Sodium doping in ZnO crystals

摘要

ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to ＞6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 10~(17)cm~(-3). Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na_(Zn) level at ～(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.