Cyclotron Resonance Plasma-enhanced Chemical Vapor Research Articles

Influence of Nitridation Time on the Characteristics of GaN Films Deposited on Ni Metal Substrate by ECR-MOCVD

GaN films were deposited on metal Ni substrates using electron cyclotron resonance plasma-enhanced metal organic chemical vapour deposition system (ECR-PEMOCVD). The nitridation time dependent structural and morphological characteristics of GaN films were systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis. The results indicate that it is feasible to deposit GaN films on Ni metal substrate under the proper deposition procedures. The high quality GaN films with c-axis preferred orientation and dense and uniform microstructure are successfully obtained under the optimized nitridation time. The GaN/Ni structure has great potential for the improvement of short-wavelength optical devices with excellent heat dissipation.

Growth of high c-orientated crystalline GaN films on amorphous Cu/glass substrates with low-temperature ECR-PEMOCVD

A low temperature growth method based on electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition system (ECR-PEMOCVD) was proposed for the growth of gallium nitride (GaN) films on ordinary soda-lime glass substrates with sputtered Cu as intermediate layer (Cu/glass substrates). The influence of deposition temperature on the properties of the GaN films on Cu/glass substrates was systematically investigated by means of In-situ reflection high energy electron diffraction, X-ray diffraction, atomic force microscopy and photoluminescence spectra. With this method, high c-orientated crystalline GaN films with relatively smooth surface were achieved on amorphous Cu/glass substrate at an extremely low temperature of ~400 °C. The successfully growth of crystalline GaN films on amorphous Cu/glass substrates show great potential for significant improvements in the scalability and cost of GaN based devices, since the adverse effects with high temperature process for glass substrates can be effectively suppressed by this technique.

Deposition and characteristics of GaN films on Ni metal substrate by ECR-PEMOCVD

Gallium nitride (GaN) films were deposited on Ni metal substrate using electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition system. With this approach, highly c-oriented GaN films with smooth surface were obtained at an extremely low temperature of ~480 °C. The trimethyl gallium (TMGa) flux dependent structural, morphological, and optical characteristics of GaN films were investigated by X-ray diffraction analysis, reflection high energy electron diffraction, atomic force microscopy and photoluminescence analysis. The results indicate that it is feasible to deposit GaN films on Ni metal substrate under the proper deposition procedures. The high quality GaN films with high c-axis orientation and strong ultraviolet emission peak are successfully achieved under the optimized TMGa flux of 1.2 sccm. The GaN/Ni structure has great potential for the development of high power devices with excellent heat dissipation.

Low-temperature growth of high c-orientated crystalline GaN films on amorphous Ni/glass substrates with ECR-PEMOCVD

A low temperature growth method based on electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition system (ECR-PEMOCVD) was proposed for the growth of GaN films on ordinary soda-lime glass substrates with Ni as intermediate layer. With this method, high c-orientated crystalline GaN films with atomically smooth surface were achieved on amorphous Ni/glass substrate at an extremely low temperature of ∼480 °C. This GaN/Ni/glass structures have great potential for dramatically improve the scalability and cost of solid-state lighting, since the adverse effects with high temperature process for glass substrates can be effectively suppressed by this technique.

Indium Nitride Film Growth by Metal Organic Chemical Vapor Deposition with Nitrogen Activation in Electron Cyclotron Resonance Discharge Sustained by 24 GHz Gyrotron Radiation

We report the results of the first experiments on the growth of indium nitride films by electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition. Discharge sustained by the radiation of a technological gyrotron with a frequency of 24 GHz and power up to 5 kW was used to provide active nitrogen flow. The use of higher frequency microwave radiation for plasma heating provides a higher plasma density, and more active nitrogen flow. Mirror-smooth homogeneous hexagonal InN films were grown on ittria-stabilized zirconia and sapphire substrates. It was shown that single-crystal InN films can be grown on Al2O3 (0001) substrates if a double buffer layer of InN/GaN is used. The growth rate of 1 µm/h was demonstrated in this case. Film properties are studied by optical and electron microscopies, secondary ion mass spectroscopy, X-ray diffraction, and photoluminescence.

On the origin of emission and thermal quenching of SRSO:Er3+ films grown by ECR-PECVD.

Silicon nanocrystals embedded in a silicon-rich silicon oxide matrix doped with Er3+ ions have been fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition. Indirect excitation of erbium photoluminescence via silicon nanocrystals has been investigated. Temperature quenching of the photoluminescence originating from the silicon nanocrystals and the erbium ions has been observed. Activation energies of the thermally activated quenching process were estimated for different excitation wavelengths. The temperature quenching mechanism of the emission is discussed. Also, the origin of visible emission and kinetic properties of Er-related emission have been discussed in details.

Influence of Ar/H2 ratio on the characteristics of boron-doped nc-Si:H films prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Boron-doped hydrogenated nanocrystalline silicon (nc-Si(B):H) films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). The effect of Ar/H2 ratio on the characteristic of as-grown nc-Si(B):H films was investigated systematically with Raman scattering, XRD, XPS as well as Hall effect measurements. The experimental results indicate that the increase of Ar/H2 ratio can enhance the concentration of B in the as-grown films. On the other hand, with the Ar/H2 ratio increasing, the crystallinity of the films deteriorated sharply, and the electrical properties of the as-grown films decreased. Langmuir Probe was used to investigate the electron temperature (Te) of microwave activated B2H6/Ar/H2 plasmas. Finally, the microscopic mechanism of the enhancement in doping efficiency was elucidated in terms of the plasma reaction equations of B2H6 and Langmuir probe testing result.

Deposition and properties of highly c-oriented of InN films on sapphire substrates with ECR-plasma-enhanced MOCVD

InN films with highly c-axis preferred orientation were deposited on sapphire substrate by low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). Trimethyl indium (TMIn) and N2 were applied as precursors of In and N, respectively. The quality of as-grown InN films were systematically investigated as a function of TMIn fluxes by means of reflection high-energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), and atomic force microscopy (AFM). The results show that the dense and uniform InN films with highly c-axis preferred orientation are successfully achieved on sapphire substrates under optimized TMIn flux of 0.8 ml·min−1. The InN films reported here will provide various opportunities for the development of high efficiency and high-performance semiconductor devices based on InN material.

Stress analyses of GaN film manufactured by ECR plasma-enhanced chemical vapor deposition

The residual stress in GaN film grown on (0001) α-Al2O3 substrate at 450–500 °C by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR–PECVD) is investigated. Macro deformation analysis reveals a low level of compressive stress, from −0.46 GPa to −1.03 GPa in GaN/Sapphire. Low growth temperature and high N2:TMG flow ratio contributes to decreasing of residual stress. A blue shift for the edge peak in photoluminescence analysis (PL) is related to compressive stress. Roughness statistics and AFM morphology of GaN film show a fine smoothness and uniform surface. All results demonstrate that ECR-PECVD process is favorable for depositing GaN films at low temperature.

Influence of Ar/H2 ratio on the characteristics of phosphorus-doped hydrogenated nanocrystalline silicon films prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition

Phosphorus-doped hydrogenated nanocrystalline silicon films (nc-Si(P):H) were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition. The effect of Ar/H2 ratio on the characteristics of as-grown nc-Si(P):H films was investigated systematically with Raman scattering, Hall effect measurements as well as Fourier Transform infrared spectroscopy (FTIR). The results indicated that the Ar/H2 ratio played a critical role for the crystalline quality and electrical properties of the nc-Si:H films. FTIR also showed that infrared spectrum intensity of SiH2 bonding mode peak decreased when Ar/H2 ratio increased. The optimal value Ar/H2 ratio of 10/15 was obtained for high quality nc-Si(P):H films with high electron density and the mechanism was elucidated in terms of Raman and FTIR analysis.

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y = 0.36–0.42 in SiyO1−y), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2 h) annealed at various temperatures (Ta = 900–1100 °C) under either Ar or (Ar + 5%H2) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate Ta can be qualitatively understood in terms of a ‘crystalline core–amorphous shell’ Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing Ta, the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails.

The Effect of a TiN Interlayer on the Tribological Properties of Diamond-like Carbon Films Deposited on 7A04 Aluminum Alloy

Aluminum-based alloys are known to be significant candidates in the automotive and aerospace industries. However, the relatively poor wear resistance of aluminum alloys restricts their further application. In this paper, diamond-like carbon (DLC) films are deposited on the 7A04 aluminum alloy to improve its wear resistance by electron cyclotron resonance plasma-enhanced chemical vapor deposition. Before the DLC film deposition, TiN films were first fabricated as interlayer between the 7A04 aluminum alloy and DLC films by unbalanced magnetron sputtering. The influence of the TiN buffer layer on the mechanical properties of the DLC film is studied. The results showed that the TiN interlayer could provide enough mechanical support for the DLC films by suppressing plastic deformation of the aluminum alloy and then could effectively improve wear resistance of DLC films on 7A04 aluminum alloy.

Low-temperature growth of highly c-oriented InN films on glass substrates with ECR-PEMOCVD

High quality InN films are deposited with an interlayer of high c-orientation (002) AZO (Aluminium-doped Zinc Oxide; ZnO:Al) films on glass substrates by electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) at low temperature. AZO films used as a buffer layer are effective for the epitaxial growth of InN films. The influence of Trimethyl Indium (TMIn) flux on the properties of InN films is systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), atomic force microscopy (AFM) and optical transmittance spectra. The results indicate that high quality InN films with high c-orientation and small surface roughness are successfully achieved at an optimized Trimethyl Indium (TMIn) flux of 5.5 sccm. The InN/AZO structures have great potential for the development of full spectra solar cells.

Influence of N2 flux on the improvement of highly c-oriented GaN films on diamond substrates

High-quality GaN films are deposited on freestanding thick diamond films by electron cyclotron resonance plasma-enhanced metal organic chemical vapour deposition (ECR-PEMOCVD). Trimethyl gallium (TMGa) and N2 are applied as precursors and different N2 fluxes are used to achieve high-quality GaN films. The influence of N2 flux on the properties of GaN films is systematically investigated by X-ray diffraction analysis (XRD), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM) and Hall effect measurement (HL). The results show that the high-quality GaN films with small surface roughness of 4.5 nm and high c-orientation are successfully achieved at the optimized N2 flux of 90sccm. The most significant improvements in morphological, structural, and optical properties of GaN films are obtained by using a proper N2 flux.

ChemInform Abstract: Low Temperature Deposition of SiO2 by Distributed Electron Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Characterizations of GaN film growth by ECR plasma chemical vapor deposition

The electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition technology (ECR–MOPECVD) is adopted to grow GaN films on (0001) α-Al2O3 substrate. The gas sources are pure N2 and trimethylgallium (TMG). Optical emission spectroscopy (OES) and thermodynamic analysis of GaN growth are applied to understand the GaN growth process. The OES of ECR plasma shows that TMG is significantly dissociated in ECR plasma. Reactants N and Ga in the plasma, obtained easily under the self-heating condition, are essential for the GaN growth. They contribute to the realization of GaN film growth at a relatively low temperature. The thermodynamic study shows that the driving force for the GaN growth is high when N2:TMG>1. Furthermore, higher N2:TMG flow ratio makes the GaN growth easier. Finally, X-ray diffraction, photoluminescence, and atomic force microscope are applied to investigate crystal quality, morphology, and roughness of the GaN films. The results demonstrate that the ECR–MOPECVD technology is favorable for depositing GaN films at low temperatures.

Structural and optical properties of Si nanocrystals embedded in SiO 2/SiN x multilayers

Si nanocrystals (Si-ncs) embedded in SiO 2/SiN x multilayer structures can be of interest for optoelectronic devices such as solar cells. However, controlling the size and density of the Si-ncs is strongly requested for an efficient use in a functioning solar cell device. In this work, SiO 2 and Si-rich Si 3N 4 (SRN) layers have been deposited alternatively on a silicon wafer in an electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) using N 2O, NH 3 and SiH 4 gases. The Si-ncs can be obtained in the SRN layers after thermal annealing, thanks to the phase separation between the Si atoms in excess and the matrix. The SiO 2 layers allow the Si clusters’ spatial confinement in the SRN film and are also used as a barrier of diffusion. The amount of Si atoms in excess can be controlled by the gas flow ratio. The structural characteristics of Si-ncs density have been investigated by conventional TEM and HR-TEM for different silicon nitride layer thicknesses. Their optical properties were studied by photoluminescence (PL) spectroscopy. Results clearly show a room temperature PL in the visible range, which is of interest for the solar cells applications.

Light Emission from Rare-Earth Doped Silicon Nanostructures

Rare earth (Tb or Ce)-doped silicon oxides were deposited by electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD). Silicon nanocrystals (Si-ncs) were formed in the silicon-rich films during certain annealing processes. Photoluminescence (PL) properties of the films were found to be highly dependent on the deposition parameters and annealing conditions. We propose that the presence of a novel sensitizer in the Tb-doped oxygen-rich films is responsible for the indirect excitation of the Tb emission, while in the Tb-doped silicon-rich films the Tb emission is excited by the Si-ncs through an exciton-mediated energy transfer. In the Ce-doped oxygen-rich films, an abrupt increase of the Ce emission intensity was observed after annealing at 1200∘C. This effect is tentatively attributed to the formation of Ce silicate. In the Ce-doped silicon-rich films, the Ce emission was absent at annealing temperatures lower than 1100∘C due to the strong absorption of Si-ncs. Optimal film compositions and annealing conditions for maximizing the PL intensities of the rare earths in the films have been determined. The light emissions from these films were very bright and can be easily observed even under room lighting conditions.

Deposition of Ge-doped silica thin films for an integrated optic application using a matrix distributed electron cyclotron resonance PECVD reactor

Optical quality Ge-doped SiO2 thin films, suitable for an integrated optic version of a gain equalizer for erbium-doped fibre amplifiers (EDFAs), have been deposited using a matrix distributed electron cyclotron resonance plasma-enhanced chemical vapour deposition (MDECR-PECVD) system. Using spectroscopic ellipsometry and infrared transmission spectroscopy, the optical constants and hydroxyl content of the films were calculated. Losses due to the hydroxyl overtone at 1.37μm are found to be approximately 0.251dB/cm. An RBS analysis determined the germanium content of the films to be in the vicinity of 4 at.%. A comparison of the atomic percentage of germanium in the films and their corresponding refractive indices with values obtained using other deposition methods is also discussed.

Large-grained poly-silicon thin films by aluminium-induced crystallisation of microcrystalline silicon

Al-induced crystallisation of microcrystalline Si (μc-Si:H) thin films prepared by electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) on SiO 2-coated Si wafers has been studied. The starting structure was substrate/μc-Si:H/Al. Annealing this structure at a temperature of 520 °C resulted in successful layer exchange and the formation of a substrate/Al+Si layer/poly-Si geometry. Grain sizes exceeding ∼60 μm have been achieved in films displaying a preferential (1 0 0) orientation. The length of time the samples are kept under ambient conditions before annealing plays a key role in controlling grain size and orientation. It is likely that this time delay influences the formation of the interface between the Si and Al layers and, hence, the crystallisation process. These poly-Si layers exhibit an average surface roughness ( R a) generally in the range ∼7–12 nm.