MoC intermediate layer for FePt magnetic recording media

A (001) textured FePt film was deposited on MoC/CrRu/glass at heated-substrate by using magnetron sputtering in 4-guns sputter system with DC power supply. We studied the effect of MoC conductive intermediate layer on CrRuFePt system. My work would step by step with three parts. In the first part, the FePt films were deposited on different MoC thickness at 380℃. And the MoC intermediate layer was used to resist the Cr diffusion up to high deposition temperatures and promotes the epitaxial growth of the (001) texture FePt films. The FePt showed high perpendicular magnetization and the out-of-plane coercivity increased with MoC thickness. The FePt/MoC (5 nm)/CrRu film showed a square out-of-plane magnetic hysteresis loop with a coercivity of 6.0 kOe and a linear-like in-plane loop. We also learned that the FePt particles would concentrate in the rectangular structure by specific orientation at certain temperature. The second part was fixed the FePt (10 nm)/MoC (5 nm)/CrRu film thickness and changed the deposited temperature of FePt films from 260℃ to 410℃. We can obviously observe that the FePt started to order at 320℃ and the ordering degree reach to 0.79 when the FePt deposited at 410℃, also the square magnetization curve showed and the greater out-of-plane Hc value of 6.9 kOe was obtained. In addition, the rectangular structure which shows at 380℃ was surmised to be a transition-shape. Once the deposition temperature slightly increased, the rectangular area would be dispersing into particular-like. In the final part, the substrate temperature of FePt (t)/MoC (5 nm)/CrRu film was fixed and the FePt thickness t changed from 4~10 nm. At such high deposited temperature of 410℃ could obtain a great magnetic property on all of samples on this part. The highest coercivity value was 8.3 kOe when FePt thickness was 5 nm. We found that the magnetic property of FePt/MoC/CrRu films might be more related to ordering degree rather than microstructur. A multi-fuctional MoC intermediate layer exhibited heteroepitaxial relation with FePt and CrRu and was capable of resisting the underlayer diffusion at high deposition temperature.本實驗使用配備四支磁控濺鍍槍之高真空濺鍍系統，皆以直流電源供應器供給各靶材所需之濺鍍功率，在基座加熱至高溫狀態下於玻璃基板上依序沉積CrRu底層、MoC中間層，最後堆疊FePt磁記錄層，研究導體之MoC中間層材料於CrRuFePt的磊晶膜層系統中其對FePt序化之影響。 實驗循序漸進分為三個部分：首先在380℃高溫下，於CrRu (80 nm)/glass底層上沉積MoC 0~5 nm，再沉積FePt 10 nm。實驗結果觀察發現隨MoC厚度增加，FePt (001)織構強度被有效提升，且垂直膜面之矯頑磁力亦隨之升高。於FePt/MoC (5 nm)/CrRu膜層樣品觀察，其呈現方正之垂直膜面磁滯曲線，矯頑磁力高達6.0 kOe，而水平膜面之磁滯迴路接近線性，顯示出極佳之垂直磁異向性。證明5 nm MoC可有效在高沉積溫度下阻擋底層擴散並促使FePt序化。另外可於微結構觀察到在此溫度下FePt顆粒會依特定方向性聚集排列成長方狀的島狀結構。 第二部分實驗為固定膜層厚度FePt (10 nm)/MoC (5 nm)/CrRu並改變FePt沉積溫度 ，觀察發現FePt於320℃便開始序化，沉積溫度提高至410℃時FePt序化度提高至0.79，並得到垂直矯頑磁力6.9 kOe。微結構方面發現第一部分FePt之長方狀結構僅出現在380℃，推斷為一過渡形貌，稍加溫度即會使此狀態崩散成一般顆粒膜，另外可觀察到隨沉積溫度提高，FePt膜層由原本連續性薄膜轉變成島狀之顆粒膜型態。 最後一部分為改變FePt薄膜之厚度，在沉積溫度410℃下樣品皆能得到不錯的磁性質，整體來看，膜層厚度降低序化度以及垂直矯頑磁力有升高的趨勢，於FePt 5 nm時垂直膜面之Hc達8.3 kOe，再進一步降低膜層厚度至4 nm時會因應力釋放使得FePt沿c軸垂直排列崩解而破壞整體膜層的序化度以及磁性質。而第二及第三部分實驗發現此膜層系統之磁性質與微結構較無關聯，磁性質好壞依序化程度而變動。致謝 ............................................................... i 摘要 .............................................................. ii Abstract .......................................................... iii 目錄 .............................................................. iv 表目錄 ........................................................... vii 圖目錄 .......................................................... viii 符號說明 ........................................................ xiii 第一章 緒論 ....................................................... 1 1-1 前言 ................................................................................................................... 1 1-2 硬碟的發展與簡介 ............................................................................................. 2 1-3 背景與研究動機 ................................................................................................. 7 第二章 實驗基礎理論與文獻回顧 ...................................... 9 2-1 材料之晶體結構 ................................................................................................. 9 2-1-1 FePt合金結構.......................................................................................... 9 2-1-2 序化與非序化 ....................................................................................... 11 2-1-3 CrRu合金與MoC化合物之結構與磊晶關係 ....................................... 12 2-2 理論基礎 .......................................................................................................... 15 2-2-1 磁性材料 ............................................................................................... 15 2-2-2 磁異向性 ............................................................................................... 16 2-2-3 磁滯曲線 ............................................................................................... 19 v 2-2-4 FePt薄膜之序化度計算 ........................................................................ 22 2-3 文獻回顧 .......................................................................................................... 27 2-3-1 FePt薄膜之文獻回顧 ............................................................................ 27 2-3-2 CrRu薄膜底層之文獻回顧 ................................................................... 28 2-3-3 FePt/CrRu膜層中間層之文獻回顧 ....................................................... 32 第三章 實驗流程與儀器原理 ......................................... 37 3-1 實驗流程 .......................................................................................................... 37 3-2靶材選擇 ........................................................................................................... 38 3-3基板之選用及清洗 ........................................................................................... 38 3-4 試片製備 .......................................................................................................... 40 3-4-1 磁控濺鍍系統 ....................................................................................... 40 3-4-2 薄膜製備 ............................................................................................... 41 3-4-3 實驗設計 ............................................................................................... 43 3-5 分析設備與分析方法 ....................................................................................... 44 3-5-1膜厚量測及表面粗糙度 ......................................................................... 44 3-5-2 晶體結構分析 ....................................................................................... 45 3-5-3 磁性量測 ............................................................................................... 48 3-5-4 微結構觀察 ........................................................................................... 50 3-5-5 元素分佈 ............................................................................................... 54 3-5-6 基板溫度校正...........................................................................................55 第四章 結果與討論 ................................................. 56 4-1 MOC中間層膜厚變化之探討 ........................................................................... 57 4-1-1 MoC中間層膜厚變化之X-ray繞射分析 .............................................. 57 4-1-2 MoC中間層膜厚變化之VSM磁性質分析 ........................................... 59 vi 4-1-3 MoC中間層膜厚變化之TEM微結構分析 ........................................... 61 4-2 FEPT沉積溫度變化之探討 ............................................................................... 64 4-2-1 FePt沉積溫度變化之X-ray繞射分析 .................................................. 64 4-2-2 FePt沉積溫度變化之VSM磁性質分析 ............................................... 66 4-2-3 FePt沉積溫度變化之TEM微結構分析 ............................................... 68 4-2-4 FePt沉積溫度變化之AFM表面粗糙度分析 ....................................... 71 4-3 FEPT膜厚變化之探討 ....................................................................................... 72 4-3-1 FePt膜厚變化之X-ray繞射分析 .......................................................... 72 4-3-2 FePt膜厚變化之VSM磁性質分析 ....................................................... 73 4-3-3 FePt膜厚變化之TEM微結構分析 ....................................................... 76 第五章 結論 ....................................................... 79 參考文獻 .......................................................... 8