REAL-SPACE COMPOSITION-DEPTH PROFILING IN POLYMERIC SAMPLES TO 3 NM RESOLUTION USING THE H-2(HE-3,H-1)HE-4 NUCLEAR-REACTION

Direct depth profiling techniques to date have largely lacked the nece ssary depth resolution to investigate interfacial phenomena of the ord er of the bulk correlation length (5-10 nm for a wide range of systems ). Here we investigate the optimal spatial resolution and depth of pro be that may be attained for composition - depth profiling of polymeric samples via nuclear reaction analysis (NRA) using the H-2(He-3,H-1)He -4 reaction. We find that the spatial resolution can be greatly improv ed by using a grazing incidence geometry of the incident He-3 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 a-particles were detected in the forw ard direction. At the same time the depth to which samples can be prof iled via the backwards emitted protons may be considerably extended re lative to the a-particle detection mode, when the He-3 beam impinges o n the sample surface at normal incidence (up to about 4 mu m into the sample for incident energies of 1.2 MeV in the proton-detection mode c ompared to only 1 mu m for the equivalent a-particle detection mode).