Hyperfine studies of dangling bonds in amorphous silicon

Dangling-bond electron-spin hyperfine spectra have been measured in ${}_{}{}^{29}{}_{}{}^{}\mathrm{dilute}$ and ${}_{}{}^{29}{}_{}{}^{}\mathrm{enriched}$ a-Si:H. From the data we deduce that the electron wave function is largely p-like and has 50–80 % of its density on the central atom with the remainder predominantly on at least one of the back-bonded neighbors. A significant degree of weak back bonding for most dangling-bond sites is invoked to explain the large hyperfine coupling to a back-atom nucleus. Hydrogen back bonding at the dangling-bond site is shown to be negligible.