Modification of metallic multiwalled carbon nanotubes properties by 50 Hz atmospheric pressure dielectric barrier discharge plasma

Abstract

In this study, multiwalled carbon nanotubes (MWCNTs) were modified using low frequency (50 Hz) nonequilibrium plasma, which was generated separately by oxygen and nitrogen dielectric barrier discharge plasma (DBD) at atmospheric pressure. The MWCNTs were treated with oxygen and nitrogen DBD plasma at atmospheric pressure under three different applied voltages, because the MWCNTs surface was closely related to the plasma treatment voltage. The surface and electrical properties of pristine and treated MWCNTs were studied using Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, while the electrical characteristics were measured using a Hall measurement and two-point probe. FTIR showed formation of oxygen-containing groups like C=O and COOH for the O2 DBD plasma, and addition of N–H vibration bending for the N2 DBD plasma. Raman spectroscopy revealed that the ratio of I D/I G increased with increasing discharge voltage of plasma. The ascended I D/I G may be ascribed to the production of several new defects owing to the introduction of oxygen- and nitrogen functional groups recognized by FTIR. The results of Hall measurement showed that the hall mobility increased with the increase of O2 and N2 DBD voltage. Highest hall mobility was measured for MWCNTs treated with nitrogen at 12 kV, which was 172.9 cm2/Vs. It was also found from the two-point probe IV curve that Ohmic behaviour of pristine MWCNTs tended to change to Schottky behaviour after DBD plasma treatment.