Engineering of semiconductor nanocrystals and metal Ions in amorphous materials

Abstract

Semiconductor nanocrystals (NCs), metal ions containing glass based materials have applications in design engineering, and may solve many technological problems. P2O5 based glasses are an important class of materials for several applications, especially for high power laser. Recently, the construction of semiconductor NCs-based phosphate glass materials has been shown to be of high importance for various applications, like in photovoltaics, LEDs, lasers and spintronics. The major challenges are the intentional insertion of dopants into semiconductor NCs aiming expanding their intrinsic functionalities and the scalable incorporation of NCs into host free of hydroxyl and organic species for stabilizing and integrating their performances. On the other hand, the low refractive index of phosphate glass can be adjusted by the addition of a high index of TeO2 content. These hybrid materials fulfil the requirement of refractive index contrast for chromatic dispersion control and are useful for the design of photonic materials. The thesis focus on the design of ZnNiTe semiconductors in transparent phosphate glass-ceramics, and the effect of TeO2 environment in Nd3+ doped phosphate glass for optoelectronic and solid-state laser applications. The structural features of these materials have been determined by XRD, FT-IR and Raman spectroscopic techniques. Optical properties were characterized by using UV-Vis-NIR absorption and fluorescence spectroscopic techniques. The findings were used to estimate crystal field interaction parameters, coordinate state of Ni2+ ions, Judd-Ofelt intensity parameters for Nd3+ ions and radiative properties of metal ions in glasses. Thermal diffusivity (D) and thermal conductivity (K) of ZnNiTe NCs in glasses were determined using thermal lens (TL) and thermal relaxation (TR) techniques. The results revealed that the behaviors of D and K for the studied samples are similar. Nonlinear optical properties of ZnNiTe NCs glasses were also studied using Z-scan technique. The nonlinear refractive property is observed only in the sample containing 5% Ni. Other samples with 1.0% to 10% of Ni content presented nonlinear absorption nature. This suggests that the absorption coefficient, β does not change significantly with the wavelength, but increase with Ni concentration, with confinement effects and two-photon absorption (TPA).