Structural Features of Pseudomorphic Spinel-Structure Films on R-Sapphire Substrates

Abstract

А suspension of submicron ZnO crystallites in acetone is applied to epi-ready R(10\(\bar {1}\)2) sapphire plates with dimensions of ~10 × 10 × 0.5 mm. The composite is dried and annealed in air in a tube furnace at 1200°C for 60 min. According to the data of electron and scanning probe microscopy, X-ray and electron diffraction, thin oriented ZnAl₂O₄ zinc spinel films are formed on the sapphire substrate with the mutual orientation of lattices following the epitaxial relationships: (311)ZnAl₂O₄||(10\(\bar {1}\)2)Al₂O₃; 〈332〉ZnAl₂O₄||〈11\(\bar {2}\)0〉 Al₂O₃; 〈110〉ZnAl₂O₄||〈1\(\bar {1}\)01〉Al₂O₃. Due to the relatively high synthesis temperature of the films (1200°C) and the most intense cathodoluminescence of the film in the near-infrared (IR) spectrum, the formation of normal zinc spinel can be assumed. The obtained ZnAl₂O₄ films with the (311)-plane orientation parallel to the R plane of the sapphire substrate are supposed to be used to grow magnetic NiFe₂O₄ and CoFe₂O₄ films having the (311) plane with an easy-axis magnetization anisotropy oriented along the 〈311〉 direction.