Si-NCs embedded in dielectric matrices

Abstract In this chapter, we present a novel analytical strategy, useful in order to probe structural and electronic properties of single silicon nanocrystals (NCs) embedded in a dielectric matrix. We tested this strategy in three systems with different embedding dielectric matrices (SiO 2 , SiC, and Si 3 N 4 ). Experiments were performed using a monochromated and aberration corrected Titan low-base microscope, operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. Then, a novel analysis approach allowed to disentangle the electronic features corresponding to pure Si-NCs from the spectral contribution of the surrounding dielectric materials, trough an appropriate computational treatment of hyperspectral datasets. First, the different materials were identified by measuring the plasmon energy. Notice that due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty for non-linear fitting methods to identify and separate the components in the EELS signal. We managed to solve this problem for the silicon oxide and silicon nitride systems by applying multivariate analysis (MVA) methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC and dielectric signal components. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus separated, studied, and compared with the crystalline silicon from the substrate and with the dielectric material in the matrix.