Editing Atomic force microscopy (section)

==Identification of individual surface atoms==
The AFM can be used to image atoms and structures on a variety of surfaces.  The atom at the apex of the tip "senses" individual atoms on the underlying surface when it begins the formation of chemical bonds with each atom.  Because these chemical interactions subtly alter the tip's vibration frequency, they can be detected and mapped. This principle was used to distinguish between atoms of silicon, tin and lead on an alloy surface, by comparing these atomic fingerprints with values obtained from [[density functional theory]] (DFT) simulations.<ref name="Sugimoto_2007">{{cite journal|doi=10.1038/nature05530|date=Mar 2007|author1=Sugimoto, Y |author2=Pou, P |author3=Abe, M |author4=Jelinek, P |author5=Pérez, R |author6=Morita, S |author7=Custance, O |title=Chemical identification of individual surface atoms by atomic force microscopy|volume=446|issue=7131|pages=64–7|issn=0028-0836|pmid=17330040|journal=[[Nature (journal)|Nature]]|bibcode = 2007Natur.446...64S |citeseerx=10.1.1.552.6764|s2cid=1331390}}</ref>

Interaction forces must be measured precisely for each type of atom expected in the sample, and then to compare with forces given by DFT simulations. It was found that the tip interacted most strongly with silicon atoms, and interacted 24% and 41% less strongly with tin and lead atoms, respectively.  Each different type of atom could be identified in the matrix as the tip using this information.<ref name="Sugimoto_2007"/>