Paper IS+AS-FrM9
In-situ TEM Investigation of Nanoscale Deformation Mechanisms in Lubricious Thin Films

Friday, November 13, 2009, 11:00 am, Room C4

The field of tribology - the study of contacting surfaces in relative motion - has long suffered from the problem of buried interfaces, forcing researchers to conduct experiments completely blind to the underlying mechanical deformation and structural processes that dictate friction behavior. Using a unique in-situ TEM nanomanipulation technique, we can dynamically observe the sliding interface at the single asperity level. With this method, we can deeply probe the effects of film composition on surface behavior and by extension, on the tribology and wear properties of such films.

In particular, we are interested in the nanoscale deformation mechanisms in lubricious thin films, particularly highly-ordered pyrolytic graphite, diamond-like carbon (DLC), and molybdenum disulfide (MoS2). The manner in which the material responds to an applied stress is not only of fundamental interest, but of practical importance as device design shrinks to ever-smaller dimensions.

Using our in-situ approach, we have access to all the instrumentation of the TEM. With HOPG and MoS2, we can use electron diffraction to look at the structural deformations in the graphitic grains as a function of the type and magnitude of applied stress. We have also looked at the phase transformation usually known as graphitization seen in DLC films. The bonding configuration at the surface has been shown to play a significant role in nanotribological properties, along with experimental and growth parameters such as the relative amount of hydrogen present at the surface. By using electron energy loss spectroscopy combined with high resolution imaging, we can look at the effect of film hydrogenation on the speed of the phase transformation, which is useful for both applications and for determining the actual mechanism involved.