Thin-suspended 2D Materials: Facile, Versatile, and Deterministic Transfer Assembly

Abstract: We report a deterministic 2D material (2DM) transfer method to assemble any-stacking-order heterostructures incorporating suspended ultra-thin 2D materials, such as single-layer graphene (SLG) and bilayer graphene (BLG). The transfer procedure relies on a single-step preparation nitrocellulose micro-stamp, which combines both outstanding adhesion and softness. It permits the dry pick-up of naked 2D crystals (graphene, MoS$_2$, and hBN) directly from a SiO$_2$ substrate, and to precisely transfer them on substrates or trenches. Optical and Raman data show that no significant defect is introduced upon transfer, even in suspended SLG and BLG. The areas transferred range up $\sim$ 1000 $\mu$m$^2$ on substrate. High-yield transfer of suspended ultra-thin 2DM does not require critical point drying for areas up to 15 $\mu$m$^2$ or suspension heights down to 160 nm. To demonstrate the method's capabilities, we assembled on-substrate and suspended optical cavities tuning BLG's Raman scattering intensity by factors of 19 and 4, respectively. This resilient and rapid 2DM transfer procedure will accelerate the fabrication of many heterostructures and permit versatile suspension of 2DMs for research in twistronics, straintronics, and nano-opto-electro-mechanical systems (NOEMS).