Physical Properties of Copper Nitride Thin Film Deposited Using Reactive DC Magnetron Sputtering for Photodetection

Copper nitride thin films have been expected to be used in photodetection applications. In this work, copper
nitride films were deposited on glass substrates using a reactive DC magnetron sputtering process with the
voltage from 250 V to 350 V at room temperature. The high purity of copper target was used and the ratio of
gas flow rates, N₂/(N₂+Ar), were 0.86 and 1.00. The film thickness of 100 nm was controlled by a quartz crystal monitor during the deposition process. After deposition, the four-point probe measurement was used for the sheet resistance characterization. The optical properties and the structural properties were investigated using UV-Vis spectrophotometer and X-ray diffractometer. For all sputtering voltage, all XRD spectra can be fitted with the diffraction patterns of Cu₃N. In the case of a N₂/(N₂+Ar) ratio of 0.86, the sheet resistance decreased from about 106 ohm/sq to 102 ohm/sq as increasing the voltage from 250 V to 350 V. The optical energy bandgap was extrapolated using the standard Tauc plot technique from transmittance spectra of Cu₃N thin films. The optical energy bandgap varied from 1.26 eV to 1.62 eV. The N₂/(N₂+Ar) ratio of 1.00 lowered the optical energy bandgaps of all samples for all sputtering voltages. The variation of the optical energy band gap resulting from the sputtering parameters may be useful for band gap adjustment and band gap alignment in electronic device applications. Finally, both optical properties and electrical properties of Cu₃N thin films from this process can be a potential candidate for future photodetection devices.