Simulating noncontact atomic force microscopy images

Journal Article · 27 November 2019 · Physical Review Materials

DOI: https://doi.org/10.1103/physrevmaterials.3.110302 · OSTI ID:1800352

Chelikowsky, James R.  ^[1]; Fan, Dingxin ^[2]; Lee, Alex J. ^[2]; Sakai, Yuki ^[2]

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1. Univ. of Texas, Austin, TX (United States); OSTI
2. Univ. of Texas, Austin, TX (United States)

A scanning probe with an atomically sharp tip is used in atomic force microscopy. As the probe is rastered over the specimen of interest, changes in its vibration mode can be ascribed to changes in the interatomic forces between the specimen and the tip. Various modes for implementing atomic force measures exist. One of the most successful modes is frequency-modulation noncontact atomic force microscopy. Here we address the role of replicating accurate forces on the probe tip to simulate images within this mode. In this work, we examine several approaches. One involves the use of classical force fields based on interatomic potentials, where the potentials are often fit to experiment. Other approaches center on the use of forces generated from quantum-based calculations. We consider the development of a “virtual tip” approximation wherein the probe tip senses electrostatic forces generated by the specimen. This approach treats the specimen quantum mechanically, while the tip is treated as a classical object. We also consider the use of an embedding approximation to avoid direct computations of the specimen in the presence of the tip. In this method, the tip and specimen are treated quantum mechanically. However, the electronic structure of the specimen is computed in the absence of the probe tip. The electronic density of the specimen is then fixed and the electronic structure of the tip is then computed in the presence of the fixed density. As a general approach, we outline new methods for the full computation of quantum forces between the tip and specimen. We note that quantum-based forces are particularly important as they directly contain the chemical nature of the forces present without the use of any adjustable parameters. We illustrate recent algorithmic developments to computing quantum forces that can produce accurate simulations of atomic force microscopy images for large and complex molecular species. We also suggest new pathways to overcome current challenges in this rapidly evolving field.

• Research Organization: Univ. of Texas, Austin, TX (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Welch Foundation
• Grant/Contract Number: FG02-06ER46286
• OSTI ID: 1800352
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 11 Vol. 3; ISSN 2475-9953
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English