Figure 1.

a) The four crystalline phases (2H, 1T, 1T′, Td) of 2D TMDs. M represents a metal atom, X represents a chalcogen compound, and all three phases are composed of the X—M—X layer structure. Reproduced with permission.33 Copyright 2014, Nature Publishing Group. Reproduced with permission.45 Copyright 2015, American Chemical Society. Reproduced with permission.65 Copyright 2015, American Physical Society. b) Perspective drawing of a primitive cell of monolayer ReS₂. The blue shows the strong metallic Re—Re bond. Reproduced with permission.66 Copyright 2015, American Physical Society. c) crystal structure of monolayer ReS₂, the red arrows represent the direction of a and b axes. d) Band structure of monolayer, trilayer, and five‐layer ReS₂. Reproduced with permission.67 Copyright 2015, the authors, published under CC‐BY‐4.0 license.