  Polymorphic phases and collective phenomena - such as charge density waves
(CDWs) - in transition metal dichalcogenides (TMDs) dictate the physical and
electronic properties of the material. Most TMDs naturally occur in a single
given phase, but the fine-tuning of growth conditions via methods like
molecular beam epitaxy (MBE) allows to unlock otherwise inaccessible
polymorphic structures. Exploring and understanding the morphological and
electronic properties of new phases of TMDs is an essential step to enable
their exploitation in technological applications. Here, we use scanning
tunneling microscopy to map MBE-grown monolayer TaTe2. We report the first
observation of the 1H polymorphic phase, coexisting with the 1T, and
demonstrate that their relative coverage can be controlled by adjusting
synthesis parameters. Several super-periodic structures, compatible with CDWs,
are observed to coexist on the 1T phase. Finally, we provide theoretical
insight on the delicate balance between Te...Te and Ta-Ta interactions that
dictates the stability of the different phases. Our findings demonstrate that
TaTe2 is an ideal platform to investigate competing interactions, and indicate
that accurate tuning of growth conditions is key to accessing metastable states
in TMDs.
