Formation of Epitaxial Twins by Perfluoro-N-Alkane Evaporated on Alkali Halide Crystal

Abstract
Structural evaluation of perfluoro- n-alkane, CF3(CF2)18CF3, thin films evaporated on KCl(001) single crystal was performed using a recently developed total reflection X-ray diffractometer. The molecular chain axes of the perfluoro- n-alkane crystals in the evaporated films were revealed to be normal to the substrate, where the molecules assembled in hexagonal symmetry and grew epitaxially on the KCl(001) surface with fourfold symmetry, arranging their h e x directions along the directions of the KCl crystal. Furthermore, detailed analysis suggested that the epitaxially grown crystals form a slightly distorted twin with facing their (14̄30) planes, referred to here as an “epitaxial twin”.