Monolayer Level Depth Profiling by Laser Induced Fluorescence Spectroscopy

Abstract

Abstract Application limits of the proposed concentration depth profile using laser induced fluorescence spectroscopy based on the reciprocal principle (Bull. Chem. Soc. Jpn., 64, 755 (1991)) were investigated. Although this method has no limitations regarding film thickness and spatial resolution in the depth direction theoretically, for practical applications, they are limited by the instrumental factors. Effects of uncertainty in the observation angle measurement, which depends on the size of the detector, the mechanical precision of the rotating stage, and experimental errors in the fluorescence intensity measurement on the accuracy of the reconstructed concentration depth profile were discussed in detail. The theoretical results predicted nanometer level depth profiling with our laboratory-constructed instruments. A 29 nm thick model film sample, consisting of long chain molecular bilayers, was used to verify the theoretical analysis results. The concentration depth profile for bilayer level steps of about 5 nm was obtained under our experimental conditions. Possible improvements in this method and monolayer level depth profiling were also considered.