The growth mechanism and field-emission properties of single carbon nanotips

摘要

We study the self-aligned growth of a single carbon nanotip on a sharp metal tip via the field-emission-induced growth method. Under typical growth conditions, a micron long nanotip can be formed in around 10 s by field emission in the presence of acetylene gas at similar to 10(-2) mbar. The tip radius of the carbon nanotip can be as small as 5 nm, while its length is determined by the growth duration. Electron energy loss spectroscopy ( EELS) analysis in a transmission electron microscope revealed that the carbon nanotip is amorphous carbon with predominant sp(2) bonding. The growth mechanism of the carbon nanotip is discussed to explain the formation of the nanotip and its carbon matrix. Field-emission measurements showed that emission from the carbon nanotip follows the Fowler-Nordheim equation, suggesting that the tip shows metallic behaviour as far as field emission is concerned. A high emission current stress cycle is found to improve the emission current stability significantly.