Selecting the tip electron orbital for scanning tunneling microscopy imaging with sub-?ngstrom lateral resolution

Abstract

We report on scanning tunneling microscopy (STM) studies performed with single crystalline W[001] tips on a graphite(0001) surface. Results of distance-dependent STM experiments with sub-?ngstrom lateral resolution and density functional theory electronic structure calculations show how to controllably select one of the tip electron orbitals for high-resolution STM imaging. This is confirmed by experimental images reproducing the shape of the 5dxz,yz and 5dx2 ? y2 tungsten atomic orbitals. The presented data demonstrate that the application of oriented single crystalline probes can provide further control of spatial resolution and expand the capabilities of STM.