Study of the electron field emission and microstructure correlation in nanocrystalline carbon thin films

Nanocrystalline carbon thin films were deposited by hot-filament chemical v apor deposition using a 2% concentration of methane in hydrogen. The films were deposited on molybdenum substrates under various substrate biasing con ditions. A positive bias produced a continuous flow of electrons from the f ilament onto the substrate, while a negative bias caused the substrate to b e bombarded with positive ions. Films were also grown under no bias, for co mparison. Differences in the electron field emission properties (turn-on fi elds and emitted currents) of these films were characterized. Corresponding ly, microstructural differences were also studied, as characterized with at omic force microscopy and Raman spectroscopy. Films grown under electron bo mbardment showed lower turn-on fields, smoother surfaces, and smaller grain s than those grown under ion bombardment or no bias. A correlation between the enhanced emission properties and the nanocrystalline carbon material pr oduced by the low-energy particle bombardment was found through the paramet ers obtained using spectroscopic ellipsometry modeling. The results confirm the significant role of defects on the electron field emission mechanism. (C) 2001 American Institute of Physics.