Atmospheric Chemical Vapor Research Articles

Investigation of Gate-Stacked In-Ga-Zn-O TFTs with Ga-Zn-O Source/Drain Electrodes by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition.

Atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) was employed for the fabrication of indium gallium zinc oxide thin-film transistors (IGZO TFTs) with high transparent gallium zinc oxide (GZO) source/drain electrodes. The influence of post-deposition annealing (PDA) temperature on GZO source/drain and device performance was studied. Device with a 300 °C annealing demonstrated excellent electrical characteristics with on/off current ratio of 2.13 × 108, saturation mobility of 10 cm2/V-s, and low subthreshold swing of 0.2 V/dec. The gate stacked LaAlO3/ZrO2 of AP-IGZO TFTs with highly transparent and conductive AP-GZO source/drain electrode show excellent gate control ability at a low operating voltage.

Using KrF ELA to Improve Gate-Stacked LaAlO₃/ZrO₂ Indium Gallium Zinc Oxide Thin-Film Transistors with Novel Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition Technique.

Atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique and KrF excimer laser annealing (ELA) were employed for the fabrication of indium gallium zinc oxide thin-film transistors (IGZO-TFTs). Device with a 150 mJ/cm2 laser annealing densities demonstrated excellent electrical characteristics with improved on/off current ratio of 4.7×107, high channel mobility of 10 cm2/V-s, and low subthreshold swing of 0.15 V/dec. The improvements are attributed to the adjustment of oxygen vacancies in the IGZO channel to an appropriate range of around 28.3% and the reduction of traps at the high-k/IGZO interface.

Numerical Study of Turbulent Confined Jets Impinging on a Heated Substrate for Thin Film Deposition

This paper reports on the study of confined jets and jets interaction in terms of increasing chemical transport. The context of this study is the atmospheric pressure plasma-enhanced chemical vapor deposition, higher thin film growth rate being desired, while maintaining total flow rate as low as possible. Turbulence mixing and enhanced heat transfer are the physical mechanisms identified as being capable of increasing the growth rate at atmospheric pressure. A numerical study of jets impinging on a heated substrate was carried out using quasicompressible Reynolds-Averaged Navier–Stokes (RANS) equations. Abe–Kondoh–Nagano (AKN) low-Reynolds k-ε and standard k-ε models were tested using an unconfined impinging jet at Reynolds number Re = 23,750 for jet diameter to plate-spacing ratios of H/d = 2 and H/d = 6. Results were compared with experimental data from the literature. Based on numerical results and in accordance with existing findings, the AKN low-Reynolds k-ε was shown to be reasonably accurate and was thus chosen for the numerical study. The effects of flow rate, hole diameter and length, jet-to-jet spacing, confinement width, and jet number were investigated numerically for inline jets confined between two vertical planes for jet Reynolds numbers between 810 and 5060. The configurations with the greatest turbulent intensity were studied, with the addition of diluted species transport and consumption. A laminar flow setup with a slot jet (Re = 79.5) was compared to two injection designs consisting of a simple set of 12 impinging gas jets (Rej = 2530; H/d = 3) with and without the adjunction of a wire to break the jets (Rej = 1687; H/d = 2). The two turbulent injection methods improved growth rate by 15%, which mainly resulted from a larger gas heating by the surface due to turbulent heat exchange in the jet impact zone.

Fabrication of Titanium-Based Hard Coatings by Atmospheric Microplasma-Metal Organic Chemical Vapor Deposition Using Titanium Tetraisopropoxide

The atmospheric microplasma metal organic chemical vapor deposition (AP-MOCVD) using titanium (IV) tetraisopropoxide (TTIP) as a metal alkoxide titanium source was investigated for depositing TiC and TiN hard coatings on stainless steel rods for improving the tool life of electroplated diamond tools. The components and morphology of the coating deposited by microplasma AP-MOCVD with several gas sources and different processes was observed and analyzed. The titanium-based hard coatings composed of TiC, TiN, and TiO2 was successfully obtained by microplasma AP-MOCVD using TTIP as a metal alkoxide titanium source with mixed gases (CH4, N2, H2, and Ar). For the fabrication of titanium-based coatings (TiC, TiN) by microplasma AP-MOCVD, it is important that the carbon and oxygen content, which are components of TTIP, are reduced. The addition of hydrogen gas in the microplasma AP-MOCVD process, followed by nitriding effectively reduces the carbon and oxygen content in the coating.

The growth characteristics of microcrystalline Si thin film deposited by atmospheric pressure plasma-enhanced chemical vapor deposition

Microcrystalline silicon thin film was grown by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique with a cylindrical rotary electrode supplied with 150 MHz very-high-frequency power. The crystalline volume fraction could be controlled by changing the flow rate ratio of silane and hydrogen gas during AP-PECVD. We could also control it by regulating the substrate scanning speed. At low substrate scanning speed, the silicon film had a low crystalline volume faction and layer-by-layer structure with alternating layers of amorphous and microcrystalline Si. On the other hand, at high substrate scanning speed, silicon crystals of sizes 25 nm grew homogeneously throughout the whole film.

Effect of O2/Ni ratio on structure and surface morphology of atmospheric pressure MOCVD grown NiO thin films

ABSTRACTEffect of oxygen to nickel molar ratio (O2/Ni) on the crystallinity of atmospheric pressure metal organic chemical vapor deposition (APMOCVD) grown NiO at 500°C is reported. X-ray diffraction (XRD) analysis including grazing incident angle θ of 0.6°, θ-2θ, ɸ and rocking curve scan are employed for crystallographic characterization. Furthermore, surface roughness is studied by atomic force microscopy (AFM). No evidence of diffraction peaks in X-ray grazing incident angle measurement confirms that all the grown NiO films are well oriented along a certain direction. θ-2θ scan results further indicate that the samples are highly oriented only along [111] direction on (0001) sapphire substrates. The analysis of full width at half maximum (FWHM) of rocking curve scan of (111) plane shows that higher O2/Ni ratio results in better crystallinity. The best crystallinity is achieved with FWHM as low as 0.106° at (111) rocking curve scan corresponding to 82.57nm grain size. AFM measurement shows that NiO films grown with higher O2/Ni ratio have smoother surface morphology.

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

Electron Microscopy Study of Y-Shaped Carbon Fibers with Different Morphologies

A series of techniques, including field emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, and energy dispersive X-ray spectroscopy were employed to investigate three types of Y-shaped carbon fibers that were synthesized by the thermal decomposition of acetylene using an atmospheric pressure catalytic chemical vapor deposition process and copper tartrate as a catalyst precursor. On the basis of electron microscopy analysis, we propose that the simultaneous growth of three pieces of carbon fibers on the same copper catalyst particle results in the formation of Y-shaped carbon fibers. When several copper catalyst particles became positioned in a stratified arrangement, other types of Y-shaped carbon fibers were obtained. Our study indicates that the morphology of various Y-shaped carbon fibers can be controlled by tailoring the configuration of the copper catalyst particles used to generate them.

Selective growth of carbon nanotubes using catalyst poisoning and geometric trench

This work suggests catalyst poisoning and geometric patterned approaches to selectively grow multiwall carbon nanotubes. Ferromagnetic particles as a catalyst for CNTs growth vanish when they are deposited over an aluminum thin film. Additionally, geometric features, such as trenches or cavities, are revealed to be capable of selectively ceasing the growth of CNTs even though catalytic thin films were covered on entire samples by an atmospheric thermal chemical vapor deposition technique.

Hydrogen‐assisted nitrogen‐acceptor doping in ZnO

AbstractN‐doped ZnO (ZnO:N) thin films were prepared by atmospheric pressure mist chemical vapor deposition. The as‐grown ZnO:N film was of high resistivity with ambiguous carrier type, while the annealed sample showed p‐type conductivity with a resistivity of 22.3 Ω cm and hole concentration of 5.49 × 1017 cm–3. The crystallinity of ZnO films was improved by the annealing treatment. Unintentionally H impurities introduced into the as‐grown film could be annealed out and a near‐edge absorption related to the N states in band gap was present in the annealed sample, which was indicative of the appearance of activated N in ZnO during the annealing process. A hydrogen‐assisted nitrogen‐acceptor doping mechanism was proposed to explain the observation of p‐type ZnO. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Heavy arsenic doping of silicon grown by atmospheric pressure selective epitaxial chemical vapor deposition

abstractSelective epitaxial Si with a high arsenic concentration of 2.2 × 1019 atoms/cm3 was deposited at a high growth rate of 3.3 nm/min under atmospheric pressure. It was confirmed that this method had excellent selectivity and produced films having good crystalline quality, abrupt dopant profiles at the interfaces, and smooth surfaces. The growth mechanism is discussed in terms of the relationship between the effects of arsenic surface segregation and etching by hydrogen chloride.

PREPARATION OF 1-3 CONNECTIVITY COMPOSITE FILMS OF WELL-ALIGNED ZnO WHISKER ARRAYS WITH AN ORGANIC RESIN

Zinc oxide whisker arrays well-aligned along [0001] direction have been grown on the substrates of glass and single crystal silicon by atmospheric metal organic chemical vapor deposition method (MOCVD). The SEM observation indicated that the whiskers were quite uniform in length and diameter. The whisker arrays were very dense, and the gap among the whiskers was less than 1 μm. The array materials were proposed as the component to prepare 1-3 piezoelectric composite film in-situ. Epoxy resin was used as the matrix materials. The key points to prepare the composites are how to make the resin enter the array and control a suitable thickness of the resin films. Several approaches were studied. The results showed that the best was the vertical sucking method. The SEM observations indicated that the thickness was well controlled as almost same as the length of the whiskers, and the resin perfectly entered the array without pore. The 1-3 piezoelectric composite film has great potential applications in micro sensor and actuator arrays.

Assessment of discharges for large area atmospheric pressure plasma-enhanced chemical vapor deposition (AP PE-CVD)

Different types of dielectric barrier discharges are evaluated for atmospheric pressure plasma chemical vapor deposition (AP PE-CVD). Special focus is on surface and coplanar dielectric barrier discharges.

Growth of InN pillar crystal films by means of atmospheric pressure halide chemical vapor deposition

Preparation of InN thin films has been examined using an atmospheric pressure halide chemical vapor deposition technique. It was found that the quality of the InN pillar crystal film grown on a Si(100) substrate is significantly dependent upon the ratio of NH3∶InCl3 used as source materials. Hall mobility decreases as the NH3∶InCl3 ratio is decreased, while the carrier concentration increases. This is explained in terms of the formation of nitrogen vacancies. A decrease of the NH3∶InCl3 ratio causes the increase of nitrogen defects in the InN film. This also increases the number of electrons being trapped by the defects, while their mobility is reduced because of the electrons being scattered at the vacancies.

Processing of yttria stabilized zirconia thin films by liquid fuel combustion chemical vapor deposition

ABSTRACTYttria fully stabilized zirconia (YSZ) thin films have been successfully synthesized with atmospheric combustion chemical vapor deposition (ACCVD) technique with liquid fuel. Key processing parameters, such as the ratio of oxygen to liquid fuel in the flame, the concentration of metal reagents in the solution, the temperature of the substrate and substrate material, have been investigated. The as-grown films are characterized with X-ray diffraction and scanning electron microscopy. Within the range of experimental parameters, the phase of the film is predominantly of cubic structure. The phase and crystallinity of the films are strongly dependent upon the experimental variables.

Polycrystalline and Amorphous Chromium Oxide MOCVD

AbstractThis paper will report the methods to deposit polycrystalline or amorphous chromium oxide (Cr2O3) thin films, which have potential applications in optoelectronics such as components for flat panel display devices. An atmospheric cold wall chemical vapor deposition (CVD) system was used to thermally decompose sublimed chromium acetylacetonate(Cr(C5H7O2)3) precursor, which gave Cr2O3 films. Oxygen concentration in gas phase is the key factor determining chromia film structure. In oxygen containing CVD system, the deposited films were polycrystalline Cr2O3, with (006), and (110) orientations. In inert, O2 free environment, the grown films were amorphous chromium oxide, as identified by XPS and XRD results. Based on depth profiling AES results, even in an oxygen free ambient, the elemental Cr/O ratio in films still remained stoichiometry(Cr:O = 2:3). Oxygen atoms might originate from acetylacetonyl (C5H7O2) ligands in the Cr(C5H7O2)3precursor.

Chemical Kinetic Calculations Of The Gas Phase In Atmospheric Pressure Microwave Plasma-Assisted Chemical Vapour Deposition Of Diamond

The authors develop a numerical model for the atmospheric pressure microwave plasma chemical vapour deposition (CVD) of diamond in a two-dimensional field. The continuity, momentum, energy, and chemical kinetic calculations are carried out using a finite-difference control volume method. The microwave dissipated power was calculated using Maxwell’s equations. The temperature field, stream lines, and species concentration profiles were obtained for two different MW powers. We found that the species concentrations inside the MW reactor are not in chemical equilibrium, and the viscosity and thermal conductivity of pure hydrogen may be used as the mixture properties without any major loss of accuracy. However, these properties must be calculated based on the local concentrations of atomic and molecular hydrogen. By increasing the power, we increase the molar ratio of [H]/[CH3], which is advantageous in the CVD of diamond, and the product of [H]Ð[CH3] does not change. The latter parameter affects the rate of diamond growth. We also found that at low microwave power the effect of the thermal diffusion can be negligible.

Preparation of textured Mg2TiO4 thin films on Si substrate by atmospheric pressure metallorganic chemical vapour deposition

Highly crystalline and fully [1 0 0]-textured Mg2TiO4 thin films have been successfully prepared on Si(1 0 0) and (1 1 1) substrate by using atmospheric pressure metallorganic chemical vapour deposition. Magnesium acetylacetonate was used as the metallorganic source. The films were produced in a horizontal warm-wall reactor. X-ray diffraction experiments provided evidence that the Mg2TiO4 thin films on Si substrate were fully textured with [1 0 0] orientation perpendicular to the substrate surface. The films obtained a very smooth and densely packed surface morphology. The relationship between substrate temperature and crystallographic orientations was also considered.

Epitaxial Growth and Properties of Mg-Doped Gan Film Produced by Atmospheric Mocvd System With Three Layered Lammar Flow Gas Injection

AbstractMg-doped GaN films with a variety of Mg concentrations were grown on sapphire (0001) by horizontal atmospheric metalorganic chemical vapor deposition (MOCVD) system with three layered laminar flow gas injection in an attempt to study the Mg doping effects on film quality. The increase of Mg concentration induced an increase of x-ray rocking curve full width at half maximum (FWHM) and degradation of surface morphology. Secondary ion mass spectroscopy (SIMS) analysis shows increase of Si and O, associated with Mg-doping concentration. Si and O concentrations of Mg-doped film are up to 5×1016cm−3 and 5×1017cm−3 at Mg concentration of 4.5×1019cm−3, respectively. Strong 380nm emission and weak 430nm emission were observed by photoluminescence (PL) measurement at room temperature for as-grown Mg-doped GaN films which shows p-type conductivity after thermal annealing. While, in highliy Mg-doped GaN films which do not show the p-type conduction after thermal annealing, 430nm and/or 450nm emission were dominating. The highest room temperature free hole concentration achieved was p=2.5× 1018cm−3 with mobility μp=l.9cm2/V s.

Longitudinal phonon modes in a ZnSe/ZnSxSe1−x lattice-mismatched superlattice

Longitudinal acoustic and optical phonon modes of a ZnSe/ZnSxSe1−x (x≂0.20) lattice-mismatched superlattice, prepared with atmospheric metal organic chemical vapor deposition method, have been investigated by light scattering measurements. Despite a lattice mismatch as large as 1% between the alternating layers, the measured longitudinal elastic constants are in agreement with the calculated values of an unstrained effective medium model. Furthermore, a correlative study was made by fitting the spectra to a spatial correlation model, which reproduces line shapes of the observed confined longitudinal-optical modes without incorporating the strain effects. The results demonstrate that a combination of Brillouin and Raman spectroscopy provides a good method to determine accurately the elastic constants and strain information of the lattice-mismatched superlattices and heterostructures.