Sci. Adv. 3, e1700414 (2017)

Large-scale fabrication of devices based on 2D materials requires scalable and low-cost deposition techniques that go beyond traditionally used mechanical transfer and high-temperature growth. Solution-based methods offer quick and simple ways of thin-film deposition but do not provide sufficient control of the thickness and morphology of coatings. Matsuba et al. now report a spin-coating method to obtain dense large-area mono- and multilayers formed of neatly tiled 2D nanosheets.

The researchers disperse several types on nanosheets including graphene oxide and its reduced form into DMSO/tetrabutylammonium (TBA) hydroxide solution. When spin-coated under optimized conditions, the suspensions form a uniform and ordered monolayer with edge-to-edge packed nanosheets showing negligible overlaps. Due to its high viscosity, DMSO acts as a binder for the nanosheets, preventing them from spreading out during the deposition process, whereas TBA cations connect the basal planes of adjacent nanosheets, promoting a monolayer formation. The uniformity of the obtained monolayer films is preserved within a radius of 8 mm. A layer-by-layer deposition of thicker films can be achieved by successive spin-coating steps. The films require post-deposition annealing to ensure better adhesion to the substrate.

Monolayer tiling of nanosheets can be applied to other 2D materials, although further optimization is required for industrial-scale production.