利用垂直異向性電極研究橫向自旋閥單層二硒化鎢通道和接觸的電學特性

Investigation on Electrical Properties of Monolayer Tungsten Diselenide Channel and Contact through Lateral Spin Valve with Perpendicular Magnetic Anisotropy Electrodes

蕭俊彥(Jyun-Yan Siao)

指導教授 ： 林敏聰

國立臺灣大學/理學院/物理學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201904421

摘要

近十年來，二維過渡金屬二硫化物引起了人們的興趣。其額外的能谷自由度可以與電子自旋自由度耦合，使得能谷-自旋電子元件可能被實現。然而，由於鐵磁金屬和半導體之間的接觸，將導致電導失配問題，使得通過電接觸的自旋傳輸仍然具有挑戰性。而接觸電阻是實現對二維過渡金屬半導體注入電子自旋的關鍵，其大小由金屬和半導體之間的界面特性決定。當接觸電阻數值落在優化範圍內，將有利於通過電接觸實現自旋傳輸。

在本論文中，我們主要製作了兩種WSe2-FET 橫向自旋閥，一種是正向結構，另一種是倒置結構。此外，接觸電極是由多層鈷/鉑組成，它是一種具有垂直磁向異性（PMA）的電極。在未來的研究中，此種電極可用於注入和檢測單層二硒化鎢通道中的電子自旋。透過濺鍍沉積多層鈷/鉑電極，並且在室溫下使用我們自架的P-MOKE系統測量它們的磁性。單層二硒化鎢和六方氮化硼是使用PDMS透過機械剝離方式來製備，然後再轉移到SiO2(300nm)/Si或預先沉積好的垂直磁異性電極上。在其中兩個元件裡，我們從橫向自旋閥的IV量測中，得到了某些柵極電壓下的蕭基特位壘高度。我們也製作了一些有潛力的WSe2-FET橫向自旋閥，實驗結果顯示這些結構是有機會在未來被用來進行自旋傳輸研究的結構。

關鍵字

能谷電子學 ； 二維材料 ； 過渡金屬硫屬化物 ； 二硒化鎢 ； 晶體剝離 ； 垂直磁異向性 ； 元件量測 ； 蕭基特能障

並列摘要

Two-dimension transition metal dichalcongenides (2D-TMDCs) has gained interests in recent 10 years. Its extra valley degree of freedom can couple with electron spin degree of freedom, giving the possibility to make valley-spintronic device come true. However, spin transport through the electric contact still remains challenging because of contact between ferromagnetic metal and semiconductor, resulting in conductance mismatch problem. The other key point about injecting spin into TMD semiconductor is contact resistance which is decided by the interface properties between metal and semiconductor. And optimized region value of contact resistance is beneficial to spin transport through the electric contact.

In this thesis, we mainly fabricated two categories of WSe2-FET lateral spin valve. One is the normal structure and the other one is reversed structure. In addition, the contact electrodes consist of Co/Pt multilayers, which is kind of perpendicular magnetic anisotropy (PMA) electrodes. It can be used to inject and detect spin through monolayer tungsten diselenide (WSe2) channel in the future research. Multilayers Co/Pt electrodes are deposited by sputtering and their magnetic properties are measured by our homemade polar MOKE system at room temperature. The monolayer WSe2 and hexagonal boron nitride (hBN) are prepared by mechanical exfoliation through polydimethylsiloxane (PDMS) and are transferred onto SiO2 (300nm)/Si or pre-patterned PMA electrodes afterwards. We extract Schottky barrier height from IV measurement at some certain gate voltage in two of our devices. We also fabricate some promising structure of WSe2-FET lateral spin valve. Results has shown that they're potential for future spin transport research.

並列關鍵字

Valleytronics ； 2D-materials ； transition metal dichalcongenides ； tungsten diselenide ； crystal exfoliation ； perpendicular magnetic anisotropy ； device measurement ； Schottky barrier

參考文獻

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