  We report on the various types of Peierls like two dimensional structural
modulations and relative phase stability of 2H and 1T poly-types in MoS2-ReS2
and WS2-ReS2 alloy system. Theoretical calculation predicts a polytype phase
transition cross over at ~50 at.% of Mo and W in ReS2 in both monolayer and
bulk form, respectively. Experimentally, two different types of structural
modulations at 50% and a modulation corresponding to trimerization at 75% alloy
composition is observed for MoS2-ReS2 and only one type of modulation is
observed at 50% WS2-ReS2 alloy system. The 50% alloy system is found to be a
suitable monolithic candidate for metal semiconductor transition with minute
external perturbation. ReS2 is known to be in 2D Peierls distorted 1Td
structure and forms a chain like superstructure. Incorporation of Mo and W
atoms in the ReS2 lattice modifies the metal-metal hybridization between the
cations and influences the structural modulation and electronic property of the
system. The results offer yet another effective way to tune the electronic
structure and poly-type phases of this class of materials other than
intercalation, strain, and vertical stacking arrangement.
