Uncovering the Effects of Metal Contacts on Monolayer MoS<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 32905703.
- Also identified by DOI 10.1021/acsnano.0c03515.
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Abstract
Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here, we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.2 eV) and monolayer MoS<sub>2</sub> grown by chemical vapor deposition. We evaporate thin metal films onto MoS<sub>2</sub> and study the interfaces by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and electrical characterization. We uncover that (1) ultrathin oxidized Al dopes MoS<sub>2</sub> <i>n-</i>type (>2 × 10<sup>12</sup> cm<sup>-2</sup>) without degrading its mobility, (2) Ag, Au, and Ni deposition causes varying levels of damage to MoS<sub>2</sub> (e.g. broadening Raman E' peak from <3 to >6 cm<sup>-1</sup>), and (3) Ti, Sc, and Y react with MoS<sub>2</sub>. Reactive metals must be avoided in contacts to monolayer MoS<sub>2</sub>, but control studies reveal the reaction is mostly limited to the top layer of multilayer films. Finally, we find that (4) thin metals do not significantly strain MoS<sub>2</sub>, as confirmed by X-ray diffraction. These are important findings for metal contacts to MoS<sub>2</sub> and broadly applicable to many other 2D semiconductors.