Yong Sik Lim

Investigation of the transition between glow and streamer discharges in atmospheric air

Generally, the parameter p ? d (pressure ? gap distance) in dielectric barrier discharge (DBD) controls the electrical breakdown and also the plasma characteristics. We investigated the optimum plasma transition p ? d by controlling the pressure. To find the transition p ? d (p ? dtr) condition, optical emission spectroscopy (OES) was used to measure emission spectra from the DBD. All p ? d data were normalized by the second positive system of nitrogen molecules, the wavelength of which was 337.1?nm. Then we compared the relative intensities of species generated during the discharge by OES analysis. Species selected for comparison were the first negative system (FNS) of nitrogen molecules (391.4?nm) and atomic oxygen spectra (777.1?nm). Experimental results showed that relative intensities were almost constant as p ? d decreased, but at specific p ? d data, the intensity started to increase. The increase in FNS of nitrogen molecules means not only an increase in electron energy but also a change in the plasma mode, streamer to glow transition. In the case of DBD using alumina with 1?mm thickness applied ac power, the plasma transition occurred at the 1?Torr?cm condition.

Work function increase of indium-tin-oxide surfaces by atmospheric air plasma treatment with steady-state airflow

Atmospheric air-plasma treatment of indium–tin–oxide (ITO) surfaces has been investigated as an alternative to a conventional oxygen (O2) vacuum plasma process. For this study, we devised an atmospheric air barrier plasma system having a dimension of 1000×600mm2 and successfully verified a possibility to ignite and maintain an atmospheric pressure discharge only in the ambient air. In particular, we used the steady-state airflow to generate more atomic oxygen radicals as oxygen gas during the vacuum plasma process and to prevent redeposition of the removed or transformed impurities onto the indium–tin–oxide substrate. The x-ray photoemission spectroscopy examination indicated that the adoption of the atmospheric-air plasma treatment reduced the surface content of carbon from 22.1% down to 8.5% and increased that of oxygen from 43% up to 57%. According to the photoelectron spectrometer (AC-1, RIKKEN) result, we obtained a work function of 5.11eV for the treated ITO surfaces after 1min treatment time, which...

Improvement of plasma uniformity using ZnO-coated dielectric barrier discharge in open air

The discharge behavior in atmospheric pressure dielectric barrier discharge using ZnO-coated dielectric layer is examined. ZnO thin film on alumina using rf magnetron sputter causes about a factor of a million higher surface conductivity than bare alumina surface. Experimental result shows that discharge uniformity is improved definitely in the case of ZnO-coated dielectric barrier discharge. Increase of surface conductivity stimulates charges to spread over the dielectric surface widely. These charge spreading enhances the uniformity and the stability of atmospheric pressure discharge in open air by initiation of consecutive streamers.

Analysis of polymer surface treated by dielectric barrier discharge

We investigate polymer surfaces after exposing them to dielectric barrier discharges with different flowing gases (He, CF4) in air. The relationship between the gas characteristics and the surface properties of polypropylene (PP) is determined by contact angle measurement, optical emission spectroscopy and x-ray photoelectron spectroscopy. Experimental results reveal that there is a definite relationship between the surface energy and the surface chemical composition of PP and also indicate that the hydrophilicity of PP in an atmospheric pressure (AP) discharge is more dependent on ionic bombardment than on the atomic oxygen composition at the surface and its hydrophobicity depends on the fluorine composition at the PP surface. In addition, it turns out that in a CF4 discharge at AP, the CF3 molecular band exhibits a continuum band at the orange line in the visible range.

Control of current-jump induced by voltage, temperature, light in p-type GaAs: Programmable critical temperature sensor

For two-terminal devices fabricated by Be (or Mn)-doped p-type epitaxial GaAs thin films, when the Mott metal-insulator transition (MIT) as current jump occurs, we observe that the energy gap of GaAs is not shifted, its peak intensity decreases in an applied voltage, and that the MIT temperature is between 410 and 440 K, and that the current jump is controlled by temperature, voltage and light intensity. The control of the jump voltage, a characteristic of the Mott MIT, reveals that these devices can be applied for programmable critical temperature sensors or optical sensors with high sensitivity.

Large area silicon dioxide deposition using rf atmospheric pressure glow discharge at low termperature

Summary form only given. RF APGD (atmospheric pressure glow discharge) is nonequilibrium plasma and low temperature plasma. This plasma source is of interest for the deposition of materials because low temperature deposition without a vacuum system is possible. Moreover, remote plasma deposition process using atmospheric pressure plasma jet has some advantages due to suppression of ion bombardment effect. Silicon dioxide films were deposited using an atmospheric pressure plasma jet composed of two planar electrodes with an area of 50 mm times 30 mm at a distance of 1 mm. The planar jet was operated with helium of 20 slm, O2 of 400 sccm and RF (13.56 MHz) power of 60-100 W was applied. He-TEOS mixture (99% He, 1% TEOS) was injected into the plasma region directly. The films were deposited on silicon substrates with heating 100-300 Z. We investigated the deposition rate at various conditions by controlling power, oxygen pressure and TEOS pressure, substrate temperature. And we analyzed the film properties with former variables by SEM, FTIR, AFM and hardness test. Finally, large area SiO2 deposition was accomplished uniformly by only one directional scan system since the plate jet has linear shape

Distinction Between Streamer to Glow Transition in Atmospheric Discharge using Optical Emission Spectroscopy

Summary form only given. Generally to generate glow discharge in air, sufficient numbers of seed electrons or metastables are needed. But by electronegative gases such as oxygen and water vapor etc, atmospheric discharge exists as streamer, non-uniform microdischarges. As mentioned by other references, the parameter Ptimesd in dielectric barrier discharge (DBD) controls electrical breakdown. At high gas pressure, two types of breakdown mechanisms can occur. One is called Townsend breakdown at low Ptimesd and the other breakdown is termed streamer breakdown at high Ptimesd. Therefore, we investigated optimum streamer-to-glow transition Ptimesd by controlling pressure. And to find transition Ptimesd condition, we compared the relative intensities of generated species at each discharge mode during discharge by optical emission spectroscopy analysis. Experimental results show that in case of DBD using alumina with 1 mm thickness streamer-to-glow transition occurred at the 1 torrmiddotcm condition.