Electrical conduction of carbon nanotube atomic force microscopy tips: Applications in nanofabrication

This paper reports the electrical transport properties of the interface of a multiwalled carbon nanotube (MWNT) in physical end contact with a hydrogen-passivated Si surface and a Pt surface. The electrical measurement was performed in an atomic force microscope (AFM) with a MWNT attached to a scanning probe in contact mode at approximately 50% relative humidity. AFM force-distance spectroscopy was employed to set the degree of contact between the MWNT tip with the surface. The tip-substrate interface dominates the electrical measurement in this configuration, showing electrical conductivity characteristics indicative of the tip-substrate junction. MWNT tips in contact with a Pt surface exhibit a linear I-V behavior with electrical resistances in the range of 30–50kΩ, demonstrating the metallic nature of the MWNT. Results are presented for the investigation of the current-induced joule heating limitations of MWNT tips under ambient conditions. Thinning of the outer walls through a current-induced thermal oxidation process is observed at a current greater than 5μA, exhibiting a current density of greater than 106A∕cm2. For a MWNT tip in end contact with a highly p-doped silicon surface, a diode-like metal-insulator-semiconductor (MIS) junction is measured. Modeling of the MIS junction is presented and compared to the experiments.