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Title: Charge neutral MoS 2 field effect transistors through oxygen plasma treatment

Lithographically fabricated MoS 2 field effect transistors suffer from several critical imperfections, including low sub-threshold swings, large turn-on gate voltages (V T), and wide device-to-device variability. The large magnitude and variability of V T stems from unclean interfaces, trapped charges in the underlying substrate, and sulfur vacancies created during the mechanical exfoliation process. In this work, we demonstrate a simple and reliable oxygen plasma treatment, which mitigates the effects of unintentional doping created by surface defect sites, such as S vacancies, and surface contamination. This plasma treatment restores charge neutrality to the MoS 2 and shifts the threshold turn-on voltage towards 0 V. Out of the 10 devices measured, all exhibit a shift of the FET turn-on voltage from an average of -18 V to -2 V. The oxygen plasma treatment passivates these defects, which reduces surface scattering, causing increased mobility and improved subthreshold swing. For as-prepared devices with low mobilities (~0.01 cm 2/V s), we observe up to a 190-fold increase in mobility after exposure to the oxygen plasma. Perhaps the most important aspect of this oxygen plasma treatment is that it reduces the device-to-device variability, which is a crucial factor in realizing any practical application of these devices.
Authors:
 [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering
  2. XEI Scientific, Inc., Redwood City, CA (United States)
Publication Date:
Grant/Contract Number:
FG02-07ER46376; 1402906
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 19; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Southern California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; materials properties; carrier mobility; optoelectronic devices; band gap; plasma materials processing; monolayers; surface scattering; vacancies; field effect transistors
OSTI Identifier:
1465120
Alternate Identifier(s):
OSTI ID: 1332764

Dhall, Rohan, Li, Zhen, Kosmowska, Ewa, and Cronin, Stephen B. Charge neutral MoS2 field effect transistors through oxygen plasma treatment. United States: N. p., Web. doi:10.1063/1.4967398.
Dhall, Rohan, Li, Zhen, Kosmowska, Ewa, & Cronin, Stephen B. Charge neutral MoS2 field effect transistors through oxygen plasma treatment. United States. doi:10.1063/1.4967398.
Dhall, Rohan, Li, Zhen, Kosmowska, Ewa, and Cronin, Stephen B. 2016. "Charge neutral MoS2 field effect transistors through oxygen plasma treatment". United States. doi:10.1063/1.4967398. https://www.osti.gov/servlets/purl/1465120.
@article{osti_1465120,
title = {Charge neutral MoS2 field effect transistors through oxygen plasma treatment},
author = {Dhall, Rohan and Li, Zhen and Kosmowska, Ewa and Cronin, Stephen B.},
abstractNote = {Lithographically fabricated MoS2 field effect transistors suffer from several critical imperfections, including low sub-threshold swings, large turn-on gate voltages (VT), and wide device-to-device variability. The large magnitude and variability of VT stems from unclean interfaces, trapped charges in the underlying substrate, and sulfur vacancies created during the mechanical exfoliation process. In this work, we demonstrate a simple and reliable oxygen plasma treatment, which mitigates the effects of unintentional doping created by surface defect sites, such as S vacancies, and surface contamination. This plasma treatment restores charge neutrality to the MoS2 and shifts the threshold turn-on voltage towards 0 V. Out of the 10 devices measured, all exhibit a shift of the FET turn-on voltage from an average of -18 V to -2 V. The oxygen plasma treatment passivates these defects, which reduces surface scattering, causing increased mobility and improved subthreshold swing. For as-prepared devices with low mobilities (~0.01 cm2/V s), we observe up to a 190-fold increase in mobility after exposure to the oxygen plasma. Perhaps the most important aspect of this oxygen plasma treatment is that it reduces the device-to-device variability, which is a crucial factor in realizing any practical application of these devices.},
doi = {10.1063/1.4967398},
journal = {Journal of Applied Physics},
number = 19,
volume = 120,
place = {United States},
year = {2016},
month = {11}
}

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