Investigation Of Physical Properties On Gesb(As)Se Glasses

Chalcogenides are important amorphous materials formed primarily from one or more of the chalcogen elements(S, Se, Te), covalently bonded with the network forming elements such as As, Ge, Si, Sb, etc. They are important and have widely been applied in various fields that include phase-change optical memories, solar cells, and optical waveguides. They are promising for photonics because they have attractive optical properties which include high linear and nonlinear refractive indices, high photosensitivity, and exceptional transmission range spanning from the visible to the mid-infrared. Generally, we can tune their properties via changing glass components. Over the past decade, various applications have been developed including chalcogenide planar waveguides for high speed all-optical processing of telecommunications signals and chalcogenide optical fibres and waveguides for chemical sensors. Besides, we have further investigated the preparation technology of nanoparticles by pulsed laser ablation in liquid media to meet demands of micro-devices in applications. The following five sections are included in this thesis:(1) The analysis of Ge As(Sb)Se glasses by Raman scattering spectra. In this respect, we measured Stokes and anti-Stokes Raman scattering spectra of GexSb(As)10Se90-x, GexSb15Se85-x and GexSb(As)20Se80-x glasses at a range from-450 to 450 cm-1. Nicolet 6700 FT-IR Spectrometer with an excitation wavelength of 1064 nm was used to record the spectra. The evolutions and physical significance of Raman shift peaks have given particular evidences to understand the network of these glasses.(2) The discussion of free assembled mechanism about GeAsSe structure by using Peak-fitting method. In order to understand the evolution of chemical structure in glasses, Raman features were fitted into different peak-fitting functions, including Gaussian and Lorentzian types. Comparing the fitting results between Gaussian and Lorentizian, we found out the microscopic mechanism of broadening Raman peaks and further analyzed the importance of Short-Range Structure, Medium-Range Structure and defects in chalcogenide glasses.(3) The demonstration of the viability of Raman scattering method for thermal conductivity measurements. We developed an unconventional approach for the noncontact measurement of the thermal conductivity using the shift of the temperature-sensitive Raman peak. Compared with traditional methods, this method was demonstrated to be a simple, easy, time-saving and practical, which opens a new path on the measurement of thermal conductivity. This paper has demonstrated strictly the viability and creditability of Raman scattering method from theory principles and experiments.(4) Systematically measuring thermal conductivities of GeAs(Sb)Se chalcogenide glasses and understanding the role of chemical composition in determining thermal conductivity of the chalcogenide glasses. We estimated the temperatures of each sample under different laser irradiation powers by the ratio of Stoke and anti-Stokes scattering cross-section, and further calculated the corresponding thermal conductivities by these temperatures as a function of laser power. Our results provided direct evidence to understand the evolution of network structure on chalcogenide, which is beneficial to tune the physical properties by changing the components.(5) Preparing Zn S nanoparticles with pulsed laser ablation in liquid media and systematically investigating properties of the nanoparticles. We had successfully prepared ZnS nanoparticles in deionized water with 355 nm and 500 mW pulse laser from Nd:YAG laser and systematically investigated the particle size, structure and component by high-resolution transmission electron microscopy(HTEM), selected area electron diffraction(SAED) and energy dispersive spectroscopy(EDS). All measurement results shown that all the nanoparticles in sphalerite structure with average particle size below 10 nm, and pulsed laser ablation in liquid is effective and promising to nanoparticles with controllable size in large scales.