Flexible Large-Area Graphene Films of 50-600 nm Thickness with High Carrier Mobility.

Bulk graphene nanofilms feature fast electronic and phonon transport in combination with strong light-matter interaction and thus have great potential for versatile applications, spanning from photonic, electronic, and optoelectronic devices to charge-stripping and electromagnetic shielding, etc. However, large-area flexible close-stacked graphene nanofilms with a wide thickness range have yet to be reported. Here, we report a polyacrylonitrile-assisted 'substrate replacement' strategy to fabricate large-area free-standing graphene oxide/polyacrylonitrile nanofilms (lateral size ~ 20 cm). Linear polyacrylonitrile chains-derived nanochannels promote the escape of gases and enable macro-assembled graphene nanofilms (nMAGs) of 50-600 nm thickness following heat treatment at 3,000 °C. The uniform nMAGs exhibit 802-1,540 cm V s carrier mobility, 4.3-4.7 ps carrier lifetime, and > 1,581 W m K thermal conductivity (nMAG-assembled 10 µm-thick films, mMAGs). nMAGs are highly flexible and show no structure damage even after 1.0 × 10 cycles of folding-unfolding. Furthermore, nMAGs broaden the detection region of graphene/silicon heterojunction from near-infrared to mid-infrared and demonstrate higher absolute electromagnetic interference (EMI) shielding effectiveness than state-of-the-art EMI materials of the same thickness. These results are expected to lead to the broad applications of such bulk nanofilms, especially as micro/nanoelectronic and optoelectronic platforms.