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      Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS 2 and HfO 2 High- k Dielectric

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          Abstract

          Two-dimensional layered semiconductors such as molybdenum disulfide (MoS 2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS 2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS 2 and an ultra-thin HfO 2 high- k gate dielectric. We show that the existence of sulfur vacancies at the MoS 2-HfO 2 interface is responsible for the generation of interface states with a density ( D it ) reaching ~7.03 × 10 11 cm −2 eV −1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS 2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in D it could be achieved by thermally diffusing S atoms to the MoS 2-HfO 2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS 2 devices with carrier transport enhancement.

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          Most cited references 43

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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                13 January 2017
                2017
                : 7
                Affiliations
                [1 ]Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, 117583 Singapore
                [2 ]Institute of Materials Research and Engineering, 3 Research Link , 117602 Singapore
                [3 ]Department of Materials Science and Engineering, South University of Science and Technology of China , 1088 Xueyuan Road, Shenzhen, 518055, People Republic of China
                [4 ]College of Materials Science and Engineering, Shenzhen Key Laboratory of Special Functional Materials, Nanshan District Key Lab for Biopolymer and Safety Evaluation, Shenzhen University , 3688 Nanhai Ave, Shenzhen, 518060, People Republic of China
                Author notes
                Article
                srep40669
                10.1038/srep40669
                5234002
                28084434
                Copyright © 2017, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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