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Student Number 942202008
Author Shih-yu Weng(翁世宇)
Author's Email Address 942202008@cc.ncu.edu.tw
Statistics This thesis had been viewed 1403 times. Download 679 times.
Department Physics
Year 2006
Semester 2
Degree Master
Type of Document Master's Thesis
Language zh-TW.Big5 Chinese
Title The effects of interpartical interplay on superconductivity of Tin nanoparticles
Date of Defense 2007-06-20
Page Count 96
Keyword
  • critical temperature
  • nanoparticles
  • superconductivity
  • Tin
  • Abstract Two tin nanoparticles samples were fabricated via thermal evaporation method and identified their particle diameters as 3 nm and 6 nm by X-ray diffraction scheme. AC magnetic susceptibility measurements reveal the normal and superconducting state of 3 and 6 nm Sn samples at 1.8 K with zero applied magnetic field respectively. However, the Meissner effect appears in 3 nm Sn while interparticle separation reduces to 2 nm. At the end, 15.1 times diamagnetism signal from susceptibility measurement is observed between 6 nm and bulk sample as interparticle separation is almost zero. The origin of enhanced Meissner effect may be mainly contributed by DC Josephson effect due to reduction of tunneling distance.
    We define the relative separation as interparticle separation divided by particle diameter in order to study the variation on critical temperature of 3 nm and 6 nm Sn samples. As the relative separation is greater than 0.9, no superconducting signal was found in 3 nm Sn from susceptibility measurements; the TC of 6 nm Sn is higher than bulk one. While the relative separation lies between 0.9 and 0.2, the TC of two samples are depressed. It may be associated with the modification of phonon density of state. Nevertheless, the TC increases as the relative separation becomes below 0.2. It may be attributed to weakened Anderson effect. In addition, the polarization of electron spins exists in both samples.
    Table of Content 論文摘要…………………………………………………… I
    Abstract…………………………………………………… II
    致謝………………………………………………………… III
    目錄………………………………………………………… IV
    圖目與表目………………………………………………… VI
    第一章 金屬錫超導性質概論……………………………………1
    1-1 塊材錫的基本物理性質………………………………………1
    1-2 已知錫超導臨界溫度研究結果………………………………2
    1-3 實驗目的………………………………………………………5
    第二章 實驗樣品與儀器介紹……………………………………6
    2-1 奈米樣品製備…………………………………………………6
    2-2 奈米微粒壓合模具……………………………………………8
    2-3 交流磁化率實驗………………………………………………9
    2-4 奈米粒徑分析………………………………………………10
    2-5 樣品成份分析………………………………………………22
    第三章 超導理論…………………………………………………29
    3-1 奈米微粒平均間距估算……………………………………29
    3-2 奈米微粒超導相變磁化率描述……………………………31
    3-3 超導態的自由能與熵..……………………………………33
    3-4 超導體的約瑟夫遜隧道……………………………………35
    第四章 超導抗磁相變與臨界溫度…………………………………39
    4-1 塊材樣品與Sn_A樣品交流磁化率實驗結果………………39
    4-2 Sn_B樣品交流磁化率實驗結果……………………………51
    4-3 交流磁化率實驗結果擬合分析………………………………61
    4-4 超導抗磁磁化率變化探討……………………………………62
    4-5 臨界溫度變化探討……………………………………………70
    第五章 低溫電子自旋極化…………………………………………79
    5-1 沿外加磁場排列的自旋極化磁矩……………………………79
    5-2 自旋極矩磁化強度隨外加磁場變化關係……………………88
    第六章 結論…………………………………………………………93
    參考文獻………………………………………………………………95
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    Advisor
  • Wen-Hsien Li(李文献)
  • Files
  • 942202008.pdf
  • approve immediately
    Date of Submission 2007-07-16

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