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

Polycrystalline zinc nitride (Zn3N2) thin films are prepared by reactive rf magnetron sputtering with different N2 concentrations in sputtering gases (N2–Ar mixtures). Structure and chemical bonding states are measured with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Single phase Zn3N2 film formation and texture strongly depend on N2 concentration. Polycrystalline Zn3N2 films are formed at N2 concentrations over 20% and show a 100 preferred orientation. The XPS N 1s peak (395.8 eV) for Zn3N2 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 Zn3N2 from XPS measurements. This value is significantly different from the values for ZnO and metallic zinc. The polycrystalline Zn3N2 films show a high electron mobility of about 100 cm2 V−1 s−1 at room temperature. Zn3N2 is determined to be an n-type semiconductor with direct gap of 1.23±0.02 eV.