Woo-Yong Sung

Field emission characteristics of CuO nanowires grown on brown-oxide-coated Cu films on Si substrates by conductive heating in air

CuO nanowires were grown on brown-oxide-coated Cu films on Si substrates by conductive heating in air and their field emission characteristics were investigated. High resolution scanning electron microscopy showed that the CuO nanowires grew perpendicularly to the substrate, and their length and radius could be controlled by varying heating temperature and time. It was found that the lengths of the CuO nanowires were saturated to a certain point with respect to the heating temperature, and the increasing heating time increased the uniformity of the CuO nanowires in length. The field emission characteristics were strongly affected by the formation of the brown-oxide layer and the morphologies of the CuO nanowires governed by heating temperature and time.

Fabrication of Field Emitters with Carbon Nanotubes Using Triboelectricity

The triboelectricity method uses no adhesives but it induced by the difference of triboelectric series between materials can vertically align the carbon nanotube (CNT) emitters. CNTs are attached on a silicon wafer by dip-coating method, and then vertically aligned by the triboelectricity. The field emission property is enhanced up to 270 µA/cm2 at 4 V/µm after the activation of the emitters but no emission is observed at the same electric field before activation. The triboelectricity method avoids inevitable contamination due to the adhesives of taping method and is suitable for the conventional fabrication process which uses indirect-attachment method of CNTs.

Field Emission Characteristics of Carbon Nanocoils Grown on Copper Micro-tips

Carbon nanocoils (CNCs) were synthesized by using thermal chemical vapor deposition of C2H2 and NH3 gas at 600degC over copper micro-tips formed on silicon substrate. Copper micro-tips were formed by the high current pulse electroplating in order to investigate the effect of the surface morphology of the substrate on the growth of carbon nanostructures. We prepared three kinds of substrates with surface of electroplated copper micro-tips, electroplated copper film and evaporated copper film. Among the substrates, CNCs grown on the copper micro-tips showed the highest field emission characteristics

Density control of carbon nanofibers on titanium buffer layer using electroplated Ni catalyst

With a view to controlling the density of carbon nanofibers (CNFs), the density of Ni catalysts was varied using direct current (dc) electroplating technique coupled with titanium (Ti) buffer layer which is deposited between catalytic layer and substrate. The dc electroplating technique is used for the deposition and formation of islands of Ni catalysts simultaneously, without any additional process. The islands of Ni catalysts were formed on the substrate with Ti buffer layer, while the smooth and continuous film of Ni catalyst was formed on the substrate without the Ti buffer layer, using the same electroplating process. The site density of Ni catalysts was controlled via the dc electroplating technique coupled with the deposition of Ti buffer layer successfully. Then, CNFs were synthesized using a direct current plasma enhanced chemical vapor deposition (dc-PECVD) system at a temperature of 480°C. The morphologies of the electroplated Ni catalysts and CNFs were compared at different electroplating cond...

Synthesis of Carbon Nanofibers Formed on Density-controlled Ni Catalyst

Preformed nickel nanoparticles are utilized for catalyst to synthesize carbon nanofibers (CNFs). The nanoparticles are attached to the substrate by spraying colloidal solution containing themselves and drying out. Then, CNFs were synthesized by using DC plasma-enhanced chemical vapor deposition (DC-PECVD) at 480degC. Spraying-drying method is very simple to obtain particle-type catalyst with uniform diameter on the substrate and allows easy control of the catalyst density by adjusting the concentration of colloidal solution as well as cycles of spraying-drying process. The field emission characteristics of the CNFs grown by the aid of preformed nickel catalyst are investigated

Field emission characteristics of carbon nanotube-copper composite emitters formed by composite plating

The field emission characteristics of CNT-Cu composite emitters formed by composite electroplating method were investigated. Multi-walled carbon nanotubes (MWNTs) synthesized by chemical vapor deposition were used. The results showed that the turn-on field is about 2.34 V//spl mu/m with the current density of 0.1 /spl mu/m/cm/sup 2/. We observed that more emission sites located near edge than center and the emission current was stable. It is expected that CNT-Cu composite emitters can be applied to the FEDs and large area vacuum lighting sources.

Field emission properties of CuO nanowires formed on a bulk-micromachined glass substrate

In the present work CuO nanowires were formed on a bulk micro-machined glass substrate to control their density and thus enhance the field emission characteristics.