Engineered Creation of Periodic Giant, Nonuniform Strains in MoS2 Monolayers

• Published in: Advanced materials interfaces Vol. 7; no. 17
• Main Authors: Blundo, Elena, Di Giorgio, Cinzia, Pettinari, Giorgio, Yildirim, Tanju, Felici, Marco, Lu, Yuerui, Bobba, Fabrizio, Polimeni, Antonio
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.09.2020
• Subjects: 2D materials; Atomic force microscopy; bubbles; Computer simulation; Domes; Energy conservation; engineering; Gas pressure; Molybdenum disulfide; Monolayers; MoS2 monolayers; nonuniform strains; Performance enhancement; Scaling laws; Strain distribution
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.202000621

The realization of ordered strain fields in 2D crystals is an intriguing perspective in many respects, including the instauration of novel transport regimes and enhanced device performances. However, the current straining techniques hardly allow to reach strains higher than ≈3% and in most cases there is no control over the strain distribution. In this work, a method is demonstrated to subject micrometric regions of atomically thin molybdenum disulfide (MoS2) to giant strains with the desired ordering. Selective hydrogen‐irradiation of bulk flakes allows the creation of arrays of size/position‐controlled monolayer domes containing pressurized hydrogen. However, the gas pressure is ruled by energy minimization, limiting the extent and geometry of the mechanical deformation of the 2D membrane. Here, a protocol is developed to create a mechanical constraint, that alters remarkably the morphology of the domes, otherwise subject to universal scaling laws, as demonstrated by atomic force microscopy. This enables the realization of unprecedented periodic configurations of large strain gradients—estimated by numerical simulations—with the highest strains being close to the rupture critical values (>10%). The creation of such high strains is confirmed by Raman experiments. The method proposed here represents an important step toward the strain engineering of 2D crystals. Spherically shaped 2D membranes are created via hydrogen irradiation of bulk MoS2. Here, a novel engineering protocol is developed to tailor the size, shape, and position of the bulges. Periodic, nonuniform, giant strains up to 12% in MoS2 monolayers are attained, with enormous potentialities for the instauration of novel transport regimes and the achievement of enhanced broadband light absorption.