Initial stage of MBE growth of MoSe₂ monolayer

An atomically thin MoSe₂ layer has been synthesized on mica using molecular beam epitaxy (MBE). The polymorphous of the MoSe₂ layer depends on the coverage and the growth temperature. At low coverages and low growth temperature, 1T-MoSe₂ forms in addition to a comparable quantity of 2H-MoSe₂. The metastable 1T-MoSe₂ transfers gradually to the stable 2H-MoSe₂ before the completion of the first monolayer. The current result sheds some light on the complexity of the nucleation and growth of transition metal dichalcogenide (TMDC) monolayers and implies a possible route for a phase selective synthesis using MBE.