Seong Eui Lee

Material properties and plasma display panel discharging characteristics depending on MgO evaporation rate

MgO thin film is most widely used as a protecting layer in ac Plasma Display Panel. The film is deposited using electron beam evaporation. The effects of the evaporation rate of MgO film deposited using an electron beam on the MgO properties and the discharge characteristics of the plasma display panel (PDP) were investigated. The evaporation rate was changed from 3 to 15 A/s at a substrate temperature of 300 °C. MgO properties such as crystal orientation, surface roughness, contact angle, and film structure were inspected using X-ray diffraction (XRD), analysis atomic force microscopy (AFM), drop shape analysis, and secondary electron microscopy (SEM). The MgO properties were shown to be strongly dependent on the evaporation rate. We also studied the relation between MgO properties and PDP discharging characteristics. The minimum firing voltage and maximum luminous efficiency were obtained at an evaporation rate of 5 A/s. In the MgO film deposited at 5 A/s, the (200) orientation was most intensive and surface roughness was minimum.

Use of zeolites in the capture of charged particles from plasma

The zeolites NaA and 13X were introduced to a coplanar discharge cell to investigate the behavior of charged particles from plasma. The zeolite crystals were attached to the surface without blocking their nanopores. The memory margin related to the accumulated charged particles on the surface indicated that the zeolites absorb charged particles. This phenomenon was also observed at the displacement and discharge current plots. Zeolites with a different window size cause abnormally high displacement and a saturation phenomenon of discharge currents. Note in particular that NaA seems to not only absorb charged particles but also capture gas molecules.

The Effectof Li-Ion-Doped Porous MgO Film on Operational Memory Margin of ac-Plasma Display Panel

An ac-type plasma display panel (ac-PDP) made with Li-ion-doped MgO film formed using a sol–gel precursor is characterized and compared with an ac-type PDP with an MgO film formed by e-beam evaporation. The operational memory margin of a test panel with a pure MgO film formed using the printing method is very high due to the porous surface of the films. For a test panel with Li-ion-doped MgO, the operational margin decreases as the dopant concentration increases. The secondary electron emission from a pure printed MgO film is highly unstable because of the severe surface charging due to the porosity of the MgO films. The surface charging decreases linearly as the dopant concentration increases. This secondary electron emission (SEE) result implies that a linear relationship exists between the memory margin of an ac-PDP and the charging phenomenon of the MgO surface after the SEE.

Fabrication and Characterization of Rapidly Oxidized p-Type Cu2O Films from Cu Films and their Application to Heterojunction Thin-Film Solar Cells

In this study, we report that the metal Cu deposited on a glass substrate is formed into a stable p-type Cu2O film with excellent properties through rapid thermal oxidation (RTO). The pre-deposited Cu film layer went through thermal oxidation in the temperature range of 200–500 °C in O2 and air ambient, and the electrical and optical properties were intensively investigated. The optimized p-type Cu2O film heat-treated at a temperature of 200 °C in an air ambient has a carrier concentration of 1.25×1017 cm-3, mobility of 0.51 cm2 V-1 s-1, and resistivity of 9.86 Ω cm; its optical band gap reaches about 2.4 eV. Using the p-type Cu2O film with i- and n-type amorphous silicon layers, heterojunction thin-film solar cells were fabricated on glass substrates. These transparent solar cells employed Ga-doped ZnO films as top and bottom electrodes. Solar cells with Cu2O film oxidized at 200 °C in an air ambient have an open circuit voltage of 0.36 V, short-circuit current of 15.2 mA/cm2, and photoelectric conversion efficiency of 1.98%.

Injection of carriers from a ZnO nanostructured shell to a ZnS based microsphere core

ZnO nanostructures were synthesized on a microsphere ZnS:Cu,Cl (ZC) with various optical emission bands. Using an electroluminescence (EL) device with a semiliquid type of active layer, the carrier injection phenomenon through the nanostructure was observed. The EL from ZnO nanorods on the cubic ZC and the ZnO plate on the hexagonal ZC showed a nonlinear voltage-color characteristic and deep blue color, respectively, as explained by the carrier injection through the ZnO nanostructures. Both carrier injection cases appear to have been caused by the lowered band-gap energy at the boundary and by the structural factors that focused the applied electric field.

High-Luminous-Efficiency AC-Plasma Display Panel Using Separate Discharge Mode in Tiled Sustain Electrode Structure

The discharge characteristics of high-efficiency AC-plasma display panels (PDPs) using a separate discharge mode were investigated using both numerical simulation and experiments. New types of segmented sustain electrodes have been proposed in order to increase the luminous efficiency with low power consumption and without major changes in the manufacturing process. We have obtained the higher efficiency with a wider separation between the left-side and right-side discharges in a cell. This effect can be explained in that a wider gap between the tiles is beneficial because the discharge remains confined to the walls, thus efficiently exploiting the phosphor on the walls. The discharge images of an intensified charge-coupled device (ICCD) camera in a tiled sustain electrode structure support these results.

Fabrication of nano-structures on glass substrate by modified nano-imprint patterning with a plasma-induced surface-oxidized Cr mask

In this study, we introduce a process for fabrication of nano-sized structural arrays on glass using modified nano-imprint patterning. A PVC (polyvinyl chloride) stamp was prepared by hot embossing, and a Cr-oxide-pattern etch-mask was used. The etch-mask was formed by oxidizing the surface of exposed Cr region by oxygen plasma treatment at room temperature. The fabrication of the etch-mask was conducted by immersing the locally oxidized Cr pattern in resin remover and Cr-etchant. The residual UV resin and un-oxidized Cr pattern were selectively removed, resulting in the obvious array of Cr-oxide etch-mask-pattern. The array of glass nano-structures was formed by reactive ion etching (RIE) using CF4 and Ar gas discharge. After removing the Cr-oxide mask, the final nano-structure had a height of 40 nm and a diameter of 170 nm, which was slightly less than the diameter of the original master-mold. The plasma treatment gave rise to a rough glass surface with root-mean-square (RMS) roughness of 29.25 nm, while that of bare glass was 0.66 nm. A high optical transmittance due to reduction in reflectance was observed at the plasma-treated rough surface, as well as for the array of nano-structures. The highest measured optical transmittance was 97.2% at a wavelength of 550 nm; an increase of about 7.2% compared to bare glass.

A Study on the Crystalline Orientation and Electromechanical Properties of PZT and Doped PZT Thin Films by Using the Sol-Gel Method

This study investigated the crystalline orientation and electromechanical characteristics of PZT films fabricated with various concentrations of sol-gel solution, and dopants such as Nb and Zn. Crack-free and 1-μm-thick films with a pure perovskite phase were obtained on Pt/Ti/SiO2/Si by modified sol-gel deposition method. The degree of (111) orientation was promoted by a higher concentration of a sol-gel solution. Excellent electromechanical characteristics were measured in PZN-PZT films. The highest remnant polarization and d33 piezoelectric coefficient were 25.1 μC/cm2 and 240 pC/N, respectively. The sol-gel driven PZN-PZT films could be attractive for application to piezoelectrically operated microelectronic devices.

The Discharging Characteristics of Spin-Coated MgO Thin Films with Li Dopant in a Flat Fluorescent Lamp Structure

The physical and electronic properties of lithium ion doped MgO films formed by spin coating were investigated and characterized in a flat fluorescent lamp structure. The doped MgO films were exquisitely crystallized until the doping concentration was increased to 5%. The test panel with Li-doped MgO films showed that the initial discharge voltages were decreased with increasing the dopant concentration. In particular, the static memory margin of the test panel showed the higher value than that of pure-MgO film. The CL spectra confirmed the creation of defects energy levels in the energy band gap of MgO and showed that the main defects in the doped MgO were the F+ center increased as the concentration of lithium ion was increased.

The Effect of Potassium-Doped MgO Films on Discharge Characteristics in AC-Plasma Display Panel

In this paper, we investigate how various concentrations of potassium-doped MgO films affect the discharge characteristics in ac-type plasma display panel. The firing voltages of ion-doped MgO films indicate that the potassium ions in MgO film clearly produce a low discharge voltage. The static memory margin of a test panel decreases as the concentration of potassium ions increases. The X-ray photoelectron spectroscopy results, which confirm that the potassium doping creates donor energy levels in the band gap of MgO, agree well with the varied behavior of secondary electron emission yields in various K+-doped MgO films.