Role of Negative Electric Field Biasing on Growth of Vertically Aligned Carbon Nanotubes Using Chemical Vapor Deposition

Abstract

Vertically aligned carbon nanotubes (CNTs) were grown on a Si substrate by thermal chemical vapor deposition (CVD) and direct current plasma-enhanced CVD with a negative electric field. By contrast, under a positive electric field, CNTs grew randomly. The morphologies of the CNTs grown on Si and quartz substrates were compared to clarify the mechanism of aligned CNT growth. CNTs grown on quartz showed a random structure regardless of the polarity and amplitude of applied electric field. It is noted that the Fe catalysts on the tips of aligned CNTs were apparently elongated compared with those of randomly grown CNTs. The present observations suggest that aligned CNT growth might be due to the electrostatic force acting on the electrons drawn toward the tips of CNTs by negative electric field.