Scanning tunneling microscope investigation of carbon nanotubes produced by catalytic decomposition of acetylene

A detailed scanning tunneling microscopy (STM) study of carbon nanotubes prepared by catalytic decomposition of acetylene over a supported transition metal catalyst is reported. Nanotubes with diameters in the 10-nm range and others with diameters as small as 1 nm were found. The mechanism of STM image formation and image deconvolution with respect to the tip shape are discussed, as well as the corrections which have to be applied when measuring by STM nanotube diameters in the ranges of 10 nm and of 1 nm, respectively. The behavior of a nanotube crossing steps on the graphite surface is analyzed. Modified height values measured on a single-wall nanotube in regions where it was subjected to strong mechanical stresses indicate changes in the electrical conductivity by several orders of magnitude. Carbon nanotubes are found to be good candidates to be used for STM tip shape characterization in the nm range.