Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Direct depth profiling techniques to date have largely lacked the necessary depth resolution to investigate interfacial phenomena of the order of the bulk correlation length (5 - 10 nm for a wide range of systems). Here we investigate the optimal spatial resolution and depth of probe that may be attained for composition - depth profiling of polymeric samples via nuclear reaction analysis (NRA) using the 2H(3He, 1H)4He reaction. We find that the spatial resolution can be greatly improved by using a grazing incidence geometry of the incident 3He beam on the sample, and analyzing the emitted protons in a backwards direction. This results in spatial resolutions down to about 3 nm at the sample surface, compared to a value of some 7 nm or more previously reported in earlier studies when emitted α-particles were detected in the forward direction. At the same time the depth to which samples can be profiled via the backwards emitted protons may be considerably extended relative to the α-particle detection mode, when the 3He beam impinges on the sample surface at normal incidence (up to about 4 μm into the sample for incident energies of 1.2 MeV in the proton-detection mode compared to only 1 μm for the equivalent α-particle detection mode).
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