Microcrystal ordering and second-order optical susceptibilities of zinc oxide films

Second harmonic generation in zinc oxide films deposited by the hydrothermal method was investigated. A correlation between second-order optical susceptibility tensor components d311 and d333 was studied by using the model of noninteracting microcrystals, and the origin of different contributions to the film nonlinearities was discussed. The change of stacking sequences and the inhomogeneity in the distribution of the nonlinearities over the film thickness are the most probable effects hindering the investigations of the thickness dependence of ZnO film nonlinearities. A model of the inhomogeneous distribution of the nonlinearities over the film thickness was used for doing an analysis of the experimental data features, which were accounted for by a sublayer, adjacent to the seed layer, and possess high optical nonlinearity, d333 = −72.6 pm/V.