Liquid Precursor-Enabled Growth of 2D Mo2C and Mo2C/Graphitic Carbon Heterostructures

In this work, we present the low-pressure chemical vapor deposition (CVD) growth of two-dimensional (2D) Mo2C using liquid n-hexane as a carbon precursor on a Cu/Mo bilayer under H2 at ∼1085 °C. By varying the reactor pressure from 0.75 to 1.00 mbar, corresponding to different carbon-flux conditions, we achieve controlled evolution in surface carbon availability during growth. Under comparatively lower flux conditions, well-defined faceted Mo2C domains with enhanced lateral growth are obtained. With increased flux, graphitic carbon signatures emerge together with denser but comparatively smaller Mo2C domains. Time-dependent studies (5-10 min) further reveal systematic changes in domain size and domain density with increasing flux. The use of liquid n-hexane enables modulation of the reactive carbon supply in hydrocarbon-assisted CVD. Based on the combined optical microscopy, Raman mapping, and AFM observations, we propose a qualitative flux-dependent growth framework in which increased surface carbon availability influences the evolution from predominantly Mo2C-dominated growth toward mixed Mo2C/graphitic-carbon surface structures.