Analysis of STM images with pure and CO-functionalized tips: A first-principles and experimental study

• Published in: Physical review. B 2017-08, Vol.96 (8), Article 085415
• Main Authors: Gustafsson, Alexander, Okabayashi, Norio, Peronio, Angelo, Giessibl, Franz J., Paulsson, Magnus
• Format: Article
• Language: English
• Subjects: Adatoms; Atomic force microscopy; Atomic structure; Computation; Copper; Density functional theory; First principles; Fysik; Mathematical analysis; Microscopy; Physics; Scanning tunneling microscopy; State of the art; Tips; Wave functions; Wave propagation
• ISSN: 2469-9950; 2469-9969; 2469-9969
• DOI: 10.1103/PhysRevB.96.085415

We describe a first-principles method to calculate scanning tunneling microscopy (STM) images, and compare the results to well-characterized experiments combining STM with atomic force microscopy (AFM). The theory is based on density functional theory with a localized basis set, where the wave functions in the vacuum gap are computed by propagating the localized-basis wave functions into the gap using a real-space grid. Constant-height STM images are computed using Bardeen's approximation method, including averaging over the reciprocal space. We consider copper adatoms and single CO molecules adsorbed on Cu(111), scanned with a single-atom copper tip with and without CO functionalization. The calculated images agree with state-of-the-art experiments, where the atomic structure of the tip apex is determined by AFM. The comparison further allows for detailed interpretation of the STM images.