Deposition-rate controlled nitrogen-doping into cuprous oxide and its thermal stability.

Abstract Cuprous oxide has important applications from photovoltaic devices to photocatalysis and nitrogen-doping can improve the p-type conductivity of cuprous oxide. Here, phase-pure cuprous oxide thin films are prepared by sputtering a copper target in the atmosphere of Ar, O 2 and N 2 with the sputtering pressure varying from 0.6 Pa–3.0 Pa. The samples deposited at 0.6 Pa is also annealed in the flow of Ar or Ar plus N 2. The results show that sputtering pressure below 1.0 Pa results in higher deposition rate and more nitrogen incorporation into cuprous oxide while sputtering pressure of 3.0 Pa leads to lower deposition rate and no nitrogen doping though the gas flow rates are the same. In nitrogen-doped Cu 2 O, nitrogen exists as β-N (atomic nitrogen), α-N 2 (-N=N-) and γ-N 2 (N N). Annealing completely removes β-N and partially turns α-N 2 into γ-N 2. Nitrogen-doped cuprous oxide has smaller resistivity and larger hole density than undoped samples. The longest time for the absorbed nitrogen molecules to stay on the copper position is estimated to be 8.45 × 10−7 s. Annealing has little effect on the electrical and optical properties of nitrogen-doped cuprous oxide though it induces a weak decomposition. Highlights • The nitrogen content in Cu 2 O was controlled by varying the sputtering pressure. • Lower sputtering pressure results in higher deposition rate. • Lower sputtering pressure favors the incorporation of nitrogen into Cu 2 O. • Lowering sputtering pressure increases the hole density. • Annealing at 400 °C results in little electrical and optical change. [ABSTRACT FROM AUTHOR]