We have observed individual electrons and positive charge both in bulk SiO@sub 2@ and Al@sub 2@O@sub 3@ gate oxides, and trapped on dangling-bond derived states (P@sub b@ centers) at the SiO@sub 2@-Si(111) interface. The charge is observed as sharp virtual holes in the surface topography measured with an Atomic Force Microscope operating in the non-contact mode in ultra high vacuum (UHV). The polarity of the charge was ascertained from contrast differences in Kelvin images that were simultaneously acquired with the topographs. The trapped charges in the bulk of the oxides exhibited a tendency to cluster. The P@sub b@ centers were created by the removal of H from the H-Si interfacial bonds by annealing the Si(111) samples to 600°C. Their densities in the mid 10@super 12@ cm@super -2@ range were measured with the AFM and confirmed by capacitance-voltage experiments. The distributions of the negatively and positively charged (holes) traps are peaked, respectively, in the upper and lower halves of the band gap. This allows the selective capture of electrons or holes that depends on the position of the local Fermi level E@sub F@. E@sub F@ is controlled by the bias applied to the metallic AFM tip. We have modeled the band bending beneath the tip, which, depending on the bias and the binding energy of the trap state, can lead to temporary filling of the trap that leads to unusually sharp features in the images. Thus the trap's physical location and, less directly, the trap level relative to the band edges can be ascertained from these experiments.