Ultra-large suspended graphene as a highly elastic membrane for capacitive pressure sensors

• Published in: Nanoscale Vol. 8; no. 6; pp. 3555 - 3564
• Main Authors: Chen, Yu-Min, He, Shih-Ming, Huang, Chi-Hsien, Huang, Cheng-Chun, Shih, Wen-Pin, Chu, Chun-Lin, Kong, Jing, Li, Ju, Su, Ching-Yuan
• Format: Journal Article
• Language: English
• Published: England 14.02.2016
• Subjects: Annealing; Arrays; Chemical vapor deposition; Graphene; Membranes; Nanostructure; Pressure sensors; Silicon substrates
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c5nr08668j

In this work, we fabricate ultra-large suspended graphene membranes, where stacks of a few layers of graphene could be suspended over a circular hole with a diameter of up to 1.5 mm, with a diameter to thickness aspect ratio of 3 × 10(5), which is the record for free-standing graphene membranes. The process is based on large crystalline graphene (∼55 μm) obtained using a chemical vapor deposition (CVD) method, followed by a gradual solvent replacement technique. Combining a hydrogen bubbling transfer approach with thermal annealing to reduce polymer residue results in an extremely clean surface, where the ultra-large suspended graphene retains the intrinsic features of graphene, including phonon response and an enhanced carrier mobility (200% higher than that of graphene on a substrate). The highly elastic mechanical properties of the graphene membrane are demonstrated, and the Q-factor under 2 MHz stimulation is measured to be 200-300. A graphene-based capacitive pressure sensor is fabricated, where it shows a linear response and a high sensitivity of 15.15 aF Pa(-1), which is 770% higher than that of frequently used silicon-based membranes. The reported approach is universal, which could be employed to fabricate other suspended 2D materials with macro-scale sizes on versatile support substrates, such as arrays of Si nano-pillars and deep trenches.