Crystalline Channeling of MeV Ion Beams
Dr. Stephen Remillard and Dr. Paul DeYoung
Thin film strontium titanate (SrTiO3) on single crystal MgO substrate, and thin film strontium manganese oxide (SrMnO3) also on single crystal MgO substrate, are being considered for use in engineered superlattices. Crystal matching of the films to the substrates is indicated by channeling of an ion beam through the lattice. With its ability to resolve depth in a sample, Rutherford backscattering of helium ions is used to determine layer thickness and the depth profile of the elemental composition of a sample. Ion beam channeling occurs when the beam’s incident angle is parallel to crystal planes, or rather normal to the surface. Channeling can occur in well-ordered and pure crystals, providing an indication of sample quality. Comparison of the backscattering yields at different incident angles will show a drop in yield as the optimum channeling angle is approached. Channeling is seen with the bulk SrTiO3 sample as well as with the thin film samples. Even though an 8% lattice mismatch exists between SrMnO3 and MgO, channeling was still evident, although in this case the yield suppression revealed structure around normal incidence.
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