Structural properties of hexaphenyl thin films obtained by a rubbing technique: characterization of a biaxial texture

X-ray diffraction analysis is used to characterize structural properties of hexaphenyl thin films prepared on glass substrates using physical vapor deposition. The thin films of thickness from 1000 to 3300 Angstrom are evaporated on a rubbed layer of hexaphenyl molecules serving as an orientation-inducing layer. The results reveal that the orientation of the evaporated molecules is effectively influenced by the rubbed layer. The long axes of the hexaphenyl molecules are oriented parallel to the rubbing direction and are aligned uniaxially. Moreover, the phenyl rings of the molecules are tilted relative to the substrate surface approximately 33 degrees. In other words, the hexaphenyl crystallites are oriented with (2 0 (3) over bar) planes parallel to the substrate surface and their [(2) over bar 0 1] crystallographic directions are oriented approximately parallel to the rubbing direction. However, the pole figure measurements document that the rubbing procedure does not determine the orientation of all hexaphenyl molecules in the thin film, a certain amount of crystallites possess a different orientation. (C) 1999 Elsevier Science B.V. All rights reserved.