Charge storage characteristics have been investigated in metal-oxide-semiconductor memory structures based on silicon nanocrystals, where various interface traps and defects were introduced by thermal annealing treatment. The observations demonstrate that traps have strong influence on the charge storage behavior, in which the traps and defects at the internal/surface of silicon nanocrystals and the interface states at the SiO2/Si substrate play different roles, respectively. It is suggested that the injected charges are mainly stored at the deep traps of nanocrystals instead of the conduction band in long-term retention mode. The long-term charge-loss process is dominantly determined by the direct tunneling of the trapped charges to the interface states in the present experiment. An optimum way to improve the retention time would be to introduce a certain number of deep trapping centers in nanocrystals and to decrease the interface states at SiO2/Si substrate.

The quantum mechanical effects in silicon single-electron transistors have been investigated. The devices have been fabricated in the form of point contact metal–oxide–semiconductor field-effect transistors with various channel widths using electron beam lithography and the anisotropic etching technique on silicon-on-insulator substrates. The device with an extremely narrow channel shows Coulomb blockade oscillations at room temperature. At low temperatures, negative differential conductances and fine structures are superposed on the device characteristics, which are attributed to the quantum mechanical effects in the silicon quantum dot in the channel. The energy spectrum of the dot is extracted from the experimental results.

We have developed a very controllable fabrication process of an extremely narrow (∼10 nm) quantum wire metal-oxide-semiconductor field-effect transistor (MOSFET) on a separation-by-implanted-oxygen (SIMOX) substrate using anisotropic etching and selective oxidation technique. The drain current versus gate voltage characteristics show oscillations caused by Coulomb blockade even at room temperature. The oscillations split into several sharp peaks when the temperature is decreased, indicating that the channel is separated by several serial coupled quantum dots and that the quantum levels of these dots correspond to the observed fine peaks.