Initial growth process of carbon nanowalls synthesized by radical injection plasma-enhanced chemical vapor deposition

摘要

We synthesized carbon nanowalls (CNWs) using radical injection plasma-enhanced chemical vapor deposition. The initial growth process of CNWs was investigated with and without O_2 gas addition to a C_2F_6 capacitively coupled plasma with H radical injection. In the case of the CNW synthesis without the addition of O_2 gas, scanning electron microscopy (SEM), transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy revealed that a 10-nm-thick interface layer composed of nanoislands was formed on a Si substrate approximately 1 min prior to CNW formation. In contrast, with O_2 gas addition, SEM and XPS revealed that an interface layer was not formed and that CNWs were grown directly from nanoislands. Moreover, Raman spectroscopy suggested that the interface layer was composed of amorphous carbon and that O_2 gas addition during CNW growth is effective for achieving a high graphitization of CNWs. Therefore, O_2 gas addition has the effect of reducing the amorphicity and disorder of CNWs and controlling CNW nucleation.