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Effect of post-annealing on the properties of copper oxide thin films obtained from the oxidation of evaporated metallic copper

2007; Elsevier BV; Volume: 254; Issue: 13 Linguagem: Inglês

10.1016/j.apsusc.2007.12.019

1873-5584

Vitor Figueiredo, E. Elangovan, G. Gonçalves, Pedro Barquinha, L. Pereira, N. Franco, E. Alves, Rodrigo Martins, Elvira Fortunato,

Electronic and Structural Properties of Oxides

Thin films of copper oxide were obtained through thermal oxidation (100–450 °C) of evaporated metallic copper (Cu) films on glass substrates. The X-ray diffraction (XRD) studies confirmed the cubic Cu phase of the as-deposited films. The films annealed at 100 °C showed mixed Cu–Cu2O phase, whereas those annealed between 200 and 300 °C showed a single cubic Cu2O phase. A single monoclinic CuO phase was obtained from the films annealed between 350 and 450 °C. The positive sign of the Hall coefficient confirmed the p-type conductivity in the films with Cu2O phase. However, a relatively poor crystallinity of these films limited the p-type characteristics. The films with Cu and CuO phases show n-type conductivity. The surface of the as-deposited is smooth (RMS roughness of 1.47 nm) and comprised of uniformly distributed grains (AFM and SEM analysis). The post-annealing is found to be effective on the distribution of grains and their sizes. The poor transmittance of the as-deposited films (<1%) is increased to a maximum of ∼80% (800 nm) on annealing at 200 °C. The direct allowed band gap is varied between 2.03 and 3.02 eV.