In-Cu alloy substrates for low-temperature chemical vapor deposition of Mo2C

Two-dimensional transition metal carbides are promising materials because of their potential for combining the favorable properties of transition metal carbides with the high aspect ratio of two-dimensional materials. Though commonly produced by top-down wet-chemical synthesis methods, synthesis by chemical vapor deposition is being considered because of its ability to achieve large areas, controlled layer thickness, and reduced defect density. Typically, liquid Cu is used as a synthesis substrate, though the high melting temperature of Cu (1085 degrees C) requires high synthesis temperatures. Thus, alternative substrates have been studied in order to reduce the necessary melting temperature. This work systematically studies the impact of synthesis parameters and substrate composition on the growth of ultrathin Mo2C (similar to 4-120nm thick) by chemical vapor deposition on an In-Cu alloy. Mo2C flake size increases, and graphene/Mo2C heterostructures form with an increase in the methane flow rates. Increasing the In composition slightly decreases surface coverage and coalescence but does not appreciably impact the Mo2C flake size. Increasing In content also decreases the alloy substrate melting temperature so that a lower temperature synthesis (800 degrees C) can be performed. However, the necessary high temperatures for pyrolysis of methane lead to a lower limit for the synthesis temperature, similar to graphene.

Automated summary

The study investigates the growth of ultrathin Mo2C on an In-Cu alloy substrate using chemical vapor deposition and how synthesis parameters and substrate composition can affect the process. Increasing methane flow rates results in larger Mo2C flake sizes and the formation of graphene/Mo2C heterostructures. Higher In composition reduces surface coverage and coalescence but does not significantly impact Mo2C flake size.