Hydrogen local vibrational modes in zinc oxide

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 cm(-1). Some specimens were annealed up to 950 degreesC 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.