Air Stable Doping and Intrinsic Mobility Enhancement in Monolayer Molybdenum Disulfide by Amorphous Titanium Suboxide Encapsulation

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• 作者：Amritesh Rai ; Amithraj Valsaraj ; Hema C.P. Movva ; Anupam Roy ; Rudresh Ghosh ; Sushant Sonde ; Sangwoo Kang ; Jiwon Chang ; Tanuj Trivedi ; Rik Dey ; Samaresh Guchhait ; Stefano Larentis ; Leonard F. Register ; Emanuel Tutuc ; Sanjay K. Banerjee
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：July 8, 2015
• 年：2015
• 卷：15
• 期：7
• 页码：4329-4336
• 全文大小：525K
• ISSN：1530-6992

文摘

To reduce Schottky-barrier-induced contact and access resistance, and the impact of charged impurity and phonon scattering on mobility in devices based on 2D transition metal dichalcogenides (TMDs), considerable effort has been put into exploring various doping techniques and dielectric engineering using high-魏 oxides, respectively. The goal of this work is to demonstrate a high-魏 dielectric that serves as an effective n-type charge transfer dopant on monolayer (ML) molybdenum disulfide (MoS₂). Utilizing amorphous titanium suboxide (ATO) as the 鈥渉igh-魏 dopant鈥? we achieved a contact resistance of 鈭?80 惟路渭m that is the lowest reported value for ML MoS₂. An ON current as high as 240 渭A/渭m and field effect mobility as high as 83 cm²/V-s were realized using this doping technique. Moreover, intrinsic mobility as high as 102 cm²/V-s at 300 K and 501 cm²/V-s at 77 K were achieved after ATO encapsulation that are among the highest mobility values reported on ML MoS₂. We also analyzed the doping effect of ATO films on ML MoS₂, a phenomenon that is absent when stoichiometric TiO₂ is used, using ab initio density functional theory (DFT) calculations that shows excellent agreement with our experimental findings. On the basis of the interfacial-oxygen-vacancy mediated doping as seen in the case of high-魏 ATO鈥揗L MoS₂, we propose a mechanism for the mobility enhancement effect observed in TMD-based devices after encapsulation in a high-魏 dielectric environment.