Dielectric and optical properties of samarium oxide thin films

Samarium sesquioxide thin films were prepared by vacuum evaporation. Their structural and optical properties have been obtained by X-ray diffractometry (XRD) and optical spectrophotometry. The energy dispersion X-ray fluorescence (EDXRF) spectroscopy method was used to study the composition of the deposited Sm2O3 films. Spectroscopic optical absorption coefficients alpha(lambda) are evaluated in the interband transition energy region. The obtained energy gap was 4.33 eV. Thin film capacitors of Al/Sm2O3/Al structure have been prepared. The dc current-voltage characteristics of the capacitor showed that the current transfer is via Schottky emission at high fields (E>1 MV/cm). The leakage current density was 6 x 10(-7) A/cm(2) at an electric field of 10(6) V/m. The near electrode region (NER) has an effective dielectric constant of 42.7 according to Schottky current formula. The dielectric properties such as capacitance, ac conductance and dielectric loss factor were investigated as a function of bias voltage, temperature and frequency in the range from 60 Hz to 100 kHz. The measurements were performed in air at various temperatures in the range from 297 to 483 K. The frequency dependence of capacitance and conductance are consistent with the 'universal dielectric response law' with exponent s = 0.6 at room temperature. The frequency behavior of the dielectric properties can be explained according to the dipoles-dipole interaction and screening effect. The behavior of temperature dependence of ac conductivity suggests two competing hopping mechanisms with dominating activation energies of 0.01 eV at low-temperature range and of 0.04 eV at high-temperature range. (C) 2003 Elsevier B.V. All rights reserved.