Fig. 3: STM images.

STM images of aging effect: as-exfoliated (a) and after 10 days of aging (b). Effect of C deposition with varying deposition time: 0 min (as-exfoliated) (c), 10 min (d), and 30 min (e). All scale bars are 40 nm in (a–e), 4 nm for insets of (b) and (d). f The number of defects imaged per frame as a function of the C deposition time. Images were obtained with V_s = −1.0 V and I_t = 0.3 nA. Insets in (b) and (d) are zoomed-in images (V_s = −1.0 V and I_t = 0.1 nA) showing the bright (B) and dark (D) defects. The defects that appeared with aging and after C deposition are the same.