MOLECULAR-ORIENTATION BEHAVIOR OF PARAFFIN THIN-FILMS MADE BY VAPOR-DEPOSITION

The molecular orientation behavior of paraffin thin films prepared by the vapor deposition method was investigated. The molecular orientation in the thin film could be controlled by the substrate temperature, the deposition rate, the length of the molecular chain and other parameters. Of these parameters, the degree of supercooling, defined as the difference between the melting temperature of the sample and the substrate temperature, was found to be the most important factor influencing the molecular orientation in the film. It is supposed that the degree of supercooling affects the adsorption-desorption process and the molecular motions on the substrate, such as translation, rotation and precession modes. Among these modes, the precessional motion is assumed to play an important role in the formation of the thin film with the molecular orientation perpendicular to the substrate.