Fig. 1: Synthesis and structural characterization of 1T”-MoS₂ flakes.

a MoS₂ flake on Si/SiO₂ substrate before and after the treatment with tert-butyllithium. b, c Experimental SAED patterns of the MoS₂ flakes before (b) and after (c) the lithiation treatment and the corresponding theoretical SAED patterns constructed using the calculated atomic positions in the unit cell with the trigonal symmetry (see Supplementary Table 1 and Supplementary Fig. 2). The SAED patterns in b, c correspond to 2H-MoS₂ and 1T”-MoS₂ phases, respectively. d Atomic structure of 1T”-MoS₂ (upper panel—top view, lower panel—side view). A unit cell is marked by the purple rhombus in the upper panel. Arrows in the upper panel illustrate the displacements of the Mo atoms forming trimers (marked by dashed triangles). The Mo and S atoms located close to the ideal positions in the undistorted 1T-MoS₂ structure are shown as blue and yellow spheres, respectively. Arrows in the lower panel illustrate the vertical displacements of the polar sulfur atoms in the centers of the trimers and sulfur atoms bridging the trimers (marked by the dashed blue and red circles, respectively) from their ideal positions. Vertical displacement of the S atoms results in the emergence of an out-of-plane polarization. e TEM image of a representative 1T”-MoS₂ flake (shown in blue for clarity) on a lacey carbon TEM grid.