An Alternating-Current Voltage Modulated Thermal Probe Technique for Local Seebeck Coefficient Characterization

Nanostructured and nanocomposite thermoelec- tric materials have recently attracted a great deal of attention due to the optimization of thermal and electrical transports for high thermoelectric performance The initial ideas for the applica- tions of nano-structures in thermoelectric materials are that the lattice thermal conductivity can be de- pressed by the scattering of nano-particles or nano- boundaries as well as the enhanced electron density of states at the Fermi level. The latter is expected to enhance Seebeck coefficients due to the fact that the low energy carriers can be filtered by nano-sized grain boundaries. Lowered thermal conductivity and enhanced thermoelectric figure of merit have been ob- served in lots of bulk materials with nanostructures or nano-impurities. However, the thermal and electrical transports in these nano-materials are usually mea- sured by normal commercial systems, in which only the statistical values of the transports are obtained. The characterization of local thermoelectric parame- ters still remains a challenging task at the submicro, even nanometer level as a powerful tool for Scanning probe microscopy nanostructure imaging and local properties characterization, has become a promis- ing technique for measuring local thermal and electri- cal properties, like scanning tunneling microscopy, scanning thermal microscopy, and scanning Joule expansion microscopy. Recent work has demon- strated simultaneously determined the thermal con- ductivity and Seebeek coefficient of Bi2Se3 thin film by a microprobe technique.     

Single atomic manipulation and writing with scanning tunnelling microscopy at low temperatures

In the work reported in this paper,we have used a low-temperature scanning tunnelling microscope (LT-STM) system to manipulate accurately single atoms.We show how we can use a LT-STM to image and modify a bulk Ag(111) surface and manipulate Ag atoms from substrate and evaporated adsorbates on Ag(111) substrates.We present a synergistic combination of SM-induced modification and ordered arrays of nanometre-scale structures.In particular,we demonstrate the ability to modify Ag atomic nanometre structures on the Ag(111) substrate,and some English letters and a Chinese character can be written by single Ag atoms coming from the substrate and evaporated adsorbates on Ag(111),In this way ,we supply an effective basis to explore the fundamental physical properties of a nanometre structure and to develop nanotechnology with a bottom-up approach,     

快速测量单晶样品低温热电势的新方法

对传统的热电势倒相测量方法进行了改进,发展了一种快速的、针对毫米级样品的准连续的热电势测量方法,在不降低测量精度的情况下大幅度提高了热电势的测量速度.我们用高温超导材料Nd1.84Ce0.16CuO4单晶样品对该法进行了不同变温速率的测试,并与传统的倒相法进行比较,一定变温速率(<30K/hr)下和传统方法数据吻合很好,有很高的测量精度.由于此法为准连续测量法,变温速率可精确设定,所以对有明显热滞效应的材料如电子型超导体母体材料Nd2CuO4等的热电势测量有十分重要的意义.     

热电材料研究进展

在介绍热电材料制冷工作原理,分析热电材料优值系数的基础上,介绍了300K以下热电材料的研究进展,以及热电材料制冷特点、现状和应用前景．     

STM灵敏度系数的校正

讨论了隧道扫描显微镜（ＳＴＭ）中压电陶瓷压电系数的测量计算及高定向裂解石墨（ＨＯＰＧ）的ＳＴＭ相象。这对ＳＴＭ图象的分析有着重要的作用。     

石墨烯-六方氮化硼面内异质结构的扫描隧道显微学研究

石墨烯-六方氮化硼面内异质结构因可调控石墨烯的能带结构而受到广泛关注. 本文介绍了在超高真空体系内, 利用两步生长法在两类对石墨烯分别有强和弱电子掺杂的基底, 即Rh(111)和Ir(111)上制备石墨烯-六方氮化硼单原子层异质结构. 通过扫描隧道显微镜及扫描隧道谱对这两种材料的形貌和电子结构进行研究发现: 石墨烯和六方氮化硼倾向于拼接生长形成单层的异质结构, 而非形成各自分立的畴区; 在拼接边界处, 石墨烯和六方氮化硼原子结构连续无缺陷; 拼接边界多为锯齿形型, 该实验结果与密度泛函理论计算结果相符合; 拼接界面处的石墨烯和六方氮化硼分别具有各自本征的电子结构, 六方氮化硼对石墨烯未产生电子掺杂效应.     

热电材料室温下塞贝克系数测试装置的研制

提出一种测试热电材料室温下塞贝克系数的有效方法并搭建了其测试装置。该测试装置通过电路控制获得标准温差实现塞贝克系数的精确测量,其特点是利用电路控温取代传统的恒温循环水和温度测试仪表控温系统,结构简单、操作方便、成本低廉。     

Si3N4/Si表面Si生长过程的扫描隧道显微镜研究

利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si₃N₄/Si(111)和Si₃N₄/Si(100)表面生长过程的结构演变.在生长早期T为350—1075K范围内,Si在两种衬底表面上都形成高密度的三维纳米团簇,这些团簇的大小均在几个纳米范围内,并且在高温退火时保持相当稳定的形状而不相互融合.当生长继续时,Si的晶体小面开始显现.在晶态的Si₃N₄(0001)/S 关键词： 氮化硅 扫描隧道显微镜 纳米颗粒     

Si_3N_4/Si表面Si生长过程的扫描隧道显微镜研究

利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si3N4 /Si(111)和Si3N4 /Si(10 0 )表面生长过程的结构演变 .在生长早期T为 35 0— 10 75K范围内 ,Si在两种衬底表面上都形成高密度的三维纳米团簇 ,这些团簇的大小均在几个纳米范围内 ,并且在高温退火时保持相当稳定的形状而不相互融合 .当生长继续时 ,Si的晶体小面开始显现 .在晶态的Si3N4 (0 0 0 1) /Si(111)表面 ,Si的 (111)小面生长比其他方向优先 ,生长方向与衬底Si(111)方向一致 .最后在大范围内形成以 (111)为主的晶面 .相反 ,在非晶的Si3N4 表面 ,即Si3N4 /Si(10 0 ) ,Si晶体的生长呈现完全随机的方向性 ,低指数面如 (111)和 (10 0 )面共存 ,但它们并不占据主导地位 ,大部分暴露的小面是高指数面如 (113)面 .对表面生长过程进行了探讨并给出了合理的物理解释     

X射线干涉仪实现扫描控针显微镜样板线间距纳米测量

X射线干涉仪以非常稳定的单晶硅晶格作为长度单位,可以实现亚纳米精度的微位移测量。提出了将X射线干涉仪和扫描隧道显微镜结合起来,利用单晶硅的晶格尺度测量扫描探针显微镜样板节距的技术方案,并进行了实验研究。     

Progress of microscopic thermoelectric effects studied by micro- and nano-thermometric techniques

Heat dissipation is one of the most serious problems in modern integrated electronics with the continuously decreasing devices size. Large portion of the consumed power is inevitably dissipated in the form of waste heat which not only restricts the device energy-efficiency performance itself, but also leads to severe environment problems and energy crisis. Thermoelectric Seebeck effect is a green energy-recycling method, while thermoelectric Peltier effect can be employed for heat management by actively cooling overheated devices, where passive cooling by heat conduction is not sufficiently enough. However, the technological applications of thermoelectricity are limited so far by their very low conversion efficiencies and lack of deep understanding of thermoelectricity in microscopic levels. Probing and managing the thermoelectricity is therefore fundamentally important particularly in nanoscale. In this short review, we will first briefly introduce the microscopic techniques for studying nanoscale thermoelectricity, focusing mainly on scanning thermal microscopy (SThM). SThM is a powerful tool for mapping the lattice heat with nanometer spatial resolution and hence detecting the nanoscale thermal transport and dissipation processes. Then we will review recent experiments utilizing these techniques to investigate thermoelectricity in various nanomaterial systems including both (two-material) heterojunctions and (single-material) homojunctions with tailored Seebeck coefficients, and also spin Seebeck and Peltier effects in magnetic materials. Next, we will provide a perspective on the promising applications of our recently developed Scanning Noise Microscope (SNoiM) for directly probing the non-equilibrium transporting hot charges (instead of lattice heat) in thermoelectric devices. SNoiM together with SThM are expected to be able to provide more complete and comprehensive understanding to the microscopic mechanisms in thermoelectrics. Finally, we make a conclusion and outlook on the future development of microscopic studies in thermoelectrics.     

The influence of annealing temperature on the morphology of graphene islands

We report on temperature-programmed growth of graphene islands on Ru(0001) at annealing temperatures of 700°C,800°C,and 900°C.The sizes of the islands each show a nonlinear increase with the annealing temperature.In 700°C and 800°C annealings,the islands have nearly the same sizes and their ascending edges are embedded in the upper steps of the ruthenium substrate,which is in accordance with the etching growth mode.In 900°C annealing,the islands are much larger and of lower quality,which represents the early stage of Smoluchowski ripening.A longer time annealing at 900°C brings the islands to final equilibrium with an ordered moir’e pattern.Our work provides new details about graphene early growth stages that could facilitate the better control of such a growth to obtain graphene with ideal size and high quality.     

块体热电材料的研究进展

文章重点介绍了现役热电材料（Bi2Te3,PbTe,SiGe）、常见结构类型（方钴矿型,笼合物型,Half-Heusler合金型,钠钴氧型和Zn4Sb3型）热电材料及新颖晶体结构类型的热电材料的晶体结构、热电性能、热电性能优化等方面的最新研究进展.     

STM的同胞兄弟--原子力显微镜(AFM)

介绍了在扫描隧道显微镜（ＳＴＭ）基础上发展起来的原子力显微镜（ＡＦＭ）的工作原理、关键部分、工作模式及其应用。     

Influence of Interorbital Interference on Tunneling Process in STM

We present a theoretical study of the influence of intra-atomic interorbital interference on the formation of STM images of metal surfaces. The obtained results show that this kind of interference may modify significantly the tunneling current by the increase or decrease of the current contributions flowing through different orbitals of the surface atoms. STM simulations performed for aluminium and nickel surfaces indicate that the height of corrugation and the topographies of STM images of different surfaces depend considerably on this interference.     

摇摆型棘齿热电子隧穿制冷

本文利用传输矩阵法数值模拟了电子在加入周期性正负偏压的双势垒("摇摆"棘齿)异质结中的传输特性,获得了两电子库间的净电流以及所伴随的净热流的表达式.进一步分析了净电流、净热流和制冷系数等性能参数的特征,获得的结果对介观热电子器件的研制有一定的理论指导意义. 关键词： 热电子制冷机 摇摆棘齿 性能参数 传输矩阵法     

Tunable thermoelectric properties in bended graphene nanoribbons

The ballistic thermoelectric properties in bended graphene nanoribbons(GNRs) are systematically investigated by using atomistic simulation of electron and phonon transport. We find that the electron resonant tunneling effect occurs in the metallic–semiconducting linked ZZ-GNRs(the bended GNRs with zigzag edge leads). The electron-wave quantum interference effect occurs in the metallic–metallic linked AA-GNRs(the bended GNRs with armchair edge leads).These different physical mechanisms lead to the large Seebeck coefficient S and high electron conductance in bended ZZGNRs/AA-GNRs. Combined with the reduced lattice thermal conduction, the significant enhancement of the figure of merit ZT is predicted. Moreover, we find that the ZTmax(the maximum peak of ZT) is sensitive to the structural parameters. It can be conveniently tuned by changing the interbend length of bended GNRs. The magnitude of ZT ranges from the 0.15 to 0.72. Geometry-controlled ballistic thermoelectric effect offers an effective way to design thermoelectric devices such as thermocouples based on graphene.     

Solid-state resonant tunneling thermoelectric refrigeration in the cylindrical double-barrier nanostructure

A solid-state thermoelectric refrigerator with a cylindrical InP/InAs/InP double-barrier heterostructure is proposed.Based on the ballistic electron transport and the asymmetrical transmission, we derive the expressions of the performance parameters of this refrigerator. The cooling rate rather than the coefficient of performance is affected by the area of the inner cylinder. Then through the numerical simulation, a triangular cooling rate region is found with respect to the chemical potential and bias voltage; further, that it is because of the small full width at half maximum of the transmission resonance and the linear relationship between the energy position of resonance and the bias voltage. These tunable results might supply some guide to the cooling in tiny components or devices.     

Mg2Si的电子结构和热电输运性质的理论研究

利用全势线性缀加平面波法,对Mg₂Si的几何结构和电子结构进行了计算,得到了稳定的晶格参数以及能带和电子态密度.能带结构表明,Mg₂Si为间接带隙半导体,禁带宽度为020 eV.在此基础上利用玻尔兹曼输运理论和刚性带近似计算了材料的电导率、Seebeck系数和功率因子.结果表明,在温度为700 K时p型和n型掺杂的Mg₂Si功率因子达到最大时的最佳载流子浓度分别为7749×10¹⁹ cm^-3和 关键词： 2Si')" href="#">Mg₂Si 全势线性缀加平面波法 热电输运性质     

电子自旋共振扫描隧道显微镜

单电子自旋极有可能发展成为未来信息学的基础。以电子自旋为核心的新型单分子或单原子器件将最终成为基本信息单元,基于单电子的自旋态将有可能构筑未来量子计算机的量子比特。但是,如何实现对单个电子自旋及其相干态和纠缠态的测量和控制,目前仍然是一个很大的挑战。作为调控单个电子自旋的重要实验手段,电子自旋共振扫描隧道显微镜的发展一直备受关注。文章简要介绍了电子自旋共振扫描隧道显微镜的基本概念,阐述了其发展历史和最新进展,归纳了机理探索的研究成果,论述了该设备研发面临的挑战与对策,并对未来的发展和应用做了展望。