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The ASP logo depicts the snake known in antiquity as the asp* "analysing" a surface with its forked tongue.  Snakes have a remarkable sense of smell and the molecular collection "patches" on each tine of the fork allow the snake to smell stereoscopically - natural spatially resolved chemical information. 

The data in the background is the first sub-nm ultra low energy SIMS depth profile obtained with the prototype floating low energy ion gun (FLIG) by Mark Dowsett and Noel Smith in 1994.  The sample was alternating layers of silicon and germanium just 1 nm thick, and was grown by Prof. Evan Parker's Nano-Silicon group.

FirstSiGeHere is a more detailed view of the depth profile (blue curve).  The primary ions were 300 eV O2+ at normal incidence.  At first sight, it appears that the depth resolution in the profile is increasing with depth - quite the opposite to what one would expect.  In fact, TEM of the same sample shows that the layers nearer the surface were buckled by strain in the material so that they appear to be corrugated.  It is this effect which causes  the near-surface loss of depth resolution.  

At the time this profile was originally recorded, 2 keV was regarded as a low beam energy.  The red curve shows that no detail can be recovered from the sample at this energy. 


*from the Greek aspis, and probably the modern Egyptian Cobra




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