Atomic Fingerprinting of Heteroatoms Using Noncontact Atomic Force Microscopy

Abstract Immense strides have been made in increasing the resolution of scanning probe microscopy. Noncontact atomic force microscopy (nc‐AFM) now offers one the ability to characterize and visualize single molecules with subatomic resolution. Specifically, nc‐AFM with a carbon monoxide (CO) functionalized tip has the ability to discriminate functional groups (–CC–, –CH₂, –CO, …), although discriminating atomic species often remains as an ongoing challenge. Here, real‐space pseudopotentials constructed within density functional theory are employed to accurately simulate nc‐AFM images of molecules containing heteroatoms (S, I, and N) within dibenzothiophene (DBT), 2‐iodotriphenylene (ITP), acridine (ACR) and ferrous phthalocyanine (FePc). It is found that S and I atoms can be easily identified from C based on their unique features. For N atoms, a use of tip functionalization is proposed to effectively discriminate them from C atoms.