Symmetry Analysis of ZnSe(100) Surface in Air By Second Harmonic   Generation
  Polarized and azimuthal dependencies of optical second harmonics generation (SHG) at the surface of noncentrosymmetric semiconductor crystals have been measured on polished surfaces of ZnSe(100), using a fundamental wavelength of 1.06$\mu m$. The SHG intensity patterns were analyzed for all four combination of p- and s-polarized incidence and output, considering both the bulk and surface optical nonlinearities in the electric dipole approximation. We found that the measurement using $S_{in}-S_{out}$ is particularly useful in determining the symmetry of the oxdized layer interface, which would lower the effective symmetry of the surface from $C_{4v}$ to $C_{2v}.$ We also have shown that the [011] and [0$\bar{1}$1] directions can be distinguished through the analysis of p-incident and p-output confugration. 
Xiangyang Song, Arnold Neumann, Rein Maripuu, and Kai Siegbahn   (ESCA-Laser Laboratory, Insitute for Material, Uppsala Univ...