Abstract
We have studied time evolution of spatial distribution of charges stored in one-dimensionally self-aligned double-stack of Si quantum dots (QDs), which were formed on thermally-grown SiO2 with an areal dot density as high as ～1013 cm-2, by surface potential measurements using an atomic force microscope (AFM)/Kelvin probe technique. Electron injection to and emission from the Si-QDs were initially carried out by scanning the surface with an electrically-biased AFM tip in a tapping mode. A stepwise decay in the surface potential accompanied with a gradual change in the potential profile after electron injection can be interpreted in terms that the electron transfer from the upper dot to the lower dot for a stable charged state and the propagation of electron tunneling to neighboring dots proceed simultaneously. In addition, the temporal change in the surface potential after electron extraction shows early propagation of hole tunneling to neighboring dots and progressive hole tunneling from the upper dot and the lower dot but less. These results suggest that Coulomb interaction among charged dots plays a role in the time evolution of charge distribution in the closely-arranged Si-QDs.
