Variations of interface potential barrier height and leakage current of (Ba, Sr)TiO3 thin films deposited by sputtering process

Abstract

Variations of the leakage current behaviors and interface potential barrier height (ΦB) of rf-sputter deposited (Ba, Sr)TiO3 (BST) thin films with thicknesses ranging from 20 nm to 150 nm are investigated as a function of the thickness and bias voltages. The top and bottom electrodes are dc-sputter-deposited Pt films. ΦB critically depends on the BST film deposition temperature, postannealing atmosphere and time after the annealing. The postannealing under N2 atmosphere results in a high interface potential barrier height and low leakage current. Maintaining the BST capacitor in air for a long time reduces the ΦB from about 2.4 eV to 1.6 eV due to the oxidation. ΦB is not so dependent on the film thickness in this experimental range. The leakage conduction mechanism is very dependent on the BST film thickness; the 20 nm thick film shows tunneling current, 30 and 40 nm thick films show Schottky emission current.