The annealing effect for structural, optical and electrical properties of dysprosium-manganese oxide films grown on Si substrate

Samples of (Dy-Mn) oxide thin films were prepared on quartz and Si(p) Substrates for optical and electrical investigations. These samples were annealed at different temperatures and characterised by UV-VIS absorption spectroscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The XRF spectrum was used to determine the weight fraction ratio of Mn to Dy in the prepared samples. The XRD shows that Dy oxide and Mn oxide prevent each other to crystallise alone or making a solid solution even at 600 degrees C. However, compound of DyMnO3 was formed through the solid-state reaction for T > 800 degrees C. The ac-conductance and capacitance were studied, as a function of frequency and gate voltage and the fixed and interface charge densities were determined. It was found that the "correlated barrier hopping" CBH model controls the frequency dependence of the conductivity, while the Kramers-Kronig (KK) relations explain the frequency dependence of the capacitance. The parameters of CBH model were determined and show that the ac-conduction in crystalline (Dy-Mn) oxide is realised by bipolaron mechanism, where the barrier height of hopping is equal to the bandgap determined the UV-VIS absorption spectroscopy. (C) 2005 Elsevier Ltd. All rights reserved.