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 probe tip of scanning tunneling microscope (STM) for imaging atoms on chemically active surfaces in an ultra-high vacuum (UHV) environment. When a clean Si(1 1 1)-7 x 7 surface was scanned with an as-prepared CNT tip, the atomic 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 the present case) coming out of the CNT tip. When the tip was once annealed thermally in UHV, the clear atomic nature was observed in STM images for a long period of time without any image degradation even if the tip touched the sample surface. Stable atomic STM imaging with the CNT tip in UHV will make the scanning prope microscope more reliable than before for the future application. (C) 2001 Elsevier Science B.V. All rights reserved.