Computational Investigation of Orderly Doped Transition Metal Dichalcogenides: Implications for Nanoscale Optoelectronic Devices

Doping is an effective approach to tailoring the electronic properties of nanomaterials to realize their specific applications. However, position-controllable doping is still a challenging task. In contrast to the common randomly doped alloys, here we present a feasible approach to achieving orderly doped 1T′-MoX_2(1-x)Y_2x(X and Y represent chalcogens S, Se, or Te) compounds, where X and Y are alternatively arranged rather than randomly distributed, from first-principles calculations. The underlying mechanism is attributed to the unique structure, the bonding space, and the chemical environment at two sides of Mo to distribute in the distorted 1T′ phase. The dopants with relatively smaller atomic radii prefer to selectively substitute the atoms with a smaller space in the 1T′-MoTe₂and achieve the alternating ordered structure. 2H orderly alloys cannot be achieved by direct doping but can be formed from the phase transition after overcoming a reasonable energy barrier. The structural stability has been confirmed from the mixing energy calculation. This method is applicable to all transition metal dichalcogenides (TMDs). It is interesting to notice that the orderly doped TMDs have shown different electronic structures from the randomly doped TMDs. The band-edge states were contributed from different rows due to the presence of interior electric polarization. The developed approach here provides a feasible method to precisely control the structure of TMDs and an easy way to tune electronic structures to realize their potential applications for nanoscale optoelectronic devices.