Interfacial characteristics and dielectric properties of Ba0.65Sr0.35TiO3 thin films

Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) depth profiling data show that each element component of the BST film possesses a uniform distribution from the outermost surface to subsurface, but obvious Ti-rich is present to BST/Pt interface because Ti4+ cations are partially reduced to form amorphous oxides such as TiOx (x < 2). Based on the measurement of XPS valence band spectrum, an energy band diagram in the vicinity of BST/Pt interface is proposed. Dielectric property measurements at 1 MHz reveal that dielectric constant and loss tangent are 323 and 0.0095 with no bias, while 260 and 0.0284 with direct current bias of 25 V; furthermore, tunability and figure of merit are calculated to be 19.51% and 20.54, respectively. The leakage current density through the BST film is about 8.96 × 10− 7 A/cm2 at 1.23 V and lower than 5.66 × 10− 6 A/cm2 at 2.05 V as well as breakdown strength is above 3.01 × 105 V/cm.