【作者】 陈云；

【导师】 张健；

【作者基本信息】 华东师范大学 ， 微电子学与固体电子学， 2013， 博士

【摘要】 气体放电研究,尤其是微小问隙下的放电,具有突出的学术价值。一方面,在集成电路和MEMS等器件中,放电击穿是应着力避免的问题；另一方面,在新型的气体传感器、气体除尘、离子推进等领域,放电击穿是重要的分析和应用手段。因此,对材料的电学击穿以及放电行为进行系统的研究显得非常有必要。对纳米材料在小间隙低电压的情况下的放电行为的研究,尚处于起步阶段,更是目前的研究热点之一。本文以硅纳米线(SiNWs)作为研究对象,研究其制备、修饰,以及在场致电子发射、电晕放电和气体电离等方面的性能。论文的主要内容和研究结果如下：第一,完成了硅纳米电极的优化制备,并以此为基础,首次在其上进行了金纳米粒子修饰,得到了Au/SiNWs电极。运用金属辅助化学湿法刻蚀,制备了直径在50-300nm左右,具有高长径比的直立结构的SiNWs,并研究了刻蚀参数对纳米线形态的影响。通过硅烷偶联剂APTMS将金纳米粒子成功组装到SiNWs表面,金纳米粒子的平均直径为10nm,且修饰的金纳米粒子为单晶,含量为7.26%。第二,研究了SiNWs以及金纳米粒子修饰的SiNWs (Au/SiNWs)的真空场发射性能,获得了超低的开启电场。首先,研究了不同类型硅片制成的SiNWs的场发射性能,发现n型低掺杂SiNWs的场发射性能最好。其次,采用SiNWs/金纳米粒子复合结构来提高场发射性能,发现经过修饰以后的SiNWs勺场发射性能有了很大的改进,开启电场由未修饰的1.76V/μm降低至0.17V/μm。同时由于金纳米粒子的修饰作用,提高了SiNWs的导电性能,所以电流密度也因此增大。接着研究了SiNWs和Au/SiNWs的变温场发射特性。发现SiNWs的场发射性能随着温度的增加而能略有所提高,在各个温度下的电流密度有明显差异。而随着温度的升高Au/SiNWs勺场发射性能明显提高。最后,鉴于SiNWs表面本证氧化层的存在,提出了基于MIS的SiNWs能带模型,分析了场发射的机理。第三,采用SiNWs尖端-金属平面电极结构,研究了常温常压下,SiNWs电极的正电晕和负电晕放电特性。首先,采用简化的针尖-平面电极模型,进行了放电器件设计。接着对此结构在常温常压下进行测试,得到正电晕放电的起始电压在700V左右,稳定的正电晕放电工作电压的范围为700-1600V。负电晕放电起始电压在400V左右,负电晕放电工作电压的范围为400-1700V,发现负电晕的电晕范围比正电晕放电时更大,负电晕放电的性能要比正电晕放电稳定。最后,根据电晕放电电压-电流的拟合公式进一步研究了多针尖-平面电极结构的电晕放电特性。第四,利用微机械加工的SiNWs电极,研究了微米间隙尺度(1-20μm)时SiNWs电极的气体电离特性,发现微小间隙下放电规律与经典Paschen公式的背离。首先,利用MEMS技术制作出两种间隙在微米级可控的电极结构。一种是通过刻蚀玻璃,形成玻璃凹槽式电极结构；一种是对硅表面进行选择性刻蚀,形成硅凹槽式电极结构。接着在常温常压下研究SiNWs的电离全伏安特性,测得空气的击穿电压仅为21±1V左右,远远低于其他一维纳米材料的击穿电压。其次分别研究两个特征量即气压P和电极间隙d对气体电离的影响。随着压力对数降低,气体击穿电压和击穿电流均随之呈线性降低。当电极间隙小于7μm,击穿电压关于电极间隙d呈强线性关系,背离Paschen曲线。当电极间隙大于7μm,击穿电压与Paschen曲线基本符合。研究了电极极性、纳米电极掺杂类型和浓度等对气体电离的影响。研究发现,n型低掺杂SiNWs的击穿电压小于p型的击穿电压,击穿电流大于p型的击穿电流。而p型低掺的击穿电压和电流均低于p型高掺的击穿电压。更多还原

【Abstract】 Gas discharge research, especially the discharge under small gap, has outstanding academic values. On one hand, in the fields of integrated circuits and MEMS devices, discharge breakdown is harmful and should be avoided; the other hand, in the areas of new gas sensors, electrostatic precipitators, ion propulsions, discharge breakdown is becoming an important means of analysis and application. Therefore, the electrical breakdown of the material and the discharge behavior of the system are very necessary. The discharge behavior research of nanomaterials under the small electrode distance and low-voltage, is still in its infancy, and is becoming into one of the hotspots. In this thesis, silicon nanowires (SiNWs) were studied as the research object. The nanostructures fabrication and modification, as well as its application in electron emission, corona discharge and gas ionization were analyzed. The main contents and results are as follows:Firstly, the preparation and optimization of SiNWs electrodes were carried out and the gold nanoparticles decorated SiNWs electrodes were fabricated. SiNWs were first prepared by metal-assisted wet chemical etching. The vertically aligned silicon nanowire arrays with the average diameter of100nm were obtained and have high field enhancement factor. The influence of the process parameters such as etchant solution concentration, temperature, doping type on the nanowires appearance was studied. Gold nanoparticles(AuNPs), prepared by reduction of chloroauric acid, with the average diameter of10nm, were assembled onto the surface of SiNWs with APTMS as coupling agent to form the Au/SiNWs nanocomposite electrode. And the AuNPs were single crystal with content of7.26%.Secondly, the field emission (FE) behaviors of SiNWs and Au/SiNWs composites were studied and the ultra-low turn-on electric field was obtained. First, the FE performance of SiNWs, made from wafers with different doping types and doping concentrations, was investigated. And the study indicated that lightly-doped n-type SiNWs has the higher FE perfromance. Next, the FE characteristics of Au/SiNWs nanocomposite were studied. It is found that by introduction of AuNPs, the FE performance of SiNWs can be improved remarkably:the turn-on field can be reduced from1.76V/μm (SiNWs) to0.17V/(.μm (Au/SiNWs). On this foundation, the variable temperature field emission characteristics, i.e., the field emission properties of SiNWs and Au/SiNWs under different temperatures, had also been studied. The FE performance of the SiNWs increased slightly with temperature, the current density at various temperatures are different. For Au/SiNWs, the FE characteristics increased obviously with temperature. At last, in view of the existence of silicon dioxide, we proposed the MIS-Schottky band model for SiNWs and analyzed the possible FE mechanism.Thirdly, under the atmospheric pressure, with SiNWs electrodes as needle electrode and metal as plane electrode, the positive corona and negative corona discharge characteristics of SiNWs was been studied. According to the mechanism of needle-to-plane corona discharge, the corona discharge electrode was designed. The onset voltage of positive corona discharge is about700V voltage, and the stable working voltage range of the corona discharge is700-1600V. The onset voltage of negative corona discharge is about400V voltage, and the stable working voltage range of the corona discharge is400-1700V.Fourthly, the micro-gap, l-20μm, ionization behavior of micromachined SiNWs electrodes at atmospheric under room temperature were investigated, and the departure from the classical Paschen’s curve was found. First, two kinds of micromachined ionization devices with controllable micron level electrode gap were fabricated. Both of them consist of SiNWs electrode and glass electrode. The first one is that glass is etched to form the concaved-glass/SiNW structure. And the second one is to selectively to fabricate SiNW to form the concaved-SiNW/glass structure. The homemade ionization testing system was used. Ionization devices were tested and the corresponding I-V characteristics of the air ionization at atmospheric were recorded and analyzed. The obtained breakdown voltage in air is only about21V, which is smaller than other similar structures with one-dimensional nanomaterials. The effects of two parameters, pressure P and electrode gap distance d, were discussed respectively. When the pressure reduced logarithmically, both the current and the gas breakdown voltage linearly decreased accordingly. When the electrode gap is less than7μm, breakdown voltage showed strong linear relation with the gap distance d, departure from the Paschen’s curve. The influence of parameters, e.g., electrode polarities, doping type and doping concentration of SiNWs, on gas ionization were also been studied. The results as following:the breakdown voltage of n-type low doped SiNWs is less than p-type low doped, but on the contrary of the breakdown current. And the breakdown voltage and current of p-type low doped SiNWs were both below p-type high doped SiNWs.更多还原