Fig. 2

Hydrogen adsorption at 2H–1T-phase boundaries. a STM topography of as-treated MoS₂ showing mixed 2 H (bright) and 1 T (dark) domains. b Zoom-in image of a domain boundary as denoted by a dashed square in a, where 2H and 1T phases are rendered with yellow and purple colors, respectively. The lattice grid of 2H phase is superimposed on the image to highlight the lateral sliding of S atoms in 1T phase. The black arrows indicate the sliding direction [120]. The two in-plane primitive vectors are shown in the upper left of b. c dI/dV spectra taken on the 2H and 1T phases, suggesting the semiconducting 2H phase with a 2.5-eV bandgap and metallic 1T phase. d STM image of the MoS₂ after hydrogenation, showing prominent depression features. The sample bias was chosen such that the apparent heights of 2 H and 1 T phases become similar, to highlight the depression features. e Zoom-in image of the depression features as denoted by a dashed square in d, indicating that the depression features are located exactly at the boundary of 2H and 1T phases. Set points of the STM images: a: 1.5 V, 50pA; b: 1 V, 10 pA; d: 2 V, 10 pA; e: 0.5 V, 50pA. Set point of dI/dV spectra:1.5 V, 50 pA c. f Projected density of states (PDOS) of S and H atoms at the phase boundary before and after hydrogenation. Blue curve: PDOS of S atoms before hydrogenation, black curve: PDOS of S atoms with H bonded, red curve: PDOS of absorbed H atoms. Scale bar: 2 nm a, 0.7 nm b, 1.5 nm d, 0.7 nm e