Research On Preparation And Luminescent Properties Of Novel Si Nanocrystals

Si, as the most semiconductor materials in the field of electronic industry, has attracted wide interest since porous silicon (PS) with visible-light emission has been fabricated by L.T.Canham who is an English scientist. And luminescent Si nanocrystals (nc-Si), as 0-dimensional materials, have become one of the hottest issues in the research on Si nanostructres due to their unique quanum confinement effect.In this thesis, we improved photoluminescence (PL) efficiency through changing the crystalline structure of nc-Si, enhanced PL intensity and stability through passivation of Si-Ag bonds in surface of PS, and realized PL simplification, which means PL spectrum with single and narrow peak, through ordering of nc-Si.The research results indicate that fcc nc-Si with blue- and violet-light emission can be prepared by magnetron sputtering with substrate bias, one kind of low-cost and free-pollution method. After comparing characterization between fcc nc-Si and dc nc-Si, we can conclude that although fcc nc-Si contain the intrinsic character of indirect band gap, PL efficiency of fcc nc-Si/SiO2 system is higher than that of dc nc-Si/SiO2 system and the former is latter's 1.2 to 1.6 times.PS with Si-Ag bonds passivation can be prepared by using low-cost, simple two-step technique, combining electrochemical anodization and electrochemical deposition. The research results reveal that PL intensity of passivated PS is 3 times of that of normal PS and PL stability of passivated PS is much better than that of normal PS. PL intensity of passivated PS depend on the number of Si-Ag bonds: at first, PL intensity increase with number of Si-Ag bonds, then PL intensity reach the maximum when Si-Ag bonds are saturated, at last, PL vanish due to superfluous Si-Ag bonds.In addition, we discussed ordering of nc-Si in both theoretical and experimental aspects. In theoretical aspect, we firstly simulated distribution of Si atoms on the amorphous SiO2 buffer layer under the effect of strain field by using Monte Carlo method. The results indicate that Si atoms tend to congregate in some particular zones due to existence of strain field. Therefore, we proved that ordering of nc-Si can be realized under strain field. In experimental aspect, we prepared nc-Si with highest area density (about be 7×1012 cm-2, and is 5 to 10 times of highest density which be reported up to now) by using magnetron sputtering with substrate bias combined with post-annealing. High resolution transmission electron microscope (HRTEM) images and PL spectra with only one PL peak respectively show that partial ordering and PL simplication of nc-Si have been realized.