Study of transition metal dichalcogenides for optical non linearity and memory device applications

Abstract

The different types of memories structures are provided followed by the literature survey, background, motivation and objectives of thesis. Chapter 2 talks over the materials and methods chosen and the details about the instrumentation with their working principles. The sample are characterized by X-Ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), High resolution transmission electron microscopy (HRTEM), UV-Vis spectroscopy, Photoluminescence (PL) spectroscopy, Elemental mapping, Energy dispersive X-ray spectroscopy (EDX), Z-scan technique and the electrical measurements setup. The detailed synthesis method and the structural, morphological and optical results obtained for nanoparticles (NPs) i.e. MoSe2, NiSeatMoSe2 and CoSeatMoSe2 and its PNCs using PMMA and PVA. XRD confirmed the victorious synthesis of MoSe2, NiSeatMoSe2 and CoSeatMoSe2 NPs and also the well dispersion of NPs in PVA and PMMA. The polymer-NPs interaction is studied by FTIR. The surface morphology and particle size is obtained using FESEM and HRTEM images along with the elemental mapping and composition via EDX. The UV-Vis and PL spectra informs about the bandgap and defects present. The third order nonlinear optical properties studied using Z-scan technique, its mechanism, merits and demerits. Various parameters obtained i.e. nonlinear absorption coefficient, nonlinear refractive index and third-order nonlinear susceptibility are discussed. The enhancement in nonlinear factors obtained opens up ways for future optoelectronics. The memory device fabrication method and electrical measurements. I-V, W-R-E-R cycles and endurance studies have been performed to check the switching behavior and the stability of MoSe2-PMMA, NiSeatMoSe2-PMMA, MoSe2-PVA, NiSeatMoSe2-PVA and CoSeatMoSe2-PVA based devices. The Ag/NiSeatMoSe2-PVA/FTO device achieved highest Ion/Ioff ratio of order ~103 while MoSe2-PVA and CoSeatMoSe2-PVA could achieve upto ~102.