Synthesis of Vertically Aligned Carbon Nanofibers-Carbon Nanowalls by Plasma-Enhanced Chemical Vapor Deposition

摘要

Vertically aligned carbon nanofibers (VA-CNFs)-carbon nanowalls (CNWs) have been prepared on a silicon (Si) substrate by plasma-enhanced chemical vapor deposition. The VA-CNFs-CNWs were formed at bias voltage of -185 V, whereas conventional VA-CNFs were synthesized under conditions of high bias voltages. Degenerated CNWs with turbostratic graphite structure were created on amorphous carbon layer around CNFs like a flag attached to a pole, which is evidenced by scanning electron microscopy, transmission electron microscopy, electron diffraction, and micro-Raman spectroscopy. Electron field emission characteristics of VA-CNFs-CNWs with unique microstructure, fabricated on the Si substrate, were primarily investigated. As a result, the VA-CNFs-CNWs showed the turn-on and the threshold fields of 1.7 V · μm~(-1) and 3.35 V ·μm~(-1) with current densities of 10 nA · cm~(-2) and 1 μA · cm~(-2), respectively. The field enhancement factor β was estimated to be 1059 by using Fowler-Nordheim theory.