Photoluminescent, wide-bandgap a-SiC:H alloy films deposited by Cat-CVD using acetylene (original) (raw)
Related papers
Solar Energy Materials and Solar Cells, 1994
Hydrogenated amorphous and microcrystalline silicon carbon alloy films have been grown by photo-CVD using C2H 2 as a source gas of carbon. The hydrogenated amorphous silicon carbon (a-SiC : H) film with a band gap of ~ 2.0 eV prepared at a very low hydrogen (LD) concentration exhibits better photo-electronic properties compared to that at high hydrogen dilution (HD) having a similar optical gap. Notwithstanding a high deposition rate, the high photosensitivity (~ 106), the low density of the defect states (~ 6 X 1016 cm -3) and the Urbach energy parameter (72 meV) for the a-SiC:H film prepared at low hydrogen dilution and pressure are impressive. On the other hand, low pressure along with high hydrogen dilution have been found to be conducive to microcrystalline silicon carbon alloy (/~c-Si:H) formation. Interestingly, crystallites are of silicon while carbon remains in the amorphous and grain boundary regions.
2007
Hydrogenated amorphous silicon carbide (a-SiC:H) films were prepared using a home-built plasma-enhanced chemical vapor deposition (PECVD) system with different flow rate ratios of methane (CH(4)) and silane (SiH(4)) gases. Fourier-transform infrared (FTIR) spectra indicate multiple bonding configurations consisting of wagging, bending and stretching modes of silicon, hydrogen and carbon atoms with a steady depletion of Si-H wagging and stretching modes as the gas flow rate ratio increases. Micro-Raman spectra show evidence of amorphous silicon structure in all the films. Only the a-SiC:H film prepared at the highest CH(4) to SiH(4) gas flow rate ratio shows the existence of the Si-C vibrational mode. All the samples prepared show room-temperature luminescence with two peaks centered at 467 and 698 nm. The photoluminescence (PL) intensity increases as the CH(4) to SiH(4) gas flow rate ratio increases but a reduction in intensity is observed for a high CH(4) to SiH(4) gas flow rate ratio. a-SiC:H films with higher optical energy gaps were obtained by allowing the gases to flow at higher CH(4) to SiH(4) gas flow rate ratios.
Journal of Alloys and Compounds, 1999
Two series of hydrogenated amorphous silicon carbide (a-SiC:H) films have been prepared by using plasma-enhanced chemical-vapor deposition (PECVD) with the gas mixture of methane (CH ) and silane (SiH ). The influence of the r.f. power density on the structural 4 4 and optical properties of the films has been investigated with the CH gas ratio in the total gas flow rate ranging from 50 to 90%. The r.f. 4 power density is an important parameter which affects both the carbon content and the structures of the films. Under high r.f. power condition, the samples are Si-rich and the structure of them is described as a disordered amorphous silicon network in which hydrogen 3 atoms are incorporated in the form of Si-CH and Si-CH entities and carbon atoms are in a sp carbon-related configuration. The 2 3
Properties of a-SiC:H films deposited in high power regime
Thin Solid Films, 2003
The aim of the present paper is the study of the RF power effects on the properties of hydrogenated amorphous silicon-carbon (a-SiC:H) films, deposited in high power regime in a conventional plasma enhanced chemical vapor deposition system by using silane-methane gas mixtures highly diluted in hydrogen. Varying the RF power chemically ordered a-SiC:H alloys can be grown controlling the carbon content, CywCqSix, and consequently the energy gap from 0.20 to 0.57 and 2.17 to 3.23 eV, respectively. C-rich films show defect density lower than 2=10 cm and photoluminescence (PL) at room temperature. The PL peak 17 y3 position of the spectra shifts from 1.70 to 2.54 eV as the carbon content increases from 0.3 to 0.57. ᮊ
Multiphase structure of hydrogen diluted a-SiC:H deposited by HWCVD
Materials Chemistry and Physics, 2006
The structural and optical properties of hydrogenated amorphous silicon carbon (a-SiC:H) thin films, grown from pure SiH 4 , C 2 H 2 and H 2 mixture by hot wire chemical vapor deposition (HWCVD) technique, were studied. Variable flow rates and other growth conditions were applied. A variety of techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, Raman scattering (RS), Atomic force microscopy (AFM), UV-VIS-NIR spectroscopy and photoluminescence (PL) were used to characterize the grown materials. The results confirmed coexisting of the multiphase structure of the grown a-SiC:H thin films: Si C network, carbon-like and silicon-like clusters. The room temperature (RT) PL shows a different result from the previous reports. It is suggested that both graphite-cluster phase and silicon cluster like phase are light-emitting grains. The two types of grains and Si C network are the origin of the PL in hydrogenated amorphous silicon carbide material.
Solid State Communications, 2005
Hydrogenated amorphous SiC thin films deposited at low substrate temperature (100 8C) show the different bonding configurations and microstructures which depend on the carbon concentrations in the films controlled by the gas ratio R of methane to silane during the deposition. Photoluminescence characteristics are investigated for these samples with different structures. A strong luminescence in red light region can be observed for samples deposited with low gas ratio R which is significantly reduced its intensity with increasing the carbon concentrations in the films. On the other hand, the luminescence bands located at blue-green light region are detected under UV light excitation for samples deposited with high gas ratio R, which can be associated with the existence of amorphous SiC clusters in the films. q
Journal of Applied Physics, 1997
a-SiC:H films with energy gap in the range 2.00-2.65 eV have been grown by plasma enhanced chemical vapor deposition in undiluted and H 2 diluted SiH 4 ϩCH 4 gas mixtures, by making use of optimized deposition conditions. A complete picture of structural, compositional, optoelectronic, and defective properties for high quality films has been drawn for the first time. We show that the addition of H 2 to the gas mixture leads to a different chemical composition of the deposited films; in particular, carbon incorporation is enhanced and a carbon fraction in the solid matrix up to C/͑CϩSi͒Ϸ0.45 can be obtained. These films have a higher mass density, a reduced microvoid and carbon cluster concentration, a better structural connectivity, and improved optoelectronic properties. For samples with optical gap below 2.4 eV, the reduced defect concentration of H 2 diluted films results in an increase of the photoconductivity gain and the steady-state () ss values up to two orders of magnitude.
Effect of H2 dilution on Cat-CVD a-SiC:H films
Thin Solid Films, 2006
Effect of hydrogen (H 2 ) dilution of the Silane (SiH 4 ), acetylene (C 2 H 2 ) gas mixture during the deposition of hydrogenated amorphous silicon carbon alloy (a-SiC:H) films by Cat-CVD process shows that the H 2 dilution induced additional carbon incorporation, leading to an increase of the carbon content in the films from 52% to 70% for the maximum H 2 dilution employed. A slight increase in graphitic carbon in the films deposited with H 2 dilution is also observed. A drastic increase in the optical band gap E g from 2.5 eV for zero dilution to 3.5 eV is observed for a H 2 dilution of 10 sccm. Raman spectra for the films deposited with increasing H 2 dilution indicate structural changes in the amorphous network associated with increasing graphitic carbon.
2013
A hot-wire chemical vapour deposition (HWCVD) system is a simple and cost-effective technique for deposition of Si-based films. Silicon carbide (SiC) on the other hand is a very interesting material with many unique properties. This work is directed towards understanding how the structural properties of the SiC films affect the opto-electronic properties of the films. This is important for application of this wide band gap semiconductor as a window material in photovoltaic solar cells. In this work, an HWCVD system built in the laboratory is successfully utilized to grow multi-phased SiC films from silane (SiH4) and methane (CH4) gases without hydrogen dilution. In the first part of this work, the influence of precursor gas concentration on chemical bonding, crystallinity and elemental composition of the films is studied. The precursor gas concentration is changed by depositing films at different CH4 flow-rates with the SiH4 flow-rate fixed at SiH4 starving condition and at differen...