Pressure-Driven Metallicity in Ångström-Thickness 2D Bismuth and Layer-Selective Ohmic Contact to MoS<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 40999703.
- Also identified by DOI 10.1021/acs.nanolett.5c03319.
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Abstract
Recent fabrication of two-dimensional (2D) metallic bismuth (Bi) via van der Waals (vdW) squeezing offers a route to <i>ultrascaling</i> metal into ångström thickness. However, free-standing 2D Bi is typically semiconducting, which contradicts the experimentally observed metallicity in vdW-squeezed 2D Bi. Here we show that this discrepancy originates from the pressure-induced buckled-to-flat structural transition in 2D Bi, changing the electronic structures from semiconducting to semimetallic. Based on the experimentally fabricated MoS<sub>2</sub>-Bi-MoS<sub>2</sub> <i>trilayer</i> heterostructure, we demonstrate the concept of <i>layer-selective Ohmic contact</i> in which one MoS<sub>2</sub> layer forms an Ohmic contact to the 2D Bi while the opposite MoS<sub>2</sub> exhibits a Schottky barrier. The Ohmic contact can be switched between the two sandwiching MoS<sub>2</sub> monolayers by reversing an external gate field, thus enabling charge to be spatially injected into different MoS<sub>2</sub> layers. The layer-selective Ohmic contact proposed here represents a <i>layertronic</i> generalization of semimetal/semiconductor contact, paving the way toward layertronic device application.