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

MRI：收购用于本科教育的薄膜生长和表征实验室

• 批准号: 0820025
• 负责人: Phillip Broussard
• 金额: $ 17.89万
• 依托单位: Covenant College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0820025&HistoricalAwards=false
• 关键词: MRI; Acquisition; Thin; Film; Growth

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.

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，将研究超导邻近效应中的边界条件问题。 对于具有超导和非超导材料的重复层的系统的超导转变温度将如何取决于边界条件，缺乏明确性。 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。 要考虑的系统将是铌和钨或锆的溅射层，层的数量级为60 nm或更大。 转变温度将通过电阻和电感方法表征。 第二个项目将研究薄铬膜在厚度减小时的行为，以了解材料是否会经历标准的金属-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“坏”金属，继续显示金属电阻率，在没有预期的情况下。 非晶Mo-Ge将被用作确实经历金属-绝缘体转变的材料的示例以用于比较。 我们的愿望是在费米液体理论被假定为不成立，但仍然观察到金属行为的制度，看看电子传导。 这两个项目都将深入了解金属中电子的行为。外行：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。 第一个项目涉及对电流流动失去所有电阻的材料（超导体），并将处理由于超导材料与不超导的金属之间的电接触而导致的这种行为如何变化。 两种不同的金属（铌和锆）将被分层，就像蛋糕一样，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，因为在某些时候，它们都必须在某些时候与非超导金属电接触。 第二项工作是观察金属载流能力的变化，因为电荷载流子可以移动的平均距离发生了变化。 在这个距离的某个值（大致是金属中原子之间的距离），大多数金属变成绝缘体，因为它们携带电流的能力非常差，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，并成为物理学家所说的“坏”金属。 相反，它们仍然表现得像金属一样，随着温度的降低，它们的载流能力变得更好，但总体能力比以前小得多。 这个项目将着眼于元素铬的薄层。 对于这两个项目，层的厚度约为人类头发的1/1600。