Summary

High pressure glow discharges stabilized by operating with relatively small characteristic dimensions have been given the term “microplasma”. With the intersection of plasma science, photonics and materials science, microplasma device science and technology offers not only a new realm of plasma application but also device capability. The first and second conferences about microplasma are organized in 2003 and 2004 respectively and the third International Workshop on Microplasmas (IWM) is held in Germany, 2006. The growth of this series of microplasma conference shows the developing potential of microplasmas. Recent examples of microplasma devices developed with many configurations, such as inverted pyramid, planar electrode and three dimensional structures. Moreover, materials of microplasma device are also the critical research topics in the development of microplasma device. Research and development on microplasma devices reveal the characteristics which are well-behaved electrically and optically and appear to be valuable and feasible applications such as active display and backlighting [27].

This work was devoted to the characterization of nano-tip enhanced microplasma device in neon, argon and Ne+Ar(2%). Using nano-tip is to locally enhance the electric field and reduce the discharge voltage. This article presents the panel type microplasma devices with nano-tip enhanced electrodes and demonstrates that the

proposed devices have been successfully fabricated and operated with various direct current bipolar pulsed excitation frequencies from 2 to 20 kHz in neon, argon and Ne+Ar(2%) gas mixture. The nano-tip enhanced microplasma devices are characterized by abnormal glow discharge properties and low discharge voltages were acquired due to the fact that the local electric field distribution is heightened by the nano-tips. Operating at pressure up to 800 Torr at voltage as low as 250 V provides stable glow discharge phenomena. Large voltage margin of our proposed devices reveals the potential of wide operating range in future device. Simple fabrication of the devices is an obvious advantage to procure the larger area panel type nano-tip enhanced microplasma devices. The nano-tip enhanced microplasma device technology provides advantages which are discharge voltage, lifetime, brightness, and efficiency. The high resolution patterns with nano-tips, low discharges voltage obtained from the short distance between panel electrodes and the strong emission from the nano-tips can be provided from the proposed devices. Furthermore, with the advantages which are discharge voltage, lifetime, brightness, and efficiency, the nano-tip enhanced microplasma technology provides possible opportunity to integrate with broad applications.

5.2 Future work

Despite the encouraging results of this study as to the positive of using nano-tip enhanced electrodes in the microplasma devices, future research is required in a number of directions. The work we presented is an exciting first step and among the many topics to be explored in future research and some important ones can be discussed as following sections.

5.2.1 Phosphor

In this work, the proposed nano-tip enhanced microplasma device is only one line device. In the future, multi-line and full size panel microplasma device are desired. Because Red, Green, Blue and White (RGBW) colors are desired for display application, vacuum ultra-violet (VUV) excitable phosphors is capable of achieving this future work. To avoid destroying the nano-tip, a spraying method with spray nozzle is commented to grow phosphor layer in the proposed devices. According to the full size panel microplasma device with phosphors, it can provide potential of application on flat plasma light source

5.2.2 Dielectric layer

From the observation of long time operation, there is some erosion which comes from the ion bombardment phenomena on the nano-tip. In order to avoid the erosion, a dielectric layer can be deposited on rear metal electrode to protect the nano-tip enhanced electrode. Base on the plasma display panel (PDP) technology, Magnesium Oxide (MgO) is the best candidate in this future work. MgO can provide low sputtering rate and high secondary emission coefficient. With depositing the MgO thin film, the life time of proposed device is confidently longer.

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