Scanning tunneling microscopy measurements of local surface photovoltage of the Si(001) surface reveal the existence of local charging produced by the tunneling current. Since the tunneling current is confined to a region of near atomic dimensions, charge transport between surface and bulk electronic states is probed with high spatial resolution. The surface charge is enhanced while tunneling at the bonded, type-B atomic step and at specific point defects demonstrating atomic-scale variations in the charge dynamics
