Alternating-current Plasma Research Articles

Oxidative Treatment and Characterization of Plasma Carbon Blacks

A series of carbon blacks and fullerene soot was produced by a 3-phase Alternative Current (AC) plasma technology. Surface properties of parent materials and their oxidized homologues were studied by Fourier transform infra red spectroscopy (FT-IR), pH of the point zero charge (pHPZC) and acid/base titration. Presence of chemically bounded oxygen and hydrogen in the parent materials was attributed to the ageing of the materials, while the considerable differences observed in the material reactivity toward nitric acid were associated with properties of nanostructure, governed by conditions of plasma synthesis method. The most stable materials are the carbon blacks having the highly ordered graphitic structure, prepared in thermal plasma process by hydrocarbons cracking. These materials present a low surface reactivity. On the other hand, the fullerene soot, obtained in helium atmosphere from pure carbon, exhibits a very high surface reactivity, induced by structure desorganization and probably the presence of dangling bonds.

Improvement in Discharge Delay Time by Accumulating Positive Wall Charges on Cathode MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

The improvement in discharge delay time by accumulating positive wall charges on a cathode MgO protective layer surface in plasma display panels (PDPs) was investigated. The number of exoelectrons emitted from the cathode MgO surface, which trigger the discharge, increases with the accumulation of positive wall charges on the cathode MgO surface, thereby reducing both the statistical and formative delay times, ts and tf, respectively, of the address discharge. The correlations between exoelectron emission and ts and tf were investigated, revealing that the address discharge is triggered by multiple exoelectrons. In addition, it is found that exoelectron emission plays an important role in wall charge leakage during the address period. The present results confirmed that the accumulation of positive wall charges on the cathode MgO protective layer surface is effective for improving the discharge delay times ts and tf in not only PDPs but also common dielectric barrier discharge.

Improvement in Discharge Delay Time by Accumulating Positive Wall Charges on Cathode MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

Improvement in Discharge Delay Time by Accumulating Positive Wall Charges on Cathode MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

Accumulation and Decay Characteristics of Exoelectron Sources at MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

The accumulation and decay characteristics of exoelectron sources at a MgO protective layer surface in alternating-current plasma display panels (AC-PDPs) were investigated. The positively charged MgO surface provides a larger number of exoelectrons than the negatively charged surface, indicating that electrons trapped in shallow carrier traps coexist with trapped holes, and exoelectrons are emitted through Auger and/or photoionization processes after their recombination. The exoelectron sources are accumulated by sustain discharges and always decay. The half-life of the decay of the exoelectron sources is relatively long, of the order of a few tens of ms, confirming that the exoelectron emission property at the address discharge in a certain television (TV) field is strongly affected by sustain firings in the previous two TV fields or more. The effects of such a long-term decay of the exoelectron sources should be taken into consideration when designing the driving waveforms of AC-PDPs.

Laser direct patterning of the T-shaped ITO electrode for high-efficiency alternative current plasma display panels

The laser direct patterning technique is one of the new methods of direct etching process to replace the conventional photolithography. In this experiment, a Q-switched diode-pumped Nd:YVO 4 ( λ = 1064 nm) laser was used to produce the indium–tin oxide (ITO) patterns with a complex T-shaped structure on glass substrate. The results showed that the overlapping rate of laser beam had a major effect on the quality of the edge of the ITO electrode. When the overlapping rate was about 75%, it was possible to obtain optimum linearity in the edge of patterned ITO electrode. By using the optimum conditions of 75% overlapping rate, 500 mm/s scanning speed, and 40 kHz repetition rate, an alternative current plasma display panels (AC PDPs) with T-shaped ITO electrode was fabricated and characterized. The discharging results showed that the AC PDPs with the laser ablated T-shaped ITO electrode had a better discharging characteristics compared to the conventional sample with wet-etched stripe-type ITO electrode.

Performance Enhancement by Using Graphite-In-Diamond Nanoparticles on MgO Protective Film in AC Plasma Display

Graphite-in-diamond (GiD) nanoparticles in which the secondary-electron-emission coefficient was larger than the MgO protective film were introduced to enhance the electrical and optical characteristics in alternating-current plasma displays. The GiD nanoparticles suspended stably in ethanol solvent were sprayed uniformly on an MgO film. Based on the results of field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy analysis after continuous operation for approximately 300 h, the morphology of the GiD nanoparticles as well as the carbon element in the particles was preserved nicely, and their characteristics could ensure long lifetime without degradation in plasma environment. It is noted that the average firing voltages of the GiD panels are 135 and 80 V lower than those of the conventional one for gas mixtures of Ne + He (50%) + Xe (15%) and Ne + He (50%) + Xe (30%), respectively. It was revealed that the optimum coverage ratio of the GiD nanoparticles sprayed on the MgO film was 6%. The luminous efficiency of the GiD panel was improved up to 40% for relatively higher xenon contents.

Effects of Wall Charge on Firing Voltage and Statistical Delay Time in Alternating-Current Plasma Display Panels

The effects of wall charge on firing voltage, Vf, and the statistical delay time of discharge, ts, in plasma display panels were investigated. Vf, i.e., the ion-induced secondary electron emission, is independent of both the polarity and amount of wall charge. In contrast, ts, i.e., the exoelectron emission, strongly depends on the wall charge and is smaller for a high positive wall charge, revealing the coexistence of trapped electrons and holes in the surface region. Positive charging of the MgO surface of the cathode side is effective to improve the response of the address discharge.

Analysis of transient electron energy in a micro dielectric barrier discharge for a high performance plasma display panel

We present here analysis of electron energy of a micro dielectric barrier discharge (micro-DBD) for alternating-current plasma display panel (ac-PDP) with Ne/Xe gas mixture by using the optical emission spectroscopy (OES). The OES method is quite useful to evaluate a variety of electron energy in a high pressure DBD ignited in a PDP small cell. Experiment shows that the ratio of Ne emission intensity (INe) relative to Xe emission intensity (IXe) drastically decreases with time. This temporal profile is well consistent with dynamic behavior of electron temperature in a micro-DBD, calculated in one-dimensional fluid model. INe/IXe also decreases with an increase in Xe gas pressure and a decrease in applied voltage especially in the initial stage of discharge, and these reflect the basic features of electron temperature in a micro-DBD. The influences of plasma parameters such as electron temperature on luminous efficacy are also theoretically analyzed using one-dimensional fluid model. The low electron temperature, which is attained at high Xe gas pressure, realizes the efficient Xe excitation for vacuum ultraviolet radiation. The high Xe-pressure condition also induces the rapid growth of discharge and consequent high plasma density, resulting in high electron heating efficiency.

Study on Pulse Waveforms for Improving Voltage Margin and Luminous Efficacy in an AC Plasma Display Panel Having Auxiliary Electrodes

New pulse waveforms applied to an alternating-current plasma display panel (ac PDP) with an auxiliary electrode are investigated for the purpose of improving the panel's operating voltage margin and luminous efficacy. In the proposed pulse waveforms with reciprocal sustain pulses, a pair of positive and negative sustain pulses is applied to the sustain electrodes simultaneously and alternately. A positive auxiliary pulse is applied to the auxiliary electrode immediately after reciprocal sustain pulses. The voltage margin becomes wider, and the luminous efficacy is improved because of the suppression of the discharge toward the address electrode. In the another proposed pulse waveforms with reciprocal sustain and auxiliary pulses, a negative pulse, which is the same as the negative pulse of reciprocal sustain pulses, is additionally applied to the auxiliary electrode when reciprocal sustain pulses are applied. This negative auxiliary pulse can maintain a high level of luminous efficacy because it supports the effect of the auxiliary pulses. The measurement results show that the operating voltage margin is about twice wider than that of the typical pulse waveforms for an ac PDP with an auxiliary electrode; furthermore, the maximum luminous efficacy is able to reach 3.14 lm/W in terms of the measurement of the discharge in a 50-in XGA resolution (0.27 mm × 0.81 mm) panel with a white cell and a gas mixture of Ne+20%Xe.

Optimization of Sustain Electrode Gap for High-Efficiency Plasma Display by Using a Counter-Electrode Structure

A counter-electrode structure as a microscaled dielectric barrier discharge for an application to the alternating-current plasma display has been investigated with six in-test panels fabricated by using a thick-film ceramic-sheet method. Based on observations of infrared (IR) emission, the optimum sustain electrode gap to generate an efficient positive-column-like microdischarge plasma was suggested. The IR emission as well as the firing and sustain voltages increases with the increasing electrode gap, and the positive-column-like microdischarge plasma was built up for electrode gaps over 400 mum, which can be used for an intense vacuum ultraviolet source. Furthermore, the luminance and luminous efficiency, as well as the panel capacitance of the counter-electrode structure, were compared with those of the conventional reference structure.

The Effects of Electrode Structures on the Luminous Efficacy of Micro Dielectric Barrier Discharges

A high-efficacy alternating-current plasma display panel utilizing various electrode structures is simulated using a 3-D fluid code for the investigation of the effects of cell structures on the discharge characteristics of micro dielectric barrier discharges. For the modification of the conventional coplanar electrode structure, three suggested electrode structures were simulated, namely, a patterned bus electrode, a multilayer bus electrode, and a two-electrode facial discharge structure. The time evolutions of infrared radiation images for the three structures compare well with the experimental results of test panels. The ultraviolet and visible-light emission profiles, as well as the time evolution of wall charge profiles, are analyzed in order to explain the role of the electrode structure for the improvement of luminous efficacy.

A new laser direct etching method of indium tin oxide electrode for application to alternative current plasma display panel

For cost effective fabrication and time of alternative current plasma display panels (AC PDPs), an indium tin oxide (ITO) layer was patterned directly with a Q-switched diode pumped Nd:YVO 4 laser ( λ = 1064 nm). As experimental results, 500 mm/s scan speed with 40 kHz repetition rate was suitable for the application to AC PDP ITO electrode. In comparison with the chemically wet-etched ITO patterns by photolithography method, laser-ablated ITO patterns showed the formation of shoulders at the edge of the ITO lines and a ripple-like structure of the etched bottom. By dipping the laser-ablated ITO films in the chemical etching solution for 30 s at 50 °C, the shoulders were effectively removed without affecting the discharging properties of AC PDP.

The Analysis of Memory Margin of an Alternative Current-Plasma Display Panel with K-Ion-Doped MgO

An ac-type plasma display panel (ac-PDP) with K ion-doped MgO film formed via a sol-gel precursor was analyzed and compared to an ac-type PDP with MgO formed by e-beam evaporation. As the dopant content was increased, memory margins of test panels were linearly reduced and the surface charging caused by the secondary electron emission (SEE) was decreased. From these results we suggested the amounts of surface charging has a close relation to the wall potential of ac-PDP.

The effect of Fe-doped magnesium oxide thin film in alternative current plasma display panel

In order to improve the discharge characteristics of MgO thin film as a protective layer in an alternative current plasma display panel, Fe-doped MgO thin films was introduced. Both the surface characteristics of the deposited thin films and the electro-optical properties of 4 inch test panels were investigated. It has been demonstrated experimentally that ac PDP with Fe-doped MgO protective layer has lower discharge voltage than that of undoped MgO film, which corresponds to measured secondary electron emission coefficients. The crystallinity and surface roughness of thin films were determined by XRD patterns and AFM images.

A study on the secondary electron emission from Na-ion-doped MgO films in relation to the discharge characteristics of plasma display panels

Using a sol–gel precursor, Na-ion-doped MgO was prepared and applied to alternative current plasma display panels (ac-PDP). The cathodoluminescence spectra showed that the F + center was increased as the concentration of Na + was increased. Numerous pores were found on the printed MgO surface and seemed to give higher memory margin of ac-PDP compared to an electron beam-evaporated MgO film. All doped MgO showed higher secondary electron emission than printed pure MgO, likely owing to the O defect states of MgO. In addition, this result indicated the operational memory margin of the ac-PDP was directly proportional to the grade of surface charging.

Spatio-Temporal Effect of Gas Pressure on Excited Xe Atoms in Ultrafine Pixel Pitch AC Plasma Display Panels

The kaleidoscopic change in the distributions of excited xenon (Xe) atom density was investigated under a high gas pressure condition in a unit microdischarge cell on a coplanar-structured alternating-current plasma display panel with an ultrafine pixel pitch by using microscopic laser absorption spectroscopy. As the gas pressure increased, the peak densities of the excited atoms not only increased but the peak position on the anode side also tended to shift toward the center of the discharge gap by expanding in width. The temporal behavior of the excited Xe atom density in the resonant state (1s4) did not change significantly with the pressure since the decay rate was mostly governed by the effective lifetime of the imprisoned resonance radiation. On the contrary, the decay rate of the excited Xe atoms in the metastable state (1s5) decreased drastically with the pressure due to an increase in the three-body collision rate. This implied that the metastable state atoms were efficiently converted to Xe excimers, leading to an increase in the vacuum ultraviolet emission.

Spatiotemporal Behavior of Excited Xenon-Atom Density in Accordance With Xenon Mole Fraction to Neon in Alternating-Current Plasma Display Panels by Laser-Absorption Spectroscopy

In this paper, spatiotemporal behavior of the excited Xe-atom density of metastable state was investigated by laser-absorption spectroscopy in alternating-current plasma display panel in accordance with the Xe mole fraction to Ne, which can be connected to the relative luminous efficiency over all spaces in a discharge cell. The various test panels with Xe mole fractions of 4%, 7%, 10%, and 15% to Ne have been used in this paper, in which discharge cell with T-typed indium-tin-oxide electrode and closed-barrier rib has been adopted. In this paper, the density of metastable state for the excited Xe atom is found to increase slowly beyond the Xe mole fraction of 10%. It is also accordingly noted that the luminous efficiency increases slowly beyond the Xe mole fraction of 10%, which is similar to that of the density of the excited Xe atoms in the metastable state in this paper.

Streamwise and spanwise plasma actuators for flow-induced cavity noise control

Plasma actuators operating in atmospheric air can induce a body force through collisions between electrically charged particles and neutral air molecules by an externally applied electric field. The fast response and the simple structure make the plasma actuator a promising option in aerospace applications. In this work, experiments were performed with several alternative current excited plasma (streamwise and spanwise) actuators to control flow-induced noise from a cavity. It was found that the streamwise actuator induced three-dimensional variations in the shear layer. The spanwise actuator, however, has little influence on the global flow field. As a result, the streamwise actuator is more effective than the spanwise actuator in cavity noise attenuation.

Calculation of breakdown voltage in plasma display panels

Plasma display panels play an important role in flat display panel market. The description of physical phenomena present in the alternative current plasma display panel discharges needs to know the breakdown voltage. This leads to minimize the applied voltage. The Paschen law gives the breakdown voltage for only pure gases. For this reason an analytical calculation has been done for pure gases and a xenon-neon mixture in order to estimate the breakdown voltage. This study makes it possible to see the importance of the parent gas. The results were obtained in an analytical approach to the numerical and experimental data.

Continuous Generation of TiO2Nanoparticles by an Atmospheric Pressure Plasma-Enhanced Process

A novel method for the continuous generation of titanium dioxide (TiO2) nanoparticles by dielectric barrier discharge process is presented using titanium tetraisopropoxide (TTIP) and water as precursors. The aerosol generator employs an atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process of alternative current (AC). The influences of applied voltage, frequency and precursor molar ratio on the generated particles were described by the SEM, XRD, and SMPS analyses. The results showed that TiO2 particles appear to be in a broad size range of bi-modal distribution when no voltage is applied. While after applying the AC plasma they become uni-modal distributed with average sizes range from around 30 to 60 nm. The applied electric frequency can be adjusted to either generate nanoparticles after the plasma reactor or develop a thin film in the reactor. An increase in the precursor molar ratio leads larger particles with a broader size distribution.