Electrical properties of amorphous barium titanate films sputter deposited under hydrogen containing atmosphere

Hydrogenated barium titanate films (a -BaTiO3:H) were grown by rf magnetron sputtering under hydrogen containing atmospheres. X-ray photoelectron spectroscopy and Fourier transform infrared analyses were carried out in order to get insight on composition and chemical bonds. Impedance spectroscopy was used to investigate the dielectric behavior at low-temperature range. The strong O-H stretch band (at around 3500 cm-1) evidenced in the infrared spectrum clearly manifests the presence of protons in the hydrogenated material. The incorporation of protons during the deposition of a -BaTiO3:H films hugely modifies their electrical properties. These films exhibit large capacitance that is hundred times higher than the one measured when the film is grown without hydrogen. On the other hand, the presence of positively charged protons can contribute to the conduction process by introducing two main features. The first is related to a significant migration of proton between adjacent oxygen sites with an activation energy of 0.37 eV. This behavior might be responsible for the high protonic conductivity depicted in our material at temperature higher than -30 °C. Furthermore, protons were shown to engender hydrogen bonds in the structure. As a result, the dielectric relaxation observed at temperature below -30 °C could be ascribed to the dissociation of the hydrogen bonds. Activation energy for this process is around 0.26 eV.