Someone argues: "The feedback loop of a scanning tunnelling microscope adjusts the…
PHYSICS · Subjective · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction · Crystal structure, bonding and diffraction
Solid State Physics, Ch Seeing atoms: electron and scanning-probe microscopy
Problem
Someone argues: "The feedback loop of a scanning tunnelling microscope adjusts the vertical piezo position z(x,y) so as to hold the tunnel current fixed at every point. The recorded image is exactly this function z(x,y). Therefore an STM image is a direct topographic height map of the surface, atom by atom, in the same sense that a mechanical profilometer traces a surface with a stylus." Find the error in this argument and state, in one or two sentences, what a constant-current STM image is actually a map of.