Field Emission Current Measurements Research Articles

Morphology Control of Patterned Carbon Nanofiber Arrays for Field Emission Applications

Carbon nanofibers (CNFs), grown by dc plasma-enhanced chemical vapor deposition, have differences in morphology and resulting field emission properties depending on underlying buffer layers. We patterned 200-nm-sized Ni catalyst dots, with 2–5 µm spacing, by e-beam lithography and obtained regularly spaced vertically aligned CNF arrays. CNFs, grown on Ti-buffered Si substrates, showed a needle like shape with a high aspect ratio, but CNFs directly grown on Si substrates, had a cone like shape. The former showed a smaller turn-on field (11 V/µm) than the latter (27 V/µm), in field emission current measurements. Moreover, the maximum current density of the CNF array on Ti was as high as 10 A/cm2.

Surface resistance and field emission current measurements on chemically vapour depositedpolycrystalline diamond measured by scanning probe methods

Scanning tunnelling microscopy (STM) and current imaging tunnelling currentspectroscopy (CITS) methods were performed on polycrystalline diamond filmsgrown on silicon substrates grown by microwave plasma-enhanced chemical vapourdeposition. Large tunnelling currents were observed at some grain boundariesand crystal surfaces with secondary grains. Following atomic force microscopy(AFM) measurements, we performed scanning probe contact current (SPCC)measurements to investigate the spatial variation of electrical resistance on the surface byusing an AFM cantilever in contact mode. The conducting grain boundaries andfacets were observed on both boron-doped and undoped samples. For microscalecharacterization of the field emission properties, we performed scanning probefield emission current (SPFEC) measurements. From the results of STM/CITS,AFM/SPCC and SPFEC, it is concluded that the specific grain boundaries andfacets on polycrystalline diamonds work as initial points of electron emission andcause high field emission current through a conducting pass formed in the bulk.

Scanning probe field emission current measurements on diamond-like carbon films treatedby reactive ion etching

Nitrogen-doped chemical vapour deposited diamond-like carbon (DLC) filmswere treated by reactive ion etching system under various conditions ofCHF3 gas successively after pre-treatment with oxygen. Atomic force microscopy and Ramanspectroscopy were carried out in order to characterize the surface morphology and chemicalbond, respectively. Scanning tunnelling microscopy was used in order to investigate thesurface state of the DLC films at the nanoscale level. Scanning probe field emission currentmeasurement was performed in order to obtain the emission current mapping.The emission sites appeared to a great extent after the surface treatment byCHF3 gas and a clear activation effect was observed. We confirmed that the surface treatment usingCHF3 gas affected not only the appearance of emission sites but also the activation process.

Scanning Probe Field Emission Current Measurements on Polycrystalline Diamond Films

Scanning Probe Field Emission Current Measurements on Polycrystalline Diamond Films

Spatial variation of field emission current on nitrogen-doped diamond-like carbon surfaces by scanning probe method

Field emission characteristics of nitrogen-doped diamond-like carbon (DLC) films deposited by the radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) method were investigated by the scanning probe system specially designed for the micro-scale field emission current measurements. The structural changes in the films were examined by using Raman spectroscopy. Random and inhomogeneous distribution of electron emission sites was observed. The emission current and conductivity of the films were significantly increased with self-bias voltage. Activated electron emission characteristics were observed in all samples and showed stable electron emission. The activation of the films was directly related to emission site size. It indicated that electron emission activation possibly originated from the changes in sp 2 and sp 3 bonding ratio and/or formation of conductive channels.