Realization of 2D Crystalline Metal Nitrides via Selective Atomic Substitution

Two-dimensional (2D) transition metal nitrides (TMNs) are emerging members in 2D family with promising potential for a range of applications. Their applications can be further extended to electronic and optoelectronic devices through the acquisition of high crystalline and large-area thin films. However, materials that meet such requirements have not been achieved using previous methods. Here, we report the synthesis of few-nanometer thin Mo₅N₆ crystals with satisfactory area and quality via chemical conversion of layered MoS₂ crystals. The lateral dimensions of Mo₅N₆ crystals are inherited from the MoS₂ precursors. Atomic force microscopy characterization indicates that the thicknesses of Mo₅N₆ crystal reduce to about 1/3 of the MoS₂ crystal, matching well with the crystal structure model. Electrical measurement shows the high conductivity of Mo₅N₆. In addition, this chemical conversion strategy is found versatile for the synthesis of various metal nitrides including W₅N₆, and TiN using corresponding metal sulfides. Our strategy offers a new direction for preparing 2D TMNs with desired characteristics, opening a door for future exploration of fundamental physics and devices applications.