我們利用濺鍍系統成長了數個不同參數的鈮/鋁多層膜，在本系統中，可以變化的參數包括有鈮層的厚度dNb、鋁層的厚度dAl以及總層數。本實驗中固定每個樣品的總層數均為20層，也就是鈮和鋁各十層，保持每個樣品的單一鈮層厚度均為200A，依序變化鋁層厚度為0、50、100、200、400 A等五個不同的樣品。因此每個樣品的總厚度至少都有2000A，如此可避免size effect對量測的影響。在濺鍍過程中，濺鍍順序為鈮先鋁後，亦即形成基板/鈮/鋁/鈮/鋁/…/鈮/鋁的結構。最上面一層為鋁，是希望避免表面超導性(Surface Superconductivity)對Hc2的量測影響。我們測量了各樣品的零磁場下超導相轉變溫度Tc、平行方向上臨界磁場(parallel upper critical field)Hc2//以及垂直方向上臨界磁場(perpendicular upper critical field)Hc2⊥對溫度的曲線關係，探討這些結果在隨著dAl變化時的變化關係。我們將結果和I.K.Schuller所作的Nb/Cu多層膜實驗比較。並以de Gennes的鄰近效應(proximity effect)理論為基礎做了一些計算，比較並討論實驗和理論之間的差別。

We fabricate several Nb/Al multilayer samples with different parameters by using sputtering method. In our experiment, we keep the period numbers and each Nb layer thickness are 10 and 200 angstron respectively. We vary Al layer thickness from 0 to 400 angstron, therefore each sample has their total thickness larger than 2000 angstron to avoid size effect. We measure the two direction upper critical field versus temperature, one direction is parallel to film and the other one is perpendicular to film. We compare our experiment results with Nb/Cu multilayer systems which made by I.K.Schuller. We also use de Gennes-Werthamer proximity effect theory to fit my data and discuss it.

參考資料
[1] W.Deubner, Annin.Phys.5, 261, (1930)
[2] J.W.M.Dumond, J.P.Youtz, Phys.Rev.48, 703, (1935), J.Appl.Phys. 11, 357, (1940)
[3] M.R.Beasley, 1980, Inhomogeneous Superconductors p.186
[4] M.Strongin, O.F.Kammerer et al, Rhys.Rev.Lett.21,1320,(1968)
[5] H.Raffy, et al, Solid St.Commun.11,1679,(1972)
[6] H.Raffy, et al, Solid St.Commun.14,427,(1974)
[7] S.T.Ruggiero, T.W.Barbee, Jr.M.R.Beasley, Phys.Rev.B 29,4894
[8] Banerjee, Q.S.Yang, C.M.Falco, I.K.Schuller, Solid St.Commun.41,805,(1982)
[9] T.R.Werner, I.Banerjee, I.K.Schuller,Phys.Rev.B26,2224,(1982)
[10] I.K.Schuller, Phys.Rev.Lett.44, 1597,(1980)
[11] I.Banerjee, Q.S.Yang, C.M.Falco, I.K.Schuller, Phys.Rev.B28,5037,(1983)
[12] S.L.Cornelt, et al, I.K.Schuller, Phys.Rev.B.29, 4915, (1984)
[13] I.Banerjee, I.K.Schuller, JLTP, 54, 501, (1984)
[14] J.G.Bednorz, K.A.Muller, Z.Phys.B64,189,(1986)
[15] M.K.Wu et al, Phys.Rev.Lett.58,908,(1987)
[16] V.M.Krasnov, A.E.Kovalev, V.A.Oboznov, N.F.Pedersen, Phys.Rev.B54, 15448, (1996)
[17] P.Seng, R.Tidecks, K.Samner, G.Yu.Logvenov, V.A.Oboznov, JLTP, 106, 29, (1997)
[18] H.J.Fink, O.Laborde, J.C.Villegier, JLTP, 63, 151, (1986)
[19] L.N.Cooper, Phys.Rev.Lett.6,689, (1961)
[20] P.G.de Gennes, E.Guyon, Phys.Lett.3, 168, (1963)
[21] P.G.de Gennes, Rev.Mod.Phys.36,225, (1964), for a complete review
[22] N.R.Werthamer, Phys.Rev.132, 2440, (1963)
[23] S.Takahashi, M.Tachiki, Phys.Rev.B33, 4620, (1986)
[24] M.Tinkham, Introduction to Superconductivity, p.117
[25] M.Tinkham, Introduction to Superconductivity, p.135
[26] W.E.Lawrence, S.Doniach, in Proceedings of the 12th International Conference on Low Temperature Physics(Kyoto, Japan, 1970), p.361
[27] N.R.Werthamer, E.Helfand, P.C.Hohenberg, Phys.Rev.147, 295,(1966)
[28] 陳信孚, 清華大學材料科學工程學系碩士論文, p.56, (1997)
[29] Charles Kittel, Introduction to Solid State Physics, seventh edition
[30] J.J.Hauser, H.C.Theuerer, N.R.Werthamer, Phys.Rev.136, A637,(1964)