(a) The measured I-V spectra on an n-type Si(111) substrate with . The tip position is set by the bias at +4 V with current varying from 2 nA (non-contact) to 4.5 nA, 10 nA, and 20 nA (all in contact). (b) Simulated I-V curves using a Schottky barrier model and Eq. (4) with ϕB=0.45 V.
(a) The I-V spectra taken on an n-type heavily doped silicon with . The tip position is set by a current of 10 nA at various bias voltages from 0.5 V (non-contact) to 0.4 V, 0.3 V, 0.2 V, 0.05 V, and 0.001 V (all in contact). (b) A 135 nm × 135 nm STM topographic image on the tip-sample contact area. The line profile across the hole indicates that the ultimate contact area was ∼24 nm in diameter and 3-4 nm in depth. (c) The simulated I-V curves using a constant ϕB = 0.45 V with different fictitious contact radii, RC, ranging from 3 to 10 000 nm. (d) The simulated I-V curves with Rtip = 20 nm and RC = 12 nm but various ϕB ranging from 0.45 V to 0.15 V.
(a) Schematic of the STM tip contact with a semiconductor substrate with the depletion region in spherical symmetry. The sample is grounded and the tip is applied with a bias voltage, V. The corresponding energy diagrams at (b) zero bias, (c) forward bias (V>0), and (d) reverse bias (V<0), on which the Schottky barrier height, ϕB, the conduction band bottom edge, EC, the valence band top edge, EV, and the Fermi levels are labeled. The potential shapes due to the Schottky barrier and the image potential are shown.
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