Enhancement of the characteristics of carbon nanofibers by the on/off cyclic modulationof C2H2/H2 flow

Abstract

Carbon nanofibers were deposited on silicon oxide substrate by thermal chemical vapor deposition method. Forthe enhancement of the characteristics of carbon nanofibers, the source gases (C2H2, H2) flows were intentionallymanipulated as the cyclic on/of modulation of C2H2 flow. By the cyclic modulation process during the initial depositionstage, the formation density of carbon nanofibers on the substrate could be much more enhanced. The diameter of as-characteristics of carbon nanofibers by the cyclic modulation process was discussed in association with the hydrogen gasetching ability.Key words Carbon nanofibers, Cyclic modulation of C2H2/H2 flow, Nucleation density, Surface morphology, Thermal CVD1. IntroductionDue to their fascinating geometries and unique electri-cal properties, carbon nanofilaments, called carbon nan-otubes if hollow and carbon nanofibers if filled [1-3],have been regarded as the promising materials to fabri-of the carbon nanofilaments, up to the present, variousmethods have been introduced, such as arc discharge[7], pyrolysis [8], laser ablation [9], plasma or thermalchemical vapor deposition methods [4, 10], and so forth.Among these methods, chemical vapor deposition meth-ods have been noted for having the advantages of thehigh purity and the high yield of carbon nanofilamentsformation [11]. Despite these advantages, however, thepractical applications of carbon nanofilaments to fulfillthe industry’s expectations still requires the massive pro-duction and/or the higher purity of carbon nanofilaments.Therefore, the development of their formation process toenhance their purity and formation yield would be inevi-