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We have proposed a new method for in-situ doping of multiwall carbon nanotubes (MWCNTs) by catalytic CVD using nickel boron (NiB) as the catalyst. Raman spectrum measurements were carried out to determine the effects of doping using NiB catalysts with different B-concentrations at different CVD temperatures. The characteristic shifts in the Raman spectra which indicate carrier doping were demonstrated for the NiB catalyst with 18 atomic % B at the CVD temperature of 900°C. The CNT crystallinity was improved by a new catalyst structure with a B-capping layer over the NiB catalyst.

Multilayer graphene (MLG) is expected to be a low-resistance and high-reliability interconnect material replacing copper (Cu) in nanoscale interconnects. To achieve low-resistance interconnect with MLG, carrier doping is necessary since the carrier concentrations in pristine MLGs are low. In this work, the effects of bromine (Br) doping by intercalation on the carrier concentration and sheet resistance of exfoliated highly oriented pyrolytic graphite (HOPG) were investigated by measuring the Fermi level shift using ultraviolet photoelectron spectroscopy (UPS) and the four-terminal method, respectively. The Fermi level was shifted downward up to 0.63 eV, and the sheet resistance was reduced to less than 10% of that of the pristine HOPG by increasing the Br concentration. A similar Fermi level shift was observed for the commercially available CVD-MLG. Br doping is thus promising for low-resistance MLG interconnects from the perspective of carrier doping.