Approach Towards Heteroepitaxial Growth of Functional Molecular Crystals by Vapour Deposition

Abstract

In order to realize a thin film of organic single crystals, we have been investigating fabrication process using vapour deposition technique. Up to now, highly oriented thin films of 2-methyl-4-nitroaniline(MNA) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene(DAN), both of which are promising organic materials for nonlinear optical devices, could be fabricated on a buffed polyimide and on a thermally oxidized silicon wafer, respectively. In the case of MNA films, a series of results by X-ray diffraction and by SEM observation showed weak two-dimensional characteristics suggesting the existence of topographic effects and/or of interaction between MNA molecules and molecular moieties of polyimide substrate. Small optical transmittance of both MNA and DAN thin films are explained in terms of light scattering by grain boundaries and surface roughness.