Ordered films of a new substituted diphenyl-1,3,4-oxadiazole for application in light emitting devices

The formation of highly ordered layers of oxadiazoles by vapor deposition (VD) aims to built structures characterized by the emission of polarized light. In this paper the formation of multilayer structures depending on preparation parameters is described. Essential deposition parameters are the substrate temperature and the deposition rate. Systematic variation of these parameters and structure investigation of the resulting samples by means of X-ray specular reflection (XSR) and scanning force microscopy (SFM) were used to get insight into the film growth mechanism. A comparison of the length of the molecules extended chain conformation with the layer periodicity derived from X-ray data (d=4.9 nm) reveals a bilayer structure. SFM images of samples formed at optimum deposition parameters show a smooth topography with bilayer steps. This indicates a bilayer-by-bilayer growth mechanism. The vapor deposited oxadiazole films show fluorescence with a maximum intensity at a wavelength of 382 nm.