oxide thin films by complex beam epitaxy (CxBE) process; 1997 nendo chosa hokokusho (sakutaisen epitaxy (CxBE) ho ni yoru kinosei tagenso sankabutsu usumaku no sekiso seigyo gijutsu ni kansuru kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Complex beam epitaxy (CxBE) process was proposed and demonstrated as new deposition process of multi-element oxide thin films. This process radiates excimer laser onto a metal complex target of ethylenediamine-tetraacetate complex under reduced pressure oxygen atmosphere condition in a reaction vessel to supply raw material onto a heated substrate. This process allowed deposition of YBCO123 phase hetero-epitaxial film onto a single-crystalline SrTiO3 substrate. This process was proved to be promising through study on crystal orientation, composition transcription and surface smoothness of the obtained oxide thin films. In addition, epitaxial ZnO film was also deposited onto a single crystalline Al2O3 substrate by this process. The relation between the obtained film and substrate epitaxy was examined, and photoluminescence of specimens was measured by triple wave of Nd:YAG laser. As a result, it was clarified that the epitaxial ZnO film prepared by this process is useful as laser material. 60 refs., 48 figs., 5 tabs.

  13. Optical and electrical properties of semiconducting BaSi2 thin films on Si substrates grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Morita, K.; Inomata, Y.; Suemasu, T.

    2006-01-01

    The electrical properties and optical absorption (OA) spectra of undoped BaSi 2 films grown by molecular beam epitaxy were investigated The electron density and mobility of BaSi 2 grown epitaxially on Si(111) were 5 x 10 15 cm -3 and 820 cm 2 /V.s at room temperature, respectively. The conduction-band discontinuity at the BaSi 2 /Si heterojunction was estimated to be 0.7 eV from the current-voltage characteristics of n-BaSi 2 /n-Si isotype diodes. OA spectra were measured on polycrystalline BaSi 2 films grown on transparent fused silica substrates with predeposited polycrystalline Si layer. The indirect absorption edge was derived to be 1.3 eV, and the optical absorption coefficient reached 10 5 cm -1 at 1.5 eV

  14. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 {sup 0}C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc{sub r}eases in the film. The Ni film prepared at 100 {sup 0}C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  15. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 0 C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc r eases in the film. The Ni film prepared at 100 0 C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  16. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films

    Directory of Open Access Journals (Sweden)

    Huaping Wu

    2016-01-01

    Full Text Available The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110 orientation leads to a lower symmetry and more complicated phase transition than the (111 orientation in BaTiO3 films. The increase of compressive strain will dramatically enhance the Curie temperature TC of (110-oriented BaTiO3 films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110- and (111-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

  17. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huaping, E-mail: wuhuaping@gmail.com, E-mail: hpwu@zjut.edu.cn [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Ma, Xuefu; Zhang, Zheng; Zeng, Jun; Chai, Guozhong [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Wang, Jie [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027 (China)

    2016-01-15

    The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110) orientation leads to a lower symmetry and more complicated phase transition than the (111) orientation in BaTiO{sub 3} films. The increase of compressive strain will dramatically enhance the Curie temperature T{sub C} of (110)-oriented BaTiO{sub 3} films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110)- and (111)-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

  18. Epitaxial c-axis oriented BaTiO{sub 3} thin films on SrTiO{sub 3}-buffered Si(001) by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Thong Q.; McDaniel, Martin D.; Ekerdt, John G., E-mail: ekerdt@che.utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Posadas, Agham B.; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States); Hu, Chengqing; Yu, Edward T. [Department of Electrical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Bruley, John [IBM Research Division, Yorktown Heights, New York 10593 (United States)

    2014-02-24

    Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO{sub 3} (BTO) on Si(001) using a thin (1.6 nm) buffer layer of SrTiO{sub 3} (STO) grown by molecular beam epitaxy is reported. The ALD growth of crystalline BTO films at 225  °C used barium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and water as co-reactants. X-ray diffraction (XRD) reveals a high degree of crystallinity and c-axis orientation of as-deposited BTO films. Crystallinity is improved after vacuum annealing at 600  °C. Two-dimensional XRD confirms the tetragonal structure and orientation of 7–20-nm thick films. The effect of the annealing process on the BTO structure is discussed. A clean STO/Si interface is found using in-situ X-ray photoelectron spectroscopy and confirmed by cross-sectional scanning transmission electron microscopy. The capacitance-voltage characteristics of 7–20 nm-thick BTO films are examined and show an effective dielectric constant of ∼660 for the heterostructure.

  19. Structural and dielectric properties of (001) and (111)-oriented BaZr0.2Ti0.8O3 epitaxial thin films

    International Nuclear Information System (INIS)

    Ventura, J.; Fina, I.; Ferrater, C.; Langenberg, E.; Coy, L.E.; Polo, M.C.; Garcia-Cuenca, M.V.; Fabrega, L.; Varela, M.

    2010-01-01

    We have grown and characterized BaZr 0.2 Ti 0.8 O 3 (BZT) epitaxial thin films deposited on (001) and (111)-oriented SrRuO 3 -buffered SrTiO 3 substrates by pulsed laser deposition. Structural and morphological characterizations were performed using X-ray diffractometry and atomic force microscopy, respectively. A cube-on-cube epitaxial relationship was ascertained from the θ-2θ and φ diffractograms in both (001) and (111)-oriented films. The (001)-oriented films showed a smooth granular morphology, whereas the faceted pyramid-like crystallites of the (111)-oriented films led to a rough surface. The dielectric response of BZT at room temperature was measured along the growth direction. The films were found to be ferroelectric, although a well-saturated hysteresis loop was obtained only for the (001)-oriented films. High leakage currents were observed for the (111) orientation, likely associated to charge transport along the boundaries of its crystallites. The remanent polarization, coercive field, dielectric constant, and relative change of dielectric permittivity (tunability) of (111)-oriented BZT were higher than those of (001)-oriented BZT.

  20. Epitaxial c-axis oriented BaTiO3 thin films on SrTiO3-buffered Si(001) by atomic layer deposition

    International Nuclear Information System (INIS)

    Ngo, Thong Q.; McDaniel, Martin D.; Ekerdt, John G.; Posadas, Agham B.; Demkov, Alexander A.; Hu, Chengqing; Yu, Edward T.; Bruley, John

    2014-01-01

    Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO 3 (BTO) on Si(001) using a thin (1.6 nm) buffer layer of SrTiO 3 (STO) grown by molecular beam epitaxy is reported. The ALD growth of crystalline BTO films at 225  °C used barium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and water as co-reactants. X-ray diffraction (XRD) reveals a high degree of crystallinity and c-axis orientation of as-deposited BTO films. Crystallinity is improved after vacuum annealing at 600  °C. Two-dimensional XRD confirms the tetragonal structure and orientation of 7–20-nm thick films. The effect of the annealing process on the BTO structure is discussed. A clean STO/Si interface is found using in-situ X-ray photoelectron spectroscopy and confirmed by cross-sectional scanning transmission electron microscopy. The capacitance-voltage characteristics of 7–20 nm-thick BTO films are examined and show an effective dielectric constant of ∼660 for the heterostructure

  1. Fabrication of GaN epitaxial thin film on InGaZnO4 single-crystalline buffer layer

    International Nuclear Information System (INIS)

    Shinozaki, Tomomasa; Nomura, Kenji; Katase, Takayoshi; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2010-01-01

    Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO 4 (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH 3 source. The epitaxial relationships are (0001) GaN //(0001) IGZO //(111) YSZ in out-of-plane and [112-bar 0] GaN //[112-bar 0] IGZO //[11-bar 0] YSZ in in-plane. This is different from those reported for GaN on many oxide crystals; the in-plane orientation of GaN crystal lattice is rotated by 30 o with respect to those of oxide substrates except for ZnO. Although these GaN films showed relatively large tilting and twisting angles, which would be due to the reaction between GaN and IGZO, the GaN films grown on the sc-IGZO buffer layers exhibited stronger band-edge photoluminescence than GaN grown on a low-temperature GaN buffer layer.

  2. Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

    International Nuclear Information System (INIS)

    Nishiyama, Tsutomu; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    FeCo epitaxial films were prepared on MgO(111), SrTiO 3 (111), and Al 2 O 3 (0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy. The effects of insulating substrate material on the film growth process and the structures were investigated. FeCo(110) bcc films grow on MgO substrates with two type domains, Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) relationships. On the contrary, FeCo films grown on SrTiO 3 and Al 2 O 3 substrates include FeCo(111) bcc crystal in addition to the FeCo(110) bcc crystals with NW and KS relationships. The FeCo(111) bcc crystal consists of two type domains whose orientations are rotated around the film normal by 180 deg. each other. The out-of-plane and the in-plane lattice spacings of FeCo(110) bcc and FeCo(111) bcc crystals formed on the insulating substrates are in agreement with those of the bulk Fe 50 Co 50 (at. %) crystal with small errors ranging between +0.2% and +0.4%, showing that the strains in the epitaxial films are very small.

  3. Strong magnetorefractive effect in epitaxial La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hrabovsky, D. [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, Bellaterra 08193, Catalonia (Spain); Herranz, G., E-mail: gherranz@icmab.e [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, Bellaterra 08193, Catalonia (Spain); Caicedo, J.M.; Infante, I.C.; Sanchez, F.; Fontcuberta, J. [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, Bellaterra 08193, Catalonia (Spain)

    2010-05-15

    We report here on the magneto-optical characterization of epitaxial La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films. We observe that the magnetic field dependence of the magneto-optical signal measured in transverse Kerr geometry can be decomposed into even and odd contributions which evolve differently with the temperature. We demonstrate that whereas the odd component is proportional to the magnetization, the even contribution is related to the magnetorefractive effect, which is caused by the changes of the refractive index and optical conductivity with the magnetic field. This phenomenon, previously reported only at infrared wavelengths in some spin valves and granular systems, is shown here to be very relevant at visible frequencies for the colossal magnetoresistance manganites, thus allowing simultaneous optical characterization of the magnetic and magnetotransport properties. We argue that these characteristics result from inherent transport properties of these strongly correlated ferromagnetic oxides.

  4. Misfit strain relaxation in (Ba0.60Sr0.40)TiO3 epitaxial thin films on orthorhombic NdGaO3 substrates

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.

    2006-07-01

    Strain relaxation in (Ba0.60Sr0.40)TiO3 (BST) thin films on ⟨110⟩ orthorhombic NdGaO3 substrates is investigated by x-ray diffractometry. Pole figure analysis indicates a [010]BST∥[1¯10]NGO and [001]BST∥[001]NGO in-plane and [100]BST∥[100]NGO out-of-plane epitaxial relationship. The residual strains are relaxed at h ˜200nm, and for h >600nm, films are essentially strain free. Two independent dislocations mechanisms operate to relieve the anisotropic misfit strains along the principal directions. The critical thickness for misfit dislocation formation along [001] and [010] are 11 and 15nm, respectively. Stress analysis indicates deviation from linear elasticity for h <200. The films with 10

  5. Deposition of epitaxial thin films of Nd1.85Ce0.15CuO4-y by laser ablation

    International Nuclear Information System (INIS)

    Gupta, A.; Koren, G.; Tsuei, C.C.; Segmuller, A.; McGuire, T.R.

    1989-01-01

    Thin films of the electron-doped superconductor Nd 1.85 Ce 0.15 CuO 4-y have been deposited on (100) SrTiO 3 substrates at 780 degree C using the laser ablation technique. The deposited films are very smooth and show epitaxial growth with the c axis normal to the substrate. The transport properties of the films are very sensitive to the concentration of oxygen vacancies. Films deposited and cooled in the presence of 150 mTorr O 2 exhibit localization behavior with no evidence of superconductivity down to 5 K. Superconductivity is observed on vacuum annealing the films in situ after deposition. Films with optimum concentration of oxygen vacancies show a superconducting onset temperature of 21 K and T c (R=0) of 20 K, with a critical current density of 2x10 5 A/cm 2 at 5.5 K in zero magnetic field

  6. Reversal of the Lattice Structure in SrCoOx Epitaxial Thin Films Studied by Real-Time Optical Spectroscopy and First-Principles Calculations

    Science.gov (United States)

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

    2013-08-01

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

  7. Reversal of the lattice structure in SrCoO(x) epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.

    Science.gov (United States)

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S S Ambrose; Cooper, Valentino R; Rabe, Karin M; Lee, Ho Nyung

    2013-08-30

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoO(x) (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

  8. Strain Influence on the Oxygen Electrocatalysis of the (100)-Oriented Epitaxial La 2 NiO 4+δ Thin Films at Elevated Temperatures

    KAUST Repository

    Lee, Dongkyu; Grimaud, Alexis; Crumlin, Ethan J.; Mezghani, Khaled; Habib, Mohamed A.; Feng, Zhenxing; Hong, Wesley T.; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

    2013-01-01

    Ruddlesden-Popper materials such as La2NiO4+δ (LNO) have high activities for surface oxygen exchange kinetics promising for solid oxide fuel cells and oxygen permeation membranes. Here we report the synthesis of the (100)tetragonal-oriented epitaxial LNO thin films prepared by pulsed laser deposition. The surface oxygen exchange kinetics determined from electrochemical impedance spectroscopy (EIS) were found to increase with decreasing film thickness from 390 to 14 nm. No significant change of the surface chemistry with different film thicknesses was observed using ex situ auger electron spectroscopy (AES). Increasing volumetric strains in the LNO films at elevated temperatures determined from in situ high-resolution X-ray diffraction (HRXRD) were correlated with increasing surface exchange kinetics and decreasing film thickness. Volumetric strains may alter the formation energy of interstitial oxygen and influence on the surface oxygen exchange kinetics of the LNO films. © 2013 American Chemical Society.

  9. Strain Influence on the Oxygen Electrocatalysis of the (100)-Oriented Epitaxial La 2 NiO 4+δ Thin Films at Elevated Temperatures

    KAUST Repository

    Lee, Dongkyu

    2013-09-19

    Ruddlesden-Popper materials such as La2NiO4+δ (LNO) have high activities for surface oxygen exchange kinetics promising for solid oxide fuel cells and oxygen permeation membranes. Here we report the synthesis of the (100)tetragonal-oriented epitaxial LNO thin films prepared by pulsed laser deposition. The surface oxygen exchange kinetics determined from electrochemical impedance spectroscopy (EIS) were found to increase with decreasing film thickness from 390 to 14 nm. No significant change of the surface chemistry with different film thicknesses was observed using ex situ auger electron spectroscopy (AES). Increasing volumetric strains in the LNO films at elevated temperatures determined from in situ high-resolution X-ray diffraction (HRXRD) were correlated with increasing surface exchange kinetics and decreasing film thickness. Volumetric strains may alter the formation energy of interstitial oxygen and influence on the surface oxygen exchange kinetics of the LNO films. © 2013 American Chemical Society.

  10. Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)

    2015-07-01

    The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.

  11. Lattice distortion and strain relaxation in epitaxial thin films of multiferroic TbMnO3 probed by X-ray diffractometry and micro-Raman spectroscopy

    Science.gov (United States)

    Hu, Y.; Stender, D.; Medarde, M.; Lippert, T.; Wokaun, A.; Schneider, C. W.

    2013-08-01

    A detailed structural XRD analysis of (1 1 0)-oriented TbMnO3 thin films grown on (1 1 0)-YAlO3 substrates shows the co-existence of a strained and relaxed "sublayer" within the films due to strain relaxation during epitaxial growth by pulsed laser deposition. The substrate-film lattice mismatch yields a compressive strain anisotropy along the two in-plane directions, i.e. [1 -1 0] and [0 0 1] and a monoclinic distortion. A further manifestation of the growth-induced strain is the hardening of Raman active modes as a result of changed atomic motions along the [1 -1 0] and [0 0 1] directions.

  12. Lattice distortion and strain relaxation in epitaxial thin films of multiferroic TbMnO{sub 3} probed by X-ray diffractometry and micro-Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Y.; Stender, D. [Paul Scherrer Institute, General Energy Research Department, 5232 Villigen-PSI (Switzerland); Medarde, M. [Paul Scherrer Institute, Laboratory for Developments and Methods, 5232 Villigen-PSI (Switzerland); Lippert, T., E-mail: thomas.lippert@psi.ch [Paul Scherrer Institute, General Energy Research Department, 5232 Villigen-PSI (Switzerland); Wokaun, A.; Schneider, C.W. [Paul Scherrer Institute, General Energy Research Department, 5232 Villigen-PSI (Switzerland)

    2013-08-01

    A detailed structural XRD analysis of (1 1 0)-oriented TbMnO{sub 3} thin films grown on (1 1 0)-YAlO{sub 3} substrates shows the co-existence of a strained and relaxed “sublayer” within the films due to strain relaxation during epitaxial growth by pulsed laser deposition. The substrate-film lattice mismatch yields a compressive strain anisotropy along the two in-plane directions, i.e. [1 −1 0] and [0 0 1] and a monoclinic distortion. A further manifestation of the growth-induced strain is the hardening of Raman active modes as a result of changed atomic motions along the [1 −1 0] and [0 0 1] directions.

  13. Optical investigation of atomic steps in ultra-thin InGaAs/InP quantum wells grown by vapor levitation epitaxy

    International Nuclear Information System (INIS)

    Morais, P.C.

    1988-09-01

    Ultra-thin InGaAs/InP single-quantum-well structures, grown by chloride transport vapor levitation epitaxy, have been investigated by low temperature photoluminescence (PL). Well resolved peaks are observed in the PL spectra which we attribute to monolayer (a/2=2.93 A) variations in quantum well (QW) thickness. Separate peak positions for QW thicknesses corresponding to 2-6 monolayers have been determined, providing an unambiguous thickness calibration for spectral shifts due to quantum confinement. The PL peak corresponding to two monolayers occurs at 1.314 eV corresponding to an energy shift of 524 meV. Experimental data agree very well with a simple effective-mass theory. (author) [pt

  14. Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films

    Science.gov (United States)

    Hu, S.; Seidel, J.

    2016-08-01

    Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

  15. Epitaxial La2/3Sr1/3MnO3 thin films with unconventional magnetic and electric properties near the Curie temperature

    International Nuclear Information System (INIS)

    Signorini, L.; Riva, M.; Cantoni, M.; Bertacco, R.; Ciccacci, F.

    2006-01-01

    We used Pulsed Laser Deposition (PLD) in oxidizing environment to epitaxially grow optimally doped manganite La 2/3 Sr 1/3 MnO 3 (LSMO) thin films over a (001) oriented SrTiO 3 substrate. Synthesized samples show good room temperature magnetic properties accompanied by a peculiar extension of the metallic conduction regime to temperatures higher than the Curie point. In this paper we present a study of the dependence of transport and magnetic properties of LSMO thin films on the oxygen pressure during PLD growth. We show how interaction of the growing films with O 2 molecules is fundamental for a correct synthesis and in which way it is possible to adjust PLD experimental parameters in order to tune LSMO thin film properties. The persistence of the metallic conduction regime above the Curie temperature indicates some minor changes of the electronic structure near the Fermi level, which is responsible for the half-metallic behavior of LSMO at low temperature. This feature is rather intriguing from the technological point of view, as it could pave the way to the increase of operating temperature of devices based on LSMO

  16. On the dielectric and optical properties of surface-anchored metal-organic frameworks: A study on epitaxially grown thin films

    Science.gov (United States)

    Redel, Engelbert; Wang, Zhengbang; Walheim, Stefan; Liu, Jinxuan; Gliemann, Hartmut; Wöll, Christof

    2013-08-01

    We determine the optical constants of two highly porous, crystalline metal-organic frameworks (MOFs). Since it is problematic to determine the optical constants for the standard powder modification of these porous solids, we instead use surface-anchored metal-organic frameworks (SURMOFs). These MOF thin films are grown using liquid phase epitaxy (LPE) on modified silicon substrates. The produced SURMOF thin films exhibit good optical properties; these porous coatings are smooth as well as crack-free, they do not scatter visible light, and they have a homogenous interference color over the entire sample. Therefore, spectroscopic ellipsometry (SE) can be used in a straightforward fashion to determine the corresponding SURMOF optical properties. After careful removal of the solvent molecules used in the fabrication process as well as the residual water adsorbed in the voids of this highly porous solid, we determine an optical constant of n = 1.39 at a wavelength of 750 nm for HKUST-1 (stands for Hong Kong University of Science and Technology-1; and was first discovered there) or [Cu3(BTC)2]. After exposing these SURMOF thin films to moisture/EtOH atmosphere, the refractive index (n) increases to n = 1.55-1.6. This dependence of the optical properties on water/EtOH adsorption demonstrates the potential of such SURMOF materials for optical sensing.

  17. Optical characterization of epitaxial single crystal CdTe thin films on Al{sub 2}O{sub 3} (0001) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, S.M.; Devenyi, G.A., E-mail: devenyga@mcmaster.ca; Jarvis, V.M.; Meinander, K.; Haapamaki, C.M.; Kuyanov, P.; Gerber, M.; LaPierre, R.R.; Preston, J.S.

    2014-11-03

    The optoelectronic properties of single crystal CdTe thin films were investigated by photoluminescence spectroscopy, photoreflectance spectroscopy and variable angle spectroscopic ellipsometry. The room temperature bandgap was measured to be 1.51 eV and was consistent between spectroscopic measurements and previously reported values. Breadth of bandgap emission was consistent with high quality material. Low temperature photoluminescence spectra indicated a dominant emission consistent with bound excitons. Emissions corresponding to self-compensation defects, doping and contaminants were not found. Variable angle spectroscopic ellipsometry measurements over the near-UV to infrared range demonstrated sharp resonance peaks. All spectroscopic measurements indicate high quality thin film material of comparable or better quality than bulk CdTe. - Highlights: • High quality epitaxial CdTe thin films were grown. • Two dimensional X-ray diffraction characterization confirmed single crystal material. • Photoluminescence indicated low defect density when compared to bulk single crystals. • Optical characterization indicated the presence of room temperature excitons.

  18. Perpendicular magnetic anisotropy of non-epitaxial hexagonal Co{sub 50}Pt{sub 50} thin films prepared at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, F.T., E-mail: ftyuan@gmail.com [iSentek Ltd., Advanced Sensor Laboratory, New Taipei City 22101, Taiwan (China); Chang, H.W., E-mail: wei0208@gmail.com [Department of Applied Physics, Tunghai University, Taichung 40704, Taiwan (China); Lee, P.Y.; Chang, C.Y. [Department of Applied Physics, Tunghai University, Taichung 40704, Taiwan (China); Chi, C.C. [Department of Materials Sciences and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Ouyang, H., E-mail: houyang@mx.nthu.edu.tw [Department of Materials Sciences and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2015-04-15

    Highlights: • In this paper, we propose a non-epitaxially grown PMA thin film of disorder hexagonal Co{sub 50}Pt{sub 50} which can satisfy all the requirements at once. • Although the preparation temperature is at room temperature and no post annealing is required, the film also shows good thermal stability up to 400 °C. • Moreover, the easy-controlling single layer deposition process of the film largely enhances the feasibility of practical production. • Significant PMA is achieved in a wide range of film thickness from 2 nm to 20 nm, which expands the usage form a GMR or TMR magnetic junctions to perpendicular spin polarizer for spin current related engineering. • The presented results may open new opportunities for advanced spintronic devices. - Abstract: Non-epitaxially induced perpendicular magnetic anisotropy (PMA) of Co{sub 50}Pt{sub 50} thin films at room temperature (RT) is reported. The CoPt film having a disordered hcp structure shows a magnetocrystalline anisotropy (K{sub u}{sup RT}) of 1–2 × 10{sup 6} erg/cm{sup 3} in a wide range of layer thickness from 2 to 20 nm. K{sub u}{sup RT} of about 1 × 10{sup 6} erg/cm{sup 3} can be preserved after a 400 °C-thermal cycle in the 5-nm-thick sample. Moderate PMA, large thickness range, simple preparation process, low formation temperature but good thermal stability make presented hcp CoPt become a remarkable option for advanced spintronic devices.

  19. Growth of Ca2MnO4 Ruddlesden-Popper structured thin films using combinatorial substrate epitaxy

    International Nuclear Information System (INIS)

    Lacotte, M.; David, A.; Pravarthana, D.; Prellier, W.; Grygiel, C.; Rohrer, G. S.; Salvador, P. A.; Velazquez, M.; Kloe, R. de

    2014-01-01

    The local epitaxial growth of pulsed laser deposited Ca 2 MnO 4 films on polycrystalline spark plasma sintered Sr 2 TiO 4 substrates was investigated to determine phase formation and preferred epitaxial orientation relationships (ORs) for isostructural Ruddlesden-Popper (RP) heteroepitaxy, further developing the high-throughput synthetic approach called Combinatorial Substrate Epitaxy (CSE). Both grazing incidence X-ray diffraction and electron backscatter diffraction patterns of the film and substrate were indexable as single-phase RP-structured compounds. The optimal growth temperature (between 650 °C and 800 °C) was found to be 750 °C using the maximum value of the average image quality of the backscattered diffraction patterns. Films grew in a grain-over-grain pattern such that each Ca 2 MnO 4 grain had a single OR with the Sr 2 TiO 4 grain on which it grew. Three primary ORs described 47 out of 49 grain pairs that covered nearly all of RP orientation space. The first OR, found for 20 of the 49, was the expected RP unit-cell over RP unit-cell OR, expressed as [100][001] film ||[100][001] sub . The other two ORs were essentially rotated from the first by 90°, with one (observed for 17 of 49 pairs) being rotated about the [100] and the other (observed for 10 of 49 pairs) being rotated about the [110] (and not exactly by 90°). These results indicate that only a small number of ORs are needed to describe isostructural RP heteroepitaxy and further demonstrate the potential of CSE in the design and growth of a wide range of complex functional oxides

  20. Controlled growth of epitaxial CeO2 thin films with self-organized nanostructure by chemical solution method

    DEFF Research Database (Denmark)

    Yue, Zhao; Grivel, Jean-Claude

    2013-01-01

    Chemical solution deposition is a versatile technique to grow oxide thin films with self-organized nanostructures. Morphology and crystallographic orientation control of CeO2 thin films grown on technical NiW substrates by a chemical solution deposition method are achieved in this work. Based...

  1. Orientation-dependent structural and photocatalytic properties of LaCoO3 epitaxial nano-thin films

    Science.gov (United States)

    Zhang, Yan-ping; Liu, Hai-feng; Hu, Hai-long; Xie, Rui-shi; Ma, Guo-hua; Huo, Ji-chuan; Wang, Hai-bin

    2018-02-01

    LaCoO3 epitaxial films were grown on (100), (110) and (111) oriented LaAlO3 substrates by the polymer-assisted deposition method. Crystal structure measurement and cross-section observation indicate that all the LaCoO3 films are epitaxially grown in accordance with the orientation of LaAlO3 substrates, with biaxial compressive strain in the ab plane. Owing to the different strain directions of CoO6 octahedron, the mean Co-O bond length increases by different amounts in (100), (110) and (111) oriented films compared with that of bulk LaCoO3, and the (100) oriented LaCoO3 has the largest increase. Photocatalytic degradation of methyl orange indicates that the order of photocatalytic activity of the three oriented films is (100) > (111) > (110). Combined with analysis of electronic nature and band structure for LaCoO3 films, it is found that the change of the photocatalytic activity is closely related to the crystal field splitting energy of Co3+ and Co-O binding energy. The increase in the mean Co-O bond length will decrease the crystal field splitting energy of Co3+ and Co-O binding energy and further reduce the value of band gap energy, thus improving the photocatalytic activity. This may also provide a clue for expanding the visible-light-induced photocatalytic application of LaCoO3.

  2. Accompanying growth and room-temperature ferromagnetism of η-Mn3N2 thin films by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yu, Fengmei; Liu, Yajing; Yang, Mei; Wu, Shuxiang; Zhou, Wenqi; Li, Shuwei

    2013-01-01

    η-phase manganese nitride films have been grown on LaAlO 3 (100) and LaSrAlO 4 (001) substrates by using plasma-assisted molecular beam epitaxy. On the basis of reflective high energy electron diffraction, X-ray diffraction, and X-ray photoemission spectroscopy, it is confirmed that two types of η-Mn 3 N 2 with different lattice constants coexist in the films due to the lattice mismatches between the Mn 3 N 2 films and the substrates. Magnetic properties of the films were characterized by a superconducting quantum interference device magnetometer at room temperature. The Mn 3 N 2 films on LaAlO 3 substrate were found to have room-temperature ferromagnetism. Two potential interaction mechanisms are proposed regarding the origin of the observed ferromagnetism. - Highlights: ► The films of two types of η-Mn 3 N 2 have been grown by molecular beam epitaxy. ► Mn 3 N 2 A and Mn 3 N 2 B coexisted in the films on LaAlO 3 and LaSrAlO 4 . ► The room-temperature ferromagnetism of the Mn 3 N 2 films on LaAlO 3 was obtained

  3. Mechanical responses of Zn{sub 1-x}Mn{sub x}O epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Teng-Ruey [Department of Industrial Engineering and Management, Nan Kai University of Techonology, Nantou 54243, Taiwan (China); Tsai, Chien-Huang, E-mail: chtsai12@gmail.com [Department of Automation Engineering, Nan Kai University of Techonology, Nantou 54243, Taiwan (China)

    2011-10-15

    In this study, we used nanoindentation to investigate the effect of the doping of Mn into ZnO buffer layers on the epitaxial growth of ZnO through plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. We characterized the variation of the mechanical properties of Zn{sub 1-x}Mn{sub x}O alloys as a function of the Mn content in the range (x) from 0 to 0.16, as well as analyzing their microstructures using high-resolution transmission electron microscopy. The presence of the Mn-doped ZnO buffer layer enhanced the nanomechanical properties of the ZnO epilayers significantly. From their Berkovich indenter responses, plots of the Young's modulus (E) and hardness (H) of these films revealed that the value of E increased relatively steadily upon increasing the Mn composition, whereas the value of H reached its maximum when x was equal to 0.16. This discrepancy suggests that Zn{sub 1-x}Mn{sub x}O epilayers of higher Mn contents had higher shear resistances.

  4. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jumpei; Oka, Daichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [University of Tsukuba Tandem Accelerator Complex (UTTAC), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-12-07

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO{sub x}N{sub y}) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO{sub x}N{sub y} thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO{sub x}N{sub y} thin films monotonically decreased from the order of 10{sup 5} Ω cm to 10{sup −4} Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO{sub x}N{sub y} phase, which has not yet been reported in Co{sup 2+}/Co{sup 3+} mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO{sub x}N{sub y} phase, on the 10{sup −3} Ω cm order, may have originated from the intermediate spin state of Co{sup 3+} stabilized by the lowered crystal field symmetry of the CoO{sub 6−n}N{sub n} octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO{sub x}N{sub y} films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides.

  5. Structural, Optical, and Electrical Characterization of β-Ga2O3 Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy Suitable for UV Sensing

    Directory of Open Access Journals (Sweden)

    Abraham Arias

    2018-01-01

    Full Text Available β-Ga2O3 thin films were grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The films were grown using an elemental gallium source and oxygen supplied by an RF plasma source. Reflection high-energy electron diffraction (RHEED was used to monitor the surface quality in real time. Both in situ RHEED and ex situ X-ray diffraction confirmed the formation of single crystal β-phase films with excellent crystallinity on c-plane sapphire. Spectroscopic ellipsometry was used to determine the film thicknesses, giving values in the 11.6–18.8 nm range and the refractive index dispersion curves. UV-Vis transmittance measurements revealed that strong absorption of β-Ga2O3 starts at ∼270 nm. Top metal contacts were deposited by thermal evaporation for I-V characterization, which has been carried out in dark, as well as under visible and UV light illumination. The optical and electrical measurements showed that the grown thin films of β-Ga2O3 are excellent candidates for deep-ultraviolet detection and sensing.

  6. Strain induced ferromagnetism and large magnetoresistance of epitaxial La1.5Sr0.5CoMnO6 thin films

    Science.gov (United States)

    Krishna Murthy, J.; Jyotsna, G.; N, Nileena; Anil Kumar, P. S.

    2017-08-01

    In this study, the structural, magnetic, and magneto-transport properties of La1.5Sr0.5CoMnO6 (LSCMO) thin films deposited on a SrTiO3 (001) substrate were investigated. A normal θ/2θ x-ray diffraction, rocking curve, ϕ-scan, and reciprocal space mapping data showed that prepared LSCMO thin films are single phase and highly strained with epitaxial nature. Temperature vs. magnetization of LSCMO films exhibits strain-induced ferromagnetic ordering with TC ˜ 165 K. In contrast to the bulk samples, there was no exchange bias and canted type antiferromagnetic and spin glass behavior in films having thickness (t) ≤ 26 nm. Temperature dependent resistivity data were explained using Schnakenberg's model and the polaron hopping conduction process. The slope change in resistivity and magnetoresistance maximum (˜65%) around TC indicates the existence of a weak double exchange mechanism between the mixed valence states of transition metal ions. Suppression of spin dependent scattering with the magnetic field is attributed for the large negative magnetoresistance in LSCMO films.

  7. Epitaxial Pb(Mg1/3Nb2/3)O3 thin films synthesized by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Bai, G. R.; Streiffer, S. K.; Baumann, P. K.; Auciello, O.; Ghosh, K.; Stemmer, S.; Munkholm, A.; Thompson, Carol; Rao, R. A.; Eom, C. B.

    2000-01-01

    Metal-organic chemical vapor deposition was used to prepare Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) thin films on (001) SrTiO 3 and SrRuO 3 /SrTiO 3 substrates, using solid Mg β-diketonate as the Mg precursor. Parameters including the precursor ratio in the vapor phase, growth temperature, growth rate, and reaction pressure in the reactor chamber were varied in order to determine suitable growth conditions for producing phase-pure, epitaxial PMN films. A cube-on-cube orientation relationship between the thin film and the SrTiO 3 substrate was found, with a (001) rocking curve width of 0.1 degree sign , and in-plane rocking-curve width of 0.8 degree sign . The root-mean-square surface roughness of a 200-nm-thick film on SrTiO 3 was 2 to 3 nm as measured by scanning probe microscopy. The zero-bias dielectric constant and loss measured at room temperature and 10 kHz for a 200-nm-thick film on SrRuO 3 /SrTiO 3 were approximately 1100 and 2%, respectively. The remnant polarization for this film was 16 μC/cm 2 . (c) 2000 American Institute of Physics

  8. Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

    Science.gov (United States)

    Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

    2018-04-01

    Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

  9. Configuration and local elastic interaction of ferroelectric domains and misfit dislocation in PbTiO3/SrTiO3 epitaxial thin films

    Directory of Open Access Journals (Sweden)

    Takanori Kiguchi, Kenta Aoyagi, Yoshitaka Ehara, Hiroshi Funakubo, Tomoaki Yamada, Noritaka Usami and Toyohiko J Konno

    2011-01-01

    Full Text Available We have studied the strain field around the 90° domains and misfit dislocations in PbTiO3/SrTiO3 (001 epitaxial thin films, at the nanoscale, using the geometric phase analysis (GPA combined with high-resolution transmission electron microscopy (HRTEM and high-angle annular dark field––scanning transmission electron microscopy (HAADF-STEM. The films typically contain a combination of a/c-mixed domains and misfit dislocations. The PbTiO3 layer was composed from the two types of the a-domain (90° domain: a typical a/c-mixed domain configuration where a-domains are 20–30 nm wide and nano sized domains with a width of about 3 nm. In the latter case, the nano sized a-domain does not contact the film/substrate interface; it remains far from the interface and stems from the misfit dislocation. Strain maps obtained from the GPA of HRTEM images show the elastic interaction between the a-domain and the dislocations. The normal strain field and lattice rotation match each other between them. Strain maps reveal that the a-domain nucleation takes place at the misfit dislocation. The lattice rotation around the misfit dislocation triggers the nucleation of the a-domain; the normal strains around the misfit dislocation relax the residual strain in a-domain; then, the a-domain growth takes place, accompanying the introduction of the additional dislocation perpendicular to the misfit dislocation and the dissociation of the dislocations into two pairs of partial dislocations with an APB, which is the bottom boundary of the a-domain. The novel mechanism of the nucleation and growth of 90° domain in PbTiO3/SrTiO3 epitaxial system has been proposed based on above the results.

  10. Residual losses in epitaxial thin films of YBa2Cu3O7 from microwave to submillimeter wave frequencies

    International Nuclear Information System (INIS)

    Miller, D.; Richards, P.L.; Etemad, S.; Inam, A.; Venkatesan, T.; Dutta, B.; Wu, X.D.; Eom, C.B.; Geballe, T.H.; Newman, N.; Cole, B.F.

    1991-01-01

    We have measured the residual loss in five epitaxial a-b plane films of the high-T c superconductor YBa 2 Cu 3 O 7 . Microwave measurements near 10 GHz were made by resonance techniques at 4 K. Submillimeter measurements from ∼1.5 to 21 THz were made at 2 K by a direct absorption technique. We use a model of weakly coupled superconducting grains and a homogeneous two-fluid model to fit the data for each film below the well-known absorption edge at 13.5 THz. When the penetration depth determined from muon spin rotation measurements is used to constrain each model, the weakly coupled grain model is able to fit the measured absorptivities for all films, but the two-fluid model is less successful

  11. High resolution x-ray scattering studies of strain in epitaxial thin films of yttrium silicide grown on silicon (111)

    International Nuclear Information System (INIS)

    Marthinez-Miranda, L.J.; Santiago-Aviles, J.J.; Siegal, M.P.; Graham, W.R.; Heiney, P.A.

    1990-01-01

    The authors have used high resolution grazing incidence x-ray scattering (GIXS) to study the in- plane and out-of-plane structure of epitaxial YSi 2-x films grown on Si(111), with thicknesses ranging from 85 Angstrom to 510 Angstrom. Their results indicate that the films are strained, and that film strain increases as a function of thickness, with lattice parameters varying from a = 3.846 Angstrom/c = 4.142 Angstrom for the 85 Angstrom film to a = 3.877 Angstrom/c = 4.121 Angstrom for the 510 Angstrom film. The authors correlate these results with an increase in pinhole areal coverage as a function of thickness. In addition, the authors' measurements show no evidence for the existence of ordered silicon vacancies in the films

  12. Thickness dependence of optical properties of VO2 thin films epitaxially grown on sapphire (0 0 0 1)

    International Nuclear Information System (INIS)

    Xu Gang; Jin Ping; Tazawa, Masato; Yoshimura, Kazuki

    2005-01-01

    Vanadium dioxide (VO 2 ) films were epitaxially grown on α-Al 2 O 3 (0 0 0 1) by rf reactive magnetron sputtering. The effects of film thickness ranging from 3 to 150 nm on optical properties were investigated. It revealed that the semiconductor--metal phase transition temperature considerably decreases as film thickness decreases, in particular for the film with thickness less than 10 nm. On the other hand, we found that the difference in visible transmittance between the two phases of VO 2 also varies with film thickness. For the films with thickness less than 50 nm, the semiconductor phase exhibits lower visible transmittance than its metallic phase, while for those with thickness larger than 50 nm the situation is reversed

  13. Structural and magnetic characterization of mixed valence Co(II, III)xZn1−xO epitaxial thin films

    International Nuclear Information System (INIS)

    Negi, D.S.; Loukya, B.; Dileep, K.; Sahu, R.; Shetty, S.; Kumar, N.; Ghatak, J.; Pachauri, N.; Gupta, A.; Datta, R.

    2014-01-01

    In this article, we report on the Co atom incorporation, secondary phase formation and composition-dependent magnetic and optical properties of mixed valence Co(II, III) x Zn 1−x O epitaxial thin films grown by pulsed laser deposition. The intended total Co concentration is varied between ∼6–60 at.% with relatively higher concentration of +3 over +2 charge state. Mixed valence Co(II, III) shows high solubility in ZnO (up to 38 at.%) and ferromagnetism is observed in samples with total Co incorporation of ∼29 and 38 at.%. Electron diffraction pattern and high resolution transmission electron microscopy images reveal single crystalline nature of the thin films with wurtzite structure. Co oxide interlayer, with both rock salt and spinel structure, are observed to be formed between the substrate and wurtzite film for total Co concentration at ∼17 at.% and above. Magnetization shows composition dependence with a saturation moment value of ∼93 emu cm −3 and a coercive field of ∼285 Oe observed for ∼38 at.% Co:ZnO films. Ferromagnetism was not observed for films with Co concentration 17 and 9 at.%. The Co oxide interlayer does not show any ferromagnetism. All the films are n-type with carrier concentration ∼10 19 cm −3 . The observed magnetism is probably resulting from direct antiferromagntic exchange interaction between Co 2+ and Co 3+ ions favored by heavy Co alloying giving rise to ferrimagnetism in the system. - Highlights: • Mixed valence Co doped ZnO ferromagnetic single crystal thin film. • Secondary phase formation in terms of CoO and Co3O4 and magnetism is observed only for high Co alloying. • Cathodoluminescence (CL) data showing increase in band gap with Co concentrations

  14. Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

    Directory of Open Access Journals (Sweden)

    Yuanzhou Gu

    2014-04-01

    Full Text Available We study the magnetic properties of Ho thin films with different crystallinity (either epitaxial or non-epitaxial and investigate their proximity effects with Nb thin films. Magnetic measurements show that epitaxial Ho has large anisotropy in two different crystal directions in contrast to non-epitaxial Ho. Transport measurements show that the superconducting transition temperature (Tc of Nb thin films can be significantly suppressed at zero field by epitaxial Ho compared with non-epitaxial Ho. We also demonstrate a direct control over Tc by changing the magnetic states of the epitaxial Ho layer, and attribute the strong proximity effects to exchange interaction.

  15. Selfsupported epitaxial silicon films

    International Nuclear Information System (INIS)

    Lazarovici, D.; Popescu, A.

    1975-01-01

    The methods of removing the p or p + support of an n-type epitaxial silicon layer using electrochemical etching are described. So far, only n + -n junctions have been processed. The condition of anodic dissolution for some values of the support and layer resistivity are given. By this method very thin single crystal selfsupported targets of convenient areas can be obtained for channeling - blocking experiments

  16. Low-temperature liquid phase epitaxy of rare-earth-ion doped KY(WO4)2 thin layers

    NARCIS (Netherlands)

    Romanyuk, Y.E.; Utke, I.; Ehrentraut, D.; Pollnau, Markus; Garcia-Revilla, S.; Valiente, R.; Kuleshov, N.V.

    2004-01-01

    Rare-earth-ion doped KY(WO4)2 (hereafter KYW) is a promising material for novel solid-state lasers. Low laser threshold, high efficiency, high output powers, and third-order nonlinear effects have stimulated research towards miniaturized thin-film waveguide lasers and amplifiers for future photonic

  17. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

  18. Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

    Science.gov (United States)

    Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

    2018-02-01

    A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

  19. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011)B3 single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Higuchi, Jumpei; Yabuhara, Osamu; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011) B3 single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar] bcc || GaAs(011)[011-bar] B3 . The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{011} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011) B3 substrates.

  20. Microstructure and Magnetic Properties of Fe and Fe-alloy Thin Films Epitaxially Grown on MgO(100) Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Matsubara, Katsuki; Ohtake, Mitsuru; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: matsubara@futamoto.elect.chuo-u.ac.jp [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2011-07-06

    Fe, Fe{sub 50}Co{sub 50}, and Fe{sub 80}Ni{sub 20} (at. %) single-crystal films with the (100){sub bcc} plane parallel to the substrate surface were prepared on MgO(100) single-crystals heated at 300 {sup 0}C by ultra high vacuum molecular beam epitaxy. The film growth mechanism, the film structure, and the magnetic properties were investigated. In-situ reflection high energy electron diffraction and X-ray diffraction analyses indicate that the strains in the films are very small though there are fairly large mismatches of -3.7{approx}-4.3% at the film/substrate interface. Cross-sectional high-resolution transmission electron microscopy shows that misfit dislocations are introduced in the film at the interface. Dislocations are also observed in the film up to around 10{approx}20 nm distance from the interface. The presence of such dislocation relieves the strain caused by the lattice mismatch. The in-plane magnetization properties of these films reflect the magnetocrystalline anisotropies of respective bulk Fe, Fe{sub 50}Co{sub 50}, and Fe{sub 80}Ni{sub 20} crystals.

  1. Microstructure and Magnetic Properties of Fe and Fe-alloy Thin Films Epitaxially Grown on MgO(100) Substrates

    International Nuclear Information System (INIS)

    Matsubara, Katsuki; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2011-01-01

    Fe, Fe 50 Co 50 , and Fe 80 Ni 20 (at. %) single-crystal films with the (100) bcc plane parallel to the substrate surface were prepared on MgO(100) single-crystals heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The film growth mechanism, the film structure, and the magnetic properties were investigated. In-situ reflection high energy electron diffraction and X-ray diffraction analyses indicate that the strains in the films are very small though there are fairly large mismatches of -3.7∼-4.3% at the film/substrate interface. Cross-sectional high-resolution transmission electron microscopy shows that misfit dislocations are introduced in the film at the interface. Dislocations are also observed in the film up to around 10∼20 nm distance from the interface. The presence of such dislocation relieves the strain caused by the lattice mismatch. The in-plane magnetization properties of these films reflect the magnetocrystalline anisotropies of respective bulk Fe, Fe 50 Co 50 , and Fe 80 Ni 20 crystals.

  2. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO{sub 2}-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Kiliha [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Shimizu, Takao [Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Sakata, Osami [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Shiraishi, Takahisa; Nakamura, Shogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Uchida, Hiroshi [Department of Materials and Life Sciences, Sophia University, Chiyoda, Tokyo 102-8554 (Japan); Funakubo, Hiroshi, E-mail: funakubo.h.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2016-04-07

    Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO{sub 1.5}-0.93HfO{sub 2} films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)- and (001)/(010)-oriented films on ITO and YSZ, respectively. Ferroelastic domain formation was confirmed for both films by X-ray diffraction using the superlattice diffraction that appeared only for the orthorhombic symmetry. The formation of ferroelastic domains is believed to be induced by the tetragonal–orthorhombic phase transition upon cooling the films after deposition. The present results demonstrate that the orientation of HfO{sub 2}-based ferroelectric films can be controlled in the same manner as that of ferroelectric films composed of conventional perovskite-type material such as Pb(Zr, Ti)O{sub 3} and BiFeO{sub 3}.

  3. Structural and magnetic anisotropy in the epitaxial FeV2O4 (110) spinel thin films

    Science.gov (United States)

    Shi, Xiaolan; Wang, Yuhang; Zhao, Kehan; Liu, Na; Sun, Gaofeng; Zhang, Liuwan

    2015-11-01

    The epitaxial 200-nm-thick FeV2O4(110) films on (110)-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

  4. Electrical properties from photoinduced charging on Cd-doped (100) surfaces of CuInSe{sub 2} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Nicole, E-mail: nejhnsn2@illinois.edu; Rockett, Angus [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, Illinois 61801 (United States); Aydogan, Pinar; Suzer, Sefik [Department of Chemistry, Bilkent University, 06800 Ankara (Turkey)

    2016-05-15

    The photoresponse of Cd-doped CuInSe{sub 2} (CIS) epitaxial thin films on GaAs(100) was studied using x-ray photoelectron spectroscopy under illumination from a 532 nm laser between sample temperatures of 28–260 °C. The initial, air-exposed surface shows little to no photoresponse in the photoelectron binding energies, the Auger electron kinetic energies or peak shapes. Heating between 50 and 130 °C in the analysis chamber results in enhanced n-type doping at the surface and an increased light-induced binding energy shift, the magnitude of which persists when the samples are cooled to room temperature from 130 °C but which disappears when cooling from 260 °C. Extra negative charge trapped on the Cu and Se atoms indicates deep trap states that dissociate after cooling from 260 °C. Analysis of the Cd modified Auger parameter under illumination gives experimental verification of electron charging on Cd atoms thought to be shallow donors in CIS. The electron charging under illumination disappears at 130 °C but occurs again when the sample is cooled to room temperature.

  5. Atomically layer-by-layer diffusion of oxygen/hydrogen in highly epitaxial PrBaCo{sub 2}O{sub 5.5+δ} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Shanyong; Xu, Xing; Enriquez, Erik; Mace, Brennan E.; Chen, Garry; Kelliher, Sean P.; Chen, Chonglin, E-mail: cl.chen@utsa.edu [Department of Physics and Astronomy, University of Texas, San Antonio, Texas 78249 (United States); Zhang, Yamei [Department of Physics, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003 (China); Whangbo, Myung-Hwan [North Carolina State University, Raleigh, North Carolina 27695-8204 (United States); Dong, Chuang; Zhang, Qinyu [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China)

    2015-12-14

    Single-crystalline epitaxial thin films of PrBaCo{sub 2}O{sub 5.5+δ} (PrBCO) were prepared, and their resistance R(t) under a switching flow of oxidizing and reducing gases were measured as a function of the gas flow time t in the temperature range of 200–800 °C. During the oxidation cycle under O{sub 2}, the PrBCO films exhibit fast oscillations in their dR(t)/dt vs. t plots, which reflect the oxidation processes, Co{sup 2+}/Co{sup 3+} → Co{sup 3+} and Co{sup 3+} → Co{sup 3+}/Co{sup 4+}, that the Co atoms of PrBCO undergo. Each oscillation consists of two peaks, with larger and smaller peaks representing the oxygen/hydrogen diffusion through the (BaO)(CoO{sub 2})(PrO)(CoO{sub 2}) layers of PrBCO via the oxygen-vacancy-exchange mechanism. This finding paves a significant avenue for cathode materials operating in low-temperature solid-oxide-fuel-cell devices and for chemical sensors with wide range of operating temperature.

  6. Structural features of epitaxial NiFe2O4 thin films grown on different substrates by direct liquid injection chemical vapor deposition

    Science.gov (United States)

    Datta, R.; Loukya, B.; Li, N.; Gupta, A.

    2012-04-01

    NiFe2O4 (NFO) thin films are grown on four different substrates, i.e., Lead Zinc Niobate-Lead Titanate (PZN-PT), Lead Magnesium Niobate-Lead Titanate (PMN-PT), MgAl2O4 (MAO) and SrTiO3 (STO), by a direct liquid injection chemical vapor deposition technique (DLI-CVD) under optimum growth conditions where relatively high growth rate (˜20 nm/min), smooth surface morphology and high saturation magnetization values in the range of 260-290 emu/ cm3 are obtained. The NFO films with correct stoichiometry (Ni:Fe=1:2) grow epitaxially on all four substrates, as confirmed by energy dispersive X-ray spectroscopy, transmission electron microscopy and x-ray diffraction. While the films on PMN-PT and PZN-PT substrates are partially strained, essentially complete strain relaxation occurs for films grown on MAO and STO. The formations of threading dislocations along with dark diffused contrast areas related to antiphase domains having a different cation ordering are observed on all four substrates. These crystal defects are correlated with lattice mismatch between the film and substrate and result in changes in magnetic properties of the films. Atomic resolution HAADF imaging and EDX line profiles show formation of a sharp interface between the film and the substrate with no inter-diffusion of Pb or other elements across the interface. Antiphase domains are observed to originate at the film-substrate interface.

  7. Correlations between the Hall coefficient and the superconducting transport properties of oxygen-deficient YBa2Cu3O7-δ epitaxial thin films

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Feenstra, R.; Zhu, S.; Lowndes, D.H.; Phillips, J.M.; Siegal, M.P.; Budai, J.D.

    1993-01-01

    Strong correlations between the Hall coefficient R H , the transition temperature T c , and the critical current density J c were established in a series of epitaxial YBa 2 Cu 3 O 7-δ thin films as a function of oxygen deficiency δ. Steady increases in R H with δ suggest that deoxygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T c . In contrast, two well-known plateaus occurring at 90 K and 60 K were observed in T c vs δ. Others have ascribed these plateaus to either electronic phenomena or phase separations. We find that in the 90-K plateau, the critical current density J c (δ,H=0) decreases with δ and extrapolates toward zero at the edge of the plateau, while the relative-field dependence of J c (δ,H) and the flux-creep pinning energies are independent of δ. These observations suggest that the phase-separation scenario occurs on the 90-K plateau. However, electronic origins cannot be ruled out at present due to difficulties in determining the equilibrium superconducting properties of oxygen-deficient YBa 2 Cu 3 O 7-δ films

  8. Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film.

    Science.gov (United States)

    Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2016-06-07

    Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.

  9. Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

    KAUST Repository

    Sarath Kumar, S. R.; Abutaha, Anas I.; Hedhili, Mohamed N.; Alshareef, Husam N.

    2012-01-01

    A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectricproperties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

  10. Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2012-12-03

    A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectricproperties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

  11. Investigation of electronic states of infinite-layer SrFeO2 epitaxial thin films by X-ray photoemission and absorption spectroscopies

    International Nuclear Information System (INIS)

    Chikamatsu, Akira; Matsuyama, Toshiya; Hirose, Yasushi; Kumigashira, Hiroshi; Oshima, Masaharu; Hasegawa, Tetsuya

    2012-01-01

    Highlights: ► Electronic states of infinite-layer SrFeO 2 films have been experimentally observed. ► Fe 3d states have higher densities of states in the valence-band region. ► Three peaks derived from Fe 3d states were observed in the conduction-band region. ► Indirect bandgap value was determined to be 1.3 eV. - Abstract: We investigated the electronic states of a single-crystal SrFeO 2 epitaxial thin film in the valence-band and conduction-band regions using synchrotron-radiation X-ray photoemission and absorption spectroscopies. Fe 2p–3d resonant photoemission measurements revealed that the Fe 3d states have higher densities of states at binding energies of 3–5 eV and 5–8.5 eV in the valence-band region. The O K-edge X-ray absorption spectrum exhibited three peaks in the Fe 3d-derived conduction band hybridized with O 2p states; these can be assigned to Fe 3d xy , 3d xz + 3d yz , and 3d x 2 –y 2 . In addition, the indirect bandgap value of the SrFeO 2 film was determined to be 1.3 eV by transmission and absorption spectroscopies.

  12. Morphological and microstructural stability of N-polar InAlN thin films grown on free-standing GaN substrates by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Hardy, Matthew T.; Storm, David F.; Downey, Brian P.; Katzer, D. Scott; Meyer, David J.; McConkie, Thomas O.; Smith, David J.; Nepal, Neeraj

    2016-01-01

    The sensitivity of the surface morphology and microstructure of N-polar-oriented InAlN to variations in composition, temperature, and layer thickness for thin films grown by plasma-assisted molecular beam epitaxy (PAMBE) has been investigated. Lateral compositional inhomogeneity is present in N-rich InAlN films grown at low temperature, and phase segregation is exacerbated with increasing InN fraction. A smooth, step-flow surface morphology and elimination of compositional inhomogeneity can be achieved at a growth temperature 50 °C above the onset of In evaporation (650 °C). A GaN/AlN/GaN/200-nm InAlN heterostructure had a sheet charge density of 1.7 × 10 13  cm −2 and no degradation in mobility (1760 cm 2 /V s) relative to 15-nm-thick InAlN layers. Demonstration of thick-barrier high-electron-mobility transistors with good direct-current characteristics shows that device quality, thick InAlN layers can be successfully grown by PAMBE

  13. Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

    International Nuclear Information System (INIS)

    Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

    2002-01-01

    Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

  14. Morphological and microstructural stability of N-polar InAlN thin films grown on free-standing GaN substrates by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, Matthew T., E-mail: matthew.hardy.ctr@nrl.navy.mil; Storm, David F.; Downey, Brian P.; Katzer, D. Scott; Meyer, David J. [Electronics Science and Technology Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington DC 20375 (United States); McConkie, Thomas O.; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Nepal, Neeraj [Sotera Defense Solutions, 2200 Defense Hwy Suite 405, Crofton, Maryland 21114 (United States)

    2016-03-15

    The sensitivity of the surface morphology and microstructure of N-polar-oriented InAlN to variations in composition, temperature, and layer thickness for thin films grown by plasma-assisted molecular beam epitaxy (PAMBE) has been investigated. Lateral compositional inhomogeneity is present in N-rich InAlN films grown at low temperature, and phase segregation is exacerbated with increasing InN fraction. A smooth, step-flow surface morphology and elimination of compositional inhomogeneity can be achieved at a growth temperature 50 °C above the onset of In evaporation (650 °C). A GaN/AlN/GaN/200-nm InAlN heterostructure had a sheet charge density of 1.7 × 10{sup 13 }cm{sup −2} and no degradation in mobility (1760 cm{sup 2}/V s) relative to 15-nm-thick InAlN layers. Demonstration of thick-barrier high-electron-mobility transistors with good direct-current characteristics shows that device quality, thick InAlN layers can be successfully grown by PAMBE.

  15. Field geometry dependence of magnetotransport in epitaxial La2/3Ca1/3MnO3 thin films

    International Nuclear Information System (INIS)

    Saldarriaga, W.; Baca, E.; Prieto, P.; Moran, O.; Grube, K.; Fuchs, D.; Schneider, R.

    2006-01-01

    In-plane and out-of-plane magnetoresistance measurements on epitaxial ∼200nm thin (001)-oriented films of high oxygen pressure DC-sputtering grown manganite La 2/3 Ca 1/3 MnO 3 were carried out. Single crystal (001)-SrTiO 3 substrates were used. The samples featured a Curie temperature T C ∼260K and a magnetic moment μ(T->0K)∼3μ B per Mn atom. Magnetocrystalline anisotropy with the easy axes lying on film plane was evidenced by recording the in-plane and out-of-plane magnetization loops at temperatures, below T C , in magnetic field strengths up to 5T. Evidence for anisotropic magnetotransport in these films was provided by electric measurements in a wide temperature range up to 6T magnetic field strengths applied both perpendicular and parallel to the film plane. In both applied magnetic field geometries, current and magnetic field were maintained perpendicular to each other. Neither low-field magnetoresistance nor large magnetoresistance hysteresis were observed on these samples, suggesting that the tensile strain imposed by the substrate in the first monolayers has partially been released. In addition, by rotating the sample 360 o around an axis parallel to film plane, in magnetic fields >=2T, a quadratic sinusoidal dependence of the magnetoresistance on the polar angle θ was observed. These results can be consistently interpreted using a generalized version of the theory of anisotropic magnetoresistance in transition-metal ferromagnets

  16. Structural properties of Bi{sub 2−x}Mn{sub x}Se{sub 3} thin films grown via molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Babakiray, Sercan; Johnson, Trent A.; Borisov, Pavel; Holcomb, Mikel B.; Lederman, David, E-mail: david.lederman@mail.wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Marcus, Matthew A. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Tarafder, Kartick [Department of Physics, BITS-Pilani Hyderabad Campus, Secunderabad, Andhra Pradesh 500078 (India)

    2015-07-28

    The effects of Mn doping on the structural properties of the topological insulator Bi{sub 2}Se{sub 3} in thin film form were studied in samples grown via molecular beam epitaxy. Extended x-ray absorption fine structure measurements, supported by density functional theory calculations, indicate that preferential incorporation occurs substitutionally in Bi sites across the entire film volume. This finding is consistent with x-ray diffraction measurements which show that the out of plane lattice constant expands while the in plane lattice constant contracts as the Mn concentration is increased. X-ray photoelectron spectroscopy indicates that the Mn valency is 2+ and that the Mn bonding is similar to that in MnSe. The expansion along the out of plane direction is most likely due to weakening of the Van der Waals interactions between adjacent Se planes. Transport measurements are consistent with this Mn{sup 2+} substitution of Bi sites if additional structural defects induced by this substitution are taken into account.

  17. Epitaxial growth and dielectric properties of Bi sub 2 VO sub 5 sub . sub 5 thin films on TiN/Si substrates with SrTiO sub 3 buffer layers

    CERN Document Server

    Lee, H Y; Choi, B C; Jeong, J H; Joseph, M; Tabata, H; Kawai, T

    2000-01-01

    Bi sub 2 VO sub 5 sub . sub 5 (BVO) thin films were epitaxially grown on SrTiO sub 3 /TiN/Si substrates by using pulsed laser ablation. A TiN thin film was prepared at 700 .deg. C as a bottom electrode. The TiN film exhibited a high alpha axis orientation and a very smooth morphology. Before the preparation of the BVO thin film, a crystallized SrTiO sub 3 thin film was deposited as a buffer layer on TiN/Si. The BVO thin film grown at a substrate temperature at 700 .deg. C and an oxygen pressure of 50 mTorr was found to be epitaxial along the c-axis. Also, BVO films were observed to have flat surfaces and the step-flow modes. The dielectric constant of the BVO film on STO/TiN/Si was constant at about 8 approx 4 in the applied frequency range between 10 sup 2 and 10 sup 6 Hz.

  18. Observation of long phase-coherence length in epitaxial La-doped CdO thin films

    Science.gov (United States)

    Yun, Yu; Ma, Yang; Tao, Songsheng; Xing, Wenyu; Chen, Yangyang; Su, Tang; Yuan, Wei; Wei, Jian; Lin, Xi; Niu, Qian; Xie, X. C.; Han, Wei

    2017-12-01

    The search for long electron phase-coherence length, which is the length that an electron can keep its quantum wavelike properties, has attracted considerable interest in the last several decades. Here, we report the long phase-coherence length of ˜3.7 μm in La-doped CdO thin films at 2 K. Systematical investigations of the La doping and the temperature dependences of the electron mobility and the electron phase-coherence length reveal contrasting scattering mechanisms for these two physical properties. Furthermore, these results show that the oxygen vacancies could be the dominant scatters in CdO thin films that break the electron phase coherence, which would shed light on further investigation of phase-coherence properties in oxide materials.

  19. High-resolution structural characterization and magnetic properties of epitaxial Ce-doped yttrium iron garnet thin films

    Science.gov (United States)

    Li, Zhong; Vikram Singh, Amit; Rastogi, Ankur; Gazquez, Jaume; Borisevich, Albina Y.; Mishra, Rohan; Gupta, Arunava

    2017-07-01

    Thin films of magnetic garnet materials, e.g. yttrium iron garnet (Y3Fe5O12, YIG), are useful for a variety of applications including microwave integrated circuits and spintronics. Substitution of rare earth ions, such as cerium, is known to enhance the magneto-optic Kerr effect (MOKE) as compared to pure YIG. Thin films of Ce0.75Y2.25Fe5O12 (Ce:YIG) have been grown using the pulsed laser deposition (PLD) technique and their crystal structure examined using high resolution scanning transmission electron microscopy. Homogeneous substitution of Ce in YIG, without oxidation to form a separate CeO2 phase, can be realized in a narrow process window with resulting enhancement of the MOKE signal. The thermally generated signal due to spin Seebeck effect for the optimally doped Ce:YIG films has also been investigated.

  20. Control of the magnetic properties of LaMnO3 epitaxial thin films grown by Pulsed Laser Deposition

    Science.gov (United States)

    Martinez, Benjamin; Roqueta, Jaume; Pomar, Alberto; Balcells, Lluis; Frontera, Carlos; Konstantinovic, Zorica; Sandiumenge, Felip; Santiso, Jose; Advanced materials characterization Team; Thin films growth Team

    2015-03-01

    LaMnO3 (LMO), the parent compound of colossal magnetoresistance based manganites has gained renewed attention as a building block in heterostructures with unexpected properties. In its bulk phase, stoichiometric LMO is an A-type antiferromagnetic (AFM) insulator (TN = 140K) with orthorhombic structure that easily accommodate an oxygen excess by generating cationic (La or Mn) vacancies. As a result, a fraction of Mn 3+ changes to Mn 4+ leading to a double-exchange mediated ferromagnetic (FM) behavior. In thin films the AFM phase has been elusive up to now and thin films with FM ordering are usually reported. In this work, we have systematically studied the growth process of LaMnO3 thin films by pulsed laser deposition on SrTiO3 (001) substrates under different oxygen partial pressures (PO2) . A close correlation between the structure (explored by XRD) and the magnetic properties (SQUID measurements) of the films with PO2 has been identified. At high PO2 FM behavior is observed. In contrast, at very low PO2, the results obtained for unit cell volume (close to stoichiometric bulk values) and magnetic moment (0.2 μB/Mn) strongly indicate antiferromagnetic ordering. We acknowledge financial support from the Spanish MINECO (MAT2012-33207).

  1. Spin injection from epitaxial Heusler alloy thin films into InGaAs/GaAs quantum wells

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad

    2006-01-01

    -stoichiometric crystals and crystals with site swapping defects. Significant decrease in the spin polarization has been predicted for disorder defects involving especially Co on Mn or Ga sites. From an estimate based on the calculated defect formation energies it is found that Mn on Co-sites are likely to exist...... no anisotropy is seen for near stoichiometry thin films on an ordinary GaAs surface. Typically thin films grown on GaAs show lower saturation magnetization than expected from bulk properties. The electrical characterizations have revealed resistivities around ρ = 350μΩcm at 300 K. Generally, the near...... to typically 0.02-0.1 Ωmm2 for Fe and Co contacts but two orders of magnitude higher for the Co2MnGa contacts. Point contact Andreev reflection measurements on an off-stoichiometric thin film (Co2.4Mn1.6Ga) show a spin polarization of P ≈ 50 %. Furthermore spin injection into a InGaAs/GaAs quantum well have...

  2. Strain-dependence of the structure and ferroic properties of epitaxial Ni1−xTi1−yO3 thin films grown on sapphire substrates

    International Nuclear Information System (INIS)

    Varga, Tamas; Droubay, Timothy C.; Bowden, Mark E.; Stephens, Sean A.; Manandhar, Sandeep; Shutthanandan, Vaithiyalingam; Colby, Robert J.; Hu, Dehong; Shelton, William A.; Chambers, Scott A.

    2015-01-01

    Polarization-induced weak ferromagnetism has been predicted a few years back in compounds MTiO 3 (M = Fe, Mn, Ni) (Fennie, 2008). We set out to stabilize this metastable, distorted perovskite structure by growing NiTiO 3 epitaxially on sapphire Al 2 O 3 (001) substrate, and to control the polar and magnetic properties via strain. Epitaxial Ni 1−x Ti 1−y O 3 films of different Ni/Ti ratios and thicknesses were deposited on Al 2 O 3 substrates by pulsed laser deposition at different temperatures, and characterized using several techniques. The effect of film thickness, deposition temperature, and film stoichiometry on lattice strain, film structure, and physical properties was investigated. Our structural data from x-ray diffraction, electron microscopy, and x-ray absorption spectroscopy shows that substrate-induced strain has a marked effect on the structure and crystalline quality of the films. Physical property measurements reveal a dependence of the Néel transition and lattice polarization on strain, and highlight our ability to control the ferroic properties in NiTiO 3 thin films by film stoichiometry and thickness. - Highlights: • NiTiO 3 epitaxial thin films with LiNbO 3 -type structure by pulsed laser deposition. • Strain varied by film thickness, stoichiometry, and synthesis temperature. • Systematic study of the effect of strain on film structure and physical properties. • Manipulation of ferroic properties by strain confirmed

  3. Fabrication of cerium-doped β-Ga2O3 epitaxial thin films and deep ultraviolet photodetectors.

    Science.gov (United States)

    Li, Wenhao; Zhao, Xiaolong; Zhi, Yusong; Zhang, Xuhui; Chen, Zhengwei; Chu, Xulong; Yang, Hujiang; Wu, Zhenping; Tang, Weihua

    2018-01-20

    High-quality cerium-doped β-Ga 2 O 3 (Ga 2 O 3 :Ce) thin films could be achieved on (0001)α-Al 2 O 3 substrates using a pulsed-laser deposition method. The impact of dopant contents concentration on crystal structure, optical absorption, photoluminescence, and photoelectric properties has been intensively studied. X-ray diffraction analysis results have shown that Ga 2 O 3 :Ce films are highly (2¯01) oriented, and the lattice spacing of the (4¯02) planes is sensitive to the Ce doping level. The prepared Ga 2 O 3 :Ce films show a sharp absorption edge at about 250 nm, meaning a high transparency to deep ultraviolet (DUV) light. The photoluminescence results revealed that the emissions were in the violet-blue-green region, which are associated with the donor-acceptor transitions with the Ce 3+ and oxygen vacancies related defects. A simple DUV photodetector device with a metal-semiconductor-metal structure has also been fabricated based on Ga 2 O 3 :Ce thin film. A distinct DUV photoresponse was obtained, suggesting a potential application in DUV photodetector devices.

  4. Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial Bi2FeCrO6 Multiferroic Thin Films.

    Science.gov (United States)

    Huang, Wei; Chakrabartty, Joyprokash; Harnagea, Catalin; Gedamu, Dawit; Ka, Ibrahima; Chaker, Mohamed; Rosei, Federico; Nechache, Riad

    2018-04-18

    Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes because of their favorable band gap (heterojunction was fabricated by pulsed laser deposition. The heterojunction photodiode exhibits a large ideality factor ( n = ∼5.0) and a response time as fast as 68 ms, thanks to the effective charge carrier transport and collection at the BFCO/SRO interface. The diode can switch direction when the electric polarization is reversed by an external voltage pulse. The time-resolved photoluminescence decay of the device measured at ∼500 nm demonstrates an ultrafast charge transfer (lifetime = ∼6.4 ns) in BFCO/SRO heteroepitaxial structures. The estimated responsivity value at 500 nm and zero bias is 0.38 mA W -1 , which is so far the highest reported for any FE thin film photodiode. Our work highlights the huge potential for using multiferroic oxides to fabricate highly sensitive and switchable photodiodes.

  5. Ion channeling study of epitaxially grown HoBa2Cu3Ox thin films on MgO(001)

    International Nuclear Information System (INIS)

    Watamori, Michio; Shoji, Fumiya; Hanawa, Teruo; Oura, Kenjiro; Itozaki, Hideo.

    1990-01-01

    The crystalline quality of high-T c superconducting HoBa 2 Cu 3 O x thin films formed on MgO(001) has been investigated by a high-energy ion channeling technique. Analysis was performed at 3 depth regions (surface, inside, and interface), and the degree of crystalline quality at each depth was estimated. Based on ion channeling measurements carried out with the normal and off-normal and directions, it has been found that (1) the crystalline quality at the film surface is much better than that at the interface, (2) the crystalline disorder can be seen mainly along the c-axis, and (3) the film consists of two domains, 90deg rotated from each other about the c-axis of the film. The crystalline quality of the MgO substrates has also been investigated. (author)

  6. Intrinsic conduction through topological surface states of insulating Bi{sub 2}Te{sub 3} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hoefer, Katharina; Becker, Christoph; Rata, Diana; Thalmeier, Peter; Tjeng, Liu Hao [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Swanson, Jesse [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); University of British Columbia, Vancouver (Canada)

    2015-07-01

    Topological insulators represent a new state of matter that open up new opportunities to create unique quantum particles. Many exciting experiments have been proposed by theory, yet, the main obstacle for their execution is material quality and cleanliness of the experimental conditions. The presence of tiny amounts of defects in the bulk or contaminants at the surface already mask these phenomena. We present the preparation, structural and spectroscopic characterisation of MBE-grown Bi{sub 2}Te{sub 3} thin films that are insulating in the bulk. Moreover, temperature dependent four-point-probe resistivity measurements of the Dirac states on surfaces that are intrinsically clean were conducted. The total amount of surface charge carries is in the order of 10{sup 12} cm{sup -2} and mobilities up to 4600 cm{sup 2}/Vs are observed. Importantly, these results are achieved by carrying out the preparation and characterisation all in-situ under ultra-high-vacuum conditions.

  7. Effect of microstructure on the electronic transport properties of epitaxial CaRuO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Daptary, Gopi Nath; Sow, Chanchal; Sarkar, Suman; Chiniwar, Santosh; Kumar, P.S. Anil [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Sil, Anomitra [Center For Nano Science And Engineering, Indian Institute of Science, Bangalore 560012 (India); Bid, Aveek, E-mail: aveek.bid@physics.iisc.ernet.in [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2017-04-15

    We have carried out extensive comparative studies of the structural and transport properties of CaRuO{sub 3} thin films grown under various oxygen pressure. We find that the preferred orientation and surface roughness of the films are strongly affected by the oxygen partial pressure during growth. This in turn affects the electrical and magnetic properties of the films. Films grown under high oxygen pressure have the least surface roughness and show transport characteristics of a good metal down to the lowest temperature measured. On the other hand, films grown under low oxygen pressures have high degree of surface roughness and show signatures of ferromagnetism. We could verify that the low frequency resistance fluctuations (noise) in these films arise due to thermally activated fluctuations of local defects and that the defect density matches with the level of disorder seen in the films through structural characterizations.

  8. Structural and magnetic properties of epitaxial delafossite CuFeO{sub 2} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Toyanath; Senty, Tess R.; Trappen, Robbyn; Zhou, Jinling; Borisov, Pavel; Holcomb, Mikel B.; Bristow, Alan D.; Lederman, David [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Chen, Song; Song, Xueyan [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6070 (United States); Ferrari, Piero; Cabrera, Alejandro L. [Pontificia Universidad Catolica, Instituto de Física, Santiago (Chile)

    2015-01-07

    Growth of pure phase delafossite CuFeO{sub 2} thin films on Al{sub 2}O{sub 3} (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO{sub 2} films demonstrated a phase transition at T{sub C} ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO{sub 2}. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.

  9. Investigation of electronic states of infinite-layer SrFeO{sub 2} epitaxial thin films by X-ray photoemission and absorption spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Matsuyama, Toshiya [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Hirose, Yasushi [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Kumigashira, Hiroshi; Oshima, Masaharu [Department of Applied Chemistry, University of Tokyo, Tokyo 113-8656 (Japan); Hasegawa, Tetsuya [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Electronic states of infinite-layer SrFeO{sub 2} films have been experimentally observed. Black-Right-Pointing-Pointer Fe 3d states have higher densities of states in the valence-band region. Black-Right-Pointing-Pointer Three peaks derived from Fe 3d states were observed in the conduction-band region. Black-Right-Pointing-Pointer Indirect bandgap value was determined to be 1.3 eV. - Abstract: We investigated the electronic states of a single-crystal SrFeO{sub 2} epitaxial thin film in the valence-band and conduction-band regions using synchrotron-radiation X-ray photoemission and absorption spectroscopies. Fe 2p-3d resonant photoemission measurements revealed that the Fe 3d states have higher densities of states at binding energies of 3-5 eV and 5-8.5 eV in the valence-band region. The O K-edge X-ray absorption spectrum exhibited three peaks in the Fe 3d-derived conduction band hybridized with O 2p states; these can be assigned to Fe 3d{sub xy}, 3d{sub xz} + 3d{sub yz}, and 3d{sub x}{sup 2}{sub -y}{sup 2}. In addition, the indirect bandgap value of the SrFeO{sub 2} film was determined to be 1.3 eV by transmission and absorption spectroscopies.

  10. Facile synthesis of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3−δ} (BSCF) perovskite nanowires by templating from nanoporous anodic aluminium oxide membranes

    Energy Technology Data Exchange (ETDEWEB)

    Habiballah, Anisah Shafiqah [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Jani, Abdul Mutalib Md, E-mail: abdmutalib@perlis.uitm.edu.my [Chemistry Department, Faculty of Applied Sciences, Universiti Teknologi MARA, 02600 Arau, Perlis (Malaysia); Mahmud, Abdul Hadi [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Osman, Nafisah [Physics Department, Faculty of Applied Sciences, Universiti Teknologi MARA, 02600 Arau, Perlis (Malaysia); Radiman, Shahidan [Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2016-07-01

    Template synthesis has been shown to be a popular and elegant route for fabricating a broad range of nanostructured materials such as nanowires, nanotubes or nanorods. These nanostructures can be used as building blocks in nanoscale electronic, magnetic and photonic devices. Nonetheless, there are still numerous challenges to control the intricate one-dimensional nanostructures with well-controlled size, phase purity, crystallinity and chemical composition. In this work, we synthesized Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3−δ} (BSCF) perovskite nanowires by templating approach for the first time; with varying the spin coating rate of 100, 500 and 1000 revolutions per minute (rpm), followed by drying (150 °C, 15 h) and calcination treatment (400–900 °C, 4 h). We only focused on structural properties, morphology and formation mechanism of BSCF nanowires by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX) analysis. The XRD profile confirmed at a calcination temperature of 900 °C, a single crystalline phase of BSCF nanowires was successfully obtained, in which congruent to the perovskite cubic structure of BSCF. Particularly, FESEM micrograph showed that a highly dense morphological distribution of BSCF nanowires has been successfully attained at a low spinning rate of 100 rpm, with the length range of 7–10 μm. The TEM image further confirmed the nanowires structure of BSCF. Besides, EDX analysis confirmed the stoichiometry percentages of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3−δ}. The possible formation mechanism of the BSCF nanowires was also discussed in this paper. - Highlights: • BSCF nanowires were synthesized via template synthesis with spin coating technique. • Single crystalline phase of BSCF nanowires was successfully obtained at 900 °C. • Different spin rate will result in different BSCF

  11. Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire; Wu, Xiaosong; First, Phillip N.; Conrad, Edward H.; Li, Xuebin; Li, Tianbo; Sprinkle, Michael; Hass, Joanna; Sadowski, Marcin L.; Potemski, Marek; Martinez, Gérard

    2007-07-01

    Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties that may persist above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high-mobility epitaxial graphene. It appears that the effect is suppressed due to the absence of localized states in the bulk of the material. Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temperature ballistic devices may be feasible for low-dissipation high-speed nanoelectronics.

  12. Influence of the bismuth deficit on the structural and electric properties of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} thin films synthesized by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Alami, H.El.; Rannou, I.; Deville Cavellin, C

    2004-07-15

    BiSrCaCuO thin films were grown on (1 0 0) SrTiO3 substrates by molecular beam epitaxy (MBE) with variation of the Bi deposition time. A new 2x212 family with x varied between 1 and 0 was grown. The X-ray study, the Rutherford back scattering (RBS), reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM) were used to characterize the films. It was shown that the growth method used leads to intergrowth nanostructures. The transport measurements of BiSrCaCuO thin films were performed. The results analysed using the theory of percolation show a 2D character of conductivity in the films studied.

  13. High-quality AlGaN/GaN grown on sapphire by gas-source molecular beam epitaxy using a thin low-temperature AlN layer

    Energy Technology Data Exchange (ETDEWEB)

    Jurkovic, M.J.; Li, L.K.; Turk, B.; Wang, W.I.; Syed, S.; Simonian, D.; Stormer, H.L.

    2000-07-01

    Growth of high-quality AlGaN/GaN heterostructures on sapphire by ammonia gas-source molecular beam epitaxy is reported. Incorporation of a thin AlN layer grown at low temperature within the GaN buffer is shown to result in enhanced electrical and structural characteristics for subsequently grown heterostructures. AlGaN/GaN structures exhibiting reduced background doping and enhanced Hall mobilities (2100, 10310 and 12200 cm{sup 2}/Vs with carrier sheet densities of 6.1 x 10{sup 12} cm{sup {minus}2}, and 5.8 x 10{sup 12} cm{sup {minus}2} at 300 K, 77 K, and 0.3 K, respectively) correlate with dislocation filtering in the thin AlN layer. Magnetotransport measurements at 0.3 K reveal well-resolved Shubnikov-de Haas oscillations starting at 3 T.

  14. Effects of strain on the magnetic and transport properties of the epitaxial La{sub 0.5}Ca{sub 0.5}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zarifi, M. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kameli, P., E-mail: kameli@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Ehsani, M.H. [Department of Physics, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Ahmadvand, H.; Salamati, H. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2016-12-15

    The epitaxial strain can considerably modify the physical properties of thin films compared to the bulk. This paper reports the effects of substrate-induced strain on La{sub 0.5}Ca{sub 0.5}MnO{sub 3} (LCMO) thin films, grown on (100) SrTiO{sub 3} (STO) and LaAlO{sub 3} (LAO) substrates by pulsed laser deposition technique. Transport and magnetic properties were found to be strongly dependent on strain type. It is also shown that compressive (tensile) strain leads to the increase (decrease) in the magnetization of the films. Moreover, it was observed that all LCMO films deposited on both LAO and STO substrates behave as an insulator, but LCMO/LAO thin films with compressive strain have lower resistivity than LCMO/STO thin films with tensile strain. Applying magnetic field to LCMO/STO thin films with thickness of 25 and 50 nm leads to very small change in the resistivity, while the effects of magnetic field on the sample with thickness of 125 nm leads to an insulator–metal transition. For LCMO/LAO thin films, the magnetic field has a strong impact on the resistivity of samples. The results show that the magnetoresistance (MR) is enhanced by increasing film thickness for LCMO/LAO samples, due to the relatively stronger phase separation. For LCMO/STO thin films MR is drastically decreased by reduction of film thickness, which is attributed to the enhancement of the charge–orbital order (CO–O) accompanying the complex spin order (the so-called CE type). The changes of the antiferromagnetic structure from the CE to C type and the enhancement of the CE type could be attributed to the in-plane compressive and tensile strain, respectively. - Highlights: • Epitaxial La{sub 0.5}Ca{sub 0.5}MnO{sub 3} thin films, grown on (100) SrTiO{sub 3} and LaAlO{sub 3} substrates. • The compressive strain leads to the increase in the magnetization of the films. • The tensile strain leads to the decrease in the magnetization of the films. • The magnetoresistance is enhanced by

  15. Spin wave and percolation studies in epitaxial La{sub 2/3}Sr{sub 1/3}MnO{sub 3} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ettayfi, A. [LPMMAT, Faculté des Sciences Ain chock, Université Hassan II de Casablanca, B.P. 5366 Casablanca (Morocco); Moubah, R., E-mail: reda.moubah@hotmail.fr [LPMMAT, Faculté des Sciences Ain chock, Université Hassan II de Casablanca, B.P. 5366 Casablanca (Morocco); Hlil, E.K. [Institut Néel, CNRS, Université Joseph Fourier, BP 166, 38042 Grenoble Cedex 9 (France); Colis, S.; Lenertz, M.; Dinia, A. [Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504 UDS-CNRS (UDS-ECPM), 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2 (France); Lassri, H. [LPMMAT, Faculté des Sciences Ain chock, Université Hassan II de Casablanca, B.P. 5366 Casablanca (Morocco)

    2016-07-01

    We investigate the magnetic and transport properties of high quality La{sub 2/3}Sr{sub 1/3}MnO{sub 3} thin films grown by pulsed laser deposition. X-ray diffraction shows that the deposited films are epitaxial with the expected pseudo-cubic structure. Using the spin wave theory, the temperature dependence of magnetization was satisfactory modeled at low temperature, in which several fundamental magnetic parameters were obtained (spin wave stiffness, exchange constants, Fermi wave-vector, Mn–Mn interatomic distance). The transport properties were studied via the temperature dependence of electrical resistivity [ρ(T)], which shows a peak at Curie temperature due to metal to insulator transition. The percolation theory was used to simulate ρ(T) in both the ferromagnetic and paramagnetic phases. Reasonable agreement with the experimental data is reported. - Highlights: • The magnetic and transport properties of epitaxial La{sub 2/3}Sr{sub 1/3}MnO{sub 3} thin films are investigated. • The M(T) curve was modeled at low temperature, and several magnetic parameters were obtained using spin wave theory. • The percolation theory was used to simulate ρ(T) in both the ferromagnetic and paramagnetic phases.

  16. On the evolution of InAs thin films grown by molecular beam epitaxy on the GaAs(001) surface

    International Nuclear Information System (INIS)

    Grabowski, Jan

    2010-01-01

    Semiconductor nanostructures are currently of high interest for a wide variety of electronic and optoelectronic applications. A large number of devices, in particular for the optical data transmission in the long-wavelength range, essential in modern communication, are based on InAs/GaAs quantum dot (QD) structures. Though the properties of the InAs/GaAs QDs have been extensively studied, only little is known about the formation and structure of the wetting layer (WL) yet. In the present work, the pathway of the InAs WL evolution is studied in detail. For this purpose, InAs thin films in the range of one monolayer (ML) are deposited on the GaAs(001) surface by molecular beam epitaxy (MBE) and studied by reflection high energy electron diffraction (RHEED) and in particular by scanning tunneling microscopy (STM). The InAs thin films are grown in both typical growth regimes, on the GaAs-c(4 x 4) and the GaAs-β2(2 x 4) reconstructed surface, in a variety of thicknesses starting from submonolayers with 0.09 ML of InAs up to 1.65 ML of InAs exceeding the critical thickness for QD growth. In principle, three growth stages are found. At low InAs coverages, the indium adsorbs in agglomerations of typically eight In atoms at energetically preferable surface sites. In the STM images, the signatures of these In agglomerations appear with a clear bright contrast. A structural model for the initial formation of these signatures is presented, and its electronic and strain related properties are discussed. At an InAs coverage of about 0.67ML the initial surface transforms into a (4 x 3) reconstructed In 2/3 Ga 1/3 As ML and the detailed structure and strain properties of this surface are unraveled. On top of the InGaAs ML further deposited InAs forms a second layer, characterized by a typical zig-zag alignment of (2 x 4) reconstructed unit cells, with an alternating α2/α2-m configuration. In contrast to the previous surface reconstructions, where structural strain is

  17. On the evolution of InAs thin films grown by molecular beam epitaxy on the GaAs(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Grabowski, Jan

    2010-12-14

    Semiconductor nanostructures are currently of high interest for a wide variety of electronic and optoelectronic applications. A large number of devices, in particular for the optical data transmission in the long-wavelength range, essential in modern communication, are based on InAs/GaAs quantum dot (QD) structures. Though the properties of the InAs/GaAs QDs have been extensively studied, only little is known about the formation and structure of the wetting layer (WL) yet. In the present work, the pathway of the InAs WL evolution is studied in detail. For this purpose, InAs thin films in the range of one monolayer (ML) are deposited on the GaAs(001) surface by molecular beam epitaxy (MBE) and studied by reflection high energy electron diffraction (RHEED) and in particular by scanning tunneling microscopy (STM). The InAs thin films are grown in both typical growth regimes, on the GaAs-c(4 x 4) and the GaAs-{beta}2(2 x 4) reconstructed surface, in a variety of thicknesses starting from submonolayers with 0.09 ML of InAs up to 1.65 ML of InAs exceeding the critical thickness for QD growth. In principle, three growth stages are found. At low InAs coverages, the indium adsorbs in agglomerations of typically eight In atoms at energetically preferable surface sites. In the STM images, the signatures of these In agglomerations appear with a clear bright contrast. A structural model for the initial formation of these signatures is presented, and its electronic and strain related properties are discussed. At an InAs coverage of about 0.67ML the initial surface transforms into a (4 x 3) reconstructed In{sub 2/3}Ga{sub 1/3}As ML and the detailed structure and strain properties of this surface are unraveled. On top of the InGaAs ML further deposited InAs forms a second layer, characterized by a typical zig-zag alignment of (2 x 4) reconstructed unit cells, with an alternating {alpha}2/{alpha}2-m configuration. In contrast to the previous surface reconstructions, where

  18. Epitaxial growth of silicon for layer transfer

    Science.gov (United States)

    Teplin, Charles; Branz, Howard M

    2015-03-24

    Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

  19. Ferroelectric and piezoelectric responses of (110) and (001)-oriented epitaxial Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} thin films on all-oxide layers buffered silicon

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Hien Thu [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Nguyen, Minh Duc, E-mail: minh.nguyen@itims.edu.vn [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); SolMateS B.V., Drienerlolaan 5, Building 6, 7522 NB Enschede (Netherlands); Houwman, Evert; Boota, Muhammad [Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Dekkers, Matthijn [SolMateS B.V., Drienerlolaan 5, Building 6, 7522 NB Enschede (Netherlands); Vu, Hung Ngoc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Rijnders, Guus [Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2015-12-15

    Graphical abstract: The cross sections show a very dense structure in the (001)-oriented films (c,d), while an open columnar growth structure is observed in the case of the (110)-oriented films (a,b). The (110)-oriented PZT films show a significantly larger longitudinal piezoelectric coefficient (d33{sub ,f}), but smaller transverse piezoelectric coefficient (d31{sub ,f}) than the (001) oriented films. - Highlights: • We fabricate all-oxide, epitaxial piezoelectric PZT thin films on Si. • The orientation of the films can be controlled by changing the buffer layer stack. • The coherence of the in-plane orientation of the grains and grain boundaries affects the ferroelectric properties. • Good cycling stability of the ferroelectric properties of (001)-oriented PZT thin films. The (110)-oriented PZT thin films show a larger d33{sub ,f} but smaller d31{sub ,f} than the (001)-oriented films. - Abstract: Epitaxial ferroelectric Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) thin films were fabricated on silicon substrates using pulsed laser deposition. Depending on the buffer layers and perovskite oxide electrodes, epitaxial films with different orientations were grown. (110)-oriented PZT/SrRuO{sub 3} (and PZT/LaNiO{sub 3}) films were obtained on YSZ-buffered Si substrates, while (001)-oriented PZT/SrRuO{sub 3} (and PZT/LaNiO{sub 3}) were fabricated with an extra CeO{sub 2} buffer layer (CeO{sub 2}/YSZ/Si). There is no effect of the electrode material on the properties of the films. The initial remnant polarizations in the (001)-oriented films are higher than those of (110)-oriented films, but it increases to the value of the (001) films upon cycling. The longitudinal piezoelectric d33{sub ,f} coefficients of the (110) films are larger than those of the (001) films, whereas the transverse piezoelectric d31{sub ,f} coefficients in the (110)-films are less than those in the (001)-oriented films. The difference is ascribed to the lower density (connectivity between

  20. Nanosheet controlled epitaxial growth of PbZr0.52Ti0.48O3 thin films on glass substrates

    NARCIS (Netherlands)

    Bayraktar, Muharrem; Chopra, A.; Bijkerk, Frederik; Rijnders, Augustinus J.H.M.

    2014-01-01

    Integration of PbZr0.52Ti0.48O3 (PZT) films on glass substrates is of high importance for device applications. However, to make use of the superior ferro- and piezoelectric properties of PZT, well-oriented crystalline or epitaxial growth with control of the crystal orientation is a prerequisite. In

  1. The effects of strain relaxation on the dielectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)TiO3 thin films

    Science.gov (United States)

    Khan, Asif Islam; Yu, Pu; Trassin, Morgan; Lee, Michelle J.; You, Long; Salahuddin, Sayeef

    2014-07-01

    We study the effects of strain relaxation on the dielectric properties of epitaxial 40 nm Pb(Zr0.2Ti0.8)TiO3 (PZT) films. A significant increase in the defect and dislocation density due to strain relaxation is observed in PZT films with tetragonality c/a fatigue in ferroelectric materials.

  2. Enhanced hardness in epitaxial TiAlScN alloy thin films and rocksalt TiN/(Al,Sc)N superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Bivas [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Lawrence, Samantha K.; Bahr, David F. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Schroeder, Jeremy L.; Birch, Jens [Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Sands, Timothy D. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-10-13

    High hardness TiAlN alloys for wear-resistant coatings exhibit limited lifetimes at elevated temperatures due to a cubic-AlN to hexagonal-AlN phase transformation that leads to decreasing hardness. We enhance the hardness (up to 46 GPa) and maximum operating temperature (up to 1050 °C) of TiAlN-based coatings by alloying with scandium nitride to form both an epitaxial TiAlScN alloy film and epitaxial rocksalt TiN/(Al,Sc)N superlattices on MgO substrates. The superlattice hardness increases with decreasing period thickness, which is understood by the Orowan bowing mechanism of the confined layer slip model. These results make them worthy of additional research for industrial coating applications.

  3. Epitaxial single-crystal thin films of MnxTi1-xO2-δ grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Ilton, Eugene S.; Droubay, Timothy C.; Chaka, Anne M.; Kovarik, Libor; Varga, Tamas; Arey, Bruce W.; Kerisit, Sebastien N.

    2015-02-01

    Epitaxial rutile-structured single-crystal MnxTi1-xO2-δ films were synthesized on rutile- (110) and -(001) substrates using pulsed laser deposition. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and aberration-corrected transmission electron microscopy (ACTEM). Under the present conditions, 400oC and PO2 = 20 mTorr, single crystal epitaxial thin films were grown for x = 0.13, where x is the nominal average mole fraction of Mn. In fact, arbitrarily thick films could be grown with near invariant Mn/Ti concentration profiles from the substrate/film interface to the film surface. In contrast, at x = 0.25, Mn became enriched towards the surface and a secondary nano-scale phase formed which appeared to maintain the basic rutile structure but with enhanced z-contrast in the tunnels, or tetrahedral interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the β-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways.

  4. Intrinsic stability of ferroelectric and piezoelectric properties of epitaxial PbZr0.45Ti0.55O3 thin films on silicon in relation to grain tilt

    Directory of Open Access Journals (Sweden)

    Evert P Houwman, Minh D Nguyen, Matthijn Dekkers and Guus Rijnders

    2013-01-01

    Full Text Available Piezoelectric thin films of PbZr0.45Ti0.55O3 were grown on Si substrates in four different ways, resulting in different crystalline structures, as determined by x-ray analysis. The crystalline structures were different in the spread in tilt angle and the in-plane alignment of the crystal planes between different grains. It is found that the deviations of the ferroelectric polarization loop from that of the ideal rectangular loop (reduction of the remanent polarization with respect to the saturation polarization, dielectric constant of the film, slanting of the loop, coercive field value all scale with the average tilt angle. A model is derived based on the assumption that the tilted grain boundaries between grains affect the film properties locally. This model describes the observed trends. The effective piezoelectric coefficient d33,eff shows also a weak dependence on the average tilt angle for films grown in a single layer, whereas it is strongly reduced for the films deposited in multiple layers. The least affected properties are obtained for the most epitaxial films, i.e. grown on a SrTiO3 epitaxial seed layer, by pulsed laser deposition. These films are intrinsically stable and do not require poling to acquire these stable properties.

  5. Effects of swift heavy ion irradiation on La0.5Pr0.2Sr0.3MnO3 epitaxial thin films grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Markna, J.H.; Parmar, R.N.; Rana, D.S.; Ravi Kumar; Misra, P.; Kukreja, L.M.; Kuberkar, D.G.; Malik, S.K.

    2007-01-01

    We report the observation of room temperature insulator to metal transition and magnetoresistance characteristics of Swift Heavy Ions (SHIs) irradiated La 0.5 Pr 0.2 Sr 0.3 MnO 3 (LPSMO) epitaxial thin films grown on single crystal (1 0 0) SrTiO 3 substrates using Pulsed Laser Deposition. The epitaxial nature and crystallanity of the films was confirmed from the structural and magnetoresistance characteristics. Irradiation with the 200 MeV Ag 15+ ions at a fluence of about 5 x 10 11 ions/cm 2 showed suppression in the resistivity by ∼68% and 31% for the films with 50 nm and 100 nm thickness respectively. The possible reasons for this suppression could be either release of strain in the films in the dead layer at the interface of film-substrate or Swift Heavy Ions induced annealing which in turn affects the Mn-O-Mn bond angle thereby favoring the Zener double exchange. Field Coefficient of Resistance (FCR) values for both films, determined from R-H data and magnetoresistance data, showed a marginal enhancement after irradiation

  6. The liquid phase epitaxy approach for the successful construction of ultra-thin and defect-free ZIF-8 membranes: Pure and mixed gas transport study

    KAUST Repository

    Shekhah, Osama; Swaidan, Raja; Belmabkhout, Youssef; Du Plessis, Marike; Jacobs, Tia; Barbour, Leonard J.; Pinnau, Ingo; Eddaoudi, Mohamed

    2014-01-01

    The liquid-phase epitaxy (LPE) method was effectively implemented to deliberately grow/construct ultrathin (0.5-1 μm) continuous and defect-free ZIF-8 membranes. Permeation properties of different gas pair systems (O 2-N2, H2-CO2, CO2-CH 4, C3H6-C3H8, CH 4-n-C4H10) were studied using the time lag technique. This journal is © The Royal Society of Chemistry.

  7. Enhanced dielectric nonlinearity in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

    International Nuclear Information System (INIS)

    Ma, Chunrui; Wu, Judy; Ma, Beihai; Mi, Shao-Bo; Liu, Ming

    2014-01-01

    High quality c-axis oriented epitaxial Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films were fabricated using pulsed laser deposition on (001) LaAlO 3 substrates with conductive LaNiO 3 buffers. Besides confirmation of the in-plane and out-of-plane orientations using X-ray diffraction, transmission electron microscopy study has revealed columnar structure across the film thickness with column width around 100 nm. Characterization of ferroelectric properties was carried out in comparison with polycrystalline Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films to extract the effect of epitaxial growth. It is found that the ratio between the irreversible Rayleigh parameter and reversible parameter increased up to 0.028 cm/kV at 1 kHz on epitaxial samples, which is more than twice of that on their polycrystalline counterparts. While this ratio decreased to 0.022 cm/kV with increasing frequency to100 kHz, a much less frequency dependence was observed as compared to the polycrystalline case. The epitaxial Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films exhibited a higher mobility of domain wall and the higher extrinsic contribution to the dielectric properties, as well as reduced density of defects, indicating that it is promising for tunable and low power consumption devices

  8. Structure of epitaxial SrIrO.sub.3./sub. perovskite studied by interference between X-ray waves diffracted by the substrate and the thin film

    Czech Academy of Sciences Publication Activity Database

    Horák, L.; Kriegner, D.; Liu, J.; Frontera, C.; Martí, Xavier; Holý, V.

    2017-01-01

    Roč. 50, Apr (2017), s. 385-398 ISSN 1600-5767 R&D Projects: GA ČR GB14-37427G; GA MŠk(CZ) LG13058 Institutional support: RVO:68378271 Keywords : perovskites * epitaxial layers * X-ray diffraction * interference Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.495, year: 2016

  9. EDITORIAL: Epitaxial graphene Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire

    2012-04-01

    Graphene is widely regarded as an important new electronic material with interesting two-dimensional electron gas properties. Not only that, but graphene is widely considered to be an important new material for large-scale integrated electronic devices that may eventually even succeed silicon. In fact, there are countless publications that demonstrate the amazing applications potential of graphene. In order to realize graphene electronics, a platform is required that is compatible with large-scale electronics processing methods. It was clear from the outset that graphene grown epitaxially on silicon carbide substrates was exceptionally well suited as a platform for graphene-based electronics, not only because the graphene sheets are grown directly on electronics-grade silicon carbide (an important semiconductor in its own right), but also because these sheets are oriented with respect to the semiconductor. Moreover, the extremely high temperatures involved in production assure essentially defect-free and contamination-free materials with well-defined interfaces. Epitaxial graphene on silicon carbide is not a unique material, but actually a class of materials. It is a complex structure consisting of a reconstructed silicon carbide surface, which, for planar hexagonal silicon carbide, is either the silicon- or the carbon-terminated face, an interfacial carbon rich layer, followed by one or more graphene layers. Consequently, the structure of graphene films on silicon carbide turns out to be a rich surface-science puzzle that has been intensively studied and systematically unravelled with a wide variety of surface science probes. Moreover, the graphene films produced on the carbon-terminated face turn out to be rotationally stacked, resulting in unique and important structural and electronic properties. Finally, in contrast to essentially all other graphene production methods, epitaxial graphene can be grown on structured silicon carbide surfaces to produce graphene

  10. Anisotropic-strain-relaxation-induced crosshatch morphology in epitaxial SrTiO{sub 3}/NdGaO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tan, X. L.; Chen, F.; Chen, P. F.; Xu, H. R.; Chen, B. B.; Jin, F.; Gao, G. Y.; Wu, W. B., E-mail: wuwb@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, and High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230026 (China)

    2014-10-15

    We investigate the strain relaxation and surface morphology of epitaxial SrTiO{sub 3} (STO) films grown on (001){sub O} and (110){sub O} planes of orthorhombic NdGaO{sub 3} (NGO), and (001) plane of cubic (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT) substrates. Although the average lattice mismatches are similar, strikingly regular crosshatched surface patterns can be found on STO/NGO(001){sub O}[(110){sub O}] films, contrary to the uniform surface of STO/LSAT(001). Based on the orientation and thickness dependent patterns and high-resolution x-ray diffractions, we ascribe the crosshatch morphology to the anisotropic strain relaxation with possibly the 60° misfit dislocation formation and lateral surface step flow in STO/NGO films, while an isotropic strain relaxation in STO/LSAT. Further, we show that the crosshatched STO/NGO(110){sub O} surface could be utilized as a template to modify the magnetotransport properties of epitaxial La{sub 0.6}Ca{sub 0.4}MnO{sub 3} films. This study highlights the crucial role of symmetry mismatch in determining the surface morphology of the perovskite oxide films, in addition to their epitaxial strain states, and offers a different route for designing and fabricating functional perovskite-oxide devices.

  11. Direct formation of thin films and epitaxial overlayers at low temperatures using a low-energy (10-500 eV) ion beam deposition system

    International Nuclear Information System (INIS)

    Zuhr, R.A.; Alton, G.D.; Appleton, B.R.; Herbots, N.; Noggle, T.S.; Pennycook, S.J.

    1987-01-01

    A low-energy ion beam deposition system has been developed at Oak Ridge National Laboratory and has been applied successfully to the growth of epitaxial films at low temperatures for a number of different elements. The deposition system utilizes the ion source and optics of a commercial ion implantation accelerator. The 35 keV mass- and energy-analyzed ion beam from the accelerator is decelerated in a four-element electrostatic lens assembly to energies between 10 and 500 eV for direct deposition onto a target under UHV conditions. Current densities on the order of 10 μA/cm 2 are achieved with good uniformity over a 1.4 cm diameter spot. The completed films are characterized by Rutherford backscattering, ion channeling, cross-section transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning have been studied. Epitaxial overlayers which show good minimum yields by ion channeling (3 to 4%) have been produced at temperatures as low as 375 0 C for Si on Si(100) and 250 0 C for Ge on Ge(100) at growth rates that exceed the solid-phase epitaxy rates at these temperatures by more than an order of magnitude

  12. Growth and structural investigations of epitaxial hexagonal YMnO3 thin films deposited on wurtzite GaN(001) substrates

    International Nuclear Information System (INIS)

    Balasubramanian, K.R.; Chang, Kai-Chieh; Mohammad, Feroz A.; Porter, Lisa M.; Salvador, Paul A.; DiMaio, Jeffrey; Davis, Robert F.

    2006-01-01

    Epitaxial hexagonal YMnO 3 (h-YMnO 3 ) films having sharp (00l) X-ray diffraction peaks were grown above 700 deg. C in 5 mTorr O 2 via pulsed laser deposition both on as-received wurtzite GaN/AlN/6H-SiC(001) (w-GaN) substrates as well as on w-GaN surfaces that were etched in 50% HF solution. High-resolution transmission electron microscopy revealed an interfacial layer between film and the unetched substrate; this layer was absent in those samples wherein an etched substrate was used. However, the substrate treatment did not affect the epitaxial arrangement between the h-YMnO 3 film and w-GaN substrate. The epitaxial relationships of the h-YMnO 3 films with the w-GaN(001) substrate was determined via X-ray diffraction to be (001) YMnO 3 -parallel (001) GaN : [11-bar0] YMnO 3 -parallel [110] GaN ; in other words, the basal planes of the film and the substrate are aligned parallel to one another, as are the most densely packed directions in planes of the film and the substrate. Interestingly, this arrangement has a larger lattice mismatch than if the principal axes of the unit cells were aligned

  13. 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.

  14. Supercurrents in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gapud, A.A.; Wu, J.Z.; Fang, L.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    1999-06-01

    The availability of high-quality epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) and TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) with high critical current densities (J{sub c}) has made it possible to examine and compare the J{sub c} of these species. Results reveal that the J{sub c} of 1212 species have very similar temperature behavior at low fields, strongly suggesting that the 30 K shift in critical temperature (T{sub c}) induced by the exchange of Hg and Tl in the 1212 structure is due largely to a change in charge carrier density and/or electronic band structure. {copyright} {ital 1999 American Institute of Physics.}

  15. The bimodal distribution spin Seebeck effect enhancement in epitaxial Ni0.65Zn0.35Al0.8Fe1.2O4 thin film

    Science.gov (United States)

    Wang, Hua; Hou, Dazhi; Kikkawa, Takashi; Ramos, Rafael; Shen, Ka; Qiu, Zhiyong; Chen, Yao; Umeda, Maki; Shiomi, Yuki; Jin, Xiaofeng; Saitoh, Eiji

    2018-04-01

    The temperature dependence of the spin Seebeck effect (SSE) in epitaxial Ni0.65Zn0.35Al0.8Fe1.2O4 (NZA ferrite) thin film has been investigated systematically. The SSE at high fields shows a bimodal distribution enhancement from 3 K to 300 K and is well fitted with a double-peak Lorentzian function. We speculate the symmetric SSE enhancement in Pt/NZA ferrite bilayer, which is different from the magnon polarons induced asymmetric spikes in the SSE of Pt/YIG [T. Kikkawa et al. Phys. Rev. Lett. 117, 207203 (2016)], may result from the magnon-phonon interactions occurring at the intersections of the quantized magnon and phonon dispersions. The SSE results are helpful for the investigation of the magnon-phonon interaction in the magnetic ultrathin films.

  16. Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films.

    Science.gov (United States)

    Hu, S; Seidel, J

    2016-08-12

    Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

  17. Electrical transport properties and laser-induced voltage effect in La{sub 0.8}Ca{sub 0.2}MnO{sub 3} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Theingi, Mya [Kunming University of Science and Technology, Faculty of Materials Science and Engineering, Kunming (China); University of Yangon, Department of Chemistry, Yangon (Myanmar); Ma, Ji; Zhang, Hui; Cui, Qi; Yi, Jianhong; Chen, Qingming [Kunming University of Science and Technology, Faculty of Materials Science and Engineering, Kunming (China)

    2014-03-15

    La{sub 0.8}Ca{sub 0.2}MnO{sub 3} (LCMO) thin films about 200 nm thickness were grown on untilted and tilted (5 , 10 and 15 ) LaAlO{sub 3} (100) single crystal substrates by pulsed laser deposition technique. Electrical properties of the epitaxial thin films were studied by conventional four-probe technique and the anisotropic thermoelectric properties of the films grown on the tilted substrates have been investigated by laser-induced voltage (LIV) measurements. X-ray diffraction analysis and atomic force microscopy results show that the prepared LCMO thin films have a single phase and high crystalline quality. The remarkably large temperature coefficient of resistance (TCR) values (above 11 %/K) are observed in the all films. TCR value reaches 18 %/K on the film grown on 10 tilted substrate. The intensity of LIV signals monotonously increases with the tilting angles, and the largest signal is 148 mV with the fast time response 229 ns for the film grown on 15 tilted substrate. (orig.)

  18. Strain induced ionic conductivity enhancement in epitaxial Ce0.9Gd0.1O22d

    DEFF Research Database (Denmark)

    Kant, K. Mohan; Esposito, Vincenzo; Pryds, Nini

    2012-01-01

    -plane ionic conductivity in CGO epitaxial thin films. The ionic conductivity is found to increase with decrease in buffer layer thickness. The tailored ionic conductivity enhancement is explained in terms of close relationships among epitaxy, strain, and ionic conductivity....

  19. Epitaxial growth of metallic buffer layer structure and c-axis oriented Pb(Mn1/3,Nb2/3)O3-Pb(Zr,Ti)O3 thin film on Si for high performance piezoelectric micromachined ultrasonic transducer

    Science.gov (United States)

    Thao, Pham Ngoc; Yoshida, Shinya; Tanaka, Shuji

    2017-12-01

    This paper reports on the development of a metallic buffer layer structure, (100) SrRuO3 (SRO)/(100) Pt/(100) Ir/(100) yttria-stabilized zirconia (YSZ) layers for the epitaxial growth of a c-axis oriented Pb(Mn1/3,Nb2/3)O3-Pb(Zr,Ti)O3 (PMnN-PZT) thin film on a (100) Si wafer for piezoelectric micro-electro mechanical systems (MEMS) application. The stacking layers were epitaxially grown on a Si substrate under the optimal deposition condition. A crack-free PMnN-PZT epitaxial thin films was obtained at a thickness up to at least 1.7 µm, which is enough for MEMS applications. The unimorph MEMS cantilevers based on the PMnN-PZT thin film were fabricated and characterized. As a result, the PMnN-PZT thin film exhibited -10 to -12 C/m2 as a piezoelectric coefficient e 31,f and ˜250 as a dielectric constants ɛr. The resultant FOM for piezoelectric micromachined ultrasonic transducer (pMUT) is higher than those of general PZT and AlN thin films. This structure has a potential to provide high-performance pMUTs.

  20. Growth of Ca{sub 2}MnO{sub 4} Ruddlesden-Popper structured thin films using combinatorial substrate epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lacotte, M.; David, A.; Pravarthana, D.; Prellier, W., E-mail: wilfrid.prellier@ensicaen.fr [Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, Université de Basse-Normandie, 6 Bd Maréchal Juin, F-14050 Caen Cedex 4 (France); Grygiel, C. [Laboratoire CIMAP, CEA, CNRS UMR 6252, ENSICAEN, Université de Basse-Normandie, 6 Bd Maréchal Juin, F-14050 Caen Cedex 4 (France); Rohrer, G. S.; Salvador, P. A. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States); Velazquez, M. [CNRS, Université de Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Kloe, R. de [AMETEK B.V, EDAX Application Laboratory, Tilburg (Netherlands)

    2014-12-28

    The local epitaxial growth of pulsed laser deposited Ca{sub 2}MnO{sub 4} films on polycrystalline spark plasma sintered Sr{sub 2}TiO{sub 4} substrates was investigated to determine phase formation and preferred epitaxial orientation relationships (ORs) for isostructural Ruddlesden-Popper (RP) heteroepitaxy, further developing the high-throughput synthetic approach called Combinatorial Substrate Epitaxy (CSE). Both grazing incidence X-ray diffraction and electron backscatter diffraction patterns of the film and substrate were indexable as single-phase RP-structured compounds. The optimal growth temperature (between 650 °C and 800 °C) was found to be 750 °C using the maximum value of the average image quality of the backscattered diffraction patterns. Films grew in a grain-over-grain pattern such that each Ca{sub 2}MnO{sub 4} grain had a single OR with the Sr{sub 2}TiO{sub 4} grain on which it grew. Three primary ORs described 47 out of 49 grain pairs that covered nearly all of RP orientation space. The first OR, found for 20 of the 49, was the expected RP unit-cell over RP unit-cell OR, expressed as [100][001]{sub film}||[100][001]{sub sub}. The other two ORs were essentially rotated from the first by 90°, with one (observed for 17 of 49 pairs) being rotated about the [100] and the other (observed for 10 of 49 pairs) being rotated about the [110] (and not exactly by 90°). These results indicate that only a small number of ORs are needed to describe isostructural RP heteroepitaxy and further demonstrate the potential of CSE in the design and growth of a wide range of complex functional oxides.

  1. Topotactic reductive synthesis of A-site cation-ordered perovskite YBaCo2O x (x = 4.5-5.5) epitaxial thin films

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2016-04-01

    A-site cation-ordered perovskite YBaCo2O x epitaxial films were synthesized by combining pulsed-laser deposition and topotactic reduction using CaH2. The oxygen contents (x) of the films could be controlled in a range of 4.5-5.5 by adjusting the reaction temperature. The c-axis length of the YBaCo2O x films decreased with decreasing x when x ≥ 5.3 but drastically increased when x ˜ 4.5. In contrast, the in-plane lattice constants remained locked-in by the substrate after the reaction. The metal insulator transition observed in bulk YBaCo2O5.5 was substantially suppressed in the present film, likely because of the epitaxial strain effect. The resistivity of the films was significantly enhanced by changing the x value from ˜5.5 to ˜4.5, reflecting the distortion of the CoO x layers.

  2. Nanosheet controlled epitaxial growth of PbZr0.52Ti0.48O3 thin films on glass substrates

    Science.gov (United States)

    Bayraktar, M.; Chopra, A.; Bijkerk, F.; Rijnders, G.

    2014-09-01

    Integration of PbZr0.52Ti0.48O3 (PZT) films on glass substrates is of high importance for device applications. However, to make use of the superior ferro- and piezoelectric properties of PZT, well-oriented crystalline or epitaxial growth with control of the crystal orientation is a prerequisite. In this article, we report on epitaxial growth of PZT films with (100)- and (110)-orientation achieved by utilizing Ca2Nb3O10 (CNO) and Ti0.87O2 (TO) nanosheets as crystalline buffer layers. Fatigue measurements demonstrated stable ferroelectric properties of these films up to 5 × 109 cycles. (100)-oriented PZT films on CNO nanosheets show a large remnant polarization of 21 μC/cm2 that is the highest remnant polarization value compared to (110)-oriented and polycrystalline films reported in this work. A piezoelectric response of 98 pm/V is observed for (100)-oriented PZT film which is higher than the values reported in the literature on Si substrates.

  3. Liquid phase epitaxy of binary III–V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing

    Energy Technology Data Exchange (ETDEWEB)

    Wutzler, Rene, E-mail: r.wutzler@hzdr.de; Rebohle, Lars; Prucnal, Slawomir; Bregolin, Felipe L.; Hübner, Rene; Voelskow, Matthias; Helm, Manfred; Skorupa, Wolfgang [Helmholtz-Zentrum Dresden - Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, 01328 Dresden (Germany)

    2015-05-07

    The integration of III–V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III–V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO{sub 2}/Si/SiO{sub 2} layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III–V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.

  4. Incorporation of La in epitaxial SrTiO{sub 3} thin films grown by atomic layer deposition on SrTiO{sub 3}-buffered Si (001) substrates

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Martin D.; Ngo, Thong Q.; Ekerdt, John G., E-mail: ekerdt@utexas.edu [University of Texas at Austin, Department of Chemical Engineering, Austin, Texas 78712 (United States); Posadas, Agham; Demkov, Alexander A. [University of Texas at Austin, Department of Physics, Austin, Texas 78712 (United States); Karako, Christine M. [University of Dallas, Department of Chemistry, Irving, Texas 75062 (United States); Bruley, John; Frank, Martin M.; Narayanan, Vijay [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)

    2014-06-14

    Strontium titanate, SrTiO{sub 3} (STO), thin films incorporated with lanthanum are grown on Si (001) substrates at a thickness range of 5–25 nm. Atomic layer deposition (ALD) is used to grow the La{sub x}Sr{sub 1−x}TiO{sub 3} (La:STO) films after buffering the Si (001) substrate with four-unit-cells of STO deposited by molecular beam epitaxy. The crystalline structure and orientation of the La:STO films are confirmed via reflection high-energy electron diffraction, X-ray diffraction, and cross-sectional transmission electron microscopy. The low temperature ALD growth (∼225 °C) and post-deposition annealing at 550 °C for 5 min maintains an abrupt interface between Si (001) and the crystalline oxide. Higher annealing temperatures (650 °C) show more complete La activation with film resistivities of ∼2.0 × 10{sup −2} Ω cm for 20-nm-thick La:STO (x ∼ 0.15); however, the STO-Si interface is slightly degraded due to the increased annealing temperature. To demonstrate the selective incorporation of lanthanum by ALD, a layered heterostructure is grown with an undoped STO layer sandwiched between two conductive La:STO layers. Based on this work, an epitaxial oxide stack centered on La:STO and BaTiO{sub 3} integrated with Si is envisioned as a material candidate for a ferroelectric field-effect transistor.

  5. Thickness dependent structural, magnetic and magneto-transport properties of epitaxial Nd{sub 0.50}Sr{sub 0.50}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan, E-mail: p.kumar@krmangalam.edu.in [School of Basic and Applied Sciences, K. R. Mangalam University, Sohna Road, Gurgaon, Haryana 122103 (India); Singh, Hari Krishna, E-mail: hks65@nplindia.org [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India)

    2016-05-06

    We report the thickness-dependent structural, magnetic and magneto-transport properties in epitaxial Nd{sub 0.50}Sr{sub 0.50}MnO{sub 3} thin films (10 to 300nm) prepared by DC magnetron sputtering technique on single crystalline (001) oriented substrate LaAlO{sub 3}. X-ray diffraction pattern reveals the epitaxial growth of all the films and the out-of-plane lattice parameter of films were found to increase with thickness. As thickness of the film increases the paramagnetic insulator (PMI) to ferromagnetic metal (FMM) transition temperature (T{sub C}), charge ordered transition temperature (T{sub CO}) and magnetic moment were found to increase with a strong bifurcation in ZFC-FC magnetization. The asymmetry in the coercivity seen in field dependent magnetization loops (M-H loops) suggests the presence of exchange bias (EB) effect. While temperature dependent resistivity of films show the semiconducting nature for thickness 10-200nm in temperature range from 5-300K, the film of thickness 300nm shows the insulator to metal transition with transition temperature (T{sub IM}) at 175K. Temperature dependent low field magnetoresistance (LFMR) measured at 4kOe found to decrease with thickness and for high field magnetoresistance (HFMR) at 40kOe and 60kOe also show similar dependence and a crossover at intermediate temperature range in the magnitude of MR between 10nm and 200nm films at constant field. Colossal increase in magnetoresistance observed for 10nm film at low temperature.

  6. Tuning structure in epitaxial Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} thin films by using miscut substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mietschke, M., E-mail: m.mietschke@ifw-dresden.de [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Dresden University of Technology, Faculty of Mechanical Science and Engineering, D-01062 Dresden (Germany); Oswald, S.; Fähler, S. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Schultz, L. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Dresden University of Technology, Faculty of Mechanical Science and Engineering, D-01062 Dresden (Germany); Hühne, R. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

    2015-08-31

    Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} (PMN–PT) is one of the most promising ferroelectric material for actuator, dielectric and electrocaloric applications. However, oriented and phase pure thin films are essential to use the outstanding properties of these compounds. In this work it is demonstrated that the use of miscut substrates influences the growth mechanism leading to a significantly broader deposition window to achieve the required film quality. Therefore, epitaxial 0.68Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–0.32PbTiO{sub 3} films were grown by pulsed laser deposition on (001)-oriented single crystalline SrTiO{sub 3} (STO) substrates with a miscut angle between 0 and 15° towards the [100] direction using a conducting La{sub 0.7}Sr{sub 0.3}CoO{sub 3} buffer layer. The influence of the vicinal angle on the PMN–PT structure was studied by high resolution X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. A nearly pure perovskite phase growth with a cube-on-cube epitaxial relationship was obtained on all miscut STO substrates, whereas a significant volume fraction of the pyrochlore phase was present on the standard substrate. Reciprocal space measurements revealed a peak split of the perovskite reflections indicating structural variants of PMN–PT with different c/a ratios. An additional tilting of the PMN–PT planes with respect to the buffer layer was observed on some samples, which might be explained with the incorporation of dislocations according to the Nagai model. Polarization loops were measured in a temperature range between room temperature and 150 °C showing a sharp drop of the remanent polarization above 65 °C on vicinal substrates. - Highlights: • Epitaxial growth of pure perovskite Pb (Mg{sub 1}/{sub 3}Nb{sub 2}/{sub 3})O{sub 3}–PbTiO{sub 3} on miscut SrTiO{sub 3}. • Significant broadening of the deposition window for pyrochlore-free films. • Dependence of the structural parameters

  7. Atomically Smooth Epitaxial Ferroelectric Thin Films for the Development of a Nonvolatile, Ultrahigh Density, Fast, Low Voltage, Radiation-Hard Memory

    National Research Council Canada - National Science Library

    Ahn, Charles H

    2006-01-01

    The goal of this research is to fabricate atomically smooth, single crystalline, complex oxide thin film nanostructures for use in a nonvolatile, ultrahigh density, fast, low voltage, radiation-hard memory...

  8. Thickness and growth-condition dependence of in-situ mobility and carrier density of epitaxial thin-film Bi2Se3

    International Nuclear Information System (INIS)

    Hellerstedt, Jack; Fuhrer, Michael S.; Edmonds, Mark T.; Zheng, C. X.; Chen, J. H.; Cullen, William G.

    2014-01-01

    Bismuth selenide Bi 2 Se 3 was grown by molecular beam epitaxy, while carrier density and mobility were measured directly in situ as a function of film thickness. Carrier density shows high interface n-doping (1.5 × 10 13  cm −2 ) at the onset of film conduction and bulk dopant density of ∼5 × 10 11  cm −2 per quintuple-layer unit, roughly independent of growth temperature profile. Mobility depends more strongly on the growth temperature and is related to the crystalline quality of the samples quantified by ex-situ atomic force microscopy measurements. These results indicate that Bi 2 Se 3 as prepared by widely employed parameters is n-doped before exposure to atmosphere, the doping is largely interfacial in origin, and dopants are not the limiting disorder in present Bi 2 Se 3 films.

  9. Inhomogeneous nucleation and domain wall motion with Barkhausen avalanches in epitaxial PbZr0.4Ti0.6O3 thin films

    International Nuclear Information System (INIS)

    Yang, Sang Mo; Kim, Hun Ho; Kim, Tae Heon; Kim, Ik Joo; Yoon, Jong Gul

    2012-01-01

    We investigated the ferroelectric (FE) domain nucleation and domain wall motion in epitaxial PbZr 0.4 Ti 0.6 O 3 capacitors by using modified piezoresponse force microscopy with the domain-tracing method. From time-dependent FE domain evolution images, we observed that defect-mediated inhomogeneous nucleation occurred with a stochastic nature. In addition, we found that the number of nuclei N(t) was linearly proportional to log t, where t is the accumulated time of the applied pulse fields. The time-dependence of N(t) suggests a distribution of energy barriers for nucleation, which may determine the stochastic nature of domain nucleation. We also observed that the domain grew with consecutive Barkhausen avalanches and that the growth direction became anisotropic when the domain radius was larger than a critical radius of about 100 nm.

  10. X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy of tetragonal Mn72Ge28 epitaxial thin film

    Science.gov (United States)

    Kim, Jinhyeok; Mizuguchi, Masaki; Inami, Nobuhito; Ueno, Tetsuro; Ueda, Shigenori; Takanashi, Koki

    2018-04-01

    An epitaxially grown Mn72Ge28 film with a tetragonal crystal structure was fabricated. It was clarified that the film had a perpendicular magnetization and a high perpendicular magnetic anisotropy energy of 14.3 Merg/cm3. The electronic structure was investigated by X-ray magnetic circular dichroism and hard X-ray photoelectron spectroscopy. The obtained X-ray magnetic circular dichroism spectrum revealed that the Mn orbital magnetic moment governed the magnetocrystalline anisotropy of the Mn72Ge28 film. A doublet structure was observed for the Mn 2p3/2 peak of hard X-ray photoelectron spectrum, indicating the spin exchange interaction between the 2p core-hole and 3d valence electrons.

  11. Electronic structure of Fe1.08Te bulk crystals and epitaxial FeTe thin films on Bi2Te3

    Science.gov (United States)

    Arnold, Fabian; Warmuth, Jonas; Michiardi, Matteo; Fikáček, Jan; Bianchi, Marco; Hu, Jin; Mao, Zhiqiang; Miwa, Jill; Singh, Udai Raj; Bremholm, Martin; Wiesendanger, Roland; Honolka, Jan; Wehling, Tim; Wiebe, Jens; Hofmann, Philip

    2018-02-01

    The electronic structure of thin films of FeTe grown on Bi2Te3 is investigated using angle-resolved photoemission spectroscopy, scanning tunneling microscopy and first principles calculations. As a comparison, data from cleaved bulk Fe1.08Te taken under the same experimental conditions is also presented. Due to the substrate and thin film symmetry, FeTe thin films grow on Bi2Te3 in three domains, rotated by 0°, 120°, and 240°. This results in a superposition of photoemission intensity from the domains, complicating the analysis. However, by combining bulk and thin film data, it is possible to partly disentangle the contributions from three domains. We find a close similarity between thin film and bulk electronic structure and an overall good agreement with first principles calculations, assuming a p-doping shift of 65 meV for the bulk and a renormalization factor of around two. By tracking the change of substrate electronic structure upon film growth, we find indications of an electron transfer from the FeTe film to the substrate. No significant change of the film’s electronic structure or doping is observed when alkali atoms are dosed onto the surface. This is ascribed to the film’s high density of states at the Fermi energy. This behavior is also supported by the ab initio calculations.

  12. Fatigue-resistant epitaxial Pb(Zr,Ti)O3 capacitors on Pt electrode with ultra-thin SrTiO3 template layers

    International Nuclear Information System (INIS)

    Takahara, Seiichi; Morimoto, Akiharu; Kawae, Takeshi; Kumeda, Minoru; Yamada, Satoru; Ohtsubo, Shigeru; Yonezawa, Yasuto

    2008-01-01

    Lead zirconate-titanate Pb(Zr,Ti)O 3 (PZT) capacitors with Pt bottom electrodes were prepared on MgO substrates by pulsed laser deposition (PLD) technique employing SrTiO 3 (STO) template layer. Perovskite PZT thin films are prepared via stoichiometric target using the ultra-thin STO template layers while it is quite difficult to obtain the perovskite PZT on Pt electrode via stoichiometric target in PLD process. The PZT capacitor prepared with the STO template layer showed good hysteresis and leakage current characteristics, and it showed an excellent fatigue resistance. The ultra-thin STO template layers were characterized by angle-resolved X-ray photoelectron spectroscopy measurement. The effect of the STO template layer is discussed based on the viewpoint of the perovskite nucleation and diffusion of Pb and O atoms

  13. Effect of elastic compliances and higher order Landau coefficients on the phase diagram of single domain epitaxial Pb(Zr,TiO3 (PZT thin films

    Directory of Open Access Journals (Sweden)

    M. Mtebwa

    2014-12-01

    Full Text Available We report the qualitative study of the influence of both elastic compliances and higher order terms of Landau free energy potential on the phase diagram of Pb(Zr0.5Ti0.5O3 thin films by using a single domain Landau theory. Although the impact of elastic compliances and higher order terms of the Landau free energy potential on the phase diagram of ferroelectric thin films are known, the sensitivity of the phase diagram of PZT thin film on these parameters have not been reported. It is demonstrated that, while values of elastic compliances affect the positions of the phase boundaries including phase transition temperature of the cubic phase; higher order terms can potentially introduce an a1a2-phase previously predicted in PbTiO3 phase diagram.

  14. Epitaxial thin-film growth of Ruddlesden-Popper-type Ba3Zr2O7 from a BaZrO3 target by pulsed laser deposition

    International Nuclear Information System (INIS)

    Butt, Shariqa Hassan; Rafique, M.S.; Siraj, K.; Latif, A.; Afzal, Amina; Awan, M.S.; Bashir, Shazia; Iqbal, Nida

    2016-01-01

    Ruddlesden-Popper Ba 3 Zr 2 O 7 thin films have been synthesized via pulsed laser deposition (PLD) technique. The optimization of deposition parameters in PLD enables the formation of thin film of metastable Ba 3 Zr 2 O 7 phase from BaZrO 3 target. In order to see the post-annealing effects on the structural and optical properties, the deposited Ba 3 Zr 2 O 7 thin films were annealed at 500, 600 and 800 C. X-ray diffraction (XRD) reveals the formation of Ba 3 Zr 2 O 7 phase with tetragonal structure. The changes in the surface of the deposited films were analysed by FE-SEM and AFM. The thin film post-annealed at 500 C exhibited the best structural, optical and surface properties. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Zr and O exist mainly in the form of Ba 3 Zr 2 O 7 Ruddlesden-Popper-type perovskite structure. (orig.)

  15. A modular designed ultra-high-vacuum spin-polarized scanning tunneling microscope with controllable magnetic fields for investigating epitaxial thin films.

    Science.gov (United States)

    Wang, Kangkang; Lin, Wenzhi; Chinchore, Abhijit V; Liu, Yinghao; Smith, Arthur R

    2011-05-01

    A room-temperature ultra-high-vacuum scanning tunneling microscope for in situ scanning freshly grown epitaxial films has been developed. The core unit of the microscope, which consists of critical components including scanner and approach motors, is modular designed. This enables easy adaptation of the same microscope units to new growth systems with different sample-transfer geometries. Furthermore the core unit is designed to be fully compatible with cryogenic temperatures and high magnetic field operations. A double-stage spring suspension system with eddy current damping has been implemented to achieve ≤5 pm z stability in a noisy environment and in the presence of an interconnected growth chamber. Both tips and samples can be quickly exchanged in situ; also a tunable external magnetic field can be introduced using a transferable permanent magnet shuttle. This allows spin-polarized tunneling with magnetically coated tips. The performance of this microscope is demonstrated by atomic-resolution imaging of surface reconstructions on wide band-gap GaN surfaces and spin-resolved experiments on antiferromagnetic Mn(3)N(2)(010) surfaces.

  16. Growth modes and epitaxy of FeAl thin films on a-cut sapphire prepared by pulsed laser and ion beam assisted deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Xiang; Trautvetter, Moritz; Ziemann, Paul [Institut für Festkörperphysik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany); Wiedwald, Ulf [Institut für Festkörperphysik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany); Fakultät für Physik, Universität Duisburg-Essen, Lotharstraße 1, 47057 Duisburg (Germany)

    2014-01-14

    FeAl films around equiatomic composition are grown on a-cut (112{sup ¯}0) sapphire substrates by ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD) at ambient temperature. Subsequent successive annealing is used to establish chemical order and crystallographic orientation of the films with respect to the substrate. We find a strongly [110]-textured growth for both deposition techniques. Pole figures prove the successful preparation of high quality epitaxial films by PLD with a single in-plane orientation. IBAD-grown films, however, exhibit three in-plane orientations, all of them with broad angular distributions. The difference of the two growth modes is attributed to the existence of a metastable intermediate crystalline orientation as concluded from nonassisted sputter depositions at different substrate temperatures. The formation of the chemically ordered crystalline B2 phase is accompanied by the expected transition from ferromagnetic to paramagnetic behavior of the films. In accordance with the different thermally induced structural recovery, we find a step-like magnetic transition to paramagnetic behavior after annealing for 1 h at T{sub A} = 300 °C for IBAD deposition, while PLD-grown films show a gradual decrease of ferromagnetic signals with rising annealing temperatures.

  17. Surface segregation as a means of gettering Cu in liquid-phase-epitaxy silicon thin layers grown from Al-Cu-Si solutions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, T.H.; Ciszek, T.F.; Reedy, R.; Asher, S.; King, D. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    The authors demonstrate that, by using the natural surface segregation phenomenon, Cu can be gettered to the surface from the bulk of silicon layers so that its concentrations in the liquid-phase-epitaxy (LPE) layers are much lower than its solubility at the layer growth temperature and the reported 10{sup 17} cm{sup {minus}3} degradation threshold for solar-cell performance. Secondary-ion mass spectroscopy (SIMS) analysis indicates that, within a micron-deep sub-surface region, Cu accumulates even in as-grown LPE samples. Slower cooling after growth to room temperature enhances this Cu enrichment. X-ray photoelectron spectroscopy (XPS) measurement shows as much as 3.2% Cu in a surface region of about 50 {Angstrom}. More surface-sensitive, ion-scattering spectroscopy (ISS) analysis further reveals about 7% of Cu at the top surface. These results translate to an areal gettering capacity of about 1.0 x 10{sup 16} cm{sup {minus}2}, which is higher than the available total-area density of Cu in the layer and substrate (3.6 x 10{sup 15} cm{sup {minus}2} for a uniform 1.2 x 10{sup 17}cm{sup {minus}3} Cu throughout the layer and substrate with a total thickness of 300 {mu}m).

  18. Structural characterization of epitaxial YBa2Cu3O7 thin films on step-edge substrates by means of high-resolution electron microscopy

    International Nuclear Information System (INIS)

    Jia, C.L.; Kabius, B.; Urban, K.

    1993-01-01

    The microstructure of YBa 2 Cu 3 O 7 films epitaxially grown on step-edge (0 0 1) SrTiO 3 and LaAlO 3 substrates has been characterized by means of high-resolution electron microscopy. The results indicate a relationship between the microstructure of the film across a step and the angle the step makes with the substrate plane. On a steep, high-angle step, the film grows with its c-axis perpendicular to that of the film on substrate surface so that two grain boundaries are formed. In the upper grain boundary, on the average, a (0 1 3) habit plane alternates with a (1 0 3) habit plane. This alternating structure is caused by twinning in the orthorhombic structure. The lower boundaries consist of a chain of (0 1 3)(0 1 3) and (0 1 0)(0 0 1) type segments exhibiting a tendency to tilt the whole habit plane toward the a-b plane of the flank film. Dislocations, stacking faults and misfit strains were also observed in or close to the boundaries. (orig.)

  19. Anisotropic magnetotransport in epitaxial La2/3Ca1/3MnO3 thin films grown by dc-sputtering

    International Nuclear Information System (INIS)

    Moran, O.; Saldarriaga, W.; Prieto, P.; Baca, E.

    2005-01-01

    We have conducted a comprehensive study of the in-plane/out-of-plane magnetic and magnetotransport properties on (001)-oriented La 2/3 Ca 1/3 MnO 3 films epitaxially grown on single crystal (001)-SrTiO 3 substrates by dc-sputtering at high oxygen pressure. The films grew under tensile strain imposed by the lattice mismatch with the substrate. SQUID magnetometry indicated the presence of magnetocrystalline anisotropy at temperatures below the ferromagnetic Curie temperature T C with the easy plane being the film plane. Resistance measurements in magnetic field strengths of up to 6 T, applied both normal and parallel to the film plane, evidenced a distinctive dependence of the resistivity below T C on the angle of the applied field with respect to the plane of the film. During these measurements, transport current and applied magnetic field was all along maintained perpendicular to each other. Neither low-field magnetoresistance (LFMR) nor large magnetoresistance hysteresis were observed on these samples, suggesting that the tensile strain in the first monolayers has been partially released. Additionally, by rotating the sample 360 around an axis parallel to film plane, in magnetic fields ≥2 T, a quadratic sinusoidal dependence of the magnetoresistance (MR) on the polar angle θ was observed. These results can be consistently interpreted in frame of a generalized version of the theory of anisotropic magnetoresistance in transition-metal ferromagnets. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Structure-property relations in sputter deposited epitaxial (1-x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 thin films

    Science.gov (United States)

    Frederick, Joshua C.

    Lead-based ferroelectric materials are of significant technological importance for sensing and actuation due to their high piezoelectric performance (i.e., the ability to convert an electrical signal to mechanical displacement, and vice versa). Traditionally, bulk ceramic or single crystals materials have filled these roles; however, emerging technologies stand to benefit by incorporating thin films to achieve miniaturization while maintaining high efficiency and sensitivity. Currently, chemical systems that have been well characterized in bulk form (e.g. Pb(Mg1/3Nb2/3)O3- xPbTiO3, or PMN-xPT) require further study to optimize both the chemistry and structure for deployment in thin film devices. Furthermore, the effect of internal electric fields is more significant at the length scales of thin films, resulting in self biases that require compensation to reveal their intrinsic dielectric response. To this end, the structure-property relations of epitaxial PMN-xPT films sputter deposited on a variety of substrates were investigated. Attention was paid to how the structure (i.e., strain state, crystal structure, domain configuration, and defects) gave rise to the ferroelectric, dielectric, and piezoelectric response. Three-dimensional visualization of the dielectric response as a simultaneous function of electric field and temperature revealed the true phase transition of the films, which was found to correspond to the strain state and defect concentration. A lead-buffered anneal process was implemented to enhance the ferroelectric and dielectric response of the films without altering their stoichiometry. It was discovered that PMN- xPT films could be domain-engineered to exhibit a mixed domain state through chemistry and substrate choice. Such films exhibited a monoclinic distortion similar to that of the bulk compositions near the morphotropic phase boundary. Finally, it was revealed that the piezoelectric response could be greatly enhanced by declamping the film

  1. Magnetron-sputter epitaxy of β-FeSi2(220)/Si(111) and β-FeSi2(431)/Si(001) thin films at elevated temperatures

    International Nuclear Information System (INIS)

    Liu Hongfei; Tan Chengcheh; Chi Dongzhi

    2012-01-01

    β-FeSi 2 thin films have been grown on Si(111) and Si(001) substrates by magnetron-sputter epitaxy at 700 °C. On Si(111), the growth is consistent with the commonly observed orientation of [001]β-FeSi 2 (220)//[1-10]Si(111) having three variants, in-plane rotated 120° with respect to one another. However, on Si(001), under the same growth conditions, the growth is dominated by [-111]β-FeSi 2 (431)//[110]Si(001) with four variants, which is hitherto unknown for growing β-FeSi 2 . Photoelectron spectra reveal negligible differences in the valance-band and Fe2p core-level between β-FeSi 2 grown on Si(111) and Si(001) but an apparent increased Si-oxidization on the surface of β-FeSi 2 /Si(001). This phenomenon is discussed and attributed to the Si-surface termination effect, which also suggests that the Si/Fe ratio on the surface of β-FeSi 2 (431)/Si(001) is larger than that on the surface of β-FeSi 2 (220)/Si(111).

  2. Fabrication and examination of epitaxial HTSC/isolator thin films on sapphire substrates for application in high frequency devices; Herstellung und Untersuchung von epitaktischen HTSL/Isolator-Schichten auf Saphirsubstraten zur Anwendung in HF-Bauelementen

    Energy Technology Data Exchange (ETDEWEB)

    Kittel, H.

    1995-10-01

    The use of high temperature superconductors (HTSC) like YBCO with distinct lower surface resistance compared to normal conductors allows miniaturisation of high frequency (HF) circuits. The object of this work was the fabrication of YBCO thin films on low loss sapphire substrates applicable for stripline devices. To induce epitaxial growth and to avoid chemical reaction at the film-substrate boundary buffer layers were investigated. The examination of the growth properties and especially of the surface impedance has been allotted particular importance. In contrast to CaTiO{sub 3} it was possible to deposit CeO{sub 2}-buffer layers in direct growth up to a thickness of about 30 nm without cracks. The films show all growth properties required and even Laue-oscillations being a feature of high quality growth enabling the determination of film thickness distribution without destruction. The YBCO growth-, transport- and HF-properties meet the ones of YBCO films on standard substrates. A remarkable result is that the mosaic distribution of the CEO film, itself strongly dependend on film thickness, does not influence that of the YBCO film considerably. Rather it changes its shape subsequently due to YBCO deposition. A further particularity in contrast to deposition on standard substrates is the need to adjust the substrate heater tempeature for deposition of YBCO films with thicknesses {>=}300 nm needed for HF application. To demonstrate their usefullness some stripline devices like planar coils and side coupled filters have been fabricated and characterised. (orig.)

  3. Raman scattering and x-ray diffractometry studies of epitaxial TiO2 and VO2 thin films and multilayers on α-Al2O3(11 bar 20)

    International Nuclear Information System (INIS)

    Foster, C.M.; Chiarello, R.P.; Chang, H.L.M.; You, H.; Zhang, T.J.; Frase, H.; Parker, J.C.; Lam, D.J.

    1993-01-01

    Epitaxial thin films of TiO 2 and VO 2 single layers and TiO 2 /VO 2 multilayers were grown on (11 bar 20) sapphire (α-Al 2 O 3 ) substrates using the metalorganic chemical vapor deposition technique and were characterized using Raman scattering and four x-ray diffractometry. X-ray diffraction results indicate that the films are high quality single crystal material with well defined growth plane and small in-plane and out-of-plane mosaic. Single-layer films are shown to obey the Raman selection rules of TiO 2 and VO 2 single crystals. The close adherence to the Raman selection rules indicates the high degree of orientation of the films, both parallel and perpendicular to the growth plane. Selection rule spectra of two and three layer TiO 2 /VO 2 multilayers are dominated by the VO 2 layers with only minimal signature of the TiO 2 layers. Due to the low band gap of semiconducting vanadium dioxide, we attribute the strong signature of the VO 2 layers to resonant enhancement of the VO 2 Raman component accompanied with absorption of the both the incident and scattered laser light from the TiO 2 layers

  4. Role of dual-laser ablation in controlling the Pb depletion in epitaxial growth of Pb(Zr0.52Ti0.48)O3 thin films with enhanced surface quality and ferroelectric properties

    Science.gov (United States)

    Mukherjee, Devajyoti; Hyde, Robert; Mukherjee, Pritish; Srikanth, Hariharan; Witanachchi, Sarath

    2012-03-01

    Pb depletion in Pb(Zr0.52Ti0.48)O3 (PZT) thin films has remained as a major setback in the growth of defect-free PZT thin films by pulsed laser ablation techniques. At low excimer (KrF) laser fluences, the high volatility of Pb in PZT leads to non-congruent target ablation and, consequently, non-stoichiometric films, whereas, at high laser fluences, the inherent ejection of molten droplets from the target leads to particulate laden films, which is undesirable in heterostructure growth. To overcome these issues, a dual-laser ablation (PLDDL) process that combines an excimer (KrF) laser and CO2 laser pulses was used to grow epitaxial PZT films on SrTiO3 (100) and MgO (100) substrates. Intensified-charge-coupled-detector (ICCD) images and optical emission spectroscopy of the laser-ablated plumes in PLDDL revealed a broader angular expansion and enhanced excitation of the ablated species as compared to those for single-laser ablation (PLDSL). This led to the growth of particulate-free PZT films with higher Pb content, better crystallinity, and lower surface roughness as compared to those deposited using PLDSL. For FE measurements, PZT capacitors were fabricated in situ using the latticed-matched metallic oxide, La0.7Sr0.3MnO3, as the top and bottom electrodes. PZT films deposited using PLDDL exhibited enhanced polarization for all driving voltages as compared to those deposited using PLDSL. A highest remanent polarization (Pr) of ˜91 μC/cm2 and low coercive field of ˜40 kV/cm was recorded at 9 V driving voltage. Fatigue characterization revealed that PZT films deposited using PLDDL showed unchanging polarization, even after 109 switching cycles.

  5. On the Relationship of Magnetocrystalline Anisotropy and Stoichiometry in Epitaxial L1{sub 0} CoPt(001) and FePt(001) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Barmak, K

    2004-08-10

    Two series of epitaxial CoPt and FePt films, with nominal thicknesses of 42 or 50 nm, were prepared by sputtering onto single crystal MgO(001) substrates in order to investigate the chemical ordering and the resultant magnetic properties as a function of alloy composition. In the first series, the film composition was kept constant, while the substrate temperature was increased from 144 to 704 C. In the second series the substrate temperature was kept constant at 704 C for CoPt and 620 C for FePt, while the alloy stoichiometry was varied in the nominalrange of 40-60 at% Co(Fe). Film compositions and thicknesses were measured via Rutherford backscattering spectrometry. The lattice and long-range order parameter for the L1{sub 0} phase were obtained for both sets of films using x-ray diffraction. The room-temperature magnetocrystalline anisotropy constants were determined for a subset of the films using torque magnetometry. The order parameter was found to increase with increasing temperature, with ordering occurring more readily in FePt when compared with CoPt. A perpendicular anisotropy developed in CoPt for substrate temperatures above 534 C and in FePt above 321 C. The structure and width of the magnetic domains in CoPt and FePt, as seen by magnetic force microscopy, also demonstrated an increase in magnetic anisotropy with increasing temperature. For the films deposited at the highest temperatures (704 C for CoPt and 620 C for FePt), the order parameter reached a maximum near the equiatomic composition, whereas the magnetocrystalline anisotropy increased as the concentration of Co or Fe was increased from below to slightly above the equiatomic composition. It is concluded that non-stoichiometric L1{sub 0} CoPt and FePt, with a slight excess of Co or Fe, are preferable for applications requiring the highest anisotropies.

  6. Epitaxial growth of rhenium with sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Seongshik [National Institute of Standards and Technology, Boulder, CO 80305 (United States) and Department of Physics, University of Illinois, Urbana, IL 61801 (United States)]. E-mail: soh@boulder.nist.gov; Hite, Dustin A. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Cicak, K. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Osborn, Kevin D. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Simmonds, Raymond W. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); McDermott, Robert [University of California, Santa Barbara, CA 93106 (United States); Cooper, Ken B. [University of California, Santa Barbara, CA 93106 (United States); Steffen, Matthias [University of California, Santa Barbara, CA 93106 (United States); Martinis, John M. [University of California, Santa Barbara, CA 93106 (United States); Pappas, David P. [National Institute of Standards and Technology, Boulder, CO 80305 (United States)

    2006-02-21

    We have grown epitaxial Rhenium (Re) (0001) films on {alpha}-Al{sub 2}O{sub 3} (0001) substrates using sputter deposition in an ultra high vacuum system. We find that better epitaxy is achieved with DC rather than with RF sputtering. With DC sputtering, epitaxy is obtained with the substrate temperatures above 700 deg. C and deposition rates below 0.1 nm/s. The epitaxial Re films are typically composed of terraced hexagonal islands with screw dislocations, and island size gets larger with high temperature post-deposition annealing. The growth starts in a three dimensional mode but transforms into two dimensional mode as the film gets thicker. With a thin ({approx}2 nm) seed layer deposited at room temperature and annealed at a high temperature, the initial three dimensional growth can be suppressed. This results in larger islands when a thick film is grown at 850 deg. C on the seed layer. We also find that when a room temperature deposited Re film is annealed to higher temperatures, epitaxial features start to show up above {approx}600 deg. C, but the film tends to be disordered.

  7. Structural and magnetic properties of Co-doped (La,Sr)TiO{sub 3} epitaxial thin films probed using x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Copie, O; Mattana, R; Bibes, M; Cros, V; Herranz, G; Anane, A; Ranchal, R; Jacquet, E; Bouzehouane, K; Petroff, F; Barthelemy, A [Unite Mixte de Physique CNRS/Thales, Campus de l' Ecole Polytechnique, 1 Avenue A Fresnel, 91767 Palaiseau, France and Universite Paris-Sud 11, 91405 Orsay (France); Rode, K [Center for Research on Adaptative Nanostructures and Nanodevices, Trinity College Dublin, Dublin 2, Republic of Ireland (Ireland); Arrio, M-A [Institut de Mineralogie et de Physique des Milieux Condenses CNRS, Universite Pierre et Marie Curie, 140 rue de Lourmel 75015 Paris (France); Bencok, P; Brookes, N B, E-mail: agnes.barthelemy@thalesgroup.co [European Synchrotron Radiation Facility, 6 rue Horowitz, 38083 Grenoble (France)

    2009-10-07

    We report a study of Co-doped La{sub 0.37}Sr{sub 0.63}TiO{sub 3-delta} thin films grown by pulsed laser deposition in various oxygen pressure conditions. X-ray absorption spectroscopy and magnetic circular dichroism measurements at the Co L{sub 2,3} edges reveal that the cobalt mainly substitutes for the titanium and is in an ionic state. Nevertheless, in some films, indications of additional cobalt metallic impurities were found, suggesting that the intrinsic character of this magnetic system remains questionable.

  8. The Growth of Thin Epitaxial Copper Films on Ruthenium (0001)and Oxygen-Precovered Ruthenium (0001) as studied by X-ray Photoelectron diffraction

    International Nuclear Information System (INIS)

    Ruebush, Scott Daniel

    1997-01-01

    demonstrates the considerable usefulness of XPD in studying epitaxial overlayer growth with and without surfactants present

  9. Surface chemistry and growth mechanisms studies of homo epitaxial (1 0 0) GaAs by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yan Dawei; Wu Weidong; Zhang Hong; Wang Xuemin; Zhang Hongliang; Zhang Weibin; Xiong Zhengwei; Wang Yuying; Shen Changle; Peng Liping; Han Shangjun; Zhou Minjie

    2011-01-01

    In this paper, GaAs thin film has been deposited on thermally desorbed (1 0 0) GaAs substrate using laser molecular beam epitaxy. Scanning electron microscopy, in situ reflection high energy electron diffraction and in situ X-ray photoelectron spectroscopy are applied for evaluation of the surface morphology and chemistry during growth process. The results show that a high density of pits is formed on the surface of GaAs substrate after thermal treatment and the epitaxial thin film heals itself by a step flow growth, resulting in a smoother surface morphology. Moreover, it is found that the incorporation of As species into GaAs epilayer is more efficient in laser molecular beam epitaxy than conventional molecular beam epitaxy. We suggest the growth process is impacted by surface chemistry and morphology of GaAs substrate after thermal treatment and the growth mechanisms are discussed in details.

  10. Epitaxial growth of ultra-thin NbN films on AlxGa1−xN buffer-layers

    International Nuclear Information System (INIS)

    Krause, S; Meledin, D; Desmaris, V; Pavolotsky, A; Belitsky, V; Rudziński, M; Pippel, E

    2014-01-01

    The suitability of Al x Ga 1−x N epilayers to deposit onto ultra-thin NbN films has been demonstrated for the first time. High quality single-crystal films with 5 nm thickness confirmed by high resolution transmission electron microscopy (HRTEM) have been deposited in a reproducible manner by means of reactive DC magnetron sputtering at elevated temperatures and exhibit critical temperatures (T c ) as high as 13.2 K and residual resistivity ratio (RRR) ∼1 on hexagonal GaN epilayers. On increasing the Al content x in the Al x Ga 1−x N epilayer above 20%, a gradual deterioration of T c to 10 K was observed. Deposition of NbN on bare silicon substrates served as a reference and comparison. Excellent spatial homogeneity of the fabricated films was confirmed by R(T) measurements of patterned micro-bridges across the entire film area. The superconducting properties of these films were further characterized by critical magnetic field and critical current measurements. It is expected that the employment of GaN material as a buffer-layer for the deposition of ultra-thin NbN films will prospectively benefit terahertz electronics, particularly hot electron bolometer (HEB) mixers. (paper)

  11. Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3 Nanocomposites and Single-Phase Thin Films.

    Science.gov (United States)

    Lloyd-Hughes, J; Mosley, C D W; Jones, S P P; Lees, M R; Chen, A; Jia, Q X; Choi, E-M; MacManus-Driscoll, J L

    2017-04-12

    Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7 Sr 0.3 MnO 3 . At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. The VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.

  12. Effects of background oxygen pressure on dielectric and ferroelectric properties of epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrTiO3

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-11-01

    Oxygen partial pressure (PO_2) in pulsed laser deposition significantly influences the composition, microstructure, and electrical properties of epitaxial misfit strain-relieved 450nm ⟨001⟩ oriented epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated SrTiO3. Films deposited at 400mTorr exhibit high remnant and saturated polarization of 7.5 and 16.5μC /cm2, respectively, which is ˜100% increase over the ones grown at 100mTorr. The dielectric constant linearly increases from 220 to 450 with increasing PO2. The observed changes in surface morphology of the films and their properties are shown to be due to the suppression of volatile A-site cation loss.

  13. Recovery of oscillatory magneto-resistance in phase separated La0.3Pr0.4Ca0.3MnO3 epitaxial thin films

    International Nuclear Information System (INIS)

    Alagoz, H. S.; Jeon, J.; Mahmud, S. T.; Saber, M. M.; Chow, K. H.; Jung, J.; Prasad, B.; Egilmez, M.

    2013-01-01

    In-plane angular dependent magneto-resistance has been studied in La 0.3 Pr 0.4 Ca 0.3 MnO 3 (LPCMO) manganite thin films deposited on the (100) oriented NdGaO 3 , and (001) oriented SrTiO 3 and LaAlO 3 substrates. At temperatures where the electronic phase separation is the strongest, a metastable irreversible state exists in the films whose resistivity ρ attains a large time dependent value. The ρ decreases sharply with an increasing angle θ between the magnetic field and the current, and does not display an expected oscillatory cos 2 θ/sin 2 θ dependence for all films. The regular oscillations are recovered during repetitive sweeping of θ between 0° and 180°. We discuss possible factors that could produce these unusual changes in the resistivity

  14. Temperature-dependent leakage current behavior of epitaxial Bi0.5Na0.5TiO3-based thin films made by pulsed laser deposition

    Science.gov (United States)

    Hejazi, M. M.; Safari, A.

    2011-11-01

    This paper discusses the electrical conduction mechanisms in a 0.88 Bi0.5Na0.5TiO3-0.08 Bi0.5K0.5TiO3-0.04 BaTiO3 thin film in the temperature range of 200-350 K. The film was deposited on a SrRuO3/SrTiO3 substrate by pulsed laser deposition technique. At all measurement temperatures, the leakage current behavior of the film matched well with the Lampert's triangle bounded by three straight lines of different slopes. The relative location of the triangle sides varied with temperature due to its effect on the density of charge carriers and un-filled traps. At low electric fields, the ohmic conduction governed the leakage mechanism. The calculated activation energy of the trap is 0.19 eV implying the presence of shallow traps in the film. With increasing the applied field, an abrupt increase in the leakage current was observed. This was attributed to a trap-filling process by the injected carriers. At sufficiently high electric fields, the leakage current obeyed the Child's trap-free square law suggesting the space charge limited current was the dominant mechanism.

  15. Carrier compensation mechanism in heavily Nb-doped anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nogawa, H; Chikamatsu, A; Hirose, Y; Hasegawa, T [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Nakao, S [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Kumigashira, H; Oshima, M, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, Tokyo 113-8656 (Japan)

    2011-09-14

    We investigated the electronic structures of anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} (TNO) thin films as a function of Nb concentration x using photoemission spectroscopy (PES) measurements to elucidate the origin of the abrupt decrease in carrier activation in heavily Nb-doped regime. The existing intensity ratio of Nb{sup 5+} evaluated from Nb 3d core-level PES spectra maintained a constant value of {approx}0.8 at x = 0.06-0.3, implying that electron carriers generated by Nb doping are compensated by p-type defects. Ti 2p-3d and O1s-2p resonant PES measurements of x = 0.06-0.3 films revealed that the in-gap states positioned {approx}1 eV below the Fermi level (E{sub F}) have a mixed character of Ti 3d and O 2p orbitals, whereas the states at E{sub F} mainly have a Ti 3d nature. We proposed a carrier compensation mechanism that interstitial oxygen atoms strongly combined with surrounding Nb atoms kill conduction electrons in heavily Nb-doped anatase TiO{sub 2}.

  16. Effect of strain on the transport and magnetoresistance properties of La0.8Ca0.2MnO3 epitaxial thin films

    International Nuclear Information System (INIS)

    Zhang, H D; Li, M; An, Y K; Mai, Z H; Gao, J; Hu, F X; Wang, Y; Jia, Q J

    2007-01-01

    The true residual stress in La 0.8 Ca 0.2 MnO 3 (LCMO) thin films of various thicknesses deposited on STO substrates under the same deposition conditions was measured quantitatively by x-ray diffraction sin 2 ψ method. The truly strain-induced effect on the transport and magnetoresistance (MR) properties of LCMO films was investigated. The in-plane residual stress (σ 11 ) in the LCMO film is tensile, while the out-of-plane one (σ 33 ) is compressive. Moreover, the value of σ 33 is larger than that of σ 11 . With increasing film thickness, the crystalline unit cell of the LCMO film reduces; also both the in- and out-of-plane components of the residual stress in the LCMO film decrease. It was found that the resistivity, T MI and MR strongly depend on the in-plane tensile stress σ 11 (or/and the out-of-plane stress σ 33 ). With the increase in the in-plane stress σ 11 (or/and the out-of-plane stress σ 33 ), the values of resistivity and MR increase, while T MI decreases. The truly strain-induced effect on the transport and magnetoresistance properties of LCMO film is discussed briefly

  17. Growth of pseudomorphic structures through organic epitaxy

    International Nuclear Information System (INIS)

    Kaviyil, Sreejith Embekkat; Sassella, Adele; Borghesi, Alessandro; Campione, Marcello; Su Genbo; He Youping; Chen Chenjia

    2012-01-01

    The control of molecular orientation in thin solid film phases of organic semiconductors is a basic factor for the exploitation of their physical properties for optoelectronic devices. We compare structural and optical properties of thin films of the organic semiconductor α-quarterthiophene grown by molecular beam epitaxy on different organic substrates. We show how epitactic interactions, characteristic of the surface of organic crystals, can drive the orientation of the crystalline overlayer and the selection of specific polymorphs and new pseudomorphic phases. We identify a key role in this phenomenon played by the marked groove-like corrugations present in some organic crystal surfaces. Since different polymorphs possess rather different performance in terms of, e.g., charge carrier mobility, this strategy is demonstrated to allow for the growth of oriented phases with enhanced physical properties, while keeping the substrate at room temperature. These results provide useful guidelines for the design of technological substrates for organic epitaxy and they substantiate the adoption of an organic epitaxy approach for the fabrication of optoelectronic devices based on thin films of organic semiconductors.

  18. Research Update: Enhanced energy storage density and energy efficiency of epitaxial Pb0.9La0.1(Zr0.52Ti0.48O3 relaxor-ferroelectric thin-films deposited on silicon by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Minh D. Nguyen

    2016-08-01

    Full Text Available Pb0.9La0.1(Zr0.52Ti0.48O3 (PLZT relaxor-ferroelectric thin films were grown on SrRuO3/SrTiO3/Si substrates by pulsed laser deposition. A large recoverable storage density (Ureco of 13.7 J/cm3 together with a high energy efficiency (η of 88.2% under an applied electric field of 1000 kV/cm and at 1 kHz frequency was obtained in 300-nm-thick epitaxial PLZT thin films. These high values are due to the slim and asymmetric hysteresis loop when compared to the values in the reference undoped epitaxial lead zirconate titanate Pb(Zr0.52Ti0.48O3 ferroelectric thin films (Ureco = 9.2 J/cm3 and η = 56.4% which have a high remanent polarization and a small shift in the hysteresis loop, under the same electric field.

  19. Epitaxial growth and multiferroic properties of cation-engineered (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} thin film on Ir-buffered (0 0 1) MgO substrate

    Energy Technology Data Exchange (ETDEWEB)

    Paik, Hanjong [Department of Materials Science and Engineering, Cornell University, Ithaca NY 14853 (United States); Kim, Hyun-Suk [Department of Materials Engineering, Chungnam University, Daejeon 305-764 (Korea, Republic of); Hong, Jongin, E-mail: hongj@cau.ac.kr [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

    2015-04-15

    Highlights: • Epitaxial (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} thin film was grown on the Ir-buffered (0 0 1) MgO substrate by pulsed laser deposition. • Its ferroelectric polarization switching was investigated by piezoresponse force microscopy. • Its ferromagnetic hysteresis at room temperature and ferrimagnetic–ferromagnetic transition at low temperature were evaluated. • Artificial A- and B-site cation engineering would result in stable multiferroic properties at room temperature. - Abstract: An epitaxial (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} (BLB-FNO) thin film was successfully grown on an Ir-buffered (0 0 1) MgO substrate by pulsed laser deposition (PLD). The “cube-on-cube” epitaxial relation, (0 0 1)[1 0 0] BLB-FNO//(0 0 1)[1 0 0] Ir//(0 0 1)[1 0 0] MgO, was confirmed by X-ray diffraction (XRD) pole figures and cross-sectional high-resolution transmission electron microscopy (HRTEM). The ferroelectric polarization switching of the BLB-FNO thin film was investigated by piezoresponse force microscopy (PFM). Its magnetic properties, such as ferromagnetic hysteresis at room temperature and possible magnetic transition at low temperature, were also evaluated. Accordingly, we successfully demonstrated that artificial A- and B-site cation engineering would allow for stable multiferroic properties at room temperature.

  20. Strain-Modulated Epitaxy

    National Research Council Canada - National Science Library

    Brown, April

    1999-01-01

    Strain-Modulated Epitaxy (SME) is a novel approach, invented at Georgia Tech, to utilize subsurface stressors to control strain and therefore material properties and growth kinetics in the material above the stressors...

  1. Molecular-beam epitaxial growth and ion-beam analysis systems for functional materials research

    International Nuclear Information System (INIS)

    Takeshita, H.; Aoki, Y.; Yamamoto, S.; Naramoto, H.

    1992-01-01

    Experimental systems for molecular beam epitaxial growth and ion beam analysis have been designed and constructed for the research of inorganic functional materials such as thin films and superlattices. (author)

  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. Out-of-plane tilted Josephson junctions of bi-epitaxial YBa2Cu3O x thin films on tilted-axes NdGaO3 substrates with CeO2 seeding layer

    International Nuclear Information System (INIS)

    Mozhaev, Peter B.; Mozhaeva, Julia E.; Bdikin, Igor K.; Kotelyanskii, Iosif M.; Luzanov, Valery A.; Zybtsev, Sergey G.; Hansen, Jorn Bindslev; Jacobsen, Claus S.

    2006-01-01

    Bi-epitaxial heterostructures YBa 2 Cu 3 O x (YBCO)/CeO 2 /NdGaO 3 were prepared on tilted-axes NdGaO 3 substrates using laser ablation technique. The heterostructures were patterned for electrical measurements using photolithography and ion-beam milling. Electrical anisotropy of the YBCO film was tested on the ion-beam etched surface. Bi-epitaxial junctions with four different orientations of the bi-epitaxial border were fabricated and studied. The measured I V curves showed flux-flow behavior with critical current density 2.5 x 10 4 A/cm 2 for the twist-type junctions and 1.5 x 10 3 A/cm 2 for [1 0 0]-tilt type junctions

  4. Pulsed laser deposition of epitaxial Sr(RuxSn1-x)O3 thin film electrodes and KNbO3/Sr(RuxSn1-x)O3 bilayers

    International Nuclear Information System (INIS)

    Christen, H.M.; Boatner, L.A.; English, L.Q.; Geea, L.A.; Marrero, P.J.; Norton, D.P.

    1995-01-01

    Sr(Ru x Sn 1-x ) 3 is proposed as a new conducting oxide for use in epitaxial multilayer structures. The Sr(Ru o 48 Sn 0.52 )0 3 composition exhibits an excellent lattice match with (100)-oriented KTaO 3 , and films of this composition grown by pulsed laser deposition on KTaO 3 , SrTiO 3 , and LaAlO 3 substrates have been analyzed by X-ray diffraction, Rutherford backscattering/ion channeling, and resistivity measurements. Epitaxial KNbO 3 /Sr(Ru 0.48 Sn 0.52 )O 3 bilayers have been successfully grown

  5. Selenidation of epitaxial silicene on ZrB2

    NARCIS (Netherlands)

    Wiggers, F. B.; Yamada-Takamura, Y.; Kovalgin, A. Y.; de Jong, M. P.

    2018-01-01

    The deposition of elemental Se on epitaxial silicene on ZrB2 thin films was investigated with synchrotron-based core-level photoelectron spectroscopy and low-energy electron diffraction. The deposition of Se at room temperature caused the appearance of Si 2p peaks with chemical shifts of n × 0.51 ±

  6. Thickness dependence of the strain, band gap and transport properties of epitaxial In{sub 2}O{sub 3} thin films grown on Y-stabilised ZrO{sub 2}(111)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, K H L; Oropeza, F E; Egdell, R G [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA (United Kingdom); Lazarov, V K [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Veal, T D; McConville, C F [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Walsh, A, E-mail: Russell.egdell@chem.ox.ac.uk [Department of Chemistry, Kathleen Lonsdale Materials Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2011-08-24

    Epitaxial films of In{sub 2}O{sub 3} have been grown on Y-stabilised ZrO{sub 2}(111) substrates by molecular beam epitaxy over a range of thicknesses between 35 and 420 nm. The thinnest films are strained, but display a 'cross-hatch' morphology associated with a network of misfit dislocations which allow partial accommodation of the lattice mismatch. With increasing thickness a 'dewetting' process occurs and the films break up into micron sized mesas, which coalesce into continuous films at the highest coverages. The changes in morphology are accompanied by a progressive release of strain and an increase in carrier mobility to a maximum value of 73 cm{sup 2} V{sup -1} s{sup -1}. The optical band gap in strained ultrathin films is found to be smaller than for thicker films. Modelling of the system, using a combination of classical pair-wise potentials and ab initio density functional theory, provides a microscopic description of the elastic contributions to the strained epitaxial growth, as well as the electronic effects that give rise to the observed band gap changes. The band gap increase induced by the uniaxial compression is offset by the band gap reduction associated with the epitaxial tensile strain.

  7. GaN/NbN epitaxial semiconductor/superconductor heterostructures

    Science.gov (United States)

    Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D. Scott; Nepal, Neeraj; Downey, Brian P.; Muller, David A.; Xing, Huili G.; Meyer, David J.; Jena, Debdeep

    2018-03-01

    Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors—silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor—an electronic gain element—to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance—a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

  8. Seed layer technique for high quality epitaxial manganite films

    Directory of Open Access Journals (Sweden)

    P. Graziosi

    2016-08-01

    Full Text Available We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

  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. Silicon epitaxy on textured double layer porous silicon by LPCVD

    International Nuclear Information System (INIS)

    Cai Hong; Shen Honglie; Zhang Lei; Huang Haibin; Lu Linfeng; Tang Zhengxia; Shen Jiancang

    2010-01-01

    Epitaxial silicon thin film on textured double layer porous silicon (DLPS) was demonstrated. The textured DLPS was formed by electrochemical etching using two different current densities on the silicon wafer that are randomly textured with upright pyramids. Silicon thin films were then grown on the annealed DLPS, using low-pressure chemical vapor deposition (LPCVD). The reflectance of the DLPS and the grown silicon thin films were studied by a spectrophotometer. The crystallinity and topography of the grown silicon thin films were studied by Raman spectroscopy and SEM. The reflectance results show that the reflectance of the silicon wafer decreases from 24.7% to 11.7% after texturing, and after the deposition of silicon thin film the surface reflectance is about 13.8%. SEM images show that the epitaxial silicon film on textured DLPS exhibits random pyramids. The Raman spectrum peaks near 521 cm -1 have a width of 7.8 cm -1 , which reveals the high crystalline quality of the silicon epitaxy.

  11. Abstracts of 4. International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology

    International Nuclear Information System (INIS)

    2001-01-01

    4. International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology is the periodically held forum for discussion the problems connected with manufacturing of different nanostructures (thin films, quantum wells, quantum dots) needed in microelectronics. Preparation of such materials with desirable optical, electrical and magnetic properties being determined by their chemical composition and crystal structure has been discussed in detail during the workshop sessions. Optimization of crystal growth methods such as VPE and MBE from the view point of obtained material properties has also been extensively discussed

  12. Epitaxial growth and characterization of CuGa2O4 films by laser molecular beam epitaxy

    OpenAIRE

    Hongling Wei; Zhengwei Chen; Zhenping Wu; Wei Cui; Yuanqi Huang; Weihua Tang

    2017-01-01

    Ga2O3 with a wide bandgap of ∼ 4.9 eV can crystalize in five crystalline phases. Among those phases, the most stable monoclinic β-Ga2O3 has been studied most, however, it is hard to find materials lattice matching with β-Ga2O3 to grown epitaxial thin films for optoelectronic applications. In this work, CuGa2O4 bulk were prepared by solid state reaction as target, and the films were deposited on sapphire substrates by laser molecular beam epitaxy (L-MBE) at different substrate temperatures. Th...

  13. Enhanced dielectric nonlinearity in epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chunrui, E-mail: chunrui.ma@gmail.com, E-mail: jwu@ku.edu; Wu, Judy, E-mail: chunrui.ma@gmail.com, E-mail: jwu@ku.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, 66045 (United States); Ma, Beihai [Energy Systems Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Mi, Shao-Bo [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi' an Jiaotong University, Xi' an 710049 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Liu, Ming [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi' an Jiaotong University, Xi' an 710049 (China)

    2014-04-21

    High quality c-axis oriented epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films were fabricated using pulsed laser deposition on (001) LaAlO{sub 3} substrates with conductive LaNiO{sub 3} buffers. Besides confirmation of the in-plane and out-of-plane orientations using X-ray diffraction, transmission electron microscopy study has revealed columnar structure across the film thickness with column width around 100 nm. Characterization of ferroelectric properties was carried out in comparison with polycrystalline Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films to extract the effect of epitaxial growth. It is found that the ratio between the irreversible Rayleigh parameter and reversible parameter increased up to 0.028 cm/kV at 1 kHz on epitaxial samples, which is more than twice of that on their polycrystalline counterparts. While this ratio decreased to 0.022 cm/kV with increasing frequency to100 kHz, a much less frequency dependence was observed as compared to the polycrystalline case. The epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films exhibited a higher mobility of domain wall and the higher extrinsic contribution to the dielectric properties, as well as reduced density of defects, indicating that it is promising for tunable and low power consumption devices.

  14. Epitaxial growth of hybrid nanostructures

    Science.gov (United States)

    Tan, Chaoliang; Chen, Junze; Wu, Xue-Jun; Zhang, Hua

    2018-02-01

    Hybrid nanostructures are a class of materials that are typically composed of two or more different components, in which each component has at least one dimension on the nanoscale. The rational design and controlled synthesis of hybrid nanostructures are of great importance in enabling the fine tuning of their properties and functions. Epitaxial growth is a promising approach to the controlled synthesis of hybrid nanostructures with desired structures, crystal phases, exposed facets and/or interfaces. This Review provides a critical summary of the state of the art in the field of epitaxial growth of hybrid nanostructures. We discuss the historical development, architectures and compositions, epitaxy methods, characterization techniques and advantages of epitaxial hybrid nanostructures. Finally, we provide insight into future research directions in this area, which include the epitaxial growth of hybrid nanostructures from a wider range of materials, the study of the underlying mechanism and determining the role of epitaxial growth in influencing the properties and application performance of hybrid nanostructures.

  15. Reclamation of a molecular beam epitaxy system and conversion for oxide epitaxy

    International Nuclear Information System (INIS)

    Carver, Alexander G.; Henderson, Walter; Doolittle, W. Alan

    2008-01-01

    An early 1980s vintage molecular beam epitaxy system, a Varian Gen II system, originally used for HgCdTe epitaxy, was converted into a system capable of growing thin-film complex metal oxides. The nature of some of the alternative oxides requires a thorough cleaning and, in some cases, complete replacement of system components. Details are provided regarding the chemistry of the etchants used, safety requirements for properly handling, and disposal of large quantities of etchants and etch by-products, and components that can be reused versus components that require replacement are given. Following the given procedures, an ultimate base pressure of 2x10 -10 Torr was obtained. Films grown in the system after reclamation contained no evidence of previously present materials down to the detection limit of secondary ion mass spectrometry

  16. Effect of manganese doping on remnant polarization and leakage current in (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 epitaxial thin films on SrTiO3

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-05-01

    Single phase, epitaxial, ⟨001⟩ oriented, undoped and 1mol% Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10μC /cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1mol% Mn doped films is 13kV/cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50kV/cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors.

  17. Spin transport in epitaxial graphene

    Science.gov (United States)

    Tbd, -

    2014-03-01

    Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non volatile devices such as the new STT-MRAM. Beyond its widely distributed application in data storage it aims at providing more complex architectures and a powerful beyond CMOS solution for information processing. The recent discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. We will present experimental results allowing us to assess the potential of graphene for spintronics. We will show that unprecedented highly efficient spin information transport can occur in epitaxial graphene leading to large spin signals and macroscopic spin diffusion lengths (~ 100 microns), a key enabler for the advent of envisioned beyond-CMOS spin-based logic architectures. We will also show that how the device behavior is well explained within the framework of the Valet-Fert drift-diffusion equations. Furthermore, we will show that a thin graphene passivation layer can prevent the oxidation of a ferromagnet, enabling its use in novel humide/ambient low-cost processes for spintronics devices, while keeping its highly surface sensitive spin current polarizer/analyzer behavior and adding new enhanced spin filtering property. These different experiments unveil promising uses of graphene for spintronics.

  18. Ferroelectric and piezoelectric properties of epitaxial PZT films and devices on silicon

    NARCIS (Netherlands)

    Nguyen, Duc Minh

    2010-01-01

    In this thesis, the integration of lead zirconate titanate Pb(Zr,Ti)O3 (PZT) thin films into piezoelectric microelectromechanical systems (MEMS) based on silicon is studied. In these structures, all epitaxial oxide layers (thin film/electrode/buffer-layer(s)) were deposited by pulsed laser

  19. Crystallization engineering as a route to epitaxial strain control

    Directory of Open Access Journals (Sweden)

    Andrew R. Akbashev

    2015-10-01

    Full Text Available The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001SrTiO3 and (001LaAlO3 substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001SrTiO3 results in a coherently strained film, the same films obtained on (001LaAlO3 showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001SrTiO3. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  20. Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

    Directory of Open Access Journals (Sweden)

    Lijuan Wang

    2017-02-01

    Full Text Available Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial growth of bismide thin films and nanostructures, surface, structural, electric, transport and optic properties of various binaries and bismide alloys, and device applications.

  1. Coexistence of Weak Ferromagnetism and Polar Lattice Distortion in Epitaxial NiTiO3 thin films of the LiNbO3-Type Structure

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas [Environmental Molecular Sciences Lab., Richland, WA (United States); Droubay, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bowden, Mark E. [Environmental Molecular Sciences Lab., Richland, WA (United States); Colby, Robert J. [Environmental Molecular Sciences Lab., Richland, WA (United States); Manandhar, Sandeep [Environmental Molecular Sciences Lab., Richland, WA (United States); Shutthanandan, Vaithiyalingam [Environmental Molecular Sciences Lab., Richland, WA (United States); Hu, Dehong [Environmental Molecular Sciences Lab., Richland, WA (United States); Kabius, Bernd C. [Environmental Molecular Sciences Lab., Richland, WA (United States); Apra, Edoardo [Environmental Molecular Sciences Lab., Richland, WA (United States); Shelton, William A. [Environmental Molecular Sciences Lab., Richland, WA (United States); Chambers, Scott A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-04-15

    We report the magnetic and structural characteristics of epitaxial NiTiO3 films grown by pulsed laser deposition that are isostructural with acentric LiNbO3 (space group R3c). Optical second harmonic generation and magnetometry demonstrate lattice polarization at room temperature and weak ferromagnetism below 250 K, respectively. These results appear to be consistent with earlier predictions from first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LiNbO3 structure. This acentric form of NiTiO3 is believed to be one of the rare examples of ferroelectrics exhibiting weak ferromagnetism generated by a Dzyaloshinskii-Moriya interaction.

  2. Room-Temperature Multiferroics and Thermal Conductivity of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 Epitaxial Thin Films (x = 0.1 and 0.2).

    Science.gov (United States)

    Zhang, Ji; Sun, Wei; Zhao, Jiangtao; Sun, Lei; Li, Lei; Yan, Xue-Jun; Wang, Ke; Gu, Zheng-Bin; Luo, Zhen-Lin; Chen, Yanbin; Yuan, Guo-Liang; Lu, Ming-Hui; Zhang, Shan-Tao

    2017-08-02

    Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

  3. 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.

  4. Magnetic anisotropies in epitaxial Fe3O4/GaAs(100) patterned structures

    International Nuclear Information System (INIS)

    Zhang, W.; Zhang, D.; Yuan, S. J.; Huang, Z. C.; Zhai, Y.; Wong, P. K. J.; Wu, J.; Xu, Y. B.

    2014-01-01

    Previous studies on epitaxial Fe 3 O 4 rings in the context of spin-transfer torque effect have revealed complicated and undesirable domain structures, attributed to the intrinsic fourfold magnetocrystalline anisotropy in the ferrite. In this Letter, we report a viable solution to this problem, utilizing a 6-nm-thick epitaxial Fe 3 O 4 thin film on GaAs(100), where the fourfold magnetocrystalline anisotropy is negligible. We demonstrate that in the Fe 3 O 4 planar wires patterned from our thin film, such a unique magnetic anisotropy system has been preserved, and relatively simple magnetic domain configurations compared to those previous reports can be obtained

  5. Magnetic properties of novel epitaxial films

    International Nuclear Information System (INIS)

    Bader, S.D.; Moog, E.R.

    1986-09-01

    The surface magneto-optic Kerr effect (SMOKE) is used to explore the magnetism of ultra-thin Fe Films extending into the monolayer regime. Both bcc α-Fe and fcc γ-Fe single-crystalline, multilayer films are prepared on the bulk-terminated (1 x 1) structures of Au(100) and Cu(100), respectively. The characterizations of epitaxy and growth mode are performed using low energy electron diffraction and Auger electron spectroscopy. Monolayer-range Fe/Au(100) is ferromagnetic with a lower Curie temperature than bulk α-Fe. The controversial γ-Fe/Cu(100) system exhibits a striking, metastable, surface magnetic phase at temperatures above room temperature, but does not exhibit bulk ferromagnetism

  6. Investigation of the epitaxial growth of Pb(Zr{sub 0,52}Ti{sub 0,48})O{sub 3} thin films and their application in ferroelectric superconducting field effect transistors; Untersuchung des epitaktischen Wachstums duenner Pb(Zr{sub 0,52}Ti{sub 0,48})O{sub 3}-Schichten und ihre Anwendung in ferroelektrischen supraleitenden Feldeffektransistoren

    Energy Technology Data Exchange (ETDEWEB)

    Aidam, R

    1999-02-01

    The influences of the polarization of ferroelectric Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) films on the properties of YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) films were investigated in ferroelectric superconducting field effect transistors (FSuFETs). First the epitaxial growth of PZT films deposited by reactive sputtering in an argon/oxygen atmosphere was investigated. SrTiO{sub 3} single crystals and YBCO thin films proved as suitable substrates. The lead content of the PZT films depended sensitively on the deposition temperature T{sub s} and the gas pressure. By using a high pressure of 0.26 mbar the correct stoichiometry could be achieved up to an maximum T{sub s} of 580 C. Above a minimum T{sub s} of 540 C the ferroelectric perovskite structure grew. In the optimum temperature range between 560 C and 580 C the films grew with a minimum mosaic spread of {delta}{omega} < 0.3 and a small amount of less than 1% of paraelectric phase. The best ferroelectric properties could be obtained for films with the highest degree of epitaxy and the correct stoichiometry. The maximum remanent polarization amounted P{sub r} = 61 {mu}C/cm{sup 2} and the coercive field E{sub C} was 150 kV/cm at 77 K. The breakdown field was four to five times larger than E{sub C}. Fatigue studies revealed a loss of switchable polarization of 30% after 10{sup 8} cycles at 77 K, whereas loss of retention and the effect of ageing were negligible. During the process of oxidation of the heterostructure at 400 C and an oxygen pressure of 800 mbar a reaction at the PZT/YBCO interface was observed, which lead to a degradation of the transport properties of the superconductor. This reaction could be avoided by a thin SrTiO{sub 3} buffer layer without disturbing the ferroelectric hysteresis essentially.

  7. Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111/Si(111

    Directory of Open Access Journals (Sweden)

    Abe Shunsuke

    2010-01-01

    Full Text Available Abstract Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111 thin films on Si(111 has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D2-TPD and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111/Si(111 is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001 proceeds.

  8. Multifunctional epitaxial systems on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968 (United States); Prater, John Thomas [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2016-09-15

    Multifunctional heterostructures can exhibit a wide range of functional properties, including colossal magneto-resistance, magnetocaloric, and multiferroic behavior, and can display interesting physical phenomena including spin and charge ordering and strong spin-orbit coupling. However, putting this functionality to work remains a challenge. To date, most of the work reported in the literature has dealt with heterostructures deposited onto closely lattice matched insulating substrates such as DyScO{sub 3}, SrTiO{sub 3} (STO), or STO buffered Si(100) using concepts of lattice matching epitaxy (LME). However, strain in heterostructures grown by LME is typically not fully relaxed and the layers contain detrimental defects such as threading dislocations that can significantly degrade the physical properties of the films and adversely affect the device characteristics. In addition, most of the substrates are incompatible with existing CMOS-based technology, where Si (100) substrates dominate. This review discusses recent advances in the integration of multifunctional oxide and non-oxide materials onto silicon substrates. An alternative thin film growth approach, called “domain matching epitaxy,” is presented which identifies approaches for minimizing lattice strain and unwanted defects in large misfit systems (7%–25% and higher). This approach broadly allows for the integration of multifunctional materials onto silicon substrates, such that sensing, computation, and response functions can be combined to produce next generation “smart” devices. In general, pulsed laser deposition has been used to epitaxially grow these materials, although the concepts developed here can be extended to other deposition techniques, as well. It will be shown that TiN and yttria-stabilized zirconia template layers provide promising platforms for the integration of new functionality into silicon-based computer chips. This review paper reports on a number of thin

  9. Epitaxial thin-film growth of Ruddlesden-Popper-type Ba{sub 3}Zr{sub 2}O{sub 7} from a BaZrO{sub 3} target by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Butt, Shariqa Hassan; Rafique, M.S.; Siraj, K.; Latif, A.; Afzal, Amina [University of Engineering and Technology, Laser and Optronics Centre, Department of Physics, Lahore (Pakistan); Awan, M.S. [Ibn-e-Sina Institute of Science and Technology (ISIT), Islamabad (Pakistan); Bashir, Shazia [Government College University, Centre for Advanced Studies in Physics, Lahore (Pakistan); Iqbal, Nida [Universiti Teknologi Malaysia, Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Johor Bahru, Johor (Malaysia)

    2016-07-15

    Ruddlesden-Popper Ba{sub 3}Zr{sub 2}O{sub 7} thin films have been synthesized via pulsed laser deposition (PLD) technique. The optimization of deposition parameters in PLD enables the formation of thin film of metastable Ba{sub 3}Zr{sub 2}O{sub 7} phase from BaZrO{sub 3} target. In order to see the post-annealing effects on the structural and optical properties, the deposited Ba{sub 3}Zr{sub 2}O{sub 7} thin films were annealed at 500, 600 and 800 C. X-ray diffraction (XRD) reveals the formation of Ba{sub 3}Zr{sub 2}O{sub 7} phase with tetragonal structure. The changes in the surface of the deposited films were analysed by FE-SEM and AFM. The thin film post-annealed at 500 C exhibited the best structural, optical and surface properties. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Zr and O exist mainly in the form of Ba{sub 3}Zr{sub 2}O{sub 7} Ruddlesden-Popper-type perovskite structure. (orig.)

  10. Research Update: Enhancement of figure of merit for energy-harvesters based on free-standing epitaxial Pb(Zr0.52Ti0.480.99Nb0.01O3 thin-film cantilevers

    Directory of Open Access Journals (Sweden)

    Minh D. Nguyen

    2017-07-01

    Full Text Available All-oxide free-standing cantilevers were fabricated with epitaxial (001-oriented Pb(Zr0.52Ti0.48O3 (PZT and Pb(Zr0.52Ti0.480.99Nb0.01O3 (PNZT as piezoelectric layers and SrRuO3 electrodes. The ferroelectric and piezoelectric hysteresis loops were measured. From the zero-bias values, the figure-of-merits (FOMs for piezoelectric energy harvesting systems were calculated. For the PNZT cantilever, an extremely large value FOM = 55 GPa was obtained. This very high value is due to the large shifts of the hysteresis loops such that the zero-bias piezoelectric coefficient e31f is maximum and the zero-bias dielectric constant is strongly reduced compared to the value in the undoped PZT device. The results show that by engineering the self-bias field the energy-harvesting properties of piezoelectric systems can be increased significantly.

  11. Research Update: Enhancement of figure of merit for energy-harvesters based on free-standing epitaxial Pb(Zr0.52Ti0.48)0.99Nb0.01O3 thin-film cantilevers

    Science.gov (United States)

    Nguyen, Minh D.; Houwman, Evert; Dekkers, Matthijn; Schlom, Darrell; Rijnders, Guus

    2017-07-01

    All-oxide free-standing cantilevers were fabricated with epitaxial (001)-oriented Pb(Zr0.52Ti0.48)O3 (PZT) and Pb(Zr0.52Ti0.48)0.99Nb0.01O3 (PNZT) as piezoelectric layers and SrRuO3 electrodes. The ferroelectric and piezoelectric hysteresis loops were measured. From the zero-bias values, the figure-of-merits (FOMs) for piezoelectric energy harvesting systems were calculated. For the PNZT cantilever, an extremely large value FOM = 55 GPa was obtained. This very high value is due to the large shifts of the hysteresis loops such that the zero-bias piezoelectric coefficient e31f is maximum and the zero-bias dielectric constant is strongly reduced compared to the value in the undoped PZT device. The results show that by engineering the self-bias field the energy-harvesting properties of piezoelectric systems can be increased significantly.

  12. Epitaxial growth of silicon and germanium on (100-oriented crystalline substrates by RF PECVD at 175 °C

    Directory of Open Access Journals (Sweden)

    Mauguin O.

    2012-11-01

    Full Text Available We report on the epitaxial growth of crystalline Si and Ge thin films by standard radio frequency plasma enhanced chemical vapor deposition at 175 °C on (100-oriented silicon substrates. We also demonstrate the epitaxial growth of silicon films on epitaxially grown germanium layers so that multilayer samples sustaining epitaxy could be produced. We used spectroscopic ellipsometry, Raman spectroscopy, transmission electron microscopy and X-ray diffraction to characterize the structure of the films (amorphous, crystalline. These techniques were found to provide consistent results and provided information on the crystallinity and constraints in such lattice-mismatched structures. These results open the way to multiple quantum-well structures, which have been so far limited to few techniques such as Molecular Beam Epitaxy or MetalOrganic Chemical Vapor Deposition.

  13. Ge films grown on Si substrates by molecular-beam epitaxy below 450 deg. C

    International Nuclear Information System (INIS)

    Liu, J.; Kim, H.J.; Hul'ko, O.; Xie, Y.H.; Sahni, S.; Bandaru, P.; Yablonovitch, E.

    2004-01-01

    Ge thin films are grown on Si(001) substrates by molecular-beam epitaxy at 370 deg. C. The low-temperature epitaxial growth is compatible with the back-end thermal budget of current generation complementary metal-oxide-semiconductor technology, which is restricted to less than 450 deg. C. Reflection high-energy electron diffraction shows that single-crystal Ge thin films with smooth surfaces could be achieved below 450 deg. C. Double-axis x-ray θ/2θ scans also show that the epitaxial Ge films are almost fully strain-relaxed. As expected, cross-sectional transmission electron microscopy shows a network of dislocations at the interface. Hydrogen and oxide desorption techniques are proved to be necessary for improving the quality of the Ge films, which is reflected in improved minority carrier diffusion lengths and exceptionally low leakage currents

  14. Epitaxial superlattices with titanium nitride as a plasmonic component for optical hyperbolic metamaterials

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Saha, Bivas; Liu, Jing

    2014-01-01

    , we address these issues by realizing an epitaxial superlattice as an HMM. The superlattice consists of ultrasmooth layers as thin as 5 nm and exhibits sharp interfaces which are essential for high-quality HMM devices. Our study reveals that such a TiN-based superlattice HMM provides a higher PDOS...

  15. An epitaxial transparent conducting perovskite oxide: double-doped SrTiO3

    NARCIS (Netherlands)

    Ravichandran, Jayakanth; Siemons, W.; Heijmerikx, Herman; Huijben, Mark; Majumdar, Arun; Ramesh, Ramamoorthy

    2010-01-01

    Epitaxial thin films of strontium titanate doped with different concentrations of lanthanum and oxygen vacancies were grown on LSAT substrates by pulsed laser deposition technique. Films grown with 5−15% La doping and a critical growth pressure of 1−10 mTorr showed high transparency (>70−95%) in the

  16. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  17. Functional oxide thin films by pulsed-laser deposition: ion beam nanostructuring of epitaxial YBa2Cu3O7-d and growth of conductive transparent Zn1-xAlxO on compliant substrates

    International Nuclear Information System (INIS)

    Dosmailov, M.

    2015-01-01

    This doctoral dissertation is composed of two parts. The first part of the work is dedicated to the modification of YBCO film by Masked Ion Beam Structuring (MIBS) and the commensurability effects between flux line lattice and defect lattice caused by ion irradiation. The motivation of this part of the work is to understand better the physics of the vortex matter. The YBCO film was grown on MgO substrate by Pulsed Laser Deposition (PLD) method. PLD is a thin film deposition method where high power pulsed laser beam is employed to ablate the material on the target and to deposit thin film on the substrate. This process occurs in high vacuum or in gas background. The main advantage of MIBS is the direct, non-contact structuring of superconducting devices with a resolution mainly limited by masking technique. MIBS is a parallel process that can be used for patterning large sample areas. It avoids surface degradation. The resolution of the MIBS technique can be 10 nm for a 100 nm thick YBCO film irradiated with 75 keV He+. The YBCO film modified by ion irradiation has higher resistivity by factor of ⁓ 3 at temperature T =290K, and much reduced critical temperature Tc ⁓ 47K and broadened transition [Delta]Tc ⁓ 8K. The YBCO film was irradiated with 75keV He+. The square array of nanodots with diameter 175 nm and lattice constant 300 nm was produced using a Si stencil mask. The nanodots are serving as pinning centers for vortices that arise in the superconducting materials of type II in the presence of the magnetic field. The commensurability effects manifest themselves in pronounced minimum of magnetoresistance and pronounced maximum of the critical current at the matching fields. The entire Jc(B) is described by tentative model. Moreover, a strong hysteresis of magnetoresistance and the critical current density Jc(B) is observed (Cooperation with Prof. Wolfgang Lang, University of Vienna). It is interesting to further investigate the physics of vortex matter. The

  18. Preparation and properties of thin films treatise on materials science and technology

    CERN Document Server

    Tu, K N

    1982-01-01

    Treatise on Materials Science and Technology, Volume 24: Preparation and Properties of Thin Films covers the progress made in the preparation of thin films and the corresponding study of their properties. The book discusses the preparation and property correlations in thin film; the variation of microstructure of thin films; and the molecular beam epitaxy of superlattices in thin film. The text also describes the epitaxial growth of silicon structures (thermal-, laser-, and electron-beam-induced); the characterization of grain boundaries in bicrystalline thin films; and the mechanical properti

  19. Recovery of oscillatory magneto-resistance in phase separated La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Alagoz, H. S., E-mail: alagoz@ualberta.ca; Jeon, J.; Mahmud, S. T.; Saber, M. M.; Chow, K. H., E-mail: khchow@ualberta.ca; Jung, J., E-mail: jjung@ualberta.ca [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada); Prasad, B. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Egilmez, M. [Department of Physics, American University of Sharjah, Sharjah (United Arab Emirates)

    2013-12-02

    In-plane angular dependent magneto-resistance has been studied in La{sub 0.3}Pr{sub 0.4}Ca{sub 0.3}MnO{sub 3} (LPCMO) manganite thin films deposited on the (100) oriented NdGaO{sub 3}, and (001) oriented SrTiO{sub 3} and LaAlO{sub 3} substrates. At temperatures where the electronic phase separation is the strongest, a metastable irreversible state exists in the films whose resistivity ρ attains a large time dependent value. The ρ decreases sharply with an increasing angle θ between the magnetic field and the current, and does not display an expected oscillatory cos{sup 2}θ/sin{sup 2}θ dependence for all films. The regular oscillations are recovered during repetitive sweeping of θ between 0° and 180°. We discuss possible factors that could produce these unusual changes in the resistivity.

  20. Subsurface contributions in epitaxial rare-earth silicides

    Energy Technology Data Exchange (ETDEWEB)

    Luebben, Olaf; Shvets, Igor V. [Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), School of Physics, Trinity College, Dublin (Ireland); Cerda, Jorge I. [Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, Madrid (Spain); Chaika, Alexander N. [Institute of Solid State Physics, RAS, Chernogolovka (Russian Federation)

    2015-07-01

    Metallic thin films of heavy rare-earth silicides epitaxially grown on Si(111) substrates have been widely studied in recent years because of their appealing properties: unusually low values of the Schottky barrier height, an abrupt interface, and a small lattice mismatch. Previous studies also showed that these silicides present very similar atomic and electronic structures. Here, we examine one of these silicides (Gd{sub 3}Si{sub 5}) using scanning tunneling microscopy (STM) image simulations that go beyond the Tersoff-Hamann approach. These simulations strongly indicate an unusual STM depth sensitivity for this system.

  1. Metallic substrate materials for thin film oxygen transport membranes for application in a fossil power plant

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Y.; Baumann, S.; Sebold, D.; Meulenberg, W.A.; Stoever, D. [Forschungszentrum Juelich GmbH (DE). Inst. fuer Energieforschung (IEF) - IEF-1 Materials Synthesis and Processing

    2010-07-01

    La{sub 0.58}Sr{sub 0.4}CO{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58428) and Ba{sub 0.5}Sr{sub 0.5}CO{sub 0.8}Fe{sub 3-{delta}} (BSCF5582) exhibit high oxygen permeability due to their high ionic and electronic conductivity. For this reason they are under discussion for application in oxygen transport membranes (OTMs) in zero-emission power plants using oxyfuel technology. A thin film membrane which can increase the oxygen flux is beneficial and a structural substrate is required. Two types of Ni-base alloys were studied as substrate material candidates with a number of advantages, such as high strength, high temperature stability, easy joining and similar thermal expansion coefficient to the selected perovskite materials. Chemical compositions and thermal expansion coefficients of Ni-base alloys were measured in this study. LSCF58428 and BSCF5582 layers were screen printed on Ni-based alloys and co-fired at high temperature in air. The microstructure and element analysis of samples were characterized by scanning electron microscopy (SEM and EDX). A Ni-base alloy, MCrAlY, with a high Al content was the most suitable substrate material, and showed better chemical compatibility with perovskite materials at high temperature than Hastelloy X, which is a chromia-forming Ni-base alloy. A reaction occurred between Sr in the perovskite and the alumina surface layers on MCr-AlY. However, the reaction zone did not increase in thickness during medium-term annealing at 800 C in air. Hence, it is expected that this reaction will not prevent the application of MCr-AlY as a substrate material. (orig.)

  2. 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.

  3. Epitaxial growth and superconducting properties of YBa23Cu3O7 thin films and YBa2Cu3O7/Dy(Pr)Ba2Cu3O7 superlattices

    International Nuclear Information System (INIS)

    Triscone, J.M.; Brunner, O.; Antognazza, L.; Kent, A.D.; Fischer, O.; Karkut, M.G.

    1990-01-01

    The authors have prepared in situ REBa 2 Cu 3 O 7 (REBCO) (RE = Y, Pr, Dy) thin films and YBCO/Dy(Pr)BCO superlattices by single target dc planar magnetron sputtering. YBCO/DyBCO superlattices have been realized with modulation wavelength as short as 24 Angstrom, i.e., a unit cell of YBCO alternates with a unit cell of DyBCO, on average. The superconducting properties of such superlattices are indistinguishable from those of single layers. T co 's (zero resistance) are between 85 and 89K, and the residual resistivity ratios are between 2.5 and 3. In contrast to these results, when YBCO is layered with PrBCO, which is insulating, a dramatic change in the superconducting properties is observed. The authors have been able to artificially vary the coupling between single 12 Angstrom unit cell of YBCO by interposing insulating planes of PrBCO. As the YBCO layer separation increases, T c is reduced and the transition broadens showing evidence of 2-D superconducting fluctuations

  4. THE IMPACT OF THE METHOD OF UNDERLAY SURFACE PROCESSING ON THE DEVELOPMENT OF DEFECTS IN EPITAXIAL COMPOSITIONS IN THE COURSE OF SILICON PHOTO-TRANSDUCERS PRODUCTION

    Directory of Open Access Journals (Sweden)

    Zoya Nikonova

    2017-06-01

    Full Text Available For the production of silicon photo-transducers (PhT the acquisition of epitaxial compositions (EC with high resistivity of working layer. One of the main parameters characterizing the quality of EC is the density of dislocation and other structural defects. Great impact on the development of defects during epitaxial growth is produced by the quality of underlay preparation before that. Multiple research of relatively thin (less than 20-30 microns epitaxial layers demonstrated, that contamination or damages of underlay surface cause the development of defects of wrapping, counterparts, macroscopic protuberances in the growing layer. During inverted epitaxy there are no high requirements as for structural perfection of epitaxial layer as far as in PhT, produced on the basis of EC for which inverted silicon structures (ISS serve with the working layer of mono-crystal substrate. Therefore in inverted epitaxy it is the problem of the development in the course of defects growth not in epitaxial layer, but in underlay, that becomes the major one. The processes of the development of defects in underlay in the course of growing thick (approximately 300 microns epitaxial layer are scarcely researched by now. Scientists sustained the idea that when using dislocation-free underlays for growing in the working layer of ISS there are dislocations with the density of 103 sm-2 and more. Thus, investigation of the factors that determine the development of dislocations in underlay in the process of epitaxy, has now gained great practical value.

  5. Epitaxial Garnets and Hexagonal Ferrites.

    Science.gov (United States)

    1982-04-20

    guide growth of the epitaxial YIG films. Aluminum or gallium substitu- tions for iron were used in combination with lanthanum substitutions for yttrium... gallate spinel sub- strates. There was no difficulty with nucleation in the melt and film quality appeared to be similar to that observed previously...hexagonal ferrites. We succeeded in growing the M-type lead hexaferrite (magnetoplumbite) on gallate spinel substrates. We found that the PbO-based

  6. Quantum Nanostructures by Droplet Epitaxy

    OpenAIRE

    Somsak Panyakeow

    2009-01-01

    Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C). Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic...

  7. Epitaxial rare-earth superlattices and films

    International Nuclear Information System (INIS)

    Salamon, M.B.; Beach, R.S.; Flynn, C.P.; Matheny, A.; Tsui, F.; Rhyne, J.J.

    1992-01-01

    This paper reports on epitaxial growth of rare-earth superlattices which is demonstrated to have opened important new areas of research on magnetic materials. The propagation magnetic order through non-magnetic elements, including its range and anisotropy, has been studied. The importance of magnetostriction in determining the phase diagram is demonstrated by the changes induced by epitaxial clamping. The cyrstallinity of epitaxial superlattices provides the opportunity to study interfacial magnetism by conventional x-ray and neutron scattering methods

  8. Epitaxial Al2O3 capacitors for low microwave loss superconducting quantum circuits

    Directory of Open Access Journals (Sweden)

    K.-H. Cho

    2013-10-01

    Full Text Available We have characterized the microwave loss of high-Q parallel plate capacitors fabricated from thin-film Al/Al2O3/Re heterostructures on (0001 Al2O3 substrates. The superconductor-insulator-superconductor trilayers were grown in situ in a hybrid deposition system: the epitaxial Re base and polycrystalline Al counterelectrode layers were grown by sputtering, while the epitaxial Al2O3 layer was grown by pulsed laser deposition. Structural analysis indicates a highly crystalline epitaxial Al2O3 layer and sharp interfaces. The measured intrinsic (low-power, low-temperature quality factor of the resonators is as high as 3 × 104. These results indicate that low-loss grown Al2O3 is an attractive candidate dielectric for high-fidelity superconducting qubit circuits.

  9. Adsorption-controlled growth of BiMnO3 films by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Lee, J. H.; Ke, X.; Misra, R.; Schiffer, P.; Ihlefeld, J. F.; Mei, Z. G.; Liu, Z. K.; Xu, X. S.; Musfeldt, J. L.; Heeg, T.; Schlom, D. G.; Roeckerath, M.; Schubert, J.

    2010-01-01

    We have developed the means to grow BiMnO 3 thin films with unparalleled structural perfection by reactive molecular-beam epitaxy and determined its band gap. Film growth occurs in an adsorption-controlled growth regime. Within this growth window bounded by oxygen pressure and substrate temperature at a fixed bismuth overpressure, single-phase films of the metastable perovskite BiMnO 3 may be grown by epitaxial stabilization. X-ray diffraction reveals phase-pure and epitaxial films with ω rocking curve full width at half maximum values as narrow as 11 arc sec (0.003 deg. ). Optical absorption measurements reveal that BiMnO 3 has a direct band gap of 1.1±0.1 eV.

  10. Epitaxial stabilization of ordered Pd–Fe structures on perovskite substrates

    Energy Technology Data Exchange (ETDEWEB)

    Harton, Renee M., E-mail: reneehar@umich.edu [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States); Stoica, Vladimir A. [Department of Materials Science and Engineering, Pennsylvania State University, 201 Old Main, University Park, PA 16802 (United States); Clarke, Roy [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States)

    2017-05-01

    We report the fabrication of epitaxial ferromagnetic Pd{sub 3}Fe thin films on SrTiO{sub 3}(001) substrates by promoting the interdiffusion of an Fe/Pd multilayer heterostructure using thermal annealing. Prior to annealing, the results of in-situ Reflection High-Energy Electron Diffraction characterization suggest that each Fe and Pd layer exhibited an in-plane epitaxial relationship with the SrTiO{sub 3}(001) substrate. X-Ray diffraction and magneto-optic Kerr effect characterization, conducted post-annealing, demonstrate that the film composition is majority Pd{sub 3}Fe and exhibits in-plane magnetization reversal with a moderate coercive field of ≈760 Oe. This demonstration of an ordered atomic layer heterostructure grown on a perovskite substrate suggests a route to epitaxial interfacial structures which can achieve strain-assisted magnetic switching.

  11. Magnetic anisotropy basis sets for epitaxial (110) and (111) REFe2 nanofilms

    International Nuclear Information System (INIS)

    Bowden, G J; Martin, K N; Fox, A; Rainford, B D; Groot, P A J de

    2008-01-01

    Magnetic anisotropy basis sets for the cubic Laves phase rare earth intermetallic REFe 2 compounds are discussed in some detail. Such compounds can be either free standing, or thin films grown in either (110) or (111) mode using molecular beam epitaxy. For the latter, it is useful to rotate to a new coordinate system where the z-axis coincides with the growth axes of the film. In this paper, three symmetry adapted basis sets are given, for multi-pole moments up to n = 12. These sets can be used for free-standing compounds and for (110) and (111) epitaxial films. In addition, the distortion of REFe 2 films, grown on sapphire substrates, is also considered. The distortions are different for the (110) and (111) films. Strain-induced harmonic sets are given for both specific and general distortions. Finally, some predictions are made concerning the preferred direction of easy magnetization in (111) molecular beam epitaxy grown REFe 2 films

  12. Bromine doping of CdTe and CdMnTe epitaxial layers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Waag, A. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Scholl, S. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Schierstedt, K. von (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Hommel, D. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Landwehr, G. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Bilger, G. (Zentrum fuer Sonnenenergie und Wasserstoff-Forschung, Stuttgart (Germany))

    1993-03-01

    We report on the n-type doping of CdTe and CdMnTe with bormine as a novel dopant material. /the thin films were grown by molecular beam epitaxy. ZnBr[sub 2] was used as a source material for the n-type doping. Free carrier concentrations at room temperature of up to 2.8x10[sup 18] cm[sup -3] could be readily obtained for both CdTe as well as CdMnTe thin films with Mn concentrations below 10%. This is to our knowledge the highest value ever obtained for the dilute magnetic semiconductor CdMnTe. For ZnBr[sub 2] source temperatures up to 60 C - corresponding to a free carrier concentration of (2-3)x10[sup 18] cm[sup -3] - the free carrier concentration of the epitaxial film increases with ZnBr[sub 2] source temperature. For higher ZnBr[sub 2] source temperatures compensation becomes dominant, which is indicated by a steep decrease of the free carrier concentration with increasing ZnBr[sub 2] source temperature. In addition the carrier mobility decreases drastically for such high dopant fluxes. A model of bromine incorporation is proposed. (orig.)

  13. Molecular beam epitaxy of Cd3As2 on a III-V substrate

    Directory of Open Access Journals (Sweden)

    Timo Schumann

    2016-12-01

    Full Text Available Epitaxial, strain-engineered Dirac semimetal heterostructures promise tuning of the unique properties of these materials. In this study, we investigate the growth of thin films of the recently discovered Dirac semimetal Cd3As2 by molecular beam epitaxy. We show that epitaxial Cd3As2 layers can be grown at low temperatures (110 °C–220 °C, in situ, on (111 GaSb buffer layers deposited on (111 GaAs substrates. The orientation relationship is described by ( 112 Cd 3 As 2 || (111 GaSb and [ 1 1 ¯ 0 ] Cd 3 As 2 || [ 1 ¯ 01 ] GaSb . The films are shown to grow in the low-temperature, vacancy ordered, tetragonal Dirac semimetal phase. They exhibit high room temperature mobilities of up to 19300 cm2/Vs, despite a three-dimensional surface morphology indicative of island growth and the presence of twin variants. The results indicate that epitaxial growth on more closely lattice matched buffer layers, such as InGaSb or InAlSb, which allow for imposing different degrees of epitaxial coherency strains, should be possible.

  14. Defect mediated van der Waals epitaxy of hexagonal boron nitride on graphene

    Science.gov (United States)

    Heilmann, M.; Bashouti, M.; Riechert, H.; Lopes, J. M. J.

    2018-04-01

    Van der Waals heterostructures comprising of hexagonal boron nitride and graphene are promising building blocks for novel two-dimensional devices such as atomically thin transistors or capacitors. However, demonstrators of those devices have been so far mostly fabricated by mechanical assembly, a non-scalable and time-consuming method, where transfer processes can contaminate the surfaces. Here, we investigate a direct growth process for the fabrication of insulating hexagonal boron nitride on high quality epitaxial graphene using plasma assisted molecular beam epitaxy. Samples were grown at varying temperatures and times and studied using atomic force microscopy, revealing a growth process limited by desorption at high temperatures. Nucleation was mostly commencing from morphological defects in epitaxial graphene, such as step edges or wrinkles. Raman spectroscopy combined with x-ray photoelectron measurements confirm the formation of hexagonal boron nitride and prove the resilience of graphene against the nitrogen plasma used during the growth process. The electrical properties and defects in the heterostructures were studied with high lateral resolution by tunneling current and Kelvin probe force measurements. This correlated approach revealed a nucleation apart from morphological defects in epitaxial graphene, which is mediated by point defects. The presented results help understanding the nucleation and growth behavior during van der Waals epitaxy of 2D materials, and point out a route for a scalable production of van der Waals heterostructures.

  15. 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.

  16. 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

  17. High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

    KAUST Repository

    Yang, Zhenqian; Deng, Yuhao; Zhang, Xiaowei; Wang, Suo; Chen, Huazhou; Yang, Sui; Khurgin, Jacob; Fang, Nicholas X.; Zhang, Xiang; Ma, Renmin

    2018-01-01

    The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial

  18. Epitaxial growth of CZT(S,Se) on silicon

    Science.gov (United States)

    Bojarczuk, Nestor A.; Gershon, Talia S.; Guha, Supratik; Shin, Byungha; Zhu, Yu

    2016-03-15

    Techniques for epitaxial growth of CZT(S,Se) materials on Si are provided. In one aspect, a method of forming an epitaxial kesterite material is provided which includes the steps of: selecting a Si substrate based on a crystallographic orientation of the Si substrate; forming an epitaxial oxide interlayer on the Si substrate to enhance wettability of the epitaxial kesterite material on the Si substrate, wherein the epitaxial oxide interlayer is formed from a material that is lattice-matched to Si; and forming the epitaxial kesterite material on a side of the epitaxial oxide interlayer opposite the Si substrate, wherein the epitaxial kesterite material includes Cu, Zn, Sn, and at least one of S and Se, and wherein a crystallographic orientation of the epitaxial kesterite material is based on the crystallographic orientation of the Si substrate. A method of forming an epitaxial kesterite-based photovoltaic device and an epitaxial kesterite-based device are also provided.

  19. Study on structural properties of epitaxial silicon films on annealed double layer porous silicon

    International Nuclear Information System (INIS)

    Yue Zhihao; Shen Honglie; Cai Hong; Lv Hongjie; Liu Bin

    2012-01-01

    In this paper, epitaxial silicon films were grown on annealed double layer porous silicon by LPCVD. The evolvement of the double layer porous silicon before and after thermal annealing was investigated by scanning electron microscope. X-ray diffraction and Raman spectroscopy were used to investigate the structural properties of the epitaxial silicon thin films grown at different temperature and different pressure. The results show that the surface of the low-porosity layer becomes smooth and there are just few silicon-bridges connecting the porous layer and the substrate wafer. The qualities of the epitaxial silicon thin films become better along with increasing deposition temperature. All of the Raman peaks of silicon films with different deposition pressure are situated at 521 cm -1 under the deposition temperature of 1100 °C, and the Raman intensity of the silicon film deposited at 100 Pa is much closer to that of the monocrystalline silicon wafer. The epitaxial silicon films are all (4 0 0)-oriented and (4 0 0) peak of silicon film deposited at 100 Pa is more symmetric.

  20. Epitaxial graphene electronic structure and transport

    International Nuclear Information System (INIS)

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun

    2010-01-01

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.