Concentration-dependent behavior of hydrogen in Al-doped ZnO thin films

The Al-doped ZnO thin films were synthesized by aerosol-assisted chemical vapor deposition. The concentration-dependent behavior of hydrogen in the films was discussed, finding that as hydrogen is introduced at a relatively low level, it tends to take the oxygen vacancy site and form a hydrogen-oxygen vacancy complex which behaves as a shallow donor, on the other hand it reduces the solubility of the substitutional Al; then higher hydrogen concentration results in the formation of H2 neutral molecular complex.