High-efficient production methods of microplasma using nano-size-structured and active-functional electrodes

为了有效地产生微等离子体，已经开发了纳米尺寸结构和/或活性功能电极。由于等离子体的表面积与体积之比很大，因此等离子体与表面的相互作用，特别是在提供电子的电极上的相互作用，对于维持微尺寸等离子体将是重要的。我们成功地在金刚石纳米晶须上制备了碳纳米管阴极材料，大大提高了电子场发射性能。研究结果表明，微间隙放电由于宇宙射线电离几率小，其击穿电压远高于常规气体放电。用碳纳米管作阴极，成功地降低了击穿电压，提出了用优良的场发射材料作阴极，在大于1 MPa的高压下，用小于10 μm的电极间隙，使场发射电子激发微等离子体。由于在高压下很难控制微小的间隙，因此通过连续场发射维持微等离子体的挑战还没有被成功地证明。通过对样品的原位观察，证实了微等离子体是在扫描电镜腔室中局部产生的。对于差动泵送的局部气体喷射，采用小孔作为气体喷嘴是合适的。SEM中的微等离子体工艺将有助于集成电路的局部修复和微器件的制造。利用时间-空间分辨发射光谱测量技术研究了以Ar气代替He气的低频微等离子体射流。实验结果表明，在氩气的作用下也能维持稳定的微等离子体射流，并初步阐明了LF射流的产生机理。

For efficient production of micro-plasma, nano-size-structured and/or active-functional electrodes have been developed. It is expected that the plasma-surface interaction, especially on the electrode providing electrons, will be important to sustain micro-size plasma due to its large ratio of the surface area to the volume.In this research, it has been examined to use diamond with excellent material properties and carbon nanotubes (CNTs) with fine nano-structures. We have succeeded to fabricate CNTs on diamond nano-whiskers for cathode material with highly improved electron field emission property. It was confirmed that the breakdown voltage in a micro-gap discharge were extremely higher than the conventional gas discharge due to small probability of ionization by cosmic ray. By using CNTs for cathode, the breakdown voltage was successfully decreased.It was proposed that with using excellent field emission material for cathode in a higher pres-sure more than 1MPa with a smaller electrode gap below 10 μm, it would make field emission electron excited microplasma. The challenge to sustain microplasma by the continuous field emission has not been demonstrated successfully because of difficulty in controlling the small gap in the high pressure. However, some important experimental parameters have been clarified.It was also demonstrated that microplasma was produced locally in a SEM chamber with in-situ observation of the specimen. For the local gas injection in the differentially pumping, it was suitable to use a small orifice as a gas nozzle. The microplasma process in SEM will be useful for local recovery of integrated circuits and fabrication of micro devices. LF (low frequency) microplasma jet using Ar gas instead of conventional He was also studied by time-spatial resolved optical emission spectroscopic measurements. It was succeeded to sustain stable microplasma jet also with Ar and the generation mechanism for LF jet was mostly clarified.