Produiion of a-Si_1-x C_x:H powders using radiofrequency glow discharges of silane and methane mixtures.

Abstract

ABSTRACTa-Si1-x Cx:H powders have been produced in radiofrequency glow discharges of SiH4 and CH4. Samples produced in discharges with different gas flow ratios (R=[CH4] / [SiH4]+[CH4], R ∼ 0.2 to 0.95) were analyzed by several techniques: Infrared spectroscopy, transmission electron microscopy and thermal desorption spectrometry of hydrogen. The microstructural properties of the a-Si1-x Cx:H powders obtained ranged between those previously reported in silicon particles and those of amorphous carbon particles. As a general rule, the particles, whose diameter ranged between 5 and 400 nm in diameter, showed an amorphous microstructure and high hydrogen content. Infrared spectroscopy showed that the hydrogen was mainly located on the particle surface and in microvoids forming CHi and/or SiHi (i=2,3) groups.The hydrogen was removed from the powder by thermal annealing (< 700°C) under vacuum. Anlysis of the a-Si1-x Cx:H powders after this thermal treatment revealed new microstructural and optical features.