二硫化錫/氮化硼異質結構之基板效應與金屬-絕緣體相變化現象

Substrate effect and metal-insulator transition in SnS2/h-BN heterostructure

劉議仁(Yi-Ren Liu)

指導教授 ： 簡紋濱

國立交通大學/理學院/電子物理系所/碩士(2019年)

摘要

近年來二維層狀材料因獨特的物理特性與載子傳輸特性，而成為科學界爭相研究的熱門題材。過去人們以二氧化矽/矽(SiO2/Si)作為基板，製作二維層狀材料之場效電晶體電子元件，用以觀測物理與電特性。近期許多研究指出，二氧化矽含晶格缺陷易誘發p型參雜效應，影響二維層狀材料的電子傳輸行為。因此，本實驗利用晶格缺陷少的氮化硼(h-BN)取代二氧化矽/矽之基板，製作出二維層狀材料-二硫化錫之場效電晶體元件，觀測介面缺陷態對二硫化錫元件電子傳輸行為的影響，及不同基板與二硫化錫間的交互作用力對能帶造成的變化。
本實驗使用機械剝離法，將二硫化錫轉印至二氧化矽/矽或氮化硼基板上製備成場效電晶體元件，比較不同基板上之元件電性傳輸的差異性。由於不同基板的缺陷態對二硫化錫的交互作用力不同，元件的蕭特基位障有明顯差異。此外，在低溫電性傳輸方面，本實驗利用次臨界擺幅SS與電容關係計算介面陷阱濃度DIT，又以Mott二維變程跳躍傳輸理論擬合電阻-溫度曲線，計算出無序性特徵溫度T0以判斷系統之無序程度，結果均顯示本質缺陷較少的氮化硼基板，能提供元件更良好的傳輸環境。最後由於氮化硼基板顯著的降低了二硫化錫元件之無序性，使得二硫化錫的金屬-絕緣體相變化行為能被觀測到，並針對相變化的臨界載子濃度與臨界通道電場進行討論。

關鍵字

二硫化錫 ； 氮化硼 ； 基板效應 ； 場效電晶體 ； 電性傳輸行為 ； 金屬-絕緣體相變化

並列摘要

Two-dimensional (2D) materials, showing new physics and novel electron transport properties, have attracted significant interests in recent years. 2D materials are usually placed on SiO2/Si substrate for the fabrication of electronic devices. However, some recent studies indicated that the SiO2 substrate may possess lattice defects, inducing an p-type doping effect. Such doping will influence electron transport properties in electronic devices based on 2D materials.
To explore the effect from the interface defect states, we put the 2D material of SnS2 flakes on either SiO2/Si or h-BN substrate and make back-gated field effect transistor (FET) devices. The electrical properties of those devices are measured in the temperature range from 300 K to 80 K. Devices on the two different substrates reveal different Schottky barrier height possibly due to different interaction between the channel and the interface trap states. In addition, the electron transport of the SnS2 FET devices on the two different substrates reveals different characteristic temperature (T0), which can be estimated from fitting the temperature dependent resistance by the Mott’s 2D variable range hopping transport theory. On the other hand, the interface trap density can be evaluated from the gating voltage dependence of the subthreshold swing. The data point out the dependency between the SnS2 band structure and the interface trap states from the substrates. For the SnS2 FET devices on the h-BN substrate, we observe metal-insulator transition due to much fewer interface trap states in h-BN.

並列關鍵字

SnS2 ； h-BN ； substrate effect ； field effect transistor ； electrical transport properties ； metal-insulator transition

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