以掃描穿隧式電子顯微鏡對釔鋇銅氧高溫超導薄膜單電子穿隧電流與穿隧電壓關係之研究

Abstract

本論文主要在討論以掃描穿隧式電子顯微鏡(STM)量測不同氧含量下之釔 鋇銅氧高溫超導薄膜的單電子穿隧電壓與穿隧電流間的觀係。我們以脈衝 雷射蒸鍍法(PLD)在不同的基板上製作釔鋇銅氧高溫超導薄膜，再以一套 精確的系統控制薄膜的氧含量，然後在同一氧含量下利用STM在不同的溫 度區間量取穿隧電壓及穿隧電流；即對同一基板上的一塊樣品做一系列不 同氧含量在各個溫區的穿隧電壓與穿隧電流關係探討。同時，利用單電子 穿隧(SET)原理及N-I-N、N-I-S接面模型，我們對I-V曲線做一階導數並求 出釔鋇銅氧高溫超導薄膜的能隙值，再依數據討論薄膜表面的諸多性質， 最後與BCS理論做比較。 In this thesis, we mainly discuss the relationships between the single electron tunneling currents and tunneling voltages of YBCO high temperature superconducting thin films with various oxygen contents by a scanning tunneling microscope(STM). YBCO films were fabricated on several substrates by pulse laser deposition(PLD) method. Their oxygen contents were controlled with a homemade system. The tunneling currents I and tunneling voltages V were measured with the STM. The tunneling currents were then differentiated with respect to the voltages and the resulting dI/dV-V curves were used to calculate the superconducting energy gaps.