Stable atomic imaging of Si(111)-7 x 7 surface by scanning tunneling microscope with carbon nanotube tip

We demonstrated the usefulness of multi-walled carbon nanotube (CNT) as a p robe tip of scanning tunneling microscope (STM) for imaging atoms on chemic ally active surfaces in an ultra-high vacuum (UHV) environment. When a clea n Si(1 1 1)-7 x 7 surface was scanned with an as-prepared CNT tip, the atom ic nature was recognized in a very first STM image, but after a few scans, it was quickly degraded by adsorbates (most probably oxygen molecules in th e present case) coming out of the CNT tip. When the tip was once annealed t hermally in UHV, the clear atomic nature was observed in STM images for a l ong period of time without any image degradation even if the tip touched th e sample surface. Stable atomic STM imaging with the CNT tip in UHV will ma ke the scanning prope microscope more reliable than before for the future a pplication. (C) 2001 Elsevier Science B.V. All rights reserved.