Growth of 2D In2Se3 with large domain sizes in a confined micro-reactor. (a) A summary of the domain sizes of 2D materials including graphene, TMDCs, h-BN, and In2Se3 grown by conventional vapor phase deposition. (b) Schematic of the confined micro-reactor for the growth of 2D In2Se3 on mica with large domain sizes. The inset shows a side-view SEM image of the reactor, which is composed of two stacked mica sheets with an average distance of 135 μm between them. (c, d) Schematics showing different gas flow behaviors in the (c) confined and (d) conventional growth methods. (e, f) Optical images of In2Se3 crystals grown on the mica substrates with confined and conventional growth. (g, h) Statistical data of the edge length and thickness of In2Se3 grown using the two methods. The inset in (h) shows a typical AFM image of 2D In2Se3 grown in the confined micro-reactor.