Formation and charging effect of Si nanocrystals in a-SiNx/a-Si/a-SiNx structures

The sandwiched structures with a layer of amorphous silicon (a-Si) between two a-SiNx layers have been fabricated by plasma enhanced chemical vapor deposition technique. Si nanocrystal (nc-Si) layer was formed by crystallization of the a-Si layer according to the constrained crystallization principle after thermal annealing at 1100degreesC for 30 min. Transmission electron microscopy (TEM) and Raman scattering spectra showed that nc-Si grains were formed in the as-deposited a-Si layer after the annealing with a mean size about the same as the thickness of the as-deposited a-Si layer, and the density of the order of 10(11)-10(12) cm(-2). Charge trapping and storage in nc-Si were exhibited in capacitance-voltage (C-V) measurements at room temperature through the hysteresis and shift of the flat-band voltage (DeltaV(FB)) of the nc-Si samples after a dc voltage was imposed. The density of nc-Si grains estimated from the DeltaV(FB) was consistent with the results of TEM observation. The origin of the hysteresis phenomena and mechanism of the charge storage were discussed in detail. (C) 2004 American Institute of Physics.