NanoTribology

The term tribology is derived from the Greek word "tribo" meaning rubbing and "logy" meaning knowledge. The original applications by the Greeks of tribology were in trying to understand the motion of large stones across the earth's surface. Today tribology has grown to include the methodical study of friction, lubrication, and wear.

Tribology plays a critical role in diverse technological areas. In the advanced technological industries of semiconductor and data storage, tribological studies help optimize polishing processes and lubrication of data storage substrates. In traditional industries such as automotive and aerospace, tribological studies help increase the lifespan of mechanical components.

Many industrial processes require a detailed understanding of tribology at the nanometer scale. The development of lubricants in the automobile industry depends on the adhesion of nanometer layers (mono layers) to a material surface. Assembly of components can depend critically on the adhesion of materials at the nanometer length scale.

There are a number of traditional tools for characterizing friction, lubrication and wear. The most common characterization tool is the tribometer having several configurations such as pin-on-disk, ball on flat, and flat on flat, etc. Generating motions at the nanometer scale is extremely challenging. New characterization techniques are required to understand tribology at the nanometer scale.

The atomic force microscope is now being routinely applied for studying nanoscale tribology. The natural extension of the AFM for tribology applications is derived from the motion of a nanometer-sized stylus in the AFM over a surface. Although traditional tribology testing is not done with an AFM, many new types of applications are possible.

Examples of the application of AFM to tribology include:

• Direct three-dimensional visualization of wear tracks, or scars on a surface.
• Measurement of the thickness of solid and liquid lubricants having nanometer or even monolayer thickness.
• Measurement of frictional forces at the nanometer scale.
• Surface characterization of morphology, texture, and roughness.
• Evaluation of mechanical properties such as hardness and elasticity, and plastic deformation at the nanometer scale.

A major advantage of the AFM for tribological studies is that the AFM can be routinely used on all types of materials. Materials commonly studied include: ceramics, metals, polymers, semiconductors, magnetic, optical, and biomaterials. AFM investigations are usually made in ambient air environment. It is possible to make AFM studies in a vacuum or liquid environment.