Raman scattering in highly disordered amorphous phosphorus

Raman scattering measurements are presented on amorphous phosphorus ($a-\mathrm{P}$) films deposited by rf and dc sputtering under conditions that enhance structural disorder. This includes rf sputtering at increased substrate bias as well as dc sputtering employing in situ measurements on surfaces at 80 K. In addition, the influence of annealing on the Raman spectra has been studied. The experimental results indicate that substantial changes in the Raman spectra occur relative to more ordered rf sputtered $a-\mathrm{P}$ films prepared at high pressure. These changes, which are most noticeable in low-temperature dc sputtered films, are interpreted in terms of modifications of both intermediate- as well as short-range order. The results indicate that modifications of intermediate-range order are primarily manifest by changes in the Raman coupling parameters, whereas the most disordered films indicate broadening of the phonon density of states as well. The influence of changes in short-range order on the polarized Raman spectra is related to dynamical correlation effects.