High resolution UHV Helium Ion Microscopy of work function, step edges and crystal structure

Helium Ion Microscopy—in particular under UHV conditions—is well know for it’s high resolution imaging capabilities and the exceptional surface sensitivity. Here, we utilize both of these outstanding characteristics of this technology to visualize step edges, minute changes in composition and structural properties of a Ag/Pt alloy layer grown on Pt(111). A work function contrast of only a few ten’s of meV allows to distinguish between areas of different Ag content in the alloy layer. As a result step edges on the Pt(111) crystal overgrown by the alloy layer become visible. Furthermore, the regular arrangement of FCC and HCP areas in the alloy layer could be revealed using fast Fourier image analysis and dechanneling image contrast. The measured spacing of 6nm agrees well with the expected value. Low energy electron microscopy has been used to cross check the results and further analyse the alloy layer.
This research is supported by the Dutch Technology Foundation STW, which is the applied science division of NWO, and the Technology Programme of the Ministry of Economic Affairs.