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Vertically-aligned carbon nanotubes (VCNTs) are used as electron source in various field emission applications owing to its high aspect ratio, chemical inertness, mechanical strength and electrical conductivity. Here, we demonstrate that surface structure modification along with thin film coating enhances the field emission performance, such as turn-on voltage, emission site density, and stability. In the present study, VCNTs with different heights were grown on silicon wafers by thermal chemical vapor deposition followed by the structure modification of VCNTs using capillarity-driven water vapor condensation. We obtained various surface morphologies by varying the water vapor exposure time and heating temperature. In addition, the structure-modified VCNTs surfaces were coated with W and SiO2 thin films using electron-beam evaporation. It was observed that W-coated VCNTs with modified surface morphology results in the best field emission performance.

We developed high current electron emission carbon nanotube cold cathode electron sources for high power vacuum devices. To develop high power devices with electron beam, electron emission current is most important. More than 100 rnA electron emission current achieved with the optimized CNT fabrication process and its structure. The electron emission current limited by the conductivity of CNT emitters, the higher conducting emitters show higher electron emission current. Detail on the fabrication process and performance of electron beam would be presented.

We introduced a carbon-nanotube (CNT) electron beam (C-beam) for thin film crystallization and thin film transistor (TFT) applications. As a source of electron emission, a CNT emitter which had been grown on a silicon wafer with a resist-assisted patterning (RAP) process was used. By using the C-beam exposure, we successfully crystallized a silicon thin film that had nano-sized crystalline grains. The distribution of crystalline grain size was about 10 ∼ 30 nm. This nanocrystalline silicon thin film definitely had three crystalline directions which are (111), (220) and (311), respectively. The silicon TFTs crystallized by using a C-beam exposure showed a field effect mobility of 20 cm2/Vs and an on/off ratio of more than 107. The C-beam exposure can modify the bonding network of amorphous silicon with its proper energy.

We observed the bright bluish-white luminescence with naked eye from carbon nanotube electron beam exposed silicon dioxide (SiO 2 ) thin film on Si substrate. The luminescence shows a peak intensity at 2.7 eV (460 nm) with wide spread up to 600 nm after the C-beam exposed on SiO 2 thin film. The C-beam exposure system is composed of carbon nanotube emitters as electron beam source. The brightness strongly depend on the exposure condition. Luminescence characteristic was optimized by C-beam adjustment to observe with the naked eye. The cause of luminescence in the C-beam exposed SiO 2 thin film is analyzed by CL microscopy, FT-IR, AFM and ellipsometer. Decrease of Si–O bonding was observed after C-beam exposure, and this reveals that oxygen deficient defects which are irradiation-sensitive cause 2.7 eV peak of luminescence.

The effect of graphite coating on carbon nanotube (CNT) emitter arrays on field emission grown using the resist-assisted patterning (RAP) process was studied. It was found that the electron emission current and the stability of the emission current of graphite-coated CNT emitters were remarkably improved. The enhancement of the electron emission of CNT emitters after graphite coating appears to be due to the effect of graphitization between CNT emitters and the substrate. This graphitization process reduced the field-screening effect, since it unified several grown CNTs as one single emitter and improved adhesion between CNT emitters and the substrate.

We developed high performance cold cathode electron beam fabrication technique with carbon nanotube(CNT) emitters. Properties of CNT emitters and its electron emission characteristics should be compatible with application devices. Xray tubes require very high current with small cathode area and ultraviolet lamps require uniform electron emission on large area. So, we developed novel CNT electron beam with buffer and metal layer for sacrificing for structural rigidity and enhanced conductivity. We applied the novel CNT cold cathode electron beam for UV lamps and x-ray tubes for high performance UV light and x-ray image.

We studied on the fabrication and improved field emission properties of carbon nanotube (CNT) cold cathode electron emitters with electrical aging. Our CNT field emitters have improved electron emission properties with thermal and electrical aging. For the set-up of electrical aging, we used bias voltage at Joule heating appeared. Our CNT emitters show increases of electron emission at initial stage of aging and then saturation of emission current. With the electrical aging, we obtained enhanced electron emission from 3 mA to 5.5 mA and long-time stable operation.

The ring shaped high current carbon nanotube (CNT) cold cathode electron beam was developed for gyrotron application. The various circular ring shaped electron beam designed with CNT emitters for gyrotron was investigated. The circular beam design designed to have CNTs area such as, 0.2 cm2,0.3 cm2, 0.5 cm2 and 0.8 cm2. The electron emission current strongly related on the density of CNT emitters and design parameters. The field emission current depend on the ring width and could achieve electron emission current up to 160 mA.

We developed high performance carbon nanotube cold cathode electron source with molybdenum layer for vacuum nanoelectronic devices. With DC-PECVD system for the CNT growth, the high-energy ion radicals in the plasma could etch the Mo layer, and then the etched vapors coated on the CNT emitter. With the patterned Mo layer, a property of CNT emitter were improved as the emission current and the conductivity of emitters

An electron-beam-induced crystallization technique for amorphous silicon (a-Si:H) thin films was investigated. The high-energy electron beams (e-beams) transfer their energy to the silicon network, resulting in network relaxation and crystallization. The crystalline properties of the silicon film strongly rely on the e-beam exposure time and the acceleration voltage. The crystallinity of the silicon film depends on the a-Si:H growth method used. Silicon films with higher crystallinity can be obtained from thin films deposited via plasma-enhanced chemical vapor deposition (PECVD) rather than from thin films deposited via sputtering. The PECVD silicon thin film showed more than 94% crystallinity and a ∼50 nm grain size after e-beam exposure with 1500 V acceleration bias for 180 s.

We fabricated a high performance electron beam for the vacuum electronic devices with carbon nanotube (CNT) cathode. For the vacuum electronic devices application, a structure of cold cathode should be highly adhere on cathode substrate and endure a resistive heating during electron emission. For fabrication of stable electron beam, we optimized the CNT emitters and the triode structure. The structural properties of CNT emitters could be enhanced with functional coating on CNT surfaces. In this study, we developed silicon functional coating technique on CNT emitters and enhanced and stable electron emission with the coating.

We fabricated field emission electron sources and applied for the glass sealed x-ray tube for medical imaging devices. The x-ray tube consists of an electron beam with a patterned grown CNT emitters with RAP process. Those electron beam shows higher electron emission current and transmittance after glass seal. With the x-ray tube, we success to measure medical image with finger and high resolution PCBs. The fabricated x-ray tube shows electron transmission ratio (>90%) and current (>3 mA).

We developed deep UV generation techniques with home-made wide bandgap anode and carbon nanotube (CNT) based cold cathode electron beam (C-beam). The wide bandgap anodes excited with high performance C-beam. The fabrication process for anodes were developed and optimized for high performance deep UV generation. Also, the performance of C-beams optimized. With the optimized C-beam and anode, we could obtain deep UV with wavelength of 208, 226 and 244 nm. The deep-UV light sources could make new era of UV lighting technologies and industries.

The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube emitter, and the transmitted X-ray image was of high resolution.

We fabricated miniature electron beam module by using carbon nanotube electron emitters for x-ray tube application. The x-ray tubes with the beam module were fabricated with glass envelop and vacuum sealed. The miniature electron beam module was designed to achieve more than 90 % of electron transmission ratio through gate electrode with higher than 3 mA of anode current. The x-ray tube shows micro focused focal spot size and enough flux for dental imaging.

The effect of gate mesh electrode on the electron extraction from carbon nanotube emitters for high performance electron beam were studied. In the case of low electron emission regime ( 1mA/cm2) gate electrode materials and structure start to effects on electron emission current and then it makes failure in electron beams. The effects were confirmed with DC-pulse driving with different duty cycle to reduce current load on gate mesh.

The emission of a high-performance electron beam via a carbon nanotube cold cathode requires a higher electron transmission through the gate electrode. The transmittance of electrons through the gate mesh electrode strongly depends on the gate electrode structure and material properties. Therefore, thermal expansion of the gate electrode induced by the thermal load owing to the gate leakage current is a significant hurdle to be overcome. Using a high-thermal-expansion gate electrode comprised of SUS304 grid mesh, electron emission was brought to saturation when the mesh was bent upward, which was the result of a reduction of the effective electric field under the grid mesh. To mitigate the effect of this bending, a Mo grid mesh material possessing low thermal expansion introduced. The Mo grid material properties of low linear temperature expansion coefficient, high tensile strength, and low resistivity are necessary. With this grid mesh improvement, the electron emission current increased to ten times that of the SUS304 mesh grid.The emission of a high-performance electron beam via a carbon nanotube cold cathode requires a higher electron transmission through the gate electrode. The transmittance of electrons through the gate mesh electrode strongly depends on the gate electrode structure and material properties. Therefore, thermal expansion of the gate electrode induced by the thermal load owing to the gate leakage current is a significant hurdle to be overcome. Using a high-thermal-expansion gate electrode comprised of SUS304 grid mesh, electron emission was brought to saturation when the mesh was bent upward, which was the result of a reduction of the effective electric field under the grid mesh. To mitigate the effect of this bending, a Mo grid mesh material possessing low thermal expansion introduced. The Mo grid material properties of low linear temperature expansion coefficient, high tensile strength, and low resistivity are necessary. With this grid mesh improvement, the electron emission current increased to ten times tha...

A glass-sealed x-ray tube with field emission electron sources has been fabricated using carbon nanotubes (CNTs) grown on a silicon substrate by direct current plasma-enhanced chemical vapor deposition. Here, the authors report on the fabrication of CNT-based emitters, the field emission characteristics of these emitters, and the properties of the glass-sealed x-ray tube. The field emission produced a current of 5 mA with an electron transmission rate of 91.1% in a high-vacuum chamber. The glass-sealed x-ray tube had a conventional design and comprised a reflection anode, an evaporation getter, and a vacuum-sealed glass tube without additional focusing electrode requirements for ease of commercialization. Using this x-ray tube, the authors obtained x-ray images of objects, including a human finger and a commercial universal serial bus (USB) flash drive. The x-ray image allowed a 100 μm metal wire to be distinguished in the USB flash drive. The x-ray images were obtained at a dose rate of 1944 mrad/h, whic...

Deep-ultraviolet (UV) light is widely used in many industries including medicine because it has sufficient energy to kill viruses and bacteria. However, deep UV with a wavelength of 254 nm can damage human cells, so it is necessary to develop a deep-UV light source with a shorter wavelength to minimize the damage to human cells while still killing viruses. The authors used a carbon nanotube-based cold-cathode electron beam (C-beam) and wide-bandgap anode to fabricate a deep-UV light source with an emission wavelength below 250 nm. The anode was fabricated by annealing ZnO ink on a Si wafer; deep UV with a wavelength of 247 nm and full width at half maximum of 23 nm was obtained. In the case of C-beam irradiation of an anode fabricated on a quartz substrate, deep UV with wavelengths of 208, 226, and 244 nm was generated through excitation with a beam energy of 7 kV and beam currents of 0.3 and 0.5 mA.

Stable field emitters were developed using carbon nanotubes (CNTs) composite pastes with nickel (Ni) buffer layer. The paste CNT emitters showed lower threshold for field emission but which have short lifetime and unstable emission current in high emission current. In this paper, we developed the simple process of inserting Ni buffer layer between the CNT emitters and substrate. The paste CNT emitters with Ni buffer layer showed enhanced field emission properties than bare one. The lifetime of paste CNT emitters with Ni buffer layer were 9 hours 40 min. It's 22 times longer than without buffer layered one.

We optimized the triode structure for carbon nanotube electron beam(C-beam) application with carbon nanotube emitters grown with resist-assisted pattering process. The CNT emitters grown through the RAP process have a structure in which a number of CNTs are congregated, and the graphitization post-treatment process proceeded in order to enhance their adhesive strength and stability. The gate mesh was self-aligned with the carbon nanotube island for lower leakage current, resulting higher electron emission current and transmission ratio. With the optimized triode structure, the emission current show high performance with less than 1 cm2 area and C-beams operated more than 500 hours with constant current mode and DC driving.

The effect of an electron extraction electrode on electron emission for a high-performance electron beam was studied using vertically aligned carbon nanotube emitters as a cold cathode. For the lower electron emission regime (anode current less than 1 mA), the gate electrode structure and materials used had little effect on the electron emission current. However, at the higher electron emission regime (anode current higher than 1 mA), the gate electrode materials and structure do begin to deviate from an ideal Fowler–Nordheim plot by the thermal and electrostatic load on the gate electrode, especially for the small cathode area. The gate mesh bends upward under a higher current load, which then increases the gate leakage current. The upward bending in the gate mesh electrode could reduce the effective electric field by increasing the gate to cathode distance, resulting in saturation of the electron emission current. For higher electron emission currents on the anode, a gate electrode comprising a lower th...

In this study, we optimized vertically aligned carbon nanotube electron beam (C-beam) with triode structure for cathodoluminescence of Zinc Oxide (ZnO) thin films, which solution process fabricated. Efficient cathodoluminescences were observed with C-beam exposed ZnO thin films. The origin of the luminescence were confirmed by SEM measurement. The luminescence appeared to the structural modification of thin ZnO films after C-beam exposure, resulting nano-crystalline film formation.

We introduced a carbon nanotube electron beam (C-beam) exposure technique for thin films for display devices. As an electron source, the CNT emitters were placed on cathode electrode. Electrons through gate mesh, with higher accelerated energy, impact thin film on the anode plate. For display device application, amorphous silicon (a-Si:H) thin films were deposited on glass substrate and then C-beams exposed. After moderated C-beam exposure, the silicon film changes to phase of crystalline one. The structural modification was confirmed with Raman spectrum and the enhanced electrical performances were measured with I-V systems. The silicon crystalline properties were strongly depending on the C-Beam exposure conditions.

Computed Tomography (CT) using Carbon Nanotube (CNT) x-ray source is a technique of generating reconstruction images of the structure of teeth sample. A proto type CNT x-ray CT was designed for medical imaging to examine whether it could be used to analysis the equipment of medical and industrial application. The CNT field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The field emission properties showed a gate turn-on field of 3.8 V/μm at an anode emission current of 0.5 mA. The author demonstrated the x-ray source with four electrode structures utilizing the CNT emitter. The acquisitioned images were reconstructed by filtered back projection (FBP) method.

The authors fabricated an optimized electron beam (e-beam) with a carbon nanotube (CNT) cathode and triode configuration. CNT emitters grown with a resist-assisted patterning process were used as an electron source. The gate mesh was aligned with the CNT emitter islands for a lower leakage current, resulting in a higher electron emission current and transmission ratio. Additionally, the width between CNT islands and the pitch between CNTs were optimized to enhance the electric field at the tip of the CNT emitters. With the optimized e-beam module, consisting of a CNT cathode and gate mesh, CNT pitch of 30 μm, dot size of 3 μm, line width of 210 μm, and gate mesh width of 75 μm, the emission current showed an increase of 165 times and operated for more than 500 h with DC driving. The optimized e-beam can be a building block for vacuum nanoelectronic devices.