Controllable Wide-range n- and p-Doping of Monolayer Group 6 Transition-metal Disulfides and Diselenides

Published: July 30, 2018

Author(s)

Siyuan Zhang, Heather M. Hill, Curt A. Richter, Angela R. Hight Walker, Barlow Stephen, Seth Marder, Christina A. Hacker, Sujitra J. Pookpanratana

Abstract

Developing processes to controllably dope transition-metal dichalcogenides (TMDs) is critical to achieving commercial integration for optical and electrical applications. In this study, molecular reductants and oxidants are introduced onto a series of monolayer TMDs, specifically MoS2, WS2, MoSe2, and WSe2. Doping was achieved by exposing the TMD surface to solutions of pentamethylrhodocene dimer as the molecular reductant (n-dopant) and “Magic Blue,” [N(C6H4-p- Br)3]SbCl6, as the molecular oxidant (p-dopant). Current-voltage characteristics of TMD-based field-effect transistors show that, regardless of their initial transport behavior, all four TMDs can be used in either p- or n-channel devices when appropriately doped. The extent of doping can be controlled conveniently by the concentration of dopant solutions and treatment time, and, in some cases, both non-degenerate and degenerate regimes are accessible. Photoluminescence (PL) properties of the doped monolayer TMDs were measured; for all four materials the PL intensity is enhanced through p-doping but reduced through n-doping. Raman and X-ray photoelectron spectroscopies (XPS) also provide insight on the underlying physical mechanism by which the molecular reductants and oxidants react with the monolayer. The changes of carrier density were estimated and compared based on transistor, PL, and XPS results. This work presents a simple and effective route to tailor the electrical and optical properties of TMDs.
Citation: Advanced Materials
Pub Type: Journals

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Keywords

transition metal dichalcogenides, electron-transfer doping, field-effect transistors, photoluminescence, redox-active molecules
Created July 30, 2018, Updated August 02, 2018