Comparison of ZnO thin films grown by pulsed laser deposition on sapphire and Si substrates

ZnO thin films were simultaneously deposited on sapphire(0 0 1) and Si(1 0 0) substrates at 500 °C by pulsed laser deposition. The films were characterized by atomic force microscopy, X-ray diffraction, Rutherford backscattering and transmission electron microscopy. The results showed that the ZnO film grown on sapphire had a smoother surface and smaller grain size, and exhibited a sharper X-ray diffraction peak with a smaller full width at half maximum compared to those on Si. Microstructural analysis revealed that an initial amorphous ZnO buffer layer was formed on Si substrate, while a polycrystalline buffer layer appeared between sapphire and the ZnO epilayer. Pole figure measurements show that the ZnO films on Si has a random orientation along the growth direction, while the ZnO thin films on sapphire shows in-plane alignment with azimuthally six-fold symmetry, indicating a higher crystalline quality and less threading dislocations.