Investigation of resistive switching in SiO₂ layers with Si nanocrystals

MOS structures with two-layer insulator, SiO₂/SiO_x, are tested for switching between high and low resistance state. Part of the structures were annealed at 1000 °C for 60 min in N₂ in order to form silicon nanocrystals (Si NCs) in a SiOx matrix. Cross-sectional transmission electron microscopy revealed that after the high temperature annealing phase separation takes place and nanocrystals with size of ∼ 4–5 nm are formed. Direct current–voltage measurements showed that bipolar switching occurs only in the annealed c–Si/SiO₂/SiO_x/Al structures and not in the control samples. A model explaining the resistance change by electric field formation of conductive pathway in the SiO_x-Si NCs layer at negative gate voltages and current driven destruction of the conductive filament at positive voltages was verified by high frequency capacitance-voltage (C-V) measurements. From the C-V results the dielectric constant of non-annealed SiO_x films with x = 1.3 was calculated to be ε_SiOx = 4.6. (paper)