Strain engineering has been widely used to modify physical properties of materials to achieve better device performance. Recently, advances in the isolation and fabrication of monolayer materials have led to a wealth of interest in the engineering of strain in these monolayer materials for applications.
Monolayer materials exhibit mechanical strengths that enable the use of strains much larger than can be achieved in bulk materials. However, the unusual mechanical properties of monolayers require different approaches than for bulk materials. Here, we utilize REBO-based interatomic potentials to explore the potential for the engineering of strain in monolayer materials in the context of graphene using lithographically or otherwise patterned adatom adsorption.
We discover that the resulting monolayer strain is a complex competition between the in-plane elasticity and out-of-plane relaxation deformations. The strain outside the adatom adsorption region vanishes due to out-of-plane relaxation deformations. Under some circumstances, an annular adsorption pattern generates large strains of approximately 2% inside the adsorption region, and here the elastic plane strain model can be used to provide some qualitative guidance. We find that the strains generated are up to 5.8% of the lattice constant change in the adsorbed region. In addition, an elliptical adsorption pattern proves to have the potential to produce uniaxial strains of as large as 4%. Our results elucidate a potential method for strain control at the nanoscale in monolayer devices.