Controlled CVD growth of ultrathin Mo2C (MXene) flakes

Abstract

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 Mo2C flakes in a controlled manner by using chemical vapor deposition, avoiding surface functionalization, and limited lateral dimensions. Herein, we investigate the effects of CH4 flow, the precursor/catalyst (Mo/Cu) ratio, and flow rates of carrier gas on the growth of two-dimensional Mo2C structures. This study examines the effects of the precursor/catalyst (Mo/Cu) ratio and flow rates of carrier gas on the growth of Mo2C structures. Our results show that when the flow rates of CH4, catalyst/precursor (Cu/Mo) ratio, and carrier gas (N-2/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 Mo2C 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.