Atomically Thin Ordered Alloys of Transition Metal Dichalcogenides: Stability and Band Structures

We explore the possibility of modulating the electronic band edges of the transition metal dichalcogenides (TMDs) via alloying of different semiconductors within the same group (intragroup alloying). The stability of the ordered alloys is assessed from the calculated mixing enthalpy, which is found to be negative for several alloys and below 20 meV/atom for all of the alloys. We explore to what extent the electronic properties like the band gap and band edge positions of the alloy can be evaluated by taking the weighted average of the corresponding properties of the pristine systems. In general, this approach works well with the only exception being Cr-containing compounds. Because the calculated properties of the alloys are very similar to the weighted averages, we expect that the trends observed for the ordered alloys will also hold for more realistic disordered alloys.