High resolution surface roughness measurements in air using a scanning tunneling microscope

Surface roughness is an important parameter for characterizing surfaces in tribology. The existing surface roughness measurement techniques, however, are often limited in either vertical or horizontal resolution, are usually slow, and may in some case induce undesirable specimen changes in the course of measurements. On the other hand, scanning tunneling microscopy is capable of superb spatial resolution and rapid nondestructive data acquisition, in addition to its convenience and low cost of implementation. The major objective of this paper is to introduce this new imaging technique to the tribology community. The key considerations entering into the design of a scanning tunneling microscope for routine and high-resolution surface roughness measurements on practical specimens in air are described. Technical details are presented, along with some examples of its performance. Limitations of this microscopy technique and solutions are discussed.