Field emission from single-, double-, and multi-walled carbon nanotubes chemically attached to silicon

The chemical attachment and field emission (FE) properties of single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) chemically attached to a silicon substrate have been investigated. A high density of CNTs was revealed by atomic force microscopy imaging with orientation varying with CNT type. Raman spectroscopy was used to confirm the CNT type and diameter on the surfaces. The field emission properties of the surfaces were studied and both current-voltage and Fowler-Nordheim plots were obtained. The SWCNTs exhibited superior FE characteristics with a turn-on voltage (E-to) of 1.28 V mu m(-1) and electric field enhancement factor (beta) of 5587. The DWCNT surface showed an E-to of 1.91 V mu m(-1) and a beta of 4748, whereas the MWCNT surface exhibited an E-to of 2.79 V mu m(-1) and a beta of 3069. The emission stability of each CNT type was investigated and it was found that SWCNTs produced the most stable emission. The differences between the FE characteristics and stability are explained in terms of the CNT diameter, vertical alignment, and crystallinity. The findings suggest that strength of substrate adhesion and CNT crystallinity play a major role in FE stability. Comparisons to other FE studies are made and the potential for device application is discussed. (C) 2012 American Institute of Physics. [doi:10.1063/1.3687363]