Linear electro-optical behavior of hybrid nanocomposites based on silicon carbide nanocrystals and polymer matrices

Abstract

An electro-optical activity has been recently reported for hybrid nanocomposite thin films where inorganic silicon carbide nanocrystals $(\mathrm{ncSiC})$ are incorporated into polymer matrices. The role of the interface $\mathrm{SiC}$ polymer is suggested as the origin of the observed second order nonlinear optical susceptibility in the hybrid materials based on poly-(methylmethacrylate) (PMMA) or poly-($N$-vinylcarbazole) matrices. In this work, we report an analysis of the electro-optical response of this hybrid system as a function of the $\mathrm{ncSiC}$ content and surface state in order to precise the interface effect in the observed phenomenon. Two specific $\mathrm{ncSiC}$ samples with similar morphology and different surface states are incorporated in the PMMA matrix. The effective Pockels parameters of the corresponding hybrid nanocomposites have been estimated up to $7.59\ifmmode\pm\else\textpm\fi{}0.74\phantom{\rule{0.3em}{0ex}}\mathrm{pm}∕\mathrm{V}$ ($1\phantom{\rule{0.3em}{0ex}}\mathrm{wt}.\phantom{\rule{0.2em}{0ex}}%$ of $\mathrm{ncSiC}$ in the matrix). The interfacial region $\mathrm{ncSiC}$ polymer is found to play the main role in the observed effect. Particularly, the electronic defects on the $\mathrm{ncSiC}$ nanocrystal surface modify the interfacial electrical interactions between the two components. The results are interpreted and discussed on the basis of the strong influence of these active centers in the interfacial region at the nanoscale, which are found to monitor the local hyperpolarizabilities and the macroscopic nonlinear optical susceptibilities. This approach allows us to complete the description and understanding of the electro-optical response in the hybrid $\mathrm{SiC}$/polymer systems.