高温超导体超导态的场致发射

高温超导体处在临界温度以下时，能隙会引起体内电子分布的改变。本文在考虑到能隙对体内电子分布影响时，分析了高温超导体的场致发射电流密度和场致发射电子能谱。     

高温超导体超导态的光场发射研究

场致发射在低于场致发射电场阈值的场强作用下,发射体受脉冲激光照射时将会产生光场发射本文对高温超导体临界温度以下光场发射做一定的研究,并与高温超导体一般的场致发射情况做了一定的比较,两者有不同的发射规律．１引言 光场发射是发射体处于电场强度不及但接近场致发射阈值场强的条件下,输人激光脉冲激发电子发射的现象,其发射电子流受光脉冲控制．在低于场致发射电场阈值的场强作用下,高温超导体受脉冲激光照射也可以产生光场发射．当温度降到临界温度以下时高温超导体材料由正常态变成超导态,体内的电子形成库柏对,能隙会引…     

电场穿透对高温超导体场致发射电流的影响

高温超导体在场致发射时伴随正常态部分的空穴的产生 ,会出现非平衡现象。这会引起超导体电子平衡态的化学势偏移 ,增加外电场在高温超导体发射体内的穿透深度 ,使导带底弯曲影响超导体场致发射的电流。     

高温超导体场致发射的非平衡效应

高温超导体场致发射时 ,非平衡状态将使电场在超导发射体内增加穿透深度 ,这将使其场发射性质发生改变。本文对高温超导体场致发射的非平衡状态进行了研究。     

非平衡态对高温超导体光场致发射的影响

由于外加电场的作用 ,高温超导体材料体内电子平衡态的化学势偏移导致出现非平衡状态 ,这种非平衡状态将影响高温超导体光场致发射的性质。文中对高温超导体的光场致发射受非平衡态的影响进行了研究。     

高温超导体电场穿透对电子能谱的影响

高温超导体在场致发射时伴正常态部分的空穴的产生，会出现非平衡现象。这引起超导体电子平衡态的化学势偏移，增加了外电场在ＨＴＳＣ材料体内的穿透深度，使导带底弯曲引起超导体场致发射电子能谱的改变。     

非平衡态下高温超导体的光场致发射

外加电场的作用下高温超导体材料体内电子平衡态的化学势偏移导致出现非平衡状态，这种非平衡状态将影响高温超导体光场致发射的性质。本对高温超导体的光场致发射受非平衡态的影响进行了研究。     

临界温度左右高温超导体场发射电子能谱研究

本文研究了临界温度以上电场穿透发射体表面对高温超导体的场致发射电子能谱随温度变化的影响和临界温度以下能隙对场发射电子能谱影响的情况．并对理论计算的结果与实验结论做了比较．     

高温超导体场致发射电流理论研究

考虑到外电场在表面穿透引起导带能级变化的情况，推导了高温超导体的场致发射电流密度公式．利用该公式计算的结果与实验相符．     

三维热场致发射模型的数值模拟与研究

研究了场致发射与热电子发射的基本理论, 得出热场致发射的适用公式, 探讨了其粒子的初始分布和初始动量, 并在FDTD-PIC原理的基础上编写了软件, 分别实现了场致发射模型, 热电子发射模型和热场致发射模型, 通过分别对一个长楔形阴极器件的数值模拟, 从发射电流特性, 电子初始能量分布等方面验证了其正确性.     

Field emission characteristics of carbon nanotubes post-treated with high-density Ar plasma

The field emission characteristics of carbon nanotubes (CNTs) grown by thermal chemical vapor deposition (CVD) and subsequently surface treated by high-density Ar plasma in an inductively coupled plasma reactive ion etching (ICP-RIE) with the various plasma powers were measured. Results indicate that, after treated by Ar plasma with power between 250 and 500 W, the emission current density of the CNTs is enhanced by nearly two orders of magnitude (increased from 0.65 to 48 mA/cm²) as compared to that of the as-grown ones. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the structural features relevant to the modified field emission properties of CNTs. The SEM images of CNTs subjected to a 500 W Ar plasma treatment exhibit obvious damages to the CNTs. Nevertheless, the turn-on fields decreased from 3.6 to 2.2 V/μm, indicating a remarkable field emission enhancement. Our results further suggest that the primary effect of Ar plasma treatment might be to modify the geometrical structures of the local emission region in CNTs. In any case, the Ar plasma treatment appears to be an efficient method to enhance the site density for electron emission and, hence markedly improving the electric characteristics of the CNTs.     

Field electron emission from an aluminum oxide covered tungsten {112} plane at temperatures up to 1700°K

Field electron emission from an aluminum oxide mono-layer, face specifically adsorbed on a tungsten {112} plane, was measured between 1670°K and room temperature and at local field strength ranging from 17 MV/cm to 35 MV/cm. In a Fowler-Nordheim plot straight lines were obtained up to about 820°K. The work function at 650°K was determined to be 3.2 eV. The experimental values were compared with those determined by Christov's unified theory of field and thermionic emission. Deviations are attributed to the change in the shape of the potential barrier, which is caused by the aluminum oxide adsorption.     

Effect of deposition voltage on the field emission properties of electrodeposited diamond-like carbon films

Diamond-like carbon (DLC) films were deposited on Al substrates by electrodeposition technique under various voltages. The surface morphology and compositions of synthesized films were characterized by scanning electron microscopy and Raman spectroscopy. With the increase of deposition voltage, the sp² phase concentration decreased and the surface morphology changed dramatically. The influence of deposition voltage on the field electron emission (FEE) properties of DLC films was not monotonic due to two adverse effects of deposition voltage on the surface morphology and compositions. The DLC film deposited under 1200 V exhibited optimum FEE property, including a lowest threshold field of 13 V/μm and a largest emission current density of 904.8 μA/cm² at 23.5 V/μm.     

同轴空心阴极氦等离子体的电子激发温度研究

利用同轴空心阴极放电装置,产生氦低温等离子体。通过对等离子体的发射光谱进行测量和计算,研究放电功率以及氦气压强对等离子体的电子激发温度的影响。结果表明:氦低温等离子体的发射光谱主要由连续谱和原子谱线构成,放电功率和压强对谱线的强度具有明显影响。压强的变化不仅影响电子从电场中获得的能量,还会影响电子与原子的碰撞频率,从而导致电子激发温度随着氦气压强的增大,出现先上升后下降的变化趋势。     

电子束诱导沉积纳米线的电阻与场发射特性

"运用电子束诱导沉积技术在钨针尖表面沉积钨纳米线．在透射电子显微镜中,原位测量单根纳米线的电阻与场发射特性,并观察其显微结构变化．样品台为特制的电性能测试样品台,包括步进电机和压电陶瓷驱动的装置．导电铜片作为与纳米线相对的另一极．自行设计制作锁相放大器电路测量纳米线的电阻．结果表明,纳米线的电阻为0.1*10-3 -m量级．纳米线头部的几何缺陷将影响其场发射特性．纳安级电流将改变纳米线头部的几何结构与微观结构．场发射开启电压比结构变化前低11 V左右．"     

Field electron emission images of multi-walled carbon nanotubes

Field electron emission microscope images from multi-walled carbon nanotubes can typically be characterized by the presence of five pentagons surrounding a sixth central pentagon. The observations of bright line centered interference patterns between adjacent pentagons in the field electron emission microscope images of multi-walled carbon nanotubes have been reported in the literature. We have observed a shift from bright to dark line centered interference patterns and associated this with the presence of surface adsorption. In order to identify the origin of the contaminant, multi-walled carbon nanotubes were dosed with H₂, H₂O, CO and O₂ and then imaged in the field electron emission microscope. Only the samples exposed to O₂ showed a shift from a bright line centered pattern between adjacent pentagons of a clean surface to a dark line centered pattern when one pentagon was contaminated or a bright line centered pattern when both adjacent pentagons become contaminated. The results of the experimental studies and the modeling of the changes in the field emission pattern as phase shifts in the wave function of the tunneling electrons due to modifications in the surface work function are presented.