Biepitaxial Growth of High-Quality Semiconducting NiO Thin Films on (0001) Al2O3 Substrates: Microstructural Characterization and Electrical Properties

Abstract

This paper reports the effects of substrate temperature on the microstructural characteristics and electrical properties of p-type semiconducting NiO thin films grown on (0001) Al2O3 substrates. NiO thin films were biepitaxially grown on (0001) Al2O3 substrates by radiofrequency magnetron sputtering, and they showed specific crystallographic orientation relationships: [110]NiO∥[0110]Al2O3, [112]NiO∥[2110]Al2O3 (in-plane), and [111]NiO∥[0001]Al2O3 (out-of-plane). Thus, a low lattice mismatch of 7.52% was obtained between the NiO thin films and the (0001) Al2O3 substrates. The film grown at 600 °C consisted of cubic and rhombohedral NiO grains, while the NiO thin films grown at substrate temperature below 400 °C only consisted of cubic NiO grains. Atoms at the grain boundaries between the cubic and the rhombohedral NiO grains perfectly coincided with each other because of the same atomic stacking sequences along [111]c-NiO and [0003]r-NiO and with equal interatomic distances. Further, the paper d...