Carbon nanotube based bolometer

The contacts of single carbon nanotubes and bundles of carbon nanotubes with superconducting and metallic electrodes are investigated in order to create bolometers and electron coolers. Tunneling contacts of the carbon nanotubes with aluminum electrodes are obtained. The current-voltage characteristics of junctions are analyzed for temperatures from room temperature to 300 mK. The resistance of individual nanotubes is primarily determined by defects and is too large for applications. The use of the bundles of carbon nanotubes makes it possible to considerably reduce the resistance of the bolometer, which is determined by a small number of conducting tubes with good tunneling contacts with the electrodes. The energy gap is equal to hundreds and tens of millivolt in the former and latter cases, respectively. Structures containing bundles of carbon nanotubes can be described in a model with a Schottky barrier. The samples with bundles of carbon nanotubes exhibit the bolometric response to external high-frequency radiation at a frequency of 110 GHz with an amplitude up to 100 μV and a temperature voltage response to 0.4 mV/K.     

Preparation of graphene/polyaniline-modified carbon nanotubes and their electrochemical properties in microbial fuel cell

Using chemical vapor deposition methods to prepare carbon nanotubes growing in situ on a carbon felt, graphene and polyaniline were applied to the carbon felt for modifying carbon nanotubes. Microbial fuel cell was constructed with graphene/polyaniline-modified carbon nanotubes as anode, graphite as cathode, and glucose solution as substrate. The effects of electrodes, substrate concentration, and temperature on the properties of microbial fuel cell have been studied. At 38 °C using glucose solution of 1450 mg L^?1 and external resistance of 2500 Ω, the optimum output voltage of 687 mV and removal rate of 83% for chemical oxygen demand were obtained in the microbial fuel cell. The prepared nanomaterials are stable and reusable.     

Fabrication of a carbon nanotube device using a patterned electrode and a local electric field

Suspensions of carbon nanotubes (CNTs) and organic solvent were dropped onto a substrate which had patterned electrodes while applying a DC voltage between the electrodes. Both multiwall and single-wall (SW) CNTs were purified from the mixture of CNTs and the undesirable particles of carbon when the solvent dichloromethane was used at high temperature. It is found that a SW CNT bridges the gap of the electrodes. This enables us to fabricate CNT devices at a controlled position.     

Simple and accurate model for voltage-dependent resistance of metallic carbon nanotube interconnects: An ab initio study

In this work, development of a voltage dependent resistance model for metallic carbon nanotubes is aimed. Firstly, the resistance of metallic carbon nanotube interconnects are obtained from ab initio simulations and then the voltage dependence of the resistance is modeled through regression. Self-consistent non-equilibrium Green's function formalism combined with density functional theory is used for calculating the voltage dependent resistance of metallic carbon nanotubes. It is shown that voltage dependent resistances of carbon nanotubes can be accurately modeled as a polynomial function which enables rapid integration of carbon nanotube interconnect models into electronic design automation tools.     

Conductance noise investigations with four arbitrarily shaped and placed electrodes

A general relation is derived for the spectral noise density of the voltage between two arbitrarily shaped and placed sensor electrodes on a conductor, when a constant current or voltage is applied to another pair of arbitrarily shaped and placed driver electrodes. The general relation is based on the sensitivity calculation in linear electrical networks. The relation is elaborated for conductivity fluctuations due to 1/f noise by using empirical 1/f noise relations. The influence of spot radii of the sensor electrodes on the noise is demonstrated. The theoretical results for 2 and 3-dimensional conductors are in agreement with our experimental results for carbon resistance sheets and on silicon and germanium in the resistivity range of 1Ωcm to 400Ωcm. The possibility of using the four-point probe for measuring the fluctuations in the resistivity has been demonstrated.     

Conductance of bulk samples of multiwall carbon nanotubes-metal junctions

Conductance as a function of voltage and temperature was measured in junctions made of bulk samples of multiwall carbon nanotubes and metal electrodes. A clear zero bias anomaly was observed at low temperatures. The experimental results were analyzed within existing models based on Luttinger liquid and disorder theories. We find that our results are well explained using the quasi-one-dimensional disordered model.     

Vertical assembly of carbon nanotubes for via interconnects

The via interconnects are key components in ultra-large scale integrated circuits(ULSI).This paper deals with a new method to create single-walled carbon nanotubes(SWNTs) via interconnects using alternating dielectrophoresis(DEP).Carbon nanotubes are vertically assembled in the microscale via-holes successfully at room temperature under ambient condition.The electrical evaluation of the SWNT vias reveals that our DEP assembly technique is highly reliable and the success rate of assembly can be as high as 90%.We also propose and test possible approaches to reducing the contact resistance between CNT vias and metal electrodes.     

Selective growth of single-wall carbon nanotubes and the fabrication of devices on their basis

Single-wall carbon nanotubes were synthesized on specified parts of oxidized silicon substrates by single acetylene burst CVD and studied with high-resolution scanning electron and scanning probe micro-scopes. The resistance of individual nanotubes and nanotube series was measured using devices fabricated by the deposition of Pd and Pd/Al electrodes on the obtained single-wall nanotubes. The contact potential difference between Pd electrodes and carbon nanotubes was measured in the Kelvin mode of a scanning probe microscope.     

Superconducting properties of carbon nanotubes

Metallic single wall carbon nanotubes have attracted much interest as 1D quantum wires combining a low carrier density and a high mobility. It was believed for a long time that low temperature transport was exclusively dominated by the existence of unscreened Coulomb interactions leading to an insulating behavior at low temperature. However experiments have also shown evidence of superconductivity in carbon nanotubes. We distinguish two fundamentally different physical situations. When carbon nanotubes are connected to superconducting electrodes, they exhibit proximity induced superconductivity with supercurrents which strongly depend on the transmission of the electrodes. On the other hand intrinsic superconductivity was also observed in suspended ropes of carbon nanotubes and recently in doped individual tubes. These experiments indicate the presence of attractive interactions in carbon nanotubes which overcome Coulomb repulsion at low temperature, and enables investigation of superconductivity in a 1D limit never explored before. To cite this article: M. Ferrier et al., C. R. Physique 10 (2009).     

真空热处理碳纳米管的储氢性能研究

研究了真空热处理对多壁碳纳米管(MWNTs)电化学储氢性能的影响.采用化学气相沉积法(CVD)制备碳纳米管，碳纳米管与LaNi₅储氢合金按质量比1∶10混合，制作成CNTs-LaNi₅电极.电解池采用三电极体系，6mol/L KOH为电解液，Ni(OH)₂为正极，Hg/HgO为参比电极.实验结果表明，在相同的充放电条件下，850℃时CNTs-LaNi₅电极的储氢性能最好，克容量最大为503.6mAh/g，相应的平台电压高达1.18V.从500—850℃随着温度升高，放电量有较大幅度的增加，但到950℃时放电量反而下降.由此可见，碳纳米管的热处理温度对碳纳米管的电化学储氢性能有着较大的影响. 关键词： 碳纳米管(CNTs) 储氢性能 5合金')" href="#">LaNi₅合金 化学气相沉积法(CVD法)     

一种平行栅碳纳米管阵列阴极的场发射特性研究

建立一种平行栅碳纳米管阵列阴极,利用悬浮球模型和镜像电荷法进行计算,给出碳纳米管顶端表面电场与电场增强因子的解析式. 在此基础上,进一步分析器件各类参数以及接触电阻对阴极电子发射性能的影响. 分析表明,碳纳米管间距大约为2倍碳纳米管高度时阵列阴极的分布密度最佳,靠边缘部位的碳纳米管发射电子能力比其中心部位的大;除碳纳米管的长径比之外,栅极宽度和栅极间距也对电场增强因子有一定作用;接触电阻的存在大幅度降低碳纳米管顶端表面电场与发射电流,而接触电阻高于800 kΩ时,器件对阳极驱动电压的要求更高. 关键词： 平行栅碳纳米管阵列 悬浮球 场增强因子 接触电阻     

Nonlinear resistance of polymer composites with carbon nanotube additives in the percolation state

The electrical properties of a polymer composite with carbon nanotube additives have been analyzed. The state of the system near the percolation threshold, when charge is transferred along a single percolation path, has been considered. For this state, the current–voltage characteristics of a percolation chain made up of carbon nanotubes have been calculated under the assumption that the contact resistance between neighboring nanotubes is much higher than the intrinsic resistance of the nanotubes. According to recent data, the distance between neighboring (contacting) nanotubes has been assumed to be randomly distributed. It has been shown that, under the given conditions, the current–voltage characteristic is essentially nonlinear. This indicates the nonohmic conductivity of the composites. The dependence of the current–voltage characteristic on the spread of the contact distribution over distances has been discussed.     

Nonmonotonic behavior of resistance in a superconductor-Luttinger liquid junction

Transport through a superconductor-Luttinger liquid junction is considered. When the interaction in the Luttinger liquid is repulsive, the resistance of the junction with a sufficiently clean interface shows nonmonotonic temperature or voltage dependence due to the competition between the superconductivity and the repulsive interaction. The result is discussed in connection with recent experiments on single-wall carbon nanotubes in contact with superconducting leads.     

Negative differential resistance in ZnO coated peptide nanotube

We investigate the room temperature electronic transport properties of a zinc oxide (ZnO) coated peptide nanotube contacted with Au electrodes. Current–voltage (I–V) characteristics show asymmetric negative differential resistance (NDR) behavior along with current rectification. The NDR phenomenon is observed in both negative and positive voltage sweep scans, and found to be dependent on the scan rate and humidity. Our results suggest that the NDR is due to protonic conduction arising from water molecule redox reaction on the surface of ZnO coated peptide nanotubes rather than the conventional resonant tunneling mechanism.     

碳纳米管在高压下的电学性质与状态方程

 在金刚石压砧装置上，采用电阻测量方法研究了多层碳纳米管在室温下、23 GPa内的电阻与压力的关系。实验结果表明，在1.5～4.6 GPa内，电阻急剧减小，而在5.7 GPa左右，电阻出现一个极大值。这些变化与碳纳米管的结构、形状和层间距离的变化有关。同时，还在活塞-圆筒式p-V关系测量装置上首次研究了多层碳纳米管在室温下、4.5 GPa内的p-V关系，给出了它在第一次和第七次压缩时的状态方程。     

Fabrication and electrical properties of a carbon nanotube quantum dot

Single-walled carbon nanotubes (SWNTs) were synthesized by pyrolyzing methane (CH₄) at a temperature of 900℃ on SiO₂ substrates pre-coated with iron nano-particles. Electrical contacts were fabricated onto one of the SWNTs by using an electron beam lithography process. Coulomb blockade and single-electron tunnelling characters were found at low temperatures, indicating that the SWNT in-between the electrodes forms a quantum dot. It is found that the Coulomb gap of the quantum dot is about 8.57 meV, and the factor \alpha , which converts the gate voltage to the true electrostatic potential shift, is around 200 for this device.     

Ferritin-mixed solution plasma system yielding low-dimensional carbon nanomaterials and their application to flexible conductive paper

We demonstrate the production of low-dimensional carbon nanomaterials using a solution plasma system and their application to flexible conductive paper. The solution plasma system consists of two graphite electrodes and a beaker filled with ferritin-mixed deionized water. Ferritin molecules are used as the growth catalyst of the carbon nanomaterials. A high voltage of 15 kV at a frequency of 25 kHz is supplied to the electrodes using an alternating-current power source. The effects of the graphite rod diameters and the concentration of ferritin molecules are comparatively investigated. The produced carbon nanomaterials are characterized using Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. We confirmed the synthesis of graphitic platelets, onion-like structures, and carbon nanotubes. Finally, we fabricated flexible conductive papers using the produced materials with a good electrical conductance.     

碳纳米管熔接金电极的分子动力学模拟

利用分子动力学模拟方法,研究了单壁碳纳米管与Au电极的高温熔接. 模拟结果表明,用端口吸附了Au团簇的碳纳米管在高温下能很好地与Au电极熔接. 首先将Au团簇放置于碳纳米管开口处进行高温退火,退火温度在1100 K左右,Au团簇部分Au原子进入碳纳米管管内,吸入碳纳米管中的Au原子形成壳层螺旋结构的Au纳米线,管外Au团簇呈无定形结构. 然后将吸附了Au团簇的碳纳米管与Au电极进行熔接,高温退火后,碳纳米管与Au电极表面之间形成了稳固的熔接,熔接最佳温度在800 K左右. 关键词： 碳纳米管 金电极 分子动力学模拟     

Sample-specific and ensemble-averaged magnetoconductance of individual single-wall carbon nanotubes

We discuss magnetotransport measurements on individual single-wall carbon nanotubes (SWNTs) with low contact resistance, performed as a function of temperature and gate voltage. We find that the application of a magnetic field perpendicular to the tube axis results in a large magnetoconductance of the order of e2/h at low temperature. We demonstrate that this magnetoconductance consists of a sample-specific and of an ensemble-averaged contribution, both of which decrease with increasing temperature. The observed behavior resembles very closely the behavior of more conventional multichannel mesoscopic wires, exhibiting universal conductance fluctuations and weak localization. A theoretical analysis of our experiments will enable us to reach a deeper understanding of phase-coherent one-dimensional electronic motion in SWNTs.