CoPt-SiNx /Ag薄膜與CoPt-SiNx -Ag/Ag薄膜的製作與磁性質及微結構研究

Study of fabrications, magnetic properties and microstructures of CoPt-SiNx /Ag films and CoPt-SiNx -Ag/Ag films

郭俊廷(Chun-Ting Kuo)

指導教授 ： 郭博成

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02624

摘要

本研究以直流磁控濺鍍的方式，在室溫於自然氧化的矽基板及玻璃基板上鍍製CoPt薄膜，搭配Ag底層及添加SiNx與Ag於CoPt薄膜中，以形成五種不同的多層膜結構，分別為（a）CoPt/Ag,（b）CoPt-SiNx / Ag,（c）( SiNx / CoPt )9 / Ag,（d）( CoPt-SiNx / CoPt )9 / Ag,（e）( CoPt-SiNx -Ag/ CoPt )9 / Ag，探討Ag底層的厚度、SiNx與Ag添加物的含量及退火溫度與時間的改變對Co50Pt50薄膜之顯微結構、磁性質及其易磁化軸方向的影響。
在CoPt/Ag薄膜方面，引入不同厚度的Ag底層於CoPt薄膜後，發現有降低CoPt序化溫度的效果，其序化溫度從單層CoPt的700°C降至600°C。這是因為Ag底層與CoPt的晶格不匹配，產生了應力，促使CoPt薄膜的序化並具有垂直膜面磁異向性。CoPt (16 nm)/ Ag (30 nm)於700°C退火30分鐘之後，具有最好的垂直膜面磁異向性，其垂直膜面矯頑磁力Hc⊥值為18000 Oe、水平膜面矯頑磁力Hc//值為12200 Oe、飽和磁化量Ms值為388 emu/cm3、垂直膜面角形比S⊥值為0.93及水平膜面角形比S//值為0.42。
另一方面，改變SiNx添加於CoPt薄膜內的方式，發現CoPt的磁性質會受到CoPt-SiNx濺鍍方式的不同而改變，使其I001/I111比值會從CoPt-SiNx / Ag薄膜的0.92上升到( CoPt-SiNx / CoPt )9 / Ag薄膜的1.24，造成CoPt的易磁化軸會由random趨向於垂直膜面方向。( CoPt-SiNx / CoPt )9 /Ag (30 nm)薄膜700°C退火30分鐘後會有最好的垂直磁異向性。其Hc⊥＝16300 Oe、Hc//＝14600Oe、Ms＝295 emu/cm3、S⊥＝0.80及S//＝0.44。
此外，我們發現的( CoPt-SiNx / CoPt )9 /Ag (30 nm)薄膜，經過700°C退火30分鐘之後，SiNx的添加會破壞原來CoPt (16 nm)/ Ag (30 nm)薄膜的垂直磁異向性結構，但隨著SiNx添加量的增加，其垂直磁異向性結構會由於擴散產生的空位而再次出現。當SiNx添加很多的時候，使得CoPt晶粒大幅縮小且部分晶粒小於超順磁粒子尺寸，導致其矯頑磁力下降。
最後，我們將引入不同體積百分率的Ag於(CoPt)53.8(SiNx)46.2/Ag薄膜中，形成[(CoPt)53.8(SiNx)46.2]yAg1-y /Ag薄膜，希望能降低 CoPt的序化溫度。實驗結果顯示，Ag的添加會使(CoPt)53.8(SiNx)46.2/Ag薄膜的序化溫度從原先的600°C降至500°C。但隨著Ag添加量過多，將會造成磁性質的下降。而[(CoPt)53.8(SiNx)46.2] 40.8Ag59.2 / Ag(30 nm)薄膜於600°C退火30分鐘後有最好的垂直膜面磁性質，其Hc⊥＝9600 Oe、Hc//＝5500 Oe、Ms＝127 emu/cm3、S⊥＝0.75及S//＝0.49。

關鍵字

CoPt薄膜 ； 顆粒狀結構 ； 序化溫度 ； 垂直膜面磁性質 ； Ag底層

並列摘要

The Ag under layers were deposited on naturally oxidized Si (100) wafer and glass substrates by dc magnetron sputtering at room temperature. Subsequently, SiNx, Ag and CoPt films were co-sputtered on the Ag films at room temperature to form five kinds of multilayer films：（a）CoPt/Ag,（b）CoPt-SiNx / Ag,（c）( SiNx / CoPt )9 / Ag,（d）( CoPt-SiNx / CoPt )9 / Ag, and（e）( CoPt-SiNx -Ag/ CoPt )9 / Ag. The effects of Ag underlayer thickness, annealing temperature and time, and the contents of SiNx and Ag, on the microstructure, magnetic properties, and easy axis orientation of these magnetic films were investigated.
For the CoPt/Ag films, the ordering temperature of CoPt films could be decreased from 700°C to 600°C as the Ag underlayer was introduced beneath the CoPt films. The misfit between CoPt film and Ag underlayer cause the strain energy to provide the energy for fcc-CoPt film to transform from fcc-CoPt(001) to fct-CoPt(001) and fct-CoPt(002) phases. After annealing at 700°C for 30 minutes, the CoPt (16nm)/ Ag (30 nm) film shows the best perpendicular anisotropy, the out-of-plane coercivity (Hc⊥), in-plane coercivity (Hc//), saturation magnetization (Ms), out-of-plane squareness (S⊥), and in-plane squareness (S//) values of this film are 18 kOe, 12.2 kOe, 388 emu/cm3, 0.93, and 0.42, respectively.
On the other hand, the magnetic properties of CoPt-SiNx / Ag films are strong dependent on the different sputtering methods. The I001 /I111 ratio increases from 0.92 of to 1.24 as the film structure changed from CoPt-SiNx / Ag to ( CoPt-SiNx / CoPt )9 / Ag. After annealing at 700°C for 30 minutes, ( CoPt-SiNx / CoPt )9 / Ag film shows the best perpendicular anisotropy, the Hc⊥, Hc//, Ms, S⊥, and S// values of this film are 16.3 kOe, 14.6 kOe, 295 emu/cm3, 0.8, and 0.44, respectively.
Moreover, after annealing, the perpendicular anisoyropy of ( CoPt-SiNx / CoPt )9 / Ag film will be broken as the SiNx is added. However, as the SiNx content increases, the perpendicular magnetic anisotropy of this film can be obtained due to the formation of vacancies which result from the diffusion of SiNx from grain to grain boundary. As the SiNx content increases to 46.2 vol.%, some CoPt grains are smaller than the superparamagnetism particle size and causes the rapidly decrease of the coercivity.
Finally, we add the Ag element into (CoPt)53.8(SiNx)46.2/Ag (30 nm) films to form the [(CoPt)53.8(SiNx)46.2]1-y Agy /Ag (30 nm) films, in attempt to lower the ordering temperature of this film. From the experiment results, the ordering temperature of the film will decrease from 600°C to 500°C as Ag is added. As the addition of Ag content increases, the perpendicular anisotropy will be reduced. After annealing at 600°C for 30 minutes, the [(CoPt)53.8(SiNx)46.2]40.8Ag59.2/Ag (30 nm) film shows the best perpendicular anisotropy, the Hc⊥, Hc//, Ms, S⊥, and S// values of this film are 9.6 kOe, 5.5 kOe, 127 emu/cm3, 0.75, and 0.49, respectively.

並列關鍵字

CoPt film ； granular structure ； ordering temperature ； perpendicular magnetic properties ； Ag underlayer

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