The role of an amorphous carbon layer on a multi-wall carbon nanotube attached atomicforce microscope tip in making good electrical contact to a gold electrode

Abstract

Multi-wall carbon nanotube (MWNT) attached atomic force microscope (AFM) tips(MWNT tips) have good potential for use in AFM lithography. Good conducting MWNTtips are needed in such applications. However, characterizing the conductance of MWNTtips is nontrivial: making a good electrical contact between the MWNT and electrode isdifficult. We observed that MWNT tips produced by hydrocarbon-deposition attachmentusually do not make good electrical contacts to gold electrodes because of the thin andrough amorphous carbon layer on the MWNT that was unintentionally deposited duringthe attachment. We found that good contacts can be made if a more amorphous carbonlayer is deposited to form a thick and smooth amorphous carbon layer on MWNTs. Goodcontact was made either by transformation of the amorphous carbon layer intoa conducting or peel-off layer, exposing the bare MWNT surface. MWNT tipswith an exposed MWNT surface showed the well-known high-current-flowingcapacity and the stepped-cutting behavior of bare MWNTs. The peeling-off behaviorof a thick amorphous carbon layer may be utilized in producing bare-surfacedMWNT tips that have good conductance and therefore are useful for applications.