第一原理與蒙地卡羅法應用於二維過渡金屬雙硫化物傳輸特性之研究

Study of Intrinsic Transport Properties in 2D Transition Metal Dichalcogenide by First-principle Method and Monte Carlo Analysis

白修齊(Hsiu-Chi Pai)

指導教授 ： 吳育任

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202788

摘要

本研究利用第一原理計算能帶、有效質量、電聲散射率與形變常數等重要之材料基本參數，結合蒙地卡羅法開發出能有效預測二維材料電子遷移率的計算模型，並針對常見之過渡金屬雙硫屬化物進行傳輸特性的探討。在電子能帶中，K能谷與Q能谷間的能量差是影響過渡金屬雙硫屬化物傳輸特性的重要因素，儘管現階段尚無實驗能夠證實此能量差的確切數值，我們透過蒙地卡羅法發現，其在130至150 meV之間可能存在著一臨界值，對於低電場下的電子遷移率會有顯著的影響。另外，我們也針對近年來崛起的非對稱型（Janus）過渡金屬雙硫屬化物（MoSSe和WSSe）進行傳輸特性的預測。與傳統對稱的過渡金屬雙硫屬化物相比，MoSSe與WSSe在傳輸特性上不僅擁有一定的競爭力，更因其先天產生的內建電場，使之能透過單一種電極材料來同時實現n型與p型的接觸行為，進而達到更低的蕭基能障甚至歐姆接觸。

關鍵字

第一原理計算 ； 密度泛涵理論 ； 蒙地卡羅法 ； 二維材料 ； 電子遷移率

並列摘要

We investigate the intrinsic transport properties in two-dimensional (2D) transition metal dichalcogenide (TMD) by the first principle theory and Monte Carlo transport treatment. The electron-phonon and field-dependent transport properties of new class 2D materials -- Janus TMDs (MoSSe and WSSe) are systematically analyzed in this study for the first time. Both the Janus MoSSe and WSSe show competitive transport performances compared to traditional TMDs, and their strong intrinsic dipole fields enable the formation of depletion field inside the material at the same time, which is similar to depletion region induced by pn junction. The crucial factor for the transport properties appears to be the energy separations between the K and Q valleys at the conduction band since it causes intervalley electron scattering. We quantitatively predict that there exists a threshold value for the energy separation that could significantly affect the low-field transport performances.

並列關鍵字

First-principle ； Density functional theory ； Monte Carlo simulation ； Two-dimensional material ； Mobility

參考文獻

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