Interplay between interstitial and substitutional hydrogen donors in ZnO

A Raman study on hydrogen donors in ZnO reveals the properties of bond-centered hydrogen (H sub(BC)) and hydrogen trapped in the oxygen vacancy (H sub(O)). The donors are identified by their electronic 1s arrow right 2s(2p) transitions and their characteristic local vibrational modes. The H sub(O) donor was detected preferentially below the sample surface, where a high oxygen vacancy concentration is generated by thermal treatment of the samples. H sub(BC) and H sub(O) exhibit different thermal stabilities and their concentrations depend strongly on the sample history. Molecular hydrogen is an essential part of the interplay of the two hydrogen donors.