Interface potential barrier height and leakage current behavior of Pt/(Ba, Sr)TiO3/Pt capacitors fabricated by sputtering process

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Abstract
Variations of the leakage current behaviors and interface potential barrier height (φ B ) of rf-sputter deposited (Ba, Sr)TiO3 (BST) thin films, with thickness ranging from 20nm 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. φ B 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 φ B from about 2.4 eV to 1.6eV due to the oxidation. φ B 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 20nm thick film shows tunneling current, 30 and 40 nm thick films show Schottky emission current and the thicker films show a mixed characteristics and bulk and interface limited currents although the mechanism is not clearly understood at this moment.