Current-Induced Instability in the Quantized Conductance States of MetaNanowires and Their Reinforcement by Alloying

金属纳米接触，特别是由一个原子组成的单原子接触，当它们受到高偏压/高电流条件时会变得不稳定。本研究在2002-2003财政年度进行，通过实验研究这种电流引起的金属纳米接触的不稳定性，阐明其机制，并调查合金化是否抑制不稳定性。在Au、Ag、Cu和Al接触中，单原子接触（SAC）的形成概率p随着偏压的增加而减小，并且在临界偏压V^处消失<bc>。在更高的偏置/电流下，尺寸缩小的接触因此变得更不稳定，留下更少的机会成为SAC。对于p_，V_i的值<bc>为2.3V，对于<Au>p_，p_，和P_，V_i的值分别为0.6- 0.8V<Ag><Cu><Al>。尽管在V^上存在差异<bc>，但所有这些ps都显示出普遍的偏压依赖性，表明这四种金属共有的不稳定性机制2。实验 ...更多信息 对贵金属纳米接触断裂电导的研究表明，存在接触断裂的临界电流密度。Au、Ag和Cu纳米接触对于它们的临界电流密度具有相似的值，其为10^<10>A/cm ^2的数量级。当通过颈缩变形使接触收缩时，一旦接触电流密度超过临界值，接触变得不稳定并断裂.然而，一些相对稳定的接触可能会在不稳定性中幸存下来，并继续变形成为SAC。因此，SAC形成概率基本上是这种接触在不稳定条件下通过其变形的存活率。对p的这种新解释可以解释其观察到的偏差依赖性。Ag和Cu纳米接触显示出另一种类型的不稳定性，其在低电导制度中占主导地位，并且在Au中不出现。这种新的不稳定性的存在提供了为什么p_<Ag>和p_<Cu>具有比Au低的V_的原因<bc>。AuPd和AuPt合金的SAC形成概率与AuAg和AuCu合金的SAC形成概率具有不同的偏压依赖性，并且随着偏压的增加而减小得更快。目前尚不清楚是什么合金效应导致四种合金的ps差异。少

Metal nanocontacts, single-atom contacts consisting of only one atom in particular are found to become unstable when they are subject to high bias/high-current conditions. This research, conducted through 2002-2003 fiscal years, was to study experimentally this current induced instability in metal nanocontacts, clarify its mechanism(s), and investigate whether alloying suppresses the instability or not Main results obtained in this work are listed below.1. In Au, Ag, Cu, and Al contacts, the formation probability p of single-atom contacts (SACs) decreases with increasing bias and vanishes at a critical bias V^<bc>. Under higher biases/currents, a contact shrinking in size thus becomes more unstable, leaving less chance to be a SAC. The value of V^<bc> is 〜2.3V for p_<Au> and 0.6-0.8 V for p_<Ag>, p_<Cu>, and P_<Al>, respectively. Despite the difference in V^<bc>, all these ps show a universal bias dependence, indicating an instability mechanism common to these four metals2. Experiments … More on the fracture conductance of noble metal nanocontacts have ervealed the existence of a critical current density for contact rupture. Au, Ag, and Cu nanocontacts have similar values for their critical current density, which is the order of 10^<10>A/cm^2. When one shrinks a contact by necking deformation, the contact becomes unstable and fractures once the contact current density exceeds the critical value.3. However, some relatively stable contacts may survive the instability and continue the deformation to become a SAC. Therefore, the SAC formation probability is basically a survival rate of such a contact through its deformation under unstable condition. This new interpretation of p can account for its observed bias dependence.4. Ag and Cu nanocontacts show another type of instability which dominates in a low conductance regime and does not appear in Au. The existence of this new instability provides the reason why p_<Ag> and p_<Cu> have lower V_<bc> than that of Au.5. SAC formation probabilities of AuPd and AuPt alloys have different bias dependence from those of AuAg and AuCu alloys and diminish more rapidly with increasing the bias. It is not clear at this time what alloying effects bring about this difference in ps of four alloys. Less