PREDICTION OF THE EPITAXIAL ORIENTATION OF ULTRATHIN ORGANIC FILMS ON GRAPHITE

A method of predicting the epitaxial orientation of organic monolayer on graphite substrate was proposed together with a misfit defined appropriately for the prediction. This method is based on a lattice matching mode, point-on-line coincidence, that has been found through our scanning tunneling microscopy (STM) investigations of organic epitaxy on graphite. In order to examine efficiency of the method, epitaxial orientations of bis-1,2,5-thiadiazolo-tetracyano-quinodimethane (BSDA-TCNQ) and bis-1,2,5-selenadiazolo-tetracyano-quinodimethane (BSDA-TCNQ) were predicted and the predictions were compared with the orientations observed by STM. In both cases, the orientation observed was found to be exactly one of the predicted orientations, which suggests not only the efficiency of the prediction method but also the importance of the point-on-line coincidence in organic epitaxy.