Strain Patterning via Spontaneous Centroidal Voronoi Tessellation in Few-Layer MoS2

Owing to the anisotropic bonding motif inherent to transition metal dichalcogenides (TMDs), these materials can withstand significant elastic strains on the order of 10% and display an associated wide range of variable optical and electronic properties [1]. In addition to interest in fundamental behaviors, such properties have driven efforts to develop strain-tunable devices and applications. While spontaneous wrinkle formation in few to monolayer specimens generates local strain variations, controllable and predictable strain-pattern formation requires rational engineering design and processing principles [2,3]. Nascent approaches have focused on either whole-flake deformation or single, site-specific mechanical indentation to modulate the global or local elastic strain through repeatable stress application. For example, elastomeric films supporting few to monolayer flakes have been used to apply reversible, wholeflake uniaxial strains, while local, nanoscale indentation with AFM tips has been used to quantify elastic stress-strain properties as a function of layer number [4,5]. Spatially periodic strain patterning has been introduced as a way to produce predictable and highly-symmetric local structural modulations in a passive, non-continuous manner (i.e., without the need for constant applied stress). This has been done, for example, by using periodic arrays of nanoparticles blanketing a substrate, followed by flake deposition [6,7]. In this way, local strain can be patterned and controlled by manipulating nanoparticle geometry and patterning periodicity.