Air Stable Doping and Intrinsic Mobility Enhancement in Monolayer Molybdenum Disulfide by Amorphous Titanium Suboxide Encapsulation Amritesh Rai 1 * , Amithraj Valsaraj 1 , Hema C.P. Movva 1 , Anupam Roy 1 , Rudresh Ghosh 1 , Sushant Sonde 1 , Sangwoo Kang 1 , Jiwon Chang 2 , Tanuj Trivedi 1 , Rik Dey 1 , Samaresh Guchhait 1 , Stefano Larentis 1 , Leonard F. Register 1 , Emanuel Tutuc 1 , and Sanjay K. Banerjee 1 1 Microelectronics Research Center & Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA 2 SEMATECH, 257 Fuller Rd #2200, Albany, NY-12203, USA * Correspondence e-mail: amritesh557@utexas.edu Abstract: 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-κ oxides, respectively. The goal of this work is to demonstrate a high-κ dielectric that serves as an effective n-type charge transfer dopant on monolayer (ML) molybdenum disulfide (MoS2). Utilizing amorphous titanium suboxide (ATO) as the ‘high-κ dopant’, we achieved a contact resistance of ~ 180 Ω·μm which is the lowest reported value for ML MoS2. An ON current as high as 240 μA/μm and field effect mobility as high as 83 cm 2 /V-s were realized using this doping technique. Moreover, intrinsic mobility as high as 102 cm 2 /V-s at 300 K and 501 cm 2 /V-s at 77 K were achieved after ATO encapsulation which are among the highest mobility values reported on ML MoS2. We also analyzed the doping effect of ATO films on ML MoS2, a phenomenon which is absent when stoichiometric TiO2 is used, using ab initio density functional theory (DFT) calculations which shows excellent agreement with our experimental findings. Based on the interfacial-oxygen-vacancy mediated doping as seen in the case of high-κ ATO – ML MoS2, we propose a mechanism for the mobility enhancement effect observed in TMD-based devices after encapsulation in a high-κ dielectric environment. Keywords: Molybdenum disulfide (MoS2), field effect transistor, Schottky barrier, contact resistance, high-κ dielectric, amorphous titanium suboxide (ATO), doping, intrinsic mobility