IMF2017

BTO thin films are chemically substituted and processed as to generate and control point defects. Mn and Nb-doped BTO thin films were deposited by RF-sputtering. Their chemical, structural, optical, dielectric and electric properties were analyzed by Impedance spectroscopy in dependence on temperature, frequency and static electric field, X-Ray Diffraction, ex-situ and in-situ XPS, Ellipsometry and leakage currents measurements. At 100 kHz and 20 °C, Mn-doped films exhibit low dielectric losses around 1% and low relative permittivity around 300; whereas Nb-doped films exhibit higher values, 7% and 700 correspondingly. We observed the effect of doping in the Fermi level position (E_F). In fact, there is a difference of 0.6 eV between the E_F of Nb and Mn-doped BTO thin films. Moreover, we observed that the E_F in BTO: Mn thin films (300nm) is around 2.2 ± 0.1eV instead of 1eV, leading to the conclusion that the E_F in BTO is pinned by the Mn^3+/2+ defect level transition rather than that of Mn^4+/3+.The E_F observed by XPS correlates well with electrical measurements where BTO:Mn showed low current density whereas BTO:Nb showed higher current density at E_bias=100 kV/cm. In addition to this, we performed an interface experiment between STO: Nb single crystal and BTO: Mn thin film. We observed the evolution of the valence band maximum and the core levels of Sr, Ba, Ti and O in function of the film thickness, showing that E_F varies from 3.2 eV to 2.8 eV within few nanometers up to 120 nm.