A single-reflection attenuated total reflection (ATR) technique has been used to study low index monolayers with a high index ATR hemisphere in an optical contact with the sample surface. A model calculation predicts a field enhancement with the present method substantially larger than that of conventional ATR. For the present method, a discontinuity of the field normal to the film is responsible for the field enhancement in the lower index thin film. We show theoretically and experimentally that the angle of incidence has a strong influence on the ATR signal strength. We demonstrate the present method by examining the infrared reflectance spectra of a undecylenic acid self-assembled on Si (111) and with the adsorption of a bovine serum albumin monolayer. We also apply the method to examine the oxidation and surface contamination of the functionalized Si samples stored in ambient conditions. (c) 2006 American Vacuum Society.