GROWTH OF A WELL ORIENTED LAYER OF P-NITROANILINE ON THE (100)-PLANE OF A P-CYANOANILINE SINGLE-CRYSTAL, STUDIED BY POLARIZED ABSORPTION AND 2ND-HARMONIC GENERATION

It has been observed that a well oriented film, of thickness 20 to 1000 nm, grows when p-nitroaniline is deposited, by vacuum sublimation, onto a (100) cleaved face of a single crystal of p-cyanoaniline. The orientation of the deposited molecules was studied with polarized absorption and optical second-harmonic generation. It is concluded that p-nitroaniline molecules are stacked with their molecular plane parallel to the surface. The high orientational order in the deposited layer is quite insensitive to the substrate temperature during the deposition between 200 and 300 K.