DIELECTRIC AND AC CONDUCTION PROPERTIES OF THERMALLY EVAPORATED LITHIUM-NIOBATE THIN-FILMS

Thin films of LiNbO3 are prepared by thermal evaporation onto well cleaned glass substrates at 2.66 x 10(-3) Pa. The thicknesses of the dielectric films are measured by Tolansky technique (Fizeau fringes). The X-ray diffractogram shows that the as deposited films are amorphous in nature. Aging and annealing effects are found to improve the dielectric properties. The capacitance and dielectric loss are measured from 303 to 463 K in the frequency range 1 to 30 kHz. The dielectric constant of a film of 80 nm thickness is found to be 8.01 at room temperature in the frequency range studied. From the ac conduction studies it is confirmed that the mechanism responsible for the conduction process in these films is electronic hopping. The intrinsic temperature coefficient of capacitance is estimated to 1500 ppm/K. Two activation energies are observed for the thermally activated process and the results are discussed.