The optical and electrical properties of nitrogen-doped cuprous oxide annealed at different temperatures

Nitrogen atoms exist as nitrogen molecules in cuprous oxide doped with nitrogen and the thermal stability of nitrogen doping has not been studied. Here phase-pure cuprous oxide doped with nitrogen was prepared with a direct current magnetron sputtering system. The samples were then annealed at 400 °C in Ar or Ar plus N2 for 30, 60 and 90 min and the influence of annealing is studied. The results show that annealing results in the presence of metallic copper and the release of the tensile strain in the nitrogen-doped films. In nitrogen-doped cuprous oxide without annealing, nitrogen is found to exist as atomic nitrogen (β-N) and strongly chemisorbed π-bonded nitrogen molecules (α-N2). After annealing, atomic nitrogen (β-N) is absent and the strongly chemisorbed π-bonded nitrogen molecules (α-N2) partially turn into weakly chemisorbed nitrogen molecules (γ-N2). Annealing can improve the transmittance of about 550–750 nm and widen the forbidden gap. Annealing can change the hole density by changing the density of donor defects, and the density and types of nitrogen molecules doped into cuprous oxide.