Controlled Fabrication of Tunnel Barriers and Electron Tunneling into High Tc Superconductors

这个实验研究项目专注于隧道势垒的受控制造，旨在允许对受强电子关联和降维影响的超导体进行隧道和输运研究。一个令人感兴趣的话题是低维系统中超导体-绝缘体转变的性质。另一个主题是在二维无序超导体和高T_c超导体之间寻找有用的类比。不同维度的样品将通过输运、隧道和扫描隧道显微镜进行研究，强调维度交叉和无序的影响。这个实验研究项目基于被称为电子隧道的技术的使用，特别是基于寻找适合于使用该技术的制造势垒的方法。电子隧穿是一种量子力学过程，通过它电子可以越过势垒或“山”，这在经典物理规则下是无法克服的，控制着行星和网球等宏观物体。量子力学允许这样的山丘在概率的基础上被隧道穿过，可测量的转移速率被限制在非常小的质量和很短的距离(Angstrom标度)的情况下，例如原子中的电子。电子隧穿技术在确定态密度方面很重要，特别是在超导体中；也是扫描隧道显微镜的基础。本研究项目探讨了原子尺度无序和几何构型对输运的影响，重点研究了金属-绝缘体的转变。感兴趣的几何图形包括平面和一维线性样本。这项研究的结果可能包括不同寻常的新效果或结构，这些可能会在技术上得到应用。这项研究项目本质上是跨学科的，涉及研究生和博士后，他们将接受良好的培训，以进入工业、政府或教育职位。***

w:\awards\awards96\num.doc 9705180 Dynes This experimental research project focuses on the controlled fabrication of tunnel barriers intended to permit tunneling and transport studies of superconductors that are subject to strong electron correlations and to reduced dimensionality. A topic of interest is the nature of the superconductor-insulator transition in lower dimensional systems. A further topic is the search for a useful analogy between two-dimensional disordered superconductors and high Tc cuprate superconductors. Samples of varying dimensionality are to be studied by means of transport, tunneling, and scanning tunneling microscopy, emphasizing the effects of dimensional crossover and disorder. %%% This experimental research project is based on use of the technique known as electron tunneling, and in particular on finding methods to fabricate barriers suitable for the use of this technique. Electron tunneling is a quantum-mechanical process by which an electron can pass a potential barrier or "hill", which could not be overcome under the rules of classical physics, governing macroscopic objects like planets and tennis balls. Quantum mechanics allows such hills to "tunneled under" on a probabilistic basis with measurable rates of transfer limited to cases of very small mass and short (Angstrom scale) distances, such as the case of electrons in atoms. The technique of electron tunneling is important in determining the density of states, especially in superconductors; and also as the basis for the scanning tunneling microscope. This research project probes the effects of atomic scale disorder and geometric configuration on transport, with emphasis on the metal-insulator transition. Geometries of interest include planar and one-dimensional linear samples. Results from this research may include unusual new effects or st ructures which may find application in technology. This research project is interdisciplinary in nature and involves graduate and postdoctoral students who will be excellently trained to enter positions in industry, government or education. ***