Rational concept for fully designing metal-oxynitride films through reactive gas-timing magnetron sputtering: A case study on zinc oxynitride film

Abstract

Amorphous metal-oxynitride films—particularly zinc oxynitride (ZnON)—are emerging as promising materials for next-generation high-speed switching electronics, due to the absence of a potential barrier above the conduction band, unlike metal-doped ZnO. However, conventional reactive magnetron sputtering often face challenges in precisely controlling in an anion ratio, N/(N + O), because of the different reactivities of nitrogen and oxygen gases. In this work, we present a strategy to precisely control both the crystal structure and N/(N + O) ratio in ZnON films using a reactive gas-timing technique. By adjusting the oxygen gas-timing sequence (tO₂), we selectively induce different crystalline phases, which are closely related to the nitridation and oxidation of the sputtered Zn atom/cluster. This technique facilitates effective N incorporation into ZnO, enabling a broad range of N/(N + O) ratios from 0.048 to 0.964 and optical band gap variations from 1.49 eV to 3.22 eV. At an optimal tO₂, an amorphous phase is formed, attributed to a balanced nitridation and oxidation rate of the sputtered Zn atom/cluster that suppresses crystallization. The resultant amorphous ZnON film exhibits a high carrier mobility of 84.81 cm²/Vs, which is 1.16-fold and 35.89-fold greater than those of the cubic and hexagonal ZnON films, respectively. Our findings highlight the effectiveness of the reactive gas-timing technique as a powerful tool for the rational design of metal-oxynitride films, paving the way for their application in advanced electronic devices.