Growth mechanism of 2D Mo2C on Cu via CVD

Abstract

This study investigates the growth of Mo2C crystals via chemical vapor deposition (CVD) in the presence of a carbon (H2/CH4 gas)-containing environment. The study employs both theoretical and experimental approaches to investigate the vertical and lateral (in-plane) growth of Mo2C crystals. A physico-mathematical consideration is applied to develop an analytical forward model, which incorporates bulk diffusivities, surface diffusivities, and solubility gradients for Mo2C crystal growth. Coupled nonlinear flow equations have been advanced for the Mo-, Cu-, Mo2C layer framework and effectively predicted the Mo2C crystal growth rate for both vertical and lateral directions. Forming the Mo2C crystal height and diameter was directly correlated with copper layer thickness and time using the forward model and then validated by the experiments together with SEM and AFM studies. Studies showed that the Cu layer thickness plays a crucial role in controlling the height of the Mo2C crystal while it is not that critical in changing the lateral dimension of the crystal. Beyond simply enhancing Mo2C crystal growth and property-processing relationship, this study demonstrated the synthesis of designer Mo2C, which can be tailored to the needs of specific applications. This forward model will enable us to further enhance and exploit the family of analogs of materials previously demonstrated by other methods.