Growth of ZnO Thin Films on LiNbO₃ Substrates by Electron Cyclotron Resonance-Assisted Molecular Beam Epitaxy

In this paper, we describe the growth of high-quality ZnO heteroepitaxial films on LiNbO 3 (0001) substrates by electron cyclotron resonance-assisted molecular beam epitaxy (ECR-assisted MBE). The quality of these films is analyzed by means of X-ray diffraction, pole figure of X-ray diffraction, and reflection high-energy electron diffraction (RHEED). The FWHM value of the (002) rocking curve for the 0.3-µm-thick films grown at 250°C was 0.45°. The pole figure of X-ray diffraction studies revealed that the films were epitaxial with a 30° rotation of the unit cell with respect to LiNbO 3 in the (0001) basal plane. The lattice mismatch between [1210]ZnO and [1100]LiNbO 3 was about 8.3%, which is smaller than that (∼16%) of ZnO film on sapphire (0001) that is widely used as a substrate. The growth of ZnO films on interdigital transducers (IDTs)/LiNbO 3 was also studied. The films deposited over the bare LiNbO 3 area between finger electrodes were single crystalline, while the films deposited over the Cr-Au finger electrodes were polycrystalline.