MRI: Acquisition of a Thin Film Growth and Characterization Lab for Undergraduate Education

技术：拟议的研究将通过两种不同的途径研究金属中的电子传导问题。在第一个项目中，我们将研究超导邻近效应中的边界条件问题。对于一个由超导和非超导材料重复层叠的系统的超导转变温度将如何取决于边界条件，目前尚不清楚。表面如何影响超导转变温度的预测将与双层、三层和更复杂的层状结构的结果进行比较。要考虑的系统将是Nb和钨或锆溅射层，这些层的数量级为60 nm或更大。转变温度将用电阻和电感两种方法表征。第二个项目将观察随着厚度的减少，铬薄膜的行为，看看材料是否经历了标准的金属-绝缘体转变，这对于违反Ioffe-Regel限制的材料来说是预期的，或者它是否表现为一种“坏”金属，在不预期的区域继续显示金属电阻率。非晶态Mo-Ge将被用作经历金属-绝缘体转变的材料的例子，以供比较。我们的愿望是在假设费米液体理论不成立，但仍然观察到金属行为的区域内观察到电子传导。这两个项目都将深入了解电子在金属中的行为。莱曼：拟议的研究工作将着眼于金属中携带电子的电流在低温(约-440华氏度)下的行为。第一个项目涉及失去对电流流动的所有阻力的材料(超导体)，并将处理由于超导材料与不变成超导的金属之间的电接触而导致的这种行为如何变化。这两种不同的金属(Nb和Zirconium)将像蛋糕一样分层，并观察这如何影响它们失去电阻的温度。这项研究与超导体的使用有关，因为在某种程度上，它们都必须在某种程度上与非超导金属进行电接触。第二项工作是观察随着载流子平均行驶距离的变化，金属载流能力的变化。在这个距离的某个值(大约是金属中原子之间的距离)，大多数金属都会变成绝缘体，因为它们的载流能力很差，而且随着温度的降低，这种能力会变得更差。然而，有些材料不会以这种方式改变，变成物理学家所说的“坏”金属。相反，它们的行为仍然像金属一样，因为它们的载流能力随着温度的降低而变得更好，但总体能力比以前小得多。这个项目将研究铬元素的薄层。对于这两个项目，这些层的厚度大约是人类头发的1/1600。

Technical:The proposed research will look at issues in electron conduction in metals via two different routes. In the first project, the issue of boundary conditions in the superconducting proximity effect will be studied. There is a lack of clarity on how the superconducting transition temperature of a system with repeated layers of superconducting and non-superconducting materials will depend on the boundary conditions. The predictions of how surfaces affect the superconducting transition temperature will be compared against the results for bilayer, trilayer, and more complicated layered structures. The system to be considered will be sputtered layers of niobium and either tungsten or zirconium, with the layers being of order 60 nm or larger. The transition temperature will be characterized both by resistive and inductive methods. The second project will look at the behavior of thin chromium films as the thickness decreases to see if the material undergoes a standard metal-insulator transition which would be expected for a material that violates the Ioffe-Regel limit, or if it behaves as a "bad" metal which continues to show metallic resistivity in the regime where none would be expected. Amorphous Mo-Ge will be used as an example of a material that does undergo a metal-insulator transition for comparison. The desire is to look at electron conduction in the regime where Fermi liquid theory is assumed to not hold and yet a metallic behavior is still observed. Both projects will give insights to the behavior of electrons in metals.Laymen:The proposed research effort will be looking at how the current carrying electrons in metals behave at low temperatures (approximately -440 degrees Fahrenheit). The first project deals with materials that loose all resistance to current flow (superconductors) and will deal with how this behavior changes due to electrical contact between the superconducting material and a metal that does not go superconducting. The two different metals (niobium and zirconium) will be layered as in a cake and observed to see how this affects the temperature at which they loose their resistance. This study is relevant to the use of superconductors, for at some point, they must all be put into electrical contact with non-superconducting metals at some point. The second effort is looking at the change in a metal's ability to carry current as the average distance the charge carriers can travel changes. At a certain value of this distance, (roughly the distance between the atoms in the metal) most metals change to insulators, in that they have very poor ability to carry current and that ability gets worse as the temperature gets colder. However, some materials do not change in that manner and become what physicists call "bad" metals. Instead they still behave like metals in their ability to carry current gets better as the temperature is lowered, but the overall ability is much smaller than before. This project will look at thin layers of the element chromium. For both projects the layers will be about the thickness of 1/1600 that of a human hair.