Hydrogen Local Vibrational Modes in Zinc Oxide

Abstract

Using Raman backscattering spectroscopy we have observed six local vibrational modes in as-grown state-of-the-art nominally undoped zinc oxide single crystals. The local vibrational modes are located at $\nu =2854$, 2890, 2918, 2948, 2988, and $3096{\mathrm{c}\mathrm{m}}^{-1}$. Some specimens were annealed up to $950°\mathrm{C}$ to remove hydrogen. A subsequent Raman backscattering measurement revealed that the local vibrational modes disappeared. This establishes that the observed local vibrational modes are caused by the presence of hydrogen in the ZnO crystals.