Microstructure and cation distribution of Mn2-xAlxZn0.2Ni0.6Mg0.2O4 high entropy oxide films

Mn2-xAlxZn0.2Ni0.6Mg0.2O4 (0 < x < 1) high entropy oxide films were prepared on Si substrates using two-step processing method. The effects of Al doping on the microstructure, cation distribution, optical and electrical properties of the films were investigated. It is revealed that rows of micro-holes form during the high-temperature oxidation reaction of metal multilayers in air. Al3+ mainly replaces Mn3+ in octahedron, while it does not affect the distribution of Mn4+ in octahedrons as well as that of other divalent cations in tetrahedrons. With the change of Al/Mn cation content, the thermal constant of the films increase from 3096.8 to 3615.8 K. When x = 0.4, the ion concentration of Mn3+/Mn4+ is closest to 1, and the electrical performance is optimal. The films with minor addition of Al exhibit high refractive index values in visible and infrared band (over 1150 nm wavelength), more Al and less Mn in the films degrade their optical properties.