Measurement of molecular order and orientation in nanoscale organic films

Self-assembled monolayers (SAMs) have, in recent years, attracted much interest for surface modification, surface coatings and as interfacial coupling agents. X-ray photoelectron spectroscopy (XPS) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) have been used to non-destructively measure the molecular conformation of organic films with thickness of the order of 1nm. Three different types of molecular conformation were found for γ-aminopropyltriethoxysilane (γ-APS) films formed on ZnO surfaces. The orientation of γ-APS films was observed to vary with adsorption time and surface coverage. Thus the molecular conformation of thin films can be controlled through adjustment of the application parameters.