Abstract
Ultrathin Janus two-dimensional (2D) materials are attracting intense interest currently. Substitutional doping of 2D transition metal dichalcogenides (TMDs) is of importance for tuning and possible enhancement of their electronic, physical and chemical properties toward industrial applications. Using systematic first-principles computations, we propose a class of Janus 2D materials based on the monolayers MX2 (M = V, Nb, Ta, Tc, or Re; X = S, Se, or Te) with halogen (F, Cl, Br, or I) or pnictogen (N, P, As, Sb, or Bi) substitution. Nontrivial phases are obtained on pnictogen substitution of group VB (V, Nb, or Ta), whereas for group VIIB (Tc or Re), the nontrivial phases are obtained for halogen substitution. Orbital analysis shows that the nontrivial phase is driven by the splitting of M-dyz and M-dxz orbitals. Our study demonstrates that the Janus 2D materials have the tunability and suitability for synthesis under various conditions.
Highlights
Topological insulators (TIs) have been intensely studied for the past few years since the discovery of graphene due to their interesting electrical, optical, and mechanical properties
Twodimensional topological insulators (2D TIs), known as quantum spin Hall (QSH) insulators, exhibit unique symmetryprotected helical metallic edge states with an insulating interior, which makes these materials especially well-suited for optoelectronic, spintronics, quantum computing, and other applications due to the robustness of their edge states against backscattering.[5]
Numerous theoretical studies have been focused on identifying new materials that can support 2D TI1,6–9 or topological crystalline insulator (TCI)[10,11,12,13] phases
Summary
Topological insulators (TIs) have been intensely studied for the past few years since the discovery of graphene due to their interesting electrical, optical, and mechanical properties. Effects of functionalization[7,14,15,16] and substrates[16,17,18] have been investigated, experimental realizations are quite limited so far.[19,20,21] In this connection, one of the most promising classes of 2D materials with semiconducting properties are the transition metal dichalcogenides (TMDs) with chemical formula MX2, where M is a transition metal atom and X is a chalcogen atom, which exhibit different structural phases such as 1T (octahedral) and 2H/3R (trigonal prismatic). We have carried out a first-principles study of possible Janus 2D topological insulator phases via halogen (F, Cl, Br, or I) and pnictogen (N, P, As, Sb, or Bi) substitution, including one-sided hydrogen adsorption, of MX2 (M = V, Nb, Ta, Tc, or Re; X = S, Se, or Te) films in both 1T (octahedral) and 2H (trigonal prismatic) structures.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
