Reversible charging effects in Sio₂ films containing Si nanocrystals

Reversible charging effects are observed in metal-insulator-semiconductor structures which have been ion implanted and annealed to produce Si nanocrystals in the insulating SiO₂ layer. The shifts in current-voltage (I-V) and capacitance-voltage (C-V) curves are induced by forward constant voltage stress or UV light exposure, and can be explained by hole charging of the nanocrystals in the insulator layer. A reverse constant voltage stress is shown to recover the original I-V curve and partially recover the original C-V curve. For a sample implanted with a Si dose of 3 × 10¹⁶Si cm^-2, the voltage shift of the I-V curve produced by a forward voltage stress of V = -10 V for 5 s is 1.2 V, which is shown to be in reasonable agreement with simple estimates based on nanocrystal charging.