Sub-micron ZnO:N particles fabricated by low voltage electrical discharge lithography on Zn3N2 sputtered films

This work analyzes the morphological, compositional and electrical modification of zinc nitride (Zn3N2) films through arc discharges produced by biasing a metal tip at a micrometric distance of the surface. Polycrystalline nitride layers are prepared by radio-frequency magnetron sputtering from a pure Zn target on glass substrates using N2 as working gas. Film properties after arc discharges are investigated by using scanning electron microscopy (SEM), ion beam analysis (IBA) techniques and four-probe resistivity measurements. Electrical discharge lithography performed at low bias voltages reveals as an effective mechanism to reduce resistivity by electrical breakdown of the thin oxide layer formed on top of the nitride. At higher voltages, electrical discharges along the scan increase nitride resistivity due to the severe modification of the structural properties. Additionally, compositional analysis reveals that nitrogen leaves the structure being replaced by ambient oxygen. This characteristic behavior leads to the formation of facetted submicron ZnO crystals whose size depends on the original Zn3N2 grain size and the probe voltage used. The excess of zinc forms self-assembled microstructures along the scan edge.