Anisotropic growth is observed for GaN(0001) during molecular beam epitaxy for both the stepflow growth mode and two-dimensional (2D) nucleation growth mode. Using scanning tunneling microscopy, we find that in the step-flow growth mode, growth anisotropy strongly influences the shape of terrace edges, making them strikingly different between hexagonal and cubic films. In the 2D nucleation growth mode, anisotropic growth results in triangularly shaped islands. The importance of understanding growth anisotropy to achieve better grown GaN films is discussed.

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Hafnium oxide (HfO2) thin film has remarkable physical and chemical properties, which makes it useful for a variety of applications. In this work, HfO2 films were prepared on silicon through plasma enhanced atomic layer deposition (PEALD) at various substrate temperatures. The growth per cycle, structural, morphology and crystalline properties of HfO2 films were measured by spectroscopic ellipsometer, grazing-incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR), field-emission scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. The substrate temperature dependent electrical properties of PEALD–HfO2 films were obtained by capacitance–voltage and current–voltage measurements. GIXRD patterns and XRR investigations show that increasing the substrate temperature improved the crystallinity and density of HfO2 films. The crystallinity of HfO2 films has a major effect on electrical properties of the films. HfO2 thin film deposited at 300 °C possesses the highest dielectric constant and breakdown electric field.