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 degrees 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 degrees C reveals the beginning of Yb2O3 crystallisation and a film of nano YbMnO3 grains was formed at annealing at about 1000 degrees 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. (C) 2008 Elsevier B.V. All rights reserved.