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Carbon Nanotube Tip for Scanning Tunneling Microscope

We attached multiwall carbon nanotubes (CNTs) to the top of a Au tip using a manipulation system, and used the tip as a probe for a scanning tunneling microscope (STM). We measured Au(111) surfaces using an ultrahigh-vacuum-STM with an electrochemically etched Au tip and a multiwall CNT tip attached to the top of the Au tip. When the CNT tip was cleaned by heating in a coil filament, we observed the 22×√3 reconstruction of clean Au(111). With an uncleaned CNT tip, many adsorbates were observed along the reconstruction, which may be contaminants desorbed from the CNT tip. The stability of the CNT tip depends on its length, diameter and the contact to the base material. Thus far, we have obtained good resolution using a CNT with a length of less than 200 nm. We found that when the CNT was not vertical to the sample surfaces, the tip-surface interaction increased the stability of the CNT tip.