透過自組裝薄膜修飾二硫化鉬場效電晶體之電特性與電滯效應改善研究

Electrical characteristic improvement and hysteresis reduction of MoS2 FET through SAM modified substrate

蔡瑞祥(Jui-Hsiang Tsai)

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(2019年)

https://doi.org/10.6342/NTU201903791

摘要

相較於石墨烯的高載子遷移率，二硫化鉬的載子遷移率並不是很理想，這主要是因為電荷傳輸的過程中，受到外部或內部因素的影響所致，這些因素可能來自帶電雜質、陷阱或是結構缺陷，從而導致載子遷移率下降。此外，在電性量測上，我們還發現二硫化鉬場效電晶體有著嚴重的電滯現象，由於電滯是一個不理想的電性表現，因此我們也做了一些分析設法去改善它。實驗內容主要分為兩個部分，第一部分是探討閘極偏壓對電滯效應的影響，以及探討造成電滯效應的主因，並嘗試利用不同條件去減少它。我們發現基板本身內部的缺陷所造成的影響，可能遠遠超過界面的影響，而透過懸浮二硫化鉬的結構可以大幅改善電滯效應，但仍然無法完全將之消除，最後推測二硫化鉬本身的硫空缺，也是影響電滯效應的關鍵因素。而實驗第二部分則是利用一系列不同的自組裝分子修飾基板，試圖減少界面的散射源，以提升載子遷移率，實驗結果發現帶有硫醇官能基的自組裝分子能有效的提升載子遷移率，且電滯效應同時也大幅的減少，推測其可能的原因是硫醇官能基對二硫化鉬的硫空缺進行了修復所致。最後我們將帶有硫醇官能基的分子製作成雙邊自組裝層結構，類似於對二硫化鉬進行上下封裝的效果，不論是載子遷移率的提升或是電滯效應的改善都達到了最好的表現。

關鍵字

二硫化鉬 ； 機械剝離法 ； 背閘極式場效電晶體 ； 載子遷移率 ； 自組裝層 ； 電滯效應

並列摘要

Compared to the high carrier mobility of graphene, the mobility of molybdenum disulfide is not ideal, mainly due to external or internal factors in the process of charge transport. These factors may come from charged impurities, traps or structural defects, resulting in a decrease in carrier mobility. In addition, in the electrical characteristic measurement, we also found that the molybdenum disulfide field effect transistor has a serious electrical hysteresis. Since the electrical hysteresis is an unsatisfactory electrical performance, we had also done some analysis to improve it.
The experiment is divided into two parts. The first part is to explore the influence of gate bias on the hysteresis effect, and to analyze the main cause of the hysteresis effect, then try to reduce it by using different conditions. We had found that the effect of oxide traps inside the substrate may far exceed the influence of the interface. The structure of suspended molybdenum disulfide can greatly improve the hysteresis effect, but it still cannot be completely eliminated. It was speculated that the sulfur vacancy of molybdenum disulfide is also a key factor causing the hysteresis.
The second part of the experiment is to use a series of different self-assembled molecules to modify the substrate, trying to reduce the scattering source of the interface to improve the carrier mobility. The experimental results showed that the self-assembled molecules with thiol functional groups can effectively improve the carrier mobility, and the hysteresis effect was also greatly reduced. The possible reason is that the thiol functional group repairs the sulfur vacancy of molybdenum disulfide. Finally, we fabricated a double side structure with self-assembled monolayer which has thiol functional group. As the results, both the carrier mobility and the hysteresis effect have achieved the best improvement.

並列關鍵字

Molybdenum Disulfide ； Mechanical Exfoliation ； Backgated Field-Effect Transistors ； Mobility ； Self-Assembled Monolayer ； Hysteresis

參考文獻

[1] I. Ferain, C. A. Colinge, and J. P. Colinge, "Multigate transistors as the future of classical metal-oxide-semiconductor field-effect transistors," Nature, vol. 479, no. 7373, pp. 310-6, Nov 16 2011.

[2] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, "The electronic properties of graphene," Reviews of Modern Physics, vol. 81, no. 1, pp. 109-162, 2009.

[3] A. K. Geim and I. V. Grigorieva, "Van der Waals heterostructures," Nature, vol. 499, no. 7459, pp. 419-25, Jul 25 2013.

[4] Y. Liu, X. Duan, Y. Huang, and X. Duan, "Two-dimensional transistors beyond graphene and TMDCs," Chem Soc Rev, vol. 47, no. 16, pp. 6388-6409, Aug 13 2018.

[5] N. Jena, Dimple, S. D. Behere, and A. De Sarkar, "Strain-Induced Optimization of Nanoelectromechanical Energy Harvesting and Nanopiezotronic Response in a MoS2 Monolayer Nanosheet," The Journal of Physical Chemistry C, vol. 121, no. 17, pp. 9181-9190, 2017.