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 °C deposited films, whereas two traps located at 0.2 and 0.40 eV appear in 550 °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 film capacitors, having ohmic behavior at low voltage (6 V). 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.