Extended Data Fig. 2: QADs on PtTe2 surface after O2 dosing.
a, STM image before O2 dosing, showing several hexamers on the surface. b, STM image after O2 dosing, shows hexamers decorated with different number of protrusions on the corners. The setpoint is VS = − 2.5 V, It = 300 pA. c, Energy diagram for O2 adsorption and dissociation process at Te vacancy site. The inset shows the atomic structure of the initial state (IS), two transition states (TS) and two final states (FS) of the system. Atomic structure for d, O substitution e, O-O substitution at Te vacancy site (both top view and side view) and f, 3V3O2. Note: the supercell (4 × 4 × 3) consisting of three layers of PtTe2 is used in DFT calculations. Only the top layer is present to enhance clarity and better illustrate the adsorption configuration of O atoms at the SV site. Corresponding nc-AFM simulations for h, O substitution, i, O-O substitution and j, 3V3O2. g, STM image at VS = 1mV. k, nc-AFM image for 3V3O2.
