Extended Data Fig. 7: Characterizing the bistable terahertz resonator defect in GaAs(110).
a, Three-dimensional (3D) view of a constant height scan at Vd.c. = 1.2 V and ESF,pk = 50 V/cm (image size 7 nm × 7 nm). The 3D texture is represented by log10[Id.c.(x,y)] using a colormap that ranges from 10 pA (brown) to 500 pA (gold). The simultaneously recorded rectified charge, QTHz(x,y), is superimposed with a colormap that ranges from –20 e/pulse (blue) to –5 e/pulse (transparent). b, Conventional STM current–voltage (I–V) characteristics acquired on the bistable defect at z = z0 (red curve) and z = z0 + 400 pm (black curve). The height, z0, was set by Vd.c. = 1.2 V and Id.c. = 100 pA on the defect. The red and black dotted lines are guides to the eye for the voltage at which the silicon dopant moves 400 pm to an adjacent vacant gallium lattice site. c, Scatter plot showing the current and voltage at which the bistable defect jumped back and forth between the two lattice sites. Defect motion was induced by I–V curve sweeps (ESF,pk = 0 V/cm) and each point in c was determined based on the position of the discontinuous step in an I-V curve. d, STM (top) and simultaneously recorded THz-STM (bottom) images acquired in sequence (1–4). I–V curves were performed between scans at the position of highest QTHz in the preceding scan to move the defect between the two adjacent lattice sites (Images: Vd.c. = 1.2 V, Id.c. = 100 pA, ESF,pk = 50 V/cm). e,f, STM image (e) and simultaneously acquired THz-STM image (f) witnessing a defect hop that occurs at the dashed red line (Vd.c. = 1.2 V, Id.c. = 100 pA, ESF,pk = 75 V/cm).
