A transfer-matrix method was used to study defects in a tight-binding model for C nanotubes. Calculations were made of the reflection coefficient, R, for a simple barrier which was created by a point-like defect of strength, E, in armchair (Na,Na) and zig-zag (Na,0) nanotubes for the entire energy range, W, and for an arbitrary number of conducting channels. It was found that R scaled at the Fermi level (W = 0) when R = s(E/t)2/Na2, where t was the hopping parameter, s was equal to about 1/6 for armchair nanotubes and was equal to about 1/2 for the zig-zag nanotubes. Similar calculations were performed for a so-called 5-77-5 defect, and the results were found to be like those obtained for a strong point defect with E = 6t.

Reflection by Defects in a Tight-Binding Model of Nanotubes. T.Kostyrko, M.Bartkowiak, G.D.Mahan: Physical Review B, 1999, 59[4], 3241-9