A spectroscopic study on surface and structural transitions of carbon nanotubes under different atmospheres

Abstract

We demonstrate structural transitions of carbon nanotubes using Raman spectroscopy under air, Ar, and mixed H₂ (10%)/Ar atmospheres. In the H₂ (10%)/Ar atmosphere, the G-mode peak shifted toward lower frequency with increasing temperature, which occurred to a far lesser extent in air and Ar atmospheres. This indicates that H₂ reacts more actively with surface carbon atoms in graphene layers than with others because of an etching effect. The temperature coefficients of the frequency changed from −0.014 to −0.018 with an increase in the carbon–carbon distance.