Creation of unique shapes by coordination of alumina nanopores and carbon nanowalls

This work presents experimental results on the synthesis of carbon nanowalls (CNWs) with predefined morphology on the surface of the nanoporous alumina membrane using two different methods, namely radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) and radical-injection (RI)-PECVD. Obtained samples were characterized by the methods of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. From the microstructure analyses of CNWs, it has been observed that there is a time dependence on the reproducibility of membrane morphology by CNWs. At the early stage of nanowalls growth, nanowalls prefer to grow around the edges of nanopores and continue to grow vertically with time. In RF-PECVD, the nanopores' size begins to shrink drastically and pores are completely covered by secondary flake-like nanowalls after 25 minutes of growth. In the case of CNWs grown using RI-PECVD, nanowalls are more vertical and self-supported. This is because of the rapid and sustained production of hydrogen radicals that prevent the secondary growth of carbon nanowalls. In addition, the influence of pores diameter and membrane thickness on the growth of RI-PECVD CNWs was revealed.