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Ambipolar and Robust WSe2 Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Xu, H; Han, X; Liu, W; Liu, P; Fang, H; Li, X; Li, Z; ... Liu, H; + view all (2020) Ambipolar and Robust WSe2 Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides. Advanced Materials Interfaces , 7 (1) 10.1002/admi.201901628.

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Abstract

Transition metal oxides (TMOs) with high work function (WF) show promising properties as unipolar p‐type contacts for transition metal dichalcogenides. Here, ambipolar field‐effect transistors (FETs) enabled by bilayer WSe2 with self‐assembled TMOs (WO2.57) as contacts are reported. Systematic material characterizations demonstrate the formation of WO2.57/WSe2 heterojunctions around nanoflake edges with Se atoms substituted by O atoms after air‐exposure, while pristine properties of WSe2 almost sustain in inner domains. As‐fabricated FETs exhibit both polarities, implying WO2.57 with lowered WF at edges can serve as both the p‐type and n‐type contact for inner WSe2. Noteworthy, greatly reduced contact resistance and enhanced channel current are achieved, compared to the devices without WO2.57 contacts. Linear drain–source current relationship from 77 to 300 K indicates the ohmic contact between edge WO2.57 and inner WSe2. Density functional theory calculations further reveal that the WO2.57/WSe2 heterojunction forms a barrier‐less charge distribution. These nm‐scale FETs possess remarkable electrical conductivity up to ≈2600 S m−1, ultra‐low leakage current down to ≈10−12 A, robustness for high voltage operation, and air stability, which even outperform pristine WSe2 FETs. Theoretical calculations reveal that the high conductivity is exclusively attributed to the air‐induced WO2.57 and its further carrier injection to WSe2.

Type: Article
Title: Ambipolar and Robust WSe2 Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides
DOI: 10.1002/admi.201901628
Publisher version: http://dx.doi.org10.1002/admi.201901628
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: density functional theory field‐effect transistors self‐passivation WOx WSe2
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office
URI: https://discovery.ucl.ac.uk/id/eprint/10090262
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