Identifying the Driving Forces for Alloying in UltraThin Films

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Identifying the Driving Forces for Alloying in
Ultra-Thin Films Karsten Pohl, Department of
Physics, University of New Hampshire, Durham, NH
LEEM-IV Our new technique of analyzing data
from low-energy electron microscopy (LEEM)
exceeds x-ray and electron diffraction in spatial
composition profiling. Designing and
controlling the formation of high-performance
surface alloys for unique catalytic and
electronic application is an important problem of
materials research. Understanding the detailed
driving forces of alloy formation in ultra-thin
film relies on the ability to measure the
heterogeneous compositional profiles in 3
dimensions within the surface region with a
resolution of a few nanometers. We have shown
that LEEM-IV has revealed this fundamental
insight for the first time by measuring the
concentration of palladium (Pd) atoms in the
first 3 layers of a copper (001) single crystal
in a region of 1 mm with a resolution of 8 nm
see graphic. We are now applying this new
technique to develop methods to grow graphene
layers epitaxially on silicon carbide wafers.
First results indicate that silicon depletion of
the surface region at high temperatures is a
viable process.