Hydrogen bonding in amorphous silicon with use of the low-pressure chemical-vapor-deposition technique.

Abstract

Infrared spectroscopy, elastic-recoil detection analysis (ERDA), and hydrogen evolution have been used to carefully determine the hydrogen content of low-pressure chemically-vapor-deposited a-Si:H films. The amount of hydrogen and the bonding character can be easily varied by changing the deposition conditions. The stretching peaks at \ensuremath{\sim}2000 and \ensuremath{\sim}2100 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ have been deconvoluted and the integrals calibrated by means of ERDA. The results provide the exact calibration constants for both peaks, and the values for the dipole effective charge obtained so far are consistent with the theory. Hydrogen-effusion measurements show that it is fairly certain that the material presents a small amount of voids, if compared with plasma-deposited amorphous silicon, despite the fact that the \ensuremath{\sim}2100-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ peak can be detected in vibrational spectra. This result seems to confirm that the character of hydrogen bonding is not related to the amount of voids in the material. On the other hand, no presence of microcrystallites is detectable in Raman spectra and the sample quality, tested by means of photothermal-deflection spectroscopy, does not seem to depend on the relative strengths of the two stretching modes.