Role of Hole Trap Sites in MoS2 for Inconsistency in Optical and Electrical Phenomena

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Title
Role of Hole Trap Sites in MoS2 for Inconsistency in Optical and Electrical Phenomena
Author(s)
Minh Dao Tran; Ji-Hee Kim; Hyun Kim; Manh-Ha Doan; Dinh Loc Duong; Young Hee Lee
Publication Date
2018-03
Journal
ACS APPLIED MATERIALS & INTERFACES, v.10, no.12, pp.10580 - 10586
Publisher
AMER CHEMICAL SOC
Abstract
Because of strong Coulomb interaction in two-dimensional van der Waals-layered materials, the trap charges at the interface strongly influence the scattering of the majority carriers and thus often degrade their electrical properties. However, the photogenerated minority carriers can be trapped at the interface, modulate the electron-hole recombination, and eventually influence the optical properties. In this study, we report the role of the hole trap sites on the inconsistency in the electrical and optical phenomena between two systems with different interfacial trap densities, which are monolayer MoS2-based field-effect transistors (FETs) on hexagonal boron nitride (h-BN) and SiO2 substrates. Electronic transport measurements indicate that the use of h-BN as a gate insulator can induce a higher n-doping concentration of the monolayer MoS2 by suppressing the free-electron transfer from the intrinsically n-doped MoS2 to the SiO2 gate insulator. Nevertheless, optical measurements show that the electron concentration in MoS2/SiO2 is heavier than that in MoS2/h-BN, manifested by the relative red shift of the A1g Raman peak. The inconsistency in the evaluation of the electron concentration in MoS2 by electrical and optical measurements is explained by the trapping of the photogenerated holes in the spatially modulated valence band edge of the monolayer MoS2 caused by the local strain from the SiO2/Si substrate. This photoinduced electron doping in MoS2/SiO2 is further confirmed by the development of the trion component in the power-dependent photoluminescence spectra and negative shift of the threshold voltage of the FET after illumination. © 2018 American Chemical Society
URI
https://pr.ibs.re.kr/handle/8788114/4736
ISSN
1944-8244
Appears in Collections:
Center for Integrated Nanostructure Physics(나노구조물리 연구단) > Journal Papers (저널논문)
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