Influence of bias voltage on optical and structural characteristics of Cu3N films deposited by reactive RF magnetron sputtering in a pure nitrogen atmosphere

Abstract

Copper nitride (Cu3N) thin films were deposited on Soda-lime glass substrates by reactive radio-frequency (rf) magnetron sputtering in a pure nitrogen ambient, with different bias voltages (i.e., 0, 50, 150 and 250 V) applied to the substrate holder. The effects of DC bias voltage on the structural, morphological and optical properties of the Cu3N thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectra show the single-phase polycrystalline structure of Cu3N with (100) preferential orientation. Moreover, the grain sizes, ranging from 36 nm to 19 nm, decreases with the increase in the substrate bias voltage. The AFM images show that the films become more uniform with the increase in bias voltage. Using the Tauc plot, the optical band gaps of the films were calculated, ranging from 0.71 to 1.42 eV. Furthermore, the indirect optical band gap and the optical transmittance increase with the increase in the bias voltage. The PL spectroscopy shows a shift to the lower wavelength associated with an increase in the bias voltage.