In-situ atomic level observation of the strain response of graphene lattice

Abstract

Strain is inevitable in two-dimensional (2D) materials, regardless of whether the film is suspended or supported. However, the direct measurement of strain response at the atomic scale is challenging due to the difficulties of maintaining both flexibility and mechanical stability at low temperature under UHV conditions. In this work, we have implemented a compact nanoindentation system with a size of $$\sim $$ ∼ 160 mm$$^2$$ 2 $$\times $$ × 5.2 mm in a scanning tunneling microscope (STM) sample holder, which enables the reversible control of strain and gate electric field. A combination of gearbox and piezoelectric actuator allowed us to modulate the depth of the indentation continuously with nanometer precision. The 2D materials were transferred onto the polyimide film. Pd clamp was used to enhance the strain transfer from the polyimide from to the 2D layers. Using this unique technique, strain response of graphene lattice were observed at atomic precision. In the relaxed graphene, strain is induced mainly by local curvature. However, in the strained graphene with tented structure, the lattice parameters become more sensitive to the indentor height change and stretching strain is increased additionally. Moreover, the gate controllability is confirmed by measuring the dependence of the STM tip height on gate voltage.

Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update

“…(iv) Stain created by electromagnetic fields [6][7][8]. (v) Nanoindentation under scanning tunnelling microscopes (STMs) for reversible strain under tip-induced electric fields [9,10]. (vi) Folding (origami) [11,12], cutting (kirigami) [13], or both [14].…”

Investigation of Interface Interactions Between Monolayer MoS2and Metals: Implications on Strain and Surface Roughness

“…Furthermore, strain is known to alter the physical and chemical properties, such as the band gap, charge carrier effective masses, dielectric properties, chemical reactivity, and so on. The local strain induced at the 2D-metal interface might be more complex and varied compared to that on traditional dielectric substrates due to the increased interface interactions after transfer. − For example, at the interface between MoS 2 and Au, the combination of charge and strain induces the 2H-to-1T phase transition of MoS 2 , which largely changes the properties of monolayer MoS 2 from semiconducting to metallic.…”

Machine learning approach on the prediction of mechanical characteristics of pristine, boron doped and nitrogen doped graphene

“…Graphene-based nanocomposites provide multilayer structures made of 2D building blocks that have higher stiffness, strength, and energy dissipation properties [8][9][10]. Due to its exceptional mechanical and electrical capabilities, graphene is a strong contender for uses in electromechanical devices and flexible electronics [9,11,12]. Despite the fact that band-gap is crucial to regulate the electronic properties, graphene has an electronic structure with no band-gap [13][14][15].…”