二維材料介面導致鐵薄膜磁耦合分離現象

Magnetic decoupling of ferromagnetic coverage across atomic step of MoS2 flakes on SiO2 surface

林宗佑(Lin Zong-You)

指導教授 ： 林文欽

國立臺灣師範大學/理學院/物理學系/碩士(2018年)

https://doi.org/10.6345/THE.NTNU.DP.007.2018.B04

摘要

本實驗旨在於探討鐵磁薄膜沉積在單層二硫化鉬(MoS2)與二氧化矽基板(SiO2 /Si(100))兩種不同表面上產生的矯頑場(coercivity)差異，其鐵薄膜具有不連續的磁耦合分離性質，並分析推測此現象的可能來源。

我們利用自製的化學氣相沉積系統(Chemical Vapor Deposition)合成大量二硫化鉬單層薄膜於二氧化矽基板，並以原子力顯微鏡(Atomic Force Microscope)、拉曼光譜儀(Raman spectrum)驗證其大多為單層的厚度結構。其後於超高真空環境(10-9 torr)蒸鍍鐵薄膜於其上，再以磁光科爾顯微鏡(magneto optical kerr mi-croscope)量測之。結果上，我們發現樣品表面的磁滯曲線(hysteresis loop)呈現非方正的鐵磁曲線，呼應我們對於鐵膜微觀表面上具有許多磁性粒子團的預測，且異質介面導致鐵薄膜在不同介面上有著相異的矯頑場，是為鐵薄膜磁耦合分離現象，此現象伴隨著鐵薄膜厚度提升而逐漸消失。

關鍵字

二硫化鉬 ； 磁性 ； 二維材料 ； 磁耦合分離

並列摘要

In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flake. The MoS2 flakes were fabricated on SiO2/Si(100) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for the protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes were of the lateral size: 10-20 µm and mostly single layer thick. Af-ter depositing 3.6-7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves of individual MoS2 flakes. Alt-hough the Fe coverage was much thicker than the MoS2 atomic step height (∼0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 was expected, the magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (Hc) was 28±5 Oe, while in contrast, the Hc of 3.6 nm Fe/SiO2 ranged 58±5 Oe. With a thicker Fe coverage, the Hc of interface converged and the magnetic de-coupling became vague to observe. The distinct interface magnetic anisotropy of Fe on different substrates could be responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observa-tions will be valuable in combining a magnetic coverage with a single layer MoS2 for the future spintronic applications.

並列關鍵字

MoS2 ； magnetism ； two-dimensional material ； magnetic decoupling

參考文獻

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