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Issue 11, 2019
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Surface functionalization-induced photoresponse characteristics of monolayer MoS2 for fast flexible photodetectors

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Abstract

Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving a fast photoresponse time in MoS2 photodetectors. In this study, we investigate the importance of surface functionalization on controlling the charge carrier densities in a MoS2 monolayer and in turn the corresponding behavior of the photoresponse in relation to the position of the Fermi-level and the energy band structure. We find that the p-doping and n-doping, which is achieved through the surface functionalization of the MoS2 monolayer, leads to devices with different photoresponse behavior. Specifically, the MoS2 devices with surface functional groups contributing to p-doping exhibited a faster response time as well as higher sensitivity compared to that observed for the MoS2 devices with surface functional groups contributing to n-doping. We attribute this difference to the degree of bending in the energy bands at the metal–semiconductor junction as a result of shifting in the Fermi-level position, which influences the optoelectronic transport properties as well as the recombination dynamics leading to a low dark and thus high detectivity and fast decay time. Based upon these findings, we have also demonstrated the broad applicability of surface functionalization by fabricating a flexible MoS2 photodetector that shows an outstanding decay time of 0.7 s, which is the fastest response time observed in flexible MoS2 detectors ever reported.

Graphical abstract: Surface functionalization-induced photoresponse characteristics of monolayer MoS2 for fast flexible photodetectors

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Publication details

The article was received on 02 Nov 2018, accepted on 26 Feb 2019 and first published on 27 Feb 2019


Article type: Communication
DOI: 10.1039/C8NR07655C
Nanoscale, 2019,11, 4726-4734

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    Surface functionalization-induced photoresponse characteristics of monolayer MoS2 for fast flexible photodetectors

    S. Pak, A. Jang, J. Lee, J. Hong, P. Giraud, S. Lee, Y. Cho, G. An, Y. Lee, H. S. Shin, S. M. Morris, S. Cha, J. I. Sohn and J. M. Kim, Nanoscale, 2019, 11, 4726
    DOI: 10.1039/C8NR07655C

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