The charge storage of the nc-Si layer

Sandwiched structures (a-SiNx/a-Si/a-SiNx) have been fabricated by the plasma enhanced chemical vapour deposition technique. A Si nanocrystal (nc-Si) layer was formed by crystallization of an a-Si layer according to the constrained crystallization principle after quasi-static thermal annealing at 1100degreesC for 30 min. Transmission electron microscopy. (TEM) and Raman scattering spectroscopy clearly demonstrated that nc-Si grains were formed in the as-deposited a-Si layer after annealing. The density of nc-Si grains is about 10(11)cm(-2) as shown by TEM photographs. Using capacitance-voltage (C-V) measurements we investigated the electrical characteristics of the sandwiched structures. The charge storage phenomenon of the nc-Si layer was observed from the shift of flat-band voltage (VFB) in C-V curves at a high frequency (1 MHz). We estimated the density of nc-Si grains to be about 10(11)cm(-2) from the shift value of V-FB, which is in agreement with the result of TEM photographs. At the same time, we found that the shift Of VFB increased with the increase of the applied constant dc voltage or the thickness of the nc-Si layer.