American Physical Society, Physical review B, 11(78)
DOI: 10.1103/physrevb.78.113203
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Current controversy on the binding sites of H(+) in ZnO can be explained by first- principles calculations. Previous infrared measurements from different groups indicate different H sites, either at the bond center (BC) site with a stretch frequency omega=3611 cm(-1) or antibonding (AB) site with omega=3326 cm(-1). This was puzzling because the BC site has lower energy by 0.2 eV. Here, we show that calcium, isovalent to Zn and found only in samples with the 3326 cm(-1) mode, binds H at the AB site. Large spatial undulation of charge explains the unexpected large binding between isovalent Ca and charged H(+) of 0.7 eV.