In situ X-ray characterization of oligophenylene thin films prepared by organic molecular beam deposition

Abstract

In order to examine organic thin films during the deposition, we newly developed in situ observation system of an energy dispersive total reflection X-ray diffraction (TRXD) equipped with an organic molecular beam deposition (OMBD). p-Sexiphenyl (6P), which is one of oligophenylenes, is noted as a useful material with unique optical properties by controlling the molecular orientation. To establish the method to control the molecular orientation in 6P thin films prepared by OMBD, 6P thin films on different substrates of silicon oxide (SiO 2) and uniaxially oriented poly( p-phenylene) (PPP) were examined by using in situ TRXD. In the case of the 6P thin films prepared on SiO 2, 6P molecules formed with the normal orientation from the initial process of the deposition. On the other hand, it was observed 6P molecules on the oriented PPP substrates formed with the parallel orientation along the PPP chains. By using out of plane measurements, it was revealed that the (203̄) planes of 6P crystallites preferentially oriented parallel to the substrate surface.