Electrical Characterization of Metal-Coated Carbon Nanotube Tips

Abstract

Electrical characteristics of bare and metal-coated carbon nanotube (CNT) tips were investigated with an independently driven four-tip scanning tunneling microscope (STM). The CNT was glued on a W tip apex and wholly coated ex situ by metal thin layers. The resistance between the CNT-tip end and the W supporting tip scattered very widely from ca. 50 k to infinity for the bare tips, while coating the tip with a 6-nm-thick PtIr film stably reduced the resistance to less than approximately 10 k. The W coating was also effective for stabilizing the resistance, although they showed slightly larger resistance (ca. 50 k). The metal-coated tips kept their low resistance and flexibility even after 100 repeated contacts to an object for conductivity measurements. They are expected to be useful for nanometer-scale transport measurements with multiprobe STM as well as for conventional single-tip STM.

Coating Carbon Nanotubes with Compound Ultrathin Film: A Novel Route to Functional SPM tips

“…The lattice fringe of the CNT was clearly observed, indicating that the crystallinity of the inner MWNT was maintained. From the elemental analysis by energy dispersive X-ray spectroscopy (EDX) in TEM, the atom ratio of Pt to Ir was estimated to be 74:26, which was similar to the composition of the target [14].…”

“…Thereby, we performed more than 100 times I − V measurements, and derived the contact resistance at the CNT-tip junction of the PtIr-coated CNT tip. The contact resistance of the PtIr-coated CNT tip ranges from several kΩ to 10 kΩ, which is lower than that of W-coated CNT tip (∼ 50 kΩ) [14]. Since the PtIr is hardly oxidized in air and the W is easily oxidized, it is thought that the W thin layer was oxidized due to the exposure of CNT tips in air during the transfer from the PLD apparatus to the four-tip STM.…”

In situtransport measurements on ultrathin Bi(111) films using a magnetic tip: possible detection of current-induced spin polarization in the surface states

“…Without the metal coating, the resistance at the CNT-W junction scattered from 100 k to several M from tip to tip, which was too high for the probes in conductivity measurements. The details of the tip fabrication and its electrical and mechanical characterizations are discussed elsewhere [23,24].…”

Invited Review Article: Multi-tip scanning tunneling microscopy: Experimental techniques and data analysis

“…In order to prepare ultimately sharp tips for multi-tip STM (coated) carbon nanotubes or nanowires have been attached to tungsten tips. [66][67][68] FIG. 9.…”