探討二維材料-金屬介面分析及接觸電阻之改良

Investigation of Two-Dimensional Materials-Metal Interfaces and Improvement of Contact Resistance

洪堇莉(Chin-Li Hung)

指導教授 ： 吳志毅

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201803346

摘要

為了符合現今人類需求，半導體微縮製程的極限，使其朝往結構的改變以及通道材料的開發兩大方向，因此，各團體對二維材料的研究開始興起。然而當元件線寬逐漸縮小，金屬與材料間的接觸對整體元件特性表現影響甚大，因此，解決金屬與二維材料介面的接觸問題是非常重要的。
本研究分為兩部分進行深入研究。第一部分，我們研發出N/P型溶液摻雜石墨烯的方式來增加石墨烯之態密度以降低金屬與石墨烯介面的接觸電阻，並以氟化銫(CsF)及三氧化鉬(MoO3)作為摻雜物。為了確認摻雜物對石墨烯的摻雜影響，我們不僅使用光電子能譜分析其表面的電荷轉移情況，在電特性上亦以石墨烯場效電晶體的狄拉克點位移、載子遷移率等來做分析。接著，我們利用傳輸線模型(TLM)來檢測已摻雜之石墨烯與金屬之接觸電阻。我們獲得最好的結果顯示N型摻雜以鈦作為電極其接觸電阻為264.0 (Ω·μm)；P型摻雜以金作為電極其接觸電阻則為58.6 (Ω·μm)。證實無論利用摻雜石墨烯或是選用合適功函數金屬電極的方式皆能夠大幅度的降低石墨烯與金屬間的接觸電阻，優化介面。
第二部分，我們證實了藉由加入石墨烯作為金屬與二硫化鉬介面的緩衝層可以有效的減緩金屬與二硫化鉬間接觸的問題。加入石墨烯後，二硫化鉬電晶體其電特性包含載子遷移率與開關比都有大幅度的提升。因此我們以定性的方式證實加入石墨烯作為緩衝層能夠有效的優化金屬與二硫化鉬介面。

關鍵字

石墨烯 ； 二硫化鉬 ； 溶液摻雜 ； 氟化銫 ； 三氧化鉬 ； 介面分析 ； 接觸電阻

並列摘要

Two-dimensional(2D) materials has begun to emerge. However, as the devices line width shrinks, the contact between metal/ 2D materials has a significant effect to the devices performance.
In this study, the topic can be divided into two parts. In the first part, with the aim of reducing the contact resistance between the graphene/metal interface, we developed the N/P type solution doping method to extend the conduction states of graphene. Herein, dissolvable compounds of cesium fluoride(CsF) and molybdenum trioxide(MoO3) were used as N/P type dopant. The doping effect was not only analyzed by X-ray photoelectron spectroscopy(XPS) and ultraviolet photoelectron spectroscopy(UPS) but was also electrically confirmed by the shift of dirac point in graphene field effect transistors(FET) . Transfer Length Method(TLM) was used to examine the contact resistance between the doped graphene and different metal electrode(Ti and Au) interfaces. For the N type dopant, the best results shows that the contact resistance between CsF doped graphene and Ti electrode is 264.0 (Ω·μm). For the P type dopant, the best results shows that the contact resistance between MoO3 doped graphene and Au electrode is 58.6 (Ω·μm). We confirmed that the interface between graphene and metal can be optimized by solution doping graphene and suitable metal electrode choosing.
In the second part, we demonstrated that the contact issues between molybdenum disulfide(MoS2) and electrode could be alleviated graphene as a buffer layer. With graphene/Ag as electrode,MoS2 FET performance is significantly improved .We confirmed that the interface of MoS2 and metal can be optimized by graphene insertion between metal and MoS2.

並列關鍵字

Graphene ； Molybdenum disulfide(MoS2) ； solution doping ； Cesium fluoride(CsF) ； molybdenum trioxide(MoO3) ； interface analysis ； contact resistance

參考文獻

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