Structure and second-order nonlinear optical properties of CuCl nanocrystal-doped thin films prepared by rf sputtering

摘要

Second-order nonlinearity of CuCl nanocrystal-doped silica and indium tin oxide (ITO) films were examined by utilizing Maker fringe method. The films were prepared by means of the rf sputtering method with silica or ITO target on which CuCl pellets were placed. X-ray diffraction patterns of the films indicate that the mean crystallite size of CuCl nanocrystals was 20-30 nm based on the Sherrer's equation. The films exhibit second-harmonic generation. As for the films prepared at a substrate temperature of room temperature, the dependence of second-harmonic (SH) intensity on incident angle shows that the films have an optical uniaxial anisotropy with an axis perpendicular to the film surface. An orientation of CuCl nanocrystals was confirmed by X-ray diffraction patterns, but the direction of orientation depends on the sputtering condition. In contrast, the films prepared at a substrate temperature higher than 200℃ shows different incident angle dependence of second-harmonic intensity; a maximum of second-harmonic intensity appears at the incident angle of 0°. The spacings of (111), (220), and (311) planes estimated from X-ray diffraction patterns are smaller than the values of the bulk cubic structure.