M. Takai

Field emission from atomically thin edges of reduced graphene oxide.

Point sources exhibit low threshold electron emission due to local field enhancement at the tip. The development and implementation of tip emitters have been hampered by the need to position them sufficiently apart to achieve field enhancement, limiting the number of emission sites and therefore the overall current. Here we report low threshold field (< 0.1 V/μm) emission of multiple electron beams from atomically thin edges of reduced graphene oxide (rGO). Field emission microscopy measurements show evidence for interference from emission sites that are separated by a few nanometers, suggesting that the emitted electron beams are coherent. On the basis of our high-resolution transmission electron microscopy, infrared spectroscopy, and simulation results, field emission from the rGO edge is attributed to a stable and unique aggregation of oxygen groups in the form of cyclic edge ethers. Such closely spaced electron beams from rGO offer prospects for novel applications and understanding the physics of linear electron sources.

NOVEL CLASS OF LOW MOLECULAR-WEIGHT ORGANIC RESISTS FOR NANOMETER LITHOGRAPHY

A novel class of low molecular‐weight organic resist materials for nanometer lithography, 1,3,5‐tris[4‐(4‐toluenesulfonyloxy)phenyl]benzene (TsOTPB) and 4,4′,4″‐tris(allylsuccinimido) triphenylamine (ASITPA), was designed and synthesized. TsOTPB with a glass‐transition temperature (Tg) of 64 °C and ASITPA with a Tg of 80 °C were found to function as positive and negative resists, respectively, enabling the fabrication of 150 and 70 nm line patterns on exposure to an electron beam at 50 keV.

Effect of substrate absorption on the efficiency of laser patterning of indium tin oxide thin films

Maskless laser patterning of indium tin oxide thin films for flat panel display applications was studied as a function of wavelength using different harmonics of a diode-pumped Q-switched Nd:YLF laser. Electrically isolating lines could be written at all wavelengths used. However, while lines written at the infrared and the visible wavelengths exhibited a ripplelike morphology due to incomplete material removal, ultraviolet laser irradiation produced residue-free etch lines with superior smoothness even at higher scan speeds. The threshold fluences for material removal at different wavelengths were found to correlate with the optical properties of the indium tin oxide film. In addition, numerical simulations of laser-induced temperature rise yielded peak surface temperatures well above the vaporization temperature of the indium tin oxide film, indicating that, at all wavelengths studied, material removal occurs via thermal vaporization. The calculations also revealed that the absorption of the ultraviolet...

Field emission characteristics of screen-printed carbon nano tube after laser irradiation

CNTs (carbon nano tubes) have drawn much attention as a field emitter material because of the high chemical stability, superior mechanical strength, and very high aspect ratio. One can use the well-aligned CNTs produced by CVD method to fabricate the electron emitters, or can also fabricate the electron emitters by a screen-printing method, which is very easy for mass production. In this study, CNTs were screen-printed on the ITO/glass substrate, and were irradiated by an UV (ultra-violet) laser in order to improve the emission behavior of the emitter by cleaning the top surface of screen-printed CNTs or by inducing defect sites, i.e., electron emission sites.

Surface cleaning of metals by pulsed-laser irradiation in air

The surface-cleaning effect of metals was investigated using KrF-excimer-laser irradiation of metal surfaces in air. The laser-induced cleaning of copper, stainless steel and aluminum surfaces was studied. It is found that laser cleaning is an effective cleaning process for metals even if the metal surfaces are heavily contaminated. It is also found that short wavelength and pulse duration are necessary for laser surface-cleaning. The energy density of the laser pulse is an important parameter in the cleaning process. Low energy density results in a cleaner surface but a larger pulse number is required, whereas high energy density can achieve higher cleaning efficiency but the temperature rise can cause surface oxidation and secondary contamination. In contrast to the KrF-excimer-laser, the pulsed CO2 laser is not effective in surface-cleaning. The mechanisms of laser cleaning may include laser photodecomposition, laser ablation and surface vibration due to the impact of the laser pulse. Laser cleaning provides a new dry process to clean different substrate surfaces and can replace the conventional wet cleaning processes such as ultrasonic cleaning with CFC and other organic solvents.

High-speed maskless laser patterning of indium tin oxide thin films

Patterning characteristics of indium tin oxide thin films using different wavelengths of a diode-pumped Q-switched Nd:YLF and a flashlamp-pumped Nd:YAG laser have been studied. While a ripplelike structure in the etched line was formed due to incomplete material removal when the first harmonic of the Nd:YLF or Nd:YAG laser was used, a residue-free line could be obtained using the fourth harmonic of the Nd:YLF laser even at higher scan speeds. The observed differences in the morphology could be attributed to different absorption characteristics at the infrared and ultraviolet wavelengths. High process speeds in excess of 1 m/s could be achieved.

Improvement in electron emission from carbon nanotube cathodes after Ar plasma treatment

Carbon nanotube (CNT) cathode surfaces have been exposed to Ar plasma and the emission characteristics were measured. When a CNT cathode was exposed to Ar plasma for 3 min, the emission characteristics were improved. The emission current increased after an Ar plasma treatment for 3 min by three orders of magnitude from 9.0×10−5 to 3.3×10−1 mA/cm2 at 4.0 V/μm with a decrease in turn-on voltage from 3.3 to 1.7 V/μm. According to scanning electron microscopy images, entangled CNT bundles were raveled out by Ar plasma treatment.

MASKLESS PATTERNING OF INDIUM TIN OXIDE LAYER FOR FLAT PANEL DISPLAYS BY DIODE-PUMPED ND:YLF LASER IRRADIATION

An indium tin oxide (ITO) layer on a lime glass substrate for flat panel displays has been patterned without a mask by scanning Nd:YLF (neodymium‐doped yttrium‐lithium‐fluoride) laser irradiation in a pulsed mode. Both fundamental and frequency doubled lines of 1.047 μm and 523.5 nm were compared for processing. SEM (scanning electron microscopy) and surface stylus observation revealed that only the top ITO layer could be removed without substrate etching. A finer patterning was possible for irradiation of a 523.5 nm line because of the better focusing feature, though higher laser energy density was required for this line than for a 1.047 μm line because of the lower light absorption.

Direct measurement and improvement of local soft error susceptibility in dynamic random access memories

Abstract Soft errors induced in a dynamic random access memory (DRAM) have been measured using a nuclear microprobe. Soft error susceptibility of the local position and structure to the soft error has been clarified. Collection efficiency of charge carriers, induced by incident ions on reverse biased p-n junctions with barrier well structures, has been verified for various implantation doses for well formation.

Well Structure by High-Energy Boron Implantation for Soft-Error Reduction in Dynamic Randam Access Memories (DRAMs)

The susceptibility against soft-errors in dynamic random access memories (DRAMs) has been evaluated using nuclear microprobes by monitoring various addresses of a memory cell array to determine the influence of upper wiring layers such as word lines, bit lines and other patterns. The correlations between irradiated positions of microprobes and monitored cell positions were discussed. The effect of buried implanted layers against carrier collection has also been investigated using ion-beam-induced-current (IBIC) measurement. IBIC measurement revealed that the retrograde well structure was more effective in suppressing soft errors than conventional well structures in bulk or epitaxial substrates.