掺硼锯齿型单壁碳纳米管的电子结构

为了研究掺硼碳纳米管的电子结构,对可能存在掺杂方式进行了结构优化,得到掺硼碳纳米管最可能的存在结构.采用密度泛函理论下的第一性原理计算,对不同掺杂浓度的最可能存在掺杂结构进行了计算,结果表明随着掺杂浓度的增加碳纳米管的能带间隙呈现增大的趋势.     

碳纳米管超晶格结构能隙的第一性原理研究

本文采用基于密度泛函理论的CASTEP模块研究了B/N共掺(5,5)碳纳米管环超晶格的电子结构。形成能计算结果为负值表明,B/N原子对共掺碳纳米管环具有稳定存在的可能性。能带结构和态密度结果表明,B/N原子对的掺入使得(5,5)金属型碳纳米管能隙打开,导电性质向半导体转变。当管径在合理的变化范围内,纯碳纳米管的能隙宽度强烈敏感于管径的变化,而B/N共掺碳纳米管环结构的能隙值随管径的变化较小,这就降低了碳纳米管电子器件的制备要求。对新型结构施加变形作用,压缩变形使得B/N共掺碳纳米管环的能带宽度增大,这相当于提高了碳纳米管的掺杂体积浓度;拉伸变形作用下所得结论恰恰相反。实现控制碳纳米管超晶格结构的导电性能,对纳米管电子器件的应用具有重要意义。     

(111)方向的InAs/GaSb超晶格材料电子结构的杂化泛函计算

采用电子密度泛函理论方法计算了一系列（111）方向的InAs/GaSb超晶格的电子结构和能带结构。将杂化泛函的计算结果与普通密度泛函方法的计算结果进行了比较。Heyd-Scuseria-Ernzerhof (HSE)杂化与对固体修正的Perdew-Burke-Ernzerhof (PBE)近似结合的杂化泛函显示了较传统PBE方法和若干其他杂化泛函更符合实验数据的结果。采用该方法研究了InAs/GaSb超晶格的带隙随超晶格周期厚度以及InAs/GaSb比例变化的规律。其结果与以往实验结果符合很好。这些结果表明HSE-PBEsol方法对于估计InAs/GaSb超晶格的电子性质适用。     

掺氮锯齿型单壁碳纳米管的电子结构

基于密度泛函理论(DFT)框架下的第一性原理平面波超软赝势方法,采用CASTEP软件包,在分析掺氮碳纳米管最可能存在方式并进行结构优化的基础上,对不同掺氮浓度的单壁碳纳米管的电子结构进行了计算,分析了掺杂碳纳米管的能带结构和态密度,结果表明随着掺杂浓度的增加能带间隙呈现减小的趋势.     

(111)方向的InAs/GaSb超晶格材料电子结构的杂化泛函计算（英文）

采用电子密度泛函理论方法计算了一系列(111)方向的InAs/GaSb超晶格的电子结构和能带结构.将杂化泛函的计算结果与普通密度泛函方法的计算结果进行了比较.Heyd-Scuseria-Ernzerhof(HSE)杂化与对固体修正的Perdew-Burke-Ernzerhof(PBE)近似结合的杂化泛函显示了较传统PBE方法和若干其他杂化泛函更符合实验数据的结果.采用该方法研究了InAs/GaSb超晶格的带隙随超晶格周期厚度以及InAs/GaSb比例变化的规律.其结果与以往实验结果符合很好.这些结果表明HSE-PBEsol方法对于估计InAs/GaSb超晶格的电子性质适用.     

掺氮锯齿型单壁碳纳米管的电子结构

基于密度泛函理论(DFT)框架下的第一性原理平面波超软赝势方法,采用CASTEP软件包,在分析掺氮碳纳米管最可能存在方式并进行结构优化的基础上,对不同掺氮浓度的单壁碳纳米管的电子结构进行了计算,分析了掺杂碳纳米管的能带结构和态密度,结果表明随着掺杂浓度的增加能带间隙呈现减小的趋势.     

氮掺杂对单壁碳纳米管的非平衡电子输运特性的影响

利用结合了非平衡格林函数的第一性原理的局域密度泛函理论,研究了氮原子取代掺杂单壁碳纳米管的输运特性.计算结果表明,不同构形和不同数目的氮原子掺杂对(8,0)单壁碳管的输运性能有复杂的影响.研究发现,氮原子的掺杂提高了半导体型碳管的输运性能,电流-电压曲线呈非线性变化.对于浓度相同的氮掺杂,原胞内最近邻氮原子间距极大地影响了碳管的输运性能.因此,基于掺杂管的分子器件的设计中很有必要考虑这些因素.     

氮掺杂对单壁碳纳米管的非平衡电子输运特性的影响

利用结合了非平衡格林函数的第一性原理的局域密度泛函理论,研究了氮原子取代掺杂单壁碳纳米管的输运特性.计算结果表明,不同构形和不同数目的氮原子掺杂对(8,0)单壁碳管的输运性能有复杂的影响.研究发现,氮原子的掺杂提高了半导体型碳管的输运性能,电流-电压曲线呈非线性变化.对于浓度相同的氮掺杂,原胞内最近邻氮原子间距极大地影响了碳管的输运性能.因此,基于掺杂管的分子器件的设计中很有必要考虑这些因素.     

碳纳米管的电子能带结构和态密度研究

为了研究单壁碳纳米管的电子能带特性及其态密度,本文采用紧束缚法和态密度函数,对无限长碳纳米管进行了理论计算和模拟。结果表明:碳纳米管的电子能带结构与其几何结构密切相关,一般认为扶手型管呈现出金属性;而锯齿管则不同,当n=3k(k为整数)时,其能级存在一个较小的禁带宽度,具有半金属性质;而其它锯齿型管均存在较大的禁带宽度,且禁带宽度随管径的增大而减小,具有半导体性质,这为碳纳米管的电子结构的研究提供了必要且有价值的理论依据。     

C掺杂金红石结构TiO2的第一性原理研究

利用基于密度泛函的第一性原理研究了非磁性轻元素C掺杂金红石TiO2的性质,这在自旋电子和红外电子领域具有潜在的应用前景.结果显示：C原子更倾向于形成铁磁耦合并围绕在Ti原子周围,每个C原子的磁矩大约为1.3 μB.体系的铁磁性来源于p-d轨道杂化和类p-d杂化的p-p耦合共同作用,p-p耦合主要来自类p-t2g 和价带p态耦合.     

Characterization of Geoinspired and Synthetic Chrysotile Nanotubes by Atomic Force Microscopy and Transmission Electron Microscopy

Geoinspired synthetic chrysotile nanotubes both stoichiometric and 0.67 wt % Fe doped were characterized by transmission electron microscopy and electron diffraction. Bending tests of the synthetic chrysotile nanotubes were performed using the atomic force microscope. The nanotubes were found to exhibit elastic behaviour at small deformations (below ca. 20 nm). Young's modulus values of (159 ± 125) GPa and (279 ± 260) GPa were obtained from the force‐deflection curves using the bending equation for a clamped beam under a concentrated load, for the stoichiometric and the Fe doped chrysotile nanotubes, respectively. The structural modifications induced by Fe doping altered the mechanical properties, with an apparent dependence of the latter on the number of constituting walls of the nanotubes.     

Cavity Quantum Electrodynamics,Nanophotonics, and Quantum Communication with Atomically Doped Carbon Nanotubes

The latest theoretical studies of the near-field electrodynamic properties of atomically doped carbon nanotubes are reviewed. It has been shown that, similar to semiconductor microcavities and photonic band-gap materials, carbon nanotubes may qualitatively change the character of the atom–electromagnetic-field interactions, yielding strong atom–field coupling and the formation of quasi-one-dimensional atomic polariton states. A scheme for entangling such polaritons has been considered, and small-diameter metallic nanotubes have been shown to result in sizable amounts of the two-quantum bit (qubit) atomic entanglement with no damping for sufficiently long times. This challenges novel applications of atomically doped carbon nanotubes in quantum information science.     

Significantly Enhanced Photoluminescence of Doped Polymer‐Metal Hybrid Nanotubes

We report on the significantly enhanced photoluminescence (PL) of hybrid double‐layered nanotubes (HDLNTs) consisting of poly(3‐methylthiophene) (P3MT) nanotubes with various doping levels enveloped by an inorganic, nickel (Ni) metal nanotube. From laser confocal microscopy PL experiments on a single strand of the doped‐P3MT nanotubes and of their HDLNTs, the PL peak intensity of the HDLNT systems increased remarkably up to ～350 times as the doping level of the P3MT nanotubes of the HDLNTs increased, which was confirmed by measurements of the quantum yield. In a comparison of the normalized ultraviolet and visible absorption spectra of the doped‐P3MT nanotubes and their HDLNTs, new absorption peaks corresponding to surface‐plasmon (SP) energy were created at 563 and 615 nm after the nanoscale Ni metal coating onto the P3MT nanotubes, and their intensity increased on increasing the doping level of the P3MT nanotube. The doping‐induced bipolaron peaks of the HDLNTs of doped‐P3MT/Ni were relatively reduced, compared with those of the doped‐P3MT nanotubes before the Ni coating, due to the charge‐transfer effect in the SP‐resonance (SPR) coupling. Both energy‐transfer and charge‐transfer effects due to SP resonance contributed to the very‐large enhancement of the PL efficiency of the doped‐P3MT‐based HDLNTs.     

Influence of tension-twisting deformations and defects on optical and electrical properties of B, N doped carbon nanotube superlattices

As the era of nanoelectronics is dawning, CNT (carbon nanotube), a one-dimensional nano material with outstanding properties and performances, has aroused wide attention. In order to study its optical and electrical properties, this paper has researched the influence of tension-twisting deformation, defects, and mixed type on the electronic structure and optical properties of the armchair carbon nanotube superlattices doped cyclic alternately with B and N by using the first-principle method. Our findings show that if tension-twisting deformation is conducted, then the geometric structure, bond length, binding energy, band gap and optical properties of B, N doped carbon nanotube superlattices with defects and mixed type will be influenced. As the degree of exerted tension-twisting deformation increases, B, N doped carbon nanotube superlattices become less stable, and B, N doped carbon nanotube superlattices with defects are more stable than that with exerted tension-twisting deformations. Proper tension-twisting deformation can adjust the energy gap of the system; defects can only reduce the energy gap, enhancing the system metallicity; while the mixed type of 5% tension, twisting angle of 15° and atomic defects will significantly increase the energy gap of the system. From the perspective of optical properties, doped carbon nanotubes may transform the system from metallicity into semi-conductivity.     

Templating Synthesis of SnO2 Nanotubes Loaded with Ag2O Nanoparticles and Their Enhanced Gas Sensing Properties

A new kind of SnO₂ nanotubes loaded with Ag₂O nanoparticles can be synthesized by using Ag@C coaxial nanocables as sacrificial templates. The composition of silver in SnO₂ nanotubes can be controlled by tuning the compositions of metallic Ag in Ag@C sacrificial templates, and the morphology of tubular structures can be changed by use of nanocables with different thicknesses of carbonaceous layer. This simple strategy is expected to be extended for the fabrication of similar metal‐oxide doped nanotubes using different nanocable templates. In contrast to SnO₂@Ag@C nanocables as well as to other types of SnO₂ reported previously, the Ag₂O‐doped SnO₂ nanotubes exhibit excellent gas sensing behaviors. The dynamic transients of the sensors demonstrated both their ultra‐fast response (1–2 s) and ultra‐fast recovery (2–4 s) towards ethanol, and response (1–4 s) and recovery (4–5 s) towards butanone. The combination of SnO₂ tubular structure and catalytic activity of Ag₂O dopants gives a very attractive sensing behavior for applications as real‐time monitoring gas sensors with ultra‐fast responding and recovering speed.     

Current–Voltage Characteristics of Two-Electrode Elements with Carbon Nanotubes

Planar two-electrode nonlinear elements using carbon nanotubes doped with platinum metals are created and investigated. Among the nanotubes, branched ones are found. If doped, these nanotubes take a regular form. With appropriate doping, limiting currents above 1 A are achieved. However, the problem of contact between carbon nanotubes and electrodes has yet to be solved.     

Mn-Zn铁氧体掺杂与结构-性能的研究进展

Mn-Zn铁氧体以其高磁导率、低损耗和低矫顽力等特点,在功能器件中具有潜在的应用前景.介绍了基本配方对Mn-Zn铁氧体的相组成及电磁性能的影响,综述了近年来不同添加剂掺杂对Mn-Zn铁氧体材料性能的影响,并就掺杂Mn-Zn铁氧体材料的相组成、结构和磁性能之间的关系进行了讨论,对该领域研究的发展趋势给予了展望.     

掺杂单壁碳纳米管的电流特性

依据Boltzmann方程及单壁碳纳米管(SWNTs)能量色散关系,对单个掺杂SWNTs(金属型和半导体型)所加偏压、掺杂浓度及管口直径影响输运电流的性质进行数值计算.分析表明,掺杂SWNs中的电流随偏压变化呈现跃变结构;管口直径、掺杂后Fermi能级附近的态密度以及各通道输运电子的能力直接决定电流的特性,如电流强度、跃变间隔及跃变幅度;同时电流的特性也与温度有关.     

Low-Temperature Synthesis of Fe-Doped ZnO Nanotubes

We report on the synthesis Zn_1?x Fe _x O nanotubes with average tube diameter of 60?nm to 100?nm and wall thickness of about 20?nm. The nanotubes were synthesized by a low-temperature electrochemical process, and their morphology was found to be sensitive to the electrolyte concentration and growth time. The maximum Fe doping achieved by this process was estimated to be approximately 4?wt.%. High-resolution transmission electron microscopy and x-ray diffraction showed good crystalline quality of the doped and undoped nanotubes with preferential growth along the wurtzite c-axis. The Fe-doped nanotubes exhibit wurtzite crystal structure with an increase in the c-axis lattice constant when compared with the undoped nanotubes, indicative of the fact that Fe ions substitute for Zn as 2+ ions in the ZnO crystal lattice. Further evidence of Fe as a substitutional dopant is provided by Raman and photoluminescence spectroscopy. A comparison of the effective magnetic moment in the undoped and doped nanotubes reveals the presence of four unpaired electrons in the Fe-doped sample and zero unpaired electrons for the undoped sample.