Millimeter-Scale Hexagonal Boron Nitride Single Crystals for Nanosheet Generation

Development of next-generation two-dimensional (2D) transistors or photoelectronic devices is closely linked to advances in 2D materials. Because of its outstanding properties (insulating, stable, inert, transparent, isostructural to graphene, etc.), the hexagonal boron nitride (hBN) crystal, and in particular its exfoliated nanosheets form, is a choice material to fabricate sensors or plasmonic and photonic devices. However, a wide development of these heterostructures still suffers from a lack of large samples and in ample supply. In this context, we propose the fabrication of large exceptional quality hBN single crystals of more than few millimeters lateral size using the polymer route combined with a sintering process. The structural quality and compositional purity are retained after exfoliation and dry transfer of these freestanding boron nitride nanosheets (BNNSs) onto Si substrates. This developed method can be achieved under short and soft conditions and leads to BNNSs with lateral sizes of several hundreds of micrometers. This work paves the way for a wide use of BNNS for 2D material applications.