Research Initiation Award: Thermal Boundary Resistance in Thin-Film High-Temperature Superconductors

高温超导薄膜与衬底界面处的热边界电阻（Rbd）是决定高温超导器件工作温度和可行性的重要因素。研究目标是对薄膜/衬底界面微观结构与Rbd之间的关系有一个基本的理解，并建立一个Rbd与易于测量的特性（如Tc、临界电流和正常状态电阻率）相关的模型。实验进行，使用封闭循环低温装置，在薄膜蚀刻在一个新的双条弯曲模式，使正常和超导状态的测量进行。提出了两种实验方法。其中一种是连续波可见激光束作为热源，从而实现超导状态的测量。在另一种情况下，改变高Tc薄膜的氧含量，从而可以控制薄膜的Tc，从而在比通常低得多的温度下形成正常状态的薄膜。这允许两个条带作为加热器和/或温度计后，他们的电阻与温度的校准。实验结果可以比较超导态和正常态薄膜的Rbd，为高tc薄膜器件的热设计提供有价值的信息。

ABSTRACT -- CTS 9307753 Phelan The thermal boundary resistance (Rbd) occurring at the interface between high-critical-temperature (high-Tc) superconducting thin films and their substrates plays a major role in determining the operating temperature, and hence the feasibility, of high-Tc superconducting devices. The research objectives are to develop a fundamental understanding of the relationship between the film/substrate interface microstructure and Rbd, and to formulate a model relating Rbd to easily measurable properties like Tc, critical current, and normal-state resistivity. Experiments are performed, using a closed-cycle cryogenic apparatus, on films etched in a novel two-strip meander pattern that enables both normal and superconducting-state measurements to be conducted. Two experimental procedures are proposed. In one, a continuous-wave, visible laser beam serves as a heat source, thus allowing for superconducting-state measurements. In the other, the oxygen content of the high-Tc film is varied so that the film Tc can be controlled, resulting in a normal-state film at temperatures much lower than usual. This allows the two strips to serve as heaters and/or thermometers after a calibration of their electrical resistances versus temperature. The experimental results permit a comparison between Rbd for superconducting-state and normal-state films, and provide valuable information for the thermal design of high-Tc thin-film devices.