Young-Guon Kim

Measurement of Secondary Electron Emission Coefficient (γ) of MgO Protective Layer with Various Crystallinities

The secondary electron emission coefficient γ of a MgO protective layer with various crystallinities has been successfully measured by the γ-focused ion beam system with complete elimination of the charge accumulation problem by scanning-area adjustment techniques. It is found that the (111) surface has the highest γ from 0.14 to 0.26 in comparison with the other films with (200) and (220) crystallinities for operating Ne+ ions, while ranged from 0.03 to 0.24 for Ar+ ions, under operating ion energies from 50 eV to 500 eV throughout this experiment. These observations explain why the (111) crystallinity of the MgO protective layer plays an important role in lowering the firing voltages in AC plasma display panel compared to the films with other crystallinities.

Secondary electron emission coefficient of a MgO single crystal

The secondary electron emission coefficient γ of different MgO single crystal has been measured by γ-focused ion beam system. It is found that the MgO single crystal with (111) orientation has the highest γ from 0.08 up to 0.21, while from 0.06 to 0.19 for (200) and from 0.05 to 0.15 for (220) orientation for operating Ne+ ions ranging from 50 to 300 eV throughout this experiment. It is also found that these observations can be explained by work functions, which are dependent on the crystal orientations of MgO.

Striations in a coplanar ac-plasma display panel

Striations observed in a coplanar or a wedge-shaped planar ac-type discharges are reported in this article. The observed data indicate that the striations are related to ion charge waves of the wall generated by the self-sustained perturbations that originate from the force balance between the ion and the electron wall-charge clouds accumulated on the dielectric layers over the metal electrodes.

Ion-Induced Secondary Electron Emission Coefficient(γ)of Bulk-MgO Single Crystals

The ion induced secondary electron emission coefficient ? of bulk-MgO single crystal has been measured by the ?-focused ion beam system. It is found that the bulk-MgO single crystal with (111) orientation has the highest ? from 0.08 up to 0.21, and the ? values are in the order of the crystallinities, (111) > (200) > (220) for operating Ne+ ions ranging from 50 eV to 300 eV in this experiment. These results are consistent with our previous reports for MgO protective layers with respective orientations of (111), (200), and (220).

Influence of Driving Frequency on the System Parameters in Surface Discharge of AC Plasma Display Panels

The influence of the driving frequency on the wall charge and voltage is experimentally investigated for the surface discharge of AC plasma display panels. A square pulse with a rising time of 150 ns and a duty ratio of 40% was used in the experiment. It is found that the capacitance C0 of the surface discharge in a gas-filled region is almost constant and is 0.3 pF/cell, whereas the capacitance Cg in the dielectric region is significantly decreased from 7.5 pF/cell to 0.8 pF/cell, as the driving frequency is increased from 10 kHz to 200 kHz. It is also found that both the wall charge and the wall voltage decrease from 34.5 pC/cell to 15.6 pC/cell and from 104.4 V to 76.5 V, respectively, as the driving frequency increases from 10 kHz to 200 kHz.

Computer-controlled fabrication of ultra-sharp tungsten tips

In order to monitor the end-point current during electrochemical etching, an analog to digital converter circuit aided by a personal computer has been setup. At the moment the lower part of the needle drops off during the etching process, a maximum current change across the reference resistor is detected by the PC interface card and the applied voltage is then cut off within a few milliseconds. Using these circuits to control the etching time, our experiment has been able to fabricate an ultra-sharp tip of ∼200 A radius with a higher reproduction rate and reliability than the conventional method.

P-36: LCD Planar Backlight Employing the External Electrode Fluorescent Lamps Driven by Square Pulses from Switching Inverter

The planar luminaries with the external electrode fluorescent lamps arrayed on a flat panel for the LCD-backlight have been improved by driving with the square pulses from a single switching inverter. With the square pulses of the driving frequency about 30 kHz, the high efficiency up to 40–70 lm/W and high brightness up to 30,000 cd/m2 along with the luminance uniformity 90% in the 15-inch, 18-inch, 21-inch diagonal panels, respectively, could be obtained.

Temperature effects on the energy spreads in liquid metal ion sources

The energy spread of charged particles during beam propagation is calculated for liquid-metal ion sources. After acceleration, the particles have different energies originating from Coulomb interactions among them, which are randomly located due to the statistical fluctuations caused by the emission-surface temperature. The energy spreads are obtained in terms of the total current and emitter temperature. In particular, the energy spread is proportional to the square root of the emission-surface temperature. The results agree remarkably well with previously reported experimental data for the liquid-gallium ion beam.

Effects of the Dielectric Layer on a Planar and a Coplanar Discharge Breakdown

There are two influences of a dielectric layer on the breakdown in Paschens law. The potential difference at the dielectric layer itself enhances the minimum value of firing voltage, while the strong field in the discharge space with a large dielectric constant reduces the firing voltage in a high pressure range. Specially in a coplanar geometry like AC-PDP [S. Sato et al. : IEEE Trans. Electron Devices 23 (1976) 328.], the firing voltage is shown to be higher due to the non-uniformity of the electric field along with the thickness of the dielectric layer.

Influence of Vacuum-Annealing Process on the Secondary Electron Emission Coefficient (γ) from a MgO Protective Layer

The secondary electron emission coefficient (γ) of vacuum-annealed MgO films has been investigated using a γ-focused ion beam (γ-FIB) system. The vacuum-annealed MgO films have been found to have higher γ values from 0.05 to 0.12 than those from 0.03 to 0.06 for as-deposited MgO films for operating Ne+ ions whose acceleration voltages ranged from 50 V to 200 V. It is shown that the γ for the as-deposited MgO protective layer is significantly decreased by the influence of holding in air since the hydroxyl OH groups are absorbed onto the MgO surface from the atmospheric air. It is also observed that the secondary electron emission coefficient γ for the vacuum-annealed MgO protective layer is less influenced by holding in air than that for the as-deposited MgO protective layer. Based on these findings, it is concluded that the vacuum-annealed MgO protective layer plays an important role in lowering the firing voltage in alternating current-plasma display panel (AC-PDP) compared with the as-deposited MgO protective layer or the as-deposited MgO protective layer held in air.