Growth of Carbon Nanotubes by Sublimation of Silicon Carbide Substrates

摘要

Aligned carbon nanotubes (CNT’s) have been found to form on both the Si and C faces of silicon carbide (SiC)wafers at high temperature. The CNT’s form when the SiC wafer is exposed to temperatures in the range 1400-1700℃under moderate vacuum. The CNT’s are aligned roughly parallel to the surface. After a half hour at 1700℃ undervacuum of 10-4torr, a near continuous CNT layer about 250nm thick is formed. The entire surface of the SiC is coveredwith CNT’s including both single and multiwalled tubes, and some graphitic carbon. SEM, TEM, AFM, XPS andRaman scattering measurements have been used to analyse the CNT/SiC structures. The metal catalyst free CNT’s onSiC exhibit low density of structural defects and are very straight. The carbon source is believed to be residual carbonfrom the SiC left on the surface after preferential evaporation of Si. It is speculated that CNT's growth is catalysed bylow concentrations of residual oxygen in the chamber during growth. The vacuum conditions can significantly affectCNT's growth. Single wall carbon nanotubes are evident in Raman spectra on the samples grown at 10_(-3 )Torr, not onthese grown at 10-5Torr.