Scanning auger electron microscopy evaluation and composition control of cantilevers for ultrahigh vacuum atomic force microscopy

Atomic force microscopy (AFM) tips have been evaluated on a submicrometer scale using a scanning Auger electron microscope (SAM) with a field emission electron gun. The commercially available AFM tips on the cantilever as supplied were usually covered with carbon and oxide layers as identified by the Auger spectra. A piezoresistive cantilever can be easily heated by passing a small current into the resistive film on the lever. The carbon and oxide layers can be reduced by heating the cantilever at temperatures higher than 700 degrees C and simultaneously irradiating with an electron beam. However, the layer in which carbon is strongly combined with the Si substrate cannot be completely removed by the above method. The tip then was cleaned by Ar ion sputtering and thermally oxidized to form a clean Si oxide layer. The oxide layer was removed only by heating at 700 degrees C. Thus a clean Si tip can be obtained in an ultrahigh vacuum (UHV) AFM chamber by heating the tip, which is then covered with clean Si oxide as a protective layer.