摘要
本實驗室已於文獻探討過[ZnO(20Å)/Co0.7Fe0.3(xÅ)]25多層膜在不同過渡金屬厚度下的磁性質。本論文主要利用其中CoFe厚度為1Å的部份，分兩主題進行相關的研究。
ㄧ. 為了縮短及節省其製程上的時間，我們比較在相同比例(CoFe~5%)，兩種不同製程(cosputter and discontinuous multilayers) 下，其磁性質與結構的差異性。
由分析結果我們可以清楚看出，以離子共濺鍍所成長的薄膜樣品，雖其3d過渡金屬摻雜的比例與多層膜[ZnO(20Å)/Co0.7Fe0.3(1Å)]25相近，但卻有部分形成金屬團簇(cluster)，造成順磁行為的發生。因此，稀磁性半導體的製程方法，為是否能成功成長出本質磁性半導體的關鍵。

二. 多層膜磁性半導體額外摻雜Cu原子導致其磁化量的提升以被許多團隊報導過，但其中的機制仍然眾說紛紜。於是，我們將Cu(1Å and 0.5Å)摻雜於多層膜磁性半導體[ZnO(20Å)/Co0.7Fe0.3(1Å)]25，藉由各種磁電性量測(Hall effect, NEXAS, …..)，試圖找出其磁性來源的合理解釋。
由霍爾效應結果知道，兩組樣品電子濃度均隨著Cu在薄膜中的比例增加而增加，因此，摻雜Cu導致磁化量提升的原因，似乎與載子濃度沒有直接的關聯性，亦即可能不是完全的carried-mediated mechanism。另ㄧ方面，我們由X光近吸收邊緣光譜(NEXAS)分析得知，額外的Cu摻雜並不會改變3d過渡金屬Co和Fe在材料中的價數，亦即，磁化量提升的原因，似乎也跟雙交換耦合機制(Double Exchange mechanism)沒有直接的關聯性。
最後，我們由Cu的NEXAS發現，少量的Cu在ZnO晶格內會誘發出磁性，但由於ZnO材料對Cu原子的溶解度相當低，所以當Cu摻雜約1Å時，則可能因為其未溶入ZnO晶格而形成其它氧化態，導致磁性消失。亦即Cu在材料中存在的價數，乃影響磁性質的重要關鍵。

Abstract
Multilayer growth and room-temperature ferromagnetism, [ZnO(20Å)/Co0.7Fe0.3(1Å)]25 have been reported[1.12] by our group. Here we study the relevant properties of diluted magnetic semiconductors(DMS) in multilayers [ZnO(10Å)/Co0.7Fe0.3(1Å)]25. The main results are summarized below.
1. The difference of magnetism and structure has been obtained for different growth process, i.e. by cosputtering and multilayers techniques. At a fixed CoFe concentration (~5%), the two techniques are compared to meet the requirement of fast production in semiconductor industry.
Though the doping concentration of 3d transition metal for cosputtering films is similar to discontinuous multilayers [ZnO(20Å)/CoFe(1Å)]25, more metal clusters form and contribute an additional paramagnetism. Therefore, one of the key factors to achieve a good DMS structure is the control of fabrication process.

2. It has been reported that using additional doping with Cu in TM-doped ZnO can enhance magnetic moment by experimental and theoretical work of the other groups. But the mechanism of the enhancement of ferromagnetism remains controversial. In this work, we undertook an investigation on CoFe/ZnO with and without inserting Cu layers to verify the role of Cu doping in magnetism. The [ZnO(20Å)/CoFe(1Å)]25 and [ZnO(10Å)/Cu(xÅ)/ZnO(10Å)/CoFe(1Å)]25 MLs with nominal thickness x=0.5 and 1 Å were fabricated by ion beam sputtering. These MLs were characterized by superconducting quantum interface device for magnetic properties, Hall effect measurement for electrical properties and near edge x-ray absorption spectra for electronic structures, respectively. The enhancement of magnetization for x=0.5 ML was larger than that without inserting Cu layers while the magnetization of x=1 ML remains unchanged with or without Cu doping. For both cases, the carrier concentration increased with increasing Cu layer thickness. It implies that the carrier-mediated mechanism may not be applicable to explain the fluctuation of magnetization. On the other hand, the transformation of the charge state of Cu from 1+ for x=0.5 ML to 2+ for x=1 ML has been observed while the charge state of Co and Fe atoms kept unchanged. The valence of Cu plays a key role influencing the magnetic properties.

【Reference】
[1.1] 黃榮俊、許華書，物理雙月刊，26期4卷2004年8月p.599
[1.2] J. K. Furdyna and J. Kossut, Semiconductor and Semimetals
vol. 25 (Academic press, New York, 1988)
[1.3] H. Munekata, T. Dietl，Phys. Rev. Lett. 63, 1849 (1989)
[1.4] H.Ohno, T. Dietl，Phys. Rev. Lett. 68, 2664 (1992)
[1.5] H.Ohno, T. Dietl，J. Vac. Sci. Techmol. B 18, 2039 (2000)
[1.6] H.Ohno, T. Dietl，Jap. Soc. Appl. Phys. Int. 5, 4 (2002)
[1.7] H.Ohno, T. Dietl，Appl. Phys. Lett. 69, 363 (1996)
[1.8] F. Matsukura, T. Dietl，Phys. Rev. B 57, 2037 (1998)
[1.9] Dietl, T. Semicond. Sci. Technol. (2002) 17 (14), 377
[1.10] H.Ohno, D. Chiba, F. Matsukura, T. Omiya, T. Dietl, Y.Ohno and
K. Ohtani，Nature 408, 944 (2000)
[1.11] Y.Ohno, T. Dietl，Nature 402, 790 (1999)
[1.12] J. C. A. Huang, H. S. Hsu, Y. M. Hu, C. H. Lee, Y. H. Huang, and M. Z. Lin，Appl. Phys. Lett. 85 (17), 25 October 2004，3815-3817
[1.13] H. T. Lin, T. S. Chin, J. C. Shih, R. T. Huang, F. R. Chen, and J. J. Kai，Appl. Phys. Lett. 85 (4), 26 July 2004，621-623
[1.14] Nguyen Hoa Hong, Virginie Brize, and Joe Sakai，Appl. Phys. Lett. 86 (8), 17 February 2005，082505(1-3)
[1.15] S-J. Han, J. W. Song, C.-H. Yang, S. H. Park, J.-H. Park, Y. H. Jeong, and K. W. Rhie，Appl. Phys. Lett. 81 (22), 25 November 2002，4212-4214
[1.16] Jeong Hyun Shim, Taesoon Hwang, Soonchil Lee, Jung Hye Park, Seung-Jin Han, and Y. H. Jeong，Appl. Phys. Lett. 85 (22), 15 February 2005，082503(1-3)
[2.1] 林素霞、黃肇瑞, 氧化鋅薄膜的特性改良及應用之研究, 國立成 功大學材料工程研究所博士班論文(2003).
[2.2] Zheng-wu jin, T. Fukumura, Appl. Phys. Lett. 78, 3824(2001).
[2.3] T. Dietl, Science 287, 1019(2000).
[2.4] 吳忠益, 一維稀磁半導體Zn1-XCoXO奈米線之製備與研究, 國立清華大學工程與系統科學所碩士班論文(2004).
[2.5] V. I. Litvinov, Phys. Rev. Lett. 86, 5593(2001).
[2.6] M. Berciu, Phys. Rev. Lett. 87, 7203(2001).
[2.7] H. Akai, Phys. Rev. Lett. 81, 3002(1998).
[2.8] J. Konig, Phys. Rev. Lett. 84, 5628(2000).
[2.9] J. Konig, Phys. Rev. Lett. 86, 5637(2001).
[2.10] 宛德福，馬興隆, 磁性物理學, 電子科技大學出版社(1994).
[2.11] 戴道生，錢昆明，鐘文定，廖紹彬, 鐵磁學, 科學出版社(2000).
[2.12] 施敏, 半導體元件物理與製作技術, 23-47(1997).
[3.1] 賴耿陽, IC 製程之濺射技術, 復漢出版社(1997).
[3.2] D. C. Koningsberger, R. Prins, X-ray Absorption principles, applications, technigues of EXAFS、SEXAFS and XANES, 574-575(1988).
[3.3] J. J. Rehr, R. C. Alers, Rev. Mod. Phys. 72, 621(2000).
[3.4] 國立台灣大學物理學系，楊鴻昌教授，科儀新知，第十二卷第六期, 72-79(1991).
[3.5] 邱繼廣、紀國鐘, 氮化鋁保護層應用於離子佈值活化之研究, 國立中央大學物理研究所碩士論文(2003).