X-RAY ANALYTICAL METHODS FOR ULTRATHIN ORGANIC FILMS

摘要

Three x-ray analytical methods were tested for their feasibility to determine the crystal structure of highly ordered Me-phthalocyanine (MePc) molecular films up to 30 nm. The molecular alignment of 3 nm ZnPc on ITO substrates depends on temperature and chemical passivation of the substrate. From near-edge x-ray absorption fine structure spectroscopy the best molecular alignment was found for films on H{sub}3PO{sub}4 passivated ITO surface deposited at 90° substrate temperature. The thickness average of lattice distance of a-modification ZnPc a-axis perpendicular to the substrate surface is determined by XRD measurement to 1.28 nm. For β-modification c-axis a lattice distance of 1.25 is found. The full crystal profile of 37.7 nm CuPc films on oxidized Si were analyzed by x-ray reflectivity calculations fitted to experimental data. Best fit turned out to be a three layer system for Cu-Pc consisting of 3 nm disturbed molecular base on the substrate, 32.5 nm highly ordered bulk layer and 2.2 nm surface layer standing for the film roughness.