Conductance in Nanocontacts of Soft Metals and Liquid Metals

众所周知，在诸如Au的软金属中可以最好地观察到金属量子点接触中的电导量子化。然而，迄今为止，还没有系统的研究进行了金属的机械强度如何影响其接触的电导量化。这项研究是在1999-2000财政年度进行的，目的是澄清金属硬度与其原子大小接触中电导量子化现象之间的相互关系。主要结果如下：1.我们研究了五种不同硬度的过渡金属Pd、Pt、Rh、Ru和Ir的电导，发现它们都没有表现出像Au那样明显的电导量子化。但电导特性依赖于金属，电导量子化程度与金属的机械强度之间存在弱相关性.虽然液态汞是最软的金属，但它也几乎没有任何证据表明 ...更多信息 电导量子化。我们发现，汞的电导特性依赖于接触断开的速度。在快速断开继电器触点中，汞在瞬态电导迹线中没有电导平台。通过使用缓慢断开的机械接触，我们可以观察到，不经常但偶尔，定义良好的量子化电导平台。合金化是强化金属的一种典型方法。因此，我们对AuPd合金进行了实验，以阐明合金化对电导量子化的影响。在AuPd中，发现随着Pd浓度的增加，电导特性从纯Au向纯Pd转变。Au直方图中的量化电导峰通过与Pd合金化而降低，并且逐渐被Pd直方图的宽结构特征所取代。一个重要的发现是，第一个电导峰显示没有峰位移后，钯合金化。这一观察结果表明，溶质原子的电子散射比产生峰位移强得多。少

It is well known that the conductance quantization in quantum point contacts of metals can be best observed in soft metals such as Au. However, no systematic studies have been performed so far on how mechanical strength of metals influences the conductance quantization in their contacts. This study was conducted through 1999-2000 fiscal years to clarify the interrelation between hardness of metals and the appearance of conductance quantization in their atom-sized contacts. Main results obtained in this work are listed below.1. We investigated the conductance of five transition metals of different hardness, Pd, Pt, Rh, Ru, and Ir, and found that none of them exhibit the conductance quantization as clearly as that of Au. However, the conductance characteristics depends on metals, and a weak correlation can be found between the degree of conductance quantization and the mechanical strength of metals.2. Although liquid Hg represents the softest metals, it also exhibits hardly any evidences … More of the conductance quantization. We found that the conductance characteristics of Hg depend on the speed of contact breaking. In fast-breaking relay contacts, Hg shows no conductance plateaus in transient conductance traces. With the use of a slow-breaking mechanical contact, we can observe, not often but occasionally, well-defined quantized conductance plateaus.3. Alloying is a typical method of strengthening metals. We, therefore, carried out experiments on AuPd alloys to clarify the influence of alloying on the conductance quantization. In AuPd, it is found that the conductance characteristics transform gradually from that of pure Au to that of pure Pd with increasing the Pd concentration. Quantized conductance peaks in the histogram of Au are reduced by alloying with Pd, and gradually replaced by a broad structure characteristic of the Pd histogram. An important finding is that the first conductance peak shows no peak shift upon Pd alloying. This observation suggests that the electron scattering by solute atoms is much stronger than to generate the peak shift. Less