Coulomb interaction controlled room temperature oscillation of tunnel current in porous Si

A novel phenomenon of regular oscillations is observed in I-V characteristics of porous silicon under illumination by visible light. The measurements are performed at room temperature using a scanning tunneling microscope. The heights of the oscillation peaks appear to be a linear function of the oscillation number. The experimental value of the Coulomb energy determined from the oscillation period is much smaller than k B T. The oscillations are attributed to a Coulomb effect, i.e., to the periodic trapping of a multielectron level in a quantum well within a Si nanocrystal under the combined influence of the voltage variation at the STM tip and the Coulomb interaction among the carriers.