Interstitial molecular hydrogen and deuterium in PECVD and HW amorphous silicon

For many years it has been known that high quality plasma-enhanced chemical vapor deposition (PECVD) hydrogenated amorphous silicon contains small quantities (less than or equal to 100 ppm) of molecular hydrogen in microvoids. More recently it has been demonstrated that there exist major (10-40%) molecular hydrogen populations singly trapped as interstitials in the amorphous equivalents of tetragonal T sites of the a-Si network. Comparative NMR studies have shown that a substantial fractional molecular hydrogen population residing in T sites correlates well with high photovoltaic quality as measured by film's mobility-life time product etamutau. Now, our current NMR measurements have turned to H-1-Si-29 double resonance experiments in hot wire amorphous silicon films (HW a-Si:H). Our HW a-Si:H films have been provided by Schropp and Branz and the PECVD films by Paul. The HW films show several resolved proton NMR components at 80 and 300 K. These components include a narrow line arising from molecular hydrogen resident in T-like sites and perhaps also in voids, A second broader line reflects clusters of Si-bonded H. A third superbroad (similar to80 kHz FWHM) line also is present as is a diamagnetically shifted feature. (C) 2002 Elsevier Science B.V. All rights reserved.