Effect of radiation induced methyl methacrylate grafting on structural and optical properties of silicon nanowire

Abstract

Silicon nanowires (SiNWs) is a one-dimensional nanostructured material that had been widely studied due to its potential applications in various fields. Combination of polymers and nanostructured materials offers great potential for enhanced material with many possible applications. This study aims to determine the influence of radiation induced methyl methacrylate (MMA) grafting on structural and optical properties of SiNWs. Six identical SiNWs were prepared using RF magnetron sputtering. Five samples were grafted with MMA by radiation induced grafting under the electron beam dose of 10 kGy, 30 kGy, 50 kGy, 70 kGy, and 90 kGy. The structural analysis of the samples were performed by X-ray diffraction, ATR-FTIR spectroscopy, Raman spectroscopy, FESEM, and EDX spectroscopy while the optical characteristics were measured using UV-vis and photoluminescence spectroscopy. The grafting percentage was in the range of 0.20% to 0.35%. XRD pattern showed new peak appearing at 53° after MMA was grafted. ATR-FTIR and Raman Spectra showed the existence of bonding between MMA and silicon nanowires, which suggest the mechanism of grafting process. These results were also shown in the FESEM images and EDX spectra by the observable MMA layer with thickness in the range of 81.96 nm to 162 nm. The UV-vis absorption spectra showed that the reflectance at the wavelength of 850 nm to 1100 nm was increased as the grafting percentage was increased. Tauc plot showed that the energy band gap increased dramatically from 1.07 eV to 1.17 eV as MMA was grafted and the energy band gap dropped down to 1.12 eV as the grafting percentage is increased. Photoluminescence spectra showed increase of peak intensity as the MMA was grafted on the samples. The structural analyses confirmed that MMA can be combined with SiNWs via radiation induced grafting and the grafting percentage can be increased by increasing the radiation dose of electron beam. The optical characterisations showed that the MMA grafted SiNWs did not strongly affect the optical band gap and the stable absorption at the NIR region still gave this material a great potential for use in photovoltaic, photonics and photosensitive device application.