²⁹Si hyperfine measurements in a-Si:H

From measured hyperfine spectra of ²⁹Si-dilute and enriched material we have deduced local information about the dangling bond in a-Si:H. The electron wavefunction 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 bonding is invoked to explain the relatively large hyperfine coupling to a back atom nucleus. Finally, hydrogen back-bonding at the dangling bond site is shown to be improbable.