Structure and Properties of a-Si: H: F Films Obtained by R.F. Glow-Discharge in SiH₄-F₂ Mixtures

Abstract

Amorphous Si: H: F films have been prepared by R.F. flow discharge in a SiH₄-F₂ mixture. A substantial fluorine incorporation was achieved, as found from Rutherford backscattering and infrared absorption spectra. New vibrational bands have been found at 1070 cm^-1 and 1170 cm^-1, which have been interpreted mainly in terms of SiH²F and SiHF² complexes, whose frequencies were calculated. Dark and photoconductivities have also been measured for films with and without fluorine. Both the incorporation of fluorine and an increase of the substrate temperature led to lower conductivity values and to a reduction in the density of gap states. The ratio between the photoconductivity and the dark conductivity was found to increase substantially with the incorporation of fluorine in the amorphous alloy.