不同电场下碳纳米管场致发射电流密度研究  

Field-emission current densities of carbon nanotube under the different electric fields

作　　者：王益军[1] 严诚 

机构地区：[1]咸阳师范学院物理与电子工程学院,咸阳712000 [2]微光夜视技术重点实验室,西安710065

出　　处：《物理学报》2015年第19期292-297,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11075135;61307002);陕西省自然科学基金(批准号:2012JM1009);陕西省教育厅科学研究计划项目(批准号:12JK0984);咸阳师范学院专项科研基金项目(批准号:12XSYK014;13XSYK010);咸阳师范学院教育教学改革研究项目(批准号:201200127;201302026)资助的课题~~

摘　　要：本文运用密度泛函理论和金属电子论,深入研究了碳纳米管场致发射电流的变化规律.结果显示其发射电流密度取决于体系的态密度、赝能隙、管长和局域电场,在不同范围电场下的变化规律不同.在较低电场下,发射电流密度随电场增强而近似线性增大(对应的宏观电场须小于18 V·μm-1);但在较高电场下,发射电流密度随外电场增加呈现非周期性振荡增长趋势,碳纳米管表现为电离发射.本文进一步研究了金属性碳纳米管电导率在不同电场下的变化规律.The field emission current variation law of carbon nanotube in a large electric field range （0–32 V·μm-1 is analyzed in depth by combining the density functional theory with metal electron theory. The results show that their emission current densities are determined by their densities of states, the pseudogap, the length and the local electric field, showing the different variation laws in the different electric field ranges. In the lower electric field （corresponding macroscopic field is less than 18 V·μm-1, when their density of states increases, their pseudogap decreases： the two trends are opposite, the former increases the number of electrons for emission, and the latter improves the ability to transfer electrons, they all turn to the increase of the emission current, so their field-emission current density increases linearly with increasing electric field in this range. But in the higher electric field （corresponding macroscopic field is less than 32 V·μm-1and more than 18 V·μm-1）, their densities of states and the pseudogaps take on the same decrease and increase, so do they in the opposite change case, therefore the emission current density behaves as a non-periodic oscillation in the increasing electric field, moreover the higher electric conductivity lead to the rising of current density, the combined effect of the emitter current density exhibits an oscillatory growth in this electric field range, and the carbon nanotubes behave as ionizing radiation. So the too high electric field may cause the emission current to be instable. The electric conductivity variation law of the metallic carbon nanotube is further studied in this paper. In the lower electric field （corresponding macroscopic field is less than 5 V·μm-1, the electric conductivity of CNT increases linearly with increasing electric field;when the macroscopic electric field increases up to a value in a range from 5 to 14 V·μm-1 the electric conductivity only changes like a slight concussion in （6.3–9.9） × 1017 S�

关 键 词：碳纳米管 场致发射 电流密度 电导率 

分 类 号：TB383.1[一般工业技术—材料科学与工程]