Kunihiko Nishimura

Emission characteristics of printed carbon nanotube cathodes after laser treatment

Recently, field emission displays using printed carbon nanotubes (CNTs) as an emitter have been researched eagerly. By laser irradiation, some CNTs in the printed CNT layer stand out, and they work as the emission sites. We found that the higher CNTs that are easier to be the emission sites tend to exist at the boundary of the laser irradiation pattern. We used the irradiation patterns that consist of the arrays of microirradiation pattern to increase the total length of boundary. Both emission characteristics and emission uniformity were improved by the increase of the boundary length. We examined several lasers, and the irradiation by the second harmonic generation yttrium aluminum garnet laser of which wavelength was greatest in our experiment provided the best emission characteristics (turn-on electric field <2V∕μm) and emission uniformity (turn-on electric field deviation <5%).

25.2: Fabrication of CNT Electron Source by Simple Stacking for Obtaining Uniform Emission Distributions

We have developed the technique of fabricating triode structure with simple stacking method by forming an extremely smooth CNT layer and by activating CNT with a unique laser irradiation method. A test panel proves good emission property and uniformity.

Fabrication of carbon-nanotube field-emitter array using polymer insulator

This article reports the fabrication process of a carbon-nanotube (CNT) field-emitter array with the silicon-ladder polymer insulator polyphenylsilsesquioxane (PPSQ), whose feature is heat resistance, high breakdown voltage, and low outgassing. CNT islands are formed with a screen-printing method, polymer-insulator coating is carried out (8 μm in thickness), and the gate electrodes are deposited, followed by patterning of the electrodes. PPSQ insulator is applied reactive ion etching (RIE) to reveal CNT emitters. Because of using mixed gases of CF4 and O2, the etching rate for CNT is half that for PPSQ, there is a margin to stop etching with enough CNT left. After reactive ion etching, emission-current density from the revealed CNT is degraded, so laser activation treatment is applied and the emission current density is boosted by a hundredfold. In the case of the triode mode, the laser condition was chosen to prevent gate damage and to improve emission characteristics. Current density of 3 mA/cm2 is obta...

Improvement of emission characteristics uniformity of carbon nanotube field emission display by surface treatment

Carbon nanotubes (CNTs) have been investigated as an emitter for field emission display (FED). In our FED fabrication process, the printed CNTs are raised by a laser irradiation for the purpose to improve the emission characteristics. Because the emitters have to be controlled in each pixel individually on FED, the uniformity of the emission characteristics is necessary. We could improve the emission characteristics uniformity successfully by two methods. In the first method, the distribution of CNT raisings was homogenized by the modification of the irradiation pattern that consisted of an array of small areas. The emission deviation was improved to approximately half by the method. In the second method, the impurities of CNT raisings were cleaned by post-laser-irradiation of which fluence was lower than that of first irradiation. The emission characteristics improved and the turn-on electric field reduced from 2.1 to 1.4V∕μm. The emission deviation also improved to approximately half.

53.1: Fabrication of CNT Emitter Array with Polymer Insulator

A new method of fabricating CNT emitter array using polymer insulator with low outgassing has been developed. A dry etching process without the damage on the CNT has been found and it proved to decrease the turn-on voltage. Better emission properties than conventional insulator has been obtained.

Analysis of short circuit current loss in rear emitter crystalline Si solar cell

Short circuit current (Jsc) loss in rear emitter crystalline Si solar cell is analyzed in detail by a 2D device simulation and compared with the experimental results. There is a significant loss in Jsc for the rear emitter n-Si solar cell with an n-type doped front surface field (FSF) when the base substrate resistivity is low. It is due to an increase in recombination in the FSF region led by a less barrier height for minority carriers with a lower substrate resistivity. The barrier height less than 0.1 eV causes large loss in Jsc. To achieve higher Jsc for the cells with FSF, the control of the doping concentration in FSF, the substrate thickness, and the barrier height for the minority carriers are important. A rear emitter heterojunction Si solar cell with an amorphous Si passivation layer shows no substrate resistivity dependence on Jsc since an amorphous Si possess a higher barrier height and a long bulk lifetime of more than a few milliseconds.

Over 21% Efficiency of n-Type Monocrystalline Silicon PERT Photovoltaic Cell With Boron Emitter

We have developed an n-type monocrystalline silicon photovoltaic cell achieving the conversion efficiency of 21.3% by passivated emitter and rear totally diffused structure with a total area of 239 cm2. The center area of the cell showed 21.7% (226.3 cm2). The main developments for the cell related to an emitter are a boron diffusion process and a passivation process of the boron layer. The developed cells contain a deeply diffused and lightly doped boron emitter with a high-quality surface passivation layer to obtain high efficiency. An atmospheric pressure chemical vapor deposition (APCVD) process is used for the fabrication of a boron emitter. This process is suitable for mass production lines. An atomic layer deposition Al2O3 layer is applied for a passivation of the boron layer. In addition, the ohmic contacts between the cell and electrodes are improved by changing a temperature profile for an electrode firing process.

Fabrication of CNT field‐emitter array using a polymer insulator

— The fabrication process of a carbon-nanotube (CNT) field-emitter array (FEA) having a polymer insulator is reported. This polymer material is suitable for a large-sized FEA because of its coating property and thermal stability. These features contribute to the display-image uniformity, the tolerance to the thermal-sealing process, etc. A new method of forming via holes on the insulator instead of gate holes has been developed. The method uses a spin-wet-etching (SWE) technique instead of the typical reactive-ion-etching (RIE) method. The RIE method damages and contaminates the CNT at the end of the etching process. However, the SWE technique ensures fine gate hole configurations with little under-cut without any damage nor contamination. An FEA panel 1.5 in. on the diagonal was fabricated by using the method. The FEA showed good emission uniformity with proper surface treatment of the CNT.

3D image technique with a grating plate on high-resolution CRT

We propose the 3D image technique using a CRT with a grating plate. The main component of the system is a CRT, a lens and a diffraction plate. We make a composite image on the CRT. The composite image is compounded from several images taken from different view points. This image is focused on the diffraction plate through the lens. There are many pixels of the diffraction gratings that correspond to the pixels of the composite image. Each image is diffracted to different viewing areas by the diffraction gratings. Because we can see one image from each viewing area independently, we can observe 3D image. We made a test system. The size of composite image on the CRT screen is 8-inch. The composite image is compounded from four images. The size of the diffraction grating plate is 3-inch. The width and height of one viewing area is 6 cm by 6 cm and total viewing area is 24 cm by 6 cm. The system is able to divide the composite image into four images and we can observe the images that have perspective.