Proton-magnetic-resonance studies of microstructure in plasma-deposited amorphous-silicon—hydrogen films

Abstract

Proton-magnetic-resonance data are presented for twenty different plasma-deposited amorphous-silicon---hydrogen films. The two-phase compositional inhomogeneity observed in these films is found to be independent of film thickness down to less than 1 \ensuremath{\mu}m. Models for various structural configurations show that these films contain heavily monohydride-clustered regions such as vacancies and voids, as well as ${(\mathrm{Si}{\mathrm{H}}_{2})}_{n}$ and Si${\mathrm{H}}_{3}$ local bonding configurations. The films also contain regions in which monohydride groups are distributed at random. Based on changes in a film whose proton NMR line shapes are metastable as deposited, a model based on strain relief is proposed for film development which explains the ubiquitous presence of the two-phase inhomogeneity. Examination of the changes in proton NMR data as a function of deposition conditions furnishes new insight on the role Si${\mathrm{H}}_{2}$ and $\mathrm{Si}{{\mathrm{H}}_{x}}^{+}$ groups have in models for the gas-phase reactions involved in the developing films. Finally, $p$- or $n$-type doping is found to increase the hydrogen content of the films, and, under heavy $p$-type doping with diborane, boron clustering may occur within the films.