THE INVESTIGATIONS OF DIFFERENT NPP CRYSTAL-SURFACE STRUCTURES BY AFM

The investigations of nonlinear optical crystal surface structures hav e been reported in this paper for the first time. The AFM observations for cleavage (101) surface and (001) surface of NPP crystal indicate that the molecular arrangements on both of them are the same with its bulk structure, without any superstructure. And the phenyl and pyrroli dine rings in (001) surface can be distinguished. The angle between th e molecular charge transfer axis and the binary axis obtained by AFM i s 56 degrees, closed to the optimal angle, which leads to the large no nlinear optical efficiency of NPP crystal.