Structural, optical and DC conduction studies on vacuum evaporated Sr doped BaTiO_3 (BST) thin films prepared from Sr doped BaTiO_3 nano particles

摘要

Barium titanate (BaTiO_3) doped with Strontium (BST) nanoparticles prepared by using wet chemical method were thermally evaporated on to well cleaned glass substrates under the vacuum of 2 ×10~(-5) torr, using 12A4 Hind Hivac coating unit. The structure, optical and electrical properties of the deposited BST thin films were studied using the X-ray diffraction (XRD), optical transmittance and current-voltage measurements. The thickness of the film was measured by quartz crystal monitor. From X-ray analysis, it has been found that BaTiO_3 nanoparticles possess tetragonal structure and the deposited films were polycrystalline in nature, whereas the crytstallinity increases with increase of thickness. The extinction coefficient of the BST thin films decreases and on the other hand, refractive index increases with increasing thickness. The optical band gap energy value decreases with increase of film thickness. In the DC conduction studies, the Current-Voltage characteristics of the films showed ohmic conduction in the low field region. The conduction mechanism was found to be Poole-Frenkel at high field region. The activation energy values were estimated and were found to be decreasing with increasing applied field. The zero field value of the activation energy was found to be 0.28 eV.