Characteristic features of the IR spectra of amorphous boron-doped hydrated silicon

Vibrational modes with wave numbers 1879 and 1848 cm−1, previously observed only in the spectra of crystalline diborane, were observed in the optical spectra of a-Si:H(B) films. This indicates formation of complexes and bonds similar to those present in diborane, specifically, bridging hydrogen in the amorphous network. The change in the amplitudes of the observed modes after the films are annealed is attributed to structural rearrangements resulting in a decrease in the density of weakly bound bridging hydrogen and an increase in the density of quadruply coordinated boron. This explains the previously observed increase in the conductivity of annealed films.