Electron field emission properties of nanodiamonds synthesized by the chemical vapor deposition process

Nanodiamonds, doped with nitrogen, were successfully synthesized by using urea/methanol saturated solution as nitrogen source and in situ application of negative bias voltage during the growth period. Scanning electron microscope and Raman spectroscopic examinations reveal that increasing the urea/methanol ratio in the gas mixture markedly influences the field emission properties of diamond films, but insignificantly alters their structure and morphology. The diamond films thus obtained possess good electron field emission properties (E0=2.35 V/μm, Je=30.2 μA/cm−2, and effective work function φe=0.028 eV). Converting the grains of diamond films from submicrons into nanosize (∼50 nm) via the application of bias voltage in situ further improves these field emission properties. The turn-on field decreases to E0=1.88 V/μm, the field emission capacity increases to Je=118.2 μA/cm2 (at 6.5 V/μm applied field), and the effective work function decreases to φe=0.017 eV.