Deep level transient spectroscopy studies on BaTiO₃ and Ba_1-xCa_xTiO₃ thin films deposited on Si substrates

Abstract

Laser ablation grown BaTiO₃ and Ba_1-xCa_xTiO₃ thin films were studied in the metal-ferroelectric-semiconductor configuration by the deep level transient spectroscopy (DLTS) technique. The capture cross section, bulk and interface traps were determined from the DLTS technique. The distributions of calculated interface states were mapped with the silicon energy band gap for both the thin films. The interface states of the Ba_1-xCa_xTiO₃ thin films were found to be higher than the BaTiO₃ thin films. The substitution of Ca²⁺ into the Ba²⁺ sites of BaTiO₃ results in a decreased lattice constant, thereby leading to shrinkage in the unit cell. This might be one of the reasons for the higher density of interface states present in Ba_1-xCa_xTiO₃, as it leads to a large number of unsaturated bonds at the interface of Si substrate-thin films. The calculated capture cross section of the interface traps in both the BaTiO₃ and Ba_1-xCa_xTiO₃ thin films was very low in the range of 10^-21 cm².