Probing the shape of atoms in real space

TL;DR

This paper uses advanced scanning tunneling microscopy techniques to visualize individual atoms and their electronic orbitals in real space, achieving high resolution by oscillating the tip to avoid instabilities.

Contribution

It introduces a method of oscillating the STM tip to obtain high-resolution atomic images without instability issues, enabling direct visualization of atomic orbitals.

Findings

Images resemble charge densities of atomic orbitals

High-resolution imaging of single atoms achieved

Method reduces tip-sample instability

Abstract

The structure of single atoms in real space is investigated by scanning tunneling microscopy. Very high resolution is possible by a dramatic reduction of the tip-sample distance. The instabilities which are normally encountered when using small tip-sample distances are avoided by oscillating the tip of the scanning tunneling microscope vertically with respect to the sample. The surface atoms of Si(111)-(7 x 7) with their well-known electronic configuration are used to image individual samarium, cobalt, iron and silicon atoms. The resulting images resemble the charge density corresponding to 4f, 3d and 3p atomic orbitals.