Suk Jae Chung

Deposition of n-type diamondlike carbon by using the layer-by-layer technique and its electron emission properties

We have studied the electron emission behavior of the diamondlike carbon (DLC) films by plasma enhanced chemical vapor deposition using a layer-by-layer deposition, in which the deposition of a thin layer of DLC and a CF4 plasma exposure on its surface were carried out alternatively. The electron emission current increases with CF4 plasma exposure time. The increase in emission current appears to be due to the n-type behavior of the DLC.

Self-organized carbon nanotips

We have developed a carbon nanostructure, which is comprised of high-density carbon nanotips on a graphite layer. These carbon nanotips, with tip diameters of ∼10 nm, are grown by high-density plasma chemical vapor deposition onto Ni-coated Si using an inductively coupled plasma. The Ni on Si changes into NiSi2 by substrate heating. First, a carbon buffer layer and then a graphene sheet are formed on the NiSi2. Then, the carbon nanotips are grown by a C2H2/H2 plasma on the graphene sheet. The carbon nanotips show good adhesion to the substrate and are almost aligned, with an average length of 110 nm. They exhibit a turn-on field of 0.1 V/μm, a field amplification factor of ∼13 000, a current density of 2 mA/cm2 at a field of 2 V/μm, and uniform electron emission.

Novel plasma chemical vapor deposition method of carbon nanotubes at low temperature for field emission display application

Abstract We developed a novel growth method of aligned carbon nanotubes. A high density plasma chemical vapor deposition (PECVD) has been employed to grow high-quality carbon nanotubes (CNTs) at low temperatures. High-density, aligned CNTs can be grown on Si and glass substrates. The CNTs were selectively-deposited on the patterned Ni catalyst layer, which was sputtered on Si. The CNTs exhibited a turn-on field of 0.9 V/μm and an emission current of 480 μA/cm 2 at a field of 3 V/μm.

STABILITY OF ELECTRON EMISSION CURRENT IN HYDROGEN-FREE DIAMOND-LIKE CARBON DEPOSITED BY PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION

We have studied the electron emission characteristics of the hydrogen-free diamondlike carbon (DLC) and conventional DLC films. The electron emission current of conventional DLC increases at first and then decreases continuously with bias stress time. The emission current of the hydrogen-free DLC, deposited by the layer-by-layer technique, increases at first and then stabilizes with increasing stress time. The resistivity of the hydrogen-free DLC decreases after long bias stress, and that appears to be due to the changes in the density of states in the gap of the hydrogen-free DLC.

Field emission from carbon nanotubes grown by layer-by-layer deposition method using plasma chemical vapor deposition

Abstract We developed a noble carbon nanotube (CNT) deposition method using a layer-by-layer technique, in which the deposition of a thin layer of CNTs and a CF4 plasma exposure on its surface were carried out alternatively. Owing to the difference in the etch rate between amorphous carbon, graphite and CNTs by CF4 plasma, we can selectively etch out some of the unwanted amorphous carbon and graphite phases from the CNTs. In addition, CF4 plasma treatment on the surface can open the ends of the deposited CNTs and results in the increase of emission currents. The new CNTs exhibited a turn-on field of 1.2 V/μm.

Field emission properties of ta-C films with nitrogen doping

We have studied the electron emission characteristics of tetrahedral amorphous carbon (ta-C) films with different nitrogen content. With increasing N content in ta-C, the room-temperature conductivity as well as the emission current decreases and then increases, resulting in minima. The Fermi level shifts toward the conduction band and, thus, the work function decreases by N doping in ta-C, however, the emission currents of doped ta-C films are less than those of undoped ta-C.

Field emission of nitrogen doped diamondlike carbon films deposited by plasma enhanced chemical vapor deposition

The N doping effect on the electrical conductivity and electron emission property for diamondlike carbon (DLC) films deposited by plasma enhanced chemical vapor deposition (PECVD) has been studied. The electrical conductivity can be widely varied by n-type doping of the DLC. The relationship between the prefactor of conductivity and the conductivity activation energy satisfy the Meyer–Neldel relation: σ0=σ00 exp(AEa) with A=19 eV−1 and σ00=9×10−8 S/cm. The emission current for heavily N doped DLC films is much higher than that of undoped DLC even though the lightly N doped film shows much smaller current.

Effect of N doping on the electron emission properties of diamondlike carbon film on a 2-in. Mo field emitter array panel

We have studied the enhancement of field-emission characteristics by hydrogen-free nitrogen-doped diamondlike carbon (DLC) coating on Mo-tip field emitter arrays by a layer-by-layer technique using plasma-enhanced chemical vapor deposition. The Spindt-type molybdenum tip is used as an emission source without a resistive layer on the silicon substrate. The maximum emission current for each pixel was increased from 160 to 1520 μA by a 20 nm N-doped DLC coating. Furthermore, the emission current from DLC-coated field emitter arrays (FEAs) is more stable than that of noncoated FEAs.

Relationship between field emission characteristics and hydrogen content in diamondlike carbon deposited by the layer-by-layer technique using plasma enhanced chemical vapor deposition

We deposited diamondlike carbon (DLC) films of various hydrogen contents by plasma enhanced chemical vapor deposition. The hydrogen content in the DLC film was controlled by a novel technique called a layer-by-layer deposition, in which the deposition of a thin layer of DLC and a CF4 plasma exposure on its surface were carried out alternatively. The DLC films with different hydrogen content could be obtained by varying the CF4 plasma exposure time. The emission current increases and turn-on field decreases with decreasing hydrogen content in the DLC film.

Surface roughness and magnetic properties of L10 FePt films on MgO/CrRu/TiN

Processes for making well ordered L10 FePt thin films with root-mean-square surface roughness close to 0.4 nm, perpendicular anisotropy greater than 5 kOe and perpendicular squareness near 1 using a deposition temperature of 390 °C have been developed. In this study, we focused on reducing the ordering temperature and smoothness of L10 FePt films, while achieving good perpendicular magnetic properties by using MgO/CrRu/TiN or MgO/CrRu/Pt seed layers on Si/SiO2 substrates. It was found that the chemical ordering of L10 FePt films is strongly affected by the insertion of a sputtered MgO seed layer, and the CrRu (002) texture on a (002) textured MgO seed layer is substantially improved at high DC power. In order to prevent Cr diffusion, TiN and Pt films were inserted between the CrRu and FePt films. It was found that the smoothness, L10 FePt ordering, and perpendicular magnetic properties were strongly improved by the TiN barrier layer compared to the Pt barrier layer. Increased TiN thickness improved the pe...