UDO D. SCHWARZ
Associate Professor of Mechanical Engineering
Ph.D. University of Basel, Switzerland
E-mail: udo.schwarz@yale.edu
Phone: 1 (203)432-7525
Fax: 1 (203)432-6775
Mailing address: Yale University
P.O. Box 208284, New Haven, CT 06520-8284

• Fundamental study of force interactions at and between surfaces from the nanometer down to the atomic scale ("Nanomechanics")
• High-resolution investigations of surfaces and surface properties
• Nanotribology, atomic mechanisms of friction
• Elastic properties of matter on the atomic scale

I am using scanning probe methods (in particular scanning force microscopy). To achieve highest quality of results, these techniques are continuously further developed in my lab, with a focus on ultrahigh vacuum low-temperature scanning force microscopy, friction force microscopy, and the local mapping of surface elasticity.


Examples:

1. Resolution capabilities of scanning force microscopy:

        

Scanning force microscopy works by profiling a suitable sample surface with a sharp tip that is, in optimum case, terminated by a single atom. Due to this very general operating principle, virtually any kind of sample can be investigated on scales from the micrometer range down to atomic resolution. Two examples are given here to highlight the universality of the operating principle. First, an individual human skin cell is imaged on a scale of 55 µm x 55 µm; the average height of the cell was about 300 nm (left image). On the other end of the spectrum, atomic resolution of a xenon(111) surface, obtained in ultrahigh vacuum and at low temperatures (T~22 K), is presented in the right image as a three-dimensional perspective representation. Up to now, no method other than scanning force microscopy has been successful to achieve atomic resolution on a noble gas crystal like xenon.


2. Nanotribology, atomic origins of friction:

         

By means of friction force microscopy, we can locally resolve the lateral forces acting on atoms at interfaces down to an atomic scale. The left image shows a map of the lateral forces acting in sliding direction for a silicon nitride tip moving from left to right on a graphite sample (image size: 15 Å x 15 Å; dark colors mean low and bright colors high lateral forces). From such data sets, the exact motion of the tip atoms in the surface potential of the graphite can be calculated (right image). Three exemplary paths of atoms are plotted “time-resolved,” i.e., their position is indicated by points separated by equal time intervals of 0.15 ms.

More information

Selected Publications

 

"Dynamic Force Microscopy with Atomic Resolution at Low Temperatures," A. Schwarz, U. D. Schwarz, S. Langkat, H. Hölscher, W. Allers, and R. Wiesendanger, Appl. Surf. Sci., 188, 245-251 (2002).

"Atomic Resolution in Scanning Force Microscopy: Concepts, Requirements, Contrast Mechanisms, and Image Interpretation," U. D. Schwarz, H. Hölscher, and R. Wiesendanger, Physical Review B, 62, 13089 (2000).

Dynamic Mode Scanning Force mMcroscopy Performed at Low Temperatures on n-InAs(110)-(1x1)," A. Schwarz, W. Allers, U. D. Schwarz, and R. Wiesendanger, Physical Review B, 61, 2837-2845 (2000).

 "Consequences of the "Stick-Slip" Movement for the Scanning Force Microscopy Imaging of Graphite," H. Hölscher, U. D. Schwarz, O. Zwörner, and R. Wiesendanger, Physical Review B, 57, 2477-2481 (1998).