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Sample records for hfo2 films grown

  1. Correlation of nanochemistry and electrical properties in HfO2 films grown by metalorganic molecular-beam epitaxy

    Science.gov (United States)

    Moon, Tae-Hyoung; Ham, Moon-Ho; Myoung, Jae-Min

    2005-03-01

    We present the annealing effects on nanochemistry and electrical properties in HfO2 dielectrics grown by metalorganic molecular-beam epitaxy. After the postannealing treatment of HfO2 films in the temperature range of 600-800°C, the thicknesses and chemical states of the films were examined by high-resolution transmission electron microscopy and angle-resolved x-ray photoelectron spectroscopy. By comparing the line shapes of core-level spectra for the samples with different annealing temperatures, the concentrations of SiO and Hf-silicate with high dielectric constant are found to be highest for HfO2 film annealed at 700°C. This result supports that the accumulation capacitance of the sample annealed at 700°C is not deteriorated in spite of a steep increase in interfacial layer thickness compared with that of the sample annealed at 600°C.

  2. Effects of the oxygen precursor on the electrical and structural properties of HfO2 films grown by atomic layer deposition on Ge

    Science.gov (United States)

    Spiga, S.; Wiemer, C.; Tallarida, G.; Scarel, G.; Ferrari, S.; Seguini, G.; Fanciulli, M.

    2005-09-01

    We report on the growth by atomic layer deposition of HfO2 films on HF-last treated Ge(001) substrates using HfCl4 as a Hf source and either O3 or H2O as oxygen sources. The choice of the oxygen precursor strongly influences the structural, chemical, and electrical properties of the HfO2 films: Those grown using H2O exhibit local epitaxial growth, a large amount of contaminants such as chlorine and carbon, and a large frequency dispersion of the capacitance-voltage (C -V) characteristics. Films grown using O3 are good insulators and exhibit well-shaped C -V curves with a minimum frequency dispersion of the accumulation capacitance. Moreover, they are smoother, less crystallized, and with a lower contaminant content than those grown using H2O. However, the use of O3 leads to the formation of a 2nm thick layer, possibly GeOx, at the HfO2/Ge interface.

  3. Epitaxial Thin Films of Y doped HfO2

    Science.gov (United States)

    Serrao, Claudy; Khan, Asif; Ramamoorthy, Ramesh; Salahuddin, Sayeef

    Hafnium oxide (HfO2) is one of a few metal oxides that is thermodynamically stable on silicon and silicon oxide. There has been renewed interest in HfO2 due to the recent discovery of ferroelectricity and antiferroelectricity in doped HfO2. Typical ferroelectrics - such as strontium bismuth tantalate (SBT) and lead zirconium titanate (PZT) - contain elements that easily react with silicon and silicon oxide at elevated temperatures; therefore, such ferroelectrics are not suited for device applications. Meanwhile, ferroelectric HfO2 offers promise regarding integration with silicon. The stable phase of HfO2 at room temperature is monoclinic, but HfO2 can be stabilized in the tetragonal, orthorhombic or even cubic phase by suitable doping. We stabilized Y-doped HfO2 thin films using pulsed laser deposition. The strain state can be controlled using various perovskite substrates and controlled growth conditions. We report on Y-doped HfO2 domain structures from piezo-response force microscopy (PFM) and structural parameters via X-ray reciprocal space maps (RSM). We hope this work spurs further interest in strain-tuned ferroelectricity in doped HfO2.

  4. Crystal structure and band gap determination of HfO2 thin films

    NARCIS (Netherlands)

    Cheynet, M.C.; Pokrant, S.; Tichelaar, F.D.; Rouvière, J.L.

    2007-01-01

    Valence electron energy loss spectroscopy (VEELS) and high resolution transmission electron microscopy (HRTEM) are performed on three different HfO2 thin films grown on Si (001) by chemical vapor deposition (CVD) or atomic layer deposition (ALD). For each sample the band gap (Eg) is determined by

  5. Growth of epitaxial orthorhombic YO1.5-substituted HfO2 thin film

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    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Funakubo, Hiroshi

    2015-07-01

    YO1.5-substituted HfO2 thin films with various substitution amounts were grown on (100) YSZ substrates by the pulsed laser deposition method directly from the vapor phase. The epitaxial growth of film with different YO1.5 amounts was confirmed by the X-ray diffraction method. Wide-area reciprocal lattice mapping measurements were performed to clarify the crystal symmetry of films. The formed phases changed from low-symmetry monoclinic baddeleyite to high-symmetry tetragonal/cubic fluorite phases through an orthorhombic phase as the YO1.5 amount increased from 0 to 0.15. The additional annular bright-field scanning transmission electron microscopy indicates that the orthorhombic phase has polar structure. This means that the direct growth by vapor is of polar orthorhombic HfO2-based film. Moreover, high-temperature X-ray diffraction measurements showed that the film with a YO1.5 amount of 0.07 with orthorhombic structure at room temperature only exhibited a structural phase transition to tetragonal phase above 450 °C. This temperature is much higher than the reported maximum temperature of 200 °C to obtain ferroelectricity as well as the expected temperature for real device application. The growth of epitaxial orthorhombic HfO2-based film helps clarify the nature of ferroelectricity in HfO2-based films (186 words/200 words).

  6. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    OpenAIRE

    Takao Shimizu; Kiliha Katayama; Takanori Kiguchi; Akihiro Akama; Konno, Toyohiko J.; Osami Sakata; Hiroshi Funakubo

    2016-01-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16...

  7. Pulsed laser deposition of HfO2 thin films on indium zinc oxide: Band offsets measurements

    Science.gov (United States)

    Craciun, D.; Craciun, V.

    2017-04-01

    One of the most used dielectric films for amorphous indium zinc oxide (IZO) based thin films transistor is HfO2. The estimation of the valence band discontinuity (ΔEV) of HfO2/IZO heterostructure grown using the pulsed laser deposition technique, with In/(In + Zn) = 0.79, was obtained from X-ray photoelectron spectroscopy (XPS) measurements. The binding energies of Hf 4d5, Zn 2p3 and In 3d5 core levels and valence band maxima were measured for thick pure films and for a very thin HfO2 film deposited on a thick IZO film. A value of ΔEV = 1.75 ± 0.05 eV was estimated for the heterostructure. Taking into account the measured HfO2 and IZO optical bandgap values of 5.50 eV and 3.10 eV, respectively, a conduction band offset ΔEC = 0.65 ± 0.05 eV in HfO2/IZO heterostructure was then obtained.

  8. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO2-based thin films

    Science.gov (United States)

    Katayama, Kiliha; Shimizu, Takao; Sakata, Osami; Shiraishi, Takahisa; Nakamura, Shogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Uchida, Hiroshi; Funakubo, Hiroshi

    2016-04-01

    Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO1.5-0.93HfO2 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 HfO2-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)O3 and BiFeO3.

  9. Structural degradation of thin HfO2 film on Ge during the postdeposition annealing

    Science.gov (United States)

    Miyata, Noriyuki; Yasuda, Tetsuji; Abe, Yasuhiro

    2010-05-01

    Securing the thermal robustness of thin hafnium oxide (HfO2) film on the semiconductor surface is an important technical issue in the fabrication of the metal-oxide-semiconductor field-effect transistor devices, as the HfO2-based high-k gate stacks usually undergo high-temperature processes. In this study, the structural development of thin HfO2 film on a Ge surface during postdeposition annealing in an ultrahigh vacuum was examined to explore the origin for the initial degradation of thin HfO2 film. Void nucleation and subsequent two-dimensional void growth take place at 780-840 °C, while the chemical composition of the remaining Hf oxide is virtually stable. Both the void nucleation and growth processes show similar larger activation energy of about 10 eV. Based on the observed manner of void growth and the estimated activation energies, the authors propose that mass transport on the HfO2 surface is responsible for void nucleation in the HfO2 films on Ge. The authors also compare the present results with the previous studies on HfO2/Si structures, and suggest that similar surface process leads to the local Hf silicidation.

  10. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    Science.gov (United States)

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-09-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.

  11. III-Nitride grating grown on freestanding HfO2 gratings

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    Wu Tong

    2011-01-01

    Full Text Available Abstract We report here the epitaxial growth of III-nitride material on freestanding HfO2 gratings by molecular beam epitaxy. Freestanding HfO2 gratings are fabricated by combining film evaporation, electron beam lithography, and fast atom beam etching of an HfO2 film by a front-side silicon process. The 60-μm long HfO2 grating beam can sustain the stress change during the epitaxial growth of a III-nitride material. Grating structures locally change the growth condition and vary indium composition in the InGaN/GaN quantum wells and thus, the photoluminescence spectra of epitaxial III-nitride grating are tuned. Guided mode resonances are experimentally demonstrated in fabricated III-nitride gratings, opening the possibility to achieve the interaction between the excited light and the grating structure through guided mode resonance. PACS: 78.55.Cr; 81.65.Cf; 81.15.Hi.

  12. Growth and properties of hafnicone and HfO(2)/hafnicone nanolaminate and alloy films using molecular layer deposition techniques.

    Science.gov (United States)

    Lee, Byoung H; Anderson, Virginia R; George, Steven M

    2014-10-08

    Molecular layer deposition (MLD) of the hafnium alkoxide polymer known as "hafnicone" was grown using sequential exposures of tetrakis(dimethylamido) hafnium (TDMAH) and ethylene glycol (EG) as the reactants. In situ quartz crystal microbalance (QCM) experiments demonstrated self-limiting reactions and linear growth versus the number of TDMAH/EG reaction cycles. Ex situ X-ray reflectivity (XRR) analysis confirmed linear growth and measured the density of the hafnicone films. The hafnicone growth rates were temperature-dependent and decreased from 1.2 Å per cycle at 105 °C to 0.4 Å per cycle at 205 °C. The measured density was ∼3.0 g/cm(3) for the hafnicone films at all temperatures. Transmission electron microscopy images revealed very uniform and conformal hafnicone films. The XRR studies also showed that the hafnicone films were very stable with time. Nanoindentation measurements determined that the elastic modulus and hardness of the hafnicone films were 47 ± 2 and 2.6 ± 0.2 GPa, respectively. HfO2/hafnicone nanolaminate films also were fabricated using HfO2 atomic layer deposition (ALD) and hafnicone MLD at 145 °C. The in situ QCM measurements revealed that HfO2 ALD nucleation on the hafnicone MLD surface required at least 18 TDMAH/H2O cycles. Hafnicone alloys were also fabricated by combining HfO2 ALD and hafnicone MLD at 145 °C. The composition of the hafnicone alloy was varied by adjusting the relative number of TDMAH/H2O ALD cycles and TDMAH/EG MLD cycles in the reaction sequence. The electron density changed continuously from 8.2 × 10(23) e(-)/cm(3) for pure hafnicone MLD films to 2.4 × 10(24) e(-)/cm(3) for pure HfO2 ALD films. These hafnicone films and the HfO2/hafnicone nanolaminates and alloys may be useful for flexible thin-film devices.

  13. Mixed Al and Si doping in ferroelectric HfO2 thin films

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    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Chung, Ching-Chang; Moghaddam, Saeed; Jones, Jacob L.; Nishida, Toshikazu

    2015-12-01

    Ferroelectric HfO2 thin films 10 nm thick are simultaneously doped with Al and Si. The arrangement of the Al and Si dopant layers within the HfO2 greatly influences the resulting ferroelectric properties of the polycrystalline thin films. Optimizing the order of the Si and Al dopant layers led to a remanent polarization of ˜20 μC/cm2 and a coercive field strength of ˜1.2 MV/cm. Post-metallization anneal temperatures from 700 °C to 900 °C were used to crystallize the Al and Si doped HfO2 thin films. Grazing incidence x-ray diffraction detected differences in peak broadening between the mixed Al and Si doped HfO2 thin films, indicating that strain may influence the formation of the ferroelectric phase with variations in the dopant layering. Endurance characteristics show that the mixed Al and Si doped HfO2 thin films exhibit a remanent polarization greater than 15 μC/cm2 up to 108 cycles.

  14. On the structural origins of ferroelectricity in HfO2 thin films

    Science.gov (United States)

    Sang, Xiahan; Grimley, Everett D.; Schenk, Tony; Schroeder, Uwe; LeBeau, James M.

    2015-04-01

    Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO2 thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO2 thin films.

  15. Influences of Annealing on Residual Stress and Structure of HfO2 Films

    Institute of Scientific and Technical Information of China (English)

    SHEN Yan-Ming; SHAO Shu-Ying; DENG Zhen-Xia; HE Hong-Bo; SHAO Jian-Da; FAN Zheng-Xiu

    2007-01-01

    HfO2 films are deposited on BK7 glass substrates by electron beam evaporation. The influences of annealing between 100℃ and 400℃ on residual stresses and structures of HfO2 films are studied. It is found that little differences of spectra, residual stresses and structures are obtained after annealing at lower temperatures. After annealing at higher temperatures, the spectra shift to short wavelength, the residual stress increases with the increasing annealing temperature. At the same time, the crystallite size increases and interplanar distance decreases. The variations of optical spectra and residual stress correspond to the evolutions of structures induced by annealing.

  16. Silicon surface passivation using thin HfO2 films by atomic layer deposition

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    Gope, Jhuma; Vandana; Batra, Neha; Panigrahi, Jagannath; Singh, Rajbir; Maurya, K. K.; Srivastava, Ritu; Singh, P. K.

    2015-12-01

    Hafnium oxide (HfO2) is a potential material for equivalent oxide thickness (EOT) scaling in microelectronics; however, its surface passivation properties particularly on silicon are not well explored. This paper reports investigation on passivation properties of thermally deposited thin HfO2 films by atomic layer deposition system (ALD) on silicon surface. As-deposited pristine film (∼8 nm) shows better passivation with <100 cm/s surface recombination velocity (SRV) vis-à-vis thicker films. Further improvement in passivation quality is achieved with annealing at 400 °C for 10 min where the SRV reduces to ∼20 cm/s. Conductance measurements show that the interface defect density (Dit) increases with film thickness whereas its value decreases after annealing. XRR data corroborate with the observations made by FTIR and SRV data.

  17. Ferroelectricity and antiferroelectricity of doped thin HfO2-based films.

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    Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Kim, Yu Jin; Moon, Taehwan; Kim, Keum Do; Müller, Johannes; Kersch, Alfred; Schroeder, Uwe; Mikolajick, Thomas; Hwang, Cheol Seong

    2015-03-18

    The recent progress in ferroelectricity and antiferroelectricity in HfO2-based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non-volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si-compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si-doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro-electricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm(-2), and their coercive field (≈1-2 MV cm(-1)) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field-effect-transistors and three-dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid-state-cooling, and infrared sensors.

  18. The effects of layering in ferroelectric Si-doped HfO2 thin films

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    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Liu, Yang; Fancher, Chris M.; Jones, Jacob L.; Moghaddam, Saeed; Nishida, Toshikazu

    2014-08-01

    Atomic layer deposited Si-doped HfO2 thin films approximately 10 nm thick are deposited with various Si-dopant concentrations and distributions. The ferroelectric behavior of the HfO2 thin films are shown to be dependent on both the Si mol. % and the distribution of Si-dopants. Metal-ferroelectric-insulator-semiconductor capacitors are shown to exhibit a tunable remanent polarization through the adjustment of the Si-dopant distribution at a constant Si concentration. Inhomogeneous layering of Si-dopants within the thin films effectively lowers the remanent polarization. A pinched hysteresis loop is observed for higher Si-dopant concentrations and found to be dependent on the Si layering distribution.

  19. Ferroelectricity of nondoped thin HfO2 films in TiN/HfO2/TiN stacks

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    Nishimura, Tomonori; Xu, Lun; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2016-08-01

    We report on the impact of TiN interfaces on the ferroelectricity of nondoped HfO2. Ferroelectric properties of nondoped HfO2 in TiN/HfO2/TiN stacks are shown in capacitance-voltage and polarization-voltage characteristics. The Curie temperature is also estimated to be around 500 °C. The ferroelectricity of nondoped HfO2 clearly appears by thinning HfO2 film down to ˜35 nm. We directly revealed in thermal treatments that the ferroelectric HfO2 film on TiN was maintained by covering the top surface of HfO2 with TiN, while it was followed by a phase transition to the paraelectric phase in the case of the open surface of HfO2. Thus, it is concluded that the ferroelectricity in nondoped HfO2 in this study was mainly driven by both of top and bottom TiN interfaces.

  20. Study on absorbance and laser damage threshold of HfO2 films prepared by ion-assisted reaction deposition

    Institute of Scientific and Technical Information of China (English)

    Dawei Zhang(张大伟); Shuhai Fan(范树海); Weidong Gao(高卫东); Hongbo He(贺洪波); Yingjian Wang(王英剑); Jianda Shao(邵建达); Zhengxiu Fan(范正修); Haojie Sun(孙浩杰)

    2004-01-01

    Using a new kind of EH1000 ion source, hafnium dioxide (HfO2) films are deposited with different deposition techniques and different conditions. The absorbance and the laser damage threshold of these films have been measured and studied. By comparing these characteristics, one can conclude that under right conditions, such as high partial pressure of oxygen and right kind of ion source, the ion-assisted reaction deposition can prepare HfO2 films with higher laser induced damage threshold.

  1. TaN interface properties and electric field cycling effects on ferroelectric Si-doped HfO2 thin films

    Science.gov (United States)

    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Fancher, Chris M.; Lambers, Eric; Rudawski, Nicholas G.; Jones, Jacob L.; Moghaddam, Saeed; Nishida, Toshikazu

    2015-04-01

    Ferroelectric HfO2-based thin films, which can exhibit ferroelectric properties down to sub-10 nm thicknesses, are a promising candidate for emerging high density memory technologies. As the ferroelectric thickness continues to shrink, the electrode-ferroelectric interface properties play an increasingly important role. We investigate the TaN interface properties on 10 nm thick Si-doped HfO2 thin films fabricated in a TaN metal-ferroelectric-metal stack which exhibit highly asymmetric ferroelectric characteristics. To understand the asymmetric behavior of the ferroelectric characteristics of the Si-doped HfO2 thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-O bonds at the bottom electrode interface and a significant presence of Hf-N bonds at both electrode interfaces are identified. It is shown that the chemical heterogeneity of the bottom and top electrode interfaces gives rise to an internal electric field, which causes the as-grown ferroelectric domains to preferentially polarize to screen positively charged oxygen vacancies aggregated at the oxidized bottom electrode interface. Electric field cycling is shown to reduce the internal electric field with a concomitant increase in remanent polarization and decrease in relative permittivity. Through an analysis of pulsed transient switching currents, back-switching is observed in Si-doped HfO2 thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.

  2. Nanoscale morphological and electrical homogeneity of HfO2 and ZrO2 thin films studied by conducting atomic-force microscopy

    Science.gov (United States)

    Kremmer, S.; Wurmbauer, H.; Teichert, C.; Tallarida, G.; Spiga, S.; Wiemer, C.; Fanciulli, M.

    2005-04-01

    The morphological and electrical evolution of HfO2 and ZrO2 thin films is investigated on the nanoscale using conducting atomic-force microscopy in ultrahigh vacuum. Films of different thicknesses have been grown by atomic layer deposition. With increasing film thickness the film structure changes from amorphous to polycrystalline. By conducting atomic-force microscopy using local current-voltage curve statistics and two-dimensional current imaging it is found that the formation of crystallites has different effects on the electrical properties of the two dielectrics. In the case of HfO2, the crystalline fraction causes weak spots in the oxide, whereas for the ZrO2 films the crystallites exhibit lower leakage currents compared to the amorphous matrix and leakage is mainly determined by thickness fluctuations.

  3. Formation of Al2O3-HfO2 Eutectic EBC Film on Silicon Carbide Substrate

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    Kyosuke Seya

    2015-01-01

    Full Text Available The formation mechanism of Al2O3-HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3-HfO2 eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all of HfO2 phase is reduced to HfC phase, HfC-HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.

  4. Influence of different oxidants on the band alignment of HfO2 films deposited by atomic layer deposition

    Institute of Scientific and Technical Information of China (English)

    Fan Ji-Bin; Liu Hong-Xia; Gao Bo; Ma Fei; Zhuo Qing-Qing; Hao Yue

    2012-01-01

    Based on X-ray photoelectron spectroscopy (XPS),influences of different oxidants on band alignment of HfO2 films deposited by atomic layer deposition (ALD) are investigated in this paper.The measured valence band offset (VBO) value for H2O-based HfO2 increases from 3.17 eV to 3.32 eV after annealing,whereas the VBO value for O3-based HfO2 decreases from 3.57 eV to 3.46 eV.The research results indicate that the silicate layer changes in different ways for H2O-based and O3-based HfO2 films after the annealing process,which plays a key role in generating the internal electric field formed by the dipoles.The variations of the dipoles at the interface between the HfO2 and SiO2 after annealing may lead the VBO values of H2O-based and O3-based HfO2 to vary in different ways,which fits with the variation of fiat band (VFB) voltage.

  5. Study on absorbance and laser damage threshold of HfO2 films prepared by ion-assisted reaction deposition

    Institute of Scientific and Technical Information of China (English)

    张大伟; 范树海; 高卫东; 贺洪波; 王英剑; 邵建达; 范正修; 孙浩杰

    2004-01-01

    Using a new kind of EH1000 ion source, hafnium dioxide (HfO2) films are deposited with different depo sition techniques and different conditions. The absorbance and the laser damage threshold of these films have been measured and studied. By comparing these characteristics, one can conclude that under right conditions, such as high partial pressure of oxygen and right kind of ion source, the ion-assisted reaction deposition can prepare HfO2 films with higher laser induced damage threshold.

  6. The effect of Gd doping on the atomic and electronic structure of HfO2 thin films.

    Science.gov (United States)

    Ketsman, Ihor; Sokolov, Andrei; Belashchenko, Kirill; Dowben, Peter; Losovyj, Yaroslav; Tang, Jinke; Wang, Zhenjun

    2008-03-01

    HfO2 is a promising oxide for many applications, including high-k gate dielectric for CMOS devices. In addition, Gd-doped HfO2 could lead to a dilute magnetic semiconductor and provide an efficient neutron detection medium due to huge neutron absorption cross section of Gd. Gd-doped HfO2 films deposited on both p-type and n-type silicon by PLD retain monoclinic phase at small doping levels, but can be stabilized in fluorite phase by increased doping [1]. At small doping levels, photoemission measurements indicate n-type character of the films as a result of overcompensation with oxygen vacancies. Depending on a doping level, the films form heterojunctions with good rectifying properties on n- or p-type silicon. Preliminary results show the potential ability of the formed diode structures to detect neutrons. [1] Ya.B.Losovyj, I.Ketsman et al.,APL, 91, 132908, (2007)

  7. Temperature Effects on a-IGZO Thin Film Transistors Using HfO2 Gate Dielectric Material

    Directory of Open Access Journals (Sweden)

    Yu-Hsien Lin

    2014-01-01

    Full Text Available This study investigated the temperature effect on amorphous indium gallium zinc oxide (a-IGZO thin film transistors (TFTs using hafnium oxide (HfO2 gate dielectric material. HfO2 is an attractive candidate as a high-κ dielectric material for gate oxide because it has great potential to exhibit superior electrical properties with a high drive current. In the process of integrating the gate dielectric and IGZO thin film, postannealing treatment is an essential process for completing the chemical reaction of the IGZO thin film and enhancing the gate oxide quality to adjust the electrical characteristics of the TFTs. However, the hafnium atom diffused the IGZO thin film, causing interface roughness because of the stability of the HfO2 dielectric thin film during high-temperature annealing. In this study, the annealing temperature was optimized at 200°C for a HfO2 gate dielectric TFT exhibiting high mobility, a high ION/IOFF ratio, low IOFF current, and excellent subthreshold swing (SS.

  8. Evidence of GeO volatilization and its effect on the characteristics of HfO2 grown on a Ge substrate

    Institute of Scientific and Technical Information of China (English)

    Fan Ji-Bin; Liu Hong-Xia; Fei Cheng-Xi; Ma Fei; Fan Xiao-Jiao; Hao Yue

    2013-01-01

    HfO2 films are deposited by atomic layer deposition (ALD) using tetrakis ethylmethylamino hafnium (TEMAH) as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500 ℃ in nitrogen,the thickness of Ge oxide's interfacial layer decreases,and the presence of GeO is observed at the H2O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2O molecules in H2O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2/Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy (XPS) and electrical measurements.

  9. Effect of growth rate on crystallization of HfO2 thin films deposited by RF magnetron sputtering

    Science.gov (United States)

    Dhanunjaya, M.; Manikanthababu, N.; Pathak, A. P.; Rao, S. V. S. Nageswara

    2016-05-01

    Hafnium oxide (HfO2) is the potentially useful dielectric material in both; electronics to replace the conventional SiO2 as gate dielectric and in Optics as anti-reflection coating material. In this present work we have synthesized polycrystalline HfO2 thin films by RF magnetron sputtering deposition technique with varying target to substrate distance. The deposited films were characterized by X-ray Diffraction, Rutherford Backscattering Spectrometry (RBS) and transmission and Reflection (T&R) measurements to study the growth behavior, microstructure and optical properties. XRD measurement shows that the samples having mixed phase of monoclinic, cubic and tetragonal crystal structure. RBS measurements suggest the formation of Inter Layer (IL) in between Substrate and film

  10. The impact of ultrathin Al2O3 films on the electrical response of p-Ge/Al2O3/HfO2/Au MOS structures

    Science.gov (United States)

    Botzakaki, M. A.; Skoulatakis, G.; Kennou, S.; Ladas, S.; Tsamis, C.; Georga, S. N.; Krontiras, C. A.

    2016-09-01

    It is well known that the most critical issue in Ge CMOS technology is the successful growth of high-k gate dielectrics on Ge substrates. The high interface quality of Ge/high-k dielectric is connected with advanced electrical responses of Ge based MOS devices. Following this trend, atomic layer deposition deposited ultrathin Al2O3 and HfO2 films were grown on p-Ge. Al2O3 acts as a passivation layer between p-Ge and high-k HfO2 films. An extensive set of p-Ge/Al2O3/HfO2 structures were fabricated with Al2O3 thickness ranging from 0.5 nm to 1.5 nm and HfO2 thickness varying from 2.0 nm to 3.0 nm. All structures were characterized by x-ray photoelectron spectroscopy (XPS) and AFM. XPS analysis revealed the stoichiometric growth of both films in the absence of Ge sub-oxides between p-Ge and Al2O3 films. AFM analysis revealed the growth of smooth and cohesive films, which exhibited minimal roughness (~0.2 nm) comparable to that of clean bare p-Ge surfaces. The electrical response of all structures was analyzed by C-V, G-V, C-f, G-f and J-V characteristics, from 80 K to 300 K. It is found that the incorporation of ultrathin Al2O3 passivation layers between p-Ge and HfO2 films leads to superior electrical responses of the structures. All structures exhibit well defined C-V curves with parasitic effects, gradually diminishing and becoming absent below 170 K. D it values were calculated at each temperature, using both Hill-Coleman and Conductance methods. Structures of p-Ge/0.5 nm Al2O3/2.0 nm HfO2/Au, with an equivalent oxide thickness (EOT) equal to 1.3 nm, exhibit D it values as low as ~7.4  ×  1010 eV-1 cm-2. To our knowledge, these values are among the lowest reported. J-V measurements reveal leakage currents in the order of 10-1 A cm-2, which are comparable to previously published results for structures with the same EOT. A complete mapping of the energy distribution of D its into the energy bandgap of p-Ge, from the valence band

  11. SHI induced effects on the electrical and optical properties of HfO2 thin films deposited by RF sputtering

    Science.gov (United States)

    Manikanthababu, N.; Dhanunjaya, M.; Nageswara Rao, S. V. S.; Pathak, A. P.

    2016-07-01

    The continuous downscaling of Metal Oxide Semiconductor (MOS) devices has reached a limit with SiO2 as a gate dielectric material. Introducing high-k dielectric materials as a replacement for the conservative SiO2 is the only alternative to reduce the leakage current. HfO2 is a reliable and an impending material for the wide usage as a gate dielectric in semiconductor industry. HfO2 thin films were synthesized by RF sputtering technique. Here, we present a study of Swift Heavy Ion (SHI) irradiation with100 MeV Ag ions for studying the optical properties as well as 80 MeV Ni ions for studying the electrical properties of HfO2/Si thin films. Rutherford Backscattering Spectrometry (RBS), Field Emission Scanning Electron Microscope (FESEM), energy-dispersive X-ray spectroscopy (EDS), profilometer and I-V (leakage current) measurements have been employed to study the SHI induced effects on both the structural, electrical and optical properties.

  12. Effects of biased irradiation on charge trapping in HfO2 dielectric thin films

    Science.gov (United States)

    Mu, Yifei; Zhao, Ce Zhou; Lu, Qifeng; Zhao, Chun; Qi, Yanfei; Lam, Sang; Mitrovic, Ivona Z.; Taylor, Stephen; Chalker, Paul R.

    2017-09-01

    This paper reports the low-dose-rate radiation response of Al-HfO2/SiO2-Si MOS devices, in which the gate dielectric was formed by atomic layer deposition (ALD) with 5-nm equivalent oxide thickness. The degradation of the devices was characterized by a pulse capacitance-voltage (CV) and on-site radiation response technique under continuous gamma (γ) ray exposure at a relatively low dose rate of 0.116 rad (HfO2)/s. Compared with conventional CV measurements, the proposed measurements extract significant variations of flat-band voltage shift of the hafnium based MOS devices. The large flat-band voltage shift is mainly attributed to the radiation-induced oxide trapped charges, which are not readily compensated by bias-induced charges produced over the measurement timescales (for timescales less than 5 ms). A negative flat-band voltage shift up to -1.02 V was observed under a positive biased irradiation with the total dose up to 40 krad (HfO2) and with the electric field of 0.5 MV/cm. This is attributed to net positive charge generation in the HfO2 oxide layer. The generated charges are transported towards the HfO2/SiO2 interface, and then form effective trapped holes in the HfO2. Similarly, a positive flat-band voltage shift up to 1.1 V was observed from irradiation under negative bias with an electric field of -0.5 MV/cm. The positive shift is mainly due to the accumulation of trapped electrons. Analyses of the experimental results suggest that both hole and electron trapping can dominate the radiation response performance of the HfO2-based MOS devices depending upon the applied bias. It was also found there was no distinct border traps with irradiation in all cases.

  13. Hetero-epitaxial growth of the cubic single crystalline HfO 2 film as high k materials by pulsed laser ablation

    Science.gov (United States)

    Zhang, Xinqiang; Tu, Hailing; Wang, Xiaona; Xiong, Yuhua; Yang, Mengmeng; Wang, Lei; Du, Jun

    2010-10-01

    We report a hetero-epitaxial growth of cubic single crystalline HfO 2 film on Si substrates as high k materials by pulse laser ablation (PLA) at 820 °C. To eliminate the interfacial defects, the HfO 2 film has then been annealed at 900 °C for 5 min in N 2. Reflection high-energy electron diffraction (RHEED) results indicate orientation of the HfO 2 film on Si substrates corresponding to (∥( and [∥[. An interface layer has been revealed by high-resolution transmission electron microscope (HRTEM). Through capacitance-voltage ( C- V) and current-voltage ( I- V), it has been obtained that the leakage current of the HfO 2 gate insulator with dielectric constant of 26 is 5×10 -6 A/cm 2 at -1 V.

  14. Photo-, cathodo- and thermoluminescent properties of dysprosium-doped HfO2 films deposited by ultrasonic spray pyrolysis.

    Science.gov (United States)

    Manríquez, R Reynoso; Góngora, J A I Díaz; Guzmán-Mendoza, J; Montalvo, T Rivera; Olguín, J C Guzmán; Ramírez, P V Cerón; García-Hipólito, M; Falcony, C

    2014-09-01

    In this work, the photoluminescent (PL), cathodoluminescent (CL) and thermoluminescent (TL) properties of hafnium oxide films doped with trivalent dysprosium ions are reported. The films were deposited on glass substrates at temperatures ranging from 300 to 600°C, using chlorides as precursor reagents. The surface morphology of films showed a veins shaped microstructure at low deposition temperatures, while at higher temperatures the formation of spherical particles was observed on the surface. X-ray diffraction showed the presence of HfO2 monoclinic phase in the films deposited at temperatures greater than 400°C. The PL and CL spectra of the doped films showed the highest emission band centered at 575nm corresponding to the transitions (4)F9/2→(6)H13/2, which is a characteristic transition of Dy(3+) ion. The greatest emission intensities were observed in samples doped with 1 atomic percent (at%) of DyCl3 in the precursor solution. Regarding the TL behavior, the glow curve of HfO2:Dy(+3) films exhibited spectrum with one broad band centered at about 150°C. The highest intensity TL response was observed on the films deposited at 500°C. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Hafnium carbamates and ureates: new class of precursors for low-temperature growth of HfO2 thin films.

    Science.gov (United States)

    Pothiraja, Ramasamy; Milanov, Andrian P; Barreca, Davide; Gasparotto, Alberto; Becker, Hans-Werner; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-04-21

    Novel volatile compounds of hafnium, namely tetrakis-N,O-dialkylcarbamato hafnium(iv) [Hf((i)PrNC(O)O(i)Pr)(4)] () and tetrakis-N,N,N'-trialkylureato hafnium(iv) [Hf((i)PrNC(O)N-(Me)Et)(4)] (), have been synthesized through the simple insertion reaction of isopropyl isocyanate into hafnium isopropoxide and hafnium ethylmethylamide, respectively; based on the promising thermal properties, compound has been evaluated as a precursor for metalorganic chemical vapor deposition (MOCVD) of HfO(2) thin films, which resulted in the growth of stoichiometric and crystalline layers with a uniform morphology at temperature as low as 250 degrees C.

  16. Epitaxial growth and characterization of Gd2O3-doped HfO2 film on Ge (001) substrates with zero interface layer

    Institute of Scientific and Technical Information of China (English)

    张心强; 屠海令; 魏峰; 熊玉华; 杨萌萌; 赵洪滨; 杜军; 王文武

    2013-01-01

    The GHO (Gd2O3-doped HfO2) films were epitaxially grown on Ge (001) substrates adopting cube-on-cube mode with zero interface layer using pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) and high-resolution transmission electron microscopy (HRTEM) observation revealed a sharp interface of GHO/Ge and orientation relationship corre-sponding to (001)GHO//(001)Ge and [011] GHO//[011]Ge. The band offset for GHO/Ge stack was evaluated to be 3.92 eV for va-lence band and 1.38 eV for conduction band by X-ray photoelectron spectrum. Small equivalent oxide thickness (0.49 nm) and inter-face state density (7×1011 cm-2) were achieved from Au/Ti/GHO/Ge/Al capacitors.

  17. Interfacial reaction and electrical properties of HfO2 film gate dielectric prepared by pulsed laser deposition in nitrogen: role of rapid thermal annealing and gate electrode.

    Science.gov (United States)

    Wang, Yi; Wang, Hao; Ye, Cong; Zhang, Jun; Wang, Hanbin; Jiang, Yong

    2011-10-01

    The high-k dielectric HfO(2) thin films were deposited by pulsed laser deposition in nitrogen atmosphere. Rapid thermal annealing effect on film surface roughness, structure and electrical properties of HfO(2) film was investigated. The mechanism of interfacial reaction and the annealing atmosphere effect on the interfacial layer thickness were discussed. The sample annealed in nitrogen shows an amorphous dominated structure and the lowest leakage current density. Capacitors with high-k HfO(2) film as gate dielectric were fabricated, using Pt, Au, and Ti as the top gate electrode whereas Pt constitutes the bottom side electrode. At the gate injection case, the Pt- and Au-gated metal oxide semiconductor devices present a lower leakage current than that of the Ti-gated device, as well as similar leakage current conduction mechanism and interfacial properties at the metal/HfO(2) interface, because of their close work function and chemical properties.

  18. Impact of lanthanum on the modification of HfO2 films structure

    Institute of Scientific and Technical Information of China (English)

    T. P. Smirnova; L.V. Yakovkina; V.O. Borisov

    2015-01-01

    LaxHf1–xOy thin films with various concentrations of La, homogeneous and nonhomogeneous distributions of elements throughout the films thickness was purposefully grown by CVD. The composition of the films and their chemical structures were characterized throughout the films thickness by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDXA). A full picture of the film crystallinity was provided by the combination of grazing incidence X-ray diffraction (GIXRD) synchrotron radiation (SR) and high resolution transmission electron microscopy (HR TEM). It was shown that La acted as “molar volume modulator” and stabilized the nonequilibrium atT≤1300 °C cubic phases. The samples with La content in range of 7 at.%films microstructure was revealed.

  19. HfO2/porous anodic alumina composite films for multifunctional data storage media materials under electric field control

    Science.gov (United States)

    Qi, Li-Qian; Pan, Di-Ya; Li, Jun-Qing; Liu, Li-Hu; Sun, Hui-Yuan

    2017-03-01

    New materials for achieving direct electric field control of ferromagnetism and resistance behavior are highly desirable in the development of multifunctional data storage devices. In this paper, HfO2 nanoporous films have been fabricated on porous anodic alumina (PAA) substrates by DC-reactive magnetron sputtering. Electrically induced resistive switching (RS) and modulated room temperature ferromagnetism are simultaneously found in a Ag/HfO2/PAA/Al (Ag/HP/Al) heterostructure. The switching mechanism between low resistance state and high resistance state is generally attributed to the formation/rupture of conductive filaments which may consist of oxygen vacancies. The combination of the electric field control of magnetization change and RS makes HP films possible for the multifunctional data storage media materials.

  20. Effects of water vapor in high vacuum chamber on the properties of HfO2 films

    Institute of Scientific and Technical Information of China (English)

    Bo Ling; Hongbo He; Jianda Shao

    2007-01-01

    The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer (RGA) was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure,absorption and laser-induced damage threshold (LIDT) of the samples were characterized by Lambda 900 spectrophotometer, X-ray diffraction (XRD), surface thermal lensing (STL) technique and 1064-nm Qswitched pulsed laser at a pulse duration of 12 ns respectively. It was found that a cold trap is an effective equipment to suppress water vapor in the vacuum chamber during the pumping process, and the coatings deposited in the vacuum atmosphere with relatively low water vapor composition show higher refractive index and smaller grain size. Meanwhile, the higher LIDT value is corresponding to lower absorbance.

  1. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO2 thin films from solid phase via annealing

    Science.gov (United States)

    Mimura, Takanori; Katayama, Kiliha; Shimizu, Takao; Uchida, Hiroshi; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-08-01

    0.07YO1.5-0.93HfO2 (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiOx/SiO2/(001)Si substrates, and (111)ITO/(111)Pt/TiOx/SiO2/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ-2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiOx/SiO2/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiOx/SiO2/(001)Si substrate, which does not contain ITO. Polarization-hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (Pr) of 9.6 and 10.8 μC/cm2 and coercive fields (Ec) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.

  2. Growth of (111)-oriented epitaxial and textured ferroelectric Y-doped HfO2 films for downscaled devices

    Science.gov (United States)

    Katayama, Kiliha; Shimizu, Takao; Sakata, Osami; Shiraishi, Takahisa; Nakamura, Syogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Uchida, Hiroshi; Funakubo, Hiroshi

    2016-09-01

    In this study, the growth of (111)-oriented epitaxial and textured YO1.5-HfO2 (0.07:0.93 ratio) films using the pulsed laser deposition method is presented. Epitaxial films were prepared on ITO//(111)yttria-stabilized zirconia (YSZ) substrates (ITO: Sn-doped In2O3; YSZ: yttria-stabilized zirconia), while textured films were prepared on (111)Pt/TiOx/SiO2//Si substrates with and without an ITO buffer layer via the grain on grain coherent growth. Inserting an ITO layer increased the volume fraction of the ferroelectric orthorhombic phase. Both the epitaxial and uniaxially textured films exhibited similar ferroelectricity with a remanent polarization of around 10 μC/cm2 and a coercive field of 1.9 to 2.0 MV/cm. These results present us with a way of obtaining stable and uniform ferroelectric properties for each grain and device cells consisting of a small number of grains. This opens the door for ultimately miniaturized ferroelectric devices, such as ferroelectric field effect transistors with small gate length and resistive random access memory using ferroelectric tunnel junctions.

  3. Solid-state dewetting of ultra-thin Au films on SiO2 and HfO2

    Science.gov (United States)

    Seguini, G.; Llamoja Curi, J.; Spiga, S.; Tallarida, G.; Wiemer, C.; Perego, M.

    2014-12-01

    Ultra-thin Au films with thickness (h) ranging from 0.5 to 6.0 nm were deposited at room temperature (RT) by means of e-beam evaporation on SiO2 and HfO2. Due to the natural solid-state dewetting (SSD) of the as-deposited films, Au nanoparticles (NPs) were formed on the substrates. By properly adjusting the h value, the size and the density of the Au NPs can be finely tuned. For h = 0.5 nm, spherical-like Au NPs with diameter below 5 nm and density in the order of 1012 Au NPs cm-2 were obtained without any additional thermal treatment independently from the substrate. The dependence of the Au NPs characteristics on the substrate starts to be effective for h ≥ 1.0 nm where the Au NPs diameter is in the 5-10 nm range and the density is around 1011 Au NPs cm-2. The effect of a subsequent high temperature (400-800 °C) annealing in N2 atmosphere on the Au NPs was investigated as well. For h ≤ 1.0 nm, the Au NPs characteristics evidenced an excellent thermal stability. Whereas the thermal treatment affects the cristallinity of the Au NPs. For the thicker films (2.0 ≤ h ≤ 6.0 nm), the thermal treatment becomes effective to induce the SSD. The proposed methodology can be exploited for the synthesis of Au NPs with diameter below 10 nm on different substrates at RT.

  4. Electrical Characterisation of Ferroelectric Field Effect Transistors based on Ferroelectric HfO2 Thin Films

    OpenAIRE

    Yurchuk, Ekaterina

    2015-01-01

    Ferroelectric field effect transistor (FeFET) memories based on a new type of ferroelectric material (silicon doped hafnium oxide) were studied within the scope of the present work. Utilisation of silicon doped hafnium oxide (Si:HfO2) thin films instead of conventional perovskite ferroelectrics as a functional layer in FeFETs provides compatibility to the CMOS process as well as improved device scalability. The influence of different process parameters on the properties of Si:HfO2 thin films ...

  5. Monomeric malonate precursors for the MOCVD of HfO2 and ZrO2 thin films.

    Science.gov (United States)

    Pothiraja, Ramasamy; Milanov, Andrian; Parala, Harish; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-01-28

    New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical beta-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 degrees C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.

  6. Optimum Ferroelectric Film Thickness in Metal-Ferroelectric-Insulator-Semiconductor Structures Composed of Pt, (Bi,La)4Ti3O12, HfO2, and Si

    Science.gov (United States)

    Takahashi, Kazuhiro; Aizawa, Koji; Ishiwara, Hiroshi

    2006-06-01

    The optimum ferroelectric film thickness in metal-ferroelectric-insulator-semiconductor (MFIS) structures is investigated, in which 80- to 560-nm-thick (Bi,La)4Ti3O12 (BLT) films are deposited on HfO2 buffer layers using a sol-gel spin-coating method. It is found from electrical characteristics of MFIS diodes as well as MIS diodes that the HfO2 layers act as excellent barriers for suppressing both leakage current and atom interdiffusion when they are annealed in a rapid-thermal-annealing furnace at 900 °C for 1 min in O2 flow. In MFIS diodes, the memory window width in capacitance-voltage (C-V) characteristics is found to increase from 0.2 to 1.6 V, as ferroelectric film thickness increases from 80 to 560 nm. On the basis of these results, the relationships among memory window width, ferroelectric film thickness, and the optimum applied voltage are discussed. Finally, it is shown from the capacitance change measured over 24 h that data retention characteristics are excellent in samples with BLT films thicker than 240 nm.

  7. Extended x-ray absorption fine structure measurements on radio frequency magnetron sputtered HfO2 thin films deposited with different oxygen partial pressures.

    Science.gov (United States)

    Maidul Haque, S; Nayak, C; Bhattacharyya, Dibyendu; Jha, S N; Sahoo, N K

    2016-03-20

    Two sets of HfO2 thin film have been deposited by the radio frequency magnetron sputtering technique at various oxygen partial pressures, one set without any substrate bias and another set with a 50 W pulsed dc substrate bias. The films have been characterized by extended x-ray absorption fine structure (EXAFS) measurements at the Hf L3 edge, and the structural information obtained from analysis of the EXAFS data has been used to explain the macroscopic behavior of the refractive index obtained from spectroscopic ellipsometry measurements. It has been observed that the variation of refractive index with oxygen partial pressure depends on the Hf-Hf bond length for the set of films deposited without substrate bias, while for the other set of films deposited with pulsed dc substrate bias, it depends on the oxygen coordination of the nearest neighbor shell surrounding Hf sites.

  8. Atomic layer deposition for fabrication of HfO2/Al2O3 thin films with high laser-induced damage thresholds.

    Science.gov (United States)

    Wei, Yaowei; Pan, Feng; Zhang, Qinghua; Ma, Ping

    2015-01-01

    Previous research on the laser damage resistance of thin films deposited by atomic layer deposition (ALD) is rare. In this work, the ALD process for thin film generation was investigated using different process parameters such as various precursor types and pulse duration. The laser-induced damage threshold (LIDT) was measured as a key property for thin films used as laser system components. Reasons for film damaged were also investigated. The LIDTs for thin films deposited by improved process parameters reached a higher level than previously measured. Specifically, the LIDT of the Al2O3 thin film reached 40 J/cm(2). The LIDT of the HfO2/Al2O3 anti-reflector film reached 18 J/cm(2), the highest value reported for ALD single and anti-reflect films. In addition, it was shown that the LIDT could be improved by further altering the process parameters. All results show that ALD is an effective film deposition technique for fabrication of thin film components for high-power laser systems.

  9. On the etching characteristics and mechanisms of HfO2 thin films in CF4/O2/Ar and CHF3/O2/Ar plasma for nano-devices.

    Science.gov (United States)

    Lim, Nomin; Efremov, Alexander; Yeom, Geun Young; Kwon, Kwang-Ho

    2014-12-01

    The study of etching characteristics and mechanisms for HfO2 and Si in CF4/O2/Ar and CHF3/O2/Ar inductively-coupled plasmas was carried out. The etching rates of HfO2 thin films as well as the HfO2/Si etching selectivities were measured as functions of Ar content in a feed gas (0-50% Ar) at fixed fluorocarbon gas content (50%), gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). Plasma parameters as well as the differences in plasma chemistries for CF4- and CHF3-based plasmas were analyzed using Langmuir probe diagnostics and 0-dimensional plasma modeling. It was found that, in both gas systems, the non-monotonic (with a maximum at about 15-20% Ar) HfO2 etching rate does not correlate with monotonic changes of F atom flux and ion energy flux. It was proposed that, under the given set of experimental conditions, the HfO2 etching process is affected by the factors determining the formation and decomposition kinetics of the fluorocarbon polymer layer. These factor are the fluxes of CF(x) (x = 1, 2) radicals, O atoms and H atoms.

  10. Study of the picosecond laser damage in HfO2/SiO2-based thin-film coatings in vacuum

    Science.gov (United States)

    Kozlov, A. A.; Papernov, S.; Oliver, J. B.; Rigatti, A.; Taylor, B.; Charles, B.; Smith, C.

    2016-12-01

    The laser damage thresholds of various HfO2/SiO2-based thin film coatings, including multilayer dielectric (MLD) gratings and high reflectors of different designs, prepared by E-beam and Plasma Ion Assisted Deposition (PIAD) methods, were investigated in vacuum, dry nitrogen, and after air-vacuum cycling. Single and multiple-pulse damage thresholds and their pulse-length scaling in the range of 0.6 to 100 ps were measured using a vacuum damage test station operated at 1053nm. The E-beam deposited high reflectors showed higher damage thresholds with square-root pulse-length scaling, as compared to PIAD coatings, which typically show slower power scaling. The former coatings appeared to be not affected by air/vacuum cycling, contrary to PIAD mirrors and MLD gratings. The relation between 1-on-1 and N-on-1 damage thresholds was found dependent on coating design and deposition methods.

  11. Laminated CeO2/HfO2 High-K Gate Dielectrics Grown by Pulsed Laser Deposition in Reducing Ambient

    NARCIS (Netherlands)

    Karakaya, K.; Barcones, B.; Zinine, A.; Rittersma, Z.M.; Graat, P.; Berkum, van J.G.M.; Verheijen, M.A.; Rijnders, G.; Blank, D.H.A.

    2006-01-01

    CeO2 and HfO2 dielectric layers were deposited in an Ar+(5%)H2 gas mixture by Pulsed Laser Deposition (PLD) on Si (100). A CeO2-Ce2O3 transformation is achieved by deposition in reducing ambient. It is also shown that in-situ post deposition anneal efficiently oxidizes Ce2O3 layers to CeO2. The prop

  12. Production of HfO2 thin films using different methods: chemical bath deposition, SILAR and sol-gel process

    Science.gov (United States)

    Kariper, İ. A.

    2014-08-01

    Hafnium oxide thin films (HOTFs) were successfully deposited onto amorphous glasses using chemical bath deposition, successive ionic layer absorption and reaction (SILAR), and sol-gel methods. The same reactive precursors were used for all of the methods, and all of the films were annealed at 300°C in an oven (ambient conditions). After this step, the optical and structural properties of the films produced by using the three different methods were compared. The structures of the films were analyzed by X-ray diffraction (XRD). The optical properties are investigated using the ultraviolet-visible (UV-VIS) spectroscopic technique. The film thickness was measured via atomic force microscopy (AFM) in the tapping mode. The surface properties and elemental ratios of the films were investigated and measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX). The lowest transmittance and the highest reflectance values were observed for the films produced using the SILAR method. In addition, the most intense characteristic XRD peak was observed in the diffraction pattern of the film produced using the SILAR method, and the greatest thickness and average grain size were calculated for the film produced using the SILAR method. The films produced using SILAR method contained fewer cracks than those produced using the other methods. In conclusion, the SILAR method was observed to be the best method for the production of HOTFs.

  13. Interfacial Layer Growth Condition Dependent Electrical Conduction in HfO2/SiO2 Heterostructured Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, S. K.; Misra, D.

    2012-01-01

    The electrical conduction mechanism contributing to the leakage current at different field regions has been studied in this work. The current-voltage (I-V) measurement of TiN/HfO{sub 2}/SiO{sub 2}/P-Si nMOS capacitor has been taken for two different interfacial layer (SiO{sub 2}) growth conditions such as in situ steam grown (ISSG) and chemical processes. It is observed that Poole-Frenkel mechanism is the dominant conduction mechanism in high field region whereas Ohmic conduction is dominant in the low field region. Also it is seen that the gate leakage current is reduced for the devices having chemically grown interfacial layer compared to that of ISSG devices. Both trap energy level ({phi}{sub t}) and activation energy (E{sub a}) increase in the chemically grown interfacial layer devices for the Poole-Frenkel and Ohmic conduction mechanisms respectively in comparison to ISSG devices. Trap energy level ({phi}{sub t}) of {approx} 0.2 eV, obtained from Poole-Frenkel mechanism indicates that the doubly ionized oxygen vacancies (V{sup 2-}) are the active defects and are contributing to the leakage current in these devices.

  14. Effects of Modified Precursor Solution on Microstructure of (Y,Yb)MnO3/HfO2/Si

    Science.gov (United States)

    Suzuki, Kazuyuki; Kato, Kazumi

    2007-10-01

    Ferroelectric/insulator/silicon structures were prepared using (Y,Yb)MnO3 films as ferroelectrics and HfO2 thin films as insulators through alkoxy-derived precursor solutions. The HfO2 solution was chemically modified in order to decrease the number of heating cycles required. The HfO2 films prepared using a partially hydrolyzed alkoxide solution had a uniform structure. From the results of measurements of the roughness level and refractive index of the HfO2 films, the partial hydrolysis of the HfO2 solution was found to be effective for the formation of a uniform microstructure in a thin insulator film. (Y,Yb)MnO3/HfO2/Si structures were constructed using the resultant HfO2 thin films prepared using the modified solutions.

  15. First Principles Calculation of Elastic Constants of Monoclinic HfO2 Thin Film%单斜相HfO2薄膜弹性常数的第一性原理计算

    Institute of Scientific and Technical Information of China (English)

    蔺玲; 邵淑英; 李静平

    2013-01-01

    用电子束蒸发沉积在K9玻璃基底上镀制HfO2薄膜,沉积温度为200℃,蒸发速率为0.03 nm/s.由X射线衍射谱可知薄膜出现明显结晶,且为单斜相和正交相混合结构,其中单斜相占明显优势.用Jade5软件分析得到单斜相HfO2的晶格常数a,b,c以及晶格矢量a和c之间的夹角β.基于得到的晶格常数建立了单斜相HfO2薄膜的晶体结构模型.同时建立固态单斜相HfO2的晶体结构模型进行对比.通过密度泛函理论(DFT)框架下的平面超软赝势法,采用两种不同的交换关联函数:局域密度近似(LDA)中的CA-PZ和广义梯度近似(GGA)中的质子平衡方程(PBE),计算了薄膜态和固态单斜晶相HfO2的弹性刚度系数矩阵Gij和弹性柔度系数矩阵Sij,Reuss模型、Voigt模型和Hill理论下的体积模量和剪切模量,材料平均杨氏模量和泊松比.此外还计算得到薄膜态和固态单斜晶相HfO2在不同方向上的杨氏模量.%HfO2 films are deposited by electron beam evaporation at a deposition rate of 0.03 nm/s and deposition temperature of 200 ℃ on K9 glass substrates. The films are observed to show a mixed structure of monoclinic and orthorhombic phase through X-ray diffraction and monoclinic phase is of obvious advantages. The structure parameters a, b, c and angel β of monoclinic HfO2 films are obtained using Jade5 software, based on which the crystal structure model is built. While solid crystal monoclinic HfO2 model is built to compare with the thin film one. Elastic stiffness constants of monoclinic HfO2 thin film and solid crystal are investigated using the plane waves ultrasoft pseudopotential technique based on the density functional theory (DFT) under two different exchange correlation functions of local density approximation (LDA) CA-PZ and generalized gradient approximation (GGA) PBE. Reuss, Voigt and Hill theories are used to estimate the bulk, shear and average Young's moduli and Possion ratio for polycrystalline HfO2

  16. High-reflectivity HfO2/SiO2 ultraviolet mirrors.

    Science.gov (United States)

    Torchio, Philippe; Gatto, Alexandre; Alvisi, Marco; Albrand, Gérard; Kaiser, Norbert; Amra, Claude

    2002-06-01

    High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approximately 99% near 250 nm are reported.

  17. Crystallization behaviors of ultrathin Al-doped HfO2 amorphous films grown by atomic layer deposition

    Science.gov (United States)

    Ma, Xue-Li; Yang, Hong; Xiang, Jin-Juan; Wang, Xiao-Lei; Wang, Wen-Wu; Zhang, Jian-Qi; Yin, Hua-Xiang; Zhu, Hui-Long; Zhao, Chao

    2017-02-01

    Not Available Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA016501) and the National Natural Science Foundation of China (Grant Nos. 61574168 and 61504163).

  18. Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

    Science.gov (United States)

    Florent, Karine

    The spontaneous polarization in ferroelectrics (FE) makes them particularly attractive for non-volatile memory and logic applications. Non-volatile FRAM memories using perovskite structure materials, such as Lead Zirconate Titanate (PZT) and Strontium Bismuth Tantalate (SBT) have been studied for many years. However, because of their scaling limit and incompatibility with CMOS beyond 130 nm node, floating gate Flash memory technology has been preferred for manufacturing. The recent discovery of ferroelectricity in doped HfO2 in 2011 has opened the door for new ferroelectric based devices compatible with CMOS technology, such as Ferroelectric Field Effect Transistor (FeFET) and Ferroelectric Tunnel Junctions (FTJ). This work began with developing ferroelectric hysteresis characterization capabilities at RIT. Initially reactively sputtered aluminum doped HfO 2 films were investigated. It was observed that the composition control using co-sputtering was not achievable within the existing capabilities. During the course of this study, collaboration was established with the NaMLab group in Germany to investigate Si doped HfO2 deposited by Atomic Layer Deposition (ALD). Metal Ferroelectric Metal (MFM) devices were fabricated using TiN as the top and bottom electrode with Si:HfO2 thickness ranging from 6.4 nm to 22.9 nm. The devices were electrically tested for P-E, C-V and I-V characteristics. Structural characterizations included TEM, EELS, XRR, XRD and XPS/Auger spectroscopy. Higher remanant polarization (Pr) was observed for films of 9.3 nm and 13.1 nm thickness. Thicker film (22.9 nm) showed smaller Pr. Devices with 6.4 nm thick films exhibit tunneling behavior showing a memristor like I-V characteristics. The tunnel current and ferroelectricity showed decrease with cycling indicating a possible change in either the structure or the domain configurations. Theoretical simulations using the improved FE model were carried out to model the ferroelectric behavior of

  19. Production of HfO2 thin films using different methods:chemical bath deposition, SILAR and sol-gel process

    Institute of Scientific and Technical Information of China (English)

    İ.A.Kariper

    2014-01-01

    Hafnium oxide thin films (HOTFs) were successfully deposited onto amorphous glasses using chemical bath deposition, succes-sive ionic layer absorption and reaction (SILAR), and sol-gel methods. The same reactive precursors were used for all of the methods, and all of the films were annealed at 300°C in an oven (ambient conditions). After this step, the optical and structural properties of the films pro-duced by using the three different methods were compared. The structures of the films were analyzed by X-ray diffraction (XRD). The opti-cal properties are investigated using the ultraviolet-visible (UV-VIS) spectroscopic technique. The film thickness was measured via atomic force microscopy (AFM) in the tapping mode. The surface properties and elemental ratios of the films were investigated and measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX). The lowest transmittance and the highest reflectance values were observed for the films produced using the SILAR method. In addition, the most intense characteristic XRD peak was observed in the diffraction pattern of the film produced using the SILAR method, and the greatest thickness and average grain size were calculated for the film produced using the SILAR method. The films produced using SILAR method contained fewer cracks than those produced using the other methods. In conclusion, the SILAR method was observed to be the best method for the production of HOTFs.

  20. Si掺杂HfO2薄膜的铁电和反铁电性质%Ferro electric and antiferro electric prop erties of Si-dop ed HfO2 thin films

    Institute of Scientific and Technical Information of China (English)

    周大雨; 徐进; Johannes Müller; Uwe Schröder

    2014-01-01

    通过改变Si掺杂量制备出了具有显著铁电和反铁电特征的HfO2纳米薄膜,对其电滞回线、电容-电压和漏电流-电压特性以及物相温度稳定性进行了对比研究。反铁电薄膜的介电系数大于铁电薄膜,在电场加载和减载过程中发生的可逆反铁电-铁电相变导致了双电滞回线的出现,在室温至185◦C的测试温度范围内未出现反铁电→顺电相变。在电流-电压特性测量时观察到的负微分电阻效应归因于极化弛豫等慢响应机理的贡献。%Ferroelectric and antiferroelectric HfO2 nano-films were prepared by changing silicon doping concentration, and their basic properties were compared in terms of polarization hysteresis, capacitance-voltage and leakage-voltage behavior, as well as the effect of temperature on phase stability. Antiferroelectric thin film exhibits a higher dielectric constant than the ferroelectric film, and is characterized by the double polarization hysteresis loops due to reversible antiferroelectric-ferroelectric phase transition induced during loading and unloading processes of electric field. No antiferroelectric-paraelectric phase transition is observed at measuring temperatures up to 185 ◦C. The negative differential resistivity effect observed in leakage measurements is attributed to the contributions from slow response mechanisms like polarization relaxation.

  1. 不同基底上HfO2/SiO2多层膜的力学性能%Mechanical Properties of HfO2/SiO2 Thin Films on Different Substrates

    Institute of Scientific and Technical Information of China (English)

    王河; 贺洪波; 张伟丽

    2013-01-01

    The HfO2/SiO2 films are deposited on K9 glass and Y3Al5O12 (YAG) crystal substrates by electron beam technology respectively.Nano-scratch tests are taken to investigate the mechanical properties of films respectively.The results show that the modulus of the films deposited on K9 and YAG are 34.8 GPa and 38.5 GPa respectively and the substrates have few effect on the elasticity modulus of the films.The adhesive force of the film is 7 mN on K9 substrate and 5 mN on YAG,and they present different failure modes.This can be attributed to the weak adhesion and large divergence of modulus between film and YAG crystal.The chemical binding state and elasticity modulus between the film and the substrate are taken to explain the different mechanical behaviors of the films on YAG and K9 substrates.%用电子束蒸发技术在K9玻璃及YAG晶体上沉积了HfO2/SiO2多层膜,采用纳米划痕仪对薄膜的力学性能进行了研究.实验结果表明:沉积在YAG和K9的多层膜弹性模量分别为34.8 GPa和38.5 GPa,基底对薄膜的弹性模量影响较小;YAG和K9上薄膜的粘附失效临界附着力分别为5 mN和7 mN,薄膜与YAG基底的结合状态较K9基底的差,并且呈现不同破坏模式.从薄膜之间及膜基界面处的界面结合状态和弹性模量两方面分析解释了YAG基底和K9基底上薄膜的不同力学行为.

  2. Optical properties of a HfO2/Si stack with a trace amount of nitrogen incorporation

    Institute of Scientific and Technical Information of China (English)

    Li Ye; Jiang Tingting; Sun Qingqing; Wang Pengfei; Ding Shijin; Zhang Wei

    2012-01-01

    HfO2 films were deposited by atomic layer deposition through alternating pulsing of Hf[N(C2H5)(CH3)]4 and H2O2.A trace amount of nitrogen was incorporated into the HfO2 through ammonia annealing.The composition,the interface stability of the HfO2/Si stack and the optical properties of the annealed films were analyzed to investigate the property evolution of HfO2 during thermal treatment.With a nitrogen concentration increase from 1.41 to 7.45%,the bandgap of the films decreased from 5.82 to 4.94 eV.

  3. Post-Cleaning Effect on a HfO2 Gate Stack Using a NF3/NH3 Plasma.

    Science.gov (United States)

    Lee, Min-Seon; Oh, Hoon-Jung; Lee, Joo-Hee; Lee, In-Geun; Shin, Woo-Gon; Kim, Kyu-Dong; Park, Jin-Gu; Ko, Dae-Hong

    2016-05-01

    The effects of dry cleaning of a HfO2 gate stack using NF3 only and a NF3/NH3 gas mixture plasma were investigated. The plasma dry cleaning process was carried out after HfO2 deposition using an indirect down-flow capacitively coupled plasma (CCP) system. An analysis of the chemical composition of the HfO2 gate stacks by XPS indicated that fluorine was incorporated into the HfO2 films during the plasma dry cleaning. Significant changes in the HfO2 chemical composition were observed as a result of the NF3 dry cleaning, while they were not observed in this case of NF3/NH3 dry cleaning. TEM results showed that the interfacial layer (IL) between the HfO2 and Si thickness was increased by the plasma dry cleaning. However, in the case of NF3/NH3 dry cleaning using 150 W, the IL thickness was suppressed significantly compared to the sample that had not been dry cleaned. Its electrical properties were also improved, including the low gate leakage currents, and reduced EOT. Finally, the finding show that the IL thickness of the HfO2 gate stack can be controlled by using the novel NF3/NH3 dry cleaning process technique without any the significant changes in chemical composition and metal-oxide-semiconductor (MOS) capacitor characteristics.

  4. On device design for steep-slope negative-capacitance field-effect-transistor operating at sub-0.2V supply voltage with ferroelectric HfO2 thin film

    Directory of Open Access Journals (Sweden)

    Masaharu Kobayashi

    2016-02-01

    Full Text Available Internet-of-Things (IoT technologies require a new energy-efficient transistor which operates at ultralow voltage and ultralow power for sensor node devices employing energy-harvesting techniques as power supply. In this paper, a practical device design guideline for low voltage operation of steep-slope negative-capacitance field-effect-transistors (NCFETs operating at sub-0.2V supply voltage is investigated regarding operation speed, material requirement and energy efficiency in the case of ferroelectric HfO2 gate insulator, which is the material fully compatible to Complementary Metal-Oxide-Semiconductor (CMOS process technologies. A physics-based numerical simulator was built to design NCFETs with the use of experimental HfO2 material parameters by modeling the ferroelectric gate insulator and FET channel simultaneously. The simulator revealed that NCFETs with ferroelectric HfO2 gate insulator enable hysteresis-free operation by setting appropriate operation point with a few nm thick gate insulator. It also revealed that, if the finite response time of spontaneous polarization of the ferroelectric gate insulator is 10-100psec, 1-10MHz operation speed can be achieved with negligible hysteresis. Finally, by optimizing material parameters and tuning negative capacitance, 2.5 times higher energy efficiency can be achieved by NCFET than by conventional MOSFETs. Thus, NCFET is expected to be a new CMOS technology platform for ultralow power IoT.

  5. On device design for steep-slope negative-capacitance field-effect-transistor operating at sub-0.2V supply voltage with ferroelectric HfO2 thin film

    Science.gov (United States)

    Kobayashi, Masaharu; Hiramoto, Toshiro

    2016-02-01

    Internet-of-Things (IoT) technologies require a new energy-efficient transistor which operates at ultralow voltage and ultralow power for sensor node devices employing energy-harvesting techniques as power supply. In this paper, a practical device design guideline for low voltage operation of steep-slope negative-capacitance field-effect-transistors (NCFETs) operating at sub-0.2V supply voltage is investigated regarding operation speed, material requirement and energy efficiency in the case of ferroelectric HfO2 gate insulator, which is the material fully compatible to Complementary Metal-Oxide-Semiconductor (CMOS) process technologies. A physics-based numerical simulator was built to design NCFETs with the use of experimental HfO2 material parameters by modeling the ferroelectric gate insulator and FET channel simultaneously. The simulator revealed that NCFETs with ferroelectric HfO2 gate insulator enable hysteresis-free operation by setting appropriate operation point with a few nm thick gate insulator. It also revealed that, if the finite response time of spontaneous polarization of the ferroelectric gate insulator is 10-100psec, 1-10MHz operation speed can be achieved with negligible hysteresis. Finally, by optimizing material parameters and tuning negative capacitance, 2.5 times higher energy efficiency can be achieved by NCFET than by conventional MOSFETs. Thus, NCFET is expected to be a new CMOS technology platform for ultralow power IoT.

  6. Synthesis of Freestanding HfO2 Nanostructures

    Science.gov (United States)

    2011-04-05

    Tang J, Fabbri J, Robinson RD, Zhu Y, Herman IP, Steigerwald ML, Brus LE: Solid-solution nanoparticles:use of a nonhydrolytic sol-gel synthesis to...colloidal HfO2 nanorods. Adv Mater 2007, 19:2608-2612. Page 21 5. Qiu X, Howe JY, Cardoso MB, Polat O, Heller W: Size control of highly ordered HfO2

  7. Downscaling ferroelectric field effect transistors by using ferroelectric Si-doped HfO2

    Science.gov (United States)

    Martin, Dominik; Yurchuk, Ekaterina; Müller, Stefan; Müller, Johannes; Paul, Jan; Sundquist, Jonas; Slesazeck, Stefan; Schlösser, Till; van Bentum, Ralf; Trentzsch, Martin; Schröder, Uwe; Mikolajick, Thomas

    2013-10-01

    Throughout the 22 nm technology node HfO2 is established as a reliable gate dielectric in contemporary complementary metal oxide semiconductor (CMOS) technology. The working principle of ferroelectric field effect transistors FeFET has also been demonstrated for some time for dielectric materials like Pb[ZrxTi1-x]O3 and SrBi2Ta2O9. However, integrating these into contemporary downscaled CMOS technology nodes is not trivial due to the necessity of an extremely thick gate stack. Recent developments have shown HfO2 to have ferroelectric properties, given the proper doping. Moreover, these doped HfO2 thin films only require layer thicknesses similar to the ones already in use in CMOS technology. This work will show how the incorporation of Si induces ferroelectricity in HfO2 based capacitor structures and finally demonstrate non-volatile storage in nFeFETs down to a gate length of 100 nm. A memory window of 0.41 V can be retained after 20,000 switching cycles. Retention can be extrapolated to 10 years.

  8. Annealing effects on residual stress of HfO2/SiO2 multilayers

    Institute of Scientific and Technical Information of China (English)

    Yanming Shen; Zhaoxia Han; Jianda Shao; Shuying Shao; Hongbo He

    2008-01-01

    HfO2/SiO2 multilayer films were deposited on BK7 glass substrates by electron beam evaporation method.The effects of annealing at the temperature between 200 and 400℃ on residual stresses have been studied.It is found that the residual stress of as-deposited HfO2/SiO2 multilayers is compressive.It becomes tensile after annealing at 200℃,and then the value of tensile stress increases as annealing temperature increases.And cracks appear in the film because tensile stress is too large when the sample is annealed at 400℃.At the same time,the crystallite size increases and interplanar distance decreases with the increase of annealing temperature.The variation of residual stresses is corresponding with the evolution of structures.

  9. High performance organic nonvolatile memory transistors based on HfO2 and poly(α-methylstyrene) electret hybrid charge-trapping layers

    Science.gov (United States)

    Xu, W. C.; He, H. X.; Jing, X. S.; Wu, S. J.; Zhang, Z.; Gao, J. W.; Gao, X. S.; Zhou, G. F.; Lu, X. B.; Liu, J.-M.

    2017-08-01

    In this work, we fabricated a high performance flash-type organic nonvolatile memory transistor, which adopted polymer-electret poly(α-methylstyrene) (PαMS) and HfO2 films as hybrid charge trapping layer (CTL). Compared with a single HfO2 or PαMS CTL structure, the hybrid HfO2/PαMS CTL structure can provide enhanced charge trapping efficiency to increase the device operation speed and reduce the leakage current to boost the device reliability. The fabricated nonvolatile organic memory transistors with the hybrid CTL shows excellent electrical properties, including low operation voltage (8 V), high speed (memories.

  10. Structural and electrical properties of metal ferroelectric insulator semiconductor structure of Al/SrBi2Ta2O9/HfO2/Si using HfO2 as buffer layer

    Science.gov (United States)

    Roy, A.; Dhar, A.; Bhattacharya, D.; Ray, S. K.

    2008-05-01

    Ferroelectric SrBi2Ta2O9 (SBT) thin films have been deposited by the radio-frequency magnetron sputtering technique on bare p-Si as well as on HfO2 insulating buffer p-Si. XRD patterns revealed the formation of a well-crystallized SBT perovskite thin film on the HfO2 buffer layer. The electrical properties of the metal-ferroelectric-insulator-semiconductor (MFIS) structure were characterized by varying thicknesses of the HfO2 layer. The MFIS structure exhibits a maximum clockwise C-V memory window of 1.60 V when the thickness of the HfO2 layer was 12 nm with a lower leakage current density of 6.20 × 10-7 A cm-2 at a positive applied voltage of 7 V. However, the memory window reaches a maximum value of 0.7 V at a bias voltage of ±5 and then decreases due to charge injection in the case of the insulating buffer layer thickness of 3 nm. The density of oxide trapped charges at/near the buffer layer-ferroelectric interface is studied by the voltage stress method. Capacitance-voltage (C-V) and leakage current density (J-V) characteristics of the Al/SBT/HfO2/Si(1 0 0) capacitor indicate that the introduction of the HfO2 buffer layer prevents interfacial diffusion between the SBT thin film and the Si substrate effectively and improves the interface quality. Furthermore, the Al/SBT/HfO2/Si structures exhibit excellent retention characteristics, the high and low capacitance values clearly distinguishable for over 1 h and 30 min. This shows that the proposed Al/SrBi2Ta2O9/HfO2/Si structure is ideally suitable for high performance ferroelectric memories.

  11. Perpendicular magnetic anisotropy of Co/Pt bilayers on ALD HfO2

    Science.gov (United States)

    Vermeulen, Bart F.; Wu, Jackson; Swerts, Johan; Couet, Sebastien; Linten, Dimitri; Radu, Iuliana P.; Temst, Kristiaan; Rampelberg, Geert; Detavernier, Christophe; Groeseneken, Guido; Martens, Koen

    2016-10-01

    Perpendicular Magnetic Anisotropy (PMA) is a key requirement for state of the art Magnetic Random Access Memories (MRAM). Currently, PMA has been widely reported in standard Magnetic Tunnel Junction material stacks using MgO as a dielectric. In this contribution, we present the first report of PMA at the interface with a high-κ dielectric grown by Atomic Layer Deposition, HfO2. The PMA appears after annealing a HfO2/Co/Pt/Ru stack in N2 with the Keff of 0.25 mJ/m2 as determined by Vibrating Sample Magnetometry. X-Ray Diffraction and Transmission Electron Microscopy show that the appearance of PMA coincides with interdiffusion and the epitaxial ordering of the Co/Pt bilayer. High-κ dielectrics are especially interesting for Voltage Control of Magnetic Anisotropy applications and are of potential interest for low-power MRAM and spintronics technologies.

  12. Crystal structure of Si-doped HfO2

    Science.gov (United States)

    Zhao, Lili; Nelson, Matthew; Aldridge, Henry; Iamsasri, Thanakorn; Fancher, Chris M.; Forrester, Jennifer S.; Nishida, Toshikazu; Moghaddam, Saeed; Jones, Jacob L.

    2014-01-01

    Si-doped HfO2 was prepared by solid state synthesis of the starting oxides. Using Rietveld refinement of high resolution X-ray diffraction patterns, a substitutional limit of Si in HfO2 was determined as less than 9 at. %. A second phase was identified as Cristobalite (SiO2) rather than HfSiO4, the latter of which would be expected from existing SiO2-HfO2 phase diagrams. Crystallographic refinement with increased Si-dopant concentration in monoclinic HfO2 shows that c/b increases, while β decreases. The spontaneous strain, which characterizes the ferroelastic distortion of the unit cell, was calculated and shown to decrease with increasing Si substitution.

  13. Contamination process and laser-induced damage of HfO2/SiO2 coatings in vacuum

    Institute of Scientific and Technical Information of China (English)

    Ping Ma; Feng Pan; Songlin Chen; Zhen Wang; Jianping Hu; Qinghua Zhang; Jianda Shao

    2009-01-01

    The performances of HfO2/SiO2 single- and multi-layer coatings in vacuum influenced by contamination are studied. The surface morphology, the transmittance spectrum, and the laser-induced damage threshold are investigated. The results show that the contamination in vacuum mainly comes from the vacuum system and the contamination process is different for the HfO2 and SiO2 films. The laser-induced damage experiments at 1064 nm in vacuum show that the damage resistance of the coatings will decrease largely due to the organic contamination.

  14. Distribution of electron traps in SiO2/HfO2 nMOSFET

    Science.gov (United States)

    Xiao-Hui, Hou; Xue-Feng, Zheng; Ao-Chen, Wang; Ying-Zhe, Wang; Hao-Yu, Wen; Zhi-Jing, Liu; Xiao-Wei, Li; Yin-He, Wu

    2016-05-01

    In this paper, the principle of discharge-based pulsed I-V technique is introduced. By using it, the energy and spatial distributions of electron traps within the 4-nm HfO2 layer have been extracted. Two peaks are observed, which are located at ΔE ˜ -1.0 eV and -1.43 eV, respectively. It is found that the former one is close to the SiO2/HfO2 interface and the latter one is close to the gate electrode. It is also observed that the maximum discharge time has little effect on the energy distribution. Finally, the impact of electrical stress on the HfO2 layer is also studied. During stress, no new electron traps and interface states are generated. Meanwhile, the electrical stress also has no impact on the energy and spatial distribution of as-grown traps. The results provide valuable information for theoretical modeling establishment, material assessment, and reliability improvement for advanced semiconductor devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the New Experiment Development Funds for Xidian University, China (Grant No. SY1434), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China (Grant No. JY0600132501).

  15. Transparent nanoscale floating gate memory using self-assembled bismuth nanocrystals in Bi(2) Mg(2/3) Nb(4/3) O(7) (BMN) pyrochlore thin films grown at room temperature.

    Science.gov (United States)

    Jung, Hyun-June; Yoon, Soon-Gil; Hong, Soon-Ku; Lee, Jeong-Yong

    2012-07-01

    Bismuth nanocrystals for a nanoscale floating gate memory device are self-assembled in Bi(2) Mg(2/3) Nb(4/3) O(7) (BMN) dielectric films grown at room temperature by radio-frequency sputtering. The TEM cross-sectional image shows the "real" structure grown on a Si (001) substrate. The image magnified from the dotted box (red color) in the the cross-sectional image clearly shows bismuth nanoparticles at the interface between the Al(2) O(3) and HfO(2) layer (right image). Nanoparticles approximately 3 nm in size are regularly distributed at the interface.

  16. Structure and morphology of Ru films grown by atomic layer deposition from 1-ethyl-1’-methyl-ruthenocene

    Science.gov (United States)

    Kukli, Kaupo; Aarik, Jaan; Aidla, Aleks; Uustare, Teet; Jõgi, Indrek; Lu, Jun; Tallarida, Massimo; Kemell, Marianna; Kiisler, Alma-Asta; Ritala, Mikko; Leskelä, Markku

    2010-06-01

    Ru thin films were grown on TiO 2, Al 2O 3, HfO 2, and ZrO 2 films as well as on HF-etched silicon and SiO 2-covered silicon by atomic layer deposition from 1-ethyl-1'-methyl-ruthenocene, (CH 3C 5H 4)(C 2H 5C 5H 4)Ru, and oxygen. The growth of Ru was obtained and characterized at temperatures ranging from 250 to 325 °C. On epitaxial rutile, highly oriented growth of Ru with hexagonal structure was achieved, while on other substrates the films possessed nonoriented hexagonal structure. Ruthenium oxide was not detected in the films. The lowest resistivity value obtained for 5.0-6.6 nm thick films was 26 μΩ cm. The conductivity of the films depended somewhat on the deposition cycle time parameters and, expectedly, more strongly on the amount of deposition cycles. Increase in the deposition temperature of underlying metal oxide films increased the conductivity of Ru layers.

  17. The Post—deposition Anneal Effects on the Electrical Properties of HfO2 Gate Dielectric Deposited by Ion Beam Sputtering at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    KANGJinfeng; LIUXiaoyan; TIANDayu; WANGWei; LIANGuijun; XIONGGuangcheng; HANRuqi

    2003-01-01

    HfO2 high K gate dielectric films were fab-ricated on p-Si(100) substrates by ion beam sputtering at room temperature followed by a post-deposition anneal-ing (PDA). The PDA effects on the electrical properties of HfO2 gate dielectric films were studied. High quality HfO2 gate dielectric with small equivalent oxide thickness (EOT = 2.3nm), small hystereis (△VFB<50mV), and lowleakage current (< 1× 10-4A/cm2@lV) was fabricated.The studies of PDA effects on the electrical properties in-dicate that the PDA process in nitrogen ambient will be necessary for the HfO2 gate dielectric films deposited by ion beam sputtering the sintered target at room temper-ature in order to obtain small equivalent oxide thickness and low leakage currents, whereas a PDA in oxygen ambi-ent will be not required. The results also means that there is less oxygen vacancy defect produced in the HfO2 gate dielectric films during the deposition at room temperature.

  18. Synthesis of freestanding HfO2 nanostructures

    Directory of Open Access Journals (Sweden)

    Boyle Kayla

    2011-01-01

    Full Text Available Abstract Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic, freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide. PACS: 81.07.-b, 61.46.Hk, 68.37.Hk.

  19. Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

    Science.gov (United States)

    Bulusu, A.; Singh, A.; Wang, C. Y.; Dindar, A.; Fuentes-Hernandez, C.; Kim, H.; Cullen, D.; Kippelen, B.; Graham, S.

    2015-08-01

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al2O3)/hafnium oxide (HfO2) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiNx layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  20. Scanning transmission electron microscopy of gate stacks with HfO2 dielectrics and TiN electrodes

    OpenAIRE

    Agustin, Melody P.; Fonseca, Leo R. C.; Hooker, Jacob C.; Stemmer, Susanne

    2005-01-01

    High-angle annular dark-field (HAADF) imaging and electron energy-loss spectroscopy (EELS) in scanning transmission electron microscopy were used to investigate HfO2 gate dielectrics grown by atomic layer deposition on Si substrates, and their interfaces with TiN electrodes and silicon, as a function of annealing temperature. Annealing at high temperatures (900 °C) caused significant roughening of both bottom (substrate) and top (electrode) interface. At the bottom interface, HAADF images s...

  1. Fabrication and characteristics of ZnO MOS capacitors with high-K HfO2 gate dielectrics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    ZnO thin films are first deposited on n-type silicon by radio frequency (rf) magnetron sputtering at room temperature.And high-K HfO2 gate dielectrics thin films are deposited on ZnO films to form metal-oxide semiconductor (MOS) capacitors.The temperature to fabricate ZnO MOS capacitors is 400°C,and the low temperature process is applicable for thin film transistors,flat-panel display (FPD),flexible display,etc.The electronic availability of ZnO thin films,which serve as a semiconductor material for MOS capacitors with HfO2 gate dielectric is investigated.High frequency (1 MHz) capacitance-voltage (C-V) and current-voltage (I-V) characteristics of ZnO-based MOS capacitors are measured.The thermal stability and electronic stability of the ZnO capacitors are investigated,respectively.Experimental results indicate that good electrical characteristics can be obtained on ZnO substrates with high-K HfO2 gate dielectrics.Besides,the ZnO capacitors can exhibit high thermal and electronic stabilities.

  2. Ferroelectric HfO2-based materials for next-generation ferroelectric memories

    Science.gov (United States)

    Fan, Zhen; Chen, Jingsheng; Wang, John

    2016-05-01

    Ferroelectric random access memory (FeRAM) based on conventional ferroelectric perovskites, such as Pb(Zr,Ti)O3 and SrBi2Ta2O9, has encountered bottlenecks on memory density and cost, because those conventional perovskites suffer from various issues mainly including poor complementary metal-oxide-semiconductor (CMOS)-compatibility and limited scalability. Next-generation cost-efficient, high-density FeRAM shall therefore rely on a material revolution. Since the discovery of ferroelectricity in Si:HfO2 thin films in 2011, HfO2-based materials have aroused widespread interest in the field of FeRAM, because they are CMOS-compatible and can exhibit robust ferroelectricity even when the film thickness is scaled down to below 10 nm. A review on this new class of ferroelectric materials is therefore of great interest. In this paper, the most appealing topics about ferroelectric HfO2-based materials including origins of ferroelectricity, advantageous material properties, and current and potential applications in FeRAM, are briefly reviewed.

  3. Growth and luminescence properties of Eu-doped HfO2/α-Al2O3 eutectic scintillator

    Institute of Scientific and Technical Information of China (English)

    Kei Kamada; Kosuke Hishinuma; Shunsuke Kurosawa; Akihiro Yamaji; Yasuhiro Shoji; Jan Pejchal; Yuji Ohashi; Yuui Yokota; Akira Yoshikawa

    2016-01-01

    HfO2/α-Al2O3 eutectics were grown by the micro-pulling down (μ-PD) method at the composition of 63.2 mol.%α-Al2O3, 35.512 mol.%HfO2, 0.92 mol.%Eu2O3 and 0.368 mol.%Y2O3. Rod phases with around 3–4μm diameter were observed on the transverse cross-section. The phase-separated scintillator fibers (PSSFs) structure with fibers of around 3–4μm diameter and 10–20μm length was observed. The electron back scattering patterns indicated crystal orientation of [101] for monoclinic HfO2 rod phase and [0001] forα-Al2O3 matrix in the transverse cross-section. Eu3+4f-4f emission was observed at 550–750 nm.

  4. Capacitance-voltage and retention characteristics of Pt/SrBi2Ta2O9/HfO2/Si structures with various buffer layer thickness

    Science.gov (United States)

    Tang, M. H.; Sun, Z. H.; Zhou, Y. C.; Sugiyama, Y.; Ishiwara, H.

    2009-05-01

    The metal-ferroelectric-insulator-semiconductor (MFIS) structure diodes with SrBi2Ta2O9 (SBT) as ferroelectric thin film and HfO2 as insulating buffer layer were fabricated. The electrical properties of MFIS structure were investigated for different HfO2 buffer layer thickness. The experimental results show that the memory window extended significantly as the HfO2 layer thickness increased from 6 to 10 nm. It is also observed that the leakage current was reduced to about 10-10 A at applied voltage of 4 V, and the high and low capacitances remained distinguishable for over 8 h even if we extrapolate the measured data to 10 years.

  5. Ferroelectricity-modulated resistive switching in Pt/Si:HfO2/HfO2-x /Pt memory

    Science.gov (United States)

    Ran, Jiang; Xianghao, Du; Zuyin, Han

    2016-08-01

    It is investigated for the effect of a ferroelectric Si:HfO2 thin film on the resistive switching in a stacked Pt/Si:HfO2/highly-oxygen-deficient HfO2-x /Pt structure. Improved resistance performance was observed. It was concluded that the observed resistive switching behavior was related to the modulation of the width and height of a depletion barrier in the HfO2-x layer, which was caused by the Si:HfO2 ferroelectric polarization field effect. Reliable switching reproducibility and long data retention were observed in these memory cells, suggesting their great potential in non-volatile memories applications with full compatibility and simplicity. Project supported by the National Natural Science Foundation of China (No. 11374182), the Natural Science Foundation of Shandong Province (No. ZR2012FQ012), and the Jinan Independent Innovation Projects of Universities (No. 201303019).

  6. A small shoulder of optical absorption in polycrystalline HfO2 by LDA+U approach

    Science.gov (United States)

    Qin, Liyuan; Li, Jinping; Meng, Songhe; Lu, Hantao; Tohyama, Takami

    2016-10-01

    The dielectric function of the wide-gap optical material HfO2 is investigated by the local density approximation (LDA)+U approach. We focus on the origin of the shoulder-like structure near the edge of the band gap in the imaginary part of the dielectric function, which has been observed on the thin films of monoclinic HfO2. A comparison study on the three polymorphs of hafnia shows that regardless of the underlying crystal structure, the existence of the shoulder is mainly controlled by the value of the shortest length of Hf-O bonds. The proposition is further supported by the numerical simulations of isostatic pressing. A possible implication in high-pressure measurements is suggested accordingly.

  7. PLD-grown thin film saturable absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Tellkamp, Friedjof

    2012-11-01

    The subject of this thesis is the preparation and characterization of thin films made of oxidic dielectrics which may find their application as saturable absorber in passively Q-switched lasers. The solely process applied for fabrication of the thin films was the pulsed laser deposition (PLD) which stands out against other processes by its flexibility considering the composition of the systems to be investigated. Within the scope of this thesis the applied saturable absorbers can be divided into two fundamentally different kinds of functional principles: On the one hand, saturable absorption can be achieved by ions embedded in a host medium. Most commonly applied bulk crystals are certain garnets like YAG (Y{sub 3}Al{sub 5}O{sub 12}) or the spinel forsterite (Mg{sub 2}SiO{sub 4}), in each case with chromium as dopant. Either of these media was investigated in terms of their behavior as PLD-grown saturable absorber. Moreover, experiments with Mg{sub 2}GeO{sub 4}, Ca{sub 2}GeO{sub 4}, Sc{sub 2}O{sub 3}, and further garnets like YSAG or GSGG took place. The absorption coefficients of the grown films of Cr{sup 4+}:YAG were determined by spectroscopic investigations to be one to two orders of magnitude higher compared to commercially available saturable absorbers. For the first time, passive Q-switching of a Nd:YAG laser at 1064 nm with Cr{sup 4+}:YAG thin films could be realized as well as with Cr:Sc{sub 2}O{sub 3} thin films. On the other hand, the desirable effect of saturable absorption can also be generated by quantum well structures. For this purpose, several layer system like YAG/LuAG, Cu{sub 2}O/MgO, and ZnO/corumdum were investigated. It turned out that layer systems with indium oxide (In{sub 2}O{sub 3}) did not only grew in an excellent way but also showed up a behavior regarding their photo luminescence which cannot be explained by classical considerations. The observed luminescence at roughly 3 eV (410 nm) was assumed to be of excitonic nature and its

  8. Structural and dielectric properties of amorphous ZrO2 and HfO2

    Science.gov (United States)

    Ceresoli, Davide; Vanderbilt, David

    2006-09-01

    Zirconia (ZrO2) and hafnia (HfO2) are leading candidates for replacing SiO2 as the gate insulator in complementary metal-oxide semiconductor technology. Amorphous versions of these materials ( a-ZrO2 and a-HfO2 ) can be grown as metastable phases on top of a silicon buffer; while they tend to recrystallize during subsequent annealing steps, they would otherwise be of considerable interest because of the promise they hold for improved uniformity and electrical passivity. In this work, we report our theoretical studies of a-ZrO2 and a-HfO2 by first-principles density-functional methods. We construct realistic amorphous models using the “activation-relaxation” technique of Barkema and Mousseau. The structural, vibrational, and dielectric properties of the resulting models are analyzed in detail. The overall average dielectric constant is computed and found to be comparable to that of the monoclinic phase.

  9. Strong photoluminescence of the porous silicon with HfO2-filled microcavities

    Science.gov (United States)

    Jiang, Ran; Wu, Zhengran; Du, Xianghao; Han, Zuyin; Sun, Weideng

    2015-06-01

    Greatly enhanced blue emission was observed at room temperature in the single-crystal silicon with HfO2 filled into its microcavities. The broad blue band light was emitted from both the HfO2 dielectric and the porous Si. The ferroelectricity of HfO2 enhances the blue emission from Si by its filling into the microcaivities. At the same time, HfO2 contributes to the light emission for the transitions of the defect levels for oxygen vacancy. The observation of greatly enhanced blue light emission of the porous Si filled with HfO2 dielectric is remarkable as both HfO2 and Si are highly compatible with Si-based electronic industry.

  10. HfO2/SiO2 multilayer based reflective and transmissive optics from the IR to the UV

    Science.gov (United States)

    Wang, Jue; Hart, Gary A.; Oudard, Jean Francois; Wamboldt, Leonard; Roy, Brian P.

    2016-05-01

    HfO2/SiO2 multilayer based reflective optics enable threat detection in the short-wave/middle-wave infrared and high power laser targeting capability in the near infrared. On the other hand, HfO2/SiO2 multilayer based transmissive optics empower early missile warning by taking advantage of the extremely low noise light detection in the deep-ultraviolet region where solar irradiation is strongly absorbed by the ozone layer of the earth's atmosphere. The former requires high laser damage resistance, whereas the latter needs a solar-blind property, i.e., high transmission of the radiation below 290 nm and strong suppression of the solar background from 300 nm above. The technical challenges in both cases are revealed. The spectral limits associated with the HfO2 and SiO2 films are discussed and design concepts are schematically illustrated. Spectral performances are realized for potential A and D and commercial applications.

  11. Study of structure and antireflective properties of LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 trilayers for UV applications

    Science.gov (United States)

    Marszalek, K.; Jaglarz, J.; Sahraoui, B.; Winkowski, P.; Kanak, J.

    2015-01-01

    The aim of this paper is to study antireflective properties of the tree-layer systems LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 deposited on heated optical glass substrates. The films were evaporated by the use two deposition techniques. In first method oxide films were prepared by means of e-gun evaporation in vacuum of 5 × 10-5 mbar in the presence of oxygen. The second was used for the deposition of fluoride films. They were obtained by means of thermal source evaporation. Simulation of reflectance was performed for 1M2H1L (Quarter Wavelength Optical Thickness) film stack on an optical quartz glass with the refractive index n = 1.46. The layer thickness was optimized to achieve the lowest light scattering from glass surface covered with dioxide and fluoride films. The values of the interface roughness were determined through atomic force microscopy measurements. The essence of performed calculation was to find minimum reflectance of light in wide ultraviolet region. The spectral dispersion of the refractive index needed for calculations was determined from ellipsometric measurements using the spectroscopic ellipsometer M2000. Additionally, the total reflectance measurements in integrating sphere coupled with Perkin Elmer 900 spectrophotometer were performed. These investigations allowed to determine the influence of such film features like surface and interface roughness on light scattering.

  12. Study of Direct-Contact HfO2/Si Interfaces

    Directory of Open Access Journals (Sweden)

    Noriyuki Miyata

    2012-03-01

    Full Text Available Controlling monolayer Si oxide at the HfO2/Si interface is a challenging issue in scaling the equivalent oxide thickness of HfO2/Si gate stack structures. A concept that the author proposes to control the Si oxide interface by using ultra-high vacuum electron-beam HfO2 deposition is described in this review paper, which enables the so-called direct-contact HfO2/Si structures to be prepared. The electrical characteristics of the HfO2/Si metal-oxide-semiconductor capacitors are reviewed, which suggest a sufficiently low interface state density for the operation of metal-oxide-semiconductor field-effect-transistors (MOSFETs but reveal the formation of an unexpected strong interface dipole. Kelvin probe measurements of the HfO2/Si structures provide obvious evidence for the formation of dipoles at the HfO2/Si interfaces. The author proposes that one-monolayer Si-O bonds at the HfO2/Si interface naturally lead to a large potential difference, mainly due to the large dielectric constant of the HfO2. Dipole scattering is demonstrated to not be a major concern in the channel mobility of MOSFETs.

  13. Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application

    Directory of Open Access Journals (Sweden)

    Molina-Aldareguia Jon

    2011-01-01

    Full Text Available Abstract Nanostructuring of ultrathin HfO2 films deposited on GaAs (001 substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching. PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea

  14. In-situ growth of HfO2 on clean 2H-MoS2 surface: Growth mode, interface reactions and energy band alignment

    Science.gov (United States)

    Chen, Chang Pang; Ong, Bin Leong; Ong, Sheau Wei; Ong, Weijie; Tan, Hui Ru; Chai, Jian Wei; Zhang, Zheng; Wang, Shi Jie; Pan, Ji Sheng; Harrison, Leslie John; Kang, Hway Chuan; Tok, Eng Soon

    2017-10-01

    Room temperature growth of HfO2 thin film on clean 2H-MoS2 via plasma-sputtering of Hf-metal target in an argon/oxygen environment was studied in-situ using x-ray photoelectron spectroscopy (XPS). The deposited film was observed to grow akin to a layer-by-layer growth mode. At the onset of growth, a mixture of sulfate- and sulfite-like species (SOx2- where x = 3, 4), and molybdenum trioxide (MoO3), are formed at the HfO2/MoS2 interface. An initial decrease in binding energies for both Mo 3d and S 2p core-levels of the MoS2 substrate by 0.4 eV was also observed. Their binding energies, however, did not change further with increasing HfO2 thickness. There was no observable change in the Hf4f core-level binding energy throughout the deposition process. With increasing HfO2 deposition, MoO3 becomes buried at the interface while SOx2- was observed to be present in the film. The shift of 0.4 eV for both Mo 3d and S 2p core-levels of the MoS2 substrate can be attributed to a charge transfer from the substrate to the MoO3/SOx2--like interface layer. Consequently, the Type I heterojunction valence band offset (conduction band offset) becomes 1.7 eV (2.9 eV) instead of 1.3 eV (3.3 eV) expected from considering the bulk HfO2 and MoS2 valence band offset (conduction band offset). The formation of these states and its influence on band offsets will need to be considered in their device applications.

  15. The initial atomic layer deposition of HfO2/Si(001) as followed in situ by synchrotron radiation photoelectron spectroscopy

    Science.gov (United States)

    Tallarida, Massimo; Karavaev, Konstantin; Schmeisser, Dieter

    2008-09-01

    We have grown HfO2 on Si(001) by atomic layer deposition (ALD) using HfCl4 and H2O as precursors. The early stages of the ALD were investigated with high-resolution photoelectron spectroscopy and x-ray absorption spectroscopy. We observed the changes occurring in the Si2p, O1s, Hf4f, Hf4d, and Cl2p core level lines after each ALD cycle up to the complete formation of two layers of HfO2. From the analysis of those variations, we deduced the growth properties of HfO2. The first layer consists of a sparse and Cl-contaminated oxide because of the incomplete oxidation, and the second layer is denser than the first one and with an almost stoichiometric O /Hf ratio. At the completion of the second layer, the x-ray absorption spectra revealed the change of the Hf-oxide chemical state due to the transition from the thin Hf-oxide to the bulklike HfO2.

  16. First principle simulations on the effects of oxygen vacancy in HfO2-based RRAM

    Directory of Open Access Journals (Sweden)

    Yuehua Dai

    2015-01-01

    Full Text Available HfO2-based resistive random access memory (RRAM takes advantage of oxygen vacancy (V o defects in its principle of operation. Since the change in resistivity of the material is controlled by the level of oxygen deficiency in the material, it is significantly important to study the performance of oxygen vacancies in formation of conductive filament. Excluding effects of the applied voltage, the Vienna ab initio simulation package (VASP is used to investigate the orientation and concentration mechanism of the oxygen vacancies based on the first principle. The optimal value of crystal orientation [010] is identified by means of the calculated isosurface plots of partial charge density, formation energy, highest isosurface value, migration barrier, and energy band of oxygen vacancy in ten established orientation systems. It will effectively influence the SET voltage, forming voltage, and the ON/OFF ratio of the device. Based on the results of orientation dependence, different concentration models are established along crystal orientation [010]. The performance of proposed concentration models is evaluated and analyzed in this paper. The film is weakly conductive for the samples deposited in a mixture with less than 4.167at.% of V o contents, and the resistive switching (RS phenomenon cannot be observed in this case. The RS behavior improves with an increase in the V o contents from 4.167at.% to 6.25at.%; nonetheless, it is found difficult to switch to a stable state. However, a higher V o concentration shows a more favorable uniformity and stability for HfO2-based RRAM.

  17. Characterization of Pt/Bi3.15Nd0.85Ti3O12/HfO2/Si structure using a hafnium oxide as buffer layer for ferroelectric-gate field effect transistors

    Science.gov (United States)

    Xie, Dan; Luo, Yafeng; Han, Xueguang; Ren, Tianling; Liu, Litian

    2009-12-01

    We have investigated the structural and electrical properties of metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with Bi3.15Nd0.85Ti3O12 (BNdT) thin film deposited on Si and hafnium oxide (HfO2)/Si substrates. Microstructural analysis reveals the formation of well-crystallized BNdT perovskite film and good interface between BNdT film and HfO2 buffer layer. Pt/BNdT/HfO2/Si structure exhibits a memory window of 1.12 V at an operation voltage of 3.5 V. The width of memory window for the MFIS structure varies with increasing thickness of HfO2 layer, and 4-nm-thickness is optimum. The results from the fatigue test indicate a slight degradation of the memory window after 1010 switching cycles. These properties are encouraging for the development of ferroelectric memory transistors.

  18. Single layer of Ge quantum dots in HfO2 for floating gate memory capacitors.

    Science.gov (United States)

    Lepadatu, A M; Palade, C; Slav, A; Maraloiu, A V; Lazanu, S; Stoica, T; Logofatu, C; Teodorescu, V S; Ciurea, M L

    2017-04-28

    High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO2 were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO 2/floating gate of single layer of Ge QDs in HfO 2/tunnel HfO 2/p-Si wafers. Both Ge and HfO2 are nanostructured by RTA at moderate temperatures of 600-700 °C. By nanostructuring at 600 °C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 × 10(15) m(-2) is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO2 nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO2 NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO2 NCs boundaries, while another part of the Ge atoms is present inside the HfO2 lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8 ± 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO2, distanced from the Si substrate by the tunnel oxide layer with a precise thickness.

  19. Photocurrent generation in carbon nanotube/cubic-phase HfO2 nanoparticle hybrid nanocomposites

    Directory of Open Access Journals (Sweden)

    Protima Rauwel

    2016-07-01

    Full Text Available A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs and cubic-phase HfO2 nanoparticles (NPs with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.

  20. Thirty-Day-Long Data Retention in Ferroelectric-Gate Field-Effect Transistors with HfO2 Buffer Layers

    Science.gov (United States)

    Takahashi, Kazuhiro; Aizawa, Koji; Park, Byung-Eun; Ishiwara, Hiroshi

    2005-08-01

    Metal-ferroelectric-insulator-semiconductor (MFIS) diodes and p-channel MFIS field-effect transistors (FETs) were fabricated and their electrical properties were characterized. These MFIS structures were formed using HfO2 as an insulating buffer layer, and SrBi2Ta2O9 (SBT) and (Bi,La)4Ti3O12 (BLT) as ferroelectric films. HfO2 buffer layers of about 8 nm physical thickness were deposited by ultrahigh-vacuum (UHV) electron-beam evaporation, then ferroelectric films of about 400 nm thickness were deposited by sol-gel spin coating. The fabricated p-channel MFIS-FETs with the SBT/HfO2 gate structure exhibited a drain current on/off ratio larger than 103 even after 30 days had elapsed. It was also found that the degradation of ferroelectricity was not pronounced even after applying 2.2× 1011 bipolar pulses.

  1. Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

    Institute of Scientific and Technical Information of China (English)

    Yongguang Shan; Hongbo He; C haoyang Wei; Ying Wang; Yuan'an Zhao

    2011-01-01

    Samples with nodular defects grown from gold nanoparticles are prepared, and laser-induced damage tests are conducted on them. Nodular defects, which are in critical state of damage, are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope. The cross-sectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface, or are even melted. The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress. The numerical results give the critical temperature of the seed region and the thermal stress for crack generation, irradiated with threshold fluence. The numerical results are in good agreement with the experimental ones.%Samples with nodular defects grown from gold nanoparticles are prepared,and laser induced damage tests are conducted on them.Nodular defects,which are in critical state of damage,are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope.The crosssectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface,or are even melted.The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress.The numerical results give the critical temperature of the seed region and the thermal stress for crack generation,irradiated with threshold fluence.The numerical results are in good agreement with the experimental ones.Nodular defect,a typical defect in multilayer coatings,largely limits the improvement of the laser-induced damage threshold (LIDT) in the nanosecond regime and thus has been widely investigated.Electric field enhancement in the nodule,induced by the microlens effect of the dome structure of nodular defects,is an important factor in reducing the LIDT[1-5].Recently

  2. Ferroelectric phase stabilization of HfO2 by nitrogen doping

    Science.gov (United States)

    Xu, Lun; Nishimura, Tomonori; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2016-09-01

    We report that nitrogen (N) doping can drive the ferroelectricity of HfO2. It was found that N doping can cause the transition from a monoclinic phase to a highly symmetric phase. The role of N doping is discussed from the viewpoints of charge balance and bond-constraining effects. The former is responsible for the structural transformation from a paraelectric phase to a ferroelectric phase by forming an oxygen vacancy. In addition, Hf-N and N-O bonds with covalent characteristics have strong effects on HfO2 structural and electrical properties, and thus contribute to a marked HfO2 para-/ferroelectric transition.

  3. Interaction of La2O3 capping layers with HfO2 gate dielectrics

    Science.gov (United States)

    Copel, M.; Guha, S.; Bojarczuk, N.; Cartier, E.; Narayanan, V.; Paruchuri, V.

    2009-11-01

    We report the effect of La2O3 capping layers on HfO2/SiO2/Si dielectrics, proposed for use in threshold voltage tuning of field effect transistors. Depth profiling with medium energy ion scattering shows that an initial surface layer of La2O3 diffuses through the HfO2 at elevated temperatures, ultimately converting some of the thin interfacial SiO2 into a silicate. Core-level photoemission measurements indicate that the additional band-bending induced by the La2O3 only appears after diffusion, and the added charge resides between the HfO2 and the substrate.

  4. Near-field microwave microscopy of high-κ oxides grown on graphene with an organic seeding layer

    Science.gov (United States)

    Tselev, Alexander; Sangwan, Vinod K.; Jariwala, Deep; Marks, Tobin J.; Lauhon, Lincoln J.; Hersam, Mark C.; Kalinin, Sergei V.

    2013-12-01

    Near-field scanning microwave microscopy (SMM) is used for non-destructive nanoscale characterization of Al2O3 and HfO2 films grown on epitaxial graphene on SiC by atomic layer deposition using a self-assembled perylene-3,4,9,10-tetracarboxylic dianhydride seeding layer. SMM allows imaging of buried inhomogeneities in the dielectric layer with a spatial resolution close to 100 nm. The results indicate that, while topographic features on the substrate surface cannot be eliminated as possible sites of defect nucleation, the use of a vertically heterogeneous Al2O3/HfO2 stack suppresses formation of large outgrowth defects in the oxide film, ultimately improving lateral uniformity of the dielectric film.

  5. Interface engineered HfO2-based 3D vertical ReRAM

    Science.gov (United States)

    Hudec, Boris; Wang, I.-Ting; Lai, Wei-Li; Chang, Che-Chia; Jančovič, Peter; Fröhlich, Karol; Mičušík, Matej; Omastová, Mária; Hou, Tuo-Hung

    2016-06-01

    We demonstrate a double-layer 3D vertical resistive random access memory (ReRAM) stack implementing a Pt/HfO2/TiN memory cell. The HfO2 switching layer is grown by atomic layer deposition on the sidewall of a SiO2/TiN/SiO2/TiN/SiO2 multilayer pillar. A steep vertical profile was achieved using CMOS-compatible TiN dry etching. We employ in situ TiN bottom interface engineering by ozone, which results in (a) significant forming voltage reduction which allows for forming-free operation in AC pulsed mode, and (b) non-linearity tuning of low resistance state by current compliance during Set operation. The vertical ReRAM shows excellent read and write disturb immunity between vertically stacked cells, retention over 104 s and excellent switching stability at 400 K. Endurance of 107 write cycles was achieved using 100 ns wide AC pulses while fast switching speed using pulses of only 10 ns width is also demonstrated. The active switching region was evaluated to be located closer to the bottom interface which allows for the observed high endurance.

  6. Barium Ferrite Films Grown by Laser Ablation

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.; Haan, de P.; Smithers, M.A.; Roesthuis, F.J.G.

    1998-01-01

    Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al2O3 single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe12O19 phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic a

  7. HfO2 Gate Dielectrics for Future Generation of CMOS Device Application

    Institute of Scientific and Technical Information of China (English)

    H.Y.Yu; J.F.Kang; Ren Chi; M.F.Li; D.L.Kwong

    2004-01-01

    The material and electrical properties of HfO2 high-k gate dielectric are reported.In the first part,the band alignment of HfO2 and (HfO2)x(Al2O3)1-x to (100)Si substrate and their thermal stability are studied by X-ray photoelectron spectroscopy and TEM.The energy gap of (HfO2)x(Al2O3)1-x,the valence band offset,and the conduction band offset between (HfO2)x(Al2O3)1-x and the Si substrate as functions of x are obtained based on the XPS results.Our XPS results also demonstrate that both the thermal stability and the resistance to oxygen diffusion of HfO2 are improved by adding Al to form Hf aluminates.In the second part,a thermally stable and high quality HfN/HfO2 gate stack is reported.Negligible changes in equivalent oxide thickness (EOT),gate leakage,and work function (close to Si mid-gap) of HfN/HfO2 gate stack are demonstrated even after 1000℃ post-metal annealing(PMA),which is attributed to the superior oxygen diffusion barrier of HfN as well as the thermal stability of the HfN/HfO2 interface.Therefore,even without surface nitridation prior to HfO2 deposition,the EOT of HfN/HfO2 gate stack has been successfully scaled down to less than 1nm after 1000℃ PMA with excellent leakage and long-term reliability.The last part demonstrates a novel replacement gate process employing a HfN dummy gate and sub-1nm EOT HfO2 gate dielectric.The excellent thermal stability of the HfN/HfO2 gate stack enables its use in high temperature CMOS processes.The replacement of HfN with other metal gate materials with work functions adequate for n- and p-MOS is facilitated by a high etch selectivity of HfN with respect to HfO2,without any degradation to the EOT,gate leakage,or TDDB characteristics of HfO2.

  8. SERS-applicable silver nanoisland film grown under protective coating

    Science.gov (United States)

    Reduto, I.; Chervinskii, S.; Matikainen, A.; Baklanov, A.; Kamenskii, A.; Lipovskii, A.

    2014-10-01

    We have used recently developed out-diffusion technique of growing silver nanoisland films on glass surface to grow silver nanoislands under TiO2 layer deposited on the glass. After covering the surface of silver ion-exchanged glasses with TiO2 film using atomic layer deposition technique and subsequent thermal processing of the samples in hydrogen their optical absorption spectra demonstrate the absorption peak corresponding to surface plasmon resonance in grown silver nanoislands. The spectral position of the peak is shifted relatively to the peak observed in the spectra of the nanoisland film grown on the surface of ion exchanged and annealed glass samples without dielectric cover. The applicability of the silver nanoislands grown under several nm thick protective TiO2 coating in surface-enhanced Raman scattering spectroscopy is demonstrated.

  9. Morphology in electrochemically grown conducting polymer films

    Science.gov (United States)

    Rubinstein, Israel; Gottesfeld, Shimshon; Sabatani, Eyal

    1992-01-01

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventioonally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol.

  10. Elastic and vibrational properties of monoclinic HfO2 from first-principles study

    Science.gov (United States)

    Wu, Rui; Zhou, Bo; Li, Qian; Jiang, ZhenYi; Wang, WenBo; Ma, WenYan; Zhang, XiaoDong

    2012-03-01

    The elastic and vibrational properties of crystalline monoclinic HfO2 have been investigated using density functional perturbation theory. Using the Voigt and Reuss theory, we estimate the bulk, shear and Young's modulus for polycrystalline HfO2, which agree very well with the available experimental and theoretical data. Additionally, we present a systematic analysis of the elastic properties of HfO2 polymorphs and find the trends in the elastic parameters for the HfO2 structures are consistent with those for the ZrO2 structures. The choice of exchange-correlation functional has an important effect on the results of elastic and vibrational properties. The utilization of Hartwigzen-Goedecker-Hutter type functional is a great improvement on calculation of the zone-centre phonon frequencies, and shows the root-mean-square absolute deviation of 7 cm-1 with experiments. A rigorous assignment of all the Raman modes is achieved by combining symmetry analysis with the first-principles calculations, which helps us to identify the main peak and some other features of Raman spectra. Furthermore, the Raman spectrum of HfO2 powder has been simulated for the first time, providing a theoretical benchmark for the interpretation of the unresolved problems in experimental studies.

  11. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

    OpenAIRE

    Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Nripendra N. Halder; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

    2015-01-01

    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectivene...

  12. Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

    Institute of Scientific and Technical Information of China (English)

    Han De-Dong; Kang Jin-Feng; Liu Xiao-Yan; Sun Lei; Luo Hao; Han Ru-Qi

    2007-01-01

    This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated.Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.

  13. InSb thin films grown by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: joginderchauhan82@gmail.com; Rajaram, P., E-mail: joginderchauhan82@gmail.com [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2014-04-24

    We have grown InSb thin films on Cu substrates using the electrodeposition technique. The electrochemical bath from which the InSb thin films were grown was made up of a mixture of aqueous solutions of 0.05 M InCl{sub 3} and 0.03M SbCl{sub 3}, 0 .20M citric acid and 0.30M sodium citrate. Citric acid and sodium citrate were used as complexing agents to bring the reduction potential of In and Sb closer to maintain binary growth. The electrodeposited films were characterized by structural, morphological and optical studies. X-ray diffraction studies show that the films are polycrystalline InSb having the zinc blende structure. Scanning electron microscopy (SEM) studies reveal that the surface of the films is uniformly covered with submicron sized spherical particles. FTIR spectra of InSb thin films show a sharp absorption peak at wave number 1022 cm{sup −1} corresponding to the band gap. Hot probe analysis shows that the InSb thin films have p type conductivity.

  14. Effects of NH3 annealing on interface and electrical properties of Gd-doped HfO2/Si stack

    Institute of Scientific and Technical Information of China (English)

    YANG Mengmeng; TU Hailing; DU Jun; WEI Feng; XIONG Yuhua; ZHAO Hongbin

    2013-01-01

    Effects of NH3 rapid thermal annealing (RTA) on the interface and electrical properties of Gd-doped HfO2 (GDH)/Si stack were investigated.The process of NH3 annealing could significantly affect the crystallization,stoichiometric properties of GDH film and the interface characteristic of GDH/Si system.NH3 annealing also led to the decrease of interface layer thickness.The leakage current density of Pt/GDH/p-Si MOS capacitor without RTA was 2× 10-3 A/cm2.After NH3 annealing,the leakage current density was about one order of magnitude lower (3.9×10-4 A/cm2).The effective permittivity extracted from the C-V curves was ~14.1 and ~13.1 for samples without and with RTA,respectively.

  15. Thermally grown thin nitride films as a gate dielectric

    CERN Document Server

    Shin, H C; Hwang, T K; Lee, K R

    1998-01-01

    High-quality very thin films ( <=6 nm) of silicon nitride were thermally grown in ammonia atmosphere with an IR (Infrared) gold image furnace. As-grown nitride film was analyzed using AES(Auger Emission Spectroscopy). Using MIS (Metal-Insulator-Semiconductor) devices, the growth rate was calculated using CV (Capacitance-Voltage) measurements and various electrical characteristics were obtained using CV, IV (Current-Voltage), trapping, time-dependent breakdown, high-field stress, constant current injection stress and dielectric breakdown techniques. These characteristics showed that very thin thermal silicon nitride films can be used as gate dielectrics for future highly scaled-down ULSI (Ultra Large Scale Integrated) devices, especially for EEPROM (Electrically Erasable and Programmable ROM)'s.

  16. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    Science.gov (United States)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  17. Epitaxial yttrium iron garnet films grown by pulsed laser deposition

    Science.gov (United States)

    Dorsey, P. C.; Bushnell, S. E.; Seed, R. G.; Vittoria, C.

    1993-07-01

    Epitaxial Y3Fe5O12 (YIG) films have been grown by the pulsed laser deposition (PLD) technique on (111) gadolinium gallium garnet substrates. The effect of substrate temperature and oxygen partial pressure on the structure, composition, and magnetic properties of the films was investigated and compared to liquid phase epitaxy YIG films. The results demonstrated that epitaxial YIG films could be prepared under a wide range of deposition conditions, but narrow linewidth (ΔH≂1 Oe) films were producible only at low oxygen partial pressures (O2temperatures (Ts≳800 °C). Since the linewidth of single-crystal YIG is dominated by surface and volume defects and/or impurities, the narrow linewidth indicated that PLD is a viable technique for producing high-quality ferrite films for microwave device applications. In addition, under all deposition conditions (50-1000 mTorr and 700-850 °C) there is a uniaxial axis perpendicular to the film plane. However, at low oxygen pressure the uniaxial anisotropy energy constant Ku is negative while at high oxygen pressure Ku is positive.

  18. Enhancement of the blue photoluminescence intensity for the porous silicon with HfO2 filling into microcavities

    Science.gov (United States)

    Jiang, Ran; Du, Xianghao; Sun, Weideng; Han, Zuyin; Wu, Zhengran

    2015-10-01

    With HfO2 filled into the microcavities of the porous single-crystal silicon, the blue photoluminescence was greatly enhanced at room temperature. On one hand, HfO2 contributes to the light emission with the transitions of the defect levels for oxygen vacancy. On the other hand, the special filling-into-microcavities structure of HfO2 leads to the presence of ferroelectricity, which greatly enhances the blue emission from porous silicon. Since both HfO2 and Si are highly compatible with Si-based electronic industry, combined the low-cost and convenient process, the HfO2-filled porous Si shows a promising application prospect.

  19. Ferroelectricity in Si-doped HfO2 revealed: a binary lead-free ferroelectric.

    Science.gov (United States)

    Martin, Dominik; Müller, Johannes; Schenk, Tony; Arruda, Thomas M; Kumar, Amit; Strelcov, Evgheni; Yurchuk, Ekaterina; Müller, Stefan; Pohl, Darius; Schröder, Uwe; Kalinin, Sergei V; Mikolajick, Thomas

    2014-12-23

    Static domain structures and polarization dynamics of silicon doped HfO2 are explored. The evolution of ferroelectricity as a function of Si-doping level driving the transition from paraelectricity via ferroelectricity to antiferroelectricity is investigated. Ferroelectric and antiferroelectric properties can be observed locally on the pristine, poled and electroded surfaces, providing conclusive evidence to intrinsic ferroic behavior.

  20. Optical properties of nanocrystalline HfO2 synthesized by an auto-igniting combustion synthesis

    Directory of Open Access Journals (Sweden)

    H. Padma Kumar

    2015-03-01

    Full Text Available The optical properties of nanocrystalline HfO2 synthesized using a single-step auto-igniting combustion technique is reported. Nanocrystalline hafnium oxide having particle size of the order 10–15 nm were obtained in the present method. The nanopowder was characterized using X-ray diffraction, Fourier transform infrared and Fourier transform Raman spectroscopic studies. All these studies confirm that the phase formation is complete in the combustion synthesis and monoclinic phase [P21/c(14] of HfO2 is obtained without the presence of any impurities or additional phases. The powder morphology of the as-prepared sample was studied using transmission electron microscopy and the results were in good agreement with that of the X-ray diffraction studies. The optical constants such as refractive index, extinction coefficient, optical conductivity and the band gap were estimated from UV–vis spectroscopic techniques. The band gap of nanocrystalline HfO2 was found to be 5.1 eV and the sample shows a broad PL emission at 628 nm. It is concluded that the transitions between intermediate energy levels in the band gap are responsible for the interesting photoluminescent properties of nanocrystalline HfO2.

  1. Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

  2. The conduction bands of MgO, MgS and HfO2

    NARCIS (Netherlands)

    Boer, P.K. de; Groot, R.A. de

    1998-01-01

    Electronic structure calculations for MgO, MgS and HfO2 are reported. It is shown that the conduction bands of MgO and MgS have predominantly anion character, contrary to the common picture of the conduction band being derived from cation states. In transition metal oxides, unoccupied anion states a

  3. Retention loss in the ferroelectric (SrBi2Ta2O9)-insulator (HfO2)-silicon structure studied by piezoresponse force microscopy

    Science.gov (United States)

    Zhang, Z. H.; Zhong, X. L.; Zhang, Y.; Wang, J. B.; Lu, C. J.; Ye, W. N.; Zhou, Y. C.

    2012-04-01

    Metal-ferroelectric-insulator-silicon (MFIS) structures with SrBi2Ta2O9 as ferroelectric thin film and HfO2 as insulating buffer layer were fabricated by pulsed-laser deposition. The interfaces and memory window of the MFIS structure were investigated. Piezoresponse force microscopy was used to observe the change of domain images in order to investigate the retention characteristics, which demonstrated that the MFIS structure experiences retention loss via a random-walk-type process, identified by a stretched exponential-decay model. The corresponding mechanism was discussed based on the time-dependent depolarization field.

  4. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

    Science.gov (United States)

    Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

    2015-02-01

    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~106 s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology.

  5. Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

    Science.gov (United States)

    Niu, Gang; Kim, Hee-Dong; Roelofs, Robin; Perez, Eduardo; Schubert, Markus Andreas; Zaumseil, Peter; Costina, Ioan; Wenger, Christian

    2016-06-01

    With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.

  6. Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition.

    Science.gov (United States)

    Niu, Gang; Kim, Hee-Dong; Roelofs, Robin; Perez, Eduardo; Schubert, Markus Andreas; Zaumseil, Peter; Costina, Ioan; Wenger, Christian

    2016-06-17

    With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.

  7. Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

    Science.gov (United States)

    Niu, Gang; Kim, Hee-Dong; Roelofs, Robin; Perez, Eduardo; Schubert, Markus Andreas; Zaumseil, Peter; Costina, Ioan; Wenger, Christian

    2016-01-01

    With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption. PMID:27312225

  8. Atomic-layer-deposited Al2O3 and HfO2 on InAlAs: A comparative study of interfacial and electrical characteristics

    Science.gov (United States)

    Wu, Li-Fan; Zhang, Yu-Ming; Lv, Hong-Liang; Zhang, Yi-Men

    2016-10-01

    Al2O3 and HfO2 thin films are separately deposited on n-type InAlAs epitaxial layers by using atomic layer deposition (ALD). The interfacial properties are revealed by angle-resolved x-ray photoelectron spectroscopy (AR-XPS). It is demonstrated that the Al2O3 layer can reduce interfacial oxidation and trap charge formation. The gate leakage current densities are 1.37 × 10-6 A/cm2 and 3.22 × 10-6 A/cm2 at +1 V for the Al2O3/InAlAs and HfO2/InAlAs MOS capacitors respectively. Compared with the HfO2/InAlAs metal-oxide-semiconductor (MOS) capacitor, the Al2O3/InAlAs MOS capacitor exhibits good electrical properties in reducing gate leakage current, narrowing down the hysteresis loop, shrinking stretch-out of the C-V characteristics, and significantly reducing the oxide trapped charge (Q ot) value and the interface state density (D it). Project supported by the National Basic Research Program of China (Grant No. 2010CB327505), the Advanced Research Foundation of China (Grant No. 914xxx803-051xxx111), the National Defense Advance Research Project, China (Grant No. 513xxxxx306), the National Natural Science Foundation of China (Grant No. 51302215), the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 14JK1656), and the Science and Technology Project of Shaanxi Province, China (Grant No. 2016KRM029).

  9. Formation and disruption of conductive filaments in a HfO2/TiN structure

    Science.gov (United States)

    Brivio, S.; Tallarida, G.; Cianci, E.; Spiga, S.

    2014-09-01

    The process of the formation and disruption of nanometric conductive filaments in a HfO2/TiN structure is investigated by conductive atomic force microscopy. The preforming state evidences nonhomogeneous conduction at high fields through conductive paths, which are associated with pre-existing defects and develop into conductive filaments with a forming procedure. The disruption of the same filaments is demonstrated as well, according to a bipolar operation. In addition, the conductive tip of the microscopy is exploited to perform electrical operations on single conductive spots, which evidences that neighboring conductive filaments are not electrically independent. We propose a picture that describes the evolution of the shape of the conductive filaments in the processes of their formation and disruption, which involves the development of conductive branches from a common root; this root resides in the pre-existing defects that lay at the HfO2/TiN interface.

  10. Stable tetragonal phase and magnetic properties of Fe-doped HfO2 nanoparticles

    Directory of Open Access Journals (Sweden)

    T. S. N. Sales

    2017-05-01

    Full Text Available In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2 nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM with electron back scattering diffraction (EBSD, and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%.

  11. Epitaxial SrO interfacial layers for HfO2-Si gate stack scaling

    Science.gov (United States)

    Marchiori, C.; Frank, M. M.; Bruley, J.; Narayanan, V.; Fompeyrine, J.

    2011-01-01

    We discuss the structural and electrical properties of scaled 2 nm HfO2/SrO gate stacks. Thin SrO layers are deposited by molecular beam epitaxy onto (001) p-Si substrates as alternative passivating interfacial layers (ILs) to SiO2. X-ray photoelectron spectroscopy and transmission electron microscopy show that, despite some HfO2-SrO intermixing, the SrO IL acts as a barrier against HfxSiy and SiO2 formation during high-κ deposition. Electrical measurements on metal-oxide-semiconductor capacitors with TiN metal gates integrated in a low-temperature process flow reveal an equivalent oxide thickness of 5 Å with competitive leakage current and hysteresis and a negative flat band voltage shift, suitable for n-channel transistors.

  12. Comparison of HfAlO, HfO2/Al2O3, and HfO2 on n-type GaAs using atomic layer deposition

    Science.gov (United States)

    Lu, Bin; Lv, Hongliang; Zhang, Yuming; Zhang, Yimen; Liu, Chen

    2016-11-01

    Different high-permittivity (high-k) gate dielectric structures of HfO2, HfAlO, and HfO2/Al2O3 deposited on HF-etched n-GaAs using ALD have been investigated. It has been demonstrated that the stacked structure of HfO2/Al2O3 has the lowest interface state density of 8.12 × 1012eV-1 cm-2 due to the "self-cleaning" reaction process, but the sample of HfAlO shows much better frequency dispersion and much higher dielectric permittivity extracted from the C-V curves. The investigation reveals that the electrical properties of gate dielectrics are improved by introducing alumina into HfO2.

  13. Design and Fabrication of Interdigital Nanocapacitors Coated with HfO2

    Directory of Open Access Journals (Sweden)

    Gabriel González

    2015-01-01

    Full Text Available In this article nickel interdigital capacitors were fabricated on top of silicon substrates. The capacitance of the interdigital capacitor was optimized by coating the electrodes with a 60 nm layer of HfO2. An analytical solution of the capacitance was compared to electromagnetic simulations using COMSOL and with experimental measurements. Results show that modeling interdigital capacitors using Finite Element Method software such as COMSOL is effective in the design and electrical characterization of these transducers.

  14. Design and Fabrication of Interdigital Nanocapacitors Coated with HfO2

    Science.gov (United States)

    González, Gabriel; Kolosovas-Machuca, Eleazar Samuel; López-Luna, Edgar; Hernández-Arriaga, Heber; González, Francisco Javier

    2015-01-01

    In this article nickel interdigital capacitors were fabricated on top of silicon substrates. The capacitance of the interdigital capacitor was optimized by coating the electrodes with a 60 nm layer of HfO2. An analytical solution of the capacitance was compared to electromagnetic simulations using COMSOL and with experimental measurements. Results show that modeling interdigital capacitors using Finite Element Method software such as COMSOL is effective in the design and electrical characterization of these transducers. PMID:25602271

  15. Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region

    Science.gov (United States)

    Winkowski, P.; Marszałek, Konstanty W.

    2013-07-01

    Deposition technology of the three layers antireflective coatings consists of hafnium compound are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5x10-5 mbar in presence of oxygen and fluoride films by thermal evaporation. Substrate temperature was 250°C. Coatings were deposited onto optical lenses made from quartz glass (Corning HPFS). Thickness and deposition rate were controlled by thickness measuring system Inficon XTC/2. Simulations leading to optimization of thickness and experimental results of optical measurements carried during and after deposition process were presented. Physical thickness measurements were made during deposition process and were equal to 43 nm/74 nm/51 nm for Al2O3 / HfO2 / MgF2 respectively. Optimization was carried out for ultraviolet region from 230nm to the beginning of visible region 400 nm. In this region the average reflectance of the antireflective coating was less than 0.5% in the whole range of application.

  16. Structure and Optical Properties of Nanocrystalline Hafnium Oxide Thin Films (PostPrint)

    Science.gov (United States)

    2014-09-01

    AFRL-RX-WP-JA-2014-0214 STRUCTURE AND OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) Neil R. Murphy AFRL...OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...publication is available at http://dx.doi.org/10.1016/j.optmat.2014.08.005 14. ABSTRACT Hafnium oxide (HfO2) films were grown by sputter-deposition by

  17. Determination of complex dielectric functions at HfO(2)/Si interface by using STEM-VEELS.

    Science.gov (United States)

    Park, Jucheol; Yang, Mino

    2009-04-01

    The complex dielectric functions and refractive index of atomic layer deposited HfO(2) were determined by the line scan method of the valence electron energy loss spectrum (VEELS) in a scanning transmission electron microscope (STEM). The complex dielectric functions and dielectric constant of monoclinic HfO(2) were calculated by the density functional theory (DFT) method. The resulting two dielectric functions were relatively well matched. On the other hand, the refractive index of HfO(2) was measured as 2.18 by VEELS analysis and 2.1 by DFT calculation. The electronic structure of HfO(2) was revealed by the comparison of the inter-band transition strength, obtained by STEM-VEELS, with the density of states (DOS) calculated by DFT calculation.

  18. The Hydrothermal Autoclave Synthesis of the Nanopowders of the Refractory ZrO2 and HfO2 Oxides

    Directory of Open Access Journals (Sweden)

    N.F. Karpovich

    2015-12-01

    Full Text Available The nanopowders of the transition metal ZrO2 and HfO2 oxides were obtained by the hydrothermal autoclave synthesis. The nanoparticles possess a rounded shape and a size range of 40 to 80 nm (ZrO2, of 10 to 40 nm (HfO2. X-ray diffraction analysis and electron microscopy show that the structure of the nanoparticles is monoclinic.

  19. Electrical characteristics of multilayered HfO2-Al2O3 charge trapping stacks deposited by ALD

    Science.gov (United States)

    Spassov, D.; Paskaleva, A.; Guziewicz, E.; Luka, G.; AKrajewski, T.; Kopalko, K.; Wierzbicka, A.; Blagoev, B.

    2016-10-01

    Electrical and charge trapping properties of atomic layer deposited HfO2-Al2O3 multilayer stacks with two different Al2O3 sublayer thicknesses were investigated regarding their implementation in charge trapping non-volatile memories. The effect of post deposition annealing in oxygen at 600°C is also studied. The decreasing Al2O3 thickness increases the stack's dielectric constant and the density of the initial positive oxide charge. The initial oxide charge increases after annealing to ∼6×1012 cm-2 and changes its sign to negative for the stacks with thicker Al2O3. The annealing enhances the dielectric constant of the stacks and reduces their thickness preserving the amorphous status. Nevertheless the annealing is not beneficial for the stacks with thicker Al2O3 as it considerably increases leakage currents. Conduction mechanisms in stacks were considered in terms of hopping conduction at low electric fields, and Fowler- Nordheim tunnelling, Schottky emission and Poole-Frenkel effect at higher ones. Maximum memory windows of about 12 and 16V were obtained for the as-grown structures with higher and lower Al2O3 content, respectively. In latter case additional improvement (the memory window increase up to 23V) is achieved by the annealing.

  20. A combined ab initio and Franck-Condon factor simulation study on the photodetachment spectrum of HfO2-.

    Science.gov (United States)

    Mok, Daniel K W; Lee, Edmond P F; Chau, Foo-Tim; Dyke, John M

    2008-12-28

    Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the X[combining tilde]1A1 state of HfO2 and the X[combining tilde]2A1 state of HfO2- were computed, employing the quasi-relativistic effective core potential, ECP60MWB, and an associated contracted [13s6p6d4f3g2h] basis set designed for Hf, and the augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set for O. Based on the differences between the computed r0 and re geometrical parameters obtained from the PEF, and available experimentally derived r0 geometrical parameters of the X[combining tilde]1A1 state of HfO2, the experimental re geometrical parameters of the X[combining tilde]1A1 state of HfO2 were estimated as:-re(HfO)=1.7751 A and thetae(OHfO)=107.37 degrees. In addition, Franck-Condon factors for the HfO2 (X[combining tilde]1A1)+eVDEs) to these neutral states from the X[combining tilde]2A1 state of HfO2-.

  1. Memory Effect of Metal-Oxide-Silicon Capacitors with Self-Assembly Double-Layer Au Nanocrystals Embedded in Atomic-Layer-Deposited HfO_2 Dielectric

    Institute of Scientific and Technical Information of China (English)

    HUANG Yue; GOU Hong-Yan; SUN Qing-Qing; DING Shi-Jin; ZHANG Wei; ZHANG Shi-Li

    2009-01-01

    We report the chemical self-assembly growth of Au nanocrystals on atomic-layer-deposited HfO_2 films aminosilanized by (3-Aminopropyl)-trimethoxysilane aforehand for memory applications.The resulting Au nanocrystals show a density of about 4×10~(11) cm~(-2) and a diameter range of 5-8nm.The metal-oxide-silicon capacitor with double-layer Au nanocrystals embedded in HfO2 dielectric exhibits a large C - V hysteresis window of 11.9 V for ±11 V gate voltage sweeps at 1 MHz, a fiat-band voltage shift of 1.5 V after the electrical stress under 7 V for I ms, a leakage current density of 2.9 ×10~(-8) A/cm~(-2) at 9 V and room temperature.Compared to single-layer Au nanocrystals, the double-layer Au nanocrystals increase the hysteresis window significantly, and the underlying mechanism is thus discussed.

  2. Characterization of 1064nm laser-induced damage on antireflection coatings grown by atomic layer deposition

    Science.gov (United States)

    Liu, Zhichao; Wei, Yaowei; Chen, Songlin; Luo, Jin; Ma, Ping

    2011-12-01

    Damage tests were carried out to measure the laser resistance of Al2O3/TiO2 and Al2O3/HfO2 antireflection coatings at 1064nm grown by atomic layer deposition (ALD). The S-on-1 and R-on-1 damage results are given. It's interesting to find that ALD coatings damage performance seems closed to those grown by conventional e-beam evaporation process. For Al2O3/TiO2 coatings, the grown temperature will impact the damage resistance of thin films. Crystallization of TiO2 layer at higher temperature could play an importance role as absorption defects that reduced the LIDT of coatings. In addition, it is found that using inorganic compound instead of organic compound as precursors for ALD process can effective prevent residual carbon in films and will increase the LIDT of coatings.

  3. Anisotropic magnetothermopower in ferromagnetic thin films grown on macroscopic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jayathilaka, P.B. [Department of Physical Sciences, Faculty of Applied Sciences, Rajarata University of Sri Lanka, Mihintale (Sri Lanka); Belyea, D.D. [Department of Physics, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620 (United States); Fawcett, T.J. [College of Engineering, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620 (United States); Miller, Casey W. [School of Chemistry and Materials Science, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2015-05-15

    We report observing the anisotropic magnetothermopower in a variety of ferromagnetic thin films grown on macroscopic substrates. These measurements were enabled by eliminating spurious signals related to the Anomalous Nernst Effect by butt-mounting the sample to the heat source and sink, and appropriate positioning of electrical contacts to avoid unwanted thermal gradients. This protocol enabled detailed measurements of the magnetothermopower in the transverse and longitudinal configurations. This may enable Spin Seebeck Effect studies in the in-plane geometry. - Highlights: • Unintentional thermal gradients along surface normal mitigated via butt-mounting. • Longitudinal/transverse magnetothermopower measured on many systems. • Anomalous Nernst Effect reduced. • Importance of magnetic anisotropy identified with angle-dependent measurements.

  4. Ferroelectric Properties of Pt/Pb5Ge3O11/Pt and Pt/Pb5Ge3O11/HfO2/Si Structures

    Science.gov (United States)

    Ohara, Shuichiro; Aizawa, Koji; Ishiwara, Hiroshi

    2005-09-01

    The ferroelectric properties of metal-ferroelectric-metal (MFM) capacitors with a Pt/Pb5Ge3O11(PGO)/Pt structure and metal-ferroelectric-insulator-semiconductor (MFIS) diodes with a Pt/PGO/HfO2/Si structure were investigated. C-axis-oriented PGO thin films were formed on both Pt/SiO2/Si and HfO2 (6 nm)/Si structures by a sol-gel method. Typical values of remanent polarization (2Pr), coercive field (2Ec), and dielectric constant in the MFM capacitors were 5.7 μC/cm2, 63 kV/cm, and 50, respectively, and the remanent polarization gradually increased with the switching pulses for up to 1 × 1010 cycles. It was also found that the memory window in the MFIS diodes with a 340-nm-thick PGO film was as large as 1.3 V.

  5. Bipolar Resistive Switching Characteristics of HfO2/TiO2/HfO2 Trilayer-Structure RRAM Devices on Pt and TiN-Coated Substrates Fabricated by Atomic Layer Deposition

    Science.gov (United States)

    Zhang, Wei; Kong, Ji-Zhou; Cao, Zheng-Yi; Li, Ai-Dong; Wang, Lai-Guo; Zhu, Lin; Li, Xin; Cao, Yan-Qiang; Wu, Di

    2017-06-01

    The HfO2/TiO2/HfO2 trilayer-structure resistive random access memory (RRAM) devices have been fabricated on Pt- and TiN-coated Si substrates with Pt top electrodes by atomic layer deposition (ALD). The effect of the bottom electrodes of Pt and TiN on the resistive switching properties of trilayer-structure units has been investigated. Both Pt/HfO2/TiO2/HfO2/Pt and Pt/HfO2/TiO2/HfO2/TiN exhibit typical bipolar resistive switching behavior. The dominant conduction mechanisms in low and high resistance states (LRS and HRS) of both memory cells are Ohmic behavior and space-charge-limited current, respectively. It is found that the bottom electrodes of Pt and TiN have great influence on the electroforming polarity preference, ratio of high and low resistance, and dispersion of the operating voltages of trilayer-structure memory cells. Compared to using symmetric Pt top/bottom electrodes, the RRAM cells using asymmetric Pt top/TiN bottom electrodes show smaller negative forming voltage of -3.7 V, relatively narrow distribution of the set/reset voltages and lower ratio of high and low resistances of 102. The electrode-dependent electroforming polarity can be interpreted by considering electrodes' chemical activity with oxygen, the related reactions at anode, and the nonuniform distribution of oxygen vacancy concentration in trilayer-structure of HfO2/TiO2/HfO2 on Pt- and TiN-coated Si. Moreover, for Pt/HfO2/TiO2/HfO2/TiN devices, the TiN electrode as oxygen reservoir plays an important role in reducing forming voltage and improving uniformity of resistive switching parameters.

  6. Structure and Morphology of Phthalocyanine Films Grown in Electrical Fields by Vapor Deposition

    Science.gov (United States)

    Zhu, Shen; Banks, C. E.; Frazier, D. O.; Penn, B.; Abdeldayem, H.; Hicks, R.; Burns, H. D.; Thompson, G. W.

    1999-01-01

    Phthalocyanine (Pc) films have been synthesized by vapor deposition on quartz substrates, some of which were coated with a very thin gold film before depositing Pc films. Electrical fields up to 6200 V/cm between a mech electrode and the substrate are introduced during film growth. These films have been characterized by x-ray diffraction and scanning electron microscopy. The molecular orientations and surface morphology of Pc films were changed under the electrical fields. The surface of these films grown without electrical field shows whisk-like morphology. When films are deposited under an electrical field, a dense film with flat surface is obtained.

  7. HfO 2 -based ferroelectric modulator of terahertz waves with graphene metamaterial

    Science.gov (United States)

    Jiang, Ran; Wu, Zheng-Ran; Han, Zu-Yin; Jung, Hyung-Suk

    2016-10-01

    Tunable modulations of terahertz waves in a graphene/ferroelectric-layer/silicon hybrid structure are demonstrated at low bias voltages. The modulation is due to the creation/elimination of an extra barrier in Si layer in response to the polarization in the ferroelectric Si:HfO2 layer. Considering the good compatibility of HfO2 with the Si-based semiconductor process, the highly tunable characteristics of the graphene metamaterial device under ferroelectric effect open up new avenues for graphene-based high performance integrated active photonic devices compatible with the silicon technology. Project supported by the National Natural Science Foundation of China (Grant No. 11374182).

  8. Morphology and Photoluminescence of HfO2Obtained by Microwave-Hydrothermal

    Directory of Open Access Journals (Sweden)

    Cavalcante LS

    2009-01-01

    Full Text Available Abstract In this letter, we report on the obtention of hafnium oxide (HfO2 nanostructures by the microwave-hydrothermal method. These nanostructures were analyzed by X-ray diffraction (XRD, field-emission gum scanning electron microscopy (FEG-SEM, transmission electron microscopy (TEM, energy dispersive X-ray spectrometry (EDXS, ultraviolet–visible (UV–vis spectroscopy, and photoluminescence (PL measurements. XRD patterns confirmed that this material crystallizes in a monoclinic structure. FEG-SEM and TEM micrographs indicated that the rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing. The EDXS spectrum was used to verify the chemical compositional of this oxide. UV–vis spectrum revealed that this material have an indirect optical band gap. When excited with 488 nm wavelength at room temperature, the HfO2nanostructures exhibited only one broad PL band with a maximum at around 548 nm (green emission.

  9. Theoretical prediction of ion conductivity in solid state HfO2

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei; Chen Wen-Zhou; Sun Jiu-Yu; Jiang Zhen-Yi

    2013-01-01

    A theoretical prediction of ion conductivity for solid state HfO2 is carried out in analogy to ZrO2 based on the density functional calculation.Geometric and electronic structures of pure bulks exhibit similarity for the two materials.Negative formation enthalpy and negative vacancy formation energy are found for YSH (yttria-stabilized hafnia) and YSZ (yttriastabilized zirconia),suggesting the stability of both materials.Low activation energies (below 0.7 eV) of diffusion are found in both materials,and YSH's is a little higher than that of YSZ.In addition,for both HfO2 and ZrO2,the supercells with native oxygen vacancies are also studied.The so-called defect states are observed in the supercells with neutral and +1 charge native vacancy but not in the +2 charge one.It can give an explanation to the relatively lower activation energies of yttria-doped oxides and +2 charge vacancy supercells.A brief discussion is presented to explain the different YSH ion conductivities in the experiment and obtained by us,and we attribute this to the different ion vibrations at different temperatures.

  10. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  11. Ferromagnetism and increased ionicity in epitaxially grown TbMnO3 films

    NARCIS (Netherlands)

    Rubi, D.; de Graaf, C.; Daumont, C. J. M.; Mannix, D.; Broer, R; Noheda, B

    2009-01-01

    Thin films of TbMnO3 have been grown on SrTiO3 substrates. The films grow under compressive strain and are only partially clamped to the substrate. This produces remarkable changes in the magnetic properties and, unlike the bulk material, the films display ferromagnetic interactions below the orderi

  12. Influence of Ti substitution on the electrical properties of metal-ferroelectric (BiFeO3)-insulator (HfO2)-silicon structures for nonvolatile memory applications

    Science.gov (United States)

    Pi-Chun Juan, Trevor; Liu, Yu-Wei

    2011-05-01

    Metal-ferroelectric (Ti-substituted BiFeO3)-insulator (HfO2)-semiconductor structures have been fabricated via the cosputtering technique. Ti4+ substitution at the Fe site was investigated through x-ray photoelectron spectra and x-ray diffraction patterns at postannealing temperatures of 500 to 700 °C. The capacitance-voltage memory windows as functions of the insulator film thickness and the dc power for Ti were measured and compared. A memory window of 3.1 V was obtained at a sweep voltage of 8 V under O2-rich conditions. The leakage current and the charge injection effect, especially gate injection, can be greatly improved by Ti substitution. The effects of the postannealing temperature and the substitution amount on the leakage current can be well explained by the defect reaction model.

  13. Electrical properties and reliability of HfO2 gate-dielectric MOS capacitors with trichloroethylene surface pretreatment

    Institute of Scientific and Technical Information of China (English)

    Xu Jing-Ping; Chen Wei-Bing; Lai Pui-To; Li Yan-Ping; Chan Chu-Lok

    2007-01-01

    Trichloroethylene (TCE) pretreatment of Si surface prior to HfO2 deposition is employed to fabricate HfO2 gatedielectric MOS capacitors. Influence of this processing procedure on interlayer growth, HfO2/Si interface properties,gate-oxide leakage and device reliability is investigated. Among the surface pretreatments in NH3, NO, N2O and TCE ambients, the TCE pretreatment gives the least interlayer growth, the lowest interface-state density, the smallest gate leakage and the highest reliability. All these improvements should be ascribed to the passivation effects of Cl2 and Hclon the structural defects in the interlayer and at the interface, and also their gettering effects on the ion contamination in the gate dielectric.

  14. Electrical and structural characterization of PLD grown CeO2–HfO2 laminated high-k gate dielectrics

    NARCIS (Netherlands)

    Karakaya, K.; Barcones, B.; Rittersma, Z.M.; Berkum, van J.G.M.; Verheijen, M.A.; Rijnders, G.; Blank, D.H.A.

    2006-01-01

    The electrical and physical properties of CeO2–HfO2 nanolaminates deposited by pulsed laser deposition (PLD) are investigated. The properties of the nanolaminates are compared with binary CeO2 and HfO2 thin films. Layers were deposited using CeO2 and HfO2 targets at substrate temperatures between 22

  15. Photoresponse properties of BaSi2 film grown on Si (100) by vacuum evaporation

    Science.gov (United States)

    Thi Trinh, Cham; Nakagawa, Yoshihiko; Hara, Kosuke O.; Takabe, Ryota; Suemasu, Takashi; Usami, Noritaka

    2016-07-01

    We have succeeded in the observation of high photoresponsivity of orthorhombic BaSi2 film grown on crystalline Si by a vacuum evaporation method, raising the prospect of its promising application in high-efficiency thin-film solar cells. Photocurrent was observed at photon energies larger than 1.28 eV, which corresponds to the band gap of evaporated BaSi2 film, indicating that the photoresponsivity originates from the BaSi2 film. The effect of the substrate temperature on the film’s properties was also investigated. The films grown at a substrate temperature larger than 500 °C are single-phase polycrystalline BaSi2 films, while those grown at a substrate temperature of 400 °C is a mixture of phases. We confirmed that undoped evaporated BaSi2 films are an n-type material with high carrier concentration. High carrier lifetime of 4.8 and 2.7 μs can be found for the films grown at 500 °C and 400 °C, respectively. BaSi2 film grown at a substrate temperature of 500 °C, which is crack-free and single-phase, shows the best photoresponsivity. The maximum value of photocurrent was obtained at photon energy of 1.9 eV, corresponding to an external quantum efficiency of 22% under reverse applied voltage of 2 V.

  16. Potential imaging of Si /HfO2/polycrystalline silicon gate stacks: Evidence for an oxide dipole

    Science.gov (United States)

    Ludeke, R.; Narayanan, V.; Gusev, E. P.; Cartier, E.; Chey, S. J.

    2005-03-01

    Surface potential profiles of the junction area of a cleaved n-Si(100)/HfO2/p +-polycrystalline silicon (poly-Si) gate stack reveal a dipole potential in the oxide, hole trapping at the HfO2/poly-Si interface, with the Fermi level ˜0.4eV below the Si conduction bandedge and enhanced and inhomogeneous hole depletion in the p +-poly-Si. The dipole accounts for band bending reduction in the n-Si and is consistent with flatband voltage shifts reported for similar gate stacks.

  17. Vapor Phase Sensing Using Metal Nanorod Thin Films Grown by Cryogenic Oblique Angle Deposition

    Directory of Open Access Journals (Sweden)

    Piyush Shah

    2013-01-01

    Full Text Available We demonstrate the chemical sensing capability of silver nanostructured films grown by cryogenic oblique angle deposition (OAD. For comparison, the films are grown side by side at cryogenic (~100 K and at room temperature (~300 K by e-beam evaporation. Based on the observed structural differences, it was hypothesized that the cryogenic OAD silver films should show an increased surface enhanced Raman scattering (SERS sensitivity. COMSOL simulation results are presented to validate this hypothesis. Experimental SERS results of 4-aminobenzenethiol (4-ABT Raman test probe molecules in vapor phase show good agreement with the simulation and indicate promising SERS applications for these nanostructured thin films.

  18. Micro-porous TiO2 thin films grown on surface of Ti substrate

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-hong; QIN Wei; JIANG Zhao-hua; HU Xin-guo; Li Qing-fen

    2004-01-01

    Microporous titanium dioxide thin films have been grown on titanium plates by the micro-plasma oxidation method with different current densities (4, 6, 10 and 14 A/dm2). X-ray diffraction, scanning electronic microscopy and UV-Vis spectrophotometry were used to characterize the films. It is found that the films grown are microporous and consist of crystalline titanium dioxide. The micropore size and the content of anatase and rutile TiO2 phase increase with the applied voltage. The relatively higher degradation efficiency for rhodamine B is obtained in the film produced with a current density of 10 A/dm2.

  19. Structural and optical properties of ZnS thin film grown by pulsed electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Hennayaka, H.M.M.N.; Lee, Ho Seong, E-mail: hs.lee@knu.ac.kr

    2013-12-02

    ZnS thin films were grown on indium–tin-oxide coated glass substrates using pulsed electrodeposition and the effect of the deposition temperature on the structural and optical properties of the ZnS films was investigated. Polycrystalline cubic ZnS films were obtained at all the deposition temperatures. At temperatures below 70 °C, less dense films were obtained and particle agglomeration was visible. On the other hand, at temperatures above 70 °C, more dense films with well-defined grains were obtained. With increasing deposition temperatures, the optical transmittance and bandgap of the ZnS films decreased. These results are attributed to the increase in the thickness of ZnS films and their particle size. The ZnS films grown at 90 °C exhibited the highly (200) preferred orientation and n-type conductivity with a wide bandgap of 3.75 eV. - Highlights: • This study describes the effect of the deposition temperature on the growth of the ZnS thin films. • ZnS thin films were grown using pulsed electrodeposition. • ZnS thin films exhibited the good crystal quality and chemical composition. • ZnS thin films exhibited n-type conductivity with a wide bandgap of 3.75 eV.

  20. Room temperature direct band gap emission characteristics of surfactant mediated grown compressively strained Ge films

    Science.gov (United States)

    Katiyar, Ajit K.; Grimm, Andreas; Bar, R.; Schmidt, Jan; Wietler, Tobias; Joerg Osten, H.; Ray, Samit K.

    2016-10-01

    Compressively strained Ge films have been grown on relaxed Si0.45Ge0.55 virtual substrates using molecular beam epitaxy in the presence of Sb as a surfactant. Structural characterization has shown that films grown in the presence of surfactant exhibit very smooth surfaces with a relatively higher strain value in comparison to those grown without any surfactant. The variation of strain with increasing Ge layer thickness was analyzed using Raman spectroscopy. The strain is found to be reduced with increasing film thickness due to the onset of island nucleation following Stranski-Krastanov growth mechanism. No phonon assisted direct band gap photoluminescence from compressively strained Ge films grown on relaxed Si0.45Ge0.55 has been achieved up to room temperature. Excitation power and temperature dependent photoluminescence have been studied in details to investigate the origin of different emission sub-bands.

  1. Coexistence of different charge states in Ta-doped monoclinic HfO2: Theoretical and experimental approaches

    DEFF Research Database (Denmark)

    Taylor, M.A.; Alonso, R.E.; Errico, L.A.

    2010-01-01

    A combination of experiments and ab initio quantum-mechanical calculations has been applied to examine hyperfine interactions in Ta-doped hafnium dioxide. Although the properties of monoclinic HfO2 have been the subject of several earlier studies, some aspects remain open. In particular, time dif...

  2. Enhanced resistive switching performance for bilayer HfO2/TiO2 resistive random access memory

    Science.gov (United States)

    Ye, Cong; Deng, Tengfei; Zhang, Junchi; Shen, Liangping; He, Pin; Wei, Wei; Wang, Hao

    2016-10-01

    We prepared bilayer HfO2/TiO2 resistive random accessory memory (RRAM) using magnetron sputtering on an ITO/PEN flexible substrate. The switching voltages (V SET and V RESET) were smaller for the Pt/HfO2/TiO2/ITO device than for a Pt/HfO2/ITO memory device. The insertion of a TiO2 layer in the switching layer was inferred to act as an oxygen reservoir to reduce the switching voltages. In addition, greatly improved uniformity was achieved, which showed the coefficient of the variations of V SET and V RESET to be 9.90% and 6.35% for the bilayer structure RRAM. We deduced that occurrence of conductive filament connection/rupture at the interface of the HfO2 and TiO2, in combination with the HfO2 acting as a virtual cathode, led to the improved uniformity. A multilevel storage capability can be obtained by varying the stop voltage in the RESET process for bilayer HfO2/TiO2 RRAM. By analyzing the current conduction mechanism, we demonstrated that the multilevel high resistance state (HRS) was attributable to the increased barrier height when the stop voltage was increased.

  3. X-ray study of chromium oxide films epitaxially grown on MgO

    NARCIS (Netherlands)

    Du, XS; Hak, S; Rogojami, OC; Hibma, T

    2004-01-01

    Chromium oxide films grown by molecular beam epitaxy on MgO (001) substrates were characterized by x-ray diffraction (XRD) and x-ray reflectivity (XRR) measurements. The absence of random oriented peaks in the theta-2theta spectra indicated that the thin films were a single phase. Reciprocal space

  4. Diamond films grown without seeding treatment and bias by hot-filament CVD system

    Science.gov (United States)

    Ali, M.; Ürgen, M.

    2012-04-01

    Diamond film growth without seeding treatment has been the subject of numerous studies. In the present study, diamond films with/without seeding treatment were grown on silicon using hot-filament chemical vapour deposition. An inexpensive and simple approach, namely, "dry ultrasonic treatment", was introduced in which full coverage of diamond film was achieved on unseeded substrate. For comparison, one substrate was seeded with 5 μm diamond particles, prior to deposition. The resulting diamond films were examined through standard characterization tools and distinct features were observed in each film. Here we present the results of uniform and high purity diamond film, free from nano-sized grains, which is grown without seeding treatment and is expected to be potential candidate for electro-optical applications, particularly as heat sinks.

  5. Effective annealing of ZnO thin films grown by three different SILAR processes

    OpenAIRE

    2015-01-01

    In the present work, zinc oxide (ZnO) thin films have been grown three different cation solution on glass substrates by a simple and economic successive ionic layer absorption and reaction method (SILAR). One of each grown different solution films was annealed to investigate to effective annealing at 473 K for 30 minutes. Absorption measurements showed that the optical band-gaps of all ZnO thin films were wide and were about 3.08-3.31 eV. All films’ band gap increased with annealing. Energy-D...

  6. Electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Pagni, O. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Somhlahlo, N.N. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Weichsel, C. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)]. E-mail: andrew.leitch@nmmu.ac.za

    2006-04-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies.

  7. Europium and samarium doped calcium sulfide thin films grown by PLD

    Science.gov (United States)

    Christoulakis, S.; Suchea, M.; Katsarakis, N.; Koudoumas, E.

    2007-07-01

    Europium and samarium doped calcium sulfide thin films (CaS:Eu,Sm) with different thickness were prepared by the pulsed laser deposition technique using sintered targets. A typical homemade deposition chamber and XeCl excimer laser (308 nm) were employed and the films were deposited in helium atmosphere onto silicon and corning glass substrates. Structural investigations carried out by X-ray diffraction and atomic force microscopy showed a strong influence of the deposition parameters on the film properties. The films grown had an amorphous or polycrystalline structure depending on growth temperature and the number of pulses used, the same parameters affecting the film roughness, the grain shape and dimensions, the film thickness and the optical transmittance. This work indicates that pulsed laser deposition can be a suitable technique for the preparation of CaS:Eu,Sm thin films, the film characteristics being controlled by the growth conditions.

  8. Single-crystal semiconductor films grown on foreign substrates

    Science.gov (United States)

    Vohl, P.

    1966-01-01

    Intermediate alloy formed between foreign substrates and semiconductor material enable the growth of single crystal semiconductor films on the alloy layer. The melted film must not ball up on the surface of the substrate and neither chemically react nor alloy with the intermediate alloy formed on the substrate.

  9. A Comparison between AlN Films Grown by MOCVD Using Dimethylethylamine Alane and Trimethylaluminium as the Aluminium Precursors

    Institute of Scientific and Technical Information of China (English)

    HU Wei-Guo; PAN Yi; LIU Xiang-Lin; ZHANG Pan-Feng; ZHAO Feng-Ai; JIAO Chun-Mei; WEI Hong-Yuan; ZHANG Ri-Qing; WU Jie-Jun; CONG Guang-Wei

    2007-01-01

    Aluminium nitride (AlN) films grown with dimethylethylamine alane (DMEAA) are compared with the ones grown with trimethylaluminium (TMA). In the high-resolution x-ray diffraction Ω scans, the full width at half maximum (FWHM) of (0002) AlN films grown with DMEAA is about 0.70 deg, while the FWHM of (0002)AlN films grown with TMA is only 0.11 deg. The surface morphologies of the films are different, and the rms roughnesses of the surface are approximately identical. The rms roughness of AlN films grown with DMEAA is 47.4 nm, and grown with TMA is 69.4 nm. Although using DMEAA as the aluminium precursor cannot improve the AlN crystal quality, AlN growth can be reached at low temperature of 673 K. Thus, DMEAA is an alternative aluminium precursor to deposit AlN film at low growth temperatures.

  10. Current Thermal Emission from Photonic Nanostructures Composed of TA, W, GE, and HFO2 Thin Films

    Science.gov (United States)

    2015-03-01

    and Manufacturing Directorate. Substrates chosen for this study consisted of p-type silicon (Si) wafers having Prime grade, 1-10 Ω resistivity, and...100) orientation. These Si wafers were obtained by AFRL from University Wafer . All of the designs will begin with a DCMS deposition technique that...Sputtering (DCMS) technique. The micrograph was taken at 20,000x magnification with 2 kV at 45° from surface normal. The surface W layer displays bumps

  11. Gas-phase reaction studies of dipositive hafnium and hafnium oxide ions: generation of the peroxide HfO2(2+).

    Science.gov (United States)

    Lourenço, Célia; Michelini, Maria del Carmen; Marçalo, Joaquim; Gibson, John K; Oliveira, Maria Conceição

    2012-12-27

    Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient. Density functional theory revealed the structure of HfO(2)(2+) as a peroxide. The HfO(2)(2+) ion reacted by electron transfer with N(2)O, CO(2), and CO to give HfO(2)(+). Estimates were made for the second ionization energies of Hf (14.5 ± 0.5 eV), HfO (14.3 ± 0.5 eV), and HfO(2) (16.2 ± 0.5 eV), and also for the bond dissociation energies, D[Hf(2+)-O] = 686 ± 69 kJ mol(-1) and D[OHf(2+)-O] = 186 ± 98 kJ mol(-1). The computed bond dissociation energies, 751 and 270 kJ mol(-1), respectively, are within these experimental ranges. Additionally, it was found that HfO(2)(2+) oxidized CO to CO(2) and is thus a catalyst in the oxidation of CO by N(2)O and that Hf(2+) activates methane to produce a carbene, HfCH(2)(2+).

  12. Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

    KAUST Repository

    Ahmed, Bilal

    2015-06-01

    It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Effect of surface treatment on hot-filament chemical vapour deposition grown diamond films

    Science.gov (United States)

    Ali, M.; Ürgen, M.; Atta, M. A.

    2012-02-01

    Diamond film growth without seeding treatment has been the subject of numerous studies. In this study, diamond films with/without seeding treatment were grown on silicon using hot-filament chemical vapour deposition. An inexpensive and simple approach, namely ‘dry ultrasonic treatment’, was introduced in which full coverage of the diamond film was achieved over the substrate having no prior seeding treatment. For comparison purposes, two substrates were seeded with different sizes of diamond particles, 5 µm by hand and 30-40 µm by ultrasonic agitation, prior to deposition. The produced diamond films were examined through standard characterization tools and distinct features were observed in each film. The diamond film grown without the seeding treatment shows slightly lower growth rate (1 µm h-1) but bigger grain size up to 8 µm compared with seeded films. Here we show the growth of uniform and high-purity diamond films free from nano-sized grains, which are grown without any seeding treatment.

  14. Enhancement of Endurance in HfO2-Based CBRAM Device by Introduction of a TaN Diffusion Blocking Layer

    KAUST Repository

    Chand, Umesh

    2017-08-05

    We propose a new method to improve resistive switching properties in HfO2 based CBRAM crossbar structure device by introducing a TaN thin diffusion blocking layer between the Cu top electrode and HfO2 switching layer. The Cu/TaN/HfO2/TiN device structure exhibits high resistance ratio of OFF/ON states without any degradation in switching during endurance test. The improvement in the endurance properties of the Cu/TaN/HfO2/TiN CBRAM device is thus attributed to the relatively low amount of Cu migration into HfO2 switching layer.

  15. Electrochromic behavior in CVD grown tungsten oxide films

    Science.gov (United States)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Dimitrova, Zl; Gesheva, K.

    1999-03-01

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thin TiO 2 film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte.

  16. Electrochromic behavior in CVD grown tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Gesheva, K.; Dimitrova, Z. [Central Laboratory for Solar Energy and New Energy Sources at Bulgarian Academy of Science, 72 Tzarigradsko shossee Blvd., Sofia (Bulgaria)

    1999-03-15

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thinTiO{sub 2} film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte

  17. Epitaxial thin films grown by pulsed laser deposition

    NARCIS (Netherlands)

    Blank, D.H.A.

    2005-01-01

    In this paper, we present the pulsed laser deposition (PLD) technique to control the growth of metal oxide materials at atomic level using high-pressure reflective high-energy electron diffraction and ellipsometry. These developments have helped to make PLD a grown-up technique to fabricate complex

  18. Phase transition of bismuth telluride thin films grown by MBE

    DEFF Research Database (Denmark)

    Fülöp, Attila; Song, Yuxin; Charpentier, Sophie

    2014-01-01

    A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation...

  19. Accurate prediction of band gaps and optical properties of HfO2

    Science.gov (United States)

    Ondračka, Pavel; Holec, David; Nečas, David; Zajíčková, Lenka

    2016-10-01

    We report on optical properties of various polymorphs of hafnia predicted within the framework of density functional theory. The full potential linearised augmented plane wave method was employed together with the Tran-Blaha modified Becke-Johnson potential (TB-mBJ) for exchange and local density approximation for correlation. Unit cells of monoclinic, cubic and tetragonal crystalline, and a simulated annealing-based model of amorphous hafnia were fully relaxed with respect to internal positions and lattice parameters. Electronic structures and band gaps for monoclinic, cubic, tetragonal and amorphous hafnia were calculated using three different TB-mBJ parametrisations and the results were critically compared with the available experimental and theoretical reports. Conceptual differences between a straightforward comparison of experimental measurements to a calculated band gap on the one hand and to a whole electronic structure (density of electronic states) on the other hand, were pointed out, suggesting the latter should be used whenever possible. Finally, dielectric functions were calculated at two levels, using the random phase approximation without local field effects and with a more accurate Bethe-Salpether equation (BSE) to account for excitonic effects. We conclude that a satisfactory agreement with experimental data for HfO2 was obtained only in the latter case.

  20. PbTe thin films grown by femtosecond pulsed laser deposition

    Science.gov (United States)

    Rodriguez, E.; Silva, D.; Moya, L.; Cesar, C. L.; Barbosa, L. C.; Schrank, A.; Souza Filho, C. R.; de Oliveira, E. P.

    2007-09-01

    PbTe thin films were grown on BK7 glass and Si(100) substrates using femtosecond pulsed laser deposition at room temperature. The influence of the background pressure and the laser fluence on the structural and optical characteristics of the PbTe films was studied. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the surface and structural properties of the deposited PbTe thin films, respectively. Transmission spectroscopy measurements in the visible and infrared region (VIS-IR) were used to investigate the optical properties of the PbTe thin films.

  1. Growth and atomic structure of tellurium thin films grown on Bi2Te3

    Science.gov (United States)

    Okuyama, Yuma; Sugiyama, Yuya; Ideta, Shin-ichiro; Tanaka, Kiyohisa; Hirahara, Toru

    2017-03-01

    We have grown tellurium (Te) thin films on Bi2Te3 and investigated the atomic structure. From low-energy electron diffraction (LEED) measurements, we found that the Te films are [10 1 bar0]-oriented with six domains. A detailed analysis of the reflection high-energy electron diffraction (RHEED) pattern revealed that the films are strained with the in-plane lattice constant compressed by ∼1.5% compared to the bulk value due to the epitaxy between Te and Bi2Te3. These films will be interesting systems to investigate the predicted topological phases that occur in strained Te.

  2. Property modulation of NiO films grown by radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, T.F.; Wang, A.J.; Shang, B.Y. [Department of Physics, Beijing Normal University, Beijing 100875 (China); Wu, Z.L.; Li, Y.L. [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Wang, Y.S., E-mail: yswang@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China)

    2015-09-15

    Highlights: • Controllable and preferential growth of NiO films were performed successfully on Si substrates. • Oxygen partial pressure lower than 6% is crucial for transformation of the preferential growth. • The film deposition rate is very sensitive to the low oxygen partial pressure. • NiO lattice expands quadratically with the increasing of oxygen partial pressures. • The films contain high concentration of Ni vacancies and show a good rectifying behavior with p-Si. - Abstract: NiO films were grown on Si substrates by radio frequency magnetron sputtering. The films were analyzed by an X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscopy and SCS-4200 semiconductor characterization system. Evolution of the growth mode, lattice strain, morphology, chemistry states and electrical properties were investigated systematically. The film deposition rates and properties are very sensitive to the oxygen partial pressure lower than 10%. It is crucial to decrease the oxygen partial pressure to 2% for (1 1 1) film growth and the films would transform from (1 1 1) to (1 0 0) as the oxygen partial pressure increases from 2% to 6%. The film lattice expands quadratically with the increase of oxygen partial pressure. Nickel vacancy concentration in (1 1 1) films is much higher than that in (1 0 0) films. All (1 0 0) films show good rectifying behavior with p-Si. The film growth modes and properties could be modulated flexibly by controlling the oxygen partial pressures.

  3. Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers

    Science.gov (United States)

    Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

    2017-01-01

    Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I–V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later. PMID:28252106

  4. Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers

    Science.gov (United States)

    Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

    2017-03-01

    Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later.

  5. Morphology and photoresponse of crystalline antimony film grown on mica by physical vapor deposition

    Directory of Open Access Journals (Sweden)

    Shafa Muhammad

    2016-09-01

    Full Text Available Antimony is a promising material for the fabrication of photodetectors. This study deals with the growth of a photosensitive thin film by the physical vapor deposition (PVD of antimony onto mica surface in a furnace tube. The geometry of the grown structures was studied via scanning electron microscopy (SEM, X-ray diffraction (XRD, energy-dispersive X-ray spectroscopy (EDX and elemental diffraction analysis. XRD peaks of the antimony film grown on mica mostly matched with JCPDF Card. The formation of rhombohedral crystal structures in the film was further confirmed by SEM micrographs and chemical composition analysis. The Hall measurements revealed good electrical conductivity of the film with bulk carrier concentration of the order of 1022 Ω·cm-3 and mobility of 9.034 cm2/Vs. The grown film was successfully tested for radiation detection. The photoresponse of the film was evaluated using its current-voltage characteristics. These investigations revealed that the photosensitivity of the antimony film was 20 times higher than that of crystalline germanium.

  6. Oxygen Ion Conductance in Epitaxially Grown Thin Film Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Thevuthasan, Suntharampillai; Yu, Zhongqing; Kuchibhatla, Satyanarayana V N T; Saraf, Laxmikant V.; Marina, Olga A.; Shutthanandan, V.; Nachimuthu, Ponnusamy; Wang, Chong M.

    2009-04-01

    This paper briefly summarizes the results from a project aimed to develop an understanding of oxygen ionic transport processes in highly oriented thin film oxide materials to enable the design of new types of electrolyte materials for solid state electrochemical devices. We have used oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE) to grow highly oriented doped ceria, zriconia thin films on single crystal c-Al2O3 along with multilayered hetero-structures. The influence of dopant concentration, interfaces, defects and crystalline quality on oxygen ionic conductivity has been critically analyzed using various surface and bulk sensitive capabilities. Although, preferred (111) orientation was preserved in high quality samaria doped ceria films up to a 10 atom% Sm doping, the films started to show polycrystalline features for higher Sm doping. Maximum conductivity was obtained for 5 atom% Sm doping in ceria. In the case of gadolinia doped ceria/zirconia multi-layer films, total conductivity was found to increase with the increasing number of layers.

  7. Studies on electrochemically grown Cd-Fe-Se thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mahalingam, T. [Alagappa Univ., Karaikudi (India). Dept. of Physics; Ajou Univ., Suwon (Korea, Republic of). Dept. of Electrical and Computer Engineering; Thanikaikarasan, S.; Raja, M.; Sanjeeviraja, C. [Alagappa Univ., Karaikudi (India). Dept. of Physics; Lee, S.; Moon, H.; Kim, Y.D. [Ajou Univ., Suwon (Korea, Republic of). Dept. of Molecular Science and Technology; Sebastian, P.J. [CIE-UNAM, Temixco, Morelos (Mexico); Chipas Polytechnical Univ., Chipas (Mexico)

    2007-01-15

    This paper presented the results of a study that investigated the electrochemical, structural, compositional, morphological and photoelectrochemical properties of cadmium ferrous selenide (Cd-Fe-Se) semiconducting thin films electrodeposited onto conducted tin oxide (SnO{sub 2}) coated glass substrates at various cadmium sulfate concentrations in the deposition bath. Experimental details were provided along with results of typical cyclic voltammograms of Cd-Fe-Se thin film cathodically deposited from an acid solution containing CdSO{sub 4}, FeSO{sub 4} and SeO{sub 2} without any additives. Variations in film thickness were determined along with compositional analysis and morphological studies. Photoelectrochemical (PEC) solar cell studies were performed in a cell consisting of photoelectrode (Cd-Fe{sub S}e), a platinum counter electrode and a saturated dalomel reference electrode. A hot probe method identified the nature of the thin film to be n-type, while the structure was found to be hexagon for CdSe, tetragonal for {alpha}-FeSe and orthorhombic for FeSe{sub 2}. According to energy dispersive analysis of X-rays (EDAX), the stoichiometric values of Cd and Se are obtained at higher concentration of CdSO{sub 4}. The maximum concentration of CD{sup 2+} ions in the solution bath yielded thin films with smooth surfaces. 18 refs., 1 tab., 6 figs.

  8. Pyroelectric and piezoelectric responses of thin AlN films epitaxy-grown on a SiC/Si substrate

    Science.gov (United States)

    Kukushkin, S. A.; Osipov, A. V.; Sergeeva, O. N.; Kiselev, D. A.; Bogomolov, A. A.; Solnyshkin, A. V.; Kaptelov, E. Yu.; Senkevich, S. V.; Pronin, I. P.

    2016-05-01

    This paper presents the results of pyroelectric and piezoelectric studies of AlN films formed by chloride-hydride epitaxy (CHE) and molecular beam epitaxy (MBE) on epitaxial SiC nanolayers grown on Si by the atom substitution method. The surface topography and piezoelectric and pyroelecrtric responses of AlN films have been analyzed. The results of the study have shown that the vertical component of the piezoresponse in CHE-grown AlN films is more homogeneous over the film area than that in MBE-grown AlN films. However, the signal from the MBE-synthesized AlN films proved to be stronger. The inversion of the polar axis (polarization vector) on passage from MBE-grown AlN films to CHE-grown AlN films has been found experimentally. It has been shown that the polar axis in MBE-grown films is directed from the free surface of the film toward the Si substrate while, in CHE-grown films, the polarization vector is directed toward the free surface.

  9. Nanocrystalline magnetite thin films grown by dual ion-beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, Pilar, E-mail: pilar.prieto@uam.es [Departamento de Física Aplicada M-12, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ruiz, Patricia [Departamento de Física Aplicada M-12, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ferrer, Isabel J. [Departamento de Física de Materiales M-4, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Figuera, Juan de la; Marco, José F. [Instituto de Química Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid (Spain)

    2015-07-05

    Highlights: • We have grown tensile and compressive strained nanocrystalline magnetite thin films by dual ion beam sputtering. • The magnetic and thermoelectric properties can be controlled by the deposition conditions. • The magnetic anisotropy depends on the crystalline grain size. • The thermoelectric properties depend on the type of strain induced in the films. • In plane uniaxial magnetic anisotropy develops in magnetite thin films with grain sizes ⩽20 nm. - Abstract: We have explored the influence of an ion-assisted beam in the thermoelectric and magnetic properties of nanocrystalline magnetite thin films grown by ion-beam sputtering. The microstructure has been investigated by XRD. Tensile and compressive strained thin films have been obtained as a function of the parameters of the ion-assisted beam. The evolution of the in-plane magnetic anisotropy was attributed to crystalline grain size. In some films, magneto-optical Kerr effect measurements reveal the existence of uniaxial magnetic anisotropy induced by the deposition process related with a small grain size (⩽20 nm). Isotropic magnetic properties have observed in nanocrystalline magnetite thin film having larger grain sizes. The largest power factor of all the films prepared (0.47 μW/K{sup 2} cm), obtained from a Seebeck coefficient of −80 μV/K and an electrical resistivity of 13 mΩ cm, is obtained in a nanocrystalline magnetite thin film with an expanded out-of-plane lattice and with a grain size ≈30 nm.

  10. Epitaxial Cu(001) films grown on a Cr/Ag/Fe/GaAs(001) buffer system

    Energy Technology Data Exchange (ETDEWEB)

    Gottlob, Daniel M., E-mail: d.gottlob@fz-juelich.de [Peter Grünberg Institut, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47048 Duisburg (Germany); Jansen, Thomas [Peter Grünberg Institut, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); Jülich-Aachen Research Alliance, Fundamentals for Future Information Technology (JARA-FIT), Forschungszentrum Jülich, 52425 Jülich (Germany); Hoppe, Michael [Peter Grünberg Institut, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); Bürgler, Daniel E. [Peter Grünberg Institut, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52425 Jülich (Germany); Jülich-Aachen Research Alliance, Fundamentals for Future Information Technology (JARA-FIT), Forschungszentrum Jülich, 52425 Jülich (Germany); and others

    2014-07-01

    We present a procedure to prepare single-crystalline, high-purity Cu(001) films (templates) suitable as substrates for subsequent epitaxial thin-film growth. The template films were grown in a dedicated molecular-beam epitaxy system on a Cr/Ag/Fe/GaAs(001) buffer layer system. Low-energy electron diffraction and X-ray diffraction were applied to determine the surface orientation and the epitaxial relationship between all layers of the stack. Post-annealing at moderate temperatures enhances the quality of the film as shown by low-energy electron diffraction and atomic force microscopy. X-ray photoemission and Auger electron spectroscopy confirm that no atoms of the buffer layers diffuse into the Cu film during the initial preparation and the post-annealing treatment. The completed Cu(001) template system can be exposed to air and afterwards refurbished by Ar{sup +}-ion bombardment and annealing, enabling the transfer between vacuum systems. The procedure provides suitable conductive thin film templates for studies of epitaxial thin films, e.g. on the magnetic and magnetotransport properties of Co and Ni based films and multilayers. - Highlights: • Preparation of epitaxial Cu(001) template films on an insulating substrate • Characterization of template structure, orientation, cleanness, and roughness • Template films can be exposed to air and refurbished in different vacuum system. • Template films are suitable for further thin film growth at up to 570 K.

  11. Ultrafast carrier dynamics in purified and as-grown single-walled carbon nanotube films

    Institute of Scientific and Technical Information of China (English)

    Long Yong-Bing; Song Li; Zhang Chun-Yu; Wang Li; Fu Pan-Ming; Zhang Zhi-Guo; Xie Si-Shen; Wang Guo-Ping

    2005-01-01

    Ultrafast time-resolved optical transmissions in purified and as-grown single-walled carbon nanotube films are measured at a temperature of 200K. The signal of the purified sample shows a crossover from photobleaching to photoabsorption. The former and the latter are interpreted as the state filling and the red shift of the π-plasmon,respectively. The signal of the as-grown sample can be perfectly fitted by a single-exponential with a time constant of 232fs. The disappearance of the negative component in the as-grown sample is attributed to the charge transfer between the semiconducting nanotubes and the impurities.

  12. Molecular alignments in sexiphenyl thin films epitaxially grown on muscovite

    Energy Technology Data Exchange (ETDEWEB)

    Plank, H.; Resel, R.; Sitter, H.; Andreev, A.; Sariciftci, N.S.; Hlawacek, G.; Teichert, C.; Thierry, A.; Lotz, B

    2003-10-22

    The epitaxial orientations of highly crystalline para-sexiphenyl (C{sub 36}H{sub 26}) films on mica (001) surfaces are investigated by selected area electron diffraction (SAED) and transmission electron microscopy (TEM). Films at the early growth stage (growth time 26 s) and at an advanced growth stage (growth time 10 min) are studied. Films at the early growth stage exhibit only three-dimensional islands with an average size of 60x30x10 nm{sup 3}, whereas films at an advanced growth stage consist of long oriented nano-fibres with a needle-like morphology. We identified three different types of epitaxial relations between the mica (001) substrate and the sexiphenyl crystallites, which are the same in both growth stages. Moreover, within a single island as well as within a single fibre crystalline domains with these three epitaxial orientations are observed. At the advanced growth stage, these domains are aligned antiparallel or perpendicular to the fibre axes; the typical size of the domains is 20 nm.

  13. Lightweight sodium alanate thin films grown by reactive sputtering

    NARCIS (Netherlands)

    Filippi, M.; Rector, J.H.; Gremaud, R.; Van Setten, M.J.; Dam, B.

    2009-01-01

    We report the preparation of sodium alanate, a promising hydrogen storage material, in a thin film form using cosputtering in a reactive atmosphere of atomic hydrogen. We study the phase formation and distribution, and the hydrogen desorption, with a combination of optical and infrared transmission

  14. Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy.

    Science.gov (United States)

    Lin, Shih-Wei; Wu, Yue-Han; Chang, Li; Liang, Chi-Te; Lin, Sheng-Di

    2015-01-01

    We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy. This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy. The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

  15. Preparation and characterization of GaN films grown on Ga-diffused Si(111) substrates

    Institute of Scientific and Technical Information of China (English)

    SUN Zhencui; CAO Wentian; WEI Qinqin; WANG Shuyun; XUE Chengshan; SUN Haibo

    2005-01-01

    Hexagonal GaN films were prepared by nitriding Ga2O3 films with flowing ammonia. Ga2O3 films were deposited on Ga-diffused Si (111) substrates by radio frequency (r.f.) magnetron sputtering. This paper have investigated the change of structural properties of GaN films nitrided in NH3 atmosphere at the temperatures of 850, 900, and 950℃ for 15min and nitrided at the temperature of 900℃ for 10, 15, and 20 min, respectively. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the structure, surface morphology and composition of synthesized samples. The results reveal that the as-grown films are polycrystalline GaN with hexagonal wurtzite structure and GaN films with the highest crystal quality can be obtained when nitrided at 900℃ for 15 min.

  16. Characterisation of molecular thin films grown by organic molecular beam deposition

    CERN Document Server

    Bayliss, S M

    2000-01-01

    This work concerns the growth and characterisation of molecular thin films in an ultra high vacuum regime by organic molecular beam deposition (OMBD). Films of three different molecular materials are grown, namely free base phthalocyanine (H sub 2 Pc), perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) and aluminium tris-8-hydroxyquinoline (Alq sub 3). The relationship between the growth parameters such as film thickness, growth rate, and substrate temperature during and after growth, and the structural, optical and morphological properties of the film are investigated. These investigations are carried out using various ex-situ techniques. X-ray diffraction, Raman spectroscopy and electronic absorption spectroscopy are used to probe the bulk film characteristics, whilst Nomarski microscopy and atomic force microscopy are used to study the surface morphology. Three different levels of influence of the growth parameters on the film properties are observed. In the case of H sub 2 Pc, two crystal phases are fo...

  17. Thermoelectric properties of epitaxial β-FeSi2 thin films grown on Si(111) substrates with various film qualities

    Science.gov (United States)

    Watanabe, Kentaro; Taniguchi, Tatsuhiko; Sakane, Shunya; Aoki, Shunsuke; Suzuki, Takeyuki; Fujita, Takeshi; Nakamura, Yoshiaki

    2017-05-01

    Si-based epitaxial β-FeSi2 thin films are attractive as materials for on-chip thermoelectric power generators. We investigated the structure, crystallinity, and thermoelectric properties of β-FeSi2 thin films epitaxially grown on Si(111) substrates by using three different techniques: conventional reactive deposition epitaxy followed by molecular beam epitaxy (RDE+MBE), solid phase epitaxy (SPE) based on codeposition of Fe and Si presented previously, and SPE followed by MBE (SPE+MBE) presented newly by this work. Their epitaxial growth temperatures were fixed at 530 °C for comparison. RDE+MBE thin films exhibited high crystalline quality, but rough surfaces and rugged β-FeSi2/Si(111) interfaces. On the other hand, SPE thin films showed flat surfaces and abrupt β-FeSi2/Si(111) interfaces but low crystallinity. We found that SPE+MBE thin films realized crystallinity higher than SPE thin films, and also had flatter surfaces and sharper interfaces than RDE+MBE thin films. In SPE+MBE thin film growth, due to the initial SPE process with low temperature codeposition, thermal interdiffusion of Fe and Si was suppressed, resulting in the surface flatness and abrupt interface. Second high temperature MBE process improved the crystallinity. We also investigated thermoelectric properties of these β-FeSi2 thin films. Structural factors affecting the thermoelectric properties of RDE+MBE, SPE, and SPE+MBE thin films were investigated.

  18. Microstructure, Photoluminescent Properties and Application of ZnO Films Grown on Al Foils

    Institute of Scientific and Technical Information of China (English)

    WU Hongyan; ZHAO Jiayu; XIE Aigen; XU Linhua; ZHONG Kun; SHEN Tongtong

    2015-01-01

    To obtain safety working before long-term early warning, we proposed a process for the preparation of luminescent films on metal substrate to detect the wear life. ZnO films were prepared on aluminum (Al) foils by the magnetron sputtering technique. The microstructure, tribological properties and photoluminescence (PL) spectra of ZnO films before and after the friction test were investigated. The microstructure of ZnO films grown on Al foils exhibited a closely packed hexagonal cone shape. ZnO films were grown along the orientation perpendicular to the substrate. The tribometric tests revealed that the average friction coefficient of ZnO films was lower and more stable than that of the substrate. The results of PL spectra indicated that the effect of Al element on ZnO films led to shifts of the defect related visible band. The luminescent center of ZnO films shifted from the emission peak at 510 nm before the friction to 647 nm after the friction, indicating that the green light shifted into the red light as the friction occurred. The visible light was helpful to understanding the failure characteristics during the friction and wear, and provide an early indicator of the impending failure.

  19. Solid Lubrication of Laser Grown Fluorinated Diamond Thin Films

    Science.gov (United States)

    1992-01-21

    irradiation of laser beam on the substrate surface 2 Schematic diagram showing laser CVD experimental set- up . 27 A single laser beam (YAG or Excimer) was only...0.05 to 0.2 depending upon temperature, environment, load, speed and presence of foreign material. Todate , ultra-low coefficients of friction (0.02...Laser technology for diamond film fabrication is very new and todate only a handful number of publications are available that address directly on the

  20. Hybrid Organic-Inorganic Films Grown Using Molecular Layer Deposition

    Science.gov (United States)

    2011-03-01

    discussed below for the MLD of the alucone based on TMA and glycerol . Alternatively, a heterobifunctional precursor, such as ethanolamine, HO- CH2...amine-terminated surface functional groups to reform carboxylic groups through a ring-opening reaction in reaction C given by Eqn. 5. The three-step...small amount of cross-linking in the MLD film. These problems with the TMA + EG MLD system led to the recent exploration of the TMA + glycerol system

  1. SnO2 anode surface passivation by atomic layer deposited HfO2 improves li-ion battery performance

    KAUST Repository

    Yesibolati, Nulati

    2014-03-14

    For the first time, it is demonstrated that nanoscale HfO2 surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO2-based anodes. Specifically, the measured battery capacity at a current density of 150 mAg -1 after 100 cycles is 548 and 853 mAhg-1 for the uncoated and HfO2-coated anodes, respectively. Material analysis reveals that the HfO2 layers are amorphous in nature and conformably coat the SnO2-based anodes. In addition, the analysis reveals that ALD HfO2 not only protects the SnO2-based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO2 anodes to increase battery capacity, despite the fact that HfO2 is itself electrochemically inactive. The amorphous nature of HfO2 is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. MBE and ALD grown High k Dielectrics Gate Stacks on GaN

    Science.gov (United States)

    Chang, Y. C.; Lee, K. Y.; Lee, W. C.; Lin, T. D.; Lee, Y. J.; Huang, M. L.; Hong, M.; Kwo, J.; Wang, Y. H.

    2007-03-01

    III-nitride compound semiconductors are attractive for high-temperature and high-power MOSFET applications due to their intrinsic properties of wide band gap, high breakdown field, and high saturation velocity under high fields. In this work GaN-based high k MOS diodes were fabricated using MBE-grown Ga2O3(Gd2O3), MBE-grown HfO2 and ALD-grown HfO2 as the gate dielectrics with dielectric constants of 14.7, 17.4 and 16.5, respectively. All MOS diodes exhibited low leakage (XPS and with the bandgaps of the oxides. For example, the ALD-grown HfO2-GaN at the interfaces gave approximately δEC and δEV of 1.2 eV and 1.1 eV, respectively.

  3. Strain relaxation in thin films of Cu grown on Ni(001)

    DEFF Research Database (Denmark)

    Rasmussen, F.B.; Baker, J.; Nielsen, M.;

    1998-01-01

    Surface X-ray diffraction and kinematical model calculations are used to determine the strain relaxation of embedded wedges with internal (111) facets formed in thin Cu films when grown on Ni(001). We show the wedges to be inhomogenously strained with a large lateral relaxation near the Cu...

  4. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    OpenAIRE

    2012-01-01

    The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis o...

  5. Electrical phase change of CVD-grown Ge-Sb-Te thin film device

    OpenAIRE

    Huang, C.C.; B. Gholipour; Ou, J.Y.; Knight, K.J.; Hewak, D. W.

    2011-01-01

    A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film ha...

  6. Magnetization reversal of ultrathin Fe film grown on Si(111) using iron silicide template

    Institute of Scientific and Technical Information of China (English)

    He Wei; Zhan Qing-Feng; Wang De-Yong; Chen Li-Jun; Sun Young; Cheng Zhao-Hua

    2007-01-01

    Ultrathin Fe films were epitaxially grown on Si(111) by using an ultrathin iron silicide film with p(2 × 2) surface reconstruction as a template. The surface structure and magnetic properties were investigated in situ by low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), and surface magneto-optical effect (SMOKE). Polar SMOKE hysteresis loops demonstrate that the Fe ultrathin films with thickness t< 6 ML (monolayers) exhibit perpendicular magnetic anisotropy. The characters of M-H loops with the external magnetic field at difference angles and the angular dependence of coercivity suggest that the domain-wall pinning plays a dominant role in the magnetization reversal process.

  7. CeO2掺杂对HfO2栅介质电学特性的影响%Influence of CeO2-Doping on Electrical Properties of HfO2 Gate Dielectrics

    Institute of Scientific and Technical Information of China (English)

    杨萌萌; 屠海令; 张心强; 熊玉华; 王小娜; 杜军

    2012-01-01

    采用磁控共溅射的方法在p-Si(100)衬底上沉积了掺杂和不掺杂CeO2的HfO2薄膜.通过X射线光电子能谱(XPS)研究了薄膜中元素的化学计量比及结合能,制备MOS结构并对漏电流及电容等电学性能进行表征.结果表明,掺入CeO2后,整个体系的氧空位生成能增大,氧空位数目减少,漏电流较纯HfO2下降了一个数量级,满足作为高k材料的要求.%CeO2-doped HfO2(CDH) thin films were deposited on p-Si substrates by RF magnetron co-sputtering. The film thickness was measured by surface profiler. The binding energy of elements was characterized by X-ray photoelectron spectroscopy ( XPS). MOS structures were made to characterize the leakage current and capacitance. XPS analysis of Hf 4f and 01s confirmed that the Hf-0 binding energy increased after doping CeO2. This resulted in the increase of the oxygen vacancy formation energy and the reduction of the concentration of oxygen vacancy. The leakage current density of CDH film was about one order of magnitude lower than that of HfO2 film. CDH film can meet the requirements of high-fc application.

  8. RF Magnetron Sputtering Grown Cu2O Film Structural, Morphological, and Electrical Property Dependencies on Substrate Type.

    Science.gov (United States)

    Ahn, Heejin; Um, Youngho

    2015-03-01

    We investigated the structural, morphological, and electrical properties of cuprous oxide (Cu2O) film dependency on substrate type. Thin films grown using RF magnetron sputtering were characterized by scanning electron microscopy, X-ray diffraction (XRD), and Hall effect measurements. Cu2O thin films were deposited onto sapphire (0001), Si (100), and MgO (110) substrates, and showed Cu2O single phase only, which was confirmed by XRD measurement. Relatively larger compressive strain existed in Cu2O film grown on sapphire and Si, while a smaller tensile strain appeared in Cu2O film grown on MgO. Cu2O thin film crystallite sizes showed a linear dependence on strain. Moreover, film carrier concentration and mobility increased with increasing strain, while resistivity decreased with decreasing strain. Cu2O film strain due to induced strain opens the possibility of controlling structural and electrical properties in device applications.

  9. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer

    Science.gov (United States)

    Dong, K. F.; Deng, J. Y.; Peng, Y. G.; Ju, G.; Chow, G. M.; Chen, J. S.

    2016-09-01

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) //ZrN (001) //TiN (001) among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained.

  10. Structural characterization of InSb thin films grown by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: joginderchauhan82@gmail.com; Rajaram, P. [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2015-06-24

    In the present work we have grown InSb thin films on brass substrates, using the electrodeposition technique. The electrochemical baths used in the growth were made up of aqueous solutions of InCl{sub 3} and SbCl{sub 3} mixed together in various proportions. The films grown were characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Analysis of X-rays (EDAX). Compositional studies show that stoichiometric InSb films can be prepared from a bath containing 0.05M InCl{sub 3} and 0.04M SbCl{sub 3}. XRD studies reveal that the films grown are polycrystalline having the zinc blende structure with (111) orientation. Crystallite size, dislocation density and strain were calculated using the XRD results. Optical transmission spectra were recorded using an FTIR spectrophotometer. The value of direct band gap was found to be around 0.20 eV for the thin films having the best stoichiometry.

  11. Do CVD grown graphene films have antibacterial activity on metallic substrates?

    CERN Document Server

    Dellieu, Louis; Reckinger, Nicolas; Didembourg, Christian; Letesson, Jean-Jacques; Sarrazin, Michael; Deparis, Olivier; Matroule, Jean-Yves; Colomer, Jean-François

    2014-01-01

    Accurate assessment of the antibacterial activity of graphene requires consideration of both the graphene fabrication method and, for supported films, the properties of the substrate. Large-area graphene films produced by chemical vapor deposition were grown directly on copper substrates or transferred on a gold substrate and their effect on the viability and proliferation of the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli were assessed. The viability and the proliferation of both bacterial species were not affected when they were grown on a graphene film entirely covering the gold substrate, indicating that conductivity plays no role on bacterial viability and graphene has no antibacterial activity against S. aureus and E. coli. On the other hand, antibacterial activity was observed when graphene coated the copper substrates, resulting from the release of bactericidal cupric ions in inverse proportion to the graphene surface coverage.

  12. Annealing effects of sapphire substrate on properties of ZnO films grown by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.Z. [South China Normal University, School of Physics and Telecommunication Engineering, Guangzhou (China); Xu, J. [Chinese Academy of Sciences, Shanghai Institute of Optics and Fine Mechanics, P.O. Box 800-211, Shanghai (China)

    2007-09-15

    The annealing effects of sapphire substrates on the quality of epitaxial ZnO films grown by dc reactive magnetron sputtering were studied. The atomic steps formed on (0001) sapphire ({alpha}-Al{sub 2}O{sub 3}) substrates surface by annealing at high temperature were analyzed by atomic force microscopy. Their influence on the growth of ZnO films was examined by X-ray diffraction and photoluminescence measurements. Experimental results indicate that the film quality is strongly affected by annealing treatment of the sapphire substrate surface. The optimum annealing temperature of sapphire substrates for ZnO grown by magnetron sputtering is 1400 C for 1 h in air. (orig.)

  13. Mobility enhanced photoactivity in sol-gel grown epitaxial anatase TiO2 films.

    Science.gov (United States)

    Jung, Hyun Suk; Lee, Jung-Kun; Lee, Jaegab; Kang, Bo Soo; Jia, Quanxi; Nastasi, Michael; Noh, Jun Hong; Cho, Chin-Moo; Yoon, Sung Hoon

    2008-03-18

    Epitaxial anatase thin films were grown on single-crystal LaAlO3 substrates by a sol-gel process. The epitaxial relationship between TiO2 and LaAlO3 was found to be [100]TiO2||[100]LaAlO3 and (001)TiO2||(001)LaAlO3 based on X-ray diffraction and a high-resolution transmission electron microscopy. The epitaxial anatase films show significantly improved photocatalytic properties, compared with polycrystalline anatase film on fused silica substrate. The increase in the photocatalytic activity of epitaxial anatase films is explained by enhanced charge carrier mobility, which is traced to the decreased grain boundary density in the epitaxial anatase film.

  14. Nanostructured Diamond-Like Carbon Films Grown by Off-Axis Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Seong Shan Yap

    2015-01-01

    Full Text Available Nanostructured diamond-like carbon (DLC films instead of the ultrasmooth film were obtained by pulsed laser ablation of pyrolytic graphite. Deposition was performed at room temperature in vacuum with substrates placed at off-axis position. The configuration utilized high density plasma plume arriving at low effective angle for the formation of nanostructured DLC. Nanostructures with maximum size of 50 nm were deposited as compared to the ultrasmooth DLC films obtained in a conventional deposition. The Raman spectra of the films confirmed that the films were diamond-like/amorphous in nature. Although grown at an angle, ion energy of >35 eV was obtained at the off-axis position. This was proposed to be responsible for subplantation growth of sp3 hybridized carbon. The condensation of energetic clusters and oblique angle deposition correspondingly gave rise to the formation of nanostructured DLC in this study.

  15. Structural and nonlinear optical properties of as-grown and annealed metallophthalocyanine thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zawadzka, A., E-mail: azawa@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Płóciennik, P.; Strzelecki, J. [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Pranaitis, M.; Dabos-Seignon, S.; Sahraoui, B. [LUNAM Université, Université d' Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 bd Lavoisier, 49045 Angers cedex (France)

    2013-10-31

    The paper presents the Third Harmonic Generation investigation of four metallophtalocyanine (MPc, M = Cu, Co, Mg and Zn) thin films. The investigated films were fabricated by Physical Vapor Deposition in high vacuum onto quartz substrates. MPc thin films were annealed after fabrication in ambient atmosphere for 12 h at the temperature equal to 150 °C or 250 °C. The Third Harmonic Generation spectra were measured to investigate the nonlinear optical properties and their dependence on the structure of the thin film after the annealing process. This approach allowed us to determine the electronic contribution of the third-order nonlinear optical susceptibility χ{sup <3>}{sub elec} of these MPc films and to investigate two theoretical models for explanation of the observed results. We find that the annealing process significantly changes the optical and structural properties of MPc thin films. - Highlights: • Metallophtalocyanine thin films were grown by Physical Vapor Deposition technique. • MPcs thin films were undergone an annealing process in ambient atmosphere. • Third Harmonic spectra were measured to investigate nonlinear optical properties. • The third order nonlinear optical susceptibility χ{sup <3>}{sub elec} was determined. • We report changing both nonlinear optical and structural properties of thin films.

  16. Superconducting YBa 2Cu 3O 7- δ thin film grown on metallic film evaporated on MgO

    Science.gov (United States)

    Verdyan, A.; Azoulay, J.; Lapsker, I.

    2001-03-01

    At present it is commonly accepted that thin film formation of YBa 2Cu 3O 7- δ (YBCO) on conducting substrate is one of the keys to further development of advanced devices in the microelectronic and other applications. We have grown YBCO thin films by resistive evaporation technique on MgO coated with metallic layers (Ni or Ag). A simple inexpensive vacuum system equipped with resistively heated boats for metal and precursor mixture of yttrium, copper and barium fluoride powders was used. X-ray diffraction (XRD) and scanning electron microscopy techniques were used for texture, morphology and surface analyses respectively. Electrical and magnetical properties were determined by a standard dc four-probe method. The way of heating process is shown to be critical parameter in the film quality. The physical and electrical properties of the YBCO films are discussed in light of the fact that XRD measurements done on the metallic buffer layers have revealed a multicrystalline structure.

  17. Microstructure, optical and electrical properties of Al-doped ZnO films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Su, Jianfeng, E-mail: sujianfengvy@gmail.com [Department of Mathematics and Physics, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Tang, Chunjuan; Niu, Qiang; Zang, Chunhe; Zhang, Yongsheng [Department of Mathematics and Physics, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Fu, Zhuxi [Department of Physics, University of Science and Technology of China, Hefei 230026 (China)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer Al-doped ZnO films were grown on quartz substrates by MOCVD. Black-Right-Pointing-Pointer The preferred orientation of ZnO films decreased with the increase of Al content. Black-Right-Pointing-Pointer Decomposition products of TMA bringing down the surface activity of ZnO grains. Black-Right-Pointing-Pointer UV emission peak initially red-shifted and then blue-shifted as increasing Al content. Black-Right-Pointing-Pointer Low electrical resistivity of Al-doped ZnO films was obtained. - Abstract: Al-doped ZnO films were grown on quartz substrates by MOCVD. A systematical and detailed study about the effect of Al content on structural, optical and electrical properties were discussed. XRD measurements revealed that the preferred orientation of ZnO films decreased with the increase of Al content. AFM images indicated that the TMA molecules or their decomposition products bringing down the surface activity of ZnO grains, and so grain growth is inhibited. By the band tail states and the quantum confinement effect, the UV emission peak initially red-shifted and then blue-shifted. All Al-doped samples demonstrated more than 80% of the optical transparency in the visible region. Low electrical resistivity of Al-doped ZnO films was obtained. However, due to defects and grain boundary scattering which caused by Al doping, the hall mobility is increased initially and then decreased.

  18. Simulation study of HEMT structures with HfO2 cap layer for mitigating inverse piezoelectric effect related device failures

    Directory of Open Access Journals (Sweden)

    Deepthi Nagulapally

    2015-01-01

    Full Text Available The Inverse Piezoelectric Effect (IPE is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs. Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO2 “cap layer” above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using “field plates” in concert with high-k oxides.

  19. Biocidal Silver and Silver/Titania Composite Films Grown by Chemical Vapour Deposition

    Directory of Open Access Journals (Sweden)

    D. W. Sheel

    2008-01-01

    Full Text Available This paper describes the growth and testing of highly active biocidal films based on photocatalytically active films of TiO2, grown by thermal CVD, functionally and structurally modified by deposition of nanostructured silver via a novel flame assisted combination CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to possess strong antibacterial behaviour. The deposition control, arising from the described approach, offers the potential to control the film nanostructure, which is proposed to be crucial in determining the photo and bioactivity of the combined film structure, and the transparency of the composite films. Furthermore, we show that the resultant films are active to a range of organisms, including Gram-negative and Gram-positive bacteria, and viruses. The very high-biocidal activity is above that expected from the concentrations of silver present, and this is discussed in terms of nanostructure of the titania/silver surface. These properties are especially significant when combined with the well-known durability of CVD deposited thin films, offering new opportunities for enhanced application in areas where biocidal surface functionality is sought.

  20. High-quality AlN films grown on chemical vapor-deposited graphene films

    Directory of Open Access Journals (Sweden)

    Chen Bin-Hao

    2016-01-01

    Full Text Available We report the growth of high-quality AlN films on graphene. The graphene films were synthesized by CVD and then transferred onto silicon substrates. Epitaxial aluminum nitride films were deposited by DC magnetron sputtering on both graphene as an intermediate layer and silicon as a substrate. The structural characteristics of the AlN films and graphene were investigated. Highly c-axis-oriented AlN crystal structures are investigated based on the XRDpatterns observations.

  1. Structural and morphological characterizations of ZnO films grown on GaAs substrates by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Agouram, S.; Zuniga Perez, J.; Munoz-Sanjose, V. [Universitat de Valencia, Departamento de Fisica Aplicada y Electromagnetismo, Burjassot (Spain)

    2007-07-15

    ZnO films were grown on GaAs(100), GaAs(111)A and GaAs(111)B substrates by metal organic chemical vapour deposition (MOCVD). Diethylzinc (DEZn) and tertiarybutanol (t-butanol) were used as Zn and O precursors, respectively. The influence of the growth temperature and GaAs substrate orientation on the crystalline orientation and morphology of the ZnO grown films has been analysed. Crystallinity of grown films was studied by X-ray diffraction (XRD); thickness and morphology of ZnO films were investigated by scanning electron microscopy (SEM). SEM results reveal significant differences between morphologies depending on growth temperature but not significant differences were detected on the texture of grown films. (orig.)

  2. Engineering of Wet Chemically Grown Nanostructured Zinc Oxide Thin Film by High Electronic Excitation

    Science.gov (United States)

    Birajadar, Ravikiran B.; Ghosh, Arindam A.; Joshi, Rajesh A.; Taur, Vidya S.; Shaikh, S. U.; Ghule, Anil V.; Sharma, Ramphal

    2011-07-01

    Thin films of ZnO are synthesized on ITO substrate using successive ionic layer adsorption and reaction (SILAR) technique. The as-grown thin films were annealed at 250 °C (pristine) in vacuum atmosphere (10-2 Torr) for 1 h and further irradiated using 120 MeV Au9+ ions with different fluence 3×1012 and 5×1012 ions/cm2. These pristine and irradiated samples were studied for structural and optoelectronic properties. XRD study reveals better crystalline quality of film at 3×1012 ions/cm2 fluence. On the other hand, electrical resistivity of the films decreases from 13.44 Ω-cm to 3.74 Ω-cm with increase in irradiation fluence. Also it appears that irradiation does not affect absorption edge.

  3. Morphology of superconducting FeSe thin films grown by MBE and RF-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kronenberg, Alexander; Venzmer, Eike; Haaf, Sebastian ten; Jourdan, Martin [Institut fuer Physik, Johannes Gutenberg Universitaet Mainz (Germany); Maletz, Janek [Institut fuer Physik, Johannes Gutenberg Universitaet Mainz (Germany); Leibniz-Institut fuer Festkoerper- und Werkstoffforschung, Dresden (Germany)

    2013-07-01

    Tunneling spectroscopy on planar junctions is the most direct approach for the investigation of superconducting coupling mechanisms. However, it requires smooth interfaces at the tunneling barrier. The morphology of superconducting thin films of FeSe grown by MBE and co-sputtering (RF) from an iron and a selenium target are compared. MBE deposited films show an extreme sensitivity to stoichiometry, deposition temperature and choice of substrate. These films exhibit macroscopic crevices and a pronounced roughness, rendering the preparation of tunneling junctions impossible. However, sputter deposited epitaxial FeSe thin films clearly show a more favorable morphology. Optical microscopy, AFM and SEM demonstrate a smooth surface with segregations which are eliminated by proper choice of the deposition parameters.

  4. On detection of the Fermi edge in in situ grown thin films of high- Tc oxides

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Saleh, S. A.; Rast, S.; Margaritondo, G.; Onellion, M.; Pavuna, D.

    2001-11-01

    We discuss our systematic series of experiments on the photoelectric detection of the Fermi edge using a cylindrical mirror analyser on films of high- Tc oxides, grown in situ by pulsed laser ablation. The Fermi edge (comparable to the edge of the reference Ag) is very easily observed even in the two-phase BSCCO-2212 film that exhibits onsets of superconducting transitions, at 85 and 45 K. In contrast, the Fermi edge is weaker and more difficult to observe even in the state-of-the-art, highly epitaxial, monophase YBa 2Cu 3O 7- y (YBCO) and NdBa 2Cu 3O 7- y (NBCO-123) films (both with Tc=92 K). So far we could not detect the Fermi edge in the films of the double-`chain' YBCO-124.

  5. Tunability of the superconductivity of tungsten films grown by focused-ion-beam direct writing

    Science.gov (United States)

    Li, Wuxia; Fenton, J. C.; Wang, Yiqian; McComb, D. W.; Warburton, P. A.

    2008-11-01

    We have grown tungsten-containing films by focused-ion-beam (FIB)-induced chemical vapor deposition. The films lie close to the metal-insulator transition with an electrical conductivity which changes by less than 5% between room temperature and 7 K. The superconducting transition temperature Tc of the films can be controlled between 5.0 and 6.2 K by varying the ion-beam deposition current. The Tc can be correlated with how far the films are from the metal-insulator transition, showing a nonmonotonic dependence, which is well described by the heuristic model of [Osofsky et al., Phys. Rev. Lett. 87, 197004 (2001)]. Our results suggest that FIB direct-writing of W composites might be a potential approach to fabricate mask-free superconducting devices as well as to explore the role of reduced dimensionality on superconductivity.

  6. Temperature dependent photoluminescence characteristics of nanocrystalline ZnO films grown by sol-gel technique

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, S.; Goswami, M.L.N.; Das, K.; Dhar, A. [Department of Physics and Meteorology, IIT Kharagpur 721 302 (India); Ray, S.K. [Department of Physics and Meteorology, IIT Kharagpur 721 302 (India)], E-mail: physkr@phy.iitkgp.ernet.in

    2008-10-01

    The structural as well as optical properties of nanocrystalline ZnO films, with hexagonal shaped particles of size 30-35 nm grown on p-Si (100) substrates by sol-gel technique, are investigated. Selected-area electron diffraction and X-ray diffraction patterns of annealed films reveal the formation of wurtzite structure. The mechanism of ultraviolet (UV) and green emission from ZnO thin films, post-annealed at various temperatures, is investigated using photoluminescence spectra. The oxygen content in annealed ZnO films plays an important role to suppress the green band emission. Temperature dependent photoluminescence spectra are recorded in the temperature range 10 K to 300 K to investigate different excitonic peaks in the UV-region.

  7. Physical properties of Bi doped CdTe thin films grown by the CSVT method

    Energy Technology Data Exchange (ETDEWEB)

    Vigil-Galan, O.; Sastre-Hernandez, J.; Cruz-Gandarilla, F.; Aguilar-Hernandez, J.; Contreras-Puente, G.; Tufino-Velazquez, M. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, 07738 Mexico D. F. (Mexico); Marin, E. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Instituto Politecnico Nacional, 11500 Mexico, D. F. (Mexico); Saucedo, E.; Ruiz, C.M.; Bermudez, V. [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2006-09-22

    A study of the physical properties of CdTe thin films doped with Bi is presented. CdTe:Bi thin films were deposited by the close space vapor transport (CSVT) technique using powdered CdTe:Bi crystals grown by the vertical Bridgman method. CdTe:Bi crystals were obtained with nominal Bi doping concentrations varying in the 1x10{sup 17}-8x10{sup 18}cm{sup -3} range. The physical properties of CdTe:Bi thin films were studied performing photoluminescence, X-ray, SEM, photoacoustic spectroscopy and resistivity measurements. We observed a decrease of the resistivity values of CdTe:Bi films with the Bi content as low as 6x10{sup 5}{omega}-cm for Bi concentrations of 8x10{sup 18}cm{sup -3}. These are meaningful results for CdTe-based solar cells. (author)

  8. N-Type Conductive Ultrananocrystalline Diamond Films Grown by Hot Filament CVD

    Directory of Open Access Journals (Sweden)

    Michael Mertens

    2015-01-01

    Full Text Available We present the synthesis of ultrananocrystalline diamond (UNCD films by application of hot filament chemical vapor deposition (HFCVD. We furthermore studied the different morphological, structural, and electrical properties. The grown films are fine grained with grain sizes between 4 and 7 nm. The UNCD films exhibit different electrical conductivities, dependent on grain boundary structure. We present different contact metallizations exhibiting ohmic contact behavior and good adhesion to the UNCD surface. The temperature dependence of the electrical conductivity is presented between −200 and 900°C. We furthermore present spectroscopic investigations of the films, supporting that the origin of the conductivity is the structure and volume of the grain boundary.

  9. Variable range hopping crossover and magnetotransport in PLD grown Sb doped ZnO thin film

    Science.gov (United States)

    Mukherjee, Joynarayan; Mannam, Ramanjaneyulu; Ramachandra Rao, M. S.

    2017-04-01

    We report on the variable range hopping (VRH) crossover in the electrical transport of Sb doped ZnO (SZO) thin film. Structural, chemical, electrical and magnetotransport properties were carried out on SZO thin film grown by pulsed laser deposition. X-photoelectron spectroscopy study confirms the presence of both Sb3+(33%) and Sb5+(67%) states. Sb doped ZnO thin film shows n-type behavior which is attributed to the formation of SbZn and/or SbZn–VZn defect complex. Temperature dependent resistivity measurement showed that in a low temperature regime (doped ZnO thin films is explained by the Khosla and Fischer model.

  10. Electrical transport and magnetic properties of epitaxial LSMO films grown on STO substrates

    Science.gov (United States)

    Yuan, Wei; Zhao, Yuelei; Su, Tang; Song, Qi; Han, Wei; Shi, Jing

    2015-03-01

    La0.7Sr0.3MnO3 (LSMO) is a very attractive material for spintronics due to its half-metallic ferromagnetic properties. The LSMO films are epitaxially grown on STO (100) substrates using pulsed laser deposition. The effects of substrate temperature, laser power, oxygen pressure, and annealing on the LSMO growth are systematically investigated by the reflection high energy electron diffraction and atomic force microscopy. Under the optimized growth condition, we have achieved atomically flat LSMO thin films with a wide terrace width of more than 5 micro-meters. The electrical transport properties of LSMO thin films of various thicknesses ranging from 8 to 20 monolayers are studied by measuring the resistivity as a function of temperature. We find that the growth condition plays an important role in the critical film thickness for the metal-insulator transition and the Curie temperature. The Ministry of Science and Technology of China.

  11. RBS study of in situ grown BiSrCaCuO films

    Energy Technology Data Exchange (ETDEWEB)

    Ranno, L.; Perriere, J.; Enard, J.P.; Kerherve, F.; Laurent, A.; Casero, R.P. (Paris-6 Univ., 75 (France). Lab. de Physique des Solides)

    1992-07-01

    BiSrCaCuO thin films have been grown in situ on MgO single crystals by pulsed laser deposition under 0.1 mbar oxygen pressure, the substrate temperature being around 700{sup o}C. These films are nearly pure 2212 phase, highly textured with a full c-axis orientation, and Rutherford backscattering spectrometry (RBS) in channeling geometry has been used to obtain precise information on their crystallinity. Although the X{sub min} values were found higher (about 35%) than those measured on bulk single crystals, they show partial epitaxy of the films, which was not observed with post annealed films. The comparison of backscattering yield in random and aligned orientations evidences the fact that all the cationic elements behave in a similar way in the channeling experiments, while differences are observed for the oxygen species according to their precise location in the network. These in situ grown films were found very sensitive to the ion irradiation, and showed a large dechanneling effect with increasing ion doses. (author).

  12. Transmission electron microscopy study of as-grown MgB{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Harada, Y. [Iwate Industry Promotion Center, 3-35-2 Iioka-shinden, Morioka 020-0852 (Japan)]. E-mail: yharada@luck.ocn.ne.jp; Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Kuroha, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Oba, T. [Faculty of Materials science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Seki, M. [Faculty of Materials science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Echigoya, J. [Faculty of Materials science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan)

    2006-10-01

    The intermetallic superconductor magnesium diboride (MgB{sub 2}) is a promising candidate for use in superconducting electronic devices because of its high transition temperature (T{sub c}). These applications require the development of a high-quality film fabrication process. We have previously reported the growth of MgB{sub 2} films deposited on MgO (1 0 0), SrTiO{sub 3} (1 0 0) and Al{sub 2}O{sub 3} (0 0 0 1) substrate using a co-evaporation method and molecular beam epitaxy (MBE) apparatus. In this paper, we will report the correlation between structural properties and physical properties of as-grown MgB{sub 2} films deposited on MgO (1 0 0), ZnO (0 0 0 1), and Si (1 1 1) substrate. The films' basal properties have been confirmed by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), resistivity measurements and SQUID magnetometry. The details of the interfacial structure were studied by transmission electron microscopy (TEM). We will then discuss the most important parameters for fabricating high quality as-grown MgB{sub 2} films and junctions.

  13. Yttria and ceria doped zirconia thin films grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    F. Saporiti

    2013-06-01

    Full Text Available The Yttria stabilized Zirconia (YSZ is a standard electrolyte for solid oxide fuel cells (SOFCs, which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol% Yttria stabilized Zirconia (8YSZ and films with addition of 4 weight% Ceria (8YSZ + 4CeO2 were grown by pulsed laser deposition (PLD technique using 8YSZ and 8YSZ + 4CeO2 targets and a Nd-YAG laser (355 nm. Films have been deposited on Soda-Calcia-Silica glass and Si(100 substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 µm were grown on different substrates.

  14. YBa2Cu3O7 films grown by metal cosputtering

    Science.gov (United States)

    Steinberg, Richard N.; McCambridge, James D.; Prober, Daniel E.; Guenin, Bruce M.

    1992-04-01

    Superconducting YBa2Cu3O7 films have been grown in situ by simultaneously sputtering from Y, BaCu, and Cu targets. One advantage of such metal cosputtering is the higher deposition rate compared to oxide target sputtering. Another advantage is the ability to control the individual element rates to vary composition or to substitute for any of the metals without interrupting film growth and without making additional composite targets. To prevent film damage due to oxygen ion bombardment during film growth which was observed when the sputter guns faced the substrate (on-axis sputtering), an off-axis geometry was used. One disadvantage we found with in situ metal cosputtering was that reproducibility of stoichiometries was difficult because of the presence of oxygen at the targets. To minimize the oxygen partial pressure at the targets during sputtering, the chamber was differentially pumped. Films grown in the off-axis geometry with a substrate temperature near 700 °C, a chamber pressure of 7.5 mT, and an O2:Ar flow ratio of 1:50 had zero resistance at 85 K. Results for on-axis, composite target magnetron sputtering with a high-strength magnet are also presented. These results are not promising.

  15. Yttria and ceria doped zirconia thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saporiti, F.; Juarez, R. E., E-mail: cididi@fi.uba.ar [Grupo de Materiales Avanzados, Facultad de Ingenieria, Universidad de Buenos Aires (Argentina); Audebert, F. [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Boudard, M. [Laboratoire des Materiaux et du Genie Physique (CNRS), Grenoble (France)

    2013-11-01

    The Yttria stabilized Zirconia (YSZ) is a standard electrolyte for solid oxide fuel cells (SOFCs), which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol% Yttria stabilized Zirconia (8YSZ) and films with addition of 4 weight% Ceria (8YSZ + 4CeO{sub 2}) were grown by pulsed laser deposition (PLD) technique using 8YSZ and 8YSZ + 4CeO{sub 2} targets and a Nd-YAG laser (355 nm). Films have been deposited on Soda-Calcia-Silica glass and Si(100) substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 Micro-Sign m were grown on different substrates (author)

  16. Group III-nitride thin films grown using MBE and bismuth

    Science.gov (United States)

    Kisielowski, Christian K.; Rubin, Michael

    2000-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  17. [Raman spectra studies of MBE-grown n-GaAs/SI-GaAs films].

    Science.gov (United States)

    Wang, Bin; Xu, Xiao-xuan; Qin, Zhe; Song, Ning; Zhang, Cun-zhou

    2008-09-01

    n-GaAs films doped with Si were grown by MBE on semi-insulated GaAs (100) substrates. The films with different doping concents were characterized by Raman spectra at room temperature. It is obviously that the Raman peaks shifted. Some peaks were enhanced and some were weakened. This is attributed to the fact that the higher the doping contents, the highertge lattice mismatch. And the lattice misfit induced the imperfection in epitaxy layers. This experimental result coincides with the theory.

  18. Surface organization of homoepitaxial InP films grown by metalorganic vapor-phase epitaxy

    OpenAIRE

    Gocalinska, A.; Manganaro, M.; Vvedensky, D. D.; Pelucchi, E.

    2012-01-01

    We present a systematic study of the morphology of homoepitaxial InP films grown by metalorganic vapor-phase epitaxy which are imaged with ex situ atomic force microscopy. These films show a dramatic range of different surface morphologies as a function of the growth conditions and substrate (growth temperature, V/III ratio, and miscut angle < 0.6deg and orientation toward A or B sites), ranging from stable step flow to previously unreported strong step bunching, over 10 nm in height. These o...

  19. Non-destructive characterization of films grown on Zircaloy-2 by annealing in air

    Energy Technology Data Exchange (ETDEWEB)

    McNatt, J.S.; Shepard, M.J.; Farkas, N.; Morgan, J.M.; Ramsier, R.D. [Departments of Physics, Chemistry, and Chemical Engineering, University of Akron, Akron, OH (United States)]. E-mail: rex@uakron.edu

    2002-08-07

    Zircaloy-2 is often used in engineering applications because of its corrosion resistance; a property attributable to a protective oxide film that grows on its surface. Variable angle infrared (IR) reflection spectroscopy and atomic force microscopy are used to determine the thickness and roughness of such films grown thermally on Zircaloy-2 surfaces in air. We find cubic growth kinetics in the temperature range 500-600 deg. C with an apparent activation energy of 227 kJ mol{sup -1}. We also demonstrate how an increase in microscopic surface roughness at higher temperatures correlates with a loss of oxide homogeneity as sampled by the IR method. (author)

  20. Solution-Grown Monocrystalline Hybrid Perovskite Films for Hole-Transporter-Free Solar Cells

    KAUST Repository

    Peng, Wei

    2016-03-02

    High-quality perovskite monocrystalline films are successfully grown through cavitation-triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3NH3PbBr3/Au, with near 100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole-transporter-free structure yield PCEs ≈6.5%, the highest among other similar-structured CH3NH3PbBr3 solar cells to date.

  1. 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)

  2. Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    Xu Zhihao; Zhang Jincheng; Duan Huantao; Zhang Zhongfen; Zhu Qingwei; Xu Hao; Hao Yue

    2009-01-01

    The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.

  3. Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Xu Zhihao; Zhang Jincheng; Duan Huantao; Zhang Zhongfen; Zhu Qingwei; Xu Hao; Hao Yue, E-mail: forman1115@163.co [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2009-12-15

    The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples. (semiconductor materials)

  4. Roughness of CdTe thin films grown on glass by hot wall epitaxy.

    Science.gov (United States)

    Leal, F F; Ferreira, S O; Menezes-Sobrinho, I L; Faria, T E

    2005-01-12

    Cadmium telluride films were grown on glass substrates using the hot wall epitaxy (HWE) technique. The samples were polycrystalline with a preferential (111) orientation. Scanning electron micrographs reveal a grain size between 0.1 and 0.5 µm. The surface morphology of the samples was studied by measuring the roughness profile using a stylus profiler. The roughness as a function of growth time and scale size were investigated to determine the growth and roughness exponents, β and α, respectively. From the results we can conclude that the growth surface has a self-affine character with a roughness exponent α equal to 0.69 ± 0.03 and almost independent of growth time. The growth exponent β was equal to 0.38 ± 0.06. These values agree with that determined previously for CdTe(111) films grown on GaAs(100).

  5. Photoinduced Br Desorption from CsBr Thin Films Grown on Cu(100)

    Energy Technology Data Exchange (ETDEWEB)

    Halliday, Matthew T.; Joly, Alan G.; Hess, Wayne P.; Shluger, AL

    2015-10-22

    Thin films of CsBr deposited onto metals such as copper are potential photocathode materials for light sources and other applications. We investigate desorption dynamics of Br atoms from CsBr films grown on insulator (KBr, LiF) and metal (Cu) substrates induced by sub-bandgap 6.4 eV laser pulses. The experimental results demonstrate that the peak kinetic energy of Br atoms desorbed from CsBr/Cu films is much lower than that for the hyperthermal desorption from CsBr/LiF films. Kelvin probe measurements indicate negative charge at the surface following Br desorption from CsBr/Cu films. Our ab initio calculations of excitons at CsBr surfaces demonstrate that this behavior can be explained by an exciton model of desorption including electron trapping at the CsBr surface. Trapped negative charges reduce the energy of surface excitons available for Br desorption. We examine the electron-trapping characteristics of low-coordinated sites at the surface, in particular, divacancies and kink sites. We also provide a model of cation desorption caused by Franck-Hertz excitation of F centers at the surface in the course of irradiation of CsBr/Cu films. These results provide new insights into the mechanisms of photoinduced structural evolution of alkali halide films on metal substrates and activation of metal photocathodes coated with CsBr.

  6. Chemical resistance of thin film materials based on metal oxides grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sammelselg, Väino, E-mail: vaino.sammelselg@ut.ee [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu (Estonia); Netšipailo, Ivan; Aidla, Aleks; Tarre, Aivar; Aarik, Lauri; Asari, Jelena; Ritslaid, Peeter; Aarik, Jaan [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)

    2013-09-02

    Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of < 5 pm/s. - Highlights: • Etching of atomic layer deposited thin metal oxide films in hot H{sub 2}SO{sub 4} was studied. • Smallest etching rates of < 5 pm/s for TiO{sub 2}, Al{sub 2}O{sub 3}, and Cr{sub 2}O{sub 3} were reached. • Highest etching rate of 2.8 nm/s for Al{sub 2}O{sub 3} was occurred. • Remarkable differences in etching of non- and crystalline films were observed.

  7. Biocompatibility of GaSb thin films grown by RF magnetron sputtering

    Science.gov (United States)

    Nishimoto, Naoki; Fujihara, Junko; Yoshino, Katsumi

    2017-07-01

    GaSb may be suitable for biological applications, such as cellular sensors and bio-medical instrumentation because of its low toxicity compared with As (III) compounds and its band gap energy. Therefore, the biocompatibility and the film properties under physiological conditions were investigated for GaSb thin films with or without a surface coating. GaSb thin films were grown on quartz substrates by RF magnetron sputtering, and then coated with (3-mercaptopropyl) trimethoxysilane (MPT). The electrical properties, surface morphology, and crystal structure of the GaSb thin film were unaffected by the MPT coating. The cell viability assay suggested that MPT-coated GaSb thin films are biocompatible. Bare GaSb was particularly unstable in pH9 buffer. Ga elution was prevented by the MPT coating, although the Ga concentration in the pH 9 buffer was higher than that in the other solutions. The surface morphology and crystal structure were not changed by exposure to the solutions, except for the pH 9 buffer, and the thin film properties of MPT-coated GaSb exposed to distilled water and H2O2 in saline were maintained. These results indicate that MPT-coated GaSb thin films are biocompatible and could be used for temporary biomedical devices.

  8. Structural and electrical properties of large area epitaxial VO2 films grown by electron beam evaporation

    Science.gov (United States)

    Théry, V.; Boulle, A.; Crunteanu, A.; Orlianges, J. C.; Beaumont, A.; Mayet, R.; Mennai, A.; Cosset, F.; Bessaudou, A.; Fabert, M.

    2017-02-01

    Large area (up to 4 squared inches) epitaxial VO2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 10 4 , have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where the distortions are confined close to the interface which allows growth of high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with a RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties.

  9. The effect of ultraviolet irradiation on the ultra-thin HfO2 based CO gas sensor

    Science.gov (United States)

    Karaduman, Irmak; Barin, Ã.-zlem; Yıldız, Dilber Esra; Acar, Selim

    2015-11-01

    In this work, an effort has been made to fabricate ultrathin HfO2/Al2O3 sample by atomic layer deposition method for the fast detection of CO gas at room temperature. The effect of the operating temperature and the UV light on the gas sensing characteristics has been studied. We investigated the optimum operating temperature for the sample by sensing 25 ppm CO and CO2 gases from room temperature to 150 °C for 10 °C steps. The maximum response was obtained at 150 °C for both gases in the measurement temperature range. Also, the photoresponse measurements clearly show the effect of UV light on the sample. At room temperature, sensor showed superior response (14%) for 5 ppm CO gas. The response time of sensor is 6 s to 5 ppm CO gas concentration. The ultrathin HfO2 based sample shows acceptable gas sensitivity for 5 ppm CO gas at room temperature under UV light irradiation.

  10. Elastic properties of B-C-N films grown by N{sub 2}-reactive sputtering from boron carbide targets

    Energy Technology Data Exchange (ETDEWEB)

    Salas, E.; Jiménez Riobóo, R. J.; Jiménez-Villacorta, F.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Sánchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Dept. Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Muñoz-Martín, A.; Prieto, J. E.; Joco, V. [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2013-12-07

    Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B{sub 4}C target and N{sub 2} as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.

  11. Characterizations of Cubic ZnMgO Films Grown on Si(111) at Low Substrate Temperature

    Institute of Scientific and Technical Information of China (English)

    邱东江; 吴惠桢; 陈乃波; 徐天宁

    2003-01-01

    Cubic ZnMgO thin films in the (100) orientation were grown on Si (111) substrates by reactive electron beamevaporation at low substrate temperature. X-ray photoelectron spectroscopy (XPS) analyses show that Mgcontent as high as 75 at.% in the cubic ZnMgO film can be obtained. Secondary ion mass spectroscopy (SIMS)measurement indicates the evidence of Mg richness in the interface between the ZnMgO film and the Si substrate,and it is probably the primary reason to form the MgO-like cubic ZnMgO structures rather than the wurtziteone. The optical band gap of cubic ZnMgO is estimated to be 5.76eV, which was measured by the transmissionspectrum of the cubic ZnMgO film grown on the sapphire substrate under the same growth condition with thaton Si (111). The band gap is of 2.39eV blueshifted compared with that of ZnO (3.37eV), which should renderapplications in the fabrication of ZnMgO-related heterostructures.

  12. Structural and electrical properties of tantalum oxide films grown by photo-assisted pulsed laser deposition

    Science.gov (United States)

    Zhang, Jun-Ying; Boyd, Ian W.

    2002-01-01

    We describe the growth of thin films of Ta 2O 5 on quartz and silicon (1 0 0) substrates by an in situ photo-assisted pulsed laser deposition (photo-PLD) using radiation from a Nd:YAG laser (wavelength, λ=532 nm) to stimulate the ablation, and from an excimer lamp to excite additional photochemistry. The layers grown were investigated by Fourier transform infrared (FT-IR) spectroscopy, UV spectrophotometry, atomic force microscopy (AFM), ellipsometry and electrical measurements. We have found that they exhibit a significant improvement in microstructure, and optical and electrical properties compared with conventional PLD films prepared under, otherwise, identical conditions. For example, FT-IR results showed that the suboxide content in the as-grown films deposited by the photo-PLD process is less, while the leakage current density was an order of magnitude less at around 10 -6 A/cm 2 at a bias of 1 V. These results indicate that this photo-PLD process approach can be advantageous for dielectric and optical oxide film growth.

  13. Influence of solution viscosity on hydrothermally grown ZnO thin films for DSSC applications

    Science.gov (United States)

    Marimuthu, T.; Anandhan, N.; Thangamuthu, R.; Surya, S.

    2016-10-01

    Zinc oxide (ZnO) nanowire arrays (NWAs) were grown onto zinc oxide-titanium dioxide (ZnO-TiO2) seeded fluorine doped tin oxide (FTO) conductive substrate by hydrothermal technique. X-ray diffraction (XRD) patterns depict that ZnO thin films are preferentially oriented along the (002) plane with hexagonal wurtzite structure. Viscosity measurements reveal that viscosity of the solutions linearly increases as the concentrations of the polyvinyl alcohol (PVA) increase in the growth solution. Field emission scanning electron microscope (FE-SEM) images show that the NWAs are vertically grown to seeded FTO substrate with hexagonal structure, and the growth of NWAs decreases as the concentration of the PVA increases. Stylus profilometer and atomic force microscopic (AFM) studies predict that the thickness and roughness of the films decrease with increasing the PVA concentrations. The NWAs prepared at 0.1% of PVA exhibits a lower transmittance and higher absorbance than that of the other films. The band gap of the optimized films prepared at 0.0 and 0.1% of PVA is found to be 3.270 and 3.268 eV, respectively. The photo to current conversion efficiency of the DSSC based on photoanodes prepared at 0.0 and 0.1% of PVA exhibits about 0.64 and 0.82%, respectively. Electrochemical impedance spectra reveal that the DSSC based on photoanode prepared at 0.1% of PVA has the highest charge transfer recombination resistance.

  14. Surface state conductivity in epitaxially grown Bi1-x Sb x (111) films

    Science.gov (United States)

    Koch, Julian; Kröger, Philipp; Pfnür, Herbert; Tegenkamp, Christoph

    2016-09-01

    Topologically non-trivial surface states were reported first on {{Bi}}1-xSb x bulk crystals. In this study we present transport measurements performed on thin {{Bi}}1-xSb x -films (up to 24 nm thickness) grown epitaxially on Si(111) with various Sb-concentrations (up to x = 0.22). The analysis of the temperature dependency allowed us to distinguish between different transport channels originating from surface and bulk bands as well as impurity states. At temperatures below 30 K the transport is mediated by surface states while at higher temperatures activated transport via bulk channels sets in. The surface state conductivity and bulk band gaps can be tuned by the Sb-concentration and film thickness, respectively. For films as thin as 4 nm the surface state transport is strongly suppressed in contrast to Bi(111) films grown under identical conditions. The impurity channel is of intrinsic origin due to the growth and alloy formation process and turns out to be located at the buried interface.

  15. Memory window widening of Pt/SrBi2Ta2O9/HfO2/Si ferroelectric-gate field-effect transistors by nitriding Si

    Science.gov (United States)

    Horiuchi, Takeshi; Takahashi, Mitsue; Ohhashi, Kentaro; Sakai, Shigeki

    2009-10-01

    The optimum temperature of rapid thermal nitridation (RTN) of Si substrates was investigated for minimizing an equivalent oxide thickness (EOT) of an interfacial layer (IL) which was grown between HfO2 and Si of Pt/SrBi2Ta2O9(SBT)/HfO2/Si ferroelectric-gate field-effect transistors (FeFETs) during a post-annealing process. The RTN was performed in NH3 gas at various temperatures ranging from 800 °C to 1190 °C. As the RTN temperature was raised from 800 °C to 1080 °C, memory windows of drain current-gate voltage curves became wider. Large memory windows were obtained at the range from 1020 °C to 1130 °C. The maximum was 1.36 V obtained at 1080 °C. It was 10% larger than the typical values of Pt/SBT/HfO2/Si FeFETs without the RTN. At higher RTN temperatures than 1080 °C, the memory windows tended to decrease. At 800 °C and 1190 °C, all layer boundaries among SBT-HfO2-IL-Si seemed unclear in scanning transmission electron microscopic views probably due to material diffusions. The optimum RTN temperature for minimizing the EOT of the IL and maximizing the memory window of the Pt/SBT/HfO2/SiNx/Si FeFET was 1080 °C. The FeFET using the Si processed by the RTN at 1080 °C also showed good retentions without significant degradations over two days.

  16. Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

    Science.gov (United States)

    Miikkulainen, Ville; Leskelä, Markku; Ritala, Mikko; Puurunen, Riikka L.

    2013-01-01

    Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas-solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic-organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

  17. MgB{sub 2} thin films grown on graphene/Ni–Mo alloy system

    Energy Technology Data Exchange (ETDEWEB)

    Linghu, Kehuan, E-mail: linghukehuan@126.com [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China); Song, Qingjun [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Zhang, Huai [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China); Yang, QianQian [College of Applied Sciences, Beijing University of Technology, Beijing 100124 (China); Zhang, Jibo; Wu, Qianhong; Nie, Ruijuan [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China); Dai, Lun [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Feng, Qingrong; Wang, Furen [School of Physics and State Key Laboratory for Artificial Structure and Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2015-09-15

    Highlights: • Depositing MgB{sub 2} thin films on graphene/Ni–Mo alloy substrate by HPCVD is a completely new method. • The growth of MgB{sub 2} thin films in this system lays a good foundation of depositing MgB{sub 2} thick films. • We directly deposite MgB{sub 2} films on graphene(without transferring) which keeps graphene’s original morphology and properties. - Abstract: 200 nm Ni film is coated on 25 μm thick Mo foil, and graphene is grown on the Ni–Mo system by CVD method. After the annealing process of CVD, the Ni/Mo bilayer transforms into Ni–Mo alloy, then we have successfully fabricated MgB{sub 2} films on graphene/Ni–Mo alloy system via the hybrid physical–chemical vapor deposition (HPCVD) technique. The transition temperature T{sub c} onset is 38.25 K with a corresponding transition width of 0.75 K. The average thickness of MgB{sub 2} films is 200 nm (25% concentration B{sub 2}H{sub 6}). The critical current density derives from the magnetization measurement at 5 K is, j{sub c} (5 K, 0 T) = 9.6 × 10{sup 6} A/cm{sup 2}. We can easily deposite MgB{sub 2} on graphene/Ni–Mo alloy system with a lower B{sub 2}H{sub 6} concentration and less gas flow, which lays a good foundation for depositing MgB{sub 2} thick films. The graphene in this system is multilayer and with defects, it may act like an intermediary film for the growth of MgB{sub 2}, or a carbon-doping source.

  18. Preparation and structural properties of YBCO films grown on GaN/c-sapphire hexagonal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chromik, S., E-mail: stefan.chromik@savba.sk [Institute of Electrical Engineering, SAS, Dubravska cesta 9, 84104 Bratislava (Slovakia); Gierlowski, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Spankova, M.; Dobrocka, E.; Vavra, I.; Strbik, V.; Lalinsky, T.; Sojkova, M. [Institute of Electrical Engineering, SAS, Dubravska cesta 9, 84104 Bratislava (Slovakia); Liday, J.; Vogrincic, P. [Department of Microelectronics, Slovak Technical University, Ilkovicova 3, 81219 Bratislava (Slovakia); Espinos, J.P. [Instituto de Ciencia de Materiales de Sevilla, Avda Americo Vespucio 49, 41092 Sevilla (Spain)

    2010-07-01

    Epitaxial YBCO thin films have been grown on hexagonal GaN/c-sapphire substrates using DC magnetron sputtering and pulsed laser deposition. An MgO buffer layer has been inserted between the substrate and the YBCO film as a diffusion barrier. X-ray diffraction analysis indicates a c-axis oriented growth of the YBCO films. {Phi}-scan shows surprisingly twelve maxima. Transmission electron microscopy analyses confirm an epitaxial growth of the YBCO blocks with a superposition of three a-b YBCO planes rotated by 120 deg. to each other. Auger electron spectroscopy and X-ray photoelectron spectroscopy reveal no surface contamination with Ga even if a maximum substrate temperature of 700 deg. C is applied.

  19. Lithium outdiffusion in LiTi2O4 thin films grown by pulsed laser deposition

    Science.gov (United States)

    Mesoraca, S.; Kleibeuker, J. E.; Prasad, B.; MacManus-Driscoll, J. L.; Blamire, M. G.

    2016-11-01

    We report surface chemical cation composition analysis of high quality superconducting LiTi2O4 thin films, grown epitaxially on MgAl2O4 (111) substrates by pulsed laser deposition. The superconducting transition temperature of the films was 13.8 K. Surface chemical composition is crucial for the formation of a good metal/insulator interface for integrating LiTi2O4 into full-oxide spin-filtering devices in order to minimize the formation of structural defects and increase the spin polarisation efficiency. In consideration of this, we report a detailed angle resolved x-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTi2O4 films. We attribute this process due to outdiffusion of Li toward the outermost LiTi2O4 layers.

  20. 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.

  1. 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.

  2. Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

    Science.gov (United States)

    György, E.; Pérez del Pino, A.; Sauthier, G.; Figueras, A.

    2009-12-01

    Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ =248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well as target preparation procedure.

  3. RAPID COMMUNICATION: ? thin film bilayers grown by pulsed laser ablation deposition

    Science.gov (United States)

    Singh, S. K.; Palmer, S. B.; McK Paul, D.; Lees, M. R.

    1996-09-01

    We have grown superconducting thin films of 0022-3727/29/9/044/img2 (Y-123) on 0022-3727/29/9/044/img3 (PCMO) buffer layers and PCMO overlayers on Y-123 thin films using pulsed laser ablation deposition. For both sets of films below 50 K, the Y-123 layer is superconducting and the zero-field cooled PCMO layer is insulating. The application of a magnetic field of 8 T results in an insulator - metal transition in the PCMO layer. This field-induced conducting state is stable in zero magnetic field at low temperature. The PCMO layer can be returned to an insulating state by annealing above 100 K. This opens the way for the construction of devices incorporating these oxide materials in which the electronic properties of key components such as the substrate or the barrier layer can be switched in a controlled way by the application of a magnetic field.

  4. Photoluminescence properties of MgxZn1-xO films grown by molecular beam epitaxy

    Science.gov (United States)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Chou, W. C.; Shen, J. L.

    2017-02-01

    The optical properties of MgxZn1-xO films with x=0.03, 0.06, 0.08, and 0.11 grown by molecular beam epitaxy (MBE) have been studied by temperature-dependent photoluminescence (PL) measurement. It is presented that the full-width at half-maximum (FWHM) of the 12 K PL spectrum of MgZnO films increases with increasing Mg concentration and would deviate significantly from the simulation curve of Schubert model with higher Mg contents. The abnormal broader PL FWHM is inferred from larger compositional fluctuation by incorporating higher Mg contents, which results in larger effect of excitonic localization to induce more significant S-shaped behavior of the PL peak energy with temperature dependence. Additionally, the degree of localization increases as the linear proportion of the PL FWHM, indicating that the excitonic behavior in MgZnO films belong to the strong localization effect.

  5. Polycrystalline GaSb thin films grown by co-evaporation

    Institute of Scientific and Technical Information of China (English)

    Qiao Zaixiang; Sun Yun; He Weiyu; He Qing; Li Changjian

    2009-01-01

    We report optical and electrical properties of polycrystalline GaSb thin films which were successfully grown by co-evaporation on soda-lime glass substrates. The thin films have preferential orientation of the (111)direction. SEM results indicate that the average grain size of GaSb thin film is 500 nm with the substrate temperature of 560 ℃. The average reflectance of GaSb thin film is about 30% and the absorption coefficient is of the order of 104 cm-1. The optical bandgap of GaSb thin film is 0.726 eV. The hole concentration shows a clear increasing trend as the Ga-evaporation-temperature/Sb-evaporation-temperature (TGa/TSb) ratio increases. When the Ga crucible temperature is 810 ℃ and the antinomy crucible temperature is 415 ℃, the hole concentration of polycrystalline GaSb is 2 x 1017 cm-3 and the hole mobility is 130 cm2/(V-s). These results suggest that polycrystalline GaSb thin film is a good candidate for the use as a cheap material in TPV cells.

  6. Preparation and chemical characterization of neodymium-doped molybdenum oxide films grown using spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Alfonso, J. E. [Universidad Nacional de Colombia, Departamento de Fisica, Grupo de Ciencia Materiales y Superficies, AA 5997 Bogota DC (Colombia); Moreno, L. C., E-mail: jealfonsoo@unal.edu.co [Universidad Nacional de Colombia, Departamento de Quimica, AA 5997 Bogota DC (Colombia)

    2014-07-01

    We studied the crystalline, morphology, and surface composition of Nd-doped molybdenum oxide films grown on glass slides through spray pyrolysis. After fabrication, the films were subjected to thermal treatment in oxygen for periods ranging from 2 to 20 hours. The films were structurally characterized though X-ray diffraction (XRD), their bulk chemical composition was determined using Energy-Dispersive X-ray analysis (EDX), and their surface composition was determined using X-ray Photoelectron Spectroscopy (XP S). The XRD results show that the films obtained from different dissolution volumes and at substrate temperature of 300 grades C exhibit the characteristics of the oxygen-deficient molybdenum trioxide Mo{sub 9}O{sub 26} phase. The films subjected to different thermal treatments exhibit a mixture of Mo{sub 9}O{sub 26} and Mo{sub 17}O{sub 47} phases. EDX study shows the energy belonging to the L line of Nd. Finally, films doped with Nd and subjected to a thermal treatment of 20 h were analyzed through XP S, showing the binding energies at the crystalline lattice correspond to Nd{sub 2} (MoO{sub 4}){sub 3} and Nd{sub 2}Mo{sub 2}O{sub 7}. (Author)

  7. Electronic structure analysis of GaN films grown on r- and a-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Monu; Krishna TC, Shibin; Aggarwal, Neha [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Vihari, Saket [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Gupta, Govind, E-mail: govind@nplindia.org [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)

    2015-10-05

    Graphical abstract: Substrate orientation induced changes in surface chemistry, band bending, hybridization states, electronic properties and surface morphology of epitaxially grown GaN were investigated via photoemission spectroscopic and Atomic Force Microscopic measurements. - Highlights: • Electronic structure and surface properties of GaN film grown on r/a-plane sapphire. • Downward band bending (0.5 eV) and high surface oxide is observed for GaN/a-sapphire. • Electron affinity and ionization energy is found to be higher for GaN/a-sapphire. - Abstract: The electronic structure and surface properties of epitaxial GaN films grown on r- and a-plane sapphire substrates were probed via spectroscopic and microscopic measurements. X-ray photoemission spectroscopic (XPS) measurements were performed to analyse the surface chemistry, band bending and valence band hybridization states. It was observed that GaN/a-sapphire display a downward band bending of 0.5 eV and possess higher amount of surface oxide compared to GaN/r-sapphire. The valence band (VB) investigation revealed that the hybridization corresponds to the interactions of Ga 4s and Ga 4p orbitals with N 2p orbital, and result in N2p–Ga4p, N2p–Ga4s{sup ∗}, mixed and N2p–Ga4s states. The energy band structure and electronic properties were measured via ultraviolet photoemission spectroscopic (UPS) experiments. The band structure analysis and electronic properties calculations divulged that the electron affinity and ionization energy of GaN/a-sapphire were 0.3 eV higher than GaN/r-sapphire film. Atomic Force Microscopic (AFM) measurements revealed faceted morphology of GaN/r-sapphire while a smooth pitted surface was observed for GaN/a-sapphire film, which is closely related to surface oxide coverage.

  8. Ferroelastic domain organization and precursor control of size in solution-grown hafnium dioxide nanorods.

    Science.gov (United States)

    Depner, Sean W; Cultrara, Nicholas D; Farley, Katie E; Qin, Yueling; Banerjee, Sarbajit

    2014-05-27

    We demonstrate that the degree of branching of the alkyl (R) chain in a Hf(OR)4 precursor allows for control over the length of HfO2 nanocrystals grown by homocondensation of the metal alkoxide with a metal halide. An extended nonhydrolytic sol-gel synthesis has been developed that enables the growth of high aspect ratio monoclinic HfO2 nanorods that grow along the [100] direction. The solution-grown elongated HfO2 nanorods show remarkable organization of twin domains separated by (100) coherent twin boundaries along the length of the nanowires in a morphology reminiscent of shape memory alloys. The sequence of finely structured twin domains each spanning only a few lattice planes originates from the Martensitic transformation of the nanorods from a tetragonal to a monoclinic structure upon cooling. Such ferroelastic domain organization is uncharacteristic of metal oxides and has not thus far been observed in bulk HfO2. The morphologies observed here suggest that, upon scaling to nanometer-sized dimensions, HfO2 might exhibit mechanical properties entirely distinctive from the bulk.

  9. Vacuum ultraviolet annealing of thin films grown by pulsed laser deposition

    Science.gov (United States)

    Craciun, Valentin; Craciun, Doina; Andreazza, Pascal; Perriere, Jacques; Boyd, Ian W.

    1999-01-01

    The effect of a post-deposition annealing treatment in 1 bar of oxygen at moderate temperatures (excimer lamp upon thin ZrO 2 and hydroxyapatite (HAp) films grown by the pulsed laser deposition (PLD) technique was investigated. The optical and structural properties of the films were improved by this treatment, the lower the deposition temperature and, accordingly, the poorer the initial characteristics, the more significant the improvements. The combination of these two techniques allowed us to obtain at temperatures below 350°C highly textured (020) ZrO 2 films, exhibiting optical absorption coefficients lower than 5×10 2 cm -1 and high refractive index values of around 2.25 in the visible region of the spectrum. The VUV treatment was also beneficial for the partially crystalline HAp layers containing tetracalcium phosphate and calcium oxide phases grown by the PLD technique under a low pressure oxidising atmosphere of only 10 -5 torr without any water vapours. After the VUV-assisted anneal, the crystalline structure and the stoichiometry greatly improved while the percentage of the other crystalline phases initially present was many times reduced.

  10. AFM Study on Interface of HTHP As-grown Diamond Single Crystal and Metallic Film

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The study for the interface of as-grown diamond and metallic film surrounding diamond is an attractive way for understanding diamond growth mechanism at high temperature and high pressure (HTHP), because it is that through the interface carbon atom groups from the molten film are transported to growing diamond surface. It is of great interest to perform atomic force microscopy (AFM) experiment, which provides a unique technique different from that of normal optical and electron microscopy studies, to observe the interface morphology. In the present paper,we report first that the morphologies obtained by AFM on the film are similar to those of corresponding diamond surface, and they are the remaining traces after the carbon groups moving from the film to growing diamond. The fine particles and a terrace structure with homogeneous average step height are respectively found on the diamond (100) and (111) surface. Diamond growth conditions show that its growth rates and the temperature gradients in the boundary layer of the molten film at HTHP result in the differences of surface morphologies on diamond planes,being rough on (100) plane and even on the (111) plane. The diamond growth on the (100) surface at HPHT could be considered as a process of unification of these diamond fine particles or of carbon atom groups recombination on the growing diamond crystal surface. Successive growth layer steps directly suggest the layer growth mechanism of the diamond (111) plane. The sources of the layer steps might be two-dimensional nuclei and dislocations.

  11. Transparent conductive Al-doped ZnO thin films grown at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  12. Thermal evolution of Er silicate thin films grown by rf magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Lo Savio, R; Miritello, M; Piro, A M; Grimaldi, M G; Priolo, F [MATIS CNR-INFM and Dipartimento di Fisica e Astronomia dell' Universita di Catania, via Santa Sofia 64, 95123 Catania (Italy); Iacona, F [CNR-IMM, Stradale Primosole 50, 95121 Catania (Italy)], E-mail: roberto.losavio@ct.infn.it

    2008-11-12

    Stoichiometric Er silicate thin films, monosilicate (Er{sub 2}SiO{sub 5}) and disilicate (Er{sub 2}Si{sub 2}O{sub 7}), have been grown on c-Si substrates by rf magnetron sputtering. The influence of annealing temperature in the range 1000-1200 deg. C in oxidizing ambient (O{sub 2}) on the structural and optical properties has been studied. In spite of the known reactivity of rare earth silicates towards silicon, Rutherford backscattering spectrometry shows that undesired chemical reactions between the film and the substrate can be strongly limited by using rapid thermal treatments. Monosilicate and disilicate films crystallize at 1100 and 1200 deg. C, respectively, as shown by x-ray diffraction analysis; the crystalline structures have been identified in both cases. Moreover, photoluminescence (PL) measurements have demonstrated that the highest PL intensity is obtained for Er{sub 2}Si{sub 2}O{sub 7} film annealed at 1200 deg. C. In fact, this treatment allows us to reduce the defect density in the film, in particular by saturating oxygen vacancies, as also confirmed by the increase of the lifetime of the PL signal.

  13. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Directory of Open Access Journals (Sweden)

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  14. Characterization of Perovskite Films Grown by a Novel Low-Temperature Process for Uncooled IR Detector Applications

    Science.gov (United States)

    2008-12-01

    and semiconductor thin- films (Schwenzer et al., 2006; Kisailus et al, 2006; Brutchey and Morse, 2006). The resulting pyroelectric, perovskite -based...1 CHARACTERIZATION OF PEROVSKITE FILMS GROWN BY A NOVEL LOW- TEMPERATURE PROCESS FOR UNCOOLED IR DETECTOR APPLICATIONS W.L. Sarney* and J.W...multimetallic perovskite nanoparticle deposition, direct-write digitally-scripted laser phase conversion, and MEMS fabrication and optimization

  15. A tunneling current density model for ultra thin HfO2 high-k dielectric material based MOS devices

    Science.gov (United States)

    Maity, Niladri Pratap; Maity, Reshmi; Thapa, R. K.; Baishya, Srimanta

    2016-07-01

    In this paper, an analytical model for evaluation of tunneling current density of ultra thin MOS devices is presented. The impacts of the promising high-k dielectric material, HfO2 on the current density model have been carried out. In this work, improvement in the results is brought in by taking into account the barrier height lowering due to the image force effect. The considered voltage range is from 0 to ψ1/e i.e., 0 neglecting the image force effect for a MOS device consisting asymmetric barrier. Later, image force effect of ultra thin oxide layer has been introduced for practical potential barrier by superimposing the potential barrier on the trapezoidal barrier. Theoretical predictions are compared with the results obtained by the 2-D numerical device simulator ATLAS and published experimental results. Excellent agreements among the three are observed.

  16. Photoluminescence properties of ZnO films grown on InP by thermally oxidizing metallic Zn films

    CERN Document Server

    Chen, S J; Zhang, J Y; Lu, Y M; Shen, D Z; Fan, X W

    2003-01-01

    Photoluminescence (PL) properties of ZnO films grown on (001) InP substrates by thermal oxidization of metallic Zn films, in which oxygen vacancies and interstitial Zn ions are compensated by P ions diffusing from (001) InP substrates, are investigated. X-ray diffraction spectra indicate that P ions have diffused into the Zn films and chemically combined with Zn ions to form Zn sub 3 P sub 2. Intense free exciton emission dominates the PL spectra of ZnO films with very weak deep-level emission. Low-temperature PL spectra at 79 K are dominated by neutral-donor bound exciton emission at 3.299 eV (I sub 4) with a linewidth of 17.3 meV and neutral-acceptor bound exciton emission at 3.264 eV. The free exciton emission increases with increasing temperature and eventually dominates the emission spectrum for temperature higher than 170 K. Furthermore, the visible emission around 2.3 eV correlated with oxygen deficiencies and interstitial Zn defects was quenched to a remarkable degree by P diffusing from InP substrate...

  17. Preparation and characterization of ferroelectric Hf0.5Zr0.5O2 thin films grown by reactive sputtering

    Science.gov (United States)

    Lee, Young Hwan; Kim, Han Joon; Moon, Taehwan; Do Kim, Keum; Dam Hyun, Seung; Park, Hyeon Woo; Lee, Yong Bin; Park, Min Hyuk; Hwang, Cheol Seong

    2017-07-01

    HfO2-ZrO2 solid-solution films were prepared by radio frequency sputtering, and the subsequent annealing process was optimized to render enhanced ferroelectric behavior. The target power, working pressure and O2 partial pressure ratios were varied, along with the annealing gas, time and temperature. Then, the film’s structural and electrical properties were carefully scrutinized. Oxygen-deficient conditions were necessary during the sputter deposition to suppress grain growth, while annealing by O2 gas was critical to avoid defects and leakage problems. It is expected that the grain size difference under various deposition conditions combined with the degree of TiN top and bottom electrode oxidation by O2 gas will result in different ferroelectric behaviors. As a result, Hf0.5Zr0.5O2 prepared by radio frequency sputtering showed optimized ferroelectricity at 0% of O2 reactive gas, with a doubled remnant polarization value of ˜20 μC cm-2 at a thickness of 11 nm. Film growth conditions with a high growth rate (4-5 nm min-1) were favorable for achieving the ferroelectric phase film, which feasibly suppressed both the grain growth and accompanying monoclinic phase formation.

  18. The effect of different annealing conditions in undoped and Ag doped ZnO thin films grown by SILAR method

    OpenAIRE

    GÜNEY, HARUN

    2015-01-01

    Undoped, %3 and %5 Silver (Ag) doped zinc oxide (ZnO) thin films have been grown on glass substrates by simple and economic successive ionic layer absorption and reaction method (SILAR). All grown films were annealed vacuum and air to investigate to effective annealing at 573 K for 30 minutes. Energy-Dispersive-X-Ray-Fluorescence (EDXRF) spectroscopy showed %3 and %5 dopants Ag. Absorbance measurements showed that the optical band-gaps of all thin films were wide and generally decrease with a...

  19. Growth and structure of MBE grown TiO2 anatase films with rutile nano-crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Rui; Wang, Chong M.; McCready, David E.; Droubay, Timothy C.; Chambers, Scott A.

    2007-03-15

    We have grown TiO2 anatase films with rutile nanocrystalline inclusions using molecular beam epitaxy under different growth conditions. This model system is important for investigating the role of rutile/anatase interfaces in heterogeneous photocatalysis. To control the film structure, we grew a pure anatase (001) layer at a slow rate and then increased the growth rate to drive the nucleation of rutile particles. Structure analysis indicates that the rutile phase has four preferred orientations in the anatase film.

  20. SEM, EDS, PL and absorbance study of CdTe thin films grown by CSS method

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Torres, M.E.; Silva-Gonzalez, R.; Gracia-Jimenez, J.M. [Instituto de Fisica, BUAP, Apdo. Postal J-48, San Manuel, 72570 Puebla, Pue. (Mexico); Casarrubias-Segura, G. [CIE- UNAM, 62580 Temixco, Morelos (Mexico)

    2006-09-22

    Oxygen-doped CdTe films were grown on conducting glass substrates by the close spaced sublimation (CSS) method and characterized using SEM, EDS, photoluminescence (PL) and absorbance. A significant change in the polycrystalline morphology is observed when the oxygen proportion is increased in the deposition atmosphere. The EDS analysis showed that all samples are nonstoichiometric with excess Te. The PL spectra show emission bands associated with Te vacancies (V{sub Te}), whose intensities decrease as the oxygen proportion in the CSS chamber is increased. The oxygen impurities occupy Te vacancies and modify the surfaces states, improving the nonradiative process. (author)

  1. Preparation of AgInSe2 thin films grown by vacuum evaporation method

    Science.gov (United States)

    Matsuo, H.; Yoshino, K.; Ikari, T.

    2006-09-01

    Polycrystalline AgInSe2 thin films were successfully grown on glass substrates by an evaporation method. The starting materials were stoichiometrically mixed Ag2Se and In2Se3 powders. X-ray diffraction revealed that the sample annealed at 600 °C consisted of AgInSe2 single phase, with (112) orientation and a large grain size. The lattice constant (a axis) was close to JCPDS values. From optical transmittance and reflectance measurements, the bandgap energy was estimated to be 1.17 eV.

  2. Tantalum films with well-controlled roughness grown by oblique incidence deposition

    Science.gov (United States)

    Rechendorff, K.; Hovgaard, M. B.; Chevallier, J.; Foss, M.; Besenbacher, F.

    2005-08-01

    We have investigated how tantalum films with well-controlled surface roughness can be grown by e-gun evaporation with oblique angle of incidence between the evaporation flux and the surface normal. Due to a more pronounced shadowing effect the root-mean-square roughness increases from about 2 to 33 nm as grazing incidence is approached. The exponent, characterizing the scaling of the root-mean-square roughness with length scale (α), varies from 0.75 to 0.93, and a clear correlation is found between the angle of incidence and root-mean-square roughness.

  3. Electron trapping properties at HfO2/SiO2 interface, studied by Kelvin probe force microscopy and theoretical analysis

    Science.gov (United States)

    Zhang, Man-Hong

    2016-08-01

    Electron trapping properties at the HfO2/SiO2 interface have been measured through Kelvin Probe force microscopy, between room temperature and 90 °C. The electron diffusion in HfO2 shows a multiple-step process. After injection, electrons diffuse quickly toward the HfO2/SiO2 interface and then diffuse laterally near the interface in two sub-steps: The first is a fast diffusion through shallow trap centers and the second is a slow diffusion through deep trap centers. Evolution of contact potential difference profile in the fast lateral diffusion sub-step was simulated by solving a diffusion equation with a term describing the charge loss. In this way, the diffusion coefficient and the average life time at different temperatures were extracted. A value of 0.57 eV was calculated for the activation energy of the shallow trap centers in HfO2. Project supported by the National Natural Science Foundation of China (Grant No. 61176080).

  4. Room-temperature ferromagnetism in V-doped GaN thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Souissi, M.; El Jani, B. [Unite de Recherche sur les Hetero-Epitaxies et Applications, Faculte des Sciences de Monastir, 5000 Monastir (Tunisia); Schmerber, G.; Derory, A. [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR7504 CNRS-UDS, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France)

    2010-09-15

    V-doped GaN thin films were grown on c-sapphire substrate by metal organic chemical vapour deposition method (MOCVD). We have used vanadium tetrachloride (VCl{sub 4}) to intentionally incorporate vanadium (V) during the crystal growth of GaN. X-ray diffraction measurements revealed no secondary phase in the samples. Magnetic experiments using superconducting quantum interference device (SQUID) showed clear hysteresis loop in magnetization versus applied field (M -H) curves for V-doped GaN films. The ferromagnetic behavior was evidenced at 300 K, implying the Curie temperature to be over 300 K. Strong and broad blue-luminescent band (centered at 2.6 eV) is induced by the V doping in GaN. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Growth and Characterization of Semi-Insulating GaN Films Grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    High resistivity unintentionally doped GaN films were grown on (0001) sapphire substrates by metalorganic chemical vapor deposition. The surface morphology of the layer was measured by both atomic force microscopy and scanning electron microscopy. The results show that the films have mirror-like surface morphology with root mean square of 0.3 nm. The full width at half maximum of double crystal X-ray diffraction rocking curve for (0002) GaN is about 5.22 arcmin, indicative of high crystal quality. The resistivity of the GaN epilayers at room temperature and at 250 ℃ was measured to be approximate 109 and 106 Ω·cm respectively, by variable temperature Hall measurement. Deep level traps in the GaN epilayers were investigated by thermally stimulated current and resistivity measurements.

  6. Scaling behavior of the surface roughness of platinum films grown by oblique angle deposition

    Science.gov (United States)

    Dolatshahi-Pirouz, A.; Hovgaard, M. B.; Rechendorff, K.; Chevallier, J.; Foss, M.; Besenbacher, F.

    2008-03-01

    Thin platinum films with well-controlled rough surface morphologies are grown by e-gun evaporation at an oblique angle of incidence between the deposition flux and the substrate normal. Atomic force microscopy is used to determine the root-mean-square value w of the surface roughness on the respective surfaces. From the scaling behavior of w , we find that while the roughness exponent α remains nearly unchanged at about 0.90, the growth exponent β changes from 0.49±0.04 to 0.26±0.01 as the deposition angle approaches grazing incidence. The values of the growth exponent β indicate that the film growth is influenced by both surface diffusion and shadowing effects, while the observed change from 0.49 to 0.26 can be attributed to differences in the relative importance of diffusion and shadowing with the deposition angle.

  7. Effect of external stress on phase diagrams and dielectric properties of epitaxial ferroelectric thin films grown on orthorhombic substrates

    Institute of Scientific and Technical Information of China (English)

    L(U) Ye-gang; DENG Shui-feng; GONG Lun-jun; YANG Jian-tao

    2006-01-01

    A Landau-Ginsburg-Devonshire(LD)-type thermodynamic theory was used to describe the effect of external stress on phase diagrams and dielectric properties of epitaxial ferroelectric thin films grown on orthorhombic substrates which induce nonequally biaxial misfit strains in the films plane. The "misfit strain-external stress" and "external stress-temperature" phase diagrams were constructed for single-domain BaTiO3(BT) and PbTiO3(PT) thin films. It is shown that the external stress may lead to the rotation of the spontaneous polarization and a gradual change of its magnitude, which may result in phase transition. Nonequally biaxial misfit strains dependence of the stability of polarization states may be governed by external stress. At room temperature,stress-induced ferroelectric/paraelectric phase transition which occurs in film on cubic substrate does not take place in the ferroelectric thin film grown on orthorhombic substrate. It is also shown that the nonequally misfit strains in the film plane may lead to the appearance of new phases which do not form in films grown on cubic substrates under external stress. The dependence of the dielectric response on the external stress is also studied. It is shown that the dielectric constants of single-domain PT and BT films are very sensitive to the external stress under the given anisotropic misfit strains-temperature conditions. It presents theoretical evidence that the external stress and anisotropic misfit strains can be employed for improving the thin films physical properties.

  8. Transport properties of as-grown MgB{sub 2} films using micro-bridge

    Energy Technology Data Exchange (ETDEWEB)

    Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Harada, Y. [Iwate Industry Promotion Center, 3-35-2 Iiokashinden, Morioka, Iwate 020-0852 (Japan)]. E-mail: yharada@luck.ocn.ne.jp; Goto, S. [Lightom, 95-2 Sugo, Takizawa 020-0173 (Japan); Shimizu, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Takahashi, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Kuroha, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Oba, T. [Faculty of Materials science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Seki, M. [Faculty of Materials science and Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Yoshizawa, M. [Iwate Industry Promotion Center, 3-35-2 Iiokashinden, Morioka, Iwate 020-0852 (Japan)

    2006-10-01

    The intermetallic superconductor magnesium diboride (MgB{sub 2}) is a promising candidate for use in superconducting electronic devices due to its high transition temperature (T{sub c}) and simple AlB{sub 2} type structure. Its application requires the development of a high-quality film fabrication process. We have previously reported the growth of MgB{sub 2} films deposited on MgO (1 0 0), SrTiO{sub 3} (1 0 0) and Al{sub 2}O{sub 3} (0 0 0 1) substrate using a co-evaporation method combined with a molecular beam epitaxy (MBE) apparatus. In this paper, we report on the details of the transport properties of these as-grown MgB{sub 2} films. These film's basal properties were investigated by XRD, RHEED, SQUID and the dc-4 probe method. Micro-bridges made using micro-processing methods such as photolithography and dry etching were used for transport measurements. All bridges were 10 {mu}m wide x 30 {mu}m long to allow estimation of their critical current density using the dc-4 probe method. We discuss the relationship between critical current densities and the substrates used.

  9. Thermal stability of MBE-grown epitaxial MoSe2 and WSe2 thin films

    Science.gov (United States)

    Chang, Young Jun; Choy, Byoung Ki; Phark, Soo-Hyon; Kim, Minu

    Layered transition metal dichalcogenides (TMDs) draw much attention, because of its unique optical properties and band structures depending on the layer thicknesses. However, MBE growth of epitaxial films demands information about thermal stability of stoichiometry and related electronic structure for high temperature range. We grow epitaxial MoSe2 and WSe2 ultrathin films by using molecular beam epitaxy (MBE). We characterize stoichiometry of films grown at various growth temperature by using various methods, XPS, EDX, and TOF-MEIS. We further test high temperature stability of electronic structure for those films by utilizing in-situ ellipsometry attached to UHV chamber. We discuss threshold temperatures up to 700~1000oC, at which electronic phases changes from semiconductor to metal due to selenium deficiency. This information can be useful for potential application of TMDs for fabrication of Van der Waals multilayers and related devices. This research was supported by Nano.Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning. (2009-0082580), NRF-2014R1A1A1002868.

  10. Growth-induced optical anisotropy of epitaxial garnet films grown on (110)-oriented substrates

    Science.gov (United States)

    Kitamura, K.; Iyi, N.; Kimura, S.; Chevrier, F.; Devignes, J. M.; Le Gall, H.

    1986-08-01

    Garnet films of nominal composition (Y,Nd)3Ga5O12, were grown on (110) 1°-off Gd3Ga5O12 substrates for investigation of their growth-induced optical anisotropy. Optical birefringence and directions of the electric vectors of polarized rays passing through the films were measured under a polarizing microscope using a Brace-Köhler compensator. The growth-induced anisotropy of these films optically exhibited orthorhombic characteristics with the X, Y, and Z optic elasticity axes coinciding with the [001], [110], and [1¯10] directions, respectively. The crystallographic data obtained by means of single-crystal diffractometry suggested that the cubic crystal system of the garnet film was distorted, though very slightly, to an orthorhombic one with a,b, and c axes that coincided, respectively, with the [1¯10],[001], and [110] of the original cubic cell. In addition, by annealing at 1150 °C, this distortion disappeared and the crystal system reverted to cubic.

  11. Investigation of AgInS{sub 2} thin films grown by coevaporation

    Energy Technology Data Exchange (ETDEWEB)

    Arredondo, C A; Gordillo, G [Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); J, Clavijo, E-mail: caarredondoo@unal.edu.c, E-mail: ggordillog@unal.edu.c [Departamento de Quimica, Universidad Nacional de Colombia, Bogota, Cr.30 N0 45-03 (Colombia)

    2009-05-01

    AgInS{sub 2} thin films were grown on soda-lime glass substrates by co-evaporation of the precursors in a two-step process. X-ray diffraction (XRD) measurements indicated that these compounds grow in different phases and with different crystalline structure depending upon the deposition conditions. However, through a parameter study, conditions were found to grow thin films containing only the AgInS{sub 2} phase with chalcopyrite type structure. In samples containing a mixture of several phases, the contribution in percentage terms of each phase to the whole compound was estimated with the help of the PowderCell simulation package. It was also found that the AgInS{sub 2} films present p-type conductivity, a high absorption coefficient (greater than 10{sub 4} cm{sub -1}) and an energy band gap Eg of about 1.95 eV, indicating that this compound has good properties to perform as absorbent layer in thin film tandem solar cells. The effect of the deposition conditions on the optical and morphological properties was also investigated through spectral transmitance and atomic force microscopy (AFM) measurements.

  12. Induced polarized state in intentionally grown oxygen deficient KTaO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.; Agostinho Moreira, J.; Almeida, A. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science of University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Perez de la Cruz, J. [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Vilarinho, P. M. [Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Tavares, P. B. [Centro de Quimica, Universidade de Tras-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real (Portugal)

    2013-07-21

    Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO{sub 2}/Ti/Pt substrates. Once they were structurally characterized, the effect of oxygen vacancies on their electric properties was addressed by measuring leakage currents, dielectric constant, electric polarization, and thermally stimulated depolarization currents. By using K{sub 2}O rich KTaO{sub 3} targets and specific deposition conditions, KTaO{sub 3-{delta}} oxygen deficient thin films with a K/Ta = 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO{sub 3-{delta}} thin films are under a compressive strain of 2.3% relative to KTaO{sub 3} crystals. Leakage current results reveal the presence of a conductive mechanism, following the Poole-Frenkel formalism. Furthermore, dielectric, polarization, and depolarization current measurements yield the existence of a polarized state below T{sub pol} {approx} 367 Degree-Sign C. A Cole-Cole dipolar relaxation was also ascertained apparently due to oxygen vacancies induced dipoles. After thermal annealing the films in an oxygen atmosphere at a temperature above T{sub pol}, the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.

  13. Scaling behavior of ZnPc thin films grown on CuI interlayers

    Science.gov (United States)

    Lee, Jinho; Jin, Sung-Il; Park, Chan Ryang; Yim, Sanggyu

    2015-01-01

    The growth behavior and consequent surface morphology evolution of zinc phthalocyanine (ZnPc) thin films deposited on a CuI interlayer were studied using atomic force microscopy and height difference correlation function (HDCF) analysis. The planar phthalocyanine thin films grown on non-interacting substrates have previously been reported to show anomalous scaling behavior such as large growth exponents, ß, sometimes larger than 0.5, and small anomaly values, ρ, typically smaller than 0.6. In contrast, ZnPc thin films on a CuI interlayer (CuI/ ZnPc) in this work showed conventional scaling behavior with a ß value of 0.26 ± 0.05 and a ρ value of 0.91. The HDCF analyses and x-ray diffraction results indicate that the expected interdigitated electron donor-acceptor interface was hardly formed for the CuI/ZnPc thin film system due to the lack of surface-parallel crystallites with high step edge barriers.

  14. Electronic properties of high-temperature superconducting thin films grown by pulsed laser deposition

    Science.gov (United States)

    Abrecht, M.; Ariosa, Daniel; Cloetta, D.; Margaritondo, Giorgio; Pavuna, Davor

    2002-11-01

    We use a pulsed laser deposition (PLD) setup to grow ultra-thin films of high temperature superconductors (HTSC) and transfer them in-situ into a photoemission chamber. Photoemission measurements on such films allow us to study non-cleavable materials, but can also give insights into aspects never measured before, like the influence of strain on the low energy electronic structure. Systematic studies of many different materials grown as films showed that Bi2Sr2CaCu2O8+x, Bi2Sr2Cu1O6+x, Bi2Sr2Ca2Cu3O10+x and La2-xSrxCuO4 films exhibit a conductor-like Fermi edge, but materials containing chains (such as YBa2Cu3O7-x) are prone to very rapid surface degradation, possibly related to critical oxygen loss at the surface. Among HTSC materials, La2-xSrxCuO4 is extremely interesting because of its rather simple structure and the fact that its critical temperature Tc can be enhanced by epitaxial strain. Here we present our first high resolution angular resolved photoemission spectroscopy (ARPES) results on 8 unit-cell thin La2-xSrxCuO4 films on SrLaAlO4 [001] substrates. Due to the lattice mismatch, such films are compressed in the copper oxygen planes and expanded in the c-axis direction. Results show a surprisingly modified Fermi surface compared to the one of non-strained samples.

  15. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

    Science.gov (United States)

    Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A.; Anthopoulos, Thomas D.

    2017-01-01

    Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In2O3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In2O3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications. PMID:28435867

  16. Atomic Layer Deposition (ALD) grown thin films for ultra-fine pitch pixel detectors

    Energy Technology Data Exchange (ETDEWEB)

    Härkönen, J. [Helsinki Institute of Physics, CMS Upgrade Project, Helsinki (Finland); Ott, J. [Helsinki Institute of Physics, CMS Upgrade Project, Helsinki (Finland); Laboratory of Radio Chemistry, University of Helsinki (Finland); Mäkelä, M. [Laboratory of Inorganic Chemistry, University of Helsinki (Finland); Arsenovich, T.; Gädda, A.; Peltola, T. [Helsinki Institute of Physics, CMS Upgrade Project, Helsinki (Finland); Tuovinen, E. [Helsinki Institute of Physics, CMS Upgrade Project, Helsinki (Finland); VTT Technical Research Centre of Finland, Microsystem and Nanoelectronics (Finland); Luukka, P.; Tuominen, E. [Helsinki Institute of Physics, CMS Upgrade Project, Helsinki (Finland); Junkes, A. [Institute for Experimental Physics, University of Hamburg (Germany); Niinistö, J.; Ritala, M. [Laboratory of Inorganic Chemistry, University of Helsinki (Finland)

    2016-09-21

    In this report we cover two special applications of Atomic Layer Deposition (ALD) thin films to solve these challenges of the very small size pixel detectors. First, we propose to passivate the p-type pixel detector with ALD grown Al{sub 2}O{sub 3} field insulator with a negative oxide charge instead of using the commonly adopted p-stop or p-spray technologies with SiO{sub 2}, and second, to use plasma-enhanced ALD grown titanium nitride (TiN) bias resistors instead of the punch through biasing structures. Surface passivation properties of Al{sub 2}O{sub 3} field insulator was studied by Photoconductive Decay (PCD) method and our results indicate that after appropriate annealing Al{sub 2}O{sub 3} provides equally low effective surface recombination velocity as thermally oxidized Si/SiO{sub 2} interface. Furthermore, with properly designed annealing steps, the TiN thin film resistors can be tuned to have up to several MΩ resistances with a few µm of physical size required in ultra-fine pitch pixel detectors.

  17. Atomic Layer Deposition (ALD) grown thin films for ultra-fine pitch pixel detectors

    Science.gov (United States)

    Härkönen, J.; Ott, J.; Mäkelä, M.; Arsenovich, T.; Gädda, A.; Peltola, T.; Tuovinen, E.; Luukka, P.; Tuominen, E.; Junkes, A.; Niinistö, J.; Ritala, M.

    2016-09-01

    In this report we cover two special applications of Atomic Layer Deposition (ALD) thin films to solve these challenges of the very small size pixel detectors. First, we propose to passivate the p-type pixel detector with ALD grown Al2O3 field insulator with a negative oxide charge instead of using the commonly adopted p-stop or p-spray technologies with SiO2, and second, to use plasma-enhanced ALD grown titanium nitride (TiN) bias resistors instead of the punch through biasing structures. Surface passivation properties of Al2O3 field insulator was studied by Photoconductive Decay (PCD) method and our results indicate that after appropriate annealing Al2O3 provides equally low effective surface recombination velocity as thermally oxidized Si/SiO2 interface. Furthermore, with properly designed annealing steps, the TiN thin film resistors can be tuned to have up to several MΩ resistances with a few μm of physical size required in ultra-fine pitch pixel detectors.

  18. Enhancement in as-grown CuInSe{sub 2} film microstructure by a three potential pulsed electrodeposition method

    Energy Technology Data Exchange (ETDEWEB)

    Palacios-Padros, A. [Department of Physical Chemistry, University of Barcelona (UB), Institute for Bioengineering of Catalonia (IBEC) Marti i Franques 1, 08028 Barcelona (Spain); Caballero-Briones, F.; Sanz, Fausto [Department of Physical Chemistry, University of Barcelona (UB), Institute for Bioengineering of Catalonia (IBEC) Marti i Franques 1, 08028 Barcelona (Spain); CIBER-BBN, Maria de Luna 11, 50018 Zaragoza (Spain)

    2010-08-15

    P-type copper indium diselenide (CuInSe{sub 2}) films have been prepared onto ITO substrates by an electrodeposition method, that sequentially applies potential pulses at the deposition potential of each element Cu, Se and In, and then step it back in cyclically to induce the solid state reaction between the elements. Two electrolyte concentrations as well as three different pulse durations were assessed. The resulting films were compared with those deposited at fixed electrode potentials. As-grown films are nanocrystalline and have an E{sub g} {proportional_to} 0.95 eV. Raman spectroscopy shows that Se and Cu-Se contents decrease while pulse duration increases and electrolyte concentration decreases. Cu-Se phases are even absent for films grown at the low electrolyte concentration. These results represent a great improvement in the film phase purity reducing the need of post-deposition treatments. (author)

  19. Effect of Annealing on the Optical Properties of GaN Films Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    M.Baseer Haider; M.F.Al-Kuhaili; S.M.A.Durrani; Imran Bakhtiari

    2013-01-01

    In the present study,gallium nitride thin films were grown by using pulsed laser deposition.After the growth samples were annealed at 400 and 600 ℃ in the nitrogen atmosphere.Surface morphology of the as-grown and annealed samples was observed by atomic force microscopy.Post-growth annealing results in an improved surface roughness of the films.Chemical analysis of the samples was performed by X-ray photoelectron spectroscopy.Stoichiometric gallium nitride thin films were obtained for the samples annealed at 600 ℃.Optical measurements of the samples were performed to measure the band gap and optical constants of the films.Effect of annealing on the band gap and optical constants of the films was studied.

  20. Dynamic scaling and optical properties of Zn(S, O,OH) thin film grown by chemical bath deposition

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi; Li Bo-Yan; Dang Xiang-Yu; Wu Li; Jin Jing; Li Feng-Yan; Ao Jian-Ping; Sun Yun

    2011-01-01

    The scaling behavior and optical properties of Zn(S,O and OH) thin films deposited on soda-lime glass substrates by chemical bath deposition method were studied by combined roughness measurements,scanning electron microscopy and optical properties measurement.From the scaling behaviour,the value of growth scaling exponent β,0.38±0.06,was determined.This value indicated that the Zn(S,O,OH) film growth in the heterogeneous process was influenced by the surface diffusion and shadowing effect.Results of the optical properties measurements disclosed that the transmittance of the film was in the region of 70%-88% and the optical properties of the film grown for 40 min were better than those grown under other conditions.The energy band gap of the film deposited with 40 min was around 3.63 eV.

  1. Influence of different carrier gases on the properties of ZnO films grown by MOCVD

    Directory of Open Access Journals (Sweden)

    Wang, Jinzhong

    2008-08-01

    Full Text Available ZnO films were grown on sapphire (001 substrate by atmospheric MOCVD using diethyl zinc and tertiary butanol precursors. The influence of different carrier gases (H2 and He on the properties was analyzed by their structural (XRD, microstructural (SEM and compositional (SIMS characterization. The intensity of the strongest diffraction peak from ZnO (002 plane was increased by about 2 orders of magnitude when He is used as carrier gas, indicating the significant enhancement in crystallinity. The surface of the samples grown using H2 and He carrier gases was composed of leaf-like and spherical grains respectively. Hydrogen [H] content in the film grown using H2 is higher than that using He, indicating that the [H] was influenced by the H2 carrier gas. Ultraviolet emission dominates the low temperature PL spectra. The emission from ZnO films grown using He show higher optical quality and more emission centers.

    Se depositaron películas de ZnO sobre sustratos de zafiro (001 utilizando dietil zinc y butanol terciario como precursores. La influencia de los diferentes gases portadores (H2 y He sobre las propiedades se estudió mediante la caracterización estructural (XRD, microestructural (SEM y composicional (SIMS. La intensidad del pico de difracción más importante del plano (002 del ZnO aumentó en dos órdenes de magnitud cuando se utiliza He como gas portador indicando un incremento significativo de la cristalinidad. La superficie de las muestras crecidas utilizando H2 y He está formada por granos en forma de hoja y de forma esférica respectivamente. El contenido en hidrógeno (H en la película es mayor cuando se utiliza H2 que cuando se utiliza He, indicando que la cantidad de hidrógeno está influenciada por el H2 del gas portador. La emisión ultravioleta domina el espectro PL de baja temperatura. La emisión de las películas de ZnO utilizando

  2. The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates.

    Science.gov (United States)

    Cholula-Díaz, Jorge L; Barzola-Quiquia, José; Videa, Marcelo; Yin, Chunhai; Esquinazi, Pablo

    2017-09-13

    Zinc oxide (ZnO) thin films were grown by pulsed layer deposition under an N2 atmosphere at low pressures on a- and r-plane sapphire substrates. Structural studies using X-ray diffraction confirmed that all films had a wurtzite phase. ZnO thin films on a- and r-plane sapphire have grown with orientations along the [0002] and [112[combining macron]0] directions, respectively. Room temperature photoluminescence measurements indicate that the presence of native point defects (interstitial zinc, oxygen vacancies, oxygen antisites and zinc vacancies) is more preponderant for ZnO thin films grown on the r-plane sapphire substrate than the sample grown on the a-plane sapphire substrate. Room temperature impedance spectroscopy measurements were performed in an alternating current frequency range from 40 to 10(5) Hz in the dark and under normal light. An unusual positive photoresistance effect is observed at frequencies above 100 kHz, which we suggest to be due to intrinsic defects present in the ZnO thin films. Furthermore, an analysis of the optical time response revealed that the film grown on the r-plane sapphire substrate responds faster (characteristic relaxation times for τ1, τ2 and τ3 of 0.05, 0.26 and 6.00 min, respectively) than the film grown on the a-plane sapphire substrate (characteristic relaxation times for τ1, τ2 and τ3 of 0.10, 0.73 and 4.02 min, respectively).

  3. Growth mechanism of single-crystalline NiO thin films grown by metal organic chemical vapor deposition

    Science.gov (United States)

    Roffi, Teuku Muhammad; Nozaki, Shinji; Uchida, Kazuo

    2016-10-01

    Nickel oxide (NiO) thin films were grown by atmospheric-pressure metal organic chemical vapor deposition (APMOCVD). Growth was carried out using various growth parameters, including the growth temperature, the input precursor (O2/Ni) ratio, and the type of substrate material. Effects of the growth parameters on the structural and electrical properties of the films were investigated. X-ray diffraction analysis revealed that the crystal structure and quality were strongly affected by the growth temperature and the type of substrate material. At an optimized growth temperature, single-crystalline NiO films were grown on MgO(100) and MgO(111) substrates in a cube-on-cube orientation relationship, while on an Al2O3(001) substrate, the film was grown in the NiO[111] direction. The use of MgO substrates successfully suppressed the formation of twin defects, which have been frequently reported in the growth of NiO. The difference in the formation of the twin defects on MgO and Al2O3 substrates was discussed. It was observed that the resistivity dependence on crystal quality was affected by the choice of substrate material. The effects of the precursor ratio on the transmittance and resistivity of the films were also investigated. Improved transparency in the visible wavelength region and higher conductivity were found in films grown with higher O2/Ni ratios.

  4. Electric field and temperature scaling of polarization reversal in silicon doped hafnium oxide ferroelectric thin films

    OpenAIRE

    Zhou, Dayu; Guan, Yan; Vopson, Melvin Marian; Xu, Jin; Liang, Hailong; Cao,Fei; Dong, Xianlin; Johannes, Johannes; Schenk, Tony; Schroeder, Uwe

    2015-01-01

    HfO2-based binary lead-free ferroelectrics show promising properties for non-volatile memory applications, providing that their polarization reversal behavior is fully understood. In this work, temperature-dependent polarization hysteresis measured over a wide applied field range has been investigated for Si-doped HfO2 ferroelectric thin films. Our study indicates that in the low and medium electric field regimes (E < twofold coercive field, 2Ec), the reversal process is dominated by the ther...

  5. Structural and optical characterization of ZrO2 thin films grown on silicon and quartz substrates

    Science.gov (United States)

    Hojabri, Alireza

    2016-09-01

    Zirconium oxide thin films were grown successfully by thermal annealing of zirconium thin films deposited on quartz and silicon substrates by direct current magnetron sputtering technique. The structural and optical properties in relation to thermal annealing times were investigated. The X-ray diffraction patterns revealed that structure of films changes from amorphous to crystalline by increase of annealing times in range 60-240 min. The composition of films was determined by Rutherford back scattering spectroscopy. Atomic force microscopy results exhibited that surface morphology and roughness of films depend on the annealing time. The refractive index of the films was calculated using Swanepoel's method. The optical band gap energy of annealed films decreased from 5.50 to 5.34 eV with increasing thermal annealing time.

  6. The structural state of epitaxial GaP films of different polarities grown on misoriented Si(001) substrates

    Science.gov (United States)

    Loshkarev, I. D.; Vasilenko, A. P.; Trukhanov, E. M.; Kolesnikov, A. V.; Putyato, M. A.; Esin, M. Yu.; Petrushkov, M. O.

    2017-02-01

    The structure of GaP films grown by molecular-beam epitaxy on vicinal Si(1113) substrates has been studied by X-ray diffraction. It is established that the crystalline lattice of a pseudomorphic film rotates about the axis toward increasing deviation from the singular orientation, while the subsequent relaxation leads to rotation in the opposite direction. This is valid for the films of both (001) and (001¯) polarities. Differences between the surface morphologies of relaxed and pseudomorphic GaP films are revealed.

  7. Control of native acceptor density in epitaxial Cu2O thin films grown by electrochemical deposition

    Science.gov (United States)

    Ashida, Atsushi; Sato, Shunsuke; Yoshimura, Takeshi; Fujimura, Norifumi

    2017-06-01

    Controlling the native carrier is essential for using Cu2O in devices such as solar cells. The origin of the native p-type carrier in Cu2O is thought to be copper vacancies (VCu). In this work, epitaxially grown Cu2O thin films were prepared by electrochemical deposition at a low temperature of 45 °C on a Pt (111) cathodic electrode. The sources of Cu and O for Cu2O were Cu2+ and OH- in the electrolyte and the ion concentrations were changed to control the stoichiometry of deposition and the density of VCu. The density of ionized acceptors (NA+) in the Cu2O films was evaluated by the C-V properties measured with Schottky electrodes. NA+ did not depend on [Cu2+], whereas NA+ increased with increasing [OH-] when [OH-] was larger than 10-3 mol/L (electrolyte pH >11) with [Cu2+] fixed at 10-1 mol/L. The ion concentration dependence of NA+ and the dependence of the total cathodic current density revealed that the generation of VCu was affected by a complex combination of the ion concentrations and film growth rate.

  8. Reproducibility and off-stoichiometry issues in nickelate thin films grown by pulsed laser deposition

    Science.gov (United States)

    Preziosi, Daniele; Sander, Anke; Barthélémy, Agnès; Bibes, Manuel

    2017-01-01

    Rare-earth nickelates are strongly correlated oxides displaying a metal-to-insulator transition at a temperature tunable by the rare-earth ionic radius. In PrNiO3 and NdNiO3, the transition is very sharp and shows an hysteretic behavior akin to a first-order transition. Both the temperature at which the transition occurs and the associated resistivity change are extremely sensitive to doping and therefore to off-stoichiometry issues that may arise during thin film growth. Here we report that strong deviations in the transport properties of NdNiO3 films can arise in films grown consecutively under nominally identical conditions by pulsed laser deposition; some samples show a well-developed transition with a resistivity change of up to five orders of magnitude while others are metallic down to low temperatures. Through a detailed analysis of in-situ X-ray photoelectron spectroscopy data, we relate this behavior to large levels of cationic off-stoichoimetry that also translate in changes in the Ni valence and bandwidth. Finally, we demonstrate that this lack of reproducibility can be remarkably alleviated by using single-phase NdNiO3 targets.

  9. Thin multilayer CdS/ZnS films grown by SILAR technique

    Science.gov (United States)

    Valkonen, Mika P.; Lindroos, Seppo; Kanniainen, Tapio; Leskelä, Markku; Tapper, Unto; Kauppinen, Esko

    1997-11-01

    Multilayer ZnS/CdS thin films were grown on glass, ITO-covered glass and (100)GaAs substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature and ambient pressure. The layers in multilayer thin film structures were nominally 1-6 nm thick and the amount of layers varied so that the total thickness of 100-120 nm was achieved. The films were polycrystalline according to X-ray diffraction analysis and scanning electron microscopy. The interfaces between the separate cadmium sulfide (CdS) and zinc sulfide (ZnS) layers were not sharp, but contained thin Cd xZn 1- xS solid solution layers. Annealing enhanced the mixing of the different layers and after 50 h at 300°C no separate CdS and ZnS X-ray reflections could be detected. About 20 nm thick layers could be detected as separate fields by scanning electron microscopy.

  10. STM study of the Ga thin films grown on Si(111) surface

    Science.gov (United States)

    Tao, Min-Long; Tu, Yu-Bing; Sun, Kai; Ye, Juan; Hao, Shao-Jie; Xiao, Hua-Fang; Wang, Ya-Li; Xie, Zheng-Bo; Wang, Jun-Zhong

    2017-09-01

    Structural evolution of Ga thin films grown on the Si(111)-√{ 3 } × √{ 3 } -Ga template have been investigated with a low-temperature scanning tunneling microscopy (STM). The first Ga layer exhibits a stripe structure along the base vectors of Si(111) lattices. Individual Ga dimers have been directly visualized from the high-resolution STM images of the first Ga layer. The second Ga layer reveals a pseudo 1×1 structure with respect to the Si(111). A new 5×5 phase has been found in the second Ga layer when annealing the sample to 120 ℃. Further annealing to 150 ℃ leads to the formation of 6.3×6.3 phase, which is more stable than the 5×5 phase. The existences of a variety of superstructures of Ga films demonstrates the delicate balance between the interactions of Si(111)-Ga and Ga-Ga. These results shed important light on the epitaxial growth mechanism of Ga films on semiconductor surfaces.

  11. Frictional Properties of UV illuminated ZnO Thin Films Grown by Pulsed Laser Deposition

    Science.gov (United States)

    Chiu, Hsiang-Chih; Chang, Huan-Pu; Lo, Fang-Yu; Yeh, Yu-Ting; Department of Physics, National Taiwan Normal University Collaboration

    Zinc Oxide (ZnO) nanostructures have potential applications in nano-electro-mechanical systems (NEMS) due to their unique physical properties. ZnO is also an excellent lubricant and hence a promising candidate for protective coatings in NEMS. By means of atomic force microscopy (AFM), we have investigated the frictional properties of ZnO thin films prepared by pulsed laser deposition technique. In addition, UV illumination is used to convert the surface wettability of ZnO thin films from being more hydrophobic to superhydrophilic via the photo-catalyst effect. We found that the frictional properties of the UV illuminated, superhydrophilic ZnO surface are strongly dependent on the environment humidity. While for hydrophobic ZnO, no such dependence is found. The observed frictional behaviors can be explained by the interplay between the surface roughness, environmental humidity and the presence of nanoscale capillary condensation forming between surface asperities at the tip-ZnO contact. Our results might find applications in future ZnO related NEMS. Frictional Properties of UV illuminated ZnO Thin Films Grown by Pulsed Laser Deposition.

  12. Electrical and mechanical stability of aluminum-doped ZnO films grown on flexible substrates by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Luka, G., E-mail: gluka@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Witkowski, B.S.; Wachnicki, L.; Jakiela, R. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Virt, I.S. [University of Rzeszow, Rzeszow (Poland); Drohobych Ivan Franko State Pedagogical University, Drohobych (Ukraine); Andrzejczuk, M.; Lewandowska, M. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Godlewski, M. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Department of Mathematics and Natural Sciences, College of Science, Cardinal Stefan Wyszynski University, Warsaw (Poland)

    2014-08-01

    Highlights: • Transparent and conductive ZnO:Al films were grown by atomic layer deposition. • The films were grown on flexible substrates at low growth temperatures (110–140 °C). • So-obtained films have low resistivities, of the order of 10{sup −3} Ω cm. • Bending tests indicated a critical bending radius of ≈1.2 cm. • Possible sources of the film resistivity changes upon bending are proposed. - Abstract: Aluminum-doped zinc oxide (AZO) films were grown on polyethylene terephthalate (PET) substrates by atomic layer deposition (ALD) at low deposition temperatures (110–140 °C). The films have low resistivities, ∼10{sup −3} Ω cm, and high transparency (∼90%) in the visible range. Bending tests indicated a critical bending radius of ≈1.2 cm, below which the resistivity changes became irreversible. The films deposited on PET with additional buffer layer are more stable upon bending and temperature changes.

  13. Ultrafast carrier dynamics and the role of grain boundaries in polycrystalline silicon thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Titova, Lyubov V.; Cocker, Tyler L.; Xu, Sijia; Baribeau, Jean-Marc; Wu, Xiaohua; Lockwood, David J.; Hegmann, Frank A.

    2016-10-01

    We have used time-resolved terahertz spectroscopy to study microscopic photoconductivity and ultrafast photoexcited carrier dynamics in thin, pure, non-hydrogenated silicon films grown by molecular beam epitaxy on quartz substrates at temperatures ranging from 335 °C to 572 °C. By controlling the growth temperature, thin silicon films ranging from completely amorphous to polycrystalline with minimal amorphous phase can be achieved. Film morphology, in turn, determines its photoconductive properties: in the amorphous phase, carriers are trapped in bandtail states on sub-picosecond time scales, while the carriers excited in crystalline grains remain free for tens of picoseconds. We also find that in polycrystalline silicon the photoexcited carrier mobility is carrier-density-dependent, with higher carrier densities mitigating the effects of grain boundaries on inter-grain transport. In a film grown at the highest temperature of 572 °C, the morphology changes along the growth direction from polycrystalline with needles of single crystals in the bulk of the film to small crystallites interspersed with amorphous silicon at the top of the film. Depth profiling using different excitation wavelengths shows corresponding differences in the photoconductivity: the photoexcited carrier lifetime and mobility are higher in the first 100-150 nm from the substrate, suggesting that thinner, low-temperature grown polycrystalline silicon films are preferable for photovoltaic applications.

  14. Effect of silane flow rate on structural, electrical and optical properties of silicon thin films grown by VHF PECVD technique

    Energy Technology Data Exchange (ETDEWEB)

    Gope, Jhuma [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Kumar, Sushil, E-mail: skumar@nplindia.org [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sudhakar, S.; Rauthan, C.M.S. [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Srivastava, P.C. [Department of Physics, Banaras Hindu University, Varanasi 221005 (India)

    2013-08-15

    Hydrogenated silicon thin films deposited by VHF PECVD process for various silane flow rates have been investigated. The silane flow rate was varied from 5 sccm to 30 sccm, maintaining all other parameters constant. The electrical, structural and optical properties of these films were systematically studied as a function of silane flow rate. These films were characterized by Raman spectroscopy, Scanning Electron Microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and UV–visible (UV–Vis) spectroscopy. Different crystalline volume fraction (22%–60%) and band gap (∼1.58 eV–∼1.96 eV) were achieved for silicon thin films by varying the silane concentration. A transition from amorphous to nanocrystalline silicon has been confirmed by Raman and FTIR analysis. The film grown at this transition region shows the high conductivity in the order of 10{sup −4} Ω{sup −1} cm{sup −1}. - Highlights: • Silicon films grown using VHF PECVD at various F{sub silane} (silane flow rate). • Amorphous to nanocrystalline silicon transition at F{sub silane} ∼5 sccm–10 sccm. • Deposition rate increases with the increase of F{sub silane}. • Powder formation occurred beyond 20 sccm of F{sub silane}. • Film grown at 20 sccm shows max. crystalline fraction ∼60% with E{sub g} ∼1.58 eV.

  15. The investigation of spray pyrolysis grown CdS thin films doped with flourine atoms

    Energy Technology Data Exchange (ETDEWEB)

    Yılmaz, Salih, E-mail: slh_yilmaz@yahoo.com.tr

    2015-12-01

    Highlights: • Undoped and F-doped CdS thin films were produced. • XRD data showed deterioration with the increase of F-doping. • SEM images indicated a grain growth after F-doping. • RTPL data exhibited an enhancement in the spectrum for F-doped CdS samples. • The best electrical and optical properties were obtained for 2 at.% F-doped CdS. - Abstract: Undoped and F-doped CdS thin films were succesfully grown on the glass substrates by the spray prolysis method. X-ray diffraction results showed that all the samples had hexagonal wurtzite structure with the (1 0 1) preferred orientation. It was found from scanning electron microscopy that an increase in the grain size was observed after F-doping. The band gap value of CdS thin films increased from 2.38 eV to 2.42 eV with the increase of F concentration from 0 to 6 at.%. The intensity of room temperature photoluminescence spectrum of undoped CdS thin films enhanced with the increment of F-doping amount that is related to the increase of point defects formed by the flourine atoms. Electrical measurements showed that the carrier concentration increased from 1.93 × 10{sup 12} cm{sup −3} to 7.62 × 10{sup 12} cm{sup −3} when CdS thin films were doped with 2 at.% F. However, further increase in F amount up to 6 at.% caused a decrease in the carrier concentration. On the other hand, resistivity value first decreased from 1.26 × 10{sup 5} Ω cm to 8.54 × 10{sup 4} Ω cm with the increase of F-doping up to 2 at.% and then increased to 1.65 × 10{sup 5} Ω cm for 6 at.% F-doping. It can be concluded that 2 at.% F-doped CdS thin films exhibited the best electrical and optical properties, which is suitable for the application of thin film solar cells.

  16. Synthesis of as-grown superconducting MgB_2 thin films by molecular beam epitaxy in UHV conditions

    OpenAIRE

    Harada, Y.; Udsuka, M.; Nakanishi, Y.; Yoshizawa, M.

    2004-01-01

    As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001), MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method with novel co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c determined by resistivity measurement w...

  17. Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates

    Science.gov (United States)

    2013-02-01

    like HEMTs . A nanolayer of AlGaN over GaN provides extra 2DEG charge density because of the piezoelectric effect of the AlGaN layer. The higher...Control of Defects in Aluminum Gallium Nitride ((Al) GaN ) Films on Grown Aluminum Nitride (AlN) Substrates by Iskander G. Batyrev, Chi-Chin Wu...Aluminum Gallium Nitride ((Al) GaN ) Films on Grown Aluminum Nitride (AlN) Substrates Iskander G. Batyrev and N. Scott Weingarten Weapons and

  18. Ionization potentials of transparent conductive indium tin oxide films covered with a single layer of fluorine-doped tin oxide nanoparticles grown by spray pyrolysis deposition

    OpenAIRE

    2005-01-01

    Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7 nm in average size show an ionization potential of 5.01 eV, as compared ...

  19. Fabricating superconducting interfaces between artificially grown LaAlO3 and SrTiO3 thin films

    Directory of Open Access Journals (Sweden)

    Danfeng Li

    2014-01-01

    Full Text Available Realization of a fully metallic two-dimensional electron gas (2DEG at the interface between artificially grown LaAlO3 and SrTiO3 thin films has been an exciting challenge. Here we present for the first time the successful realization of a superconducting 2DEG at interfaces between artificially grown LaAlO3 and SrTiO3 thin films. Our results highlight the importance of two factors—the growth temperature and the SrTiO3 termination. We use local friction force microscopy and transport measurements to determine that in normal growth conditions the absence of a robust metallic state at low temperature in the artificially grown LaAlO3/SrTiO3 interface is due to the nanoscale SrO segregation occurring on the SrTiO3 film surface during the growth and the associated defects in the SrTiO3 film. By adopting an extremely high SrTiO3 growth temperature, we demonstrate a way to realize metallic, down to the lowest temperature, and superconducting 2DEG at interfaces between LaAlO3 layers and artificially grown SrTiO3 thin films. This study paves the way to the realization of functional LaAlO3/SrTiO3 superlattices and/or artificial LaAlO3/SrTiO3 interfaces on other substrates.

  20. Low Microwave Surface Resistance in NdBa2Cu3O7-d Films Grown by Molecular Beam Epitaxy

    OpenAIRE

    2004-01-01

    We report the growth of NdBa2Cu3O7-d films on (100) MgO substrate by Molecular Beam Epitaxy (MBE). Large area NdBa2Cu3O7-d films with homogeneous superconducting properties were grown by precise control of stoichiometry and the optimisation of growth parameters. The stoichiometric ratio of Nd:Ba:Cu close to 1:2:3 yields films with TC of 94 K and JC values above 3.5 MA/cm2 at 77 K on bare MgO substrate. The NdBa2Cu3O7-d films grown under optimised conditions had excellent in-plane texture and ...

  1. Effects of Annealing Temperature on Properties of ZnO Thin Films Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    ZHUANG Hui-zhao; XUE Shou-bin; XUE Cheng-shan; HU Li-jun; LI Bao-li; ZHANG Shi-ying

    2007-01-01

    ZnO thin films are deposited on n-Si(111) substrates by pulsed laser deposition(PLD) system.Then the samples are annealed at different temperatures in air ambient and their properties are investigated particularly as a function of annealing temperature.The microstructure,morphology and optical properties of the as-grown ZnO films are studied by X-ray diffraction(XRD),atomic force microscope(AFM),Fourier transform infrared spectroscopy(FTIR) and photoluminescence(PL) spectra.The results show that the as-grown ZnO films have a hexagonal wurtzite structure with a preferred c-axis orientation.Moreover,the diameters of the ZnO crystallites become larger and the crystal quality of the ZnO films is improved with the increase of annealing temperature.

  2. Electrical and optical properties of VO2 thin films grown on various sapphire substrates by using RF sputtering deposition

    Science.gov (United States)

    Jung, Dae Ho; So, Hyeon Seob; Ko, Kun Hee; Park, Jun Woo; Lee, Hosun; Nguyen, Trang Thi Thu; Yoon, Seokhyun

    2016-12-01

    VO2 thin films were grown on a-, c-, m-, and r-plane sapphire and SiO2/Si substrates under identical conditions by using RF sputtering deposition from a VO2 target. The structural and the morphological properties of all VO2 films were investigated. The grain sizes of the VO2 films varied between 268 nm and 355 nm depending on the substrate's orientation. The electrical and the optical properties of all VO2 thin films were examined in detail. The metal-insulator transition temperature (TMI) varied with the substrate's orientation. The (200)/(bar 211 )-oriented VO2 films on the a-plane sapphire showed the lowest TMI of about 329.3 K (56.3 °C) while the (020)/(002)-VO2 films on the c-plane sapphire displayed the highest TMI of about 339.6 K (66.6 °C). The VO2 films showed reversible changes in the resistivity as large as 1.19 × 105 and a hysteresis of 2 K upon traversing the transition temperature. The variations observed in the TMI with respect to the substrate's orientation were due to changes in the lattice strain and the grain size distribution. Raman spectroscopy showed that metal (rutile) - insulator (monoclinic) transitions occurred via the M2 phase for VO2 films on the c-plane substrate rather than the direct M1 to rutile transition. The shifts in the phonon frequencies of the VO2 film grown on various sapphire substrates were explained in terms of the strain along the V-V atomic bond direction (cR). Our work shows a possible correlation between the transition parameters ( e.g., TMI, sharpness, and hysteresis width) and the width ( σ) of the grain size distribution. It also shows a possible correlation between the TMI and the resistivities at the insulating and the metallic phases for VO2 films grown on various sapphire substrates.

  3. Magnetotransport in an aluminum thin film on a GaAs substrate grown by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Lin Sheng-Di

    2011-01-01

    Full Text Available Abstract Magnetotransport measurements are performed on an aluminum thin film grown on a GaAs substrate. A crossover from electron- to hole-dominant transport can be inferred from both longitudinal resistivity and Hall resistivity with increasing the perpendicular magnetic field B. Also, phenomena of localization effects can be seen at low B. By analyzing the zero-field resistivity as a function of temperature T, we show the importance of surface scattering in such a nanoscale film.

  4. Structural and optical characterizations of InPBi thin films grown by molecular beam epitaxy.

    Science.gov (United States)

    Gu, Yi; Wang, Kai; Zhou, Haifei; Li, Yaoyao; Cao, Chunfang; Zhang, Liyao; Zhang, Yonggang; Gong, Qian; Wang, Shumin

    2014-01-13

    InPBi thin films have been grown on InP by gas source molecular beam epitaxy. A maximum Bi composition of 2.4% is determined by Rutherford backscattering spectrometry. X-ray diffraction measurements show good structural quality for Bi composition up to 1.4% and a partially relaxed structure for higher Bi contents. The bandgap was measured by optical absorption, and the bandgap reduction caused by the Bi incorporation was estimated to be about 56 meV/Bi%. Strong and broad photoluminescence signals were observed at room temperature for samples with xBi < 2.4%. The PL peak position varies from 1.4 to 1.9 μm, far below the measured InPBi bandgap.

  5. Thermal activation of nitrogen acceptors in ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Dangbegnon, J.K.; Talla, K.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth (South Africa)

    2010-06-15

    Nitrogen doping in ZnO is inhibited by spontaneous formation of compensating defects. Perfect control of the nitrogen doping concentration is required, since a high concentration of nitrogen could induce the formation of donor defects involving nitrogen. In this work, the effect of post-growth annealing in oxygen ambient on ZnO thin films grown by Metalorganic Chemical Vapor Deposition, using NO as both oxidant and nitrogen dopant, is studied. After annealing at 700 C and above, low-temperature photoluminescence shows the appearance of a transition at {proportional_to}3.23 eV which is interpreted as pair emission involving a nitrogen acceptor. A second transition at {proportional_to}3.15 eV is also discussed. This work suggests annealing as a potential means for p-type doping using nitrogen (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Interface between metallic film from Fe-Ni-C system and HPHT as-grown diamond single crystal

    Institute of Scientific and Technical Information of China (English)

    许斌; 李木森; 尹龙卫; 刘玉先; 崔建军; 宫建红

    2003-01-01

    Microstructures of surface layer (near diamond) of the metallic film from Fe-Ni-C system are composed of (Fe,Ni)3C, (Fe,Ni)23C6 and γ-(Fe,Ni), from which it can be assumed that graphite isn't directly catalyzed into diamond through the film and there exists a transition phase (Fe,Ni)3C that can decompose into diamond structure. AFM morphologies on the film/diamond interface are traces preserved after carbon groups moving from the film to diamond. The morphologies on the as-grown diamond are similar to those on corresponding films, being spherical on (100) face and sawtooth-like steps on (111) face. Diamond growth rates and temperature gradients in boundary layer of the molten film at HPHT result in morphology differences.

  7. Properties of MgB{sub 2} films grown at various temperatures by hybrid physical-chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ke; Veldhorst, Menno; Li, Qi; Xi, X X [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Lee, Che-Hui; Lamborn, Daniel R; DeFrain, Raymond; Redwing, Joan M [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

    2008-09-15

    A hybrid physical-chemical vapour deposition (HPCVD) system consisting of separately controlled Mg-source heater and substrate heater is used to grow MgB{sub 2} thin films and thick films at various temperatures. We are able to grow superconducting MgB{sub 2} thin films at temperatures as low as 350 deg. C with a T{sub c0} of 35.5 K. MgB{sub 2} films up to 4 {mu}m in thickness grown at 550 deg. C have J{sub c} over 10{sup 6} A cm{sup -2} at 5 K and zero applied field. The low deposition temperature of MgB{sub 2} films is desirable for all-MgB{sub 2} tunnel junctions and MgB{sub 2} thick films are important for applications in coated conductors.

  8. Zinc sulfide and terbium-doped zinc sulfide films grown by traveling wave reactor atomic layer epitaxy

    CERN Document Server

    Yun, S J; Nam, K S

    1998-01-01

    Zinc sulfide (ZnS) and terbium-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (ALE). In the present work, ZnCl sub 2 , H sub 2 S, and tris (2,2,6,6-tetramethyl-3,5-heptandionato) terbium (Tb(tmhd) sub 3) were used as the precursors. The dependence of crystallinity and Cl content of ZnS films was investigated on the growth temperature. ZnS and ZnS:Tb films grown at temperatures ranging from 400 to 500 .deg. C showed a hexagonal-2H crystalline structure. The crystallinity of ZnS film was greatly enhanced as the temperature increased. At growth temperatures higher than 450.deg.C, the films showed preferred orientation with mainly (002) diffraction peak. The Cl content decreased from approximately 9 to 1 at.% with the increase in growth temperature from 400 to 500 .deg. C. The segregation of Cl near the surface region and the incorporation of O from Tb(tmhd) sub 3 during ALE process were also observed using Auger electron spectroscopy. The ALE-grown ZnS and ZnS:Tb films re...

  9. Characteristics of Fluorine-doped tin oxide thin films grown by Streaming process for Electrodeless Electrochemical Deposition

    Science.gov (United States)

    Yusuf, Gbadebo; Khalilzadeh-Rezaie, Farnood; Cleary, Justin W.; Oladeji, Isaiah O.; Suu, Koukou; Schoenfeld, Winston V.; Peale, Robert E.; Awodugba, Ayodeji O.

    2015-04-01

    This work investigated the characteristics of SnO2: F films grown by Streaming Process for Electrodeless Electrochemical Deposition (SPEED). Stannic chloride (SnCl4) and ammonium fluoride (NH4 F) was dissolved in a mixture of deionized water and organic solvents. The preheated substrate temperature was varied between 450 and 530° C. High quality SnO2: F films were grown at all the substrate temperatures studied. The typical film thickness was 250 nm. XRD shows that the grown films are polycrystalline SnO2 with a tetragonal crystal structure. The average optical transmission of the films was around 93% throughout the wavelength of 400 to 1000 nm. The lowest electrical resistivity achieved was 6 x 10-4 Ω cm. The Hall measurements showed that the film is an n-type semiconductor, with the highest carrier mobility of 8.3 cm2/V.s, and concentration of 1 x 1021 cm-3. The direct band gap was determined to be 4 eV from the transmittance spectrum.

  10. Hydrogen influence on the electrical and optical properties of ZnO thin films grown under different atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Lorite, I., E-mail: lorite@physik.uni-leipzig; Wasik, J.; Michalsky, T.; Schmidt-Grund, R.; Esquinazi, P.

    2014-04-01

    In this work we studied the changes of the electrical and optical properties after hydrogen plasma treatment of polycrystalline ZnO thin films grown under different atmosphere conditions. The obtained results show that the gas used during the growth process plays an important role in the way hydrogen is incorporated in the films. The hydrogen doping can produce radiative and non-radiative defects that reduce the UV emission in ZnO films grown in oxygen atmosphere but it passivates defects created when the films are grown in nitrogen atmosphere. Impedance spectroscopy measurements show that these effects are related to regions where hydrogen is mostly located, either at the grain cores or boundaries. We discuss how hydrogen strongly influences the initial semiconducting behavior of the ZnO thin films. - Highlights: • Effectiveness of hydrogen treatment depends on the thin film growth conditions. • There is no detection of secondary phases after treatment by IS. • Hydrogen incorporation changes optical and electrical ZnO properties.

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

    Science.gov (United States)

    Li, Wei; Varlamov, Sergey; Xue, Chaowei

    2014-09-01

    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, Voc and Jsc than the one on the seed layer without RTA treatment.

  12. Field effect transistor with HfO2/Parylene-C bilayer hybrid gate insulator

    Science.gov (United States)

    Kumar, Neeraj; Kito, Ai; Inoue, Isao

    2015-03-01

    We have investigated the electric field control of the carrier density and the mobility at the surface of SrTiO3, a well known transition-metal oxide, in a field effect transistor (FET) geometry. We have used a Parylene-C (8 nm)/HfO2 (20 nm) double-layer gate insulator (GI), which can be a potential candidate for a solid state GI for the future Mott FETs. So far, only examples of the Mott FET used liquid electrolyte or ferroelectric oxides for the GI. However, possible electrochemical reaction at the interface causes damage to the surface of the Mott insulator. Thus, an alternative GI has been highly desired. We observed that even an ultra thin Parylene-C layer is effective for keeping the channel surface clean and free from oxygen vacancies. The 8 nm Parylene-C film has a relatively low resistance and consequentially its capacitance does not dominate the total capacitance of the Parylene-C/HfO2 GI. The breakdown gate voltage at 300 K is usually more than 10 V (~ 3.4 MV/cm). At gate voltage of 3 V the carrier density measured by the Hall effect is about 3 ×1013 cm-2, competent to cause the Mott transition. Moreover, the field effect mobility reaches in the range of 10 cm2/Vs indicating the Parylene-C passivated surface is actually very clean.

  13. Synthesis and characterization of hafnium oxide films for thermo and photoluminescence applications.

    Science.gov (United States)

    Mendoza, J Guzmán; Frutis, M A Aguilar; Flores, G Alarcón; Hipólito, M García; Maciel Cerda, A; Azorín Nieto, J; Montalvo, T Rivera; Falcony, C

    2010-01-01

    Hafnium oxide (HfO(2)) films were deposited by the ultrasonic spray pyrolysis process. The films were synthesized from hafnium chloride as raw material in deionized water as solvent and were deposited on corning glass substrates at temperatures from 300 to 600 degrees C. For substrate temperatures lower than 400 degrees C the deposited films were amorphous, while for substrate temperatures higher than 450 degrees C, the monoclinic phase of HfO(2) appeared. Scanning electron microscopy showed that the film's surface resulted rough with semi-spherical promontories. The films showed a chemical composition close to HfO(2), with an Hf/O ratio of about 0.5. UV radiation was used in order to achieve the thermoluminescent characterization of the films; the 240 nm wavelength induced the best response. In addition, preliminary photoluminescence spectra, as a function of the deposition temperatures, are shown. Copyright 2009 Elsevier Ltd. All rights reserved.

  14. Effects of annealing on electrical performance of multilayer MoS2 transistors with atomic layer deposited HfO2 gate dielectric

    Science.gov (United States)

    Wen, Ming; Xu, Jingping; Liu, Lu; Lai, Pui-To; Tang, Wing-Man

    2016-09-01

    Atomic layer deposited HfO2 annealed in different ambients (N2, O2, and NH3) is used to replace SiO2 as a gate dielectric for fabricating back-gated multilayer MoS2 transistors. Excellent electrical properties such as a mobility of 15.1 cm2/(V·s), an on/off ratio exceeding 107, and a hysteresis of 0.133 V are achieved for samples annealed in NH3 at 400 °C for 10 min. This is caused by the NH3 annealing passivation effects that reduce defective states in the HfO2 dielectric and the interface. The capacitance equivalent thickness is only 7.85 nm, which is quite small for a back-gated MoS2 transistor and is conducive to the scaling down of the device.

  15. Identification of the ferroelectric switching process and dopant-dependent switching properties in orthorhombic HfO2: A first principles insight

    Science.gov (United States)

    Clima, S.; Wouters, D. J.; Adelmann, C.; Schenk, T.; Schroeder, U.; Jurczak, M.; Pourtois, G.

    2014-03-01

    The origin of the ferroelectric polarization switching in orthorhombic HfO2 has been investigated by first principles calculations. The phenomenon can be regarded as being the coordinated displacement of four O ions in the orthorhombic unit cell, which can lead to a saturated polarization as high as 53 μC/cm2. We show the correlation between the computed polarization reversal barrier and the experimental coercive fields.

  16. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    S. S. Kushvaha

    2014-02-01

    Full Text Available We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm thick GaN epi-layer on sapphire (0001 substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 108 cm−2 at 750 °C than that of the low temperature grown sample (1.1 × 109 cm−2 at 730 °C. A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  17. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kushvaha, S. S., E-mail: kushvahas@nplindia.org; Pal, P.; Shukla, A. K.; Joshi, Amish G.; Gupta, Govind; Kumar, M.; Singh, S.; Gupta, Bipin K.; Haranath, D. [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)

    2014-02-15

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm thick GaN epi-layer on sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 10{sup 8} cm{sup −2} at 750 °C) than that of the low temperature grown sample (1.1 × 10{sup 9} cm{sup −2} at 730 °C). A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  18. Nonequilibrium critical behavior of magnetic thin films grown in a temperature gradient

    Science.gov (United States)

    Candia, Julián; Albano, Ezequiel V.

    2012-08-01

    We investigate the irreversible growth of (2 + 1)-dimensional magnetic thin films under the influence of a transverse temperature gradient, which is maintained by thermal baths across a direction perpendicular to the direction of growth. Therefore, different longitudinal layers grow at different temperatures between T1 and T2, where {T}_{1}\\lt {T}_{{c}}^{{hom}}\\lt {T}_{2} and {T}_{{c}}^{{hom}}=0.6 9(1) is the critical temperature of films grown in homogeneous thermal baths. We find a far-from-equilibrium continuous order-disorder phase transition driven by the thermal bath gradient. We characterize this gradient-induced critical behavior by means of standard finite-size scaling procedures, which lead to the critical temperature Tc = 0.84(2) and a new universality class consistent with the set of critical exponents ν = 3/2, γ = 5/2, and β = 1/4. In order to gain further insight into the effects of the temperature gradient, we also develop a bond model that captures the magnetic film’s growth dynamics. Our findings show that the interplay of geometry and thermal bath asymmetries leads to growth bond flux asymmetries and the onset of transverse ordering effects that explain qualitatively the shift observed in the critical temperature. The relevance of these mechanisms is further confirmed by a finite-size scaling analysis of the interface width, which shows that the growing sites of the system define a self-affine interface.

  19. Low-temperature, vapor-liquid-solid, laterally grown silicon films using alloyed catalysts

    Science.gov (United States)

    LeBoeuf, Jerome L.; Brodusch, Nicolas; Gauvin, Raynald; Quitoriano, Nathaniel J.

    2014-12-01

    Using amorphous oxide templates known as micro-crucibles which confine a vapor-liquid-solid catalyst to a specific geometry, two-dimensional silicon thin-films of a single orientation have been grown laterally over an amorphous substrate and defects within crystals have been necked out. The vapor-liquid-solid catalysts consisted nominally of 99% gold with 1% titanium, chromium, or aluminum, and each alloy affected the processing of micro-crucibles and growth within them significantly. It was found that chromium additions inhibited the catalytic effect of the gold catalysts, titanium changed the morphology of the catalyst during processing and aluminum stabilized a potential third phase in the gold-silicon system upon cooling. Two mechanisms for growing undesired nanowires were identified both of which hindered the VLS film growth, fast silane cracking rates and poor gold etching, which left gold nanoparticles near the gold-vapor interface. To reduce the silane cracking rates, growth was done at a lower temperature while an engineered heat and deposition profile helped to reduce NWs caused by the second mechanism. Through experimenting with catalyst compositions, the fundamental mechanisms which produce concentration gradients across the gold-silicon alloy within a given micro-crucible have been proposed. Using the postulated mechanisms, micro-crucibles were designed which promote high-quality, single crystal growth of semiconductors.

  20. Electrical properties of GaAsN film grown by chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, K. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan)], E-mail: sd05501@toyota-ti.ac.jp; Suzuki, H.; Saito, K.; Ohshita, Y.; Kojima, N.; Yamaguchi, M. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan)

    2007-12-15

    The local vibrational modes (LVMs) observed by Fourier transform infrared (FTIR) spectroscopy in GaAsN films grown by chemical beam epitaxy (CBE) was studied, and the influence of the nitrogen-hydrogen bond (N-H) concentration on the hole concentration was investigated. The absorption peak around 936 cm{sup -1} is suggested to be the second harmonic mode of the substitutional N, N{sub As}, LVM around 469 cm{sup -1}. The absorption peak around 960 cm{sup -1} is suggested to be the wagging mode of the N-H, where the stretch mode is observed around 3098 cm{sup -1}. The hole concentration linearly increases with increasing N-H concentration, and the slope increases with increasing growth temperature. It indicates that the hole concentration in GaAsN film is determined by both the number of the N-H and unknown defect, such as impurities, vacancies, and interstitials. This defect concentration increases with increasing growth temperature, suggesting that it is determined by Arrhenius type reaction.

  1. Effect of residual stress on the microstructure of GaN epitaxial films grown by pulsed laser deposition

    Science.gov (United States)

    Wang, Haiyan; Wang, Wenliang; Yang, Weijia; Zhu, Yunnong; Lin, Zhiting; Li, Guoqiang

    2016-04-01

    The stress-free GaN epitaxial films have been directly grown by pulsed laser deposition (PLD) at 850 °C, and the effect of different stress on the microstructure of as-grown GaN epitaxial films has been explored in detail. The as-grown stress-free GaN epitaxial films exhibit very smooth surface without any particles and grains, which is confirmed by the smallest surface root-mean-square roughness of 2.3 nm measured by atomic force microscopy. In addition, they also have relatively high crystalline quality, which is proved by the small full-width at half maximum values of GaN(0002) and GaN (10 1 bar 2) X-ray rocking curves as 0.27° and 0.68°, respectively. However, when the growth temperature is lower or higher than 850 °C, internal or thermal stress would be increased in as-grown GaN epitaxial films. To release the larger stress, a great number of dislocations are generated. Many irregular particulates, hexagonal GaN gains and pits are therefore produced on the films surface, and the crystalline quality is greatly reduced consequently. This work has demonstrated the direct growth of stress-free GaN epitaxial films with excellent surface morphology and high crystalline quality by PLD, and presented a comprehensive study on the origins and the effect of stress in GaN layer. It is instructional to achieve high-quality nitride films by PLD, and shows great potential and broad prospect for the further development of high-performance GaN-based devices.

  2. Structural characteristics of single crystalline GaN films grown on (111) diamond with AlN buffer

    DEFF Research Database (Denmark)

    Pécz, Béla; Tóth, Lajos; Barna, Árpád;

    2013-01-01

    Hexagonal GaN films with the [0001] direction parallel to the surface normal were grown on (111) oriented single crystalline diamond substrates by plasma-assisted molecular beam epitaxy. Pre-treatments of the diamond surface with the nitrogen plasma beam, prior the nucleation of a thin AlN layer,...

  3. An investigation of structural properties of GaN films grown on patterned sapphire substrates by MOVPE

    Science.gov (United States)

    Törmä, P. T.; Ali, M.; Svensk, O.; Sintonen, S.; Kostamo, P.; Suihkonen, S.; Sopanen, M.; Lipsanen, H.; Odnoblyudov, M. A.; Bougrov, V. E.

    2009-12-01

    GaN films were fabricated by metal organic vapor phase epitaxy (MOVPE) on patterned sapphire substrates (PSSs) with either direct or inverse type patterned structures. Both of these two types of PSSs had their own unique GaN growth process which depart from the standard growth on the planar c-plane. GaN films on PSSs showed decreased threading dislocation (TD) density. However, differences between the crystal quality of the GaN films grown on PSSs were observed. It was also found out with one of the pattern type that the TD density varied laterally and followed the periodicity of the pattern on the sapphire surface.

  4. Laser MBE-grown yttrium iron garnet films on GaN: characterization of the crystal structure and magnetic properties

    Science.gov (United States)

    Kaveev, A. K.; Bursian, V. E.; Gastev, S. V.; Krichevtsov, B. B.; Suturin, S. M.; Volkov, M. P.; Sokolov, N. S.

    2016-07-01

    Yttrium iron garnet (YIG) films were grown on GaN substrates using the laser molecular beam epitaxy method. X-ray diffraction data showed polycrystalline YIG layers without additional structural modifications. The magnetic properties of the YIG films were studied at room temperature with the aid of a vibration sample magnetometer, the magneto-optical Kerr effect and ferromagnetic resonance methods. ‘Easy-plane’-type magnetic anisotropy was found in the films. The gyromagnetic ratio and 4 πMS value were calculated.

  5. Effect of acetylene flow rate on morphology and structure of carbon nanotube thick films grown by thermal chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    CAO Zhangyi; SUN Zhuo; GUO Pingsheng; CHEN Yiwei

    2007-01-01

    Carbon nanotube (CNT) films were grown on nickel foil substrates by thermal chemical vapor deposition (CVD) with acetylene and hydrogen as the precursors. The morphology and structure of CNTs depending on the acetylene flow rate were characterized by a scanning electron microscope (SEM),a transmission electron microscope (TEM) and a Raman spectrometer,respectively.The effect of acetylene flow rate on the morphology and structure of CNT films was investigated.By increasing the acetylene flow rate from 10 to 90 sccm (standard cubic centimeter perminute),the yield and the diameter of CNTs increase.Also, the defects and amorphous phase in CNT films increase with increasing acetylene flow rate.

  6. Effect of standing-wave field distribution on femosecond laser-induced damage of HfO2/SiO2 mirror coating

    Institute of Scientific and Technical Information of China (English)

    Shunli Chen; Yuan'an Zhao; Hongbo He; Manda Shao

    2011-01-01

    Single-pulse and multi-pulse damage behaviors of "standard" (with A/4 stack structure) and "modified" (with reduced standing-wave field) HfO2/SiO2 mirror coatings are investigated using a commercial 50-fs, 800-nm Tksapphire laser system. Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings. Meanwhile, the single-pulse laser-induced damage threshold of the "standard" mirror is improved by about 14% while suppressing the normalized electric field intensity at the outmost interface of the HfO2 and SiO2 layers by 37%. To discuss the damage mechanism, a theoretical model based on photoionization, avalanche ionization, and decays of electrons is adopted to simulate the evolution curves of the conduction-band electron density during pulse duration.%@@ Single-pulse and multi-pulse damage behaviors of "standard"(with λ/4 stack structure) and "modified"(with reduced standing-wave field) HfO2/SiO2 mirror coatings are investigated using a commercial 50-fs,800-nm Thsapphire laser system.以Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings .

  7. Electrical Characterization of Metal-Insulator-Metal Capacitors with Atomic-Layer-Deposited HfO2 Dielectrics for Radio Frequency Integrated Circuit Application

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Jian; HUANG Yue; DING Shi-Jin; ZHANG Wei; LIU Ran

    2007-01-01

    Metal-insulator-metal (MIM) capacitors with atomic-layer-deposited HfO2 dielectric and TaN electrodes are investigated for rf integrated circuit applications. For 12nm HfO2, the fabricated capacitor exhibits a high capacitance density of 15.5fF/μm2 at 100kHz, a small leakage current density of 6.4 × 10-9 A/cm2 at 1.8 V and 125℃, a breakdown electric field of 2.6 MV/cm as well as voltage coefficients of capacitance (VCCs) of 2110ppm/V2 and -824 ppm/V at 100kHz. Further, it is deduced that the conduction mechanism in the high field range is dominated by the Poole-Frenkel emission, and the conduction mechanism in the low field range is possibly related to trap-assisted tunnelling. Finally, comparison of various HfO2 MIM capacitors is present,suggesting that the present MIM capacitor is a promising candidate for future rf integrated circuit application.

  8. Texture mechanisms and microstructure of biaxial thin films grown by oblique angle deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shetty, A.R.; Karimi, A. [Institut de Physique de la Matiere Condensee (IPMC), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)

    2012-08-15

    In order to understand the texture formation mechanism in thin films grown under oblique angle deposition (OAD), TiAlN films were deposited at room temperature (RT) under various incident angles. We show that both in-plane and out-of-plane crystallographic orientations respond strongly to the deposition angle. For {alpha} = 0 , the pole figures show a (111) and (200) mixed out-of-plane orientation with random in-plane alignment. In contrast, under OAD, inclined textures are observed with the (111) direction moving toward the incident flux direction and the (200) moving away, showing substantial in-plane alignment. This observation suggests that TiAlN crystals prefer to grow with the (200) direction perpendicular to the substrate while maintaining the minimization of the surface free energy by maximizing the (111) surface area toward the incident flux. The in-plane texture, which is randomly oriented at normal incidence, gives rise to two preferred orientations under oblique angles - one along the direction of flux and other away from the deposition source. The biaxial texture results from a competition among texture mechanism related to surface mobilities of adatoms, geometrical and directional effects. The surface and cross-section of the films were observed by scanning electron microscopy (SEM). OAD films develop a kind of smooth tiles of a roof structure, with no faceted crystallites. The columns of these films were tilted toward the direction of incident flux. The dependence of (111) texture tilt angle and column angle {beta} on the incidence flux angle {alpha} is evaluated using four well-known models. Transmission electron microscopy (TEM) study reveals a voided, intercolumnar structure with oblique growth toward the flux direction. The selected area diffraction pattern (SAED) pattern supports the pole figure observations. Measurements of the nanoindentation test were performed in order to discuss the change of mechanical properties as a function of incident

  9. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D., E-mail: l_chandrakant@yahoo.com

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z{sub 1}) and nanograins by SILAR (Z{sub 2}). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10{sup 2} Ω cm) is lower than that of SILAR deposited films (10{sup 5} Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method.

  10. 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.

  11. Morphology and Optical Properties of Zinc Oxide Films Grown on Metal Coated Glass Substrates by Aqueous Chemical Growth

    Science.gov (United States)

    Bakar, M. A.; Hamid, M. A. A.; Jalar, A.; Shamsudin, R.

    2013-04-01

    Zinc oxide films were deposited on three different metal coated substrates (gold, nickel and platinum) by aqueous chemical growth method. This paper discusses the effect of metal coated substrates on the morphology and optical properties of grown ZnO films. X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and UV-visible spectroscopy (UV-vis) were employed to characterize the samples. All the as-deposited ZnO films exhibit crystalline hexagonal wurzite structure. The crystallite size of the ZnO films were in the range of 29 to 32 nm. FESEM micrographs revealed hexagonal rod, oval-like and flower-like ZnO structures formed on all metal coated substrates. The Pt coated film contains higher density hexagonal rod as compared to others metal coated substrate. Most probably the Pt lattice parameter is the nearest to ZnO compared to nickel and gold. The optical band gap energy, Eg of ZnO films were estimated to be 3.30 eV which is near to bulk Eg, 3.37 eV. This indicates that the ZnO grown by aqueous chemical growth is able to produce similar quality properties to other conventional method either films or bulk size.

  12. N-doped ZnO films grown from hybrid target by the pulsed laser deposition technique

    Science.gov (United States)

    Martín-Tovar, E. A.; Chan y Díaz, E.; Acosta, M.; Castro-Rodríguez, R.; Iribarren, A.

    2016-10-01

    ZnO thin films were grown by the pulsed laser deposition technique on glass substrate using a hybrid target composed of ZnO powder embedded into a poly(ethyl cyanoacrylate) matrix. The resulting thin film presented ZnO wurtzite structure with very low stress and diffractogram very similar to that of the powder pattern. From comparing with ZnO thin films grown from traditional sintered target, it is suggested that the use of this hybrid target with a soft matrix led to ejection of ZnO clusters that conveniently disposed and adhered to substrate and previous deposited layers. Chemical measurements showed the presence of Zn-N bonds, besides Zn-O ones. Optical absorption profile confirmed the presence of low-polymerized zinc oxynitride molecular subunits, besides ZnO.

  13. UV/vis range photodetectors based on thin film ALD grown ZnO/Si heterojunction diodes

    Science.gov (United States)

    Alkis, Sabri; Tekcan, Burak; Nayfeh, Ammar; Kemal Okyay, Ali

    2013-10-01

    We present ultraviolet-visible (UV/vis) range photodetectors (PDs) based on thin film ZnO (n)/Si (p) heterojunction diodes. ZnO films are grown by the atomic layer deposition (ALD) technique at growth temperatures of 80, 150, 200 and 250 ° C. The fabricated ZnO (n)/Si (p) photodetectors (ZnO-Si-PDs) show good electrical rectification characteristics with ON/OFF ratios reaching up to 103. Under UV (350 nm wavelength) and visible (475 nm wavelength) light illumination, the ZnO-Si-PDs give photoresponsivity values of 30-37 mA W-1 and 74-80 mA W-1 at 0.5 V reverse bias, respectively. Photoluminescence (PL) spectra of ALD grown ZnO thin films are used to support the results.

  14. Nanomechanical properties of SiC films grown from C{sub 60} precursors using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Morse, K. [Colorado School of Mines, Golden, CO (United States); Balooch, M.; Hamza, A.V.; Belak, J. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

    The mechanical properties of SiC films grown via C{sub 60} precursors were determined using atomic force microscopy (AFM). Conventional silicon nitride and modified diamond cantilever AFM tips were employed to determine the film hardness, friction coefficient, and elastic modulus. The hardness is found to be between 26 and 40 GPa by nanoindentation of the film with the diamond tip. The friction coefficient for the silicon nitride tip on the SiC film is about one third that for silicon nitride sliding on a silicon substrate. By combining nanoindentation and AFM measurements an elastic modulus of {approximately}300 GPa is estimated for these SiC films. In order to better understand the atomic scale mechanisms that determine the hardness and friction of SiC, we simulated the molecular dynamics of a diamond indenting a crystalline SiC substrate.

  15. Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Quesada, Adrián [Instituto de Cerámica y Vidrio, CSIC, Madrid E-28049 (Spain); Martín-García, Laura; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Prieto, Pilar; Muñoz-Martín, Ángel [Universidad Autónoma de Madrid, E-28049 (Spain); Aballe, Lucía [Alba Synchrotron Light Facility, CELLS, Barcelona (Spain); Marco, José F. [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain)

    2015-12-30

    Highlights: • Infrared pulsed deposition is used to grow single crystal mixed magnetite-cobalt ferrite films. • Distinct topography with two mound types on the surface of the film. • Suggested origin of segregation into two phases is oxygen deficiency during growth. • Mössbauer is required to quantify the two components. - Abstract: We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO{sub 3} by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.

  16. LiCoO{sub 2} thin films grown by pulsed laser deposition on low cost substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ginley, D.S.; Perkins, J.D.; McGraw, J.M.; Parilla, P.A.

    1998-07-01

    The authors report on the use of pulsed laser deposition (PLD) to grow thin films of LiCoO{sub 2} on a number of low cost substrates including SnO{sub 2} coated Upilex, stainless steel and SnO{sub 2} coated glass. Highly textured (001) films grown on CVD deposited SnO{sub 2} films on 7059 glass, were obtained at 200 to 500 mTorr O{sub 2} and a temperature of 500 C. Similar texture was not obtained on the stainless or Upilex however dense films from crystalline to amorphous were obtained. The films were characterized by x-ray diffraction and Raman spectroscopy.

  17. ALD grown nanostructured ZnO thin films: Effect of substrate temperature on thickness and energy band gap

    Directory of Open Access Journals (Sweden)

    Javed Iqbal

    2016-10-01

    Full Text Available Nanostructured ZnO thin films with high transparency have been grown on glass substrate by atomic layer deposition at various temperatures ranging from 100 °C to 300 °C. Efforts have been made to observe the effect of substrate temperature on the thickness of the deposited thin films and its consequences on the energy band gap. A remarkably high growth rate of 0.56 nm per cycle at a substrate temperature of 200 °C for ZnO thin films have been achieved. This is the maximum growth rate for ALD deposited ZnO thin films ever reported so far to the best of our knowledge. The studies of field emission scanning electron microscopy and X-ray diffractometry patterns confirm the deposition of uniform and high quality nanosturtured ZnO thin films which have a polycrystalline nature with preferential orientation along (100 plane. The thickness of the films deposited at different substrate temperatures was measured by ellipsometry and surface profiling system while the UV–visible and photoluminescence spectroscopy studies have been used to evaluate the optical properties of the respective thin films. It has been observed that the thickness of the thin film depends on the substrate temperatures which ultimately affect the optical and structural parameters of the thin films.

  18. 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.

  19. Characterization of oxynitride dielectric films grown in NO/O{sub 2} mixtures by rapid thermal oxynitridation

    Energy Technology Data Exchange (ETDEWEB)

    EVERIST,SARAH C.; MEISENHEIMER,TIMOTHY L.; NELSON,GERALD C.; SMITH,PAUL M.

    2000-02-29

    Ultra-thin oxynitride films were grown on Si by direct rapid thermal processing (RTP) oxynitridation in NO/O{sub 2} ambients with NO concentrations from 5% to 50%. During oxynitridation, nitrogen accumulated at the Si/dielectric interface and the average concentration of in N through the resulting films ranged from 0.3 to 3.0 atomic percent. The average concentration of N in the films increased with increasing NO in the ambient gas, but decreased with longer RTP times. The maximum N concentration remained relatively constant for all RTP times and a given NO/O{sub 2} ambient. Re-oxidation following oxynitridation altered L the N profile and improved the electrical characteristics, with an optimal NO/O{sub 2} mixture in the range of 10% to 25% NO. Re-oxidation by RTP improves the electrical characteristics with respect to the films that were not re-oxidized and produces only slight changes in the N distribution or maximum concentration. The electrical results also indicate that oxynitride films are superior to comparably grown oxide films.

  20. Annealing Effect on the Structural and Optical Properties of Sputter-Grown Bismuth Titanium Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    José E. Alfonso

    2014-04-01

    Full Text Available The aim of this work is to assess the evolution of the structural and optical properties of BixTiyOz films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain size, low defect density and high refractive index similar to that of single crystals. Films with thickness in the range of 220–250 nm have been successfully grown. After annealing treatment at 600 °C the films show excellent transparency and full crystallization. It is shown that to achieve larger crystallite sizes, up to 17 nm, it is better to carry the annealing under dry air than under oxygen atmosphere, probably because the nucleation rate is reduced. The refractive index of the films is similar under both atmospheres and it is very high (n =2.5 at 589 nm. However it is still slightly lower than that of the single crystal value due to the polycrystalline morphology of the thin films.

  1. Investigation of bonded hydrogen defects in nanocrystalline diamond films grown with nitrogen/methane/hydrogen plasma at high power conditions

    Science.gov (United States)

    Tang, C. J.; Hou, Haihong; Fernandes, A. J. S.; Jiang, X. F.; Pinto, J. L.; Ye, H.

    2017-02-01

    In this work, we investigate the influence of some growth parameters such as high microwave power ranging from 3.0 to 4.0 kW and N2 additive on the incorporation of bonded hydrogen defects in nanocrystalline diamond (NCD) films grown through a small amount of pure N2 addition into conventional 4% CH4/H2 plasma using a 5 kW microwave plasma CVD system. Incorporation form and content of hydrogen point defects in the NCD films produced with pure N2 addition was analyzed by employing Fourier-transform infrared (FTIR) spectroscopy for the first time. A large amount of hydrogen related defects was detected in all the produced NCD films with N2 additive ranging from 29 to 87 μm thick with grain size from 47 nm to 31 nm. Furthermore, a specific new H related sharp absorption peak appears in all the NCD films grown with pure N2/CH4/H2 plasma at high powers and becomes stronger at powers higher than 3.0 kW and is even stronger than the 2920 cm-1 peak, which is commonly found in CVD diamond films. Based on these experimental findings, the role of high power and pure nitrogen addition on the growth of NCD films including hydrogen defect formation is analyzed and discussed.

  2. Thickness dependence of critical current density in MgB{sub 2} films fabricated by ex situ annealing of CVD-grown B films in Mg vapor

    Energy Technology Data Exchange (ETDEWEB)

    Hanna, Mina; Salama, Kamel [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Wang, Shufang; Xi, X X [Department of Physics, Pennsylvania State University, University Park, PA 16801 (United States); Redwing, Joan M [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16801 (United States)], E-mail: ksalama@uh.edu

    2009-01-15

    A study was performed to examine the J{sub c} behavior as a function of thickness in MgB{sub 2} films fabricated by ex situ annealing at 840 deg. C of boron films, grown by chemical vapor deposition, in Mg vapor. The film thicknesses range between 300 nm and 10 {mu}m. The values of J{sub c} range from 1.2 x 10{sup 7} A cm{sup -2} for 300 nm to 1.9 x 10{sup 5} A cm{sup -2} for 10 {mu}m film thicknesses at 20 K and self-field. The study shows that the critical current density (J{sub c}) in MgB{sub 2} films decreases with increasing film thickness, similar to that observed in YBCO-coated conductors. Moreover, our study shows that critical current (I{sub c}) reaches its maximum value of 728 A cm{sup -1} width at {approx}1 {mu}m thick MgB{sub 2} films at 20 K and self-field, which is, interestingly, the same thickness of pulsed-laser-deposited YBCO-coated conductors at which I{sub c} reaches its maximum value. The high J{sub c} values carried by our films show that the ex situ fabrication method can produce high quality MgB{sub 2} films at low processing temperatures, which is promising for RF cavity applications and coated-conductor wires and tapes.

  3. Influence of substrate on structural, morphological and optical properties of ZnO films grown by SILAR method

    Indian Academy of Sciences (India)

    F N Jiménez-García; C L Londoño-Calderón; D G Espinosa-Arbeláez; A Del Real; M E Rodríguez-García

    2014-10-01

    ZnO films were obtained by successive ionic layer adsorption and reaction (SILAR) method from four different substrates: glass microslides, corning glass, quartz and silicon with and without oxide layer. For films deposition, a precursor solution of ZnSO4 was used, complexed with ammonium hydroxide. Prior to the film deposition, wettability of the substrates was analysed using a CCD camera. It was found that the Si without the oxide layer substrate shows hydrophobic behaviour, which makes the films less adherent and not uniform, while in the other substrates, the behaviour was optimal for the growing process. ZnO films grown on glass microslides, corning glass, quartz and Si with oxide layer were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Vis techniques. According to the XRD patterns, the films were polycrystalline, with hexagonal wurtzite structure and the patterns mentioned showed significant differences in crystallite sizes, microstrain and texture coefficient with respect to the employed substrates. The morphology of the ZnO films constituted by rice-like and flower-like structures shows differences in form and size depending on the substrate. The UV–Vis spectroscopy results show that the substrate did not influence the band gap energy value obtained from films.

  4. Graphene films grown on sapphire substrates via solid source molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Tang Jun; Kang Chao-Yang; Li Li-Min; Liu Zhong-Liang; Yan Wen-Sheng; Wei Shi-Qiang; Xu Peng-Shou

    2012-01-01

    A method for growing graphene on a sapphire substrate by depositing an SiC buffer layer and then annealing at high temperature in solid source molecular beam epitaxy(SSMBE)equipment was presented.The structural and electronic properties of the samples were characterized by reflection high energy diffraction(RHEED),X-ray diffractionφ scans,Raman spectroscopy,and near edge X-ray absorption fine structure(NEXAFS)spectroscopy.The results of the RHEED and φ scan,as well as the Raman spectra,showed that an epitaxial hexagonal α-SiC layer was grown on the sapphire substrate.The results of the Raman and NEXAFS spectra revealed that the graphene films with the AB Bernal stacking structure were formed on the sapphire substrate after annealing.The layer number of the graphene was between four and five,and the thickness of the unreacted SiC layer was about 1-1.5 mm.

  5. Superconducting YBa sub 2 Cu sub 3 O sub 7 thin films grown in-situ by ion beam CO-deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kellett, B.K.; James, J.H.; Gauzzi, A.; Dwir, B.; Pavuna, D. (Inst. of Micro and Optoelectronics, Dept. of Physics, Federal Inst. of Tech., Lausanne (Switzerland))

    1989-12-01

    Superconducting YBCO thin films have been grown in-situ by three ion beam co-deposition sputtering. Both metal and oxide targets of Cu and Y and BaF{sub 2} and BaCO{sub 3} targets have been investigated. Film composition was determined by RBS and AES analysis. Films grown using BaF{sub 2} show fluorine contamination, whereas the carbon concentration in films grown using BaCO{sub 3} is beneath the Auger detection limit. Superconducting films have been grown on SrTiO{sub 3} (T{sub co}=78K) and on Si with SiO{sub 2} or Y{sub 2}O{sub 3} buffer layers (T{sub co}=35K). (orig.).

  6. Transferring MBE-grown topological insulator films to arbitrary substrates and metal-insulator transition via Dirac gap.

    Science.gov (United States)

    Bansal, Namrata; Cho, Myung Rae; Brahlek, Matthew; Koirala, Nikesh; Horibe, Yoichi; Chen, Jing; Wu, Weida; Park, Yun Daniel; Oh, Seongshik

    2014-03-12

    Mechanical exfoliation of bulk crystals has been widely used to obtain thin topological insulator (TI) flakes for device fabrication. However, such a process produces only microsized flakes that are highly irregular in shape and thickness. In this work, we developed a process to transfer the entire area of TI Bi2Se3 thin films grown epitaxially on Al2O3 and SiO2 to arbitrary substrates, maintaining their pristine morphology and crystallinity. Transport measurements show that these transferred films have lower carrier concentrations and comparable or higher mobilities than before the transfer. Furthermore, using this process we demonstrated a clear metal-insulator transition in an ultrathin Bi2Se3 film by gate-tuning its Fermi level into the hybridization gap formed at the Dirac point. The ability to transfer large area TI films to any substrate will facilitate fabrication of TI heterostructure devices, which will help explore exotic phenomena such as Majorana fermions and topological magnetoelectricity.

  7. Epitaxial Properties of Co-Doped ZnO Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    CAO Qiang; DENG Jiang-Xia; LIU Guo-Lei; CHEN Yan-Xue; YAN Shi-Shen

    2007-01-01

    High quality Co-doped ZnO thin films are grown on single crystalline Al2O3(0001) and ZnO(0001) substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450 ℃. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction (RHEED) and ex-situ high resolution x-ray diffraction (HRXRD). The epitaxial thin films are single crystal at film thickness smaller than 500nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co2+ substituting Zn2+ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures TC above room temperature.

  8. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    Directory of Open Access Journals (Sweden)

    Prashanta Dhoj Adhikari

    2014-01-01

    Full Text Available We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G. Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

  9. Etch Pits and Threading Dislocations in GaN Films Grown by Metal-Organic Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    陆敏; 常昕; 黎子兰; 杨志坚; 张国义; 章蓓

    2003-01-01

    High quality epitaxial GaN films on (0001) sapphire substrates were grown by a commercial metal-organic chemical vapour deposition system. The, etch pits and threading dislocations in GaN films is studied by a scanning electron microscope (SEM) and a transmission-electron microscope (TEM). The SEM images of GaN films, etched in mixed acid solution (H3PO4:H2SO4 = 1: 3) and molten KOH exhibit notably different, etching pit densities of 5 × 108/cm2 and 4 × 107/cm2, respectively, which probably indicate that more kinds of, etching pits were revealed when, etched in mixed acid solution (H3PO4:H2SO4 = 1: 3). Cross section TEM of GaN films with different g vectors showed the portions of different threading dislocations. Theoretical calculation indicates that the lattice and thermal expansion coefficient mismatch may be the main origins of pure edge threading dislocations.

  10. Effects of sapphire substrates surface treatment on the ZnO thin films grown by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yinzhen [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: agwyz@yahoo.com.cn; Chu Benli [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)

    2008-06-01

    The surface treatment effects of sapphire substrate on the ZnO thin films grown by magnetron sputtering were studied. The sapphire substrates properties have been investigated by means of atomic force microscopy (AFM) and X-ray diffraction rocking curves (XRCs). The results show that sapphire substrate surfaces have the best quality by CMP with subsequent chemical etching. The surface treatment effects of sapphire substrate on the ZnO thin films were examined by X-ray diffraction (XRD) and photoluminescence (PL) measurements. Results show that the intensity of (0 0 2) diffraction peak of ZnO thin films on sapphire substrates treated by CMP with subsequent chemical etching was strongest, FWHM of (0 0 2) diffraction peak is the narrowest and the intensity of UV peak of PL spectrum is strongest, indicating surface treatment on sapphire substrate preparation may improve ZnO thin films crystal quality and photoluminescent property.

  11. Low-damping sub-10-nm thin films of lutetium iron garnet grown by molecular-beam epitaxy

    Science.gov (United States)

    Jermain, C. L.; Paik, H.; Aradhya, S. V.; Buhrman, R. A.; Schlom, D. G.; Ralph, D. C.

    2016-11-01

    We analyze the structural and magnetic characteristics of (111)-oriented lutetium iron garnet (Lu3Fe5O12) films grown by molecular-beam epitaxy, for films as thin as 2.8 nm. Thickness-dependent measurements of the in- and out-of-plane ferromagnetic resonance allow us to quantify the effects of two-magnon scattering, along with the surface anisotropy and the saturation magnetization. We achieve effective damping coefficients of 11.1 (9 )×10-4 for 5.3 nm films and 32 (3 )×10-4 for 2.8 nm films, among the lowest values reported to date for any insulating ferrimagnetic sample of comparable thickness.

  12. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  13. Characterization of Al2O3 Thin Films on GaAs Substrate Grown by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    LU Hong-Liang; LI Yan-Bo; XU Min; DING Shi-Jin; SUN Liang; ZHANG Wei; WANG Li-Kang

    2006-01-01

    @@ Al2O3 thin films are grown by atomic layer deposition on GaAs substrates at 300℃. The structural properties of the Al2O3 thin film and the Al2O3/GaAs interface are characterized using x-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM), and x-ray photoelectron spectroscopy (XPS). The XRD results show that the as-deposited Al2O3 film is amorphous. For 30 atomic layer deposition growth cycles, the thicknesses of the Al2O3 thin film and the interface layer from the HRTEM are 3.3nm and 0.5nm, respectively.XPS analyses reveal that the Al2O3/GaAs interface is almost free from As2O3.

  14. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Science.gov (United States)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U.

    2016-12-01

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between S b 2 S 3 and I n and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40-60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 1017 cm-3 and 1000 cm2 V-1 s-1, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  15. Structural, morphological and optical characterizations of ZnO:Al thin films grown on silicon substrates by pulsed laser deposition

    Science.gov (United States)

    Alyamani, A.; Sayari, A.; Albadri, A.; Albrithen, H.; El Mir, L.

    2016-09-01

    The pulsed laser deposition (PLD) technique is used to grow Al-doped ZnO (AZO) thin films at 500 ° C on silicon substrates under vacuum or oxygen gas background from ablating AZO nanoparticle targets synthesized via the sol-gel process. The structural, morphological and optical properties were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and spectroscopic ellipsometry (SE) techniques. XRD and TEM images show that AZO powder has a wurtzite-type structure and is composed of small prismatic-like shape nanoparticles with an average size of 30nm. The structural properties of the AZO films grown under oxygen show no significant changes compared to those of the film grown under vacuum. However, the optical properties show a dependence on the growth conditions of the AZO films. Highly c -axis-oriented AZO thin films were obtained with grain size ˜ 15 nm. The stress in the AZO films is tensile as measured from the c -parameter. The dielectric function, the refractive index and the extinction coefficient as a function of the photon energy for the AZO films were determined by using spectroscopic ellipsometry measurements in the photon energy region from 1 to 6eV. The band gap energy was observed to slightly decrease in the presence of the O2 gas background and this may be attributed to the stress. The surface and volume energy loss functions are calculated and exhibit different behaviors in the energy range 1-6eV. Refractive indices of 1.9-2.1 in the visible region were obtained for the AZO films. Also, the electronic carrier concentration appears to be related to the presence of O2 during the growth process.

  16. Effects of growth temperature on the properties of atomic layer deposition grown ZrO2 films

    Science.gov (United States)

    Scarel, G.; Ferrari, S.; Spiga, S.; Wiemer, C.; Tallarida, G.; Fanciulli, M.

    2003-07-01

    Zirconium dioxide films are grown in 200 atomic layer deposition cycles. Zirconium tetrachloride (ZrCl4) and water (H2O) are used as precursors. A relatively high dielectric constant (κ=22), wide band gap, and conduction band offset (5.8 and 1.4 eV, respectively) indicate that zirconium dioxide is a most promising substitute for silicon dioxide as a dielectric gate in complementary metal-oxide-semiconductor devices. However, crystallization and chlorine ions in the films might affect their electrical properties. These ions are produced during atomic layer deposition in which the ZrCl4 precursor reacts with the growth surface. It is desirable to tune the composition, morphology, and structural properties in order to improve their benefit on the electrical ones. To address this issue it is necessary to properly choose the growth parameters. This work focuses on the effects of the growth temperature Tg. ZrO2 films are grown at different substrate temperatures: 160, 200, 250, and 350 °C. Relevant modification of the film structure with a change in substrate temperature during growth is expected because the density of reactive sites [mainly Si+1-(OH)-1 bonds] decreases with an increase in temperature [Y. B. Kim et al., Electrochem. Solid-State Lett. 3, 346 (2000)]. The amorphous film component, for example, that develops at Si+1-(OH)-1 sites on the starting growth surface, is expected to decrease with an increase in growth temperature. The size and consequences of film property modifications with the growth temperature are investigated in this work using x-ray diffraction and reflectivity, and atomic force microscopy. Time of flight-secondary ion mass spectrometry is used to study contaminant species in the films. From capacitance-voltage (CV) and current-voltage (IV) measurements, respectively, the dielectric constant κZrO2 and the leakage current are studied as a function of the film growth temperature.

  17. High Stability Electron Field Emitters Synthesized via the Combination of Carbon Nanotubes and N₂-Plasma Grown Ultrananocrystalline Diamond Films.

    Science.gov (United States)

    Chang, Ting-Hsun; Hsieh, Ping-Yen; Kunuku, Srinivasu; Lou, Shiu-Cheng; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan; Tai, Nyan-Hwa

    2015-12-16

    An electron field emitter with superior electron field emission (EFE) properties and improved lifetime stability is being demonstrated via the combination of carbon nanotubes and the CH4/N2 plasma grown ultrananocrystalline diamond (N-UNCD) films. The resistance of the carbon nanotubes to plasma ion bombardment is improved by the formation of carbon nanocones on the side walls of the carbon nanotubes, thus forming strengthened carbon nanotubes (s-CNTs). The N-UNCD films can thus be grown on s-CNTs, forming N-UNCD/s-CNTs carbon nanocomposite materials. The N-UNCD/s-CNTs films possess good conductivity of σ = 237 S/cm and marvelous EFE properties, such as low turn-on field of (E0) = 3.58 V/μm with large EFE current density of (J(e)) = 1.86 mA/cm(2) at an applied field of 6.0 V/μm. Moreover, the EFE emitters can be operated under 0.19 mA/cm(2) for more than 350 min without showing any sign of degradation. Such a superior EFE property along with high robustness characteristic of these combination of materials are not attainable with neither N-UNCD films nor s-CNTs films alone. Transmission electron microscopic investigations indicated that the N-UNCD films contain needle-like diamond grains encased in a few layers of nanographitic phase, which enhanced markedly the transport of electrons in the N-UNCD films. Moreover, the needle-like diamond grains were nucleated from the s-CNTs without the necessity of forming the interlayer that facilitate the transport of electrons crossing the diamond-to-Si interface. Both these factors contributed to the enhanced EFE behavior of the N-UNCD/s-CNTs films.

  18. Luminescence properties of lanthanide and ytterbium lanthanide titanate thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Per-Anders, E-mail: p.a.hansen@kjemi.uio.no; Fjellvåg, Helmer; Nilsen, Ola [Department of Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, Sem Sælandsvei 26, 0371 Oslo (Norway); Finstad, Terje G. [Department of Physics, Centre for Materials Science and Nanotechnology, University of Oslo, Sem Sælandsvei 24, 0371 Oslo (Norway)

    2016-01-15

    Lanthanide based luminescent materials are highly suitable as down conversion materials in combination with a UV-absorbing host material. The authors have used TiO{sub 2} as the UV-absorbing host material and investigated the energy transfer between TiO{sub 2} and 11 different lanthanide ions, Ln{sup 3+} (Ln = La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) in thin films grown by atomic layer deposition. They have also investigated the possibility to improve the overall energy transfer from TiO{sub 2} to Yb{sup 3+} with a second Ln{sup 3+}, in order to enhance down conversion. The films were grown at a substrate temperature of 300 °C, using the Ln(thd){sub 3}/O{sub 3} (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and TiCl{sub 4}/H{sub 2}O precursor pairs. The focus of the work is to explore the energy transfer from TiO{sub 2} to Ln{sup 3+} ions, and the energy transfer between Ln{sup 3+} and Yb{sup 3+} ions, which could lead to efficient down conversion. The samples have been characterized by x-ray diffraction, x-ray fluorescence, spectroscopic ellipsometry, and photoluminescence. All films were amorphous as deposited, and the samples have been annealed at 600, 800, and 1000 °C in order to investigate the correlation between the crystallinity and luminescence. The lanthanum titanium oxide samples showed a weak and broad emission centered at 540 nm, which was absent in all the other samples, indicating energy transfer from TiO{sub 2} to Ln{sup 3+} in all other lanthanide samples. In the amorphous phase, all samples, apart from La, Tb, and Tm, showed a typical f-f emission when excited by a 325 nm HeCd laser. None of the samples showed any luminescence after annealing at 1000 °C due to the formation of Ln{sub 2}Ti{sub 2}O{sub 7}. Samples containing Nd, Sm, and Eu show a change in emission spectrum when annealed at 800 °C compared to the as-deposited samples, indicating that the smaller lanthanides crystallize in a different manner than the larger

  19. Structural, morphological and mechanical properties of niobium nitride thin films grown by ion and electron beams emanated from plasma

    Science.gov (United States)

    Siddiqui, Jamil; Hussain, Tousif; Ahmad, Riaz; Umar, Zeeshan A.; Abdus Samad, Ubair

    2016-05-01

    The influence of variation in plasma deposition parameters on the structural, morphological and mechanical characteristics of the niobium nitride films grown by plasma-emanated ion and electron beams are investigated. Crystallographic investigation made by X-ray diffractometer shows that the film synthesized at 10 cm axial distance with 15 plasma focus shots (PFS) exhibits better crystallinity when compared to the other deposition conditions. Morphological analysis made by scanning electron microscope reveals a definite granular pattern composed of homogeneously distributed nano-spheroids grown as clustered particles for the film synthesized at 10 cm axial distance for 15 PFS. Roughness analysis demonstrates higher rms roughness for the films synthesized at shorter axial distance and by greater number of PFS. Maximum niobium atomic percentage (35.8) and maximum average hardness (19.4 ± 0.4 GPa) characterized by energy-dispersive spectroscopy and nano-hardness analyzer respectively are observed for film synthesized at 10 cm axial distance with 15 PFS.

  20. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  1. Interface morphology studies of liquid phase epitaxy grown HgCdTe films by atomic force microscopy

    Science.gov (United States)

    Azoulay, M.; George, M. A.; Burger, A.; Collins, W. E.; Silberman, E.

    1994-04-01

    In this paper we report an investigation of the morphology of the interfaces of liquid phase epitaxy (LPE) grown HgCdTe thin films on CdTe and CdZnTe substrates by atomic force microscopy (AFM) on freshly cleaved (110) crystallographic planes. An empirical observation which may be linked to lattice mismatch was indicated by an angle between the cleavage steps of the substrate to those of the film. The precipitates with size ranging from 5 nm to 20 nm were found to be most apparent near the interface.

  2. On the scalability of doped hafnia thin films

    Science.gov (United States)

    Adelmann, C.; Schram, T.; Chew, S.-A.; Woicik, J. C.; Brizzi, S.; Tallarida, M.; Schmeisser, D.; Horiguchi, N.; Van Elshocht, S.; Ragnarsson, L.-Å.

    2014-03-01

    The scaling behavior of Gd- and Al-doped HfO2 films as gate dielectrics in metal-oxide-semiconductor (MOS) capacitors was studied. For equivalent oxide thicknesses (EOTs) in the range of 10 Å, crystallized Gd:HfO2 showed higher leakage current densities than crystallized Al:HfO2, with undoped HfO2 in between. Ultimately, the scalability of Al:HfO2 was limited by the ability to crystallize the films at a given thermal budget. As a result, for post-deposition annealing at 800 °C, the EOT of Al:HfO2 based MOS capacitors was limited to ˜8 Å. However, for such an EOT, leakage current densities were reduced by about 100× with respect to HfO2. This demonstrates the high potential of Al:HfO2 for low-standby-power MOS devices.

  3. Oxygen Recovery in Hf Oxide Films Fabricated by Sputtering

    Institute of Scientific and Technical Information of China (English)

    JIANG Ran; LI Zi-Feng

    2009-01-01

    The chemical structure of ultrathin Hf oxide films (< 10 nm) fabricated by a standard sputtering method is investigated using x-ray spectroscopy and Rutherford backscattering spectroscopy. According to the experiments,oxygen species are impacted to the HfO2/Si interface during the initial sputtering, and then released back to the upper Hf02 region driven by the oxygen concentration grads. A vacuum annealing can greatly enhance this recovery process. Additionally, significant SiO2 reduction in the interface is observed after the vacuum annealing for the thick HfO2 films in our experiment. It might be an effective method to confine the interracial layer thickness by sputtering thick HfO2 in no-oxygen ambient.

  4. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  5. The influence of epitaxial Ti buffer layers for fabricating as-grown MgB{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Oba, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan)]. E-mail: t3806005@iwate-u.ac.jp; Sun, P. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Harada, Y. [JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan); Takahashi, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Seki, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Noguchi, S. [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); JST-CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ishida, T. [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); JST-CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan)

    2007-03-15

    We have measured the magnetic field dependence of the resistivity using a 35T pulsed magnet for the as-grown MgB{sub 2} films fabricated on the epitaxial Ti buffer layer grown on c-plane ZnO and Al{sub 2}O{sub 3} substrates by molecular beam epitaxy (MBE). We will report the upper critical fields (H{sub c2}) along H||c-axis and H||ab-plane. The anisotropy ratio were obtained from these H{sub c2} values. The effects of Ti buffer layer on the H{sub c2} and the anisotropy of MgB{sub 2} film were discussed.

  6. Synthesis of as-grown superconducting MgB{sub 2} thin films by molecular beam epitaxy in UHV conditions

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y.; Uduka, M.; Nakanishi, Y.; Yoshimoto, N.; Yoshizawa, M

    2004-10-01

    As-grown superconducting MgB{sub 2} thin films have been grown on SrTiO{sub 3}(0 0 1), MgO(0 0 1), and Al{sub 2}O{sub 3}(0 0 0 1) substrates by a molecular beam epitaxy (MBE) method with novel co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The RHEED patterns indicate three-dimensional growth for MgB{sub 2}. The highest T{sub c} determined by resistivity measurement was about 36 K in these samples. And a clear Meissner effect below T{sub c} was observed using magnetic susceptibility measurement. We will discuss the influence of B buffer layer on the structural and physical properties.

  7. Theoretical analyses of In incorporation and compositional instability in coherently grown InGaN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yayama, Tomoe [Department of Aeronautics and Astronautics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Kangawa, Yoshihiro; Kakimoto, Koichi [Department of Aeronautics and Astronautics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Koukitu, Akinori [Division of Applied Chemistry, Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 184-8588, Koganei (Japan)

    2010-07-15

    We performed thermodynamic analyses to calculate the relationship between the input indium molar ratio and solid composition of a coherently grown InGaN thin film that is subjected compressive or tensile stress. The theoretical approach incorporates energy loss of a thin film system due to lattice constraint from the substrate. The results show that the indium composition x of coherently grown InGaN is lower than that of stress-free InGaN. This represents the composition pulling effect. We also studied stable growth modes under various growth conditions. The results suggest the importance of control of partial pressure of NH{sub 3} to optimize growth conditions of InGaN with a unique composition. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Enhancement of supercapacitance property of electrochemically deposited MnO2 thin films grown in acidic medium

    Science.gov (United States)

    Jana, S. K.; Rao, V. P.; Banerjee, S.

    2014-02-01

    In this communication we present supercapacitance property of MnO2 thin-films which are fabricated on stainless steel (SS) substrate by electro-deposition method carried out in different pH of the electrolyte. A significant improvement of the device performance of acid mediated grown (AMG) MnO2 over normal MnO2 (grown in neutral medium) has been achieved. We have also investigated role of interfacial structure on the internal resistance of the device material. AMG MnO2 film exhibits superior device performance with specific capacitance of 652 F/g which is 2 times better than that obtained in normal MnO2 and also energy density of 90.69 Wh/kg.

  9. Dielectric and Structural Properties of SrTiO_3 Thin Films Grown by Laser Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Dielectric and Structural Properties of SrTiO_3 Thin Films Grown by Laser Molecular Beam Epitaxy[1]Hao J H,Gao J,Wang Z,et al.Interface structure and phase of epitaxial SrTi O3(110)thin fil ms grown directly on silicon[J].Appl Phys Lett,2005,87:131908. [2]Hao J H,Gao J,Wang HK.SrTi O3(110)thin fil ms grown directly on different oriented silicon substrates[J].Appl Phys A,2005,81:1233. [3]Aki mov I A,Sirenko A A,Clark A M,et al.Electric-field-induced soft-mode hardening in SrTi O3fil ms[J].Phys Rev Lett...

  10. Characteristics of atomic layer deposition grown HfO{sub 2} films after exposure to plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y.W. [Kookje Electric Korea Co. LTD, 4-2 Chaam-Dong, Chonan-Si, Chungcheongnam-Do (Korea, Republic of)]. E-mail: ywkim@kekorea.co.kr; Roh, Y. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Yoo, Ji-Beom [School of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)]. E-mail: jibyoo@skku.ac.kr; Kim, Hyoungsub [School of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2007-01-22

    Ultra thin HfO{sub 2} films were grown by the atomic layer deposition (ALD) technique using tetrakismethylethylaminohafnium (Hf[N(CH){sub 3}(C{sub 2}H{sub 5})]{sub 4}) and ozone (O{sub 3}) as the precursors and subsequently exposed to various plasma conditions, i.e., CCP (capacitively coupled plasma) and MMT (modified magnetron typed plasma) in N{sub 2} or N{sub 2}/O{sub 2} ambient. The conventional CCP treatment was not effective in removing the carbon impurities, which were incorporated during the ALD process, from the HfO{sub 2} films. However, according to the X-ray photoelectron spectroscopy measurements, the MMT treated films exhibited a significant reduction in their carbon contents and the efficient incorporation of nitrogen atoms. Although the incorporated nitrogen was easily released during the post-thermal annealing of the MMT treated samples, it was more effective than the CCP treatment in removing the film impurities. Consequently, the MMT treated samples exhibited excellent electrical properties as compared to the as-deposited HfO{sub 2} films, including negligible hysteresis (flatband voltage shift), a low leakage current, and the reduced equivalent oxide thickness of the gate stack. In conclusion, MMT post treatment is more effective than conventional CCP treatment in improving the electrical properties of high-k films by reducing the carbon contamination and densifying the as-deposited defective films.

  11. Substrate dependent structural, optical and electrical properties of ZnS thin films grown by RF sputtering

    Science.gov (United States)

    Pathak, Trilok K.; Kumar, Vinod; Purohit, L. P.; Swart, H. C.; Kroon, R. E.

    2016-10-01

    Zinc sulphide (ZnS) films are of great importance for applications in various optoelectronic devices. ZnS thin films were grown on glass, indium tin oxide (ITO) and Corning glass substrates by radio-frequency magnetron sputtering at a temperature of 373 K and a comparative study of the structural, optical and electrical properties was performed using X-ray diffraction (XRD), scanning electron microscopy, optical and current-voltage (I-V) measurements. The XRD patterns showed that the sputtered thin films exhibited good crystallinity with the (111) peak around 2θ=28.3° indicating preferential orientation of the cubic structure. The maximum strain and most densely packed grains were obtained for the Corning glass substrate. The transmittance spectra of the films were measured in the wavelength range from 200 to 800 nm, showing that the films are about 77% transparent in the visible region. A slight change of 3.50 eV to 3.54 eV was found for the bandgap of the films deposited on different substrates. The ZnS thin films deposited on Corning glass show better crystallinity, morphology and I-V characteristics than that deposited on ordinary glass and ITO substrates.

  12. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Science.gov (United States)

    Fedoseeva, Yu. V.; Pozdnyakov, G. A.; Okotrub, A. V.; Kanygin, M. A.; Nastaushev, Yu. V.; Vilkov, O. Y.; Bulusheva, L. G.

    2016-11-01

    Since amorphous oxygenated hydrocarbon (COxHy) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of COxHy films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the COxHy films, deposited at 300 and 500 °C, were mainly composed of the sp2-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  13. Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric

    Science.gov (United States)

    Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

    2017-01-01

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS2 and an ultra-thin HfO2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS2-HfO2 interface is responsible for the generation of interface states with a density (Dit) reaching ~7.03 × 1011 cm−2 eV−1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in Dit could be achieved by thermally diffusing S atoms to the MoS2-HfO2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS2 devices with carrier transport enhancement. PMID:28084434

  14. Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric

    Science.gov (United States)

    Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

    2017-01-01

    Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS2 and an ultra-thin HfO2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS2-HfO2 interface is responsible for the generation of interface states with a density (Dit) reaching ~7.03 × 1011 cm-2 eV-1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in Dit could be achieved by thermally diffusing S atoms to the MoS2-HfO2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS2 devices with carrier transport enhancement.

  15. Effects of packing materials on the sensitivity of RadFET with HfO2 gate dielectric for electron and photon sources

    Science.gov (United States)

    Kahraman, A.; Yilmaz, E.; Kaya, S.; Aktag, A.

    2015-10-01

    The radiation sensing field effect transistor (RadFET) with SiO2 gate oxide has been commonly used as a device component or dosimetry system in the radiation applications such as space research, radiotherapy, and high-energy physics experiments. However, alternative gate oxides and more suitable packaging materials are still demanded for these dosimeters. HfO2 is one of the most attractive gate oxide materials that are currently under investigation by many researchers. In this study, Monte Carlo simulations of the average deposited energy in RadFET dosimetry systems with different package lid materials for point electron and photon sources were performed with the aim of evaluating the effects of package lids on the sensitivity of the RadFET by using HfO2 as a gate dielectric material. The RadFET geometry was defined in a PENGEOM package and electron-photon transport was simulated by a PENELOPE code. The relatively higher average deposited energies in the sensitive region (HfO2 layer) for electron energies of 250 keV-20 MeV were obtained from the RadFET with the Al2O3 package lid despite of some deviations from the general tendency. For the photon energies of 20-100 keV, the average amount of energy deposited in RadFET with Al2O3 package was higher compared with the other capped devices. The average deposited energy in the sensitive region was quite close to each other at 200 keV for both capped and uncapped devices. The difference in the average deposited energy of the RadFET with different package lid materials was not high for photon energies of 200-1200 keV. The increase in the average deposited energy in the HfO2 layer of the RadFET with Ta package lid was higher compared with the other device configurations above 3 MeV.

  16. Damage on HfO2/SiO2 high-reflecting coatings under single and multiple Nd:YAG laser pulse irradiation

    Institute of Scientific and Technical Information of China (English)

    Weidong Gao; Tao Wang; Yuanan Zhao; Jianda Shao

    2005-01-01

    The single- and multi-shot damage behaviors of HfO2/SiO2 high-reflecting (HR) coatings under Nd:YAG laser exposure were investigated. Fundamental aspects of multi-shot laser damage, such as the instability due to pulse-to-pulse accumulation of absorption defect and structural defect effect, and the mechanism of laser induced defect generation, are considered. It was found in multi-shot damage, the main factors influencing laser-induced damage threshold (LIDT) are accumulation of irreversible changes of structural defects and thermal stress that induced by thermal density fluctuations.

  17. Examination of flatband and threshold voltage tuning of HfO2/TiN field effect transistors by dielectric cap layers

    Science.gov (United States)

    Guha, S.; Paruchuri, V. K.; Copel, M.; Narayanan, V.; Wang, Y. Y.; Batson, P. E.; Bojarczuk, N. A.; Linder, B.; Doris, B.

    2007-02-01

    The authors have examined the role of sub nanometer La2O3 and LaN cap layers interposed in Si /HfO2/TiN high-k gate dielectric stacks in tuning the flatband and threshold voltages of capacitors and transistors. High performance, band edge n metal oxide field effect transistors with channel lengths down to 60nm may be fabricated without significant compromise in mobility, electrical thickness, and threshold voltage. They have carried out a microstructural evaluation of these stacks and correlated these results with the electrical behavior of the devices.

  18. The Luminescent Properties and Atomic Structures of As-Grown and Annealed Nanostructured Silicon Rich Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    N. D. Espinosa-Torres

    2016-01-01

    Full Text Available Not long ago, we developed a theoretical model to describe a set of chemical reactions that can potentially occur during the process of obtaining Silicon Rich Oxide (SRO films, an off stoichiometry material, notwithstanding the technique used to grow such films. In order to elucidate the physical chemistry properties of such material, we suggested the chemical reactions that occur during the process of growing of SRO films in particular for the case of the Low Pressure Chemical Vapor Deposition (LPCVD technique in the aforementioned model. The present paper represents a step further with respect to the previous (published work, since it is dedicated to the calculation by Density Functional Theory (DFT of the optical and electronic properties of the as-grown and annealed SRO structures theoretically predicted on the basis of the previous work. In this work, we suggest and evaluate either some types of molecules or resulting nanostructures and we predict theoretically, by applying the DFT, the contribution that they may have to the phenomenon of luminescence (PL, which is experimentally measured in SRO films. We evaluated the optical and electronic properties of both the as-grown and the annealed structures.

  19. Room temperature ferromagnetism in epitaxial Cr{sub 2}O{sub 3} thin films grown on r-sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Punugupati, Sandhyarani, E-mail: spunugu@ncsu.edu; Narayan, Jagdish; Hunte, Frank [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-05-21

    We report on the epitaxial growth and magnetic properties of Cr{sub 2}O{sub 3} thin films grown on r-sapphire substrate using pulsed laser deposition. The X-ray diffraction (XRD) (2θ and Φ) and TEM characterization confirm that the films are grown epitaxially. The r-plane (011{sup ¯}2) of Cr{sub 2}O{sub 3} grows on r-plane of sapphire. The epitaxial relations can be written as [011{sup ¯}2] Cr{sub 2}O{sub 3} ‖ [011{sup ¯}2] Al{sub 2}O{sub 3} (out-of-plane) and [1{sup ¯}1{sup ¯}20] Cr{sub 2}O{sub 3} ‖ [1{sup ¯}1{sup ¯}20] Al{sub 2}O{sub 3} (in-plane). The as-deposited films showed ferromagnetic behavior up to 400 K but ferromagnetism almost vanishes with oxygen annealing. The Raman spectroscopy data together with strain measurements using high resolution XRD indicate that ferromagnetism in r-Cr{sub 2}O{sub 3} thin films is due to the strain caused by defects, such as oxygen vacancies.

  20. Investigation of the optimal annealing temperature for the enhanced thermoelectric properties of MOCVD-grown ZnO films

    Science.gov (United States)

    Mahmood, K.; Ali, A.; Arshad, M. I.; Ajaz un Nabi, M.; Amin, N.; Faraz Murtaza, S.; Rabia, S.; Azhar Khan, M.

    2017-04-01

    In this study, we demonstrate the optimization of the annealing temperature for enhanced thermoelectric properties of ZnO. Thin films of ZnO are grown on a sapphire substrate using the metal organic chemical Vapor Deposition (MOCVD) technique. The grown films are annealed in an oxygen environment at 600-1000°C, with a step of 100°C for one hour. Seebeck measurements at room temperature revealed that the Seebeck coefficient of the sample that was not annealed was 152 μV/K, having a carrier concentration of N D 1.46 × 1018 cm-3. The Seebeck coefficient of the annealed films increased from 212 to 415 μV/K up to 900°C and then decreased at 1000°C. The power factor is calculated and found to have an increasing trend with the annealing temperature. This observation is explained by the theory of Johnson and Lark-Horovitz that thermoelectric properties are enhanced by improving the structure of ZnO thin films. The Hall measurements and PL data strongly justify the proposed argument.

  1. Properties of boron and phosphorous incorporated tetrahedral amorphous carbon films grown using filtered cathodic vacuum arc process

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Khan, Mohd Alim [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Satyanarayana, B.S. [40, Sreeniketan, NDSE 24, New Delhi 110096 (India); Kumar, Sushil; Ishpal [Plasma Processed Materials Group, National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2010-04-15

    This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity ({sigma}{sub D}), activation energy ({Delta}E{sub 1}), hardness, microstructure, emission threshold (E{sub turn-ON}) and emission current density (J) at 12.5 V/{mu}m of ta-C: B and ta-C: P films deposited at a high negative substrate bias of -300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in {sigma}{sub D} and corresponding decrease in {Delta}E{sub 1} and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that E{sub turn-ON} increases and J decreases. The changes are attributed to the changes in the sp{sup 3}/sp{sup 2} ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.

  2. Surface morphologies of MOCVD-grown GaN films on sapphire studied by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J.; Reddic, J.E.; Sinha, M.; Ricker, W.S.; Karlinsey, J.; Yang, J.-W.; Khan, M.A.; Chen, D.A

    2002-12-30

    The surface morphologies of MOCVD GaN films grown on sapphire substrates have been investigated by scanning tunneling microscopy (STM). High quality STM images could not be obtained prior to cleaning the les in HF, hot HCl or 2 M NaOH. STM images of the GaN films showed that the surfaces consisted of curved step edges and interlocking terraces, which were roughly 224 nm wide. Surface pits approximately 2-5 nm deep and 50-80 nm wide were observed on the GaN films, and these pits were preferentially located at a juncture between two step edges. Previous studies in the literature involving MOCVD-grown GaN on sapphire have demonstrated that the surface pits are associated with screw-component threading dislocations. Therefore, the number of screw-component threading dislocations in these GaN films is estimated as 6.3x10{sup 8} cm{sup -2} from the number surface pits observed in the STM images. X-ray photoelectron studies indicated that the major surface contaminants before cleaning were carbon and oxygen. Treatment in HF or HCl removed oxygen from the surface while treatment in NaOH was more effective at removing surface carbon.

  3. Unpredicted surface termination of α-Fe2O3(0001) film grown by mist chemical vapor deposition

    Science.gov (United States)

    Osaka, Shun; Kubo, Osamu; Takahashi, Kazuki; Oda, Masaya; Kaneko, Kentaro; Tabata, Hiroshi; Fujita, Shizuo; Katayama, Mitsuhiro

    2017-06-01

    We analyze the surface structure of an α-Fe2O3(0001) film grown on a c-plane sapphire substrate by mist chemical vapor deposition (CVD), which has been recently developed as a simple, safe, and cost-effective film growth method. Using coaxial impact-collision ion scattering spectroscopy, we found that the atomic-layer sequence of the surface termination of an α-Fe2O3(0001) film grown by mist CVD was Fe-O3-Fe- from the top layer. This surface termination is predicted to form in an oxygen-poor environment by density functional theory combined with a thermodynamical approach despite that the mist CVD process is performed with atmospheric-pressure air. The surface structure markedly changes after annealing above 600 °C in ultrahigh vacuum. We found that only a couple of layers from the top layer transform into Fe3O4(111) after 650 °C annealing, which would be so-called biphase reconstruction. Complete transformation into a Fe3O4(111) film occurs at 700 °C, whose atomic-layer sequence is determined to be Fe-O4-Fe3- from the top layer.

  4. Embedded polytypes in Bi2Sr2-xLaxCuO6 thin films grown by laser ablation

    Science.gov (United States)

    Cancellieri, C.; Lin, P. H.; Ariosa, D.; Pavuna, D.

    2007-11-01

    We investigate the presence of secondary phases in La-doped Bi-2201 thin films grown by laser ablation. The cation ratios in the target material, the oxygen pressure, and the substrate temperature during the deposition are the main parameters determining the presence of diluted intergrowth and/or polytype aggregates. A statistical model of random intergrowth is used to analyze the x-ray diffraction (XRD) anomalies caused by hidden defects and to characterize the latter. A detailed structural XRD refinement on oriented aggregates allows us to identify the guest phase as a Bi deficient phase, Bi-1201. The occurrence of this particular embedded polytype is accompanied by a global Bi deficiency introduced in the films by the growing process and/or by the annealing treatment. The presence of La favors the Bi-1201 formation mostly as La-rich c -axis oriented aggregates. Bi excess in the target material improves considerably the crystallographic structure of Bi-2201, avoids intergrowth formation, but does not prevent the phase separation of Bi-1201 in La-doped thin films. We also investigate the influence of the deposition parameters on the type of intergrowth as well as their variation with La doping. This work introduces a specific methodology for optimizing the growth of thin films grown by laser ablation, which applies to layered oxides that admit polytypes with close formation enthalpies in their phase diagram.

  5. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Energy Technology Data Exchange (ETDEWEB)

    Fedoseeva, Yu. V., E-mail: fedoseeva@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Pozdnyakov, G.A. [Khristianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk 630090 (Russian Federation); Okotrub, A.V.; Kanygin, M.A. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nastaushev, Yu. V. [Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Vilkov, O.Y. [St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Bulusheva, L.G. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation)

    2016-11-01

    Highlights: • A deposition of supersonic methane plasma flow on silicon substrate produces amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) film. • The thickness, composition, and wettability of the film depend on the substrate temperature. • A rise of the substrate temperature from 500 to 700 °C promotes the sp{sup 3}-hybridization carbon formation. - Abstract: Since amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of CO{sub x}H{sub y} films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the CO{sub x}H{sub y} films, deposited at 300 and 500 °C, were mainly composed of the sp{sup 2}-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  6. Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

    KAUST Repository

    Xing, G. Z.

    2014-05-23

    We report the magnetic and magnetotransport properties of (In 0.985Nd0.015)2O2.89 thin films grown by pulse laser deposition. The clear magnetization hysteresis loops with the complementary magnetic domain structure reveal the intrinsic room temperature ferromagnetism in the as-prepared films. The strong sp-f exchange interaction as a result of the rare earth doping is discussed as the origin of the magnetotransport behaviours. A positive magnetoresistance (∼29.2%) was observed at 5 K and ascribed to the strong ferromagnetic sp-f exchange interaction in (In0.985Nd0.015)2O 2.89 thin films due to a large Zeeman splitting in an external magnetic field of 50 KOe. © 2014 AIP Publishing LLC.

  7. Novel stage in fabrication of as-grown MgB{sub 2} films by adopting Ti seed layer

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y. [JST Satellite Iwate, Japan Science and Technology Agency, 3-35-2 Iiokashinden, Morioka, Iwate 020-0852 (Japan)], E-mail: yharada@iwate-jst-satellite.jp; Yamaguchi, H. [National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Oba, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Fujine, Y. [JST Satellite Iwate, Japan Science and Technology Agency, 3-35-2 Iiokashinden, Morioka, Iwate 020-0852 (Japan); Goto, S. [Lightom, Sugo 95-2, Takizawa 020-0173 (Japan); Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Yoshizawa, M. [National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan)

    2007-10-01

    We report that Ti buffer layer improves the structural quality and superconducting properties of MgB{sub 2} film deposited on ZnO (0 0 0 1) and Al{sub 2}O{sub 3} (0 0 0 1) substrates using molecular beam epitaxy. It was found that Ti layers were grown epitaxially on the substrates and the MgB{sub 2} films were c-axis oriented with two types of in-plane orientations. The crystal quality measured by the rocking curve width of X-ray diffraction peak was improved and superconducting transition temperature increased as the buffer layer thickness increased on both substrates. The highest T{sub c} observed in this study was 37 K and 35 K in the film deposited on the Ti buffer layer 50 nm thick with the ZnO and Al{sub 2}O{sub 3} substrates, respectively.

  8. Dislocation densities reduction in MBE-grown AlN thin films by high-temperature annealing

    Science.gov (United States)

    Nemoz, Maud; Dagher, Roy; Matta, Samuel; Michon, Adrien; Vennéguès, Philippe; Brault, Julien

    2017-03-01

    AlN thin films, grown on (0001) sapphire substrates by molecular beam epitaxy (MBE), were annealed at high temperature (up to 1650 °C) in flowing N2. X-ray diffraction (XRD) studies, combined with Williamson-Hall and Srikant plots, have shown that annealing leads to a strong reduction of both edge and mixed threading dislocation densities, as confirmed by transmission electron microscopy (TEM) images, up to 75%. Moreover, it is found that annealing at high temperatures allows the relaxation of the tensile strain in the AlN film due to the growth process. In addition, the morphological properties of the films were determined by atomic force microscopy (AFM) and show that the annealing conditions have a strong impact on the surface morphology and roughness. Finally, an annealing at 1550 °C for 20 min appears as an ideal tradeoff to enhance the structural properties while preserving the initial AlN surface morphology.

  9. Hardness, elastic modulus, and wear resistance of hafnium oxide-based films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Berdova, Maria; Liu, Xuwen; Franssila, Sami, E-mail: sami.franssila@aalto.fi [Department of Materials Science and Engineering, Aalto University, 02150 Espoo (Finland); Wiemer, Claudia; Lamperti, Alessio; Tallarida, Grazia; Cianci, Elena [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Fanciulli, Marco [Laboratorio MDM, IMM CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB), Italy and Dipartimento di Scienza dei Materiali, Università degli studi di Milano Bicocca, 20126 Milano (Italy)

    2016-09-15

    The investigation of mechanical properties of atomic layer deposition HfO{sub 2} films is important for implementing these layers in microdevices. The mechanical properties of films change as a function of composition and structure, which accordingly vary with deposition temperature and post-annealing. This work describes elastic modulus, hardness, and wear resistance of as-grown and annealed HfO{sub 2}. From nanoindentation measurements, the elastic modulus and hardness remained relatively stable in the range of 163–165 GPa and 8.3–9.7 GPa as a function of deposition temperature. The annealing of HfO{sub 2} caused significant increase in hardness up to 14.4 GPa due to film crystallization and densification. The structural change also caused increase in the elastic modulus up to 197 GPa. Wear resistance did not change as a function of deposition temperature, but improved upon annealing.

  10. Unconventional magnetization of Fe3O4 thin film grown on amorphous SiO2 substrate

    Directory of Open Access Journals (Sweden)

    Jia-Xin Yin

    2016-06-01

    Full Text Available High quality single crystal Fe3O4 thin films with (111 orientation had been prepared on amorphous SiO2 substrate by pulsed laser deposition. The magnetization properties of the films are found to be unconventional. The Verwey transition temperature derived from the magnetization jump is around 140K, which is higher than the bulk value and it can be slightly suppressed by out-plane magnetic field; the out-of-plane magnetization, which is unexpectedly higher than the in-plane value, is also significantly increased as compared with the bulk value. Our findings highlight the unusual magnetization of Fe3O4 thin film grown on the amorphous SiO2 substrate.

  11. Effects of nitrogen on the growth and optical properties of ZnO thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Cui, J B; Thomas, M A; Soo, Y C; Kandel, H; Chen, T P [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States)

    2009-08-07

    ZnO thin films were grown using pulsed laser deposition by ablating a Zn target in various mixtures of O{sub 2} and N{sub 2}. The presence of N{sub 2} during deposition was found to affect the growth of the ZnO thin films and their optical properties. Small N{sub 2} concentrations during growth led to strong acceptor-related photoluminescence (PL), while larger concentrations affected both the intensity and temperature dependence of the emission peaks. In addition, the PL properties of the annealed ZnO thin films are associated with the N{sub 2} concentration during their growth. The possible role of nitrogen in ZnO growth and annealing is discussed.

  12. Magnetic properties of Sm-Co thin films grown on MgO(100) deposited from a single alloy target

    Energy Technology Data Exchange (ETDEWEB)

    Verhagen, T. G. A.; Boltje, D. B.; Ruitenbeek, J. M. van; Aarts, J., E-mail: aarts@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, P.O. Box 9504, 2300 RA Leiden (Netherlands)

    2014-08-07

    We have grown epitaxial Sm-Co thin films by sputter deposition from a single alloy target with a nominal SmCo{sub 5} composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo{sub 5}-like to a Sm{sub 2}Co{sub 7}-like phase. The composition, crystal structure, morphology, and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction, and magnetization measurements. We find that we can grow films with, at room temperature, coercive fields as high as 3.3 T, but with a remanent magnetization which is lower than can be expected from the texturing. This appears to be due to the Sm content of the films, which is higher than expected from the content of the target, even at the lowest possible sputtering pressures. Moreover, we find relatively large variations of film properties using targets of nominally the same composition. At low temperatures, the coercive fields increase, as expected for these hard magnets, but in the magnetization, we observe a strong background signal from the paramagnetic impurities in the MgO substrates.

  13. Magnetic properties of Sm-Co thin films grown on MgO(100) deposited from a single alloy target

    Science.gov (United States)

    Verhagen, T. G. A.; Boltje, D. B.; van Ruitenbeek, J. M.; Aarts, J.

    2014-08-01

    We have grown epitaxial Sm-Co thin films by sputter deposition from a single alloy target with a nominal SmCo5 composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo5-like to a Sm2Co7-like phase. The composition, crystal structure, morphology, and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction, and magnetization measurements. We find that we can grow films with, at room temperature, coercive fields as high as 3.3 T, but with a remanent magnetization which is lower than can be expected from the texturing. This appears to be due to the Sm content of the films, which is higher than expected from the content of the target, even at the lowest possible sputtering pressures. Moreover, we find relatively large variations of film properties using targets of nominally the same composition. At low temperatures, the coercive fields increase, as expected for these hard magnets, but in the magnetization, we observe a strong background signal from the paramagnetic impurities in the MgO substrates.

  14. Photo- and Electrochromic Properties of Activated Reactive Evaporated MoO3 Thin Films Grown on Flexible Substrates

    Directory of Open Access Journals (Sweden)

    K. Hari Krishna

    2008-01-01

    Full Text Available The molybdenum trioxide (MoO3 thin films were grown onto ITO-coated flexible Kapton substrates using plasma assisted activated reactive evaporation technique. The film depositions were carried out at constant glow power and oxygen partial pressures of 8 W and 1×10−3 Torr, respectively. The influence of substrate temperature on the microstructural and optical properties was investigated. The MoO3 thin films prepared at a substrate temperature of 523 K were found to be composed of uniformly distributed nanosized grains with an orthorhombic structure of α-MoO3. These nanocrystalline MoO3 thin films exhibited higher optical transmittance of about 80% in the visible region with an evaluated optical band gap of 3.29 eV. With the insertion of 12.5 mC/cm2, the films exhibited an optical modulation of 40% in the visible region with coloration efficiency of 22 cm2/C at the wavelength of 550 nm. The MoO3 films deposited at 523 K demonstrated better photochromic properties and showed highest color center concentration for the irradiation time of 30 minutes at 100 mW/cm2.

  15. Raman analyses of residual stress in diamond thin films grown on Ti6Al4V alloy

    Directory of Open Access Journals (Sweden)

    Azevedo Adriana F.

    2003-01-01

    Full Text Available The stress evolution in diamond films grown on Ti6Al4V was investigated in order to develop a comprehensive view of the residual stress formation. Residual stress is composed of intrinsic stress induced during diamond film growth and extrinsic stress caused by the different thermal expansion coefficients between the film and substrate. In the coalescence stage it has been observed that the residual stress is dominated by the microstructure, whereas on continuous films, the thermal stress is more important. In this work diamond thin films with small grain size and good size and good quality were obtained in a surface wave-guide microwave discharge, the Surfatron system, with a negative bias voltage applied between the plasma shell and substrate. For above of -100V applied bias, the ratio of carbon sp³/sp² bond may increase and the nucleation rate increase arising the high value at the -250V applied bias. Stress measurements and sp³ content in the film were studied by Raman scattering spectroscopy. The total residual stress is compressive and varied from -1.52 to -1.48 GPa between 0 and -200 V applied bias, respectively, and above the -200 V, the compressive residual stress increased drastically to -1.80 GPa. The diamond nucleation density was evaluated by top view SEM images.

  16. Anomalous thickness-dependent optical energy gap of ALD-grown ultra-thin CuO films

    Science.gov (United States)

    Tripathi, T. S.; Terasaki, I.; Karppinen, M.

    2016-11-01

    Usually an inverse square relation between the optical energy gap and the size of crystallites is observed for semiconducting materials due to the strong quantum localization effect. Coulomb attraction that may lead to a proportional dependence is often ignored or considered less important to the optical energy gap when the crystallite size or the thickness of a thin film changes. Here we report a proportional dependence between the optical energy gap and the thickness of ALD-grown CuO thin films due to a strong Coulomb attraction. The ultrathin films deposited in the thickness range of 9-81 nm show a p-type semiconducting behavior when analyzed by Seebeck coefficient and electrical resistivity measurements. The indirect optical energy gap nature of the films is verified from UV-vis spectrophotometric measurements. A progressive increase in the indirect optical energy gap from 1.06 to 1.24 eV is observed with the increase in the thickness of the films. The data are analyzed in the presence of Coulomb attractions using the Brus model. The optical energy gap when plotted against the cubic root of the thickness of the films shows a linear dependence.

  17. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, N. S., E-mail: nsokolov@fl.ioffe.ru; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V. [Ioffe Physical-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Maksimova, K. Yu.; Grunin, A. I. [Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Tabuchi, M. [Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603 (Japan)

    2016-01-14

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  18. Structural and Optical Properties of ZnO Films with Different Thicknesses Grown on Sapphire by MOCVD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    ZnO(002) films with different thicknesses, grown on Al2O3 (006) substrates by metal-organic chemical vapor deposition( MOCVD), were etched by Ar ion beams. The samples were examined by D8 X-ray diffraction, scanning electron microscopy(SEM), and photoluminescence (PL) spectrometry. The structural properties vary with the increasing thickness of the films. When the film thickness is thin, the phi(Φ) scanning curves for ZnO(103) and sapphire(116) substrate show the existence of two kinds of orientation relationships between ZnO films and sapphire,which are ZnO(002)//Al2O3 (006), ZnO(100)//Al2O3 (110) and ZnO(002)//Al2O3 (006), ZnO(110)//Al2O3(110). When the thickness increases to 500 nm there is only one orientation relationship, which is ZnO(002)//Al2O3 (006), ZnO [ 100 ]//Al2O3[ 110 ]. Their photoluminescence (PL) spectra at room temperature show that the optical properties of ZnO films have been greatly improved when increasing the thickness of films is increased.

  19. Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Bulusu, A.; Singh, A.; Kim, H. [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Wang, C. Y.; Dindar, A.; Fuentes-Hernandez, C.; Kippelen, B. [School of Electrical and Computer Engineering, Georgia Institute of Technology, and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332 (United States); Cullen, D. [Oak Ridge National Laboratory, P.O. Box 2008 MS-6064, Oak Ridge, Tennessee 37831 (United States); Graham, S., E-mail: sgraham@gatech.edu [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Oak Ridge National Laboratory, P.O. Box 2008 MS-6064, Oak Ridge, Tennessee 37831 (United States)

    2015-08-28

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al{sub 2}O{sub 3})/hafnium oxide (HfO{sub 2}) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiN{sub x} layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  20. SnO{sub 2} thin films grown by atomic layer deposition using a novel Sn precursor

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Min-Jung [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 (Korea, Republic of); Cho, Cheol Jin [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul, 151-744 (Korea, Republic of); Kim, Kwang-Chon; Pyeon, Jung Joon [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Park, Hyung-Ho [Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 (Korea, Republic of); Kim, Hyo-Suk; Han, Jeong Hwan; Kim, Chang Gyoun; Chung, Taek-Mo [Division of Advanced Materials, Korea Research Institute of Chemical Technology (KRICT), Daejeon, 305-600 (Korea, Republic of); Park, Tae Joo [Department of Materials Science and Engineering, Hanyang University, Ansan, 426-791 (Korea, Republic of); Kwon, Beomjin [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Jeong, Doo Seok; Baek, Seung-Hyub [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Nanomaterials, Korea University of Science and Technology, Daejeon, 305-333 (Korea, Republic of); Kang, Chong-Yun; Kim, Jin-Sang [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Kim, Seong Keun, E-mail: s.k.kim@kist.re.kr [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Department of Nanomaterials, Korea University of Science and Technology, Daejeon, 305-333 (Korea, Republic of)

    2014-11-30

    Highlights: • We developed a new ALD process for SnO{sub 2} films using dimethylamino-2-methyl-2-propoxy-tin(II) as a novel Sn precursor. • The SnO{sub 2} films grown from Sn(dmamp){sub 2} has negligible impurity contents. • Sn ions in the films had a single binding state corresponding to Sn{sup 4+} in SnO{sub 2}. - Abstract: SnO{sub 2} thin films were grown by atomic layer deposition (ALD) with dimethylamino-2-methyl-2-propoxy-tin(II) (Sn(dmamp){sub 2}) and O{sub 3} in a temperature range of 100–230 °C. The ALD window was found to be in the range of 100–200 °C. The growth per cycle of the films in the ALD window increased with temperature in the range from 0.018 to 0.042 nm/cycle. Above 230 °C, the self-limiting behavior which is a unique characteristic of ALD, was not observed in the growth because of the thermal decomposition of the Sn(dmamp){sub 2} precursor. The SnO{sub 2} films were amorphous in the ALD window and exhibited quite a smooth surface. Sn ions in all films had a single binding state corresponding to Sn{sup 4+} in SnO{sub 2}. The concentration of carbon and nitrogen in the all SnO{sub 2} films was below the detection limit of the auger electron spectroscopy technique and a very small amount of carbon, nitrogen, and hydrogen was detected by secondary ions mass spectroscopy only. The impurity contents decreased with increasing the growth temperature. This is consistent with the increase in the density of the SnO{sub 2} films with respect to the growth temperature. The ALD process with Sn(dmamp){sub 2} and O{sub 3} shows excellent conformality on a hole structure with an aspect ratio of ∼9. This demonstrates that the ALD process with Sn(dmamp){sub 2} and O{sub 3} is promising for growth of robust and highly pure SnO{sub 2} films.

  1. Magnetic and structural properties of Co{sub 2}FeAl thin films grown on Si substrate

    Energy Technology Data Exchange (ETDEWEB)

    Belmeguenai, Mohamed, E-mail: belmeguenai.mohamed@univ-paris13.fr [LSPM (CNRS-UPR 3407) 99 Avenue Jean-Baptiste Clément Université Paris 13, 93430 Villetaneuse (France); Tuzcuoglu, Hanife [LSPM (CNRS-UPR 3407) 99 Avenue Jean-Baptiste Clément Université Paris 13, 93430 Villetaneuse (France); Gabor, Mihai; Petrisor, Traian [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Street Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania); Tiusan, Coriolan [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Street Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania); Institut Jean Lamour, CNRS, Université de Nancy, BP 70239, F-54506 Vandoeuvre (France); Berling, Dominique [IS2M (CNRS-LRC 7228), 15 rue Jean Starcky, Université de Haute-Alsace, BP 2488, 68057 Mulhouse-Cedex (France); Zighem, Fatih; Mourad Chérif, Salim [LSPM (CNRS-UPR 3407) 99 Avenue Jean-Baptiste Clément Université Paris 13, 93430 Villetaneuse (France)

    2015-01-01

    The correlation between magnetic and structural properties of Co{sub 2}FeAl (CFA) thin films of different thicknesses (10 nmgrown at room temperature on MgO-buffered Si/SiO{sub 2} substrates and annealed at 600 °C has been studied. x-ray diffraction (XRD) measurements revealed an (011) out-of-plane textured growth of the films. The deduced lattice parameter increases with the film thickness. Moreover, pole figures showed no in-plane preferential growth orientation. The magneto-optical Kerr effect hysteresis loops showed the presence of a weak in-plane uniaxial anisotropy with a random easy axis direction. The coercive field, measured with the applied field along the easy axis direction, and the uniaxial anisotropy field increase linearly with the inverse of the CFA thickness. The microstrip line ferromagnetic resonance measurements for in-plane and perpendicular applied magnetic fields revealed that the effective magnetization and the uniaxial in-plane anisotropy field follow a linear variation versus the inverse CFA thickness. This allows deriving a perpendicular surface anisotropy coefficient of −1.86 erg/cm{sup 2}. - Highlights: • Various Co{sub 2}FeAl thin films were grown on a Si(001) substrates and annealed at 600 °C. • The thickness dependence of magnetic and structural properties has been studied. • X-ray measurements revealed an (011) out-of-plane textured growth of the films. • The easy axis coercive field varies linearly with the inverse CFA thickness. • The effective magnetization increases linearly with the inverse film thickness.

  2. Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties

    Science.gov (United States)

    Olsen, T.; Schröder, U.; Müller, S.; Krause, A.; Martin, D.; Singh, A.; Müller, J.; Geidel, M.; Mikolajick, T.

    2012-08-01

    Thin film capacitors were fabricated by sputtering TiN-Y doped HfO2-TiN stacks on silicon substrates. Yttrium was incorporated into the HfO2 layers by simultaneously sputtering from Y2O3 and HfO2 sources. Electric polarization and relative permittivity measurements yield distinct ferroelectric properties as a result of low yttrium dopant concentrations in the range of 0.9-1.9 mol. %. Grazing incidence x-ray diffraction measurements show the formation of an orthorhombic phase in this range. Compared to atomic layer deposition films, the highest remanent polarization and the highest relative permittivity were obtained at significantly lower doping concentrations in these sputtered films.

  3. Multi-technique Approach for the Evaluation of the Crystalline Phase of Ultrathin High-k Gate Oxide Films

    Science.gov (United States)

    Bersch, E.; LaRose, J. D.; Wells, I.; Consiglio, S.; Clark, R. D.; Leusink, G. J.; Matyi, R. J.; Diebold, A. C.

    2011-11-01

    In order to continue scaling metal oxide semiconductor field effect transistors (MOSFETs) with HfO2 gate oxides, efforts are being made to further improve the deposited high-k film properties. Recently, a process whereby an HfO2 film is deposited through a series of depositions and anneals (so-called DADA process) has been shown to result in films that give rise to MOS capacitors (MOSCAPs) which are electrically scaled compared to MOSCAPs with HfO2 films that only received post deposition anneals (PDA) or no anneals. We have measured as-deposited, DADA and PDA HfO2 films using four measurement techniques, all of which are non-destructive and capable of being used for in-line processing, to evaluate their crystallinity and crystalline phases. Grazing incidence in-plane X-ray diffraction was used to determine the crystalline phases of the HfO2 films. We observed the crystalline phases of these films to be process dependent. Additionally, X-ray and UV photoelectron spectroscopy were used to show the presence of crystallinity in the films. As a fourth technique, spectroscopic ellipsometry was used to determine if the crystalline phases were monoclinic. The combination of techniques was useful in that XPS and UPS were able to confirm the amorphous nature of a 30 cycle DADA film, as measured by GIIXRD, and GIIXRD was able to help us interpret the SE data as being an indication of the monoclinic phase of HfO2.

  4. Impact of Gate Dielectric in Carrier Mobility in Low Temperature Chalcogenide Thin Film Transistors for Flexible Electronics

    KAUST Repository

    Salas-Villasenor, A. L.

    2010-06-29

    Cadmium sulfide thin film transistors were demonstrated as the n-type device for use in flexible electronics. CdS thin films were deposited by chemical bath deposition (70° C) on either 100 nm HfO2 or SiO2 as the gate dielectrics. Common gate transistors with channel lengths of 40-100 μm were fabricated with source and drain aluminum top contacts defined using a shadow mask process. No thermal annealing was performed throughout the device process. X-ray diffraction results clearly show the hexagonal crystalline phase of CdS. The electrical performance of HfO 2 /CdS -based thin film transistors shows a field effect mobility and threshold voltage of 25 cm2 V-1 s-1 and 2 V, respectively. Improvement in carrier mobility is associated with better nucleation and growth of CdS films deposited on HfO2. © 2010 The Electrochemical Society.

  5. Deposition and characterization of titanium dioxide and hafnium dioxide thin films for high dielectric applications

    Science.gov (United States)

    Yoon, Meeyoung

    The industry's demand for higher integrated circuit density and performance has forced the gate dielectric layer thickness to decrease rapidly. The use of conventional SiO2 films as gate oxide is reaching its limit due to the rapid increase in tunneling current. Therefore, a need for a high dielectric material to produce large oxide capacitance and low leakage current has emerged. Metal-oxides such as titanium dioxide (TiO2) and hafnium dioxide (HfO2) are attractive candidates for gate dielectrics due to their electrical and physical properties suitable for high dielectric applications. MOCVD of TiO2 using titanium isopropoxide (TTIP) precursor on p-type Si(100) has been studied. Insertion of a TiO x buffer layer, formed by depositing metallic Ti followed by oxidation, at the TiO2/Si interface has reduced the carbon contamination in the TiO2 film. Elemental Ti films, analyzed by in-situ AES, were found to grow according to Stranski-Krastanov mode on Si(100). Carbon-free, stoichiometric TiO2 films were successfully produced on Si(100) without any parasitic SiO2 layers at the TiO 2/Si interface. Electron-beam deposition of HfO2 films on Si(100) has also been investigated in this work. HfO2 films are formed by depositing elemental Hf on Si(100) and then oxidizing it either in O2 or O 3. XPS results reveal that with oxidation Hf(4f) peak shifts +3.45eV with 02 and +3.65eV with O3 oxidation. LEED and AFM studies show that the initially ordered crystalline Hf becomes disordered after oxidation. The thermodynamic stability of HfO2 films on Si has been studied using a unique test-bed structure of Hf/O3/Si. Post-Oxidation of Layer Deposition (POLD) has been employed to produce HfO2 films with a desired thickness. XPS results indicate that stoichiometric HfO 2 films were successfully produced using the POLD process. The investigation of the growth and thin film properties of TiO 2 and HfO2 using oxygen and ozone has laid a foundation for the application of these metal

  6. Bonding structure and morphology of chromium oxide films grown by pulsed-DC reactive magnetron sputter deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gago, R., E-mail: rgago@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Vinnichenko, M. [Fraunhofer-Institut für Keramische Technologien und Systeme IKTS, D-01277 Dresden (Germany); Hübner, R. [Helmholtz-Zentrum Dresden – Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, 01328 Dresden (Germany); Redondo-Cubero, A. [Departamento de Física Aplicada and Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, E-28049 Madrid (Spain)

    2016-07-05

    Chromium oxide (CrO{sub x}) thin films were grown by pulsed-DC reactive magnetron sputter deposition in an Ar/O{sub 2} discharge as a function of the O{sub 2} fraction in the gas mixture (ƒ) and for substrate temperatures, T{sub s}, up to 450 °C. The samples were analysed by Rutherford backscattering spectrometry (RBS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES). On unheated substrates, by increasing ƒ the growth rate is higher and the O/Cr ratio (x) rises from ∼2 up to ∼2.5. Inversely, by increasing T{sub s} the atomic incorporation rate drops and x falls to ∼1.8. XRD shows that samples grown on unheated substrates are amorphous and that nanocrystalline Cr{sub 2}O{sub 3} (x = 1.5) is formed by increasing T{sub s}. In amorphous CrO{sub x}, XANES reveals the presence of multiple Cr environments that indicate the growth of mixed-valence oxides, with progressive promotion of hexavalent states with ƒ. XANES data also confirms the formation of single-phase nanocrystalline Cr{sub 2}O{sub 3} at elevated T{sub s}. These structural changes also reflect on the optical and morphological properties of the films. - Highlights: • XANES of CrO{sub x} thin films grown by pulsed-DC reactive magnetron sputtering. • Identification of mixed-valence amorphous CrO{sub x} oxides on unheated substrates. • Promotion of amorphous chromic acid (Cr{sup VI}) by increasing O{sub 2} partial pressure. • Production of single-phase Cr{sub 2}O{sub 3} films by increasing substrate temperature. • Correlation of bonding structure with morphological and optical properties.

  7. Optical properties and structure of HfO{sub 2} thin films grown by high pressure reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, F L [Departamento de Electronica y TecnologIa de Computadoras, Universidad Politecnica de Cartagena, Campus Universitario Muralla del Mar, E-30202 Cartagena (Spain); Toledano-Luque, M [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain); GandIa, J J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Carabe, J [Departamento de EnergIa, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Bohne, W [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Roehrich, J [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Strub, E [Hahn-Meitner-Institut Berlin, Abteilung SF4, D-14109 Berlin (Germany); Martil, I [Departamento de Fisica Aplicada III, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2007-09-07

    Thin films of hafnium oxide (HfO{sub 2}) have been grown by high pressure reactive sputtering on transparent quartz substrates (UV-grade silica) and silicon wafers. Deposition conditions were adjusted to obtain polycrystalline as well as amorphous films. Optical properties of the films deposited on the silica substrates were investigated by transmittance and reflectance spectroscopy in the ultraviolet, visible and near infrared range. A numerical analysis method that takes into account the different surface roughness of the polycrystalline and amorphous films was applied to calculate the optical constants (refractive index and absorption coefficient). Amorphous films were found to have a higher refractive index and a lower transparency than polycrystalline films. This is attributed to a higher density of the amorphous samples, which was confirmed by atomic density measurements performed by heavy-ion elastic recoil detection analysis. The absorption coefficient gave an excellent fit to the Tauc law (indirect gap), which allowed a band gap value of 5.54 eV to be obtained. The structure of the films (amorphous or polycrystalline) was found to have no significant influence on the nature of the band gap. The Tauc plots also give information about the structure of the films, because the slope of the plot (the Tauc parameter) is related to the degree of order in the bond network. The amorphous samples had a larger value of the Tauc parameter, i.e. more order than the polycrystalline samples. This is indicative of a uniform bond network with percolation of the bond chains, in contrast to the randomly oriented polycrystalline grains separated by grain boundaries.

  8. Perpendicular magnetic anisotropy of Au/FePt thin films grown on Si substrates

    CERN Document Server

    Lee, Y W; Kim, C O

    1999-01-01

    FePt thin films show in plane magnetism with a very large coercive force when they are deposited on lattice-mismatched substrates, such as glass or Si In our research, FePt alloy thin films were deposited, using the coevaporation method, on a Au buffer layer which was evaporated onto a Si substrate at 500 .deg. C. The magnetic easy axis of the FePt film changed from the in-plane direction to the normal direction of the film. Therefore, it can be said that a Au buffer layer can enhance the perpendicular magnetic anisotropy of a FePt thin film on a lattice-mismatched substrate.

  9. Preparation and properties of CdS thin films grown by ILGAR method

    Institute of Scientific and Technical Information of China (English)

    QIU Jijun; JIN Zhengguo; WU Weibing; LIU Xiaoxin; CHENG Zhijie

    2004-01-01

    CdS thin films were deposited by the ion layer gas reaction (ILGAR) method. Structural, chemical, topographical development as well as optical and electrical properties of as-deposited and annealed thin films were investigated by XRD,SEM, XPS, AFM and UV-VIS. The results showed that the thin films are uniform, compact and good in adhesion to the substrates, and the growth of the films is 2.8 nm/cycle. The evolution of structure undergoes from the cubic structure to the hexagonal one with a preferred orientation along the (002) plane after annealing at 673 K. An amount of C, O and Cl impuriries can be reduced by increasing the drying temperature or by annealing in N2 atmosphere. It was found that the band gap of the CdS films shifts to higher wavelength after annealing or increasing film thickness. The electrical resistivity decreases with increasing annealing temperature and film thickness.

  10. Optical and electrical properties of high-quality Ti2O3 epitaxial film grown on sapphire substrate

    Science.gov (United States)

    Fan, Haibo; Wang, Mingzi; Yang, Zhou; Ren, Xianpei; Yin, Mingli; Liu, Shengzhong

    2016-11-01

    Epitaxial film of Ti2O3 with high crystalline quality was grown on Al2O3 substrate by pulsed laser deposition process using a powder-pressed TiO2 target in active O2 flow. X-ray diffraction clearly reveals the (0006) crystalline Ti2O3 orientation and its (10overline{1} 0)_{{{{Ti}}_{ 2} {{O}}_{ 3} }} ||(10overline{1} 0)_{{sapphire}} in-plane epitaxial relationship with the substrate. Scanning electron microscopy images show that the film grew uniformly on the substrate with a Volmer-Weber mode. High-resolution transmission electron microscopy and selected area electron diffraction further confirm the high crystalline quality of the film. Transmittance spectrum shows that the Ti2O3 film is highly transparent in 400-800 nm with the optical band gap estimated to be 3.53 eV by Tauc plot. The temperature-dependent Hall effect measurement indicates that the Ti2O3 film appears to be n-type semiconductor with carrier concentration, mobility, and resistivity showing typical temperature-dependent behavior. The donor ionization energy was estimated to be 83.6 meV by linear relationship of conductivity versus temperature.

  11. Structural, Optical Constants and Photoluminescence of ZnO Thin Films Grown by Sol-Gel Spin Coating

    Directory of Open Access Journals (Sweden)

    Abdel-Sattar Gadallah

    2013-01-01

    Full Text Available We report manufacturing and characterization of low cost ZnO thin films grown on glass substrates by sol-gel spin coating method. For structural properties, X-ray diffraction measurements have been utilized for evaluating the dominant orientation of the thin films. For optical properties, reflectance and transmittance spectrophotometric measurements have been done in the spectral range from 350 nm to 2000 nm. The transmittance of the prepared thin films is 92.4% and 88.4%. Determination of the optical constants such as refractive index, absorption coefficient, and dielectric constant in this wavelength range has been evaluated. Further, normal dispersion of the refractive index has been analyzed in terms of single oscillator model of free carrier absorption to estimate the dispersion and oscillation energy. The lattice dielectric constant and the ratio of free carrier concentration to free carrier effective mass have been determined. Moreover, photoluminescence measurements of the thin films in the spectral range from 350 nm to 900 nm have been presented. Electrical measurements for resistivity evaluation of the films have been done. An analysis in terms of order-disorder of the material has been presented to provide more consistency in the results.

  12. Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

    Science.gov (United States)

    Hazra, D.; Tsavdaris, N.; Jebari, S.; Grimm, A.; Blanchet, F.; Mercier, F.; Blanquet, E.; Chapelier, C.; Hofheinz, M.

    2016-10-01

    Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ({T}{{c}}˜ 16.5 {{K}}) and largest gap among conventional superconductors. In its thin-film form, the T c of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin films (below 50 nm) with high T c. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel parameter ({k}{{F}}{\\ell }) ˜ 12. Accordingly we observe {T}{{c}}˜ 17.06 {{K}} (point of 50% of normal state resistance), the highest value reported so far for films of thickness 50 nm or less, indicating that HTCVD could be particularly useful for growing high quality NbN thin films.

  13. Structural properties of strained YBa2Cu3O6+x superconducting films grown by pulsed laser deposition

    Science.gov (United States)

    Ariosa, Daniel; Abrecht, M.; Pavuna, Davor; Onellion, Marshall

    2000-09-01

    In YBa2Cu3O6+x compound the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversely, the epitaxial stress, exerted by the substrate on YBCO films, modified the lattice parameters influencing the oxygen stability in the chains. The understanding of this mechanism is essential when growing epitaxial films for in- situ photoemission studies as well as for tunneling experiments, since the oxygen stability up to the top surface unit-cell is a central issue. We have studied this effect on c-axis oriented YBCO films grown by laser ablation on (001) STO single crystals. Accurate x-ray diffraction analysis of thick films (t GRT 500 angstrom) indicates the presence of two distinct layers, one strained and the other relaxed. Detailed analysis shows that the relaxed layer is as well oxidized as bulk samples, while the strained one is oxygen deficient. Furthermore, despite an oxygen content of about x equals 0.65, the strained layer is in the tetragonal phase (in bulk, the tetragonal phase exists for x < 0.3). We discuss these results in terms of competition between the chemical pressure induced by oxygen inclusion in the chains, and the uniaxial stress within the film.

  14. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    Science.gov (United States)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2017-01-01

    To study the role of novel Gd_2Zr_2O_7/Ce_{0.9}La_{0.1}O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2Cu_3O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  15. Influence of an External Magnetic Field on the Growth of Nanocrystalline Silicon Films Grown by MF Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    Junhua Gao; Lin Zhang; Jinquan Xiao; Jun Gong; Chao Sun; Lishi Wen

    2012-01-01

    The effects of an external magnetic field originating from two solenoid coils on the magnetic field configuration, plasma state of a dual unbalanced magnetron sputter system and the structure of nanocrystalline Si films were examined. Numerical simulations of the magnetic field configuration showed that increasing the coil current significantly changed the magnetic field distribution between the substrate and targets. The saturated ion current density Ji in the substrate position measured by using a circular flat probe increased from 0.18 to 0.55 mA/cm2 with the coil current ranging from 0 to 6 A. X-ray diffraction and Raman results revealed that increasing the ion density near the substrate would benefit crystallization of films and the preferential growth along [lI1] orientation. From analysis of the surface morphology and the microstructure of Si films grown under different plasma conditions, it is found that with increasing the Ji, the surface of the film was smoothed and the alteration in the surface roughness was mainly correlated to the localized surface diffusion of the deposited species and the crystallization behavior of the films.

  16. Magnetic and Optical Properties of the TiO2-Co-TiO2 Composite Films Grown by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    LIU Fa-min; DING Peng; SHI Wei-mei; WANG Tian-min

    2007-01-01

    The TiO2-Co-TiO2 sandwich films were successfully grown on glass and silicon substrata making alternate use of radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and properties of these films were identified with X-ray diffraction (XRD), Raman spectra and X-ray photoemission spectra (XPS). It is shown that the sandwich film consists of two anatase TiO2 films with an embedded Co nano-film. The fact that, when the Co nano-film thickens, varied red shifts appear in optical absorption spectra may well be explained by the quantum confinement and tunnel effects. As for magnetic properties, the saturation magnetization, remnant magnetic induction and coercivity vary with the thickness of the Co nano-films. Moreover, the Co nano-film has a critical thickness of about 8.6 nm, which makes the coercivity of the composite film reach the maximum of about 1413 Oe.

  17. The effects of thermal annealing on the structure and the electrical transport properties of ultrathin gadolinia-doped ceria films grown by pulsed laser deposition

    DEFF Research Database (Denmark)

    Rodrigo, Katarzyna Agnieszka; Heiroth, S.; Pryds, Nini;

    2011-01-01

    Ultrathin crystalline films of 10 mol% gadolinia-doped ceria (CGO10) are grown on MgO (100) substrates by pulsed laser deposition at a moderate temperature of 400°C. As-deposited CGO10 layers of approximately 4 nm, 14 nm, and 22 nm thickness consist of fine grains with dimensions ≤∼11 nm. The films...

  18. Electrical and physicochemical properties of atomic-layer-deposited HfO{sub 2} film on Si substrate with interfacial layer grown by nitric acid oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung Hyun [Department of Advanced Materials Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Seok, Tae Jun; Jin, Hyun Soo [Department of Materials Science & Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Kim, Woo-Byoung, E-mail: woo7838@dankook.ac.kr [Department of Energy Engineering, Dankook University, Cheonan 330-714 (Korea, Republic of); Park, Tae Joo, E-mail: tjp@hanyang.ac.kr [Department of Advanced Materials Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Department of Materials Science & Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of)

    2016-03-01

    Graphical abstract: - Highlights: • Ultrathin SiO{sub 2} interfacial layers grown using nitric acid oxidation and O{sub 3} oxidation were adopted at the interface of HfO{sub 2}/Si. • Higher physical density of interfacial layer grown using nitric acid oxidation resulted in the suppressed Si diffusion from substrate into the film. • The interface properties as well as permittivity of the film were improved by adoption of interfacial layer grown using nitric acid oxidation. - Abstract: The ultrathin SiO{sub 2} interfacial layer (IL) was adopted at the interface between atomic-layer-deposited HfO{sub 2} gate dielectric film and a Si substrate, which was grown using nitric acid oxidation (NAO) and O{sub 3} oxidation (OZO) prior to HfO{sub 2} film deposition. X-ray photoelectron spectroscopy result revealed that Si diffusion from the substrate into the film was suppressed for the film with NAO compared to that with OZO, which was attributed to the higher physical density of IL. The electrical measurement using metal–insulator–semiconductor devices showed that the film with NAO exhibited higher effective permittivity and lower densities of fixed charge and slow state at the interface. Furthermore, the leakage current density at an equivalent electrical thickness was lower for the film with NAO than OZO.

  19. Cw and time-resolved spectroscopy in homoepitaxial GaN films and GaN-GaAlN quantum wells grown by molecular beam epitaxy.

    OpenAIRE

    Taliercio, Thierry; Gallart, Mathieu; Lefebvre, Pierre; Morel, Aurélien; Gil, Bernard; Allègre, Jacques; Grandjean, Nicolas; Massies, Jean; Grzegory, Izabella; Porowsky, Sylvester

    2001-01-01

    International audience; We have grown GaN films and GaN–AlGaN quantum wells (QWs) on homoepitaxial substrates, by molecular beam epitaxy using ammonia. Both the GaN film and the QW are found to have superior excitonic recombination properties which are extremely promising for the development of indium free ultra-violet lasers based on nitrides.

  20. Optical, structural, and electrical properties of Mg2NiH4 thin films in situ grown by activated reactive evaporation

    NARCIS (Netherlands)

    Westerwaal, R. J.; Slaman, M.; Broedersz, C. P.; Borsa, D. M.; Dam, B.; Griessen, R.; Borgschulte, A.; Lohstroh, W.; Kooi, B.; ten Brink, Gert; Tschersich, K. G.; Fleischhauer, H. P.

    2006-01-01

    Mg2NiH4 thin films have been prepared by activated reactive evaporation in a molecular beam epitaxy system equipped with an atomic hydrogen source. The optical reflection spectra and the resistivity of the films are measured in situ during deposition. In situ grown Mg2NiH4 appears to be stable in

  1. Microstructural and conductivity comparison of Ag films grown on amorphous TiO2 and polycrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Dannenberg, Rand; Stach, Eric; Glenn, Darin; Sieck, Peter; Hukari, Kyle

    2001-03-26

    8 nm thick Ag films were sputter deposited onto amorphous TiO{sub 2} underlayers 25 nm thick, and also amorphous TiO{sub 2} (25 nm)/ZnO (5 nm) multiunderlayers. The substrates were back-etched Si with a 50 nm thick LPCVD Si{sub 3}N{sub 4} electron transparent membrane. The ZnO, sputtered onto amorphous TiO{sub 2}, formed a continuous layer with a grain size of 5 nm in diameter, on the order of the film thickness. There are several microstructural differences in the Ag dependent on the underlayers, revealed by TEM. First a strong {l_brace}0001{r_brace} ZnO to {l_brace}111{r_brace} Ag fibre-texture relationship exists. On TiO{sub 2} the Ag microstructure shows many abnormal grains whose average diameter is about 60-80 nm, whereas the films on ZnO show few abnormal grains. The background matrix of normal grains on the TiO{sub 2} is roughly 15 nm, while the normal grain size on the ZnO is about 25 nm. Electron diffraction patterns show that the film on ZnO has a strong {l_brace}111{r_brace} orientation, and dark field images with this diffraction condition have a grain size of about 30 nm. In a region near the center of the TEM grid where there is the greatest local heating during deposition, Ag films grown on amorphous TiO{sub 2} are discontinuous, whereas on ZnO, the film is continuous. When films 8 nm films are grown on solid glass substrates, those with ZnO underlayers have sheet resistances of 5.68 {Omega}/, whereas those on TiO{sub 2} are 7.56 {Omega}/, and when 16 nm thick, the corresponding sheet resistances are 2.7 {Omega}/ and 3.3 {Omega}/. The conductivity difference is very repeatable. The improved conductivity is thought to be a combined effect of reduced grain boundary area per unit volume, the predominance of low grain boundary resistivity Coincidence Site Lattice boundaries from the Ag {l_brace}111{r_brace} orientation, and Ag planarization on ZnO resulting in less groove formation on deposition, concluded from atomic force microscopy.

  2. Highly stable thin film transistors using multilayer channel structure

    KAUST Repository

    Nayak, Pradipta K.

    2015-03-09

    We report highly stable gate-bias stress performance of thin film transistors (TFTs) using zinc oxide (ZnO)/hafnium oxide (HfO2) multilayer structure as the channel layer. Positive and negative gate-bias stress stability of the TFTs was measured at room temperature and at 60°C. A tremendous improvement in gate-bias stress stability was obtained in case of the TFT with multiple layers of ZnO embedded between HfO2 layers compared to the TFT with a single layer of ZnO as the semiconductor. The ultra-thin HfO2 layers act as passivation layers, which prevent the adsorption of oxygen and water molecules in the ZnO layer and hence significantly improve the gate-bias stress stability of ZnO TFTs.

  3. High-quality β-Ga2O3 single crystals grown by edge-defined film-fed growth

    Science.gov (United States)

    Kuramata, Akito; Koshi, Kimiyoshi; Watanabe, Shinya; Yamaoka, Yu; Masui, Takekazu; Yamakoshi, Shigenobu

    2016-12-01

    β-Ga2O3 bulk crystals were grown by the edge-defined film-fed growth (EFG) process and the floating zone process. Semiconductor substrates containing no twin boundaries with sizes up to 4 in. in diameter were fabricated. It was found that Si was the main residual impurity in the EFG-grown crystals and that the effective donor concentration (N d - N a) of unintentionally doped crystals was governed by the Si concentration. Intentional n-type doping was shown to be possible. An etch pit observation revealed that the dislocation density was on the order of 103 cm-3. N d - N a for the samples annealed in nitrogen ambient was almost the same as the Si concentration, while for the samples annealed in oxygen ambient, it was around 1 × 1017 cm-3 and independent of the Si concentration.

  4. Nanostructured and wide bandgap CdS:O thin films grown by reactive RF sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M. A.; Rahman, K. S.; Haque, F.; Rashid, M. J.; Akhtaruzzaman, M.; Sopian, K.; Sulaiman, Y. [Solar Energy Research Institute (SERI), National University of Malaysia, 43600 Bangi (Malaysia); Amin, N. [Solar Energy Research Institute (SERI), National University of Malaysia, 43600 Bangi (Malaysia); Department of Electrical, Electronic and System Engineering, Faculty of Engineering and Built Environment, National University of Malaysia, 43600 Bangi (Malaysia)

    2015-05-15

    In this study, CdS:O thin films were prepared from a 99.999% CdS target by reactive sputtering in a Ar:O{sub 2} (99:1) ambient with different RF power at room temperature. The deposited films were studied by means of XRD, SEM, EDX, Hall Effect and UV-Vis spectrometry. The incorporations of O{sub 2} into the films were observed to increase with the decrease of deposition power. The cryatallinity of the films were reduced, whereas the band gaps of the films were increased by the increase of O{sub 2} content on the films. The films were found in nano-structured grains with a compact surface. It has been seen that the highest carrier density is observed in the film with O{sub 2} at.% 21.10, while the values decreased with the further increase or decrease of O{sub 2} content on the films; indicating that specific amount of donor like O{sub 2} atoms substitute to the S atoms can improve the carrier density of the CdS:O thin film.

  5. Nanostructured and amorphous-like tungsten films grown by pulsed laser deposition

    Science.gov (United States)

    Dellasega, D.; Merlo, G.; Conti, C.; Bottani, C. E.; Passoni, M.

    2012-10-01

    An experimental investigation of nanostructured, micrometer-thick, tungsten films deposited by pulsed laser deposition is presented. The films are compact and pore-free, with crystal grain sizes ranging from 14 nm to less than 2 nm. It is shown how, by properly tailoring deposition rate and kinetic energy of ablated species, it is possible to achieve a detailed and separate control of both film morphology and structure. The role of the main process parameters, He background pressure, laser fluence, and energy, is elucidated. In contrast with W films produced with other PVD techniques, β-phase growth is avoided and the presence of impurities and contaminants, like oxygen, is not correlated with film structure. These features make these films interesting for the development of coatings with improved properties, like increased corrosion resistance and enhanced diffusion barriers.

  6. High Resistive ZnO/Diamond/Si Films Grown via Metal-organic Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    YANG Hong-jun; ZHAO Bai-jun; FANG Xiu-jun; DU Guo-tong; LIU Da-li; GAO Chun-xiao; LIU Xi-zhe

    2005-01-01

    Piezoelectric ZnO layers with high resistivity for surface acoustic wave applications were prepared on polycrystalline diamond/Si substrates with (111) orientation via metal-organic chemical vapour deposition.The characteristics of the films were optimized through different growth methods. The comparative study of the X-ray diffraction spectra and scanning electron microscopic images showed that the final-prepared ZnO films were dominantly c-axis oriented. Zn and O elements in the final prepared ZnO films were investigated through X-ray photoelectron spectroscopy. According to the statistical results, the n(Zn)/n(O) ratio is near 1. The Raman scattering was also performed in back scattering configuration. E2 mode was observed for the final films, which indicated that the better quality ZnO films had been obtained. The resistivity of the films was also enhanced via the modification of the growth methods.

  7. Structural and Optical Properties of CdS Thin Film Grown by Chemical Bath Deposition

    Directory of Open Access Journals (Sweden)

    S. Rajpal

    2013-07-01

    Full Text Available In this work we report synthesis and optical characterization of CdS thin films coated on glass substrate. The films were deposited using chemical bath deposition method. Scanning Electron microscopy shows a uniform film of CdS film at particular concentration and dipping time. The Energy Dispersive spectroscopy reveals the presence of Cd and S in the CdS film. X-Ray diffraction confirms the cubic structure of CdS deposited on glass and amorphous nature of glass. Optical and photoluminescence studies were done using UV-Visible spectroscopy and Photoluminescence spectroscopy respectively. We have determined bandgap by analyzing UV-Visible spectra results. Wettability studies were done using Optical Contact Angle, which confirms the hydrophobic nature of the CdS films.

  8. Ferroelectric-field-effect-enhanced resistance performance of TiN/Si:HfO2/oxygen-deficient HfO2/TiN resistive switching memory cells

    Science.gov (United States)

    Jiang, Ran; Wu, Zhengran; Du, Xianghao; Han, Zuyin; Sun, Weideng

    2015-07-01

    Greatly improved resistance performance, including high resistance ratio between the high resistance state and the low resistance state, long-time retention, and reliable endurance, was observed in TiN/Si:HfO2/oxygen-deficient HfO2/TiN memory cells. The enhanced resistance ratio is ascribed to the creation/elimination of an extra barrier in oxygen-deficient HfO2 layer in response to the polarization reversal in the ferroelectric Si:HfO2 layer. Along with the enhanced resistance ratio, the long retention and good endurance make the proposed device a promising candidate for non-volatile resistive memories.

  9. Preferential orientation of ferroelectric calcium modified lead titanate thin films grown on various substrates

    OpenAIRE

    Ricote, J.; Calzada, M L; Mendiola, J; Chateigner, D.

    2002-01-01

    [EN] Among all the factors that determine the development of preferential orientation or texture in polycrystalline thin films, the most important is the nature of the substrate. A preferential orientation of the crystallites with the polar axis perpendicular to the film surface results in an important improvement of the ferroelectric behaviour. In the search for the substrate that produces highly oriented ferroelectric thin films, this work analyses by quantitative texture analysis ...

  10. Fractal features of CdTe thin films grown by RF magnetron sputtering

    Science.gov (United States)

    Hosseinpanahi, Fayegh; Raoufi, Davood; Ranjbarghanei, Khadijeh; Karimi, Bayan; Babaei, Reza; Hasani, Ebrahim

    2015-12-01

    Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

  11. Characterization of ZnO:Si nanocomposite films grown by thermal evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Shabnam; Kant, Chhaya Ravi [Department of Applied Sciences, Indira Gandhi Institute of Technology, Guru Gobind Singh Indraprastha University, Delhi 110 006 (India); Arun, P. [Department of Physics and Electronics, S.G.T.B. Khalsa College, University of Delhi, Delhi-110 007 (India)], E-mail: arunp92@physics.du.ac.in; Mehra, N.C. [University Science Instrumentation Centre, University of Delhi, Delhi 110 007 (India)

    2008-11-24

    Composite films were fabricated by co-evaporating Zinc Oxide with Silicon at room temperatures. The resulting films had polycrystalline grains of Zinc Oxide whose grain size were few hundred nanometers, embedded in the silicon matrix. These nanocrystalline grains of ZnO showed good photoluminescence emission at 520 nm along with a photoluminescence emission at 620 nm being contributed by the silicon background. Thus, the nanocomposite films gave a board emission, making it a potentially useful candidate for optoelectronic devices. The photo-luminescent property of the films was found to be stable since the homgenously dispersed ZnO nanocrystals were not allowed to agglomerate by the silicon background.

  12. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Science.gov (United States)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-05-01

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  13. Structural and electrical properties of ultrathin niobium nitride films grown by atomic layer deposition

    Science.gov (United States)

    Linzen, S.; Ziegler, M.; Astafiev, O. V.; Schmelz, M.; Hübner, U.; Diegel, M.; Il'ichev, E.; Meyer, H.-G.

    2017-03-01

    We studied and optimised the properties of ultrathin superconducting niobium nitride films fabricated with a plasma-enhanced atomic layer deposition (PEALD) process. By adjusting process parameters, the chemical embedding of undesired oxygen into the films was minimised and a film structure consisting of mainly polycrystalline niobium nitride with a small fraction of amorphous niobium oxide and niobium oxo-nitrides were formed. For this composition a critical temperature of 13.8 K and critical current densities of 7 × 106 A cm-2 at 4.2 K were measured on 40 nm thick films. A fundamental correlation between these superconducting properties and the crystal lattice size of the cubic δ-niobium-nitride grains were found. Moreover, the film thickness variation between 40 and 2 nm exhibits a pronounced change of the electrical conductivity at room temperature and reveals a superconductor-insulator-transition in the vicinity of 3 nm film thickness at low temperatures. The thicker films with resistances up to 5 kΩ per square in the normal state turn to the superconducting one at low temperatures. The perfect thickness control and film homogeneity of the PEALD growth make such films extremely promising candidates for developing novel devices on the coherent quantum phase slip effect.

  14. Upper critical field of as-grown MgB{sub 2} thin films by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y. [Department of Material Science and Engineering, Iwate University, Iwate Industrial Promotion Center, Iioka shinden 3-35-2, Morioka 020-0852 (Japan)]. E-mail: yharada@luck.ocn.ne.jp; Udsuka, M. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Takahashi, T. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan)

    2005-04-30

    Superconducting thin films of magnesium diboride (MgB{sub 2}) were prepared on MgO(001) substrate by molecular beam epitaxy in the co-evaporation conditions of low deposition rate and ultra-high vacuum. A superconducting transition with the onset temperature of 31.2K was confirmed by both transport and magnetization measurements. The upper critical fields are obtained from measurement of the field dependence of the resistivity. It was estimated that the upper critical field at 0K was more than 15T. The upper critical field anisotropy ratio, H{sub C2,ab}(0)/H{sub C2,c}(0), was estimated to be 1.78 from the magnetic field-temperature phase diagram for as-grown MgB{sub 2} thin films.

  15. Nucleation and Growth of MOCVD Grown (Cr, Zn)O Films – Uniform Doping vs. Secondary Phase Formation

    Energy Technology Data Exchange (ETDEWEB)

    Saraf, Laxmikant V.; Engelhard, Mark H.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Wang, Chong M.; Heald, Steve M.; McCready, David E.; Lea, Alan S.; Baer, Donald R.; Chambers, Scott A.

    2007-01-17

    We report a detailed study of chromium solubility and secondary phase formation in MOCVD grown (Cr, Zn)O-based films on silicon (100). Simultaneous deposition of 0.15M Cr(TMHD) and 0.025M Zn(TMHD) based precursors in an oxidizing environment with a flow ratio of 1:10 resulted in secondary phase formation rather than uniform Cr doping. Based on several surface and micro-structural techniques, we have identified nano-crystalline ZnCr2O4 and disordered Cr2O3 as the secondary Cr-containing phases that nucleate. Analysis suggests that ZnCr2O4 crystallites are dispersed throughout the film and that disordered Cr2O3 layer may form at the interface. These results reveal a strong tendency for Cr to exist in octahedral, rather than tetrahedral coordination.

  16. Magnetic anisotropy of crystalline Fe films grown on (001 GaAs substrates using Ge buffer layers

    Directory of Open Access Journals (Sweden)

    Seul-Ki Bac

    2016-05-01

    Full Text Available Magnetic anisotropy of Fe films grown on (001 GaAs substrates using Ge buffer layers were investigated by planar Hall effect measurements. In addition to phenomena arising from dominant cubic symmetry of the Fe specimen, the study of angular dependence of magnetization reversal revealed breaking of this symmetry in the form of systematic asymmetric shifts of magnetic hysteresis loops around the crystallographic directions. We ascribe such symmetry breaking to an admixture of uniaxial anisotropy associated with the [100] direction in the Fe film. To determine the parameters associated with this uniaxial anisotropy, we quantitatively analyze the asymmetric shifts of the hysteresis loop centers from the directions. Even though the value of these parameters turns out to be relatively small compared to that of the cubic anisotropy (by about two orders of magnitude, they survive up to room temperature.

  17. Magnetic anisotropy of crystalline Fe films grown on (001) GaAs substrates using Ge buffer layers

    Science.gov (United States)

    Bac, Seul-Ki; Lee, Hakjoon; Lee, Sangyeop; Choi, Seonghoon; Yoo, Taehee; Lee, Sanghoon; Liu, X.; Furdyna, J. K.

    2016-05-01

    Magnetic anisotropy of Fe films grown on (001) GaAs substrates using Ge buffer layers were investigated by planar Hall effect measurements. In addition to phenomena arising from dominant cubic symmetry of the Fe specimen, the study of angular dependence of magnetization reversal revealed breaking of this symmetry in the form of systematic asymmetric shifts of magnetic hysteresis loops around the crystallographic directions. We ascribe such symmetry breaking to an admixture of uniaxial anisotropy associated with the [100] direction in the Fe film. To determine the parameters associated with this uniaxial anisotropy, we quantitatively analyze the asymmetric shifts of the hysteresis loop centers from the directions. Even though the value of these parameters turns out to be relatively small compared to that of the cubic anisotropy (by about two orders of magnitude), they survive up to room temperature.

  18. Compositional dependence of Raman scattering and photoluminescence emission in Cu-Ga-Se films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Grossberg, M., E-mail: mgross@staff.ttu.e [Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Krustok, J. [Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Siebentritt, S. [Universite du Luxembourg, 162a avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Albert, J. [Helmholtz Centre Berlin, Glienicker Strasse 100, 14109 Berlin (Germany)

    2009-07-01

    This paper presents Raman scattering and photoluminescence (PL) analysis of polycrystalline Cu-Ga-Se films grown epitaxially on the GaAs substrate. In the compositional dependence of the Raman spectra of the CuGaSe{sub 2} films, the appearance of the ordered vacancy compounds (OVCs) CuGa{sub 3}Se{sub 5} and CuGa{sub 5}Se{sub 8} was observed. The dominating A{sub 1} Raman modes were detected at 185, 166 and 159 cm{sup -1}, respectively. The PL bands of CuGaSe{sub 2}, CuGa{sub 3}Se{sub 5} and CuGa{sub 5}Se{sub 8} at T=10 K were detected at 1.615, 1.72 and 1.76 eV, respectively. The dominating PL emission channel is the band-to-tail (BT) type recombination.

  19. Crystallographic and electronic contribution to the apparent step height in nanometer-thin Pb(111) films grown on Cu(111)

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, Fabian; Parga, Amadeo L Vazquez de; Anglada, Eduardo; Hinarejos, Juan Jose; Miranda, Rodolfo; Yndurain, Felix [Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid (Spain)], E-mail: al.vazquezdeparga@uam.es

    2009-12-15

    Thermal roughening of Pb(111) films grown on Cu(111) produces three-dimensional (3D) islands of different number of layers allowing the simultaneous and direct measurement by scanning tunneling microscopy (STM) of the step height for different thicknesses in real space. The apparent step heights separating adjacent layers show several oscillations with amplitudes of up to 0.8-1.4 A around the bulk interlayer distance as a function of film thickness. The oscillations have bilayer periodicity with a superimposed longer beating period that produces a phase slip every eight layers. Based on first-principles calculations of Pb(111) free standing slabs, we can identify the relevant electronic states responsible for these quantum size effects. In addition, we can distinguish between geometric and electronic contributions to the apparent step heights measured on the STM images.

  20. Effect of deposition conditions on the growth rate and electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Roro, K.T.; Botha, J.R.; Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2008-07-01

    ZnO thin films have been grown on glass substrates by MOCVD. The effect of deposition conditions such as VI/II molar ratio, DEZn flow rate and total reactor pressure on the growth rate and electrical properties of the films was studied. It is found that the growth rate decreases with an increase in the VI/II molar ratio. This behaviour is ascribed to the competitive adsorption of reactant species on the growth surface. The growth rate increases with an increase in DEZn flow rate, as expected. It is shown that the carrier concentration is independent of the DEZn flow rate. An increase in the total reactor pressure yields a decrease in growth rate. This phenomenon is attributed to the depletion of the gas phase due to parasitic prereactions between zinc and oxygen species at high pressure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Impact of low temperature annealing on structural, optical, electrical and morphological properties of ZnO thin films grown by RF sputtering for photovoltaic applications

    Science.gov (United States)

    Purohit, Anuradha; Chander, S.; Sharma, Anshu; Nehra, S. P.; Dhaka, M. S.

    2015-11-01

    This paper presents effect of low temperature annealing on the physical properties of ZnO thin films for photovoltaic applications. The thin films of thickness 50 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing radio frequency magnetron sputtering technique followed by thermal annealing within low temperature range 150-450 °C. These as-grown and annealed films were subjected to the X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) for structural, optical, electrical and surface morphological analysis respectively. The compositional analysis of the as-grown ZnO film was also carried out using energy dispersive spectroscopy (EDS). The XRD patterns reveal that the films have wurtzite structure of hexagonal phase with preferred orientation (1 0 0) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in detail. The optical band gap was found in the range 3.30-3.52 eV and observed to decrease with annealing temperature except 150 °C. The current-voltage characteristics show that the films exhibit approximately ohmic behavior. The SEM studies show that the films are uniform, homogeneous and free from crystal defects and voids. The experimental results reveal that ZnO thin films may be used as alternative materials for eco-friendly buffer layer to the thin film solar cell applications.

  2. Atomic layer deposition of nanolaminate oxide films on Si

    Science.gov (United States)

    Tallarida, M.; Weisheit, M.; Kolanek, K.; Michling, M.; Engelmann, H. J.; Schmeisser, D.

    2011-11-01

    Among the methods for depositing thin films, atomic layer deposition is unique for its capability of growing conformal thin films of compounds with a control of composition and thickness at the atomic level. The conformal growth of thin films can be of particular interest for covering nanostructures since it assures the homogeneous growth of the ALD film in all directions, independent of the position of the sample with respect to the incoming precursor flow. Here we describe the technique for growing the HfO2/Al2O3 bilayer on Si substrate and our in situ approach for its investigation by means of synchrotron radiation photoemission. In particular, we study the interface interactions between the two oxides for various thickness compositions ranging from 0.4 to 2.7 nm. We find that the ALD of HfO2 on Si induces the increase of the interfacial SiO2 layer, and a change in the band bending of Si. On the contrary, the ALD of Al2O3 on HfO2 shows negligible interaction between layers as the binding energies of Hf4f, Si2p, and O1s core level peaks and the valence band maximum of HfO2 do not change and the interfacial SiO2 does not increase.

  3. Thin films of copper oxide and copper grown by atomic layer deposition for applications in metallization systems of microelectronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Waechtler, Thomas

    2010-05-25

    Copper-based multi-level metallization systems in today's ultralarge-scale integrated electronic circuits require the fabrication of diffusion barriers and conductive seed layers for the electrochemical metal deposition. Such films of only several nanometers in thickness have to be deposited void-free and conformal in patterned dielectrics. The envisaged further reduction of the geometric dimensions of the interconnect system calls for coating techniques that circumvent the drawbacks of the well-established physical vapor deposition. The atomic layer deposition method (ALD) allows depositing films on the nanometer scale conformally both on three-dimensional objects as well as on large-area substrates. The present work therefore is concerned with the development of an ALD process to grow copper oxide films based on the metal-organic precursor bis(trin- butylphosphane)copper(I)acetylacetonate [({sup n}Bu{sub 3}P){sub 2}Cu(acac)]. This liquid, non-fluorinated {beta}-diketonate is brought to react with a mixture of water vapor and oxygen at temperatures from 100 to 160 C. Typical ALD-like growth behavior arises between 100 and 130 C, depending on the respective substrate used. On tantalum nitride and silicon dioxide substrates, smooth films and selfsaturating film growth, typical for ALD, are obtained. On ruthenium substrates, positive deposition results are obtained as well. However, a considerable intermixing of the ALD copper oxide with the underlying films takes place. Tantalum substrates lead to a fast self-decomposition of the copper precursor. As a consequence, isolated nuclei or larger particles are always obtained together with continuous films. The copper oxide films grown by ALD can be reduced to copper by vapor-phase processes. If formic acid is used as the reducing agent, these processes can already be carried out at similar temperatures as the ALD, so that agglomeration of the films is largely avoided. Also for an integration with subsequent

  4. Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

    Science.gov (United States)

    Sankaran, K. J.; Huang, B. R.; Saravanan, A.; Tai, N. H.; Lin, I. N.

    2014-10-01

    Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH4 and Ar under different negative bias voltages ranging from -50 to -200 V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under -200 V, the electron field emission (EFE) process can be turned on at a field as small as 4.08 V/μm, attaining a EFE current density as large as 3.19 mA/cm2 at an applied field of 8.64 V/μm. But the films grown without bias (0 V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH4/Ar plasma due to large applied bias voltage of -200 V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

  5. Depth dependent properties of ITO thin films grown by pulsed DC sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sytchkova, A., E-mail: anna.sytchkova@enea.it [ENEA Optical Coatings Laboratory, via Anguillarese 301, 00123 Rome (Italy); Zola, D. [ENEA Optical Coatings Laboratory, via Anguillarese 301, 00123 Rome (Italy); Bailey, L.R.; Mackenzie, B.; Proudfoot, G. [Oxford Instruments Plasma Technology, Yatton, Bristol, BS49 4AP (United Kingdom); Tian, M. [NT-MDT Europe BV, High Tech Campus 83, 5656 AG Eindhoven (Netherlands); Ulyashin, A. [SINTEF Materials and Chemistry, Forskningsveien 1, P.O. 124 Blindern, NO-0314 Oslo (Norway)

    2013-05-15

    A systematically prepared set of ITO layers for solar cell applications has been analyzed by spectroscopic variable angle ellipsometry in order to trace the dependence of free carriers’ distribution along the film depth as a function of film thickness as well as its change upon annealing. Samples were deposited on silicon substrates with various thicknesses in steps of approximately 10–20 nm. This set was duplicated and these samples were annealed, so that for each thickness an as-deposited and an annealed sample is available. Conventionally measured electrical conductivity and morphological properties (AFM measurements) of the films have been compared with the optical constants’ inhomogeneity, i.e. material properties along the film thickness modelled by variable-angle spectroscopic ellipsometry. The obtained results show that the optical as well as electrical properties of thin ITO films prepared by pulsed DC sputtering are depth dependent. For the deposition conditions used a well-determined reproducible non-uniform distribution of free carriers within the film thickness was determined. In particular it has been found that the majority of free carriers in as-deposited ultra-thin ITO films is concentrated at sample half-depth, while their distribution becomes asymmetric for the thicker films, with a maximum located at approximately 40 nm depth. The distribution of free carriers in annealed samples is qualitatively different from that of as-deposited layers.

  6. Raman scattering of polycrystalline GaSb thin films grown by the co-evaporation process

    Institute of Scientific and Technical Information of China (English)

    Qiao Zai-Xiang; Sun Yun; He Wei-Yu; Liu Wei; He Qing; Li Chang-Jian

    2009-01-01

    This paper reports that GaSb thin films have been co-deposited on soda-lime glass substrates. The GaSb thin film structural properties are characterized by Raman spectroscopy. The Sb-A1g/GaSb-TO ratio decreases rapidly with the increase of substrate temperature, which suggests a small amount of crystalline Sb in the GaSb thin film and suggests that Sb atoms in the thin film decrease. In Raman spectra, the transverse optical (TO) mode intensity is stronger than that of the longitudinal optical (LO) mode, which indicates that all the samples arc disordered. The LO/TO intensity ratio increases with increasing substrate temperature which suggests the improved polycrystalline quality of the GaSb thin film. A downshift of the TO and LO frequencies of the polycrystalline GaSb thin film to single crystalline bulk GaSb Raman spectra is also observed. The uniaxial stress in GaSb thin film is calculated and the value is around 1.0 Gpa. The uniaxial stress decreases with increasing substrate temperature. These results suggest that a higher substrate temperature is beneficial in relaxing the stress in GaSb thin film.

  7. Investigation of nanostructured transparent conductive films grown by rotational-sequential-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jong-Hong, E-mail: jonghonglu@mail.mcut.edu.tw; Chen, Bo-Ying; Wang, Chih-Hsuan [Department of Materials Engineering, Ming Chi University of Technology, 84 Gungjuan Rd., Taishan Dist. New Taipei City 24301, Taiwan and Center for Thin Film Technologies and Applications, Ming Chi University of Technology, 84 Gungjuan Rd., Taishan Dist. New Taipei City 24301, Taiwan (China)

    2014-03-15

    This study fabricates three types of nanostructured conductive transparent films using a rotational-sequential-sputtering method. These films include (1) TiO{sub 2}/indium-tin oxide (ITO) and SiO{sub x}/ITO nanomultilayer films, the optical refractive indices of which can be manipulated in the range of 2.42–1.63 at a wavelength of 550 nm with a controlled resistivity range of 1 × 10{sup −3} to 2 × 10{sup −4} Ω·cm. (2) Multilayer ITO films are deposited on polyethylene terephthalate substrates, providing good flexibility and resistivity as low as 5 × 10{sup −4} Ω·cm. Finally, (3) ultrathin ITO films ranging from subnanometer to a few nanometers in thickness enable exploration of ITO film growth and thermal stability. X-ray reflection characterization provides a rapid, non-destructive method to measure the single-layer thicknesses of the nanomultilayer films and ultrathin ITO films at subnanoscale resolution.

  8. Optical parameters of Al-doped ZnO nanorod array thin films grown via the hydrothermal method.

    Science.gov (United States)

    Kim, Soaram; Kim, Min Su; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Leem, Jae-Young

    2013-09-01

    ZnO seed layers were deposited onto a quartz substrate using the sol--gel method, and Al-doped ZnO (AZO) nanorod array thin films with different Al concentrations that ranged from 0 to 2.0 at. % were grown on the ZnO seed layers via the hydrothermal method. Optical parameters, including the optical band gap, the absorption coefficient, the Urbach energy, the refractive index, the dispersion parameter, and the optical conductivity, were studied to investigate the effects of Al doping on the optical properties of AZO nanorod array thin films. The optical band gaps of the ZnO and AZO nanorod array thin films were 3.206 at 0 at.%, 3.214 at 0.5 at.%, 3.226 at 1.5 at.%, and 3.268 at 2.0 at.%. The Urbach energy gradually decreased from 126 meV (0 at.%) to 70 meV (2.0 at.%) as the Al concentration was increased. The dispersion energy, the single-oscillator energy, the average oscillator wavelength, the average oscillator strength, the refractive index, and the optical conductivity of the AZO nanorod array thin films were all affected by Al doping.

  9. Surfactant controlled switching of water-in-oil wetting behaviour of porous silica films grown at oil-water interfaces

    Indian Academy of Sciences (India)

    Manish M Kulkarni; Rajdip Bandyopadhyaya; Ashutosh Sharma

    2008-11-01

    Selective permeation of oil and water across a porous medium, as in oil recovery operations, depends on the preferential wetting properties of the porous medium. We show a profound influence of surfactants in wetting of porous media and thus demonstrate a new route for the control of water-in-oil wetting of porous substrates by changing the concentration of surfactants in an aqueous sub-phase below the substrate. This strategy is employed to engineer partial reversible wetting transitions on a porous silica film. The film itself is grown and stabilized on a flat, macroscopic interface between an oil phase and an aqueous sub-phase. On increasing the surfactant (CTAB) concentration in the sub-phase, contact angle of a water drop (placed on the oil side of the film) changes from 140° to 16° in 25 min by diffusion of the surfactant across the porous film. On further replacement of the sub-phase with pure water, diffusion of the surfactant from the water drop back to the sub-phase was slower, increasing the contact angle in the process from 16° to 90° in 2 h. Wettability control by a cationic surfactant (CTAB) was found to be much faster (6 deg/min) than that offered by an anionic surfactant, SDS (0.05 deg/min). Switching of the surface wettability due to the surfactant diffusion may have implications in oil-water separation, chemical bed reactors and microfluidic devices.

  10. Structure analysis of Ni thin films epitaxially grown on bcc metal underlayers formed on MgO(100 substrates

    Directory of Open Access Journals (Sweden)

    Futamoto Masaaki

    2013-01-01

    Full Text Available Ni thin films are prepared on Cr, V, and Nb underlayers with bcc structure formed on MgO(100 single-crystal substrates by molecular beam epitaxy. The growth behavior and the crystallographic properties are investigated by in-situ reflection high-energy electron diffraction and pole-figure X-ray diffraction. Cr(100 and V(100 single-crystal underlayers grow epitaxially on the substrates, whereas an Nb epitaxial_underlayer consisting of two bcc(110 variants is formed on the MgO(100 substrate. Metastable crystals nucleate on the Cr and the V underlayers, where the metastable hcp structure is stabilized through heteroepitaxial growth. With increasing the film thickness, the hcp structure starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001 close-packed plane. The resulting films are consisting of mixtures of hcp and fcc crystals. On the other hand, only the formation of fcc crystal is recognized for the Ni film grown on Nb(110 underlayer.

  11. Epitaxial LaFeAsO{sub 1-x}F{sub x} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kidszun, M; Haindl, S; Reich, E; Haenisch, J; Iida, K; Schultz, L; Holzapfel, B, E-mail: M.Kidszun@ifw-dresden.d [IFW Dresden, Institute for Metallic Materials, PO Box 270116, D-01171 Dresden (Germany)

    2010-02-15

    Superconducting and epitaxially grown LaFeAsO{sub 1-x}F{sub x} thin films were successfully prepared on (001)-oriented LaAlO{sub 3} substrates using pulsed laser deposition. The prepared thin films show exclusively a single in-plane orientation with the epitaxial relation (001)[100]||(001)[100] and a full width at half-maximum value of 1{sup 0}. Furthermore, resistive measurement of the superconducting transition temperature revealed a T{sub c,90%} of 25 K with a high residual resistive ratio of 6.8. The preparation technique applied, standard thin film pulsed laser deposition at room temperature in combination with a subsequent post-annealing process, is suitable for fabrication of high quality LaFeAsO{sub 1-x}F{sub x} thin films. A high upper critical field of 76.2 T was evaluated for magnetic fields applied perpendicular to the c-axis and the anisotropy was calculated to be 3.3 assuming single band superconductivity. (rapid communication)

  12. Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method

    Directory of Open Access Journals (Sweden)

    Yang Tieying

    2011-01-01

    Full Text Available Abstract Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD and hydride vapor-phase epitaxy (HVPE in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD, micro-Raman spectra, and scanning electron microscopy (SEM. Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.

  13. Study of structural and optical properties of ZnO films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lemlikchi, S., E-mail: lemlikchi_safo@yahoo.fr [Advanced Technology Development Centre, Cite 20 Aout 1956 BP 17 Baba Hassen, Algiers (Algeria); Abdelli-Messaci, S.; Lafane, S.; Kerdja, T. [Advanced Technology Development Centre, Cite 20 Aout 1956 BP 17 Baba Hassen, Algiers (Algeria); Guittoum, A.; Saad, M. [Nuclear Research Centre of Algiers, 2 Bd Frantz-Fanon, Algiers (Algeria)

    2010-07-01

    Wurtzite zinc oxides films (ZnO) were deposited on silicon (0 0 1) and corning glass substrates using the pulsed laser deposition technique. The laser fluence, target-substrate distance, substrate temperature of 300 deg. C were fixed while varying oxygen pressures from 2 to 500 Pa were used. It is observed that the structural properties of ZnO films depend strongly on the oxygen pressure and the substrate nature. The film crystallinity improves with decreasing oxygen pressure. At high oxygen pressure, the films are randomly oriented, whereas, at low oxygen pressures they are well oriented along [0 0 1] axis for Si substrates and along [1 0 3] axis for glass substrates. A honeycomb structure is obtained at low oxygen pressures, whereas microcrystalline structures were obtained at high oxygen pressures. The effect of oxygen pressure on film transparency, band gap E{sub g} and Urbach energies was investigated.

  14. ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy

    Energy Technology Data Exchange (ETDEWEB)

    Valente, Anne-Marie [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Eremeev, Grigory V. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Spradlin, Joshua K. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Phillips, H. Lawrence [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Cao, C. [Illinois Inst. of Technology, Chicago, IL (United States); Proslier, Thomas [Argonne National Laboratory, Argonne, IL (United States); Tao, T. [Univ. of Illinois at Chicago, Chicago, IL (United States)

    2014-02-01

    In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favourable template for growing the final surface exposed to SRF fields. The influence of the deposition energy on film growth on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

  15. Electrical characterization of gadolinia doped ceria films grown by pulsed laser deposition

    DEFF Research Database (Denmark)

    Rodrigo, Katarzyna Agnieszka; Heiroth, Sebastian; Lundberg, Mats

    2010-01-01

    Electrical characterization of 10 mol% gadolinia doped ceria (CGO10) films of different thicknesses prepared on MgO(100) substrates by pulsed laser deposition is presented. Dense, polycrystalline and textured films characterized by fine grains (grain sizes ... thickness. The conductivity of the nanocrystalline films is lower (7.0×10−4 S/cm for the 20-nm film and 3.6×10−3 S/cm for the 435-nm film, both at 500°C) than that of microcrystalline, bulk samples ( S/cm at 500°C). The activation energy for the conduction is found to be 0.83 eV for the bulk material, while...

  16. Properties of CdTe nanocrystalline thin films grown on different substrates by low temperature sputtering

    Institute of Scientific and Technical Information of China (English)

    Chen Huimin; Guo Fuqiang; Zhang Baohua

    2009-01-01

    CdTe nanocrystalline thin films have been prepared on glass, Si and Al2O3 substrates by radio-frequency magnetron sputtering at liquid nitrogen temperature. The crystal structure and morphology of the films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The XRD examinations revealed that CdTe films on glass and Si had a better crystal quality and higher preferential orientation along the (111) plane than the Al2O3. FESEM observations revealed a continuous and dense morphology of CdTe films on glass and Si substrates. Optical properties of nanocrystalline CdTe films deposited on glass substrates for different deposited times were studied.

  17. Structural and morphological properties of metallic thin films grown by pulsed laser deposition for photocathode application

    Science.gov (United States)

    Lorusso, A.; Gontad, F.; Caricato, A. P.; Chiadroni, E.; Broitman, E.; Perrone, A.

    2016-03-01

    In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density, while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed.

  18. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    Energy Technology Data Exchange (ETDEWEB)

    Chebil, W., E-mail: Chbil.widad@live.fr [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Fouzri, A. [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Université de Sousse (Tunisia); Fargi, A. [Laboratoire de Microélectronique et Instrumentation, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia); Azeza, B.; Zaaboub, Z. [Laboratoire Micro-Optoélectroniques et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia); and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  19. 0.532-μm laser conditioning of HfO2/SiO2 third harmonic separator fabricated by electron-beam evaporation

    Institute of Scientific and Technical Information of China (English)

    Dawei Li; Yuan'an Zhao; Jianda Shao; Zhengxiu Fan; Hongbo He

    2008-01-01

    The 0.532-μm laser conditioning of HfO2/SiO2 third harmonic separator fabricated by electron-beam evaporation (EBE) was studied.The laser induced damage threshold (LIDT) of the separator determined by 1-on-1 test is 9.1 J/cm2 and it is 15.2 J/cm2 after laser conditioning determined by raster scanning.Two kinds of damage morphologies,taper pits and flat bottom pits,are found on the sample surface and they show different damage behaviors.The damage onset of taper pits does not change obviously and the laser conditioning effect is contributed to the flat bottom pits,which limits the application of laser conditioning.

  20. Evolution of interface chemistry and dielectric properties of HfO2/Ge gate stack modulated by Gd incorporation and thermal annealing

    Directory of Open Access Journals (Sweden)

    Gang He

    2016-02-01

    Full Text Available In current work, effects of rapid thermal annealing (RTA on the interface chemistry and electrical properties of Gd-doped HfO2 (HGO/Ge stack have been investigated systematically. It has been demonstrated that the presence of GeOx interfacial layer between HfGdO and Ge is unavoidable and appropriate annealing can improve metal-oxide-semiconductor device characteristics such as interface state density, accumulation capacitance, frequency dispersion, and leakage current. The involved leakage current conduction mechanisms for metal-oxide-semiconductor (MOS capacitors based on sputtered HGO/Ge gate stacks with optimal annealed temperature also have been discussed in detail. As a result, the Al/HGO barrier height and the band offset of HGO/Ge gate stack have been determined precisely.

  1. Investigating the Temperature Effects on ZnO, TiO2, WO3 and HfO2 Based Resistive Random Access Memory (RRAM Devices

    Directory of Open Access Journals (Sweden)

    T.D. Dongale

    2016-11-01

    Full Text Available In this paper, we report the effect of filament radius and filament resistivity on the ZnO, TiO2, WO3 and HfO2 based Resistive Random Access Memory (RRAM devices. We resort to the thermal reaction model of RRAM for the present analysis. The results substantiate decrease in saturated temperature with increase in the radius and resistivity of filament for the investigated RRAM devices. Moreover, a sudden change in the saturated temperature at a lower value of filament radius and resistivity is observed as against the steady change at the medium and higher value of the filament radius and resistivity. Results confirm the dependence of saturated temperature on the filament size and resistivity in RRAM.

  2. Comprehensive studies of IR to UV light intensification by nodular defects in HfO2/SiO2 multilayer mirrors

    Science.gov (United States)

    Smalakys, Linas; Batavičiūtė, Gintarė; Pupka, Egidijus; Melninkaitis, Andrius

    2014-10-01

    Nodular defects tend to limit laser-induced damage threshold (LIDT) of multilayer dielectric coatings frequently used for laser applications. Cross-sections of localized damage morphologies correlate well with light intensifi- cation patterns caused by defect geometries. In vast majority of studies electric field enhancement in nodular defects was investigated for infrared spectral region. In this work theoretical analysis has been extended for IR - UV range. Light intensification in HfO2/SiO2 multilayer mirror coating was studied numerically. The analysis of obtained results indicates that phenomena is very sensitive to almost every investigated parameter. It was also found that field enhancement effect can be reached within distinct material layers (either of low or high refractive index). The discussion and insights complementing existing knowledge on nodular defects were made.

  3. Robust Low Voltage Program-Erasable Cobalt-Nanocrystal Memory Capacitors with Multistacked Al2O3/HfO2/Al2O3 Tunnel Barrier

    Institute of Scientific and Technical Information of China (English)

    LIAO Zhong-Wei; GOU Hong-Yan; HUANG Yue; SUN Qing-Qing; DING Shi-Jin; ZHANG Wei; ZHANG Shi-Li

    2009-01-01

    An atomic-layer-deposited Al2O3/HfO2/Al2O3 (A/H/A) tunnel barrier is investigated for Co nanocrystal memory capacitors. Compared to a single Al2O3 tunnel barrier, the A/H/A barrier can significantly increase the hysteresis window, i.e., an increase by 9 V for ±12 V sweep range. This is attributed to a marked decrease in the energy barriers of charge injections for the A/H/A tunnel barrier. Further, the Co-nanocrystal memory capacitor with the A/H/A tunnel barrier exhibits a memory window as large as 4.1 V for 100 /us program/erase at a low voltage of ±7 V, which is due to fast charge injection rates, i.e., about 2.4 × 1016 cm-2s-1 for electrons and 1.9×1016 cm-2s-1 for holes.

  4. Random lasing of ZnO thin films grown by pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Cachoncinlle, C., E-mail: christophe.cachoncinlle@univ-orleans.fr [GREMI, UMR 7344 CNRS—Université Orléans, 45067 Orléans Cedex 2 (France); Hebert, C.; Perrière, J. [Sorbonne Universités, UPMC Université Paris 06, UMR 7588, INSP, 75005 Paris (France); CNRS, UMR 7588, INSP, 75005 Paris (France); Nistor, M. [NILPRP, L 22 PO Box. MG-36, 77125 Bucharest—Magurele (Romania); Petit, A.; Millon, E. [GREMI, UMR 7344 CNRS—Université Orléans, 45067 Orléans Cedex 2 (France)

    2015-05-01

    Highlights: • Random lasing at RT in nanocrystalline ZnO PLD thin film (<100 nm). • Low optical pumping threshold (<30 kW cm{sup −2}) for UV random lasing. • Random lasing interpreted by the electron-hole plasma (EHP) model. - Abstract: Low-dimensional semiconductor structures on nanometer scale are of great interest because of their strong potential applications in nanotechnologies. We report here optical and structural properties on UV lasing in ZnO thin films. The ZnO films, 110 nm thick, were prepared using pulsed-laser deposition on c-cut sapphire substrates at 500 °C under 10{sup −2} oxygen pressure. The ZnO films are nearly stoichiometric, dense and display the wurtzite phase. The films are highly textured along the ZnO c-axis and are constituted of nanocrystallites. According to Hall measurements these films are conductive (0.11 Ω cm). Photoluminescence measurements reveals a so-called random lasing in the range 390 to 410 nm, when illuminating at 355 nm with a tripled frequency pulsed Nd-YAG laser. Such random lasing is obtained at rather low optical pumping, 45 kW cm{sup −2}, a value lower than those classically reported for pulsed-laser deposition thin films.

  5. Nanostructured silicon carbon thin films grown by plasma enhanced chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Ambrosone, G., E-mail: ambrosone@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); SPIN-CNR, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Basa, D.K. [Department of Physics, Utkal University, Bhubaneswar 751004 (India); Rigato, V. [INFN Laboratori Nazionali Legnaro, 35020 Legnaro (Padova) (Italy); Ferrero, S.; Virga, A. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

    2013-09-30

    Nanostructured silicon carbon thin films, composed of Si nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix, have been prepared by varying rf power in ultra high vacuum plasma enhanced chemical vapour deposition system using silane and methane gas mixtures diluted in hydrogen. In this paper we have studied the compositional, structural and electrical properties of these films as a function of rf power. It is shown that with increasing rf power the atomic densities of carbon and hydrogen increase while the atomic density of silicon decreases, resulting in a reduction in the mass density. Further, it is demonstrated that carbon is incorporated into amorphous matrix and it is mainly bonded to silicon. The study has also revealed that the crystalline volume fraction decreases with increase in rf power and that the films deposited with low rf power have a size distribution of large and small crystallites while the films deposited with relatively high power have only small crystallites. Finally, the enhanced transport properties of the nanostructured silicon carbon films, as compared to amorphous counterpart, have been attributed to the presence of Si nanocrystallites. - Highlights: • The mass density of silicon carbon films decreases from 2.3 to 2 g/cm{sup 3}. • Carbon is incorporated in the amorphous phase and it is mainly bonded to silicon. • Nanostructured silicon carbon films are deposited at rf power > 40 W. • Si nanocrystallites in amorphous silicon carbon enhance the electrical properties.

  6. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Santra, T. S.; Liu, C. H.; Bhattacharyya, T. K.; Patel, P.; Barik, T. K.

    2010-06-01

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of CC, CH, SiC, and SiH bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio ID/IG. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  7. Properties of ZrB2 Thin Films Grown by E-Beam Evaporation

    Science.gov (United States)

    Lad, Robert; Stewart, David; Sell, Julia; Bernhardt, George; Frankel, David; University of Maine Team

    2014-03-01

    Zirconium diboride (ZrB2) is a candidate material for many high temperature applications because it has a high melting point, high hardness, thermal shock resistance, and metallic conductivity. However, very little work has been reported concerning growth of ZrB2 thin films and high temperature oxidation behavior. In this study, ZrB2 films with nominal thickness of 200 nm have been deposited using electron-beam evaporation of either ZrB2 pellets or elemental B and Zr sources. The ZrB2 source yields a film that has a 1:1 Zr:B average composition as measured by X-ray photoelectron spectroscopy, consisting of ZrB2 precipitates within an amorphous Zr matrix as determined by X-ray diffraction. Use of elemental B and Zr sources allows precise control of film growth over a range of stoichiometries and yields ZrB2 films with much lower oxygen contamination. After annealing ZrB2 films to 1200°C in air, oxidation leads to a loss of B and formation of a textured monoclinic ZrO2 phase. Several strategies, including deposition of a thin Al2O3 capping layer over the ZrB2 film are being pursued in an attempt to stabilize the electrically conductive ZrB2 phase at high temperature, where it can be used for high temperature electronic devices in harsh environments. Supported by NSF grant # 1309983.

  8. Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition

    Science.gov (United States)

    Zhao, Lu; Liu, Hong-xia; Wang, Xing; Fei, Chen-xi; Feng, Xing-yao; Wang, Yong-te

    2017-02-01

    We investigated the effects of different annealing ambients on the physical and electrical properties of LaAlO3 films grown by atomic layer deposition. Post-grown rapid thermal annealing (RTA) was carried out at 600 °C for 1 min in vacuum, N2, and O2, respectively. It was found that the chemical bonding states at the interfacial layers (ILs) between LaAlO3 films and Si substrate were affected by the different annealing ambients. The formation of IL was enhanced during the RTA process, resulting in the decrease of accumulation capacitance, especially in O2 ambient. Furthermore, based on the capacitance-voltage characteristics of LaAlO3/Si MIS capacitors, positive V FB shifting tendency could be observed, indicating the decrease of positive oxide charges. Meanwhile, both trapped charge density and interface trap density showed decreased trends after annealing treatments. In addition, RTA process in various gaseous ambients can reduce the gate leakage current due to the enhancement of valence band offset and the reduction of defects in the LaAlO3/Si structure in varying degrees.

  9. Photoconducting ultraviolet detectors based on GaN films grown by electron cyclotron resonance molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Misra, M.; Shah, K.S. [Radiation Monitoring Devices, Inc., Watertown, MA (United States); Moustakas, T.D.; Vaudo, R.P.; Singh, R. [Boston Univ., MA (United States). Molecular Beam Epitaxy Lab.

    1995-08-01

    We report for the first time, fabrication of photoconducting UV detectors made from GaN films grown by molecular beam epitaxy. Semi-instilating GaN films were grown by the method of electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-MBE). Photoconductive devices with interdigitated electrodes were fabricated and their photoconducting properties were investigated. In this paper we report on the performance of the detectors in terms of UV responsivity, gain-quantum efficiency product, spectral response and response time. We have measured responsivity of 125A/W and gain-quantum efficiency product of 600 at 254nm and 25V. The response time was measured to be on the order of 20ns for our detectors, corresponding to a bandwidth of 25Mhz. The spectral response showed a sharp long-wavelength cutoff at 365nm, and remained constant in the 200nm to 365nm range. The response of the detectors to low-energy x-rays was measured and found to be linear for x-rays with energies ranging from 60kVp to 90kVp.

  10. Studies on Gold Doped Lead Sulphide Thin Films Grown by Silar Technique

    Science.gov (United States)

    Preetha, K. C.; Murali, K. V.; Ragina, A. J.; Deepa, K.; Remadevi, T. L.

    2011-10-01

    Narrow band gap lead chalcogenide semiconductors have been widely used in various solid state midinfrared devices, such as light emitting devices (LEDs), laser diodes (LDs), detectors, and thermoelectric generators. In this article, the subject of research is the synthesis and characterization of PbS thin films doped with gold nanoparticles and nanorods. The successive ionic layer adsorption and reaction (SILAR) technique was used to deposit PbS nanostructured films on glass substrates. The optimization of various preparative parameters resulted in mirror like smooth, uniform films with metallic appearance. Characterization of the films has been carried out using x-ray diffraction, scanning electron microscopy, optical and electrical resistivity studies. Experimental results showed that the growth parameters and doping influenced the structure, the morphology and the optical properties of PbS films. X-ray diffraction studies confirmed the cubic nanocrystalline PbS phase formation with average crystallite size in the range 16-20 nm. Doping induced increase in the grain size, which is in agreement with SEM morphology also. EDAX studies confirmed the presence of lead, sulfur along with gold crystallites in the films. All films show higher absorption in the visible-near infrared region of the spectrum. The low transmittance in the UV-VIS region offers the possibility of using the samples as solar control coatings. The films are found to be p type and the electrical conductivity decreases slightly on doping. The observed conductivity is of the order of 10-8 (Ω cm)-1. The present work established the flexibility of SILAR method to prepare good quality thin films by cost effective technique.

  11. Silicon carbide thin films as nuclear ceramics grown by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Filipescu, M., E-mail: morarm@nipne.ro [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania); Velisa, G. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Ion, V.; Andrei, A. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania); Scintee, N.; Ionescu, P. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Stanciu, S.G. [Center for Microscopy- Microanalysis and Information Processing, University ' POLITEHNICA' of Bucharest, Bucharest (Romania); Pantelica, D. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Dinescu, M. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania)

    2011-09-01

    Silicon carbide has been identified as a potential inert matrix candidate for advanced fuel. In this work, the growth of SiC thin films by pulsed laser deposition is reported. The stoicheometry and thickness of deposited films was investigated by non-Rutherford backscattering spectrometry. The influence of the deposition parameters, i.e. substrate temperature and laser fluence on the structure, morphology and optical properties of the deposited thin layers was studied. It was found that polycrystalline SiC thin films with uniform surface morphology were obtained at 873 K.

  12. Amorphization and recrystallization of epitaxial ReSi2 films grown on Si(100)

    Science.gov (United States)

    Kim, Kun HO; Bai, G.; Nicolet, MARC-A.; Mahan, John E.; Geib, Kent M.

    1991-01-01

    The effects of implantation damage and the chemical species of the implant on structural and electrical properties of epitaxial ReSi2 films on Si(100) implanted with Si-28 or Ar-40 ions, at doses ranging from 10 to the 13th/sq cm to 10 to the 15th/sq cm, were investigated using the backscattering spectrometry, XRD, and the van der Pauw techniques. Results showed that ion implantation produces damage in the film, which increases monotonically with dose; the resistivity of the film decreases monotonically with dose.

  13. Nitrogen doping in atomic layer deposition grown titanium dioxide films by using ammonium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Kaeaeriaeinen, M.-L., E-mail: marja-leena.kaariainen@lut.fi; Cameron, D.C.

    2012-12-30

    Titanium dioxide films have been created by atomic layer deposition using titanium chloride as the metal source and a solution of ammonium hydroxide in water as oxidant. Ammonium hydroxide has been used as a source of nitrogen for doping and three thickness series have been deposited at 350 Degree-Sign C. A 15 nm anatase dominated film was found to possess the highest photocatalytic activity in all film series. Furthermore almost three times better photocatalytic activity was discovered in the doped series compared to undoped films. The doped films also had lower resistivity. The results from X-ray photoemission spectroscopy showed evidence for interstitial nitrogen in the titanium dioxide structure. Besides, there was a minor red shift observable in the thickest samples. In addition the film conductivity was discovered to increase with the feeding pressure of ammonium hydroxide in the oxidant precursor. This may indicate that nitrogen doping has caused the decrease in the resistivity and therefore has an impact as an enhanced photocatalytic activity. The hot probe test showed that all the anatase or anatase dominant films were p-type and all the rutile dominant films were n-type. The best photocatalytic activity was shown by anatase-dominant films containing a small amount of rutile. It may be that p-n-junctions are formed between p-type anatase and n-type rutile which cause carrier separation and slow down the recombination rate. The combination of nitrogen doping and p-n junction formation results in superior photocatalytic performance. - Highlights: Black-Right-Pointing-Pointer We found all N-doped and undoped anatase dominating films p-type. Black-Right-Pointing-Pointer We found all N-doped and undoped rutile dominating films n-type. Black-Right-Pointing-Pointer We propose that p-n junctions are formed in anatase-rutile mixture films. Black-Right-Pointing-Pointer We found that low level N-doping has increased TiO{sub 2} conductivity. Black

  14. Schottky Junction Methane Sensors Using Electrochemically Grown Nanocrystalline-Nanoporous ZnO Thin Films

    Directory of Open Access Journals (Sweden)

    P. K. Basu

    2009-01-01

    Full Text Available Nanocrystalline-nanoporous ZnO thin films were prepared by an electrochemical anodization method, and the films were tested as methane sensors. It was found that Pd-Ag catalytic contacts showed better sensing performance compared to other noble metal contacts like Pt and Rh. The methane sensing temperature could be reduced to as low as 100∘C by sensitizing nanocrystalline ZnO thin films with Pd, deposited by chemical method. The sensing mechanism has been discussed briefly.

  15. Properties of CdS thin films grown by CBD as a function of thiourea concentration

    Energy Technology Data Exchange (ETDEWEB)

    Ximello-Quiebras, J.N.; Contreras-Puente, G.; Rueda-Morales, G.; Vigil, O. [Escuela Superior de Fisica y Matematicas-Instituto Politecnico Nacional, Edificio 9, U.P.A.L.M. 07738 DF (Mexico); Santana-Rodriguez, G. [Instituto de Investigaciones en Materiales, UNAM, CP 04510 (Mexico DF); Morales-Acevedo, A. [CINVESTAV-IPN, Depto. Ingenieria Electrica-SEES, Av. IPN 2508,CP 07360 Mexico, DF (Mexico)

    2006-04-14

    This paper reports a study of the growth rate and optical properties of CdS thin films prepared by the chemical bath deposition technique. For the deposition an aqueous solution of cadmium chloride, ammonium chloride, ammonium hydroxide and thiourea were used, the films were deposited on conducting glass (SnO{sub 2}: F). The growth kinetics is relatively fast when the quantity of thiourea is increased in the deposition solution and higher value of band gap is obtained (E{sub g}=2.44eV). The films show good transmittance in the visible region. (author)

  16. Electrical Characteristics of the Uniaxial-Strained nMOSFET with a Fluorinated HfO2/SiON Gate Stack

    Directory of Open Access Journals (Sweden)

    Yung-Yu Chen

    2014-03-01

    Full Text Available The channel fluorine implantation (CFI process was integrated with the Si3N4 contact etch stop layer (SiN CESL uniaxial-strained n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET with the hafnium oxide/silicon oxynitride (HfO2/SiON gate stack. The SiN CESL process clearly improves basic electrical performance, due to induced uniaxial tensile strain within the channel. However, further integrating of the CFI process with the SiN CESL-strained nMOSFET exhibits nearly identical transconductance, subthreshold swing, drain current, gate leakage and breakdown voltage, which indicates that the strain effect is not affected by the fluorine incorporation. Moreover, hydrogen will diffuse toward the interface during the SiN deposition, then passivate dangling bonds to form weak Si-H bonds, which is detrimental for channel hot electron stress (CHES. Before hydrogen diffusion, fluorine can be used to terminate oxygen vacancies and dangling bonds, which can create stronger Hf-F and Si-F bonds to resist consequent stress. Accordingly, the reliability of constant voltage stress (CVS and CHES for the SiN CESL uniaxial-strained nMOSFET can be further improved by the fluorinated HfO2/SiON using the CFI process. Nevertheless, the nMOSFET with either the SiN CESL or CFI process exhibits less charge detrapping, which means that a greater part of stress-induced charges would remain in the gate stack after nitrogen (SiN CESL or fluorine (CFI incorporation.

  17. Carbon-coated ZnO mat passivation by atomic-layer-deposited HfO2 as an anode material for lithium-ion batteries.

    Science.gov (United States)

    Jung, Mi-Hee

    2017-11-01

    ZnO has had little consideration as an anode material in lithium-ion batteries compared with other transition-metal oxides due to its inherent poor electrical conductivity and large volume expansion upon cycling and pulverization of ZnO-based electrodes. A logical design and facile synthesis of ZnO with well-controlled particle sizes and a specific morphology is essential to improving the performance of ZnO in lithium-ion batteries. In this paper, a simple approach is reported that uses a cation surfactant and a chelating agent to synthesize three-dimensional hierarchical nanostructured carbon-coated ZnO mats, in which the ZnO mats are composed of stacked individual ZnO nanowires and form well-defined nanoporous structures with high surface areas. In order to improve the performance of lithium-ion batteries, HfO2 is deposited on the carbon-coated ZnO mat electrode via atomic layer deposition. Lithium-ion battery devices based on the carbon-coated ZnO mat passivation by atomic layer deposited HfO2 exhibit an excellent initial discharge and charge capacities of 2684.01 and 963.21mAhg(-1), respectively, at a current density of 100mAg(-1) in the voltage range of 0.01-3V. They also exhibit cycle stability after 125 cycles with a capacity of 740mAhg(-1) and a remarkable rate capability. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Thin-Film Solar Cells with InP Absorber Layers Directly Grown on Nonepitaxial Metal Substrates

    KAUST Repository

    Zheng, Maxwell

    2015-08-25

    The design and performance of solar cells based on InP grown by the nonepitaxial thin-film vapor-liquid-solid (TF-VLS) growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and indium tin oxide transparent top electrode. An ex situ p-doping process for TF-VLS grown InP is introduced. Properties of the cells such as optoelectronic uniformity and electrical behavior of grain boundaries are examined. The power conversion efficiency of first generation cells reaches 12.1% under simulated 1 sun illumination with open-circuit voltage (VOC) of 692 mV, short-circuit current (JSC) of 26.9 mA cm-2, and fill factor (FF) of 65%. The FF of the cell is limited by the series resistances in the device, including the top contact, which can be mitigated in the future through device optimization. The highest measured VOC under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP. The design and performance of solar cells based on indium phosphide (InP) grown by the nonepitaxial thin-film vapor-liquid-solid growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and an indium tin oxide transparent top electrode. The highest measured open circuit voltage (VOC) under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP.

  19. Layer-dependent supercapacitance of graphene films grown by chemical vapor deposition on nickel foam

    KAUST Repository

    Chen, Wei

    2013-03-01

    High-quality, large-area graphene films with few layers are synthesized on commercial nickel foams under optimal chemical vapor deposition conditions. The number of graphene layers is adjusted by varying the rate of the cooling process. It is found that the capacitive properties of graphene films are related to the number of graphene layers. Owing to the close attachment of graphene films on the nickel substrate and the low charge-transfer resistance, the specific capacitance of thinner graphene films is almost twice that of the thicker ones and remains stable up to 1000 cycles. These results illustrate the potential for developing high-performance graphene-based electrical energy storage devices. © 2012 Elsevier B.V. All rights reserved.

  20. Structural, optical, and electrical properties of tin sulfide thin films grown by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Calixto-Rodriguez, M. [Instituto de Ciencias Fisicas-Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62210, Cuernavaca, Morelos (Mexico)], E-mail: manuela@fis.unam.mx; Martinez, H. [Instituto de Ciencias Fisicas-Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62210, Cuernavaca, Morelos (Mexico); Sanchez-Juarez, A.; Campos-Alvarez, J. [Centro de Investigacion en Energia-Universidad Nacional Autonoma de Mexico, 62580, Temixco, Morelos (Mexico); Tiburcio-Silver, A. [Instituto Tecnologico de Toluca-SEP, Apartado Postal 20, 52176, Metepec 3, Estado de Mexico (Mexico); Calixto, M.E. [Consultant, Cuernavaca, Morelos (Mexico)

    2009-02-02

    Tin sulfide (SnS) thin films have been prepared by spray pyrolysis (SP) technique using tin chloride and N, N-dimethylthiourea as precursor compounds. Thin films prepared at different temperatures have been characterized using several techniques. X-ray diffraction studies have shown that substrate temperature (T{sub s}) affects the crystalline structure of the deposited material as well as the optoelectronic properties. The calculated optical band gap (E{sub g}) value for films deposited at T{sub s} = 320-396 deg. C was 1.70 eV (SnS). Additional phases of SnS{sub 2} at 455 deg. C and SnO{sub 2} at 488 deg. C were formed. The measured electrical resistivity value for SnS films was {approx} 1 x 10{sup 4} {omega}-cm.