分子束磊晶及電子槍蒸鍍準備之鋁薄膜的超導特性研究

Superconductivity in aluminum films prepared by MBE and electron gun evaporation

葉茂榮(Mao-Rong Yeh)

指導教授 ： 梁啟德

國立臺灣大學/理學院/物理研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00236

摘要

在此論文的前半部研究，我們描述準備與測量由分子束磊晶長成的四塊不同厚度的鋁薄膜(12，16，20與60 nm)並呈現其AFM及XRD的圖形且藉此討論其構造。我們進一步藉由研究這四塊鋁薄膜的超導特性來驗證由AFM與XRD圖所推測的結構特性並得到更詳細的推論。我們測量電阻率、臨界溫度、臨界磁場、臨界電流等作為判斷的參數，並利用Drude model 及其他修正來計算平均自由路徑藉以討論薄膜結構的均勻狀態。我們亦觀察到在不同平均自由路徑的修正下會影響我們對超導分類的判斷。對於平均自由路徑的修正我們考慮到尺寸效應、顆粒效應、以及電子侷限效應等等。在論文的後半部研究，我們描述準備與測量由電子槍蒸鍍長成的二塊不同厚度的鋁薄膜(30與60 nm)並且執行與分子束磊晶長成的薄膜相同的研究與測量，我們得到與先前研究有相當差異的結果。我們最後比較這兩種長晶法所得到的鋁薄膜的結構差異，得到電子槍蒸鍍長成的鋁薄膜與分子束磊晶長成的12 nm鋁薄膜會有較小且完整的顆粒。

關鍵字

分子束磊晶 ； 電子槍蒸鍍 ； 鋁薄膜 ； 尺寸效應 ； 顆粒效應 ； 電子侷限效應

並列摘要

In the first part of this thesis, we describe preparation and measurements of use MBE-grown Al thin films with four different thicknesses (12, 16, 20 and 60 nm) and then present the information from AFM and XRD patterns of the flims we judge the structures of the four films. Furthermore, by studying superconductivity of the films and comparing the experimental results with the previous theories we analyze the details of the Al structures. We had measured the normal resistivity , the critical temperature Tc, the critical filed Hc, the critical current density Jc as the judging parameters and calculated the mean free path l by Drude model and several corrections to discuss the homogeneity of the structures. We also observe the variation of the superconducting classification with different corrections of l and discovery that the mean free path indeed influences the classification by altering the penetration depth and the coherence length. The corrections of l are in consideration of size effect, granular boundary scattering, electron localization, etc. In the second part of this thesis, we describe preparation and measurements of E-gun-grown Al thin films with two different thicknesses (30 and 60 nm) and undertake the same research as that done on the MBE-grown films. Finally, we compare the structures and superconductivity of the MBE and E-gun films. We suggest that the grains of the E-gun-prepared films are more complete and smaller.

並列關鍵字

MBE ； E-gun ； Al film ； size effect ； granular effect ； electron localization

參考文獻

[1] V. L. Ginzburg and L. D. Landau, Zh. Eksp. i Teor. Fiz. 20, 1064 (1950).

[12] V. L. Ginzburg and L. D. Landau, Zh. Eksp. i Teor. Fiz. 20, 1064 (1950).

[8] Charles P. Poole, Jr., Horacio A. Farach, and Richard J. Creswick, in “Superconductivity”, Chap. 6, Academic Press, 1995.

[5] Charles P. Poole, Jr., Horacio A. Farach, and Richard J. Creswick, in “Superconductivity”, Chap. 1, Academic Press, 1995.

[2] Charles P. Poole, Jr., Horacio A. Farach, and Richard J. Creswick, in “Superconductivity”, Chap. 5, Academic Press, 1995.