X-ray Photoelectron Spectroscopic Studies of the Bonding of Organic Monolayers on Various Oxidized Surfaces

Abstract

With successive applications of one, three, and five monolayers of cadmium arachidate (cadmium eicosanoate) by the Langmuir-Blodgett technique to oxidized samples of indium, rhodium, silicon and tin, we observed progressive changes in the x-ray photoelectron spectral signals from the various elements both in the samples themselves and in the arachidate overlayers. With our APL computer program, all peaks were analyzed and fit to Gaussian curves with varying amplitudes and widths. Binding energies were thereby determined with high precision (±0.05 eV), allowing us to infer some details about the interfacial region and molecular bonding. Differences in chemical shifts have been interpreted as arising from a partial transfer of charge, such as an acid-base interaction and the corresponding electrostatic force across the interface. Evidence is given to show that this force is localized within 2.5 nm of the interface. © 1978, Taylor & Francis Group, LLC. All rights reserved.