Annealing effect on the structural, optical and electrical properties of Yb-Mn oxide thin films

Ytterbium-manganese oxide thin films were grown on quartz and p-type Si(1 0 0) substrates. The films were thermally annealed at different temperatures ranging from 400 to 1000 °C to agitate interdiffusion and thus initiate a solid-state reaction. The structural characterisation of the films was carried out by X-ray diffraction (XRD) and energy dispersion X-ray fluorescence (EDXRF). The XRD investigation on films at 400 °C reveals the beginning of Yb2O3 crystallisation and a film of nano YbMnO3 grains was formed at annealing at about 1000 °C. Mn oxide molecules were totally diffused for interaction with Yb and did not crystallise or granulate alone. The optical properties of the films were studied in wavelength range 200-2500 nm. The ac-conductance and capacitance as a function frequency were studied on samples made in form of metal/oxide film/Si MOS devices. It was found that the power-law dependence controls the frequency dependence of the ac-conductivity, while Kramers-Kronig (KK) relations explain the frequency dependence of the relative permittivity. The calculation shows that the ac-conduction in YbMnO3 film is realised by bipolaron hopping mechanism. Temperature dependence of dc-conduction was also studied.