Fig. 4: Co_S defect formation and characterization.

a The process of forming a high density of V_S, (b) low-temperature deposition of Co atoms in situ, and (c) subsequent placement into a sulfur vacancy (V_S) with the assistance of the STM probe that is used to selectively manipulate atoms at voltage ranges below −1.3 V is shown schematically. Corresponding scanning tunneling micrographs that capture WS₂/Gr/SiC(0001) (d) after defect introduction via Ar⁺ bombardment and e post Co-deposition are plotted (I_tunnel = 30 pA, V_sample = 1.2 V). Scale bars, 2 nm. STM images (f) before a voltage excitation and (g) after Co substitution within an identified V_S are also shown (I_tunnel = 30 pA, V_sample = 1.2 V, V_excitation = −2.1 V). Scale bars, 2 nm. I_tunnel is the tunneling current, V_sample is the sample bias voltage, and V_excitation is the applied excitation voltage. h The apparent height difference of Co_S compared to adsorption atop as-grown WS₂ is measured to be 0.15 nm, taken from line scans across both (f) (maxima shown with blue dashed line) and (g) (maxima shown with magenta dashed line) red highlighted regions.