Controlled CVD growth of ultrathin Mo2C (MXene) flakes

MXenes combine distinctive properties, including high electrical conductivity, high thermal conductivity, and efficient absorption of electromagnetic waves, which allow them to be utilized in various applications such as electrical energy storage, sensors, and functional composites. This study aims to grow thin and large area $\mathrm{M}{\mathrm{o}}_2\mathrm{C}$ flakes in a controlled manner by using chemical vapor deposition, avoiding surface functionalization, and limited lateral dimensions. Herein, we investigate the effects of $\mathrm{C}{\mathrm{H}}_4$ flow, the precursor/catalyst (Mo/Cu) ratio, and flow rates of carrier gas on the growth of two-dimensional $\mathrm{M}{\mathrm{o}}_2\mathrm{C}$ structures. This study examines the effects of the precursor/catalyst (Mo/Cu) ratio and flow rates of carrier gas on the growth of $\mathrm{M}{\mathrm{o}}_2\mathrm{C}$ structures. Our results show that when the flow rates of $\mathrm{C}{\mathrm{H}}_4$ , catalyst/precursor (Cu/Mo) ratio, and carrier gas (${\mathrm{N}}_2$ /${\mathrm{H}}_2$ ) ratio are varied, we can control both thickness (from 7 to 145 nm) and coverage of the substrate surface (from 11% to 68%) of the $\mathrm{M}{\mathrm{o}}_2\mathrm{C}$ flakes. Therefore, this study reveals that it is possible to realize centimeter-scale surface coverage and controllable thicknesses by adjusting the process parameters. The deposited films and flakes are analyzed by optical microscopy, atomic force microscopy, and Raman scattering spectroscopy techniques. The Raman spectra are also compared with the theoretical calculations using density functional theory. Overall, the present work is expected to provide a significant impact for utilization of MXenes in various applications.