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1.
陈钦  李统藏  石勤伟  王晓平 《物理学报》2005,54(8):3962-3966
采用紧束缚模型研究了悬挂端对单壁碳纳米管电子输运特性的影响.结果表明:有限长悬挂端开口碳纳米管的电导在费米能级附近作周期性振荡.椅型(armchair)碳纳米管的振荡同时具有快、慢两个准周期,而锯齿型(zigzag)碳纳米管的振荡仅有一个周期;碳纳米管电导在费米能级附近的振荡周期随着悬挂端的增长而减小.研究还发现:有限长悬挂端开口碳纳米管的平均电导随探针与碳纳米管间耦合强度的增加而增大,其大小约为无限长悬挂端开口碳纳米管平均电导的两倍. 关键词: 输运特性 碳纳米管 紧束缚模型  相似文献   

2.
通过采用转移矩阵方法求解自旋电子隧穿过程,理论研究了半导体超晶格系统中电子自旋输运的磁电调控行为.结果表明:仅对超晶格系统施以磁调制,隧穿系数将出现自旋分裂,随磁场增强,电导自旋极化率变大且展宽于费米能区;若选取不变磁场情况,同时施以间隔周期电场调制,超晶格的电子极化率将有更为显著地提高.进一步发现,随电场强度的改变,电子自旋输运行为显然存在两个明显不同区域,下自旋电子将在不同调制区域表现为不同的变化趋势.然而,若对周期磁超晶格施加间隔两周期的电调制,自旋电导输运的临界行为消失,电导极化率在高能区的共振峰 关键词: 半导体超晶格 自旋输运 磁电调控  相似文献   

3.
刘曼  闫强  周丽萍  韩琴 《物理学报》2014,(7):314-320
运用基于第一性原理的密度泛函理论(DFT)的非平衡格林函数(NEGF)方法对过渡金属原子嵌入后的单壁碳纳米管(SWCNT)的电子输运性质进行了研究.构建并优化不同过渡金属原子填充进不同类型碳纳米管的模型,研究其对应的电荷和自旋传输性质.发现所有体系都在费米面附近出现自旋相关的电导下降峰,数值为一个量子电导(2e2/h).碳管内封装两个铁原子的体系,磁性状态的改变导致不同的电输运行为,这一性质提供了新的有前景的方法来检测原子尺度上的磁特性.  相似文献   

4.
运用基于第一性原理的密度泛函理论(DFT)的非平衡格林函数(NEGF)方法对Li原子嵌入后的zigzag型单壁碳纳米管(SWCNT)的电子输运性质进行了研究.在构建和优化了Li原子嵌入的zigzag型单壁碳纳米管的电子输运模型后,研究了该系统的电子传输概率、能态密度、电子透射谱,还研究了电子能量和偏置电压设置与变化对其电子输运特性的影响.结果显示zigzag型单壁碳纳米管嵌入Li原子后,电子输运特性发生了较大变化,具有电子输运拓宽效应和量子台阶复苏效应. 关键词: Li原子 碳纳米管 电子输运 拓宽效应  相似文献   

5.
蔡建臻  朱宏伟  吴德海  刘峰  吕力 《物理学报》2006,55(12):6585-6588
单壁碳纳米管在高压下会发生结构相变,导致金属型的碳纳米管变成半导体.相变后碳纳米管中电子的库仑关联的表现形式发生变化,从Luttinger liquid行为转变成环境量子涨落行为.同时,相变后电子波函数的相位关联导致弱局域化行为的出现.为了研究库仑关联和相位关联之间是否有相互影响,使用金刚石对顶砧和液压自锁高压包在0—10 GPa准静压范围内测量了单层碳纳米管样品在低温和不同磁场下的微分电导随偏压的依赖关系.实验结果表明,相位关联和库仑关联是两种独立的效应,各自影响着电子的输运行为. 关键词: 单层碳纳米管 高压 微分电导  相似文献   

6.
有限长双壁碳纳米管的电子输运性质   总被引:2,自引:0,他引:2       下载免费PDF全文
陈将伟  杨林峰 《物理学报》2005,54(5):2183-2187
基于Landauer公式,研究了有限长的非公度和公度双壁碳纳米管的电子输运性顾,结果表明 ,双壁管的几何结构对其电子输运性质有显著的影响:非公度的双壁碳管的电导随能量的不 同,既可以是弹道型的,也可以是非弹道型的;由armchair管组成的公度的双壁碳管的电导 随能量变化呈现快速的电导振荡,并且此快速振荡叠加在背景慢振荡上,而zigzag管组成的 公度双壁管的电导随能量变化只有快速振荡、没有规则的慢振荡背景. 关键词: 碳纳米管 电子输运性质  相似文献   

7.
采用密度泛函理论和非平衡格林函数方法研究了纯净的及带有不同数目的 Stone-Wale拓扑缺陷下的扶手椅型单壁,双壁和三壁小管径碳纳米管的能带结构和电子输运性质,通过计算并分析不同偏压下的微分电导和非弹性电子隧穿谱(IETS),计算结果表明单壁,双壁和三壁碳纳米管的特征偏压区间分别为[-1.0 V,1.0 V],[-0.5 V,0.5 V]和[-0.25 V,0.25 V],特征偏压区间内SW拓扑缺陷所产生的电导波动平缓,而特征偏压区间外因缺陷的数目变化所带来的电导波动显著,通过IETS谱线的分析得到单壁,双壁和三壁碳纳米管的特征峰偏压分别为±1.25 V,±0.625 V和±0.125 V.碳纳米管的特征偏压区间和IETS特征峰偏压可为较小管径碳纳米管单壁,双壁和多壁类型的区分提供一种新的途径,同时也为小管径多壁碳纳米管的输运性质在出现拓扑缺陷时的响应提供参考依据.  相似文献   

8.
采用密度泛函理论和非平衡格林函数方法研究了纯净的及带有不同数目的Stone-Wale拓扑缺陷下的扶手椅型单壁, 双壁和三壁小管径碳纳米管的能带结构和电子输运性质, 通过计算并分析不同偏压下的微分电导和非弹性电子隧穿谱(IETS), 计算结果表明单壁, 双壁和三壁碳纳米管的特征偏压区间分别为[-1.0V, 1.0V], [-0.5V, 0.5V] 和[-0.25V, 0.25V], 特征偏压区间内SW拓扑缺陷所产生的电导波动平缓, 而特征偏压区间外因缺陷的数目变化所带来的电导波动显著, 通过IETS谱线的分析得到单壁, 双壁和三壁碳纳米管的特征峰偏压分别为 1.25V, 0.625V和 0.125V. 碳纳米管的特征偏压区间和IETS特征峰偏压可为较小管径碳纳米管单壁, 双壁和多壁类型的区分提供一种新的途径, 同时也为小管径多壁碳纳米管的输运性质在出现拓扑缺陷时的响应提供参考依据.  相似文献   

9.
赵起迪  张振华 《物理学报》2010,59(11):8098-8103
系统地计算了各种手性碳纳米管最低导带的电子速度和有效质量的变化规律,在此基础上推断手性碳纳米管低偏压下的输运特征,计算表明:在低偏压电子输运时,同一系列(手性角相同)的各种手性金属碳纳米管的输运性质相同,与管径无关,但不同系列的手性金属碳纳米管的输运性质有明显区别;而同一系列的各种手性半导体型碳纳米管的输运性质有一定差异,但不同系列的手性半导体型碳纳米管的输运性质有着显著差异.这一结果说明:碳纳米管在低偏压下的输运特征与系列有着密切的关系,手性角是决定各种碳纳米管在低偏压下具有不同输运性质的最关键的几何参 关键词: 碳纳米管 手性角 电子速度 有效质量  相似文献   

10.
张迷  陈元平  张再兰  欧阳滔  钟建新 《物理学报》2011,60(12):127204-127204
采用格林函数方法研究了堆叠石墨片对锯齿型石墨纳米带电子输运性质的影响,计算了两种不同堆叠方式下锯齿型石墨纳米带的电导.研究发现,由于堆叠石墨片与石墨纳米带的耦合作用,锯齿型石墨纳米带的电导谱出现了电导谷.在远离费米能处,两种堆叠方式下的电导谷位置相近甚至重合;而在费米能附近,两种堆叠方式下的电导谷存在差异.此外,讨论了堆叠石墨片的几何尺寸对锯齿型石墨纳米带电子输运的影响.结果显示,随石墨片几何尺寸的增大,锯齿型石墨纳米带在两种堆叠方式下远离费米能处的电导谷逐渐向费米能方向移动,同时其费米能附近的电导谷在两种堆叠方式下的差异随石墨片尺寸的增大变得更为明显.研究结果表明,堆叠石墨片能够有效地调制锯齿型石墨纳米带的电子输运性质.  相似文献   

11.
The universal features of quantized thermal conductance of carbon nanotubes (CNTs) are revealed through a theoretical analysis based on the Landauer theory of heat transport. The phonon-derived thermal conductance of semiconducting CNTs exhibits a universal quantization in the low-temperature limit, independent of the radius or atomic geometry. The temperature dependence follows a single curve given in terms of temperature scaled by the phonon energy gap. The thermal conductance of metallic CNTs has an additional contribution from electronic states, which also exhibits quantized behavior up to room temperature.  相似文献   

12.
苑朋山 《光谱实验室》2012,29(3):1918-1920
基于MATLAB语言数值模拟了碳纳米管的能隙特性和态密度特性,得出碳纳米管能隙的变化与碳纳米管的手性有关。数值模拟了碳纳米管的态密度表示,通过态密度表示与能隙对比,结果吻合的较好。结论为碳纳米管器件的制作提供参考。  相似文献   

13.
The influence of vacancy percentage on the energy gap of zigzag single-wall carbon nanotube is investigated by the Green's function method in coherent potential approximation. Our probes for various kinds of zigzag single-wall carbon nanotubes show that by increasing vacancy percentage the energy gap is also increased, so for metallic single-wall carbon nanotubes, a metallic to semi-metallic transition is occurred. However, any transition does not appear for semiconductor carbon nanotubes. So by controlling on concentration of vacancies, one can make a semiconductor SWCNT with a predetermined energy gap which is useful in nanoelectronic devices.  相似文献   

14.
轴向磁场对碳纳米管电子性质的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
张助华  郭万林  郭宇锋 《物理学报》2006,55(12):6526-6531
用紧束缚法研究了单壁碳纳米管在轴向磁场下费米能级附近电子性质的变化规律.研究发现:能隙随轴向磁场变化的快慢及磁致能隙峰值都与碳纳米管直径有着紧密联系;对于相同直径的碳纳米管,金属性管的磁致能隙峰值最大.具体计算了锯齿型碳纳米管费米能级附近电子态密度随轴向磁场的变化关系,发现所有碳纳米管的电子态密度和能隙变化都体现出周期性.磁场使得碳纳米管发生绝缘体-金属周期性相转变的根本原因是由于在磁场的作用下范霍夫奇异点出现分裂-移动-融合的周期性变化. 关键词: 磁场 碳纳米管 紧束缚法 范霍夫奇异点  相似文献   

15.
We report measurements on the radial electromechanical properties of single walled carbon nanotubes. By measuring the conductance of the nanotube, we show that a gap is opened while squashing the nanotubes and that during the deformation stages we observe at least two open-close cycles of the gap. We employ a novel experimental setup where an atomic force microscope tip is used both as an electrode and to induce radial deformations. In contrast with prior experiments reported, this technique allows direct probing of the local electronic structure of carbon nanotubes as they are radially deformed.  相似文献   

16.
We fabricated reproducible high transparency superconducting contacts consisting of superconducting Ti/Al/Ti trilayers to gated single-wall carbon nanotubes. The reported semiconducting single-wall carbon nanotubes have normal state differential conductance up to 3e2/h and exhibit clear Fabry-Perot interference patterns in the bias spectroscopy plot. We observed subharmonic gap structure in the differential conductance and a distinct peak in the conductance at zero bias, which is interpreted as a manifestation of the supercurrent. The gate dependence of this supercurrent as well as the excess current are examined and compared to the coherent theory of superconducting quantum point contacts with good agreement.  相似文献   

17.
We have studied the electrical conductance of gas-desorbed multiwalled carbon nanotubes (MWNTs) at high temperatures, and found a peculiar linear temperature dependence of conductance over a wide temperature range from 100 to 800 K. We interpret this phenomenon by using a thermal activation picture of conduction channels below the gap in the vicinity of the Dirac points. The result also indicates a very short and temperature-independent electron mean free path in our MWNTs, and provides a way to determine the number of residual conduction channels in the MWNTs.  相似文献   

18.
By applying non-equilibrium Green's functions in combination with density-functional theory, we investigate electronic transport properties of C60 coupled to carbon nanotubes and Li electrodes. The results show that electronic transport properties of CNT-C60-CNT and Li-C60-Li systems are completely different. Nonlinear I-V characteristic, varistor-type behavior and negative differential resistance (NDR) phenomenon are observed when electrodes are carbon nanotubes. We discuss the mechanism of I-V characteristics of CNT-C60-CNT systems in details. Our results suggest conductance, energy level of Frontier molecular orbitals, energy gap between HOMO and LUMO, the coupling between molecular orbitals and electrodes are all playing critical roles in electronic transport properties.  相似文献   

19.
The effect of oxygenation on the electronic properties of semiconducting carbon nanotubes is studied from first principles. The O2 is found to bind to a single-walled nanotube with an adsorption energy of about 0.25 eV and to dope semiconducting nanotubes with hole carriers. Weak hybridization between carbon and oxygen is predicted for the valence-band edge states. The calculated density of states shows that weak coupling leads to conducting states near the band gap. The oxygen-induced gap closing for large-diameter semiconducting tubes is discussed as well. The influence of oxygen on the magnetic property is also addressed through a spin-polarized calculation and compared to experiment.  相似文献   

20.
Using the π orbital tight-binding model and the multi-channel Laudauer-Büttiker formula, the combined effect of Aharonov-Bohm effect (induced by an axial magnetic field) and uniaxial strain on quantum conductance oscillations of the electronic Fabry-Perot resonators composed of armchair and metallic zigzag single-walled carbon nanotubes (SWNTs) has been studied. It is found that, for the case of the armchair SWNT, conductance oscillations near the band gap are dominated by Aharonov-Bohm effect, while the conductance oscillations in other regions are dominated by the uniaxial strains. The combined effect of Aharonov-Bohm effect and uniaxial strains on quantum conductance oscillations is not obvious. But, for the case of the metallic zigzag SWNTs, obvious single-channel transport and one or two conductance oscillations existing in two different gate voltage ranges were found by the combined effect of uniaxial strain and axial magnetic field.  相似文献   

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