We have investigated the hydride vapor-phase epitaxy growth of ͑101 ¯3 ¯͒-oriented GaN thick films on patterned sapphire substrates ͑PSSs͒ ͑101 ¯0͒. From characterization by atomic force microscopy, scanning electron microscopy, double-crystal X-ray diffraction, and photoluminescence ͑PL͒, it is determined that the crystalline and optical qualities of ͑101 ¯3 ¯͒ GaN epilayers grown on the cylindrical PSS are better than those on the flat sapphire. However, two main crystalline orientations ͑101 ¯3 ¯͒ and ͑112 ¯2͒ dominate the GaN epilayers grown on the pyramidal PSS, demonstrating poor quality. After etching in the mixed acids, these ͑101 ¯3 ¯͒ GaN films are dotted with oblique pyramids, concurrently lining along the ͗303 ¯2 ¯͘ direction, indicative of a typical N-polarity characteristic. Defect-related optical transitions of the ͑101 ¯3 ¯͒ GaN epilayers are identified and detailedly discussed in virtue of the temperature-dependent PL. In particular, an anomalous blueshift-redshift transition appears with an increase in temperature for the broad blue luminescence due to the thermal activation of the shallow level.

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Ni‐Si3N4 nanocomposite films with both the consecutive Ni crystallites and dispersed Si3N4 particles in the nanometer range have been fabricated using DC electroplating technique, and characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and X‐ray diffraction (XRD). The corrosion resistance of the Ni‐Si3N4 nanocomposite film has been compared to that of pure Ni coating through polarization. Meanwhile, the corrosion process of Ni‐Si3N4 nanocomposite film in neutral 3.5% NaCl solution has been investigated using electrochemical impedance spectroscopy (EIS). The results show that the Ni‐Si3N4 nanocomposite film is more resistant to corrosion than the pure Ni coating. The corrosion of Ni‐Si3N4 nanocomposite film is controlled by electrochemical step, and the whole corrosion process is divided into two sequential stages. The main corrosion type of Ni‐Si3N4 nanocomposite films in neutral 3.5% NaCl solution is pitting.

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