ZnO Film Growth on (0112)LiTaO3 by Electron Cyclotron Resonance-Assisted Molecular Beam Epitaxy and Determination of Its Polarity

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Abstract
Single-crystal ZnO films were grown on (0112)LiTaO3 substrates by electron cyclotron resonance-assisted molecular beam epitaxy (ECR-assisted MBE). The film orientation differed with the ratio of oxygen to zinc. Under oxygen-rich conditions, (1120)ZnO films with the c-axis parallel to the substrate surface were epitaxially grown. To identify the polarity of ZnO films with the c-axis parallel to the surface, a method using sideways chemical etching was proposed. The polarity of ZnO films was different when the films were grown on the + plane or the - plane of (0112)LiTaO3 substrates. The ZnO/LiTaO3 substrates offer a high electromechanical coupling factor of the shear horizontal-type leaky surface acoustic wave (SH-type leaky SAW) propagating along the X-axis due to an additional contribution of the piezoelectric shear effect of ZnO.