Isotopic ZnO thin films were deposited on the c-plane of ZnO single crystals by pulsed laser deposition. The isotopic abundance of Zn in the films was determined with a secondary ion mass spectrometry before and after the films was diffusion annealed. The diffusion profiles across the film/substrate interface behaved smooth features. The zinc diffusion coefficient (DZn) was obtained by analyzing the slope of the profile in the annealed sample. The temperature dependence of DZn was determined to be DZn(cm2/s)=8.0×104exp(−417[kJ/mol])/RT, where R and T are gas constant and temperature. The zinc ion diffusion coefficients were of the same order as that in a ZnO single crystal. A comparison of the experimental and theoretical values indicated that the zinc ions diffused in the thin film and the single crystal through a vacancy mechanism.Highlights► Isotopic ZnO thin films were deposited on the c-plane of ZnO single crystals by pulsed laser deposition. ► Zinc diffusion profiles across the film/substrate interface behaved smooth features. ► The diffusion coefficients of Zn in thin film were in good agreement with those in single-crystal. ► The zinc ions diffused across the interface between the thin film and the single crystal via a vacancy mechanism.

Zinc self-diffusion along the growth direction was analyzed for the isotopic multilayer ZnO thin film ((64ZnO/68ZnO)664ZnO) deposited by pulsed laser deposition. The isotopic distribution was measured using a secondary ion mass spectrometry. The amplitude of the 64Zn abundance in the depth profile was reduced by annealing at 993 K for several hours due to interdiffusion between the 64ZnO and 68ZnO layers. The diffusion profiles at the isotopic interfaces were analyzed using a periodic equation. The obtained zinc self-diffusion coefficients at several isotopic interfaces along the growth direction showed that the self-diffusion coefficients increased towards the film/substrate interface. A similar trend was also found in the lateral direction. The variation among the self-diffusion coefficients was related to the film thicknesses at the analysis positions. Since zinc self-diffusion is controlled by a vacancy-mediated mechanism, the variation in zinc diffusivity along the growth direction can be attributed to the effect of compressive biaxial stress. These findings are useful for producing high-quality ZnO devices.

ZnO thin films were deposited on a-plane alumina by electron cyclotron resonance-assisted CVD method at several substrate temperatures. The crystal orientation of ZnO thin film strongly depended on the substrate temperature. The full width at half maximum of (002) rocking curve improved from 7° of ZnO film deposited at 300 °C to 0.4° of that deposited at 600 °C. The hydrogen impurity in ZnO thin film decreased with increasing the substrate temperature. The behavior of hydrogen impurity is related with the degree of c-axis orientation.