MORPHOLOGY AND NLO PROPERTIES OF THIN-FILMS OF ORGANIC-COMPOUNDS OBTAINED BY EPITAXIAL-GROWTH

The epitaxial crystallization of 2-methyl-4-nitroaniline, an organic m olecule having strong non linear optical properties, was demonstrated. The PTFE substrates were prepared according to the friction transfer method. The MNA crystals can be grown either from the vapor phase or s olutions in various experimental conditions. The crystallographic cont act plane between MNA crystals and the PTFE substrate was investigated by grazing incidence X-ray diffraction. In fact, the MNA contact the PTFE substrate with their (10-2) crystal planes, their polar axes bein g parallel to the PTFE sliding direction, i.e. the polymer chain axis. The mismatch between substrate and overlayer lattices is equal to 3%. Second harmonic generation measurements were also performed on differ ent MNA layers crystallized on PTFE. The analysis of the polarization dependance of the second harmonic has confirmed the proposed molecular orientation. (C) 1998 Elsevier Science B.V.