Characterization of Si nanocrystals by different TEM-based techniques

Silicon nanocrystals (Si-nc) embedded in SiO(2) matrix and obtained by ion implantation (50keV, 1.0x10(17)Si/cm(2)) were characterized by means of three different transmission electron microscopy (TEM) techniques: Dark Field (DF), Scanning TEM Annular Dark Field (STEM-ADF) and Z contrast. The strengths and weaknesses of each technique for the characterization of the Si-nc were evaluated and discussed. DF imaging, which has the best contrast, was chosen to give the average Si-nc size evaluated to 5.6nm. On the other hand, STEM-ADF, which is only sensitive to the crystalline phase, provided an evaluation of the Si-nc density of 3.27x10(17)nc/cm(3). Finally, comparison between the STEM-ADF and Z contrast imaging permitted to evaluate the amorphous phase remaining after the annealing to around 12%.