Local Vibrational Modes of Isolated Hydrogen in Germanium

Two distinct isolated hydrogen defects are observed in crystalline Ge by in situ infrared absorption spectroscopy. Implantation of protons into Ge at cryogenic temperatures gives rise to two intense absorption lines at 745 and $1794{\mathrm{cm}}^{-1\mathrm{}}$. The lines originate from distinct defects, each of which contains one H atom located on a $〈111〉$ axis. The $1794-{\mathrm{cm}}^{-1\mathrm{}}$ line is assigned to bond center H in the positive charge state, whereas the $745-{\mathrm{cm}}^{-1\mathrm{}}$ line is ascribed to negatively charged H located on a $〈111〉$ axis close to the tetrahedral site.