Charge states of a hydrogen defect (3326 cm line) in ZnO

The hydrogen defect in ZnO that gives rise to a local vibrational mode at 3326 cm⁻¹ is investigated by means of IR absorption. Sub-band gap illumination results in the appearance of a new line at 3358 cm⁻¹ at the expense of the 3326 cm⁻¹ signal. The measurements identify both IR absorption signals as O–H stretch modes of the same defect in different charge states. The effect of the sub-band gap light strongly suggest that this defect has a deep level in the band gap. Additionally, results on the thermal stability of the 3326 cm⁻¹ feature are presented.