Effects of plasma processing on the microstructural properties of silicon powders

The effects of plasma processing conditions on the microstructural properties of silicon powders are presented. Hydrogenated nanophase silicon powders were prepared using low-pressure and low-temperature square wave modulated RF plasma (13.56 MHz) using pure silane gas. Plasma parameters such as pressure, RF power, plasma modulation frequency, and gas flow rate were varied. In situ analysis by quadrupolar mass spectroscopy and ex situ analysis of the silicon powders by Fourier transform infrared spectroscopy (FTIR) and thermal desorption spectrometry of hydrogen were performed. The thermal desorption spectrometry results show the fundamental differences between the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon films. The FTIR analysis also determined the microstructural characteristics of powders and hence their volume/surface ratio. This parameter was determined from the balance of Pj probabilities of having one of the Hj-Si-Si4-j bond arrangements in the powder particles. These results reveal an increase in hydrogen content and a reduction in volume/surface ratio as the modulation frequency of RF power increases. In consequence, higher compactness of silicon powders is associated with long particle residence times inside the plasma as a result of ion bombardment. TEM analysis indicated a considerable dispersion of particle size and some degree of structure of the silicon powder characterized by intergrain linkage. We point out the dominant presence of hydrogen on the particle surfaces (external voids), which may cause the high reactivity of grains, increasing the degree of intergrain linkage.

[1]  Jonathan P. Williams,et al.  Growth and morphology of carbon grains , 1993 .

[2]  A. Howling,et al.  Negative hydrogenated silicon ion clusters as particle precursors in RF silane plasma deposition experiments , 1993 .

[3]  Enric Bertran,et al.  Microstructural and Vibrational Characterization of the Hydrogenated Amorphous Silicon Powders , 1993 .

[4]  M. Shiratani,et al.  Observation of growing kinetics of particles in a helium‐diluted silane rf plasma , 1992 .

[5]  Enric Bertran,et al.  Properties of amorphous silicon thin films grown in square wave modulated silane rf discharges , 1992 .

[6]  A. Bouchoule,et al.  Measurements of particle size kinetics from nanometer to micrometer scale in a low‐pressure argon‐silane radio‐frequency discharge , 1992 .

[7]  Enric Bertran,et al.  Production of Silicon Powder by Square-Wave Modulated Rf Silane Plasma , 1992 .

[8]  P. J. Paris,et al.  Direct Visual Observation of Powder Dynamics in Rf Plasma-Assisted Deposition , 1991 .

[9]  Enric Bertran,et al.  Influence of pressure and radio frequency power on deposition rate and structural properties of hydrogenated amorphous silicon thin films prepared by plasma deposition , 1991 .

[10]  David B. Graves,et al.  Particle thermophoresis in low pressure glow discharges , 1991 .

[11]  Enric Bertran,et al.  Ellipsometric study of a-Si:H thin films deposited by square wave modulated rf glow discharge , 1991 .

[12]  M. Shiratani,et al.  Powder‐free plasma chemical vapor deposition of hydrogenated amorphous silicon with high rf power density using modulated rf discharge , 1990 .

[13]  Joseph T. Verdeyen,et al.  Modulated discharges: Effect on plasma parameters and deposition , 1990 .

[14]  Davidson,et al.  Effects of the nearest neighbors and the alloy matrix on SiH stretching vibrations in the amorphous SiOr:H (0 , 1989, Physical review. B, Condensed matter.

[15]  Enric Bertran,et al.  Real time controlled rf reactor for deposition of a-Si:H thin films , 1989 .

[16]  J. Verdeyen,et al.  Enhancement of the negative ion flux to surfaces from radio‐frequency processing discharges , 1989 .

[17]  M. Shiratani,et al.  Effects of low‐frequency modulation on rf discharge chemical vapor deposition , 1988 .

[18]  G. Lucovsky.  Local bonding of hydrogen in a-Si:H, a-Ge:H and a-Si, Ge:H alloy films , 1985 .

[19]  W. Beyer,et al.  Reinterpretation of the silicon-hydrogen stretch frequencies in amorphous silicon , 1983 .

[20]  D. Aspnes.  Optical properties of thin films , 1982 .

[21]  W. Paul.  Dissent from the dihydride model of the vibrational spectra of amorphous silicon-hydrogen alloys , 1980 .

[22]  Armand Hadni,et al.  Essentials of modern physics applied to the study of the infrared , 1967 .