Study on structural evolution of carbon nanowalls by one-step thermal chemical vapor deposition

The growth mechanism of carbon nanowalls (CNWs) by catalyst-free thermal chemical vapor deposition (TCVD) is investigated. CNWs are synthesized by using TCVD method at 1200 °C under atmospheric pressure, with ethanol and hydrogen gas serving as carbon source and carrier gas, respectively. The structural evolution of CNWs was characterized by scanning electron microscopy (SEM) and Raman spectroscopy. SEM analysis revealed that as-grown CNWs on the substrate consist of vertically oriented, few-layer graphene nanosheets. The carbon islands and carbon layers derived from these islands play an important role as active sites for the formation of CNWs. Raman analysis showed that the crystallinity of CNWs increases with growing deposition time, indicating the structural evolution of crystalline CNWs. Transmission electron microscopy (TEM) analysis revealed that CNWs are composed of few-layer graphene sheets. This work proposes the growth mechanism of CNWs by a novel facile one-step TCVD approach.