Highly improved optical properties of silicon nanowires by deposition of Poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] polymer

Abstract

This paper reports on the effect of the Poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) deposition on the chemical composition and the optical properties of silicon nanowires (SiNWs). The SiNWs were obtained by a single-step Ag-assisted chemical etching method, and then coated by MEH-PPV polymer using the electroless dipping method. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transformed Infra-Red (FTIR) spectroscopy were used to probe the deposition of the polymer on the SiNWs surface and its chemical interaction with them. The optical properties of the elaborated samples were investigated by photoluminescence (PL) spectroscopy. The PL spectra show that the PL emission range of the nanowires is practically the same as that of the MEH-PPV. We also get an enhancement of five orders of the integrated PL intensity of MEH-PPV/SiNWs sample compared to that of untreated SiNWs sample. The PL intensity enhancement is attributed to the luminescent centers of MEH-PPV molecules as well as the passivation of silicon nanowires surface. Interchain and intrachain transitions in the polymeric layer as well as the carriers transfer between SiNWs and MEH-PPV are the main sources of the multiband PL spectra.