Nanobubbles at extreme pressure under graphene

Owing to the exceptional strength and flexibility of sp²-carbon, graphene is able to trap mesoscopic volumes of liquid or gas. Nanobubbles (NB) under graphene came in the spotlight in view of potential applications such as gas storage and high-pressure chemistry,  fostering fruition in a plethora of novel devices. To date, only few studies have addressed the basic structural properties of NB under graphene. In the present study we have investigated the morphology and spatial distribution of Ar under micron-sized graphene flakes supported on Ir(100). We provide direct evidence that irradiation of a graphene membrane on Ir with low-energy Ar ions induces formation of solid noble-gas nanobubbles. Their size can be controlled by thermal treatment, reaching tens of nanometers laterally and height of 1.5 nm upon annealing at 1080 °C. Ab initio calculations show that Ar nanobubbles are subject to pressures reaching tens of GPa, their formation being driven by minimization of the energy cost of film

distortion and loss of adhesion. We expect that ripening of intercalated noble gases can also occur in other graphene/metal systems showing comparable adhesion strength, where it might be fruitfully exploited to strain-engineer the local chemical properties of graphene. Our study also fosters the synchrotron-based investigation of van der Waals solids under extreme pressure and temperature conditions.

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