X-ray diffraction and Rutherford backscattering spectrometry of Ba1NbxTi1-xO3 thin films synthesized by laser ablation

Niobium doped barium titanate Ba1NbxTi1-xO3 thin films have been successfully synthesized by laser ablation on sapphire (00(0) over bar 1) and (100) SrTiO3 substrates, for the growth of hexagonal and cubic phases of this system. These films were synthesized with different concentrations of niobium under various conditions. X-ray diffraction measurements showed that the films were well aligned along the c-axis of the sapphire substrate for the hexagonal phase, while perpendicular to the SrTiO3 substrate surface for the cubic phase of this system. These films were deposited at substrate temperatures of 700 and 650 degrees C for the hexagonal and cubic phases, respectively, both in oxygen and nitrogen atmospheres. At room temperature these films have a very high resistance and large negative thermopower similar or equal to 300 mV/K. Rutherford backscattering spectrometry (RBS) was performed on very thin films of this system for different concentrations of niobium deposited in the N-2 atmosphere. We have found a deficiency of Ti in these films by RBS analysis, which along with other antisite defects and oxygen deficiency, may be a cause of high resistance and large thermopower in these films. (C) 1999 American Institute of Physics. [S0021-8979(99)07716-6].