Extended Data Fig. 10: Tunnel gap spectroscopy on Au(111) with STM and THz-STM.
a,b, Conventional (a) and terahertz-pulse-driven (b) approach curves acquired with the feedback loop disengaged at the tip height, z0, set by V0 = 10 mV, I0 = 300 pA. The apparent barrier height is calculated using ϕ = ħ2/(8 m)·(d ln(I)/dz)2 following an exponential fit, where m is the electron mass, ħ is the reduced Planck constant, and I is the d.c. current (a) or rectified charge (b). The value of ϕ in electronvolts is shown beside each measurement. The measurements in a were acquired with VSF,pk = 0 V, while the measurements in b were acquired with Vd.c. = 0 V.
