PLASMA CLEANING OF SILICON SURFACE OF ATOMIC FORCE MICROSCOPY PROBES

Silicon is the most common material used in fabrication of commercial atomic force microscopy (AFM) probes. However, the surfaces of the AFM probes surface are rarely clean due to adsorption of airborne and package-released hydrophobic organic contaminants. Cleaning of silicon AFM probes removes the contaminants and renders very hydrophilic probe surfaces. This work presents a simple method of cleaning silicon AFM probes. The method consists in immersing the AFM probes in the negative glow plasma of a glow discharge in air at low pressure. To avoid destruction of the AFM probes, they are kept floating. Cleaning for ten minutes in air plasma at pressure of 6 Ton and cathode current density of 50 mu A.cm(-2) provides a very hydrophilic character to the AFM probe surfaces. The cleaning effectiveness is evaluated by water contact angle measurements of the AFM probe surfaces, which showed a drastic decrease from about 90 to less than 5 degrees. Cleaning of the silicon surfaces of AFM probes and flat samples resulted in significant increase of adhesive and friction forces measured in air on hydrophilic surface of a glass sample.