Magneto transport characterization of the Sn-doped TbMnO3 manganites

The structural, magnetic and electrical transport properties of the Sn-doped TbMnO3 manganites are studied by X-ray diffraction, ac susceptibility, dc magnetization and electrical resistivity measurements. The Sn doping into the Tb and Mn sites of TbMnO3 compresses the unit cell and changes parameters of the antiferromagnetic phase whereas the magnetic moment of Mn are only weakly affected. The electrical resistivity of doped manganites is reduced and the activation energy EA is determined for the thermally activated conduction. © 2007 Elsevier B.V. All rights reserved.

Self-similar organization of arrays of individual carbon nanotubes and carbon nanotube micropillars

It is well-known that carbon nanotube (CNT) growth from a dense arrangement of catalyst nanoparticles creates a vertically aligned CNT forest. CNT forests offer attractive anisotropic mechanical, thermal, and electrical properties, and their anisotropic structure is enabled by the self-organization of a large number of CNTs. This process is governed by individual CNT diameter, spacing, and the CNT-to-CNT interaction. However, little information is known about the self-organization of CNTs within a forest. Insight into the self-organization is, however, essential for tailoring the properties of the CNT forests for applications such as electrical interconnects, thermal interfaces, dry adhesives and energy storage. We demonstrate that arrays of CNT micropillars having micron-scale diameters organize in a similar manner as individual CNTs within a forest. For example, as previously demonstrated for individual CNTs within a forest, entanglement of small-diameter CNT micropillars during the initial stage of growth creates a film of entwined pillars. This layer enables coordinated subsequent growth of the pillars in the vertical direction, in a case where isolated pillars would not grow in a self-supporting fashion. Finally, we provide a detailed overview of the self-organization as a function of the diameter, length and spacing of the CNT pillars. This study, which is applicable to many one-dimensional nanostructured films, demonstrates guidelines for tailoring the self-organization which can enable control of the collective mechanical, electrical and interfacial properties of the films. © 2009 Elsevier B.V. All rights reserved.

A method for individual identification of echolocation signals in free-ranging finless porpoises carrying data loggers

Echolocation click events of a free-ranging juvenile and an adult finless porpoise (Neophocaena phocaenoides) were recorded with an acoustic data logger. Additionally, dive depth and swim speed of the juvenile were recorded with a behavior data logger. Echoes of echolocation signals from the water surface were clearly detected in shallow dives approximately less than 2 m. The delay time between a surface echo and a direct signal corresponded with the two-way transmission time for the animal's depth, indicating that the signals originated from the animal wearing the data loggers. The finless porpoises produced echolocation signals frequently and were thought to be able to detect their depth by listening to echoes from the water surface. (C) 2000 Acoustical Society of America. [S0001-4966(00)01609-X].

In(Ti,Sn)-O 与Sn(Pb)Zn-Te 的电子结构研究

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Raman scattering from an individual tubular graphite cone

　

Determination of the interdiffusion coefficients of liquid Zn and Sn using Ta/Zn-Sn/Si trilayers

In this paper we present a new method for measuring diffusion coefficients in liquid metals under convection-less conditions with solid/liquid-liquid/solid trilayer. The advantage of this kind of trilayer is that effects from gravity-induced convection and Marangoni-convection can be omitted, so that the diffusion coefficient is determined more accurately. The Ta/Zn-Sn/Si trilayer were prepared with a multi-target ion-beam sputtering deposition technique and annealed in an electric furnace under an argon atmosphere. The interdiffusion of liquid zinc and tin at 500 degrees degree C was investigated. The diffusion concentration profiles were determined by energy dispersive spectroscopy. The interdiffusion coefficients range from 1.0x10(-6)cm(2)/s to 2.8x10(-6)cm(2)/s, which is less than previous values measured by capillary reservoir technique under 1g-environment where various convection exist. The precise interdiffusion coefficients of liquid zinc and tin result from the removing of disturbances of various kinds of convection.

Electrical transport through individual DNA molecules

A theoretical model is presented to describe electrical transport through individual DNA molecules. By contacting the proposed model with the experimentally measured data, a variety of valuable quantities are identified. The partially decoherent nature on the guanine-cytosine (GC) pairs of DNA is also elaborated in contrast to the completely incoherent hopping mechanism discussed in the context of charge transfer experiments. (C) 2001 American Institute of Physics.

Random telegraph noise in the photoluminescence of individual GaxIn1-xAs quantum dots in GaAs

We have investigated random telegraph noise in the photoluminescence from InGaAs quantum dots in GaAs. Dots switching among two and three levels have been measured. The experiments show that the switching InGaAs dots behave very similarly to switching InP dots in GaInP. but differently from the more commonly investigated colloidal dots. The switching is attributed to defects, and we show that the switching can be used as a monitor of the defect.

La-Ba-Cu-Sn-O钙钛矿型多元复合氧化物的制备、组成、结构、电学性质和气敏性质的研究

本文合成了LaBa_2Cu_(3-x)Sn_xO_(6.5) + x (x = 0.2; 0.5; 0.7; 1.0; 1.2; 1.5; 1.7; 2.0; 2.2; 2.5; 2.7; 3.0)系列，2aBaCu_(2-x)Sn_xO_(4.5) + x (x = 0; 0.2; 0.5; 0.7; 1.0; 1.2; 1.5; 1.7; 2.0)系列和La_3Cu_(3-x)Sn_xO_(7.5) + x (x = 0.5; 1.0; 1.5; 2.0; 2.2; 2.5; 2.7)系列等二十八个新复合氧化物。这三个系列二十八个新复合氧化物直至目前为止，文献上未见过报道。我们通过x-ray粉末衍射图分析了它们的结构，肯定了它们是新的单一化合物，计算了它们的晶胞参数并确定它们的所属晶系。元素化学分析表明，所有这些化合物均可用原始计算配比化学式表示。干湿两种合成方法所合成的结构相同。对于这三个系列二十八个瓣复合氧化物，我们选用LaBa_2-Cu_(3-x)Sn_xO_(6.5) = x (x = 0.5;1.0;1.5;2.0;2.5),LaBaCu_(2-x)Sn_xO_(4.5) = x(x = 0.5; 1.0; 1.5;2.0), La_3Cu_(3-x)Sn_xO_(7.5) + x (x = 0.5; 1.0; 1.5; 2.0; 2.5)等十四个化合物，对它们的低温，高温和高湿下的电阻率和导电类型进行了测试，绘得了它们的电阻率和温度的关系曲线。在一定温度下，一个系列内的化合物电阻率随锡的分子含量增加而增大。La_3Cu_(3-x)Sn_xO_(7.5) = x系统人物的电阻率明显大于其它二个系列相应化合物的电阻率。所有化合物在液氮至室温温区内，基本上呈半导体导电类型。在高温以上温区，当温度升至一定温度时之前，化合物呈本导体导电类型达到一定温度之后，当金属导电类型所有新复合氧化物在高温均属P型半导体。本文还研究了这三个系列化合物和将它们掺入二氧化锡中的气敏性能。结果表明：所有这类化合物和将它们掺入二氧化锡中作为添加剂做成的气敏材料，除LaBa_2Cu_(1.5)Sn_(1.5)O_8掺入SnO_2做成的气敏材料外，在本文实验条件下做成的气敏元件对氧化性和还原性气体均无或只有很差的气敏性。LaBa_2Cu_(1.5)Sn_(1.5)O_8作为添加剂掺入SnO_2中(摩尔比0.2:0.8; 0.1:0.9)所制得的气敏文件对高浓度(1%-10%)的一氧化碳，液化气和煤气具有很好的气敏线性响应，当加热电流为300mA时，酒精，汽油和石油醚等还原性气体基本上无干扰。实验表明当摩尔比为0.1:0.9时，材料的气敏性能最佳，但重现性较差，当摩尔比为0.2:0.8时，气敏性稍低，但重现性较好。本文还合成了La_xBa_(1-x)SnO_3(x = 0; 0.05; 0.10; 0.15, 0.20)系列化合物，并确定了它们的结构和所属晶系。从结构上分析我们认该系列化合物相互之间为置换固溶体。其晶胞参数随镧的加入量增加而减小。该系列均属几型半导体材料。我们利用该系列材料进行了过敏性研究。结果表明。由La_(0.1)Ba_(0.9)SnO_3制得的高热式气敏器件对低浓度酒精(<1000 ppm)有很好的气敏线性响应。在加热电流为250 mA时，基本上排除了煤气，一氧化碳，液化气和汽油等可燃性气体的干扰。但香烟烟雾对器件检测酒精有一定的影响。La_(0.1)Ba_(0.9)SnO_3气敏材料多添加1%而制得的器件，机械强度达到很好的效果，器件对酒精的灵敏度有降低，而响应浓度区间宽度增加近一倍，选择性几乎不变。该材料具有较好的实验重现性。该系列的其它化合物在本实验条件下所制得的器件对可燃性气体的敏感性较差。

Energy level analyses of even-parity J=1 and 2 Rydberg states of Sn I by multichannel quantum defect theory

This paper analyzes the energy levels along the even-parity J=1 and 2 Rydberg series of Sn I by multichannel quantum defect theory. A good agreement between theoretical and experimental energy levels was achieved. Below 59198 cm~(-1), a total of 85 and 23 new energy levels, respectively, in the J=1 and J=2 series, which cannot be measured previously by experiments, are predicted in this work. Based on the calculated admixture coefficients of each channel, interchannel interactions were discussed in detail. The results are helpful to understand the characteristics of configuration interaction among even-parity levels in Sn I.

掺Sn的In_20_3透明导电膜生长优先取向对其光电性能的影响

采用反应热蒸发法制备掺sn的In_20_3（ITO）透明导电膜，系统研究了ITO薄膜生长的优先取向对其光电性能的影响，结果表明，ITO薄膜（400）取向的优先生长对其透过率影响很小，但可明显增加载流子迁移率，从而有效降低了薄膜的方块电阻。在两个相同的薄膜硅／单晶硅太阳能电池上分别沉积（222）和（400）ITO优先取向膜，光电转换效率分别为10．3％和12．9％，表明（400）取向更有利于提高电池效率。经优化，最佳衬底温度（T_s）为225℃，最佳氧流量（fo_2）为4sccm。在优化的沉积条件下制备ITO薄膜，其电阻率可达到4.8x10~(-4)Ω·cm，可见波段的透过率大于90％，性能指数为3.8×10~(-2)□/Ω。

Observation of the resonant Raman behavior of individual single-walled carbon nanotubes

The different resonant Raman scattering process of single-walled carbon nanotubes (SWNTs) has been found between the Stokes and anti-Stokes sides of the radial breathing modes (RBMs), and this provides strong evidence that Raman spectra of some special diametric SWNTs are in resonance with their electronic transitions between the singularities in the one-dimensional electronic density of states in the valence and conduction bands, and other SWNTs axe beyond the resonant condition. Because of the coexistence of resonant and non-resonant Raman scattering processes for different diametric SWNTs, the relative intensity of each RBM does not reflect the proportion of a particular SWNT.