June 23, 2023

The formation of standing optical waves lead to laser heating depending on the height of the garphene bubble, which results in Raman band oscillations when scanning the laser spot across the bubble. The profile of the bubble under laser illumination can be deduced from the Raman G band oscillations. A distinct swelling at the center of the bubble is observed which is attributed to the strong softening of graphene above 1000 °C.

Graphene has superior mechanical properties. Only a few theoretical studies are available on the elastic modulus of graphene up to 700 °C and there are no reported experimental studies so far on the elastic properties of graphene at elevated temperatures.

We revisited the Raman spectral data of graphene bubbles since a closer examination of the Raman oscillactions indicated smaller oscillations at the center of the bubble. Our spectral analysis shows a clear “swelling” at the center of the bubble where the temperature is highest, and the temperature at the edge of the swelling is found to be close to 1000 °C. When taking into account heat transport through graphene only, analytical expressions for the temperature are derived. The so-determined temperature exceeds 2000 °C at the center of the bubble.

When including heat conduction through the gas inside the bubble employing finite volume analysis, it is found that heat conduction through the gas in the bubble is significant and lowers the maximum temperature at the center of the bubble to below 1400 °C. The appearance of a swelling in large graphene bubbles when laser heated might eventually find application for creating a central hole in graphene membranes. This work is a collaboration between 2 laboratories in Toulouse (Laplace, CEMES) and a laboratory in South Korea (CMCM at UNIST).

Publication:

Probing elastic properties of graphene and heat conduction in graphene bubbles above 1000 ◦C
Bacsa, F. Topin, M. Miscevic, J.M. Hill, Y. Huang, R.S. Ruoff
Physical Review B 107, 195433 (2023)
https://doi.org/10.1103/PhysRevB.107.195433

Contact:
Wolfgang Bacsa | wolfgang.bacsa[at]cemes.fr