CVD growth and field emission characteristics of nano-structured films composed of vertically standing and mutually intersecting nano-carbon sheets

摘要

Nano-structured films composed of rather flat nano-carbon sheets which roughly stood vertically on Si wafers and which intersected each other at large angles were grown by means of a high-power microwave-plasma chemical-vapour-deposition (MWPCVD) method. The structure of the fabricated films was investigated using scanning electron microscopes and Raman spectroscopy. Field emission (FE) currents obtained from these films reached 50 mA/cm~2 at a macroscopic electric field of 3.6 V/mu m. The observed FE characteristics were analyzed using a modified Fowler-Nordheim (F-N) equation where the field enhancement factor and effective emission area were treated as field-dependent parameters. It was found from the analysis that the vertically standing nano-carbon flat sheets had larger field enhancement factors and less FE areas, compared with those obtained for wrinkled nano-carbon sheets previously reported by the authors. It is suggested that the observed variations in the FE current without saturation behavior as a function of the macroscopic electric field can be explained in terms of an effective surface geometry phenomenon of the concerned films.