Abstract
•Few-layered 4-mm-wide graphene membranes were achieved.•This result shows a 2-fold higher area/n° of layers ratio compared to previous literature.•A sublimation-assisted transfer process was used, avoiding wet methods’ problems.•This process reveals a 100 % yield for membranes as large as 1 mm in diameter.•A microphone with increased specific sensitivity is demonstrated.
In this work, suspended 4-mm-wide graphene membranes are obtained through a sublimation-assisted transfer process, using few-layer films grown by microwave plasma chemical vapor deposition. This result is achieved by a new approach involving the removal of the graphene-transfer supporting layer in vacuum. The membranes produced by this procedure show the largest area-to-thickness ratio described in the literature with a 2-fold improvement when compared to the best results using the conventional PMMA-assisted transfer, and a five orders of magnitude increase when compared to previous sublimation-assisted processes. This breakthrough allows the implementation of a wide variety of technological applications where 2D materials with atomic thickness and large areas are required. As large-area free-standing membranes are difficult to obtain, a new figure of merit is defined to benchmark the various methods of suspending graphene. A high transfer yield is achieved, and the mechanical and optical properties of the 3.7 nm thick membranes are evaluated. Finally, a prototype condenser microphone is built and tested, and found to exhibit an enhanced specific response.
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