Papers by Author: Bernd Schmidt

Abstract: Scanning transmission electron microscopy (STEM) in combination with electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) have been used to investigate Si+-implanted amorphous silicon dioxide layers and the formation of Si nanoclusters. The microstructure of the Si doped silica films was studied by energy filtered transmission electron microscopy (EFTEM) in a 200 kV FEI Tecnai F20 TEM. The samples were amorphous, thermally grown 500 nm SiO2 layers on Si substrate doped by Si+ ions with an energy of 150 keV up to an atomic dopant fraction of about 4 at%. A thermal post-annealing leads to formation of silicon clusters with sizes 1-5 nm and concentrations of about 1018 cm-3. Respective cathodoluminescence spectra in the near IR region indicate such structural changes by appearance of an additional band at 1.35 eV as well as additional emission bands in the visible green-yellow region.

Abstract: Nanocrystal memories are attractive candidate for the development of non volatile memory devices for deep submicron technologies. In a nanocrystal memory device, a 2D network of isolated nanocrystals is buried in the gate dielectric of a MOS and replaces the classical polysilicon layer used in floating gate (flash) memories. Recently, we have demonstrated a route to fabricate these devices at low cost by using ultra low energy ion implantation. Obviously, all the electrical characteristics of the device depend on the characteristics of the nanocrystal population (sizes and densities) but also on their exact location with respect to the gate and channel of the MOS transistor. It is the goal of this paper to report on the main materials science aspects of the fabrication of 2D arrays of Si nanocrystals in thin SiO2 layers and at tunable distances from their SiO2/interfaces.