High-Resolution Rutherford Backscattering Analysis of Nanoscale Thin Films

Rutherford backscattering spectroscopy (RBS) has been an important analytical method for determination of the depth distribution of elemental concentrations in materials. The depth resolution of RBS is typically limited by the energy resolution of ion detectors. In this work we demonstrate the use of a compact magnetic spectrometer as the ion energy detector for high resolution RBS analysis. The magnetic spectrometer offers several advantages: (I) a high energy resolution Delta E/E similar to 1/2000; (2) a large bending power for MeV ions; and (3) a particular configuration allowing for true 180 degrees RBS analysis. By combining this magnetic spectrometer with the grazing angle geometry, we have achieved a depth resolution better than 5 angstrom for RBS analysis of concentration distributions in elemental (e.g., Ta) and compound (e.g. HfO2) thin films using 2 MeV helium ions. These experimental results suggest that high-resolution characterization of nanoscale thin films can be realized using MeV ions in conjunction with such magnetic spectrometers.