Arsenic vacancy, imaged at −1.3 V.
Formation and imaging of surface-layer CoGa acceptor. Scale bars are 1 nm. (a) A Co adatom imaged at (−1.3 V). (b) By ramping the voltage up to >1.7 V, the Co has been inserted into the surface, displacing a Ga atom. (c) and (d) The CoGa acceptor imaged at [(c) −1.3 V and (d) +1.55 V]. Adapted from Ref. 16 .
(Color online) (Inset) STM image showing tip locations for tunneling spectroscopy off-CoGa (a) and on-CoGa (b). Scale bar is 1 nm. Off-atom, one peak (α) is observed, while on-atom, two (β,γ) are observed.
(Color online) (a) STM images of Co acceptor (black arrow) with V As (white arrow) at three different distances d. (b) dI/dV spectroscopy showing shifts of α, β, and γ peaks for three distances. (c) Plot of peak shifts vs d, with Coulomb 1/d fits (solid lines).
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