We studied the charge storage and subsequent imaging of silicon
quantum dots (SiQD) embedded in a \chem{SiO_2} film by
using atomic-force microscopy (AFM) in tapping and electrostatic
force microscopy (EFM) modes. The controllable deposition of both
positive and negative localized charges in SiQD is
described. The dynamics of the deposited charges is studied and
the charge decay time constant is determined from the
measurements. A simple analysis is presented to explain the
contrast in tapping and EFM images and to quantify the total
amount of stored charge
