Employing a Bifunctional Molybdate Precursor To Grow the Highly Crystalline MoS 2 for High-Performance Field-Effect Transistors Shi Wun Tong,* ,† Henry Medina, † Wugang Liao, ‡,§ Jing Wu, † Wenya Wu, † Jianwei Chai, † Ming Yang, † Anas Abutaha, † Shijie Wang, † Chunxiang Zhu, § Kedar Hippalgaonkar, † and Dongzhi Chi* ,† † Institute of Materials Research and Engineering, Agency for Science Technology and Research, 2 Fusionopolis Way, #08-03 Innovis, 138634, Singapore ‡ College of Electronic Science and Technology, Shenzhen University, Shenzhen 518060, China § Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore * S Supporting Information ABSTRACT: Growth of the large-sized and high-quality MoS 2 single crystals for high-performance low-power electronic applications is an important step to pursue. Despite the significant improvement made in minimizing extrinsic MoS 2 contact resistance based on interfacial engineering of the devices, the electron mobility of field-effect transistors (FETs) made of a synthetic monolayer MoS 2 is yet far below the expected theoretical values, implying that the MoS 2 crystal quality needs to be further improved. Here, we demonstrate the high-performance two-terminal MoS 2 FETs with room-temperature electron mobility up to ∼90 cm 2 V -1 s -1 based on the sulfurization growth of the bifunctional precursor, sodium molybdate dihydrate. This unique transition-metal precursor, serving as both the crystalline Mo source and seed promotor (sodium), could facilitate the lateral growth of the highly crystalline monolayer MoS 2 crystals (edge length up to ∼260 μm). Substrate surface treatment with oxygen plasma prior to the deposition of the Mo precursor is fundamental to increase the wettability between the Mo source and the substrate, promoting the thinning and coalescence of the source clusters during the growth of large-sized MoS 2 single crystals. The control of growth temperature is also an essential step to grow a strictly monolayer MoS 2 crystal. A proof-of- concept for thermoelectric device integration utilizing monolayer MoS 2 sheds light on its potential in low-voltage and self- powered electronics. KEYWORDS: molybdenum disulfide, molybdate precursor, seed promotor, field-effect transistor, thermoelectric 1. INTRODUCTION Silicon (Si)-based field-effect transistors (FETs) are the prevailing building blocks as pixel switches in flat-panel displays. It is feasible to integrate high-performance FETs with 50-90 nm thick Si (field-effect mobility of >150 cm 2 V -1 s -1 and ON/OFF ratio of ∼10 6 ) 1,2 into driver circuits for high- resolution displays. The short-channel effects, however, are severe in the scaled-down Si FETs, which hampers the utility of a few-nanometer-thick Si channel transistor in flexible electronics. 3 Atomically thin monolayer molybdenum disul- phide (MoS 2 ), one of the most widely studied layer-structured semiconducting transition-metal dichalcogenides (TMDs), has emerged as a potential channel material in the low-power downscaled digital electronic devices owing to its favorable physical and electronic properties, including its high theoretical electron mobility μ e (μ e ≈ 410 cm 2 V -1 s -1 was calculated for monolayer MoS 2 ), 4 relatively large band gap of ∼1.8 eV 5,6 (responsible for a high ON/OFF current ratio of ∼10 8 achieved in exfoliated MoS 2 -FETs), 7 immunity to short channel effect (due to an atomically thin nature), 8, 9 Received: January 23, 2019 Accepted: March 28, 2019 Published: March 28, 2019 Research Article www.acsami.org Cite This: ACS Appl. Mater. Interfaces 2019, 11, 14239-14248 © 2019 American Chemical Society 14239 DOI: 10.1021/acsami.9b01444 ACS Appl. Mater. Interfaces 2019, 11, 14239-14248 Downloaded via NANYANG TECHNOLOGICAL UNIV on September 2, 2021 at 07:38:37 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.