Impact of the RF Power on the Copper Nitride Films Deposited in a Pure Nitrogen Environment for Applications as Eco-Friendly Solar Absorber

Abstract

This material can be considered to be an interesting eco-friendly choice to be used in the photovoltaic

field. In this work, we present the fabrication of Cu3N thin films by reactive radio-frequency

(RF) magnetron sputtering at room temperature, using nitrogen as the process gas. Different RF

power values ranged from 25 to 200Wand gas pressures of 3.5 and 5 Pa were tested to determine

their impact on the film properties. The morphology and structure were exhaustively examined

by Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) and Raman Spectroscopies

and X-ray Diffraction (XRD), respectively. The AFM micrographs revealed different morphologies

depending on the total pressure used, and rougher surfaces when the films were deposited at the

lowest pressure; whereas FTIR and Raman spectra exhibited the characteristics bands related to the

Cu-N bonds of Cu3N. Such bands became narrower as the RF power increased. XRD patterns showed

the (100) plane as the preferred orientation, that changed to (111) with the RF power, revealing a

worsening in structural quality. Finally, the band gap energy was estimated from transmission spectra

carried out with a Perkin Elmer 1050 spectrophotometer to evaluate the suitability of Cu3N as a light

absorber. The values obtained demonstrated the capability of Cu3N for solar energy conversion

applications, indicating a better film performance under the sputtering conditions 5.0 Pa and RF

power values ranged from 50 to 100 W.