Vibrational modes in electrodeposited amorphous silicon: FT-IR analysis

Infrared spectra of 13 samples of amorphous silicon bonded with hydrogen, fluorine and carbon, prepared by electrodeposition using a mixture of ethylene glycol and fluosilicic acid were analysed in the wave number region 4000-400 cm^–1 with a Fourier transform infrared spectrometer. Strong absorption peaks were observed at 1000 cm^–1 due to the SiF_x stretching mode. Small peaks were seen around 2300 and 640 cm^–1 due to SiH stretching and wagging modes of absorption. The number of bonded hydrogen atoms in the film deposited at 0.05 M, 50 mA cm^–2 was calculated to be 6.2579×10²¹ and 1.2302×10²⁰ atm cm^–3 using integrated absorption of the CH and SiH stretching modes, respectively. The absorption coefficient around the SiF_x stretch region was found to vary from 1300–2500 cm^–1 as the molarity of the electrolyte was increased. Binding energy shifts in X-ray photoelectron spectrum were used as a cross check to confirm the silicon bonding with carbon, hydrogen, oxygen and fluorine atoms. The absence of columnar growth in SEM photographs indicates no polysilane formation in the films.