Structural, electrical and optical properties of zinc nitride thin films prepared by reactive rf magnetron sputtering

Abstract

Polycrystalline zinc nitride (Zn 3N 2) thin films are prepared by reactive rf magnetron sputtering with different N 2 concentrations in sputtering gases (N 2–Ar mixtures). Structure and chemical bonding states are measured with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Single phase Zn 3N 2 film formation and texture strongly depend on N 2 concentration. Polycrystalline Zn 3N 2 films are formed at N 2 concentrations over 20% and show a 100 preferred orientation. The XPS N 1s peak (395.8 eV) for Zn 3N 2 indicates a large chemical shift of 3.0 eV from the N 1s peak for free amine (398.8 eV) indicative of the formation of N–Zn bonds. Moreover, the modified Auger parameter, which is a good measure of the chemical state, is determined to be 2012.3 eV for Zn 3N 2 from XPS measurements. This value is significantly different from the values for ZnO and metallic zinc. The polycrystalline Zn 3N 2 films show a high electron mobility of about 100 cm 2 V −1 s −1 at room temperature. Zn 3N 2 is determined to be an n-type semiconductor with direct gap of 1.23±0.02 eV.