T-Site-Trapped Molecular Hydrogen in a-Si:H

Proton-29Si double resonance NMR measurements on high quality plasma-enhanced chemical vapor deposition a-Si:H deposited from SiH4 show that more than one third of the contained hydrogen is present as H2 molecules residing in the amorphous equivalent of T sites. The NMR signal from these trapped H2 appears in the narrow 4 kHz proton line, which arises from the less clustered hydrogen population. Very little of the molecular component is in the broad ~24 kHz line, which arises mostly from clustered hydrogen tightly bonded to silicon.