Characterization of homoepitaxial and heteroepitaxial ZnO films grown by pulsed laser deposition

Homo- and heteroepitaxial ZnO films were grown on ZnO (0 0 0 1) and Al2O3 (1 1 ¯2 0) substrates by using pulsed laser deposition. The X-ray diffraction and Raman measurements for these films show good correspondence with the bulk ZnO substrate, which confirms successful growth of c-axis oriented ZnO layer. Strong UVemission was also observed in these films, indicating good optical quality. However, the surface roughness differs very much for the homo- and heteroepitaxial film, that is, much less for the homoepitaxial layer. Positron annihilation measurements reveal a higher vacancy concentration in the homoepitaxial layer