二維材料場效電晶體之製作及其光電/傳輸特性

Fabrication and optoelectronic/transport properties of two-dimensional-material field-effect transistors

施甫諭(Fu-Yu Shih)

指導教授 ： 陳永芳

共同指導教授 ： 王偉華(Wei-Hua Wang)

國立臺灣大學/理學院/物理學研究所/博士(2016年)

https://doi.org/10.6342/NTU201600247

摘要

本篇論文的研究主軸是提供二維材料電晶體的特殊製程以及探討二維材料光電傳輸特性。近十年以來，二維材料是發展相當迅速的新穎奈米材料，它擁有許多獨特的性質，比如說：半金屬二維材料-石墨烯(graphene)擁有極高的載子遷移率、半導體二維材料-二硫化鉬(MoS2)的能隙會隨著層數的不同而改變，這些材料特性有助於科學家去研發設計新型態電晶體或光電元件的應用。在文章中，我們將研究分成三個區塊
首先．我們研發一套新穎、無光阻殘留技術的特殊元件製程來製作多點電極二維材料電晶體，利用聚酸甲酯(PMMA)當作薄膜蒸鍍罩，並結合電子束微影技術設計客製化薄膜蒸鍍罩的樣式。在此製程下所製作的高品質石墨烯電晶體展現許多石墨烯的電子傳輸本質特性，像是量子霍爾效應。那些無法使用顯影製程的材料，將可透過此技術來製作元件。
第二，石墨烯的高載子遷移率特性適合用在光偵測器，但石墨烯的低吸收效率卻限制其光電元件的表現行為。為此，我們專注於改善石墨烯光偵測器的低響應限制。藉由感光生物材料-葉綠素的修飾，將石墨烯光偵測器的光感應效率提升109倍。此研究為未來的綠能源研究提出一個可評估的方向。
最後，我們系統性地探討二硫化鉬橫向接面電晶體的光電流傳輸特性。在不同層數的二硫化鉬接面中，存在一個由不同二硫化鉬能隙而產生的內建電場。有趣的事情是，由內建電場產生的自供電光電流有著與環境無關的特性，本文會進一步討論其機制。此研究對於半導體二維材料橫向接面提供進一步的了解，並其光電元件的應用。

關鍵字

二維材料 ； 石墨烯 ； 二硫化鉬 ； 無光阻技術製程 ； 場效電晶體 ； 光偵測器 ； 光電傳輸特性

並列摘要

Two-dimensional (2D) materials such as graphene and MoS2 have attracted intense attention due to their remarkable properties. High carrier mobility of graphene and tunable bandgap of 2D semiconductor are kinds of significant and interesting properties for researcher to design potential electronic or optoelectronic application. In this thesis, we have devoted to study in the following three goals.
Firstly, we aim to develop a simple, novel and residue-free technique that allows for the fabrication of multi-probe metal contacts on 2D materials. We fabricate a stencil mask consisted of thin film of poly (methyl methacrylate) (PMMA), which is patterned by e-beam lithography. When we use this technique to fabricate graphene device and demonstrate high quality of graphene field-effect transistors by observation of smooth graphene surfaces and distinct transport/magnetotransport behavior. The feasibility of this stencil-mask technique offer the versatile fabrication of 2D material devices.
Then, we focus on identifying the issue of low absorption rate in graphene, which limit the performance of graphene transistors in photodetector application. Here, we demonstrate novel solutions to overcome ultralow response of graphene-based photodetector, by the integration of light-absorbing materials in graphene transistors. The result shows that the hybrid graphene-organic molecule transistors with high photosensitivity is promising insight for the development of graphene-based optoelectronics.
Finally, we demonstrate a systematic photoresponse study in novel structure of 2D semiconducting material. Based on the existence of discontinuities in energy bands from different layers of TMDCs materials, we observed built-in electric field induced photovoltaic current in layer-modified MoS2 junction. Interestingly, photovoltaic current exhibits environment-insensitive and field-effect controllable and the mechanisms are discussed in the thesis. This study extends the understanding of optoelectronic properties in layer-modified 2D semiconducting material junction.

並列關鍵字

two-dimensional materials ； graphene ； molybdenum disulphide ； resist-free fabrication ； field effect transistor ； photodetector ； optoelectronic properties

參考文獻

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