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, O2 and N2 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 N2. 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 Cu2O, nitrogen exists as β-N (atomic nitrogen), α-N2 (-N=N-) and γ-N2 (NN). Annealing completely removes β-N and partially turns α-N2 into γ-N2. 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.