Phase-sensitive surface X-ray scattering study of a crystalline organic-organic heterostructure

An X-ray study of a crystalline organic-organic heterostructure, consisting of a film of PTCDA (3,4,9,10-perylenete-tracarboxylic dianhydride) grown o n a self-assembled monolayer (SAM) of decanethiol on Au(1 1 1), is presente d. The sandwich structure acts as a "molecular interferometer", where the i nterference between the Laue function of the PTCDA film and the crystal tru ncation rod (CTR) of the substrate is governed by the SAM spacer thickness, d(0). A pronounced destructive interference feature is observed, which all ows the determination of do with great sensitivity. (C) 2000 Elsevier Scien ce B.V. All rights reserved.