Charge storage in CeO2/Si/CeO2/Si(111) structures by electrostatic force microscopy

An electrostatic force microscope was used to write and image localized dots of charge in a double barrier CeO2/Si/CeO2/Si(111) structure. By applying a relatively large tip voltage and reducing the tip to sample separation to 3–5 nm, charge dots 60–200 nm full width at half maximum of both positive and negative charge have been written. The total stored charge is found to be Q=±(20–200)e per charge dot. These dots of charge are shown to be stable over periods of time greater than 24 h, with an initial charge decay time constant of τ∼9.5 h followed by a period of much slower decay with τ>24 h. The dependence of dot size and total stored charge on various writing parameters such as tip writing bias, tip to sample separation, and write time is examined.