Synthesis and Properties of (BiSe)0.97MoSe2: A Heterostructure Containing Both 2H-MoSe2 and 1T-MoSe2

The metastable heterostructure (BiSe)0.97MoSe2 containing alternating bilayers of BiSe and MoSe2 trilayers was synthesized using the modulated elemental reactant method to determine if charge transfer from BiSe to MoSe2 would stabilize the metallic 1T polymorph of MoSe2. Optimum synthesis conditions were determined by following the structural evolution as a function of temperature. The structure of the product contained distorted rock salt structured BiSe layers alternating with hexagonal MoSe2 layers. High angle annular dark field scanning transmission electron microscopy images revealed that two different polymorphs of MoSe2 coexisted in (BiSe)0.97MoSe2. Raman spectroscopy confirmed the presence of 1T MoSe2 layers. XPS indicated that there were two different electronic states for both Mo and Bi. The Mo states are consistent with having octahedral and trigonal prismatic coordination of molybdenum as found in the 1T and 2H polymorphs of MoSe2. The two different electronic states for Bi are consistent with...