氧化鋅摻鈷是室溫稀磁性氧化物的前瞻性自旋電子主要材料之一，概因該材料在室溫已呈現自旋載子偏極化現象，故在自旋電子學上的應用可能性極高。鑑於離子濺鍍系統中以δ-法成長之ZnO:Co薄膜中，鈷的溶解度僅約3.75%，本研究擬以單靶高週波濺鍍法來成ZnO:Co薄膜，企圖突破上述溶解度的限制。在則，因靶材中氧濃度非常足夠，加上高週波濺鍍電漿中之氧離子帶負電，易加速往薄膜方向前進，故成長的薄膜不易形成氧空缺，導致薄膜皆呈現絕緣特性。故本研究利用後退火製程或成長中摻入氫氣製程，試圖製造一系列具不同氧空缺程度的ZnO:Co薄膜，研究氧空缺形成及影響磁性與導電之機制。實驗上分兩部分，第一，調變成長薄膜的時間，成長不同厚度的薄膜；第二，在鍍膜過程中，通入不同比例的氫氣與氬氣，使氧離子還未能沉積在基板表面時，已經與氫離子反應了，進而成長出含有不同濃度之氧空缺及氫置入之薄膜。由方法一發現，薄膜中晶粒尺寸幾乎不變，但晶粒品質卻是隨著膜厚增加而變好。晶粒品質越差的薄膜，磁性與導電性在經後退火處理後的改善程度則越明顯，由此可以推斷導電性是需要在適當的晶粒品質與氧空缺的情況下才會有明顯的改善。方法二發現，當氫氬比超過20%後，鋅金屬會析出造成導電性持續變好，但是鐵磁性卻會逐漸消失。此現象的發現將有助於我們了解磁性與導電機制是如何運作。

Co-doped ZnO (ZnO:Co) thin film with room temperature ferromagnetism and spin polarized carriers is one of the advance materials and highly applicable in future development in spintronics. When ZnO:Co films deposited by a δ growth method in a ion sputtering system, low solubility of Co (3.75%) limits further applications such that a single-guns sputtering thin film growth technique is employed in this study to outreach this limitation. A ZnO:Co bulk with 5 at% of Co was formed by a solid reaction method and used as a target. ZnO:Co films were grown in a single-gun RF sputtering system. However, all films grown at room temperature were insulator which might because sufficient oxygen content in the target and the negative charge of oxygen ion moving toward substrate making the films of full oxygen content. In this study, the post annealing in vacuum environment and the deposition of films in hydrogenation environment are conducted to try to produce various level of oxygen vacancies in the films for understanding the interplay between the oxygen vacancies and the electric transport and magnetic coupling. The present experiment contains two parts: (1) grow films with various thicknesses by controlling deposition time and then applying post annealing process, and (2) grow the films in oxygen reduced environment by introducing hydrogen during growth and taking out partial oxygen content in the plasma and the films. In the first part, the grain sizes of the films are near constant while the crystal quality is improved with the thickness of films. The worse crystal quality of grains, the better the electric transport and the stronger the magnetic coupling after post annealing processes. This indicates that the electric transport and magnetic coupling could be improved when the thin films was formed by crystals with certain disordering and contained a certain level of oxygen vacancies. In the second part, the introduced hydrogen may combine with the oxygen sputtered out from the target before deposition on substrates. It means that the films are grown in oxygen deficient conditions and result in various degrees of oxygen vacancies. Zn clusters precipitate in films when the concentration of hydrogen is over 20%, and at the meantime, they increase the conductivity and suppress the magnetic coupling in the films. These discoveries provide new perspective in understand the electric transport and ferromagnetism mechanics in DMS materials.

Abstract ----------------------------------------------------------------------------------------------------------------- I
Chinese Abstract (中文摘要) -------------------------------------------------------------------------------------- III
Contents ---------------------------------------------------------------------------------------------------------------- IV
Table List --------------------------------------------------------------------------------------------------------------- VII
Figure List -------------------------------------------------------------------------------------------------------------- VIII

Chapter 1 Introduction
1-1 Introduction of Spintronic and Diluted Magnetic Semiconductor or Oxide (DMS or DMO) --- 1
1-2 Structure and Physical Property of ZnO ------------------------------------------------------------------- 5
1-3 Introduction of ZnO:Co DMS Thin Film and Motivation in this Study ------------------------------- 8
1-4 Reference --------------------------------------------------------------------------------------------------------- 13

Chapter 2 Relevant Theory and Paper
2-1 Interaction of Ferromagnetism and Electric Transport in DMS or DMO -------------------------- 14
2-1-1 RKKY Interaction -------------------------------------------------------------------------------------------- 15
2-1-2 Bound Magnetic Polaron Model ------------------------------------------------------------------------- 16
2-1-3 VRH Concentric Bounded Model ------------------------------------------------------------------------ 18
2-2 Reference --------------------------------------------------------------------------------------------------------- 22

Chapter 3 Experiment Process and Equipment
3-1 Preparation of Target ------------------------------------------------------------------------------------------- 23
3-1-1 Hot-Press System -------------------------------------------------------------------------------------------- 24
3-2 Deposition Process and Post-Process--------------------------------------------------------------------- 24
3-2-1 RF Magnetron Sputtering System ----------------------------------------------------------------------- 25
3-2-2 Deposition Process of Thin Films ------------------------------------------------------------------------ 27
3-2-3 Post Annealing System ------------------------------------------------------------------------------------- 29
3-2-4 Mask Aligner and Exposure System -------------------------------------------------------------------- 30
3-3 Measure equipment -------------------------------------------------------------------------------------------- 31
3-3-1 X-ray Diffraction ---------------------------------------------------------------------------------------------- 31
3-3-2 X-ray Absorption Spectroscopy -------------------------------------------------------------------------- 36
3-3-3 Magnetic Circular Dichroism (MCD) -------------------------------------------------------------------- 39
3-3-4 Superconductive Quantum Interference Devices (SQUID) --------------------------------------- 41
3-3-5 N&K Analyzer 1280 ----------------------------------------------------------------------------------------- 42
3-3-6 Hall Effect & Electro-Transport Property Measurement System -------------------------------- 43
3-3-7 Atomic Force Microscope (AFM) ------------------------------------------------------------------------ 44
3-4 Experiment Process ------------------------------------------------------------------------------------------- 47
3-4-1 Substrates Cleaning ---------------------------------------------------------------------------------------- 48
3-4-2 Vacuum Process and Change Samples during Deposition ----------------------------------- 48
3-4-3 Experiment Design ---------------------------------------------------------------------------------------- 49
3-4-4 Process ------------------------------------------------------------------------------------------------------- 50
3-5 Reference ------------------------------------------------------------------------------------------------------- 52

Chapter 4 Result and Discussion
4-1 Thickness Effect ---------------------------------------------------------------------------------------------- 55
4-1-1 Exploration -------------------------------------------------------------------------------------------------- 55
4-1-2 Thickness Effect -------------------------------------------------------------------------------------------- 61
4-2 Hydrogenation Effect ---------------------------------------------------------------------------------------- 72
4-2-1 Exploration -------------------------------------------------------------------------------------------------- 72
4-2-2 Hydrogenation effect--------------------------------------------------------------------------------------- 78
4-3 Reference ------------------------------------------------------------------------------------------------------ 89

Chapter 5 Conclusion
5-1 Grain Size Effect ---------------------------------------------------------------------------------------------- 90
5-2 Hydrogenation Effect ----------------------------------------------------------------------------------------- 91

Chapter 6 Appendix
6-1 Appendix I ------------------------------------------------------------------------------------------------------- 94
6-2 Appendix II (Thickness Effect) ------------------------------------------------------------------------------ 99
6-3 Appendix III (Hydrogenation Effect) ---------------------------------------------------------------------- 102

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