Theoretical Insight into Hydrogen-Assisted Chemical Vapor Deposition of MoTe₂

While chemical vapor deposition (CVD) has been widely used for synthesizing MoTe2, a deep understanding of the molecular mechanism is still lacking. Here, we investigate the tellurization processes from gas-phase Mo3O9 to MoTe2 monolayer, without or with a H2 atmosphere. Without H2, both high barriers and high reaction energies hinder the growth of MoTe2. The introduction of H2 facilitates the ring opening and chain breaking of Mo3O9 and generates various intermediates involved in different possible reaction paths, which leads to reduced reaction energies and barriers for the tellurization of Mo-containing species. While the formation of a hydroxyl group results in the weakening of Mo–O bonds, the flexible Te coordination chemistry could easily adjust to form stable MoOxTeyHz intermediates. The fully tellurized MoTe6 can easily nucleate at zigzag edge or kink sites of either 1T′- or 2H-MoTe2, with low barriers. This study provides a molecular-level understanding of the MoTe2 CVD growth.