超導薄膜層狀結構表面阻抗之計算

Abstract

這篇論文有六個章節。第一個章節是介紹超導體電磁基本特性，第二章節是敘述我們計算表面阻抗的理論及方法去。第三章節是我們要在半導體基板上求得超導體薄膜在中紅外光的頻段下的表面阻抗，在第三章節第一個結構下存在著一個導體薄膜的臨界厚度，能使整個結構的損耗達到最低，而且半導體的高頻相對介電常數也影響著超導體的表面阻抗，而在第三章節第二個結構中，半導體基板為有限的厚度，我們研究基板共振的情形。第四章節我們在鐵磁基板上求得超導薄膜的表面阻抗，我們分別改變超導體厚度以及鐵磁基板厚度，研究其表面阻抗的變化。第五章節是在超導體與半導體的周期結構下，除了探討一般的正向入射的情況外，還會探討斜向入射的情況，在正向入射的情況下，在不同的周期數時存在著一個超導薄膜的臨界厚度，能使整個結構的損耗達到最低，而在斜向入射的情況下，我們針對不同的周期數，其入射角對於表面阻抗之變化情形，也有加以探討，最後在第六章節是我們的結論。The thesis consists of six chapters. Chapter 1 is to give a brief review of basic properties of a superconductor. Chapter 2 introduces the theoretical methods to be used in the calculation of the effective surface impedance. In chapter 3, the effective surface impedance of a high-temperature superconductor thin film on a semiconductor plasma substrate is calculated. Two possible configurations are considered. The first one is a superconducting film deposited on a semi-infinite semiconductor substrate. It is seen there exists a critical film thickness for superconductor such that a minimum effective surface resistance is attained. The effective surface resistance is strongly dependent on the high-frequency permittivity of semiconductor plasma. The second will be limited to the more practical case, that is, the semiconductor substrate is of finite thickness. The investigation of substrate resonance in the effective surface resistance shows some fundamental distinctions when a semiconductor plasma substrate is introduced. In chapter 4, the structure is a superconducting film deposited on a ferromagnetic substrate. We investigate the effective surface impedance as a function of the different thicknesses of superconductor and ferromagnetic as well. In chapter 5, we investigate the effective surface resistance and surface reactance in the case of normal incidence in a superconductor-semiconductor superlattice. We find there is a critical thickness for superconductor film such that a minimum loss is attained. We next study the effective surface impedance under the oblique incidence. The calculated angle-dependent effective surface impedance indicates that it does not rely on the number of periods when the period is greater than two and, in the meantime, the surface resistance is nearly unchanged as a function of the angle of incidence. The conclusion is given in Chapter 6.