Highly strained graphene samples of varying thickness and comparison of their behaviour

Mechanically straining graphene opens the possibility to exploit new properties linked to the stressed lattice of this two-dimensional material. In particular, theoretical analyses have forecast that straining graphene by more than 10% is a requirement for many novel applications that have not yet been experimentally demonstrated. Recently, we reported having achieved 12.5% strain in a trilayer graphene sample (3LG) in a controlled, reversible and non-destructive way. In this paper, we explore our method by straining samples of varying thicknesses and comparing their behavior, where strains of 14% and 11% were achieved for monolayer and four-layer graphene (4LG), respectively. For the analysis, optical tracking and the correspondent Raman spectra were taken. While doing so, we observed slippage between two layers in a bilayer sample of which one layer was clamped on one side only. The obtained results when stretching different samples to extreme strains demonstrated the exceptional elasticity of graphene, which might be essential for practical applications. Hysteretic effects observed in the partially clamped layer hints at small energy losses during slippage. This may shed new light on the superlubricity property of graphene that has been reported in the literature. (paper)