Silicide-induced multi-wall carbon nanotube growth on silicon nanowires

Abstract

A novel multi-walled carbon nanotube (MWNT) growth process is reported based oncarbon incorporation in a nickel catalyst layer deposited via plasma-enhancedatomic layer deposition (PEALD) on silicon nanowires and silicon wafer substrates.As-deposited PEALD Ni films containing relatively high amounts of carbon (>18 at.%) were observed to promote the growth of MWNTs upon post-deposition rapid thermalannealing. For these films the carbon originated from the ALD precursor ligand andMWNT growth occurred in the absence of a vapor-phase carbon feedstock. MWNT growthrelied on the formation of nickel silicide at the PEALD Ni/Si interface whichincreased the local carbon concentration in the Ni film sufficiently to promotecarbon saturation/precipitation at Ni catalyst grains and nucleate MWNT growth.Similar MWNT growth from annealed PEALD Ni films was not observed onSiO2-coated Si wafer substrates, consistent with the role of silicidation in the observedNi-catalyzed MWNT growth on Si. This MWNT growth mode requires neither thecatalytic decomposition of a gaseous hydrocarbon source nor the high-temperaturepyrolysis of metallocene materials and purposely avoids a catalyst diffusion barrier at the Sisubstrate, commonly used in MWNT growth processes on Si.