Field emission from diamond nanotips treated with nitrogen plasma immersion ion implantation

Diamond nanotips were synthesized on diamond/Si substrates by using a microwave plasma-enhanced chemical vapor deposition process. The diamond nanotips are ∼1 μm in height and the diameter at the bottom of a nanotip is ∼200 nm. The as-grown diamond nanotips exhibit excellent field emission characteristics after treating with nitrogen plasma immersion ion implantation (PIII) for 10 min. A low turn-on field of 3 V μm-1 and a high current density of 4 mA cm-2 at 9 V μm-1 are achieved. The morphologies of diamond nanotips are unchanged after the nitrogen PIII treatment. The diamond quality reduces with treatment time. The sp3 bonds in diamond can be broken by the nitrogen ions accelerated by the pulse voltage of -25 kV, which results in G peak broadening in Raman spectra. Several nanoscale amorphous regions are generated in a crystalline diamond nanotip, observed by the high resolution transmission electron microscope. The improvement of field emission properties is correlated to the amorphous regions and possible implantation-induced atomic defects