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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.
 [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
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 19; Journal ID: ISSN 0021-8979
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
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:
Alternate Identifier(s):
OSTI ID: 1332764