March 24, 2017

Extending the Capabilities of Scanning Probe Microscopy: The Path towards Robust, Quantitative, Multidimensional Atomic Resolution Imaging with Chemical Selectivity

Abstract: Despite the evolution of scanning probe microscopy (SPM) into a powerful set of techniques that image surfaces and map their properties down to the atomic level, significant limitations in both imaging and mapping persist. Currently, typical SPM capabilities qualitatively record only one property at a time and at a fixed distance from the surface. Furthermore, the probing tip’s apex is chemically and electronically undefined, complicating data interpretation. To overcome these limitations, we have started to integrate significant extensions to existing SPM approaches. First, we expanded noncontact atomic force microscopy with atomic resolution to three dimensions by adding the capability to quantify the tip-sample force fields near a surface with picometer and piconewton resolution [1,2]. Next, we gained electronic information by recording the tunneling current simultaneously with the force interaction [3] and introduced a new operating scheme called tuned-oscillator atomic force microscopy that substantially improved imaging robustness and therefore sample throughput and user friendliness [4]. Finally, we will illustrate how the tip chemistry, tip asymmetry, and tip-sample distance influence the recorded interactions – and thus the information one can gain from images –, ultimately allowing to selectively image specific atomic species [3, 5]. During the talk, applications to various model systems including oxides, metals, ionic crystals, and layered materials will be presented.

Bio: Udo D. Schwarz graduated in 1989 from the University of Basel, Switzerland, receiving his Ph.D. in physics from the same institution in 1993. Subsequently, he continued his work as a staff scientist and lecturer at the Institute of Applied Physics of the University of Hamburg, Germany. In 2001, Prof. Schwarz moved to the Materials Science Department of the Lawrence Berkeley National Laboratory in Berkeley, California. Since 2002, he works at Yale’s Mechanical Engineering Department, where he got promoted to full professor in 2009 and serves as department chair since 2012. His research interests concern the local measurement of atomic-scale interactions and properties, including electric, magnetic, chemical, and nanotribological interactions, using scanning probe microscopy techniques to study problems in surface physics, catalysis, friction, and adhesion.

[1] B. J. Albers et al., Nature Nanotechnology 4, 307 (2009).
[2] M. Z. Baykara et al., Advanced Materials 22, 2838 (2010).
[3] M. Z. Baykara et al., Physical Review B 87, 155414 (2013).
[4] O. E. Dagdeviren et al, Nanotechnology 27, 065703 (2016).
[5] H. Mönig et al., ACS Nano 7, 10233 (2013).