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C: Energy Conversion and Storage; Energy and Charge Transport 2
Defect-Free Copolymer Gate Dielectrics for Gating MoS Transistors Min Je Kim, Yongsuk Choi, Jihoo Seok, Sungjoo Lee, Young-Jun Kim, Jun Young Lee, and Jeong Ho Cho J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b03092 • Publication Date (Web): 18 May 2018 Downloaded from http://pubs.acs.org on May 18, 2018
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The Journal of Physical Chemistry
Defect-Free Copolymer Gate Dielectrics for Gating MoS2 Transistors Min Je Kim,†a Yongsuk Choi,†a Jihoo Seok,b Sungjoo Lee,a Young Jun Kim,*a Jun Young Lee,*b Jeong Ho Cho*ab a
SKKU Advanced Institute of Nanotechnology (SAINT), bSchool of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Korea. *J. H. Cho (
[email protected]), J. Y. Lee (
[email protected]), and Y. J. Kim (
[email protected]) †
M. J. Kim and Y. S. Choi contributed equally this work.
ABSTRACT In this study, the poly(2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane-co-cyclohexyl methacrylate) [p(V4D4-co-CHMA)] copolymer was developed for use as a gate dielectric in MoS2 fieldeffect transistors (FETs). The p(V4D4-co-CHMA) copolymer was synthesized via the initiated chemical vapor deposition (iCVD) of two types of monomers: V4D4 and CHMA. Four vinyl groups of V4D4 monomers and cyclohexyl groups of CHMA monomers were introduced to enhance the electrical strength of gate dielectrics through the formation of a highly crosslinked network and to reduce the charge trap densities at the MoS2–dielectric interface, respectively. The iCVD-grown p(V4D4-co-CHMA) copolymer films yielded a dielectric constant of 2.3 and a leakage current of 3.8 × 10-11 A/cm2 at 1 MV/cm. The resulting MoS2 FETs with p(V4D4-co-CHMA) gate dielectrics exhibited excellent electrical properties, including an electron mobility of 35.1 cm2/Vs, a subthreshold swing of 0.2 V/dec, and an on-off current ratio of 2.6 × 106. In addition, the environmental and operational stabilities of MoS2 FETs with p(V4D4-co-CHMA) top-gate dielectrics were superior to those of devices with SiO2 back-gate dielectrics. The use of iCVD-grown copolymer gate dielectrics as demonstrated in this study provides a novel approach to realizing nextgeneration two-dimensional electronics.
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INTRODUCTION Molybdenum disulfide (MoS2), one of the most widely investigated two-dimensional (2D) transition metal dichalcogenide (TMDC) compounds, has attracted significant attention owing to its distinct bandgap and atomic thickness.1-8 MoS2 possesses a direct bandgap of 1.8 eV as a monolayer and an indirect bandgap of 1.3 eV in its bulk form, which enables its application in advanced optoelectronic devices that operate at visible wavelengths.1,
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The ultrathin thickness of the MoS2 active channel in transistors enables more
efficient electrostatic control over the channel than that achieved using bulk materials.5, 8-9 These beneficial characteristics make MoS2 a promising candidate for a semiconducting channel material in next-generation nanoscale electronic and optoelectronic applications. Therefore, MoS2 has been applied to various electronic devices, including field-effect transistors (FETs),5, 8-9 photodetectors,10-12 sensors,13-14 and memories.15-16 For example, FETs based on mechanically exfoliated MoS2 yielded an electron mobility of >10 cm2/Vs, an onoff current ratio of >107, and a low subthreshold swing of 1000 A/W at an optical power of 1.3 W/m2 and a fast response time of
