Imaging of stored charges in Si quantum dots by tapping and electrostatic force microscopy

We studied the charge storage and subsequent imaging of silicon quantum dots (SiQD) embedded in a 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.