Our research focuses on the study friction, plasticity and wear at the nanoscale using atomic force microscopy (AFM).  We investigate these problems on simple materials and determine the fundamental physical mechanisms by which they occur.  By approaching these complex engineering problems at the atomic-length scale, we can reduce the complexity of the problems significantly.  With these experiments, we hope to be able to predictively determine material parameters such as friction coefficients, plasticity/hardness, and wear rates, which will be critical in the development of the next generation materials and lubricants.

The image on the right shows atomic stick-slip friction on an alkanethiol self-assembled monolayer grown on a Au(111) substrate.  Atomic lattice resolution is achieved, however, single atomic defects cannot be observed due to the "large" multi-atom contact between the AFM tip and the surface.  Using AFM, we are able to resolve foces much less than 1 nN, as shown in the line profile below, which approaches the strength of single atomic bonds.

We are also able to take advantage of other modes of AFM to obtain true atomic resolution of surfaces.  On the left is an example of true atomic resolution of the (100) surface of potassium bromide (KBr).  We can identify the high resolution capability of the AFM by observing single atomic vacancies at the surface.