Second Harmonic Generation in Electrochemically Synthesized Films of Ternary Metal Prussian Blue Analogs

We have observed the generation of second harmonic (SH) light from electrochemically synthesized films. The X-ray diffraction spectra of these films showed that the (1 1 0) and (1 1 1) crystalline planes were oriented parallel to the film plane, and that the crystal structures were not the typical face-centered cubic of Prussian blue analogs but they possessed a noncentrosymmetric monoclinic C2 symmetry. The SH intensity vs. plots showed that only the ternary metal films emitted SH radiation with an intensity that grew with increasing Maker's fringe pattern showed that the electric polarization was oriented perpendicular to the film plane. Furthermore, the excitation wavelength dependence on the SH intensity showed that this SH wave was resonant with the intervalence transfer band between and These SH properties are explained through the analysis of preferred orientation and noncentrosymmetric structure of electrochemical-deposited crystalline films, and by the electric polarization due to the site.