Electronic defect and trap-related current of (Ba0.4Sr0.6)TiO3 thin films

Abstract

By employing a deep level transient spectroscopy (DLTS) technique, this work investigates the deep trap levels of rf-sputtered (Ba0.4Sr0.6)TiO3 (BST) thin films deposited at various temperatures. Arrhenius plots of DLTS spectra detect a single trap located at 0.45 eV in 450 degrees C deposited films, whereas two traps located at 0.2 and 0.40 eV appear in 550 degrees C deposited films. On the other hand, examining the I-V characteristics of the films at the temperature range of 298-403 K reveals the presence of two conduction regions in the BST him capacitors, having ohmic behavior at low voltage (<1V) and Schottky-emission or Poole-Frenkel mechanism at high voltage (>6V). The barrier height and trapped level are, respectively, estimated to be 0.46 and 0.51 eV, corresponding to the trap activation energy 0.4-0.45 eV obtained from our DLTS measurements. Compared with previous published reports, the trap distributed at 0.4-0.5 eV should be an intrinsic defect of BST and possibly ascribed to be oxygen vacancies. Meanwhile, the trap plays a prominent role in the leakage current of BST films. (C) 1997 American Institute of Physics.