Showing papers on "Chemical vapor deposition published in 1999"
TL;DR: In this article, the synthesis of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane.
Abstract: The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials The optimized catalysts consist of Fe/Mo bimetallic species supported on a novel silica−alumina multicomponent material The high SWNT yielding catalyst exhibits high surface-area and large mesopore volume at elevated temperatures Gram quantities of SWNT materials have been synthesized in ∼05 h using the optimized catalyst material The nanotube material consists of individual and bundled SWNTs that are free of defects and amorphous carbon coating This work represents a step forward toward obtaining kilogram scale perfect SWNT materials via simple CVD routes
1,046 citations
TL;DR: In this paper, high quality epitaxial ZnO films were grown on R-plane sapphire substrates by metalorganic chemical vapor deposition, and the structural, piezoelectric, and optical properties of the films were investigated.
Abstract: High-quality ZnO films are receiving increased interest for use in low-loss high-frequency surface acoustic wave (SAW) devices, acousto-optic and optical modulators, as buffer layers for III-nitride growth, and as the active material in ultraviolet solid state lasers. In this work, high quality epitaxial ZnO films were grown on R-plane sapphire substrates by metalorganic chemical vapor deposition. The structural, piezoelectric, and optical properties of the ZnO films on R sapphire have been investigated. The epitaxial relationship between ZnO and R-Al2O3 was found to be (1120) ZnO∥(0112) Al2O3, and [0001] ZnO∥[0111] Al2O3. The interface between as-grown ZnO and R sapphire was atomically sharp and semicoherent, as evaluated by transmission electron microscopy. On annealing the films at temperatures above 850 °C, a solid state reaction occurred between ZnO and Al2O3, resulting in the formation of ZnAl2O4 (spinel) at the interface. A 15–20 nm spinel layer formed when the ZnO film was annealed at 850 °C fo...
730 citations
TL;DR: In this article, a model to account for the catalyzed growth of nanotubes by chemical vapor deposition is presented. But the model does not consider the physical dimensions of catalyzed reactions.
566 citations
TL;DR: In this article, the growth of freestanding carbon nanotubes on submicron nickel dot(s) on silicon has been achieved by plasmaenhanced-hot-filamentchemical-vapor deposition (PE-HF-CVD).
Abstract: Patterned growth of freestanding carbon nanotube(s) on submicron nickel dot(s) on silicon has been achieved by plasma-enhanced-hot-filament-chemical-vapor deposition (PE-HF-CVD). A thin film nickel grid was fabricated on a silicon wafer by standard microlithographic techniques, and the PE-HF-CVD was done using acetylene (C2H2) gas as the carbon source and ammonia (NH3) as a catalyst and dilution gas. Well separated, single carbon nanotubes were observed to grow on the grid. The structures had rounded base diameters of approximately 150 nm, heights ranging from 0.1 to 5 μm, and sharp pointed tips. Transmission electron microscopy cross-sectional image clearly showed that the structures are indeed hollow nanotubes. The diameter and height depend on the nickel dot size and growth time, respectively. This nanotube growth process is compatible with silicon integrated circuit processing. Using this method, devices requiring freestanding vertical carbon nanotube(s) such as scanning probe microscopy, field emissi...
445 citations
TL;DR: In this paper, thin amorphous silicon thin films have been deposited on porous nickel substrates by low pressure chemical vapor deposition using silane as the precursor gas, and the films were electrochemically cycled vs. a lithium electrode.
410 citations
TL;DR: A review of the methods used, and the results obtained, by a variety of groups in their attempts to prepare carbon nitride films is presented in this paper, with a somewhat speculative set of conclusions.
391 citations
TL;DR: The morphology of amorphous solid water grown by vapor deposition was found to depend strongly on the angular distribution of the water molecules incident from the gas phase, and the ability to control its properties in the laboratory may shed light on some of the outstanding conflicts related to this important material.
Abstract: The morphology of amorphous solid water grown by vapor deposition was found to depend strongly on the angular distribution of the water molecules incident from the gas phase. Systematic variation of the incident angle during deposition using a collimated beam of water led to the growth of nonporous to highly porous amorphous solid water. The physical and chemical properties of amorphous solid water are of interest because of its presence in astrophysical environments. The ability to control its properties in the laboratory may shed light on some of the outstanding conflicts related to this important material.
379 citations
TL;DR: Superlattice thin films are readily deposited by vapor-phase techniques such as sputter deposition, evaporation, and chemical vapor deposition, as well as by electrochemical deposition as discussed by the authors.
Abstract: Nanometer-scale multilayer materials exhibit a wealth of interesting structural and mechanical property behaviors. Physical-vapor-deposition technology allows almost unlimited freedom to choose among elements, alloys, and Compounds as layering constituents and to design and produce materials with compositional and structural periodicities approaching the atomic Scale. These materials have tremendous interface area density, approaching 106 mm/mm3, so that a Square centimeter area of a one-micron-thick multilayer film with a bilayer period of 2 nm has an interface area of roughly 1,000 cm2. Hence interfacial effects can dominate multilayer structure and properties leading to unusually large strains and frequently stabilization of metastable structures. The atomic-scale layering of different materials also leads to very high hardnesses and good wear resistance. These materials are a test-bed for examination of the fundamental aspects of phase stability and for exploring mechanical strengthening mechanisms. They are also becoming increasingly interesting for applications such as hard coatings, x-ray optical elements, in microelectromechanical Systems (MEMS), and in magnetic recording media and heads.In this article, we review some of the interesting structures and mechanical properties that have been observed in nanometer-scale artificial multilayer structures.Superlattice thin films are readily deposited by vapor-phase techniques such as sputter deposition, evaporation, and chemical vapor deposition, as well as by electrochemical deposition. Superlattice deposition Systems are similar to conventional film deposition Systems, except for the provision to modulate the fluxes and thereby produce alternating super-lattice layers.
294 citations
TL;DR: In this article, single-walled carbon nanotubes are synthesized by chemical vapor deposition of methane at controlled locations on a substrate using patterned catalytic islands, giving two-terminal resistances as low as 20 kΩ at low temperatures.
Abstract: Single-walled carbon nanotubes are synthesized by chemical vapor deposition of methane at controlled locations on a substrate using patterned catalytic islands. The combined synthesis and microfabrication technique presented here allows a large number of ohmically contacted nanotube devices with controllable length to be placed on a single substrate. Transport studies demonstrate ohmic contacting, giving two-terminal resistances as low as 20 kΩ at low temperatures.
291 citations
TL;DR: In this article, a nonparametric response surface method was employed to identify the Magnetron-PECVD conditions responsible for superlative SiOx barrier coatings on poly(ethylene terephthalate) (PET).
Abstract: Plasma-enhanced chemical vapor deposition (PECVD) of SiOx thin coatings on polymer surfaces yields tough hybrid materials with the gas barrier properties and transparency of glass. Combination of these properties makes these materials ideally suited for food packaging and biomedical device applications. In this study, we employ a Non-Parametric Response Surface Methods optimization to identify the Magnetron-PECVD conditions responsible for superlative SiOx barrier coatings on poly(ethylene terephthalate) (PET). Oxygen and water vapor permeances of optimized PET/SiOx composites produced by hexamethyldisiloxane and trimethylsilane have been measured as functions of temperature and are found to exhibit Arrhenius behavior. The thermal activation energy for water vapor permeation, unlike that for oxygen permeation, depends on barrier performance and increases by as much as 20 kJ/mol with an increase in barrier efficacy. Examination of these materials by phase-imaging atomic force microscopy and energy-filtered...
261 citations
TL;DR: In this paper, the authors investigated the dielectric response of a series of fiber-textured (BaxSr1−x)Ti1+yO3+z samples deposited by liquid-source metalorganic chemical vapor deposition onto Pt/SiO2/Si, as a function of the two commonly varied microstructural parameters: film thickness and Ti nonstoichiometry y.
Abstract: We have investigated the dielectric response of a series of {100} fiber-textured (BaxSr1−x)Ti1+yO3+z samples deposited by liquid-source metalorganic chemical vapor deposition onto Pt/SiO2/Si, as a function of the two most commonly varied microstructural parameters: film thickness and Ti nonstoichiometry y. We find that the overall behavior of these samples is adequately described by mean-field, Landau–Ginzburg–Devonshire theory as for bulk ferroelectrics. However, we quantify the impact of three separable factors for these films that greatly alter the dielectric susceptibility as a function of temperature, compared to that found for bulk ceramic samples at the same Ba/Sr ratio of 70/30: (i) Ti nonstoichiometry; (ii) the apparent interface effect; and (iii) the plane equibiaxial stress state resulting from thermal expansion mismatch strains. When these factors are properly taken into consideration, we show that these fine grained thin films behave in a manner entirely consistent with expectations based on ...
TL;DR: In this paper, the evolution of stress in gallium nitride films on sapphire has been measured in real time during metalorganic chemical vapor deposition, and it was shown that GaN consistently grows in tension at 1050°C.
Abstract: The evolution of stress in gallium nitride films on sapphire has been measured in real time during metalorganic chemical vapor deposition. In spite of the 16% compressive lattice mismatch of GaN to sapphire, we find that GaN consistently grows in tension at 1050 °C. Furthermore, in situ stress monitoring indicates that there is no measurable relaxation of the tensile growth stress during annealing or thermal cycling.
TL;DR: In this article, an LPCVD polycrystalline silicon layer is placed over the surface of a high-resistivity silicon wafer which is then covered with a silicon dioxide layer.
Abstract: The authors propose a solution to the surface conduction problem in silicon monolithic microwave integrated circuits (MMIC's). An LPCVD polycrystalline silicon layer is deposited over the surface of a high-resistivity silicon wafer which is then covered with a silicon dioxide layer. The polycrystalline silicon layer effectively removes, through traps, any free electrons or holes that may have been induced at the oxide-silicon interface. The CPW lines with 1.25-/spl mu/m aluminum metallization on passivated HRS substrates have an attenuation loss at 30 GHz of only 1.08 dB/cm.
TL;DR: In this paper, a new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids, which can be used in many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes.
Abstract: A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. For example, an approximately 20% improvement in effective thermal conductivity is observed when 5 vol.% CuO nanoparticles are added to water. Even more importantly, the heat transfer coefficient of water under dynamic flow conditions is increased more than 15% with the addition of less than 1 vol.% CuO particles. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers. Yttria-stabilizedmore » zirconia (YSZ) thin films are being produced by metal-organic chemical vapor deposition techniques. Preliminary results have indicated that the thermal conductivity is reduced by approximately a factor-of-two at room temperature in 10 nm grain-sized YSZ compared to coarse-grained or single crystal YSZ.« less
TL;DR: In this paper, measurements of piezoelectric coefficients d33 and d31 in wurtzite GaN and AlN using an interferometric technique are presented.
Abstract: Measurements of piezoelectric coefficients d33 and d31 in wurtzite GaN and AlN using an interferometric technique are presented. We report on the clamped values, d33c of these coefficients found in GaN and AlN thin films, and we derive the respective bulk values, d33b. The clamped value of d33c in GaN single crystal films is 2.8±0.1 pm V−1 which is 30% higher than in polycrystalline films grown by laser assisted chemical vapor deposition. The value of d33b in bulk single crystal GaN is found to be 3.7±0.1 pm V−1. The value of d33c in plasma assisted and laser assisted chemical vapor deposited AlN films was 3.2±0.3 and 4.0±0.1 pm V−1, respectively. The bulk value estimate of d33b in AlN of 5.6±0.2 pm V−1 was deduced. The values of d31, both clamped and bulk, were calculated for wurtzite GaN and AlN. We have also calculated the values of d14 in cubic phase film and bulk GaN and AlN. Interferometric measurements of the inverse piezoelectric effect provide a simple method of identifying the positive direction...
TL;DR: In this article, the performances of thin-film poly-Si solar cells with a thickness of less than 5μm on a glass substrate have been investigated, where the active i-type polySi layer was fabricated by plasma chemical vapor deposition (CVD) at low temperature.
Abstract: The performances of thin-film poly-Si solar cells with a thickness of less than 5 μm on a glass substrate have been investigated. The cell of glass/back reflector/n-i-p type Si/ITO is well characterized by the structure of naturally surface texture and enhanced absorption with a back reflector (STAR), where the active i-type poly-Si layer was fabricated by plasma chemical vapor deposition (CVD) at low temperature. The cell with a thickness of 2.0 μm demonstrated an intrinsic efficiency of 10.7% (aperture 10.1%), an open-circuit voltage of 0.539 V and a short-current density of 25.8 mA/cm2 as independently confirmed by Japan Quality Assurance. No light-induced degradation is observed. The optical and transport properties of poly-Si cells are summarized.
TL;DR: In this paper, a strong correlation was found between the hydrogen content of the films and the film properties, which was explained by the random-covalent network model, which is in contrast to a widely accepted study where no dependence of film properties on the source gas was observed, this being ascribed to a lost-memory effect.
Abstract: Hydrocarbon films were prepared by electron cyclotron resonance plasma deposition from different hydrocarbon source gases at varying ion energies. The source gases used were the saturated hydrocarbons CH4, C2H6, C3H8, C4H10 (n- and iso-) and the unsaturated hydrocarbons C2H4 and C2H2 as well as mixtures of these gases with hydrogen. Film deposition was analyzed in situ by real-time ellipsometry, and the resulting films ex situ by ion-beam analysis. On the basis of the large range of deposition parameters investigated, the correlation between hydrocarbon source gas, deposition parameters, and film properties was determined. The film properties are found to be influenced over a wide range not only by the energy of the impinging ions, but also by the choice of source gas. This is in contrast to a widely accepted study where no dependence of the film properties on the source gas was observed, this being ascribed to a “lost-memory effect.” A strong correlation was found between the hydrogen content of the films and the film properties. This strong correlation is explained on the basis of the random-covalent-network model.
TL;DR: TaN, Ta3N5, and TaOxNy films were obtained by the atomic layer deposition technique as discussed by the authors with a resistivity of 9 × 10-4 Ω cm.
Abstract: TaN, Ta3N5, and TaOxNy films were deposited by the atomic layer deposition technique. The alternate surface reactions between TaCl5 and NH3 resulted in Ta3N5 films, but when elemental zinc, serving as an additional reducing agent, was supplied on the substrates between the TaCl5 and NH3 pulses, TaN with a resistivity of 9 × 10-4 Ω cm was obtained. TaOxNy films were grown by depositing first thin Ta3N5 layers which were then partially oxidized by single water pulses. By varying the number of the Ta3N5 deposition cycles between the water pulses, the oxygen-to-nitrogen ratio of the films was controlled. The permittivity of the TaOxNy films was around 30 which is somewhat higher than that of Ta2O5.
TL;DR: In this paper, the absolute photoluminescence (PL) quantum yield, φPL, was measured for a wide variety of organic compounds in solid films, pure and molecularly doped with strongly fluorescent materials.
Abstract: We present measurements of the absolute photoluminescence (PL) quantum yield, φPL, for a wide variety of organic compounds in solid films, pure and molecularly doped with strongly fluorescent materials. The procedure, which uses an integrating sphere, does not entail comparison to other standards, and provides accurate measure of the photoluminescence efficiency for submicron thick films, prepared by high vacuum vapor deposition. Host materials include N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4-4′-diamine (TPD), a common hole transport material for light emitting diodes, tris (8-hydroxyquinolinolato) aluminum (III) (Alq3) and its methyl derivative, Almq3, two aluminum chelates used as electron transport and/or green emitting materials. Dopants include tetraphenylnapthacene (rubrene) and N,N′-diethyl quinacridone (DEQ). Doping results in a substantial increase (∼a factor 2–4) of φPL in comparison with that of the pure host. For instance, measured φPL increases from 0.25 and 0.42 for pure Alq3 a...
TL;DR: Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H-SiC(0001) substrates and produced by organometallic vapor phase epitaxy.
Abstract: Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H–SiC(0001) substrates and produced by organometallic vapor phase epitaxy. Selective lateral growth is forced to initiate from the (1120) GaN sidewalls of etched GaN seed forms by incorporating a silicon nitride seed mask and employing the SiC substrate as a pseudomask. Coalescence over and between the seed forms was achieved. Transmission electron microscopy revealed that all vertically threading defects stemming from the GaN/AlN and AlN/SiC interfaces are contained within the seed forms and a substantial reduction in the dislocation density of the laterally grown GaN. Atomic force microscopy analysis of the (1120) face of discrete pendeoepitaxial structures revealed a root mean square roughness of 0.98 A. The pendeoepitaxial layer photoluminescence band edge emission peak was observed to be 3.454 eV and is blueshifted by 12 meV as compared to the GaN seed layer.
TL;DR: In this article, a silicon carbide (SiC) nanowires on a silicon substrate were prepared using hot-filament-assisted chemical-vapor deposition with a solid silicon and carbon source.
Abstract: Silicon carbide (SiC) nanowires on a silicon substrate were prepared using hot-filament-assisted chemical-vapor deposition with a solid silicon and carbon source. The SiC nanowires show good field-emitting properties as revealed by the current–voltage characteristics. Together with its ease of preparation, these SiC nanowires are shown to have great potential in the area of electron field-emitting devices.
TL;DR: In this article, the anodic oxidn. of H2SO4 to H2S2O8 was investigated on B-doped synthetic diamond electrodes obtained by hot filament chem. vapor deposition.
Abstract: The anodic oxidn. of H2SO4 to H2S2O8 was investigated on B-doped synthetic diamond electrodes obtained by hot filament chem. vapor deposition. High current efficiency for H2S2O8 formation can be achieved in concd. H2SO4 (7.5 mol dm-3) and using high current densities (200 mA cm-2). The main side reaction is oxygen evolution. [on SciFinder (R)]
TL;DR: In this paper, the authors measured photoluminescence (PL) and Raman spectra for films deposited by hot-wire chemical vapor deposition using various hydrogen to silane ratios, and they observed: (a) a PL peak energy increase from 1.25 to 1.4 eV as the material approaches the a-to μc-Si transition region; (b) a dual-PL peak at 1.3 and 1.0 eV for the film with a H dilution ratio of 3.
Abstract: We measured photoluminescence (PL) and Raman spectra for films deposited by hot-wire chemical vapor deposition using various hydrogen to silane ratios. We observed: (a) a PL peak energy increase from 1.25 to 1.4 eV as the material approaches the a- to μc-Si transition region; (b) a dual-PL peak at 1.3 and 1.0 eV for the film with a H dilution ratio of 3; and (c) as the H ratio increases, the 1.3 eV PL fades away and the low energy PL dominates. Meanwhile, a redshift of the peak position, a decrease of the intensity, and a narrower bandwidth for the low energy PL are also observed. The low energy PL is explained by band-tail radiative transitions from two types of grain boundaries.
TL;DR: Using narrow nuclear reaction resonance profiling, aluminum profiles were obtained in ∼3.5 nm Al2O3 films deposited by low temperature chemical vapor deposition on Si(100), and the Al profile obtained on the thin film is consistent with a thin aluminum silicate layer, consisting of Al-O-Si bond units, between the silicon and Al2 O3 layer as discussed by the authors.
Abstract: Using narrow nuclear reaction resonance profiling, aluminum profiles are obtained in ∼3.5 nm Al2O3 films deposited by low temperature (<400 °C) chemical vapor deposition on Si(100). Narrow nuclear resonance and Auger depth profiles show similar Al profiles for thicker (∼18 nm) films. The Al profile obtained on the thin film is consistent with a thin aluminum silicate layer, consisting of Al–O–Si bond units, between the silicon and Al2O3 layer. Transmission electron microscopy shows evidence for a two-layer structure in Si/Al2O3/Al stacks, and x-ray photoelectron spectroscopy shows a peak in the Si 2p region near 102 eV, consistent with Al–O–Si units. The silicate layer is speculated to result from reactions between silicon and hydroxyl groups formed on the surface during oxidation of the adsorbed precursor.
TL;DR: In this paper, a dielectric film was prepared by radio-frequency plasma-enhanced chemical vapor deposition from mixtures of tetramethylsilane with oxygen, and the films were characterized as-deposited and after annealing at 400°C to determine the thermal stability of their properties.
Abstract: Dielectric films have been prepared by radio-frequency plasma-enhanced chemical vapor deposition from mixtures of tetramethylsilane with oxygen. The films have been characterized as-deposited and after annealing at 400 °C to determine the thermal stability of their properties. Rutherford backscattering and forward recoil elastic scattering have been used for determination of the composition of the films. Optical properties were characterized by Fourier transform infrared spectroscopy and measurements of the index of refraction and optical gap. The electrical properties were measured in a Si/insulator/metal configuration. It has been found that the index of refraction decreases and the optical gap and dielectric constant increase with increasing oxygen concentration in the gas feed. While the materials did not show a mass or composition loss after annealing, the annealing resulted in a reduction of the dielectric constant of the films. Dielectric constants as low as 3.1 have been obtained after annealing the film deposited from pure tetramethylsilane.
Patent•
18 Mar 1999TL;DR: A method for fabricating a silicon oxide and silicon glass layers at low temperature using soft power-optimized Plasma-Activated CVD with a TEOS-ozoneoxygen reaction gas mixture (TEOS O3/O2 PACVD) is described in this paper.
Abstract: A method for fabricating a silicon oxide and silicon glass layers at low temperature using soft power-optimized Plasma-Activated CVD with a TEOS-ozone-oxygen reaction gas mixture (TEOS O3/O2 PACVD) is described. It combines advantages of both low temperature Plasma-Enhanced Chemical Vapor Deposition (PECVD) and TEOS-ozone Sub-Atmospheric Chemical Vapor Deposition (SACVD) and yields a coating of silicon oxide with stable and high deposition rate, no surface sensitivity, good film properties, conformal step coverage and good gap-fill. Key features of the invention's O3/O2 PACVD process are: a plasma is maintain throughout the entire deposition step in a parallel plate type reactor chamber, the precise RF plasma density, ozone concentration in oxygen and the deposition temperature. These features provide the reaction conditions for the proper O3/O2 reaction mechanism that deposits a conformal silicon oxide layer. The process has significant implication for semiconductor device manufacturing involving the deposition of a dielectric over a conducting non-planar surface.
TL;DR: In this paper, the basic electrochemical properties of high quality diamond thin-films (3-6μm thick) are highlighted, and the use of diamond for the voltammetric detection of trace metal ions is also illustrated.
TL;DR: In this paper, the authors have successfully grown nanometer-scale InGaN self-assembled quantum dots (QDs) on a GaN surface without any surfactants, using atmospheric-pressure metalorganic chemical vapor deposition.
Abstract: We have successfully grown nanometer-scale InGaN self-assembled quantum dots (QDs) on a GaN surface without any surfactants, using atmospheric-pressure metalorganic chemical vapor deposition. Atomic force microscopy shows that the average diameter of InGaN QDs is as small as 8.4 nm. Next, we have investigated the dependence of the QDs properties on the growth conditions: the amount of InGaN deposited and the growth temperature. Moreover, we have investigated the optical property of InGaN QDs, so that the strong emission was seen at 2.86 eV at room temperature.
TL;DR: In this article, a single crystal GaN thin film was successfully grown on a Si (111) substrate by means of atmospheric pressure metalorganic chemical vapor deposition (MOCVD) and the fullwidth at half maximum (FWHM) of the double-crystal X-ray rocking curve for GaN(0004) was 600 arcsec.
Abstract: A single crystal GaN thin film was successfully grown on a Si (111) substrate by means of atmospheric pressure metalorganic chemical vapor deposition. Though there is a large difference in thermal expansion coefficients between GaN and Si, an intermediate layer consisting of AlN and AlGaN improved the quality of GaN on Si and reduced meltback etching during growth. Pits and cracks were not observed on the substrate and a mirror-like surface was obtained. The full-width at half maximum (FWHM) of the double-crystal X-ray rocking curve for GaN(0004) was 600 arcsec. Photoluminescence measurement at room temperature for a Si-doped film revealed a sharp band-edge emission with a FWHM of 62.5 meV, which is the narrowest value reported to date.
TL;DR: In this article, experimental and theoretical research on heat conduction in single-crystal semiconducting and superconducting films and superlattices, polycrystalline diamond films, and highly disordered organic and oxide films is presented.
Abstract: Heat conduction in novel electronic films influences the performance and reliability of micromachined transistors, lasers, sensors, and actuators. This article reviews experimental and theoretical research on heat conduction in single-crystal semiconducting and superconducting films and superlattices, polycrystalline diamond films, and highly disordered organic and oxide films. The thermal properties of these films can differ dramatically from those of bulk samples owing to the dependence of the material structure and purity on film processing conditions and to the scattering of heat carriers at material boundaries. Predictions and data show that phonon scattering and transmission at boundaries strongly influence the thermal conductivities of single-crystal films and superlattices, although more work is needed to resolve the importance of strain-induced lattice defects. For polycrystalline films, phonon scattering on grain boundaries and associated defects causes the thermal conductivity to be strongly anisotropic and nonhomogeneous. For highly disordered films, preliminary studies have illustrated the influences of impurities on the volumetric heat capacity and, for the case of organic films, molecular orientation on the conductivity anisotropy. More work on disordered films needs to resolve the interplay among atomic-scale disorder, porosity, partial crystallinity, and molecular orientation.