Realization of 2D crystalline metal nitrides via selective atomic substitution

Two-dimensional (2D) transition metal nitrides (TMNs) are new members in the 2D materials family with a wide range of applications. Particularly, highly crystalline and large area thin films of TMNs are desirable for applications in electronic and optoelectronic devices; however, the synthesis of these TMNs has not yet been achieved. Here, we report the synthesis of few-nanometer thin Mo₅N₆ crystals with large area and high quality via in situ chemical conversion of layered MoS₂ crystals. The versatility of this general approach is demonstrated by expanding the method to synthesize W₅N₆ and TiN. Our strategy offers a new direction for preparing 2D TMNs with desirable characteristics, opening a door for studying fundamental physics and facilitating the development of next-generation electronics.