Stability of the number of silicon-hydrogen bonds upon photoillumination of undoped amorphous hydrogenated silicon

Abstract

Deuteron magnetic resonance measurements on high quality a-Si:H,D films reveal three principal features: a sharp 66 kHz quadrupolar Pake doublet corresponding to silicon-bonded D passivating dangling bonds, a broad central line which has been shown to arise primarily from relatively isolated D 2 and HD molecules in nanovoids, and a small narrow central line arising from mobile molecular D 2 and HD in greater than 3 Å microvoids. The results of measurements on high quality plasma-deposited partially deuterated amorphous silicon cyclically exposed to a 2 h 150°C dark anneal and a 36 h photoillumination at 0.5 W/cm 2 with a 400–700 nm xenon are lamp are described. The spectra show that, following an initial spin-lattice relaxation-related transient, the intensities of all three components of the deuterium may vary by less than 1% upon illumination or dark anneal. The broad central line, primarily from isolated molecules, shows a small diamagnetic shift upon illumination. The shift becomes strongly paramagnetic at short magnetization recovery times following radio frequency saturation. The SiD doublet and the small narrow central line do not shift appreciably. This absence strongly suggests that Staebler-Wronski magnetic changes are remote from the environments of most of the silicon bonded hydrogen.