共查询到20条相似文献,搜索用时 15 毫秒
1.
S. K. Jung S. W. Hwang D. Ahn J. H. Park Yong Kim E. K. Kim 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
We report on the fabrication and the characterization of quantum dot transistors incorporating a single self-assembled quantum dot. The current–voltage characteristics exhibit clear staircase structures at room temperature. They are attributed to electron tunneling through the quantized energy levels of a single quantum dot. 相似文献
2.
基于碳纳米管的良好导电性、激子传输性能和量子点聚合物复合材料高的光电转换性能, 采用原位缩合法制备了聚合物聚(2-甲氧基-5-辛氧基)-对苯乙炔(MOPPV)功能化碳纳米管(SWNT)-PbSe量子点复合材料, 通过对复合材料的X射线衍射、透射电子显微镜和紫外可见吸收光谱研究, 发现MOPPV, SWNT与PbSe量子点可以有效地复合, 且SWNT与MOPPV形成网状结构; PbSe量子点尺寸为5.75 nm, 其可均匀地分散在MOPPV-SWNT基体中形成包覆或镶嵌结构, 并发生了光诱导电荷转移.通过对复合材料的光电性能研究发现, 当MOPPV, SWNT, PbSe三者的质量比为1: 0.3 : 1 时其光电性能最好, 开路电压为0.556 V, 短路电流为2.133 mA, 填充因子为34.48%, 转换效率为0.452%, 与聚合物MOPPV-PbSe量子点复合材料材料相比, 光电性能提高了2–3倍.
关键词:
量子点
碳纳米管
复合材料
转换效率 相似文献
3.
采用化学气相沉积方法制备的碳纳米管,用酸溶液进行弱氧化处理,经适当温度在大气中烧 灼后碳纳米管发生弯曲,在样品中出现大量的环状结构. 利用原子力显微镜、透射电子显微 镜和扫描电子显微镜对典型环直径为300 nm的碳纳米管环进行了表征. 烧灼温度和烧灼时间 对环的结构和产率有重要的影响. 实验数据统计结果表明,烧灼温度在510—530℃区间内 可得到超过40%的碳纳米管环产率,并且烧灼时间延长到120 min有利于提高碳纳米管环的产 率. 在加热情况下,碳纳米管端结合的羧基官能团脱水成酯,导致弯曲的碳纳米管结合成环 .
关键词:
碳纳米管环
化学气相沉积 相似文献
4.
This paper studies the quantum conductance properties of
three-terminated carbon nanotube Y-junctions, which are built by
connecting three (5,5) single-walled carbon nanotubes. The results
show that the quantum conductance at the Fermi energy oscillates
periodically with the junction's size, and the number of oscillating
periodic layers is 3 which is the same as that in the two terminated
$(10,0)/m(5,5)/(10,0)$ junctions. Moreover, this Y-junction with
different size exhibits obvious different distribution of electron
current in the two drain branches, called shunt valve effect of
electronic current. Thus the degree of this effect can be controlled
and modulated directly by constructing the three branches' sizes or
the distribution of defect. The results show in detail that the
difference between the two drain currents can be up to two times for
some constructions with special sizes. In addition, the uniform
distribution of defects in the Y-junction leads to lower quantum
conductance than that of other defect configurations. 相似文献
5.
6.
Fabrication and electrochemical properties of free-standing single-walled carbon nanotube film electrodes 下载免费PDF全文
An easily manipulative approach was presented to fabricate electrodes using free-standing single-walled carbon nanotube (SWCNT) films grown directly by chemical vapor deposition.Electrochemical properties of the electrodes were investigated.In comparison with the post-deposited SWCNT papers,the directly grown SWCNT film electrodes manifested enhanced electrochemical properties and sensitivity of sensors as well as excellent electrocatalytic activities.A transition from macroelectrode to nanoelectrode behaviours was observed with the increase of scan rate.The heat treatment of the SWCNT film electrodes increased the current signals of electrochemical analyser and background current,because the heat-treatment of the SWCNTs in air could create more oxide defects on the walls of the SWCNTs and make the surfaces of SWCNTs more hydrophilic.The excellent electrochemical properties of the directly grown and heat-treated free-standing SWCNT film electrodes show the potentials in biological and electrocatalytic applications. 相似文献
7.
T. Mihara K. Miyamoto M. Kida T. Sasaki N. Aoki Y. Ochiai 《Superlattices and Microstructures》2003,34(3-6):383
A multiwall carbon nanotube crossroads has been fabricated by a manipulation technique using a glass microcapillary, and the low temperature transport properties investigated. The two-terminal conductance of an individual tube shows Tomonaga–Luttinger liquid behavior G∝Tα at high temperature and dI/dV ∝V α at low temperature. However, no evidence of such a power-law behavior is obtained in the four-terminal conductance at the junction, where the conductance shows an almost metallic behavior ‘corrected’ by weak localization. Weak localization would essentially appear in electron states at the junctions of MWNTs. 相似文献
8.
基于量子点接触探测器(QPC)理论上研究了双量子点(DQD)系统在耗散环境和纯退相环境影响下的电子转移特性.结果表明,耗散环境中探测器导致的退相干会增大平均电流和Fano factor随时间演化的值,并观察到量子芝诺效应的存在.在对称的DQD情况下,弛豫减小了平均电流随时间演化的震荡振幅.在非对称的DQD情况下,弛豫降低了Fano factor随时间演化的峰值.纯退相环境中测量会阻碍共隧穿过程中不同电流通道之间的转换,导致Fano factor的极高值.在对称的DQD情况下,增大纯退相速率会提高Fano factor.在非对称的DQD情况下,动力学随时间的演化对纯退相环境不敏感.另外,还发现探测器内n个电子的转移几率只受QPC与DQD耦合的影响.我们的结论可以为实验工作者研究电子输运特性提供理论参考. 相似文献
9.
用第一性原理研究了硼-碳和硼-氮量子点器件的输运特性以及电流电压特性.研究结果表明相同数量原子组成的硼-碳和硼-氮器件其输运特性及电流电压特性有很大差别.硼-碳器件在Fermi能附近有较大的态密度,而硼-氮器件的能级在Fermi能附近有很大的间隙,Fermi能位于间隙中.从电流特性中可以看出,硼-碳器件表现出导体的特性,而硼-氮器件表现出半导体的特性. 相似文献
10.
量子点太阳电池现已成为极具潜力的“第三代” 光伏器件, 其优点体现在材料成本低廉, 制备工艺简便, 以及其敏化剂特有的多激子效应(MEG) 潜能和吸光范围可方便调节等方面. 但是与染料分子敏化剂相比, 量子点敏化剂粒径更大、表面缺乏具有与TiO2结合的官能团, 这导致其在TiO2介孔中渗透阻力大、难以在TiO2表面吸附沉积, 所以量子点沉积手段在电池组装过程中尤为重要. 本文综述了电池组装过程中量子点的沉积方法, 分类阐述了直接生长量子点方法: 化学浴沉积(CBD)和连续离子层吸附生长(SILAR), 以及采用预先合成量子点的沉积方法: 连接分子辅助法(LA)、直接吸附法(DA)和电泳沉积(EPD)方法, 陈述了各沉积方法的发展过程及相应电池性能的改善, 对比了这些沉积方法的优缺点. 突出介绍了预先合成量子点的沉积方法, 特别是近年来不断优化而凸显优势的连接分子辅助法(LA). 总结了此方法快速、均匀沉积以及实现器件高性能的特点, 介绍了此方法沉积表面缺陷更少、结构更完善、材料更“绿色化”的量子点敏化剂的最新研究成果. 相似文献
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12.
应用非平衡格林函数方法,研究了带有微波调制的侧向耦合量子点的量子线中的光辅助隧穿.在考虑了量子干涉和微波场的情况下,得出并讨论了电子传榆幅度和相位方面的信息.电子传输幅度显示出一系列的反共振峰(对应图中的谷结构).峰值的高度与振荡的微波场的幅度和频率有关,而峰的位置只与微波场的频率有关.在有限温的情况下,反共振峰值的高度随着温度的增加而减小,当温度足够高时,反共振峰会消失,特别地,在一定的温度下,低温下谷的地方会演变成峰. 相似文献
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14.
The problem of bound polarons in quantum dot quantum well (QDQW)
structures is studied theoretically. The eigenfrequencies of bulk
longitudinal optical (LO) and surface optical (SO) modes are derived
in the framework of the dielectric continuum approximation. The
electron--phonon interaction Hamiltonian for QDQW structures is
obtained and the exchange interaction between impurity and
LO-phonons is discussed. The binding energy and the trapping energy
of the bound polaron in CdS/HgS QDQW structures are calculated. The
numerical results reveal that there exist three branches of
eigenfrequencies of surface optical vibration in the CdS/HgS QDQW
structure. It is also shown that the binding energy and the trapping
energy increase as the inner radius of the QDQW structure decreases,
with the outer radius fixed, and the trapping energy takes a major
part of the binding energy when the inner radius is very small. 相似文献
15.
T. Kuroda S. Sanguinetti F. Minami K. Watanabe N. Koguchi 《Superlattices and Microstructures》2002,32(4-6)
The relaxation dynamics of a multiple exciton complex (multiexciton) confined in a semiconductor quantum dot has been investigated. Emission signals from a single self-organized GaAs/Al0.3Ga0.7As quantum dot are temporally resolved with picosecond time resolution. The emission spectra consisting of the multiexciton structures are observed to depend on the delay time and the excitation intensity. Quantitative agreement is found between the experimental data and the calculation based on a model describing the successive relaxation of multiexcitons. 相似文献
16.
以CdSe纳米晶体为核,用胶体化学的方法,通过化学替代反应,获得了不同阱层或不同垒层的CdSeHgSeCdSe量子点量子阱(QDQW)晶体.紫外可见光吸收谱研究表明,通过调节QDQW中间HgSe阱层的厚度从0.9nm至0,可以调节QDQW颗粒的带隙从1.8变化至2.1eV,实现QDQW纳米晶体的剪裁.光致荧光(PL)谱研究显示,QDQW形成后,CdSeHgSe纳米颗粒表面态得到钝化,显现出发光强度加强的带边荧光峰.利用有效质量近似模型,对QDQW晶粒内部电子的1s—1s态进行了估算,估算结果总体趋势与实验数据相符
关键词:
量子点量子阱晶体 能带剪裁 加强的带边荧光峰 相似文献
17.
In this paper, an exciton trapped by a Gaussian confining potential quantum
dot has been investigated. Calculations are made by using the method of
numerical diagonalization of Hamiltonian in the effective-mass
approximation. The dependences of binding energies of the ground state and
the first excited state on the size of the confining potential and the
strength of the magnetic field are analysed explicitly. 相似文献
18.
This paper calculates the time evolution of the quantum mechanical
state of an electron by using variational method of Pekar type on
the condition of electric--LO-phonon strong coupling in a parabolic
quantum dot. It obtains the eigenenergies of the ground state and
the first-excited state, the eigenfunctions of the ground state and
the first-excited state This system in a quantum dot may be employed
as a two-level quantum system qubit. The superposition state
electron density oscillates in the quantum dot with a period when
the electron is in the superposition state of the ground and the
first-excited state. It studies the influence of the electric field
on the eigenenergies of the ground state, the first-excited state
and the period of oscillation at the different electron--LO-phonon
coupling constant and the different confinement length. 相似文献
19.
This paper investigates the electronic transport properties in an
Aharonov--Bohm interferometer with a quantum dot coupling to left and
right electrodes. By employing cluster expansions, it transforms the equations of
motion of Green's functions into the corresponding
equation of motion of connected Green's functions, which provides a
natural and uniform truncation scheme. With this method under the
Lacroix's truncation approximation, it shows that the asymmetric line
shape of zero bias conductance manifests itself as the Fano effect,
and the Kondo effect has been observed in the narrow peak of
differential conductance curve of the system. Our numerical results
also show that the building of Fano state suppresses the amplitude
of Kondo resonance. 相似文献
20.
There are some disadvantages to Nikolopoulos et al.'s protocol [Nikolopoulos G M, Petrosyan D and Lambropoulos P 2004 Europhys. Lett. 65 297] where a quantum dot system is used to realize quantum communication. To overcome these disadvantages, we propose a protocol that uses a quantum dot array to construct a four-qubit spin chain to realize perfect quantum state transfer (PQST). First, we calculate the interaction relation for PQST in the spin chain. Second, we review the interaction between the quantum dots in the Heitler-London approach. Third, we present a detailed program for designing the proper parameters of a quantum dot array to realize PQST. 相似文献