XPS Depth Profile Analysis of Zn₃N₂ Thin Films Grown at Different N₂/Ar Gas Flow Rates by RF Magnetron Sputtering

Zinc nitride thin films were grown on fused silica substrates at 300 °C by radio frequency magnetron sputtering. Films were grown at different N₂/Ar flow rate ratios of 0.20, 0.40, 0.60, 0.80, and 1.0. All the samples have grain-like surface morphology with an average surface roughness ranging from 4 to 5 nm and an average grain size ranging from 13 to16 nm. Zn₃N₂ samples grown at lower N₂/Ar ratio are polycrystalline with secondary phases of ZnO present, whereas at higher N₂/Ar ratio, no ZnO phases were found. Highly aligned films were achieved at N₂/Ar ratio of 0.60. Hall effect measurements reveal that films are n-type semiconductors, and the highest carrier concentration and Hall mobility was achieved for the films grown at N₂/Ar ratio of 0.60. X-ray photoelectron study was performed to confirm the formation of Zn-N bonds and to study the presence of different species in the film. Depth profile XPS analyses of the films reveal that there is less nitrogen in the bulk of the film compared to the nitrogen on the surface of the film whereas more oxygen is present in the bulk of the films possibly occupying the nitrogen vacancies.