AFM vs STM: Key Differences, Strengths, and When to Use Each
AFM (Atomic Force Microscope) drags an ultra-sharp tip over a sample, mapping its surface by measuring tiny forces. STM (Scanning Tunneling Microscope) hovers a tip just above, recording electrons that quantum-tunnel across the gap.
Engineers often grab whichever tool is free, then wonder why soft cells rip or metal atoms blur. The mix-up comes from both having “scanning” in their names and producing nanometre maps—yet their physics, prep, and best samples differ sharply.
Key Differences
AFM can scan insulators and liquids, sensing van-der-Waals forces; STM needs conductive samples and ultra-high vacuum. Resolution: STM can image single atoms; AFM excels at 3-D topography of polymers or biomolecules without coating.
Which One Should You Choose?
Use STM for atomic lattice studies on metals or semiconductors. Pick AFM for soft, insulating, or hydrated specimens—cells, polymers, MEMS—where force control and no current are crucial.
Examples and Daily Life
Drug labs map pill coatings with AFM; chip fabs tweak silicon surfaces with STM. Art conservators use AFM to check varnish layers; physicists use STM to watch graphene defects in real time.
Can AFM see atoms like STM?
Only under special conditions—ultra-sharp tips, ultra-low noise, and high vacuum. Routine AFM shows sub-nanometre bumps, not individual atoms.
Is STM faster than AFM?
Not necessarily. STM scans can be quicker on flat conductors, but AFM’s force feedback is faster on rough or delicate samples where tunnelling current would damage them.