Thermomechanical Nanostraining of Two-Dimensional Materials.

Liu, Xia; Sachan, Amit Kumar; Howell, Samuel Tobias; Conde-Rubio, Ana; Knoll, Armin W; Boero, Giovanni; Zenobi, Renato; Brugger, Jürgen · Nano Lett · 2020

basic_science · Level V

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Abstract

Local bandgap tuning in two-dimensional (2D) materials is of significant importance for electronic and optoelectronic devices but achieving controllable and reproducible strain engineering at the nanoscale remains a challenge. Here, we report on thermomechanical nanoindentation with a scanning probe to create strain nanopatterns in 2D transition metal dichalcogenides and graphene, enabling arbitrary patterns with a modulated bandgap at a spatial resolution down to 20 nm. The 2D material is in contact via van der Waals interactions with a thin polymer layer underneath that deforms due to the heat and indentation force from the heated probe. Specifically, we demonstrate that the local bandgap of molybdenum disulfide (MoS<sub>2</sub>) is spatially modulated up to 10% and is tunable up to 180 meV in magnitude at a linear rate of about -70 meV per percent of strain. The technique provides a versatile tool for investigating the localized strain engineering of 2D materials with nanometer-scale resolution.