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Quantized electronic conduction of metallic nanowire made in low-temperature scanning tunneling microscope

低温扫描隧道显微镜制备金属纳米线的量子化电子传导

基本信息

批准号：
12440097
负责人：
KOMORI Fumio
金额：
$ 2.11万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Atomic-size wires of magnetic metals are formed in a scanning tunneling microscope (STM) by contacting the tip apex to the metal surface followed by withdrawing the tip from the surface. The electronic conduction of these wires depends both on the electronic states including spin states and on the atom arrangement around the wires. In the present study, we have developed a method to measure the conductivity between 4.2 K and room temperature in ultra high vacuum on clean surfaces, and measured the conductance of iron and nickel wires.1. We attached an annealing base up to 1200 degree G by electron bombardment to the present STM system to prepare clean surfaces of metal single crystals such as Ni. We also designed and made a new STM for the study of the electronic conduction.2. We measured the conductance of the iron nanowires as a function of the displacement between the surface and the STM tip. The observed conductance curves were quantized, and some steps in the conductance curves have hysteresis for repeated displacements. The unit of the quantization is e^2/h as expected in ferromagnetic materials without spin degeneracy. The magnetic field dependence of the conductance is generally small up to 150 mT. Only when the length of the wire is fixed close to the conductance step during the change of the displacement between the surface and the STM tip, the conductance step appears by changing the magnetic field. This is attributed to the effect of magnetostriction.3. The results on Ni single crystal is compared with those on Ni thin films. We found the magnetoresitance is dependent on the magnetization process of the substrate.

在扫描隧道显微镜（STM）上，通过将尖端与金属表面接触，然后将尖端从金属表面抽出来形成原子大小的磁性金属丝。这些导线的电子传导既取决于包括自旋态在内的电子态，也取决于导线周围的原子排列。在本研究中，我们开发了一种测量清洁表面在4.2 K和室温之间的超高真空电导率的方法，并测量了铁和镍线的电导率。我们用电子轰击法在现有的STM系统上附加了高达1200度G的退火基底，以制备镍等金属单晶的清洁表面。我们还设计并制作了一个新的用于研究电子传导的STM。我们测量了铁纳米线的电导作为表面和STM尖端之间位移的函数。观察到的电导曲线被量子化，电导曲线中的某些步长对重复位移有迟滞。在没有自旋简并的铁磁材料中，量子化的单位为e^2/h。电导对磁场的依赖性一般较小，可达150mt。只有在表面与STM尖端位移变化过程中，将导线长度固定在电导阶附近时，通过改变磁场才会出现电导阶。这是由于磁致伸缩的作用。比较了在Ni单晶和Ni薄膜上的实验结果。我们发现磁阻取决于衬底的磁化过程。