PREPARATION AND OPTICAL-PROPERTIES OF GOLD-DISPERSED BATIO3 THIN-FILMS

Gold-dispersed BaTiO3 thin films and gold-dispersed SiO2 thin films were prepared by r.f. magnetron sputtering method. The as-deposited films were heat-treated in air at temperature ranging from 700 to 900-degrees-C for 1h, and were compared to the optical properties of these films. For the SiO2 matrix, an absorption peak position shifted toward longer wavelength from 520 to 535 nm as the volume fraction of gold increases, and gold fine particles were spherical and were uniformly dispersed in the films. In contrast, for the BaTiO3 matrix, an absorption peak position shifted from 580 to 640 run. The matrix had substantially crystallized, and the size of matrix grain and the gold particle size varied widely. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd : YAG laser with 7 ns pulse duration. Third-order nonlinear susceptibility chi(3) of gold-dispersed BaTiO3 films increased with increasing the heat-treating temperature, volume fraction of gold in these films and the mean particle size of gold. The values of chi(3)/alpha532 Of BaTiO3 films were much larger than those Of SiO2 films. It seemed that BaTiO3 matrix contributes to increase the value of chi(3)/alpha532. The resulting maximum value of gold-dispersed BaTiO3 films was 3 x 10(-6) esu. The large chi(3) may be ascribed to the high dielectric constant of the films.