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Published online by Cambridge University Press: 01 February 2011
Thin silicon dioxide (SiO2) on Si layers with embedded germanium nanocrystals (Ge-ncs) were fabricated using 74Ge+-implantation at 15 keV and subsequent annealing. Transmission electron microscopy and Rutherford backscattering spectrometry have been used to study the Ge redistribution in the SiO2 films as a function of implantation dose under specific annealing conditions. At low implantation doses, Germanium is found to segregate at the Si/SiO2 interface leading to poor electrical properties. At higher doses and when the disorder limit of one displacement per atom is reached at the interface, transmission electron microscopy revealed the formation of a Ge-nc layer array located close to the Si/SiO2 interface and an another one inside the SiO2 host material. This near-interface high density (>1012 ncs/cm2) nc-layer is found to act as a floating gate embedded within the silicon dioxide. Capacitance-voltage measurements performed on metal-oxide-semiconductor structures containing such implanted SiO2 layers show significant memory properties (few volts hysteresis) at low programming voltages (<|10V|) due to the presence of Ge-ncs near the Si/SiO2 interface