EPI films also present an interesting example to study due to the fact that no crystal structure has been reported for this compound; attempts to grow single crystals suitable for structure solution have so far failed (though the crystal structures of two halogenated derivatives were solved).11 Such difficulties in the growth of high quality single crystals were also observed for the closely related quinacridone family of hydrogen-bonded pigments.12 The structural study of EPI thin films, therefore, presents an opportunity to attempt to solve the crystal structure directly from a thin film, for a material where, to date, no crystal structure has been forthcoming by any other means (such as single crystal X-ray diffraction or powder X-ray diffraction).