Synthesis And Optical Properties Of Tm³⁺/Yb³⁺ Co-doped Calcium Fluoride Thin Film And Micro-spheres

With the rapid development of the information industry, the human society is accelerating into the information ages. A variety of electronic products with high precision are emerging. More and more attentions are paid to the electronic monitors, especially the flat panel display. They are generally characterized by their thin, light, low voltage and power which can also be applied to the digital technology. Therefore, the searching of more advanced preparing technique of low-latitude materials is beconing the main content of scientific research. Among these materials, thin films arouse wide concern whith their special advantages. The preparation methods of thin films contain: vacuum evaporation, magnetron sputtering, electron beam evaporation, metal organic chemical vapor deposition, atomic layer growth method and orientation of sol-gel method and so on.The synthesis of inorganic micro- and nanostructures with controlled shape and composition is of fundamental and technological interest for wide range applications in microelectronic, optoelectronic, catalysis, and bio-sensing. As a consequence, great attention has been paid to frequency up-conversion (UC) from infrared (IR) to visible/ultraviolet (UV) in rare earth activated inorganic materials. In order to achieve more intensive UV up-conversion luminescence,various upconversion host materials doped different rare earth ions and with different morphology have been synthesized and studied. Such as: nanorods, nanotubes, nanowires nanobelts and thin films in nanoscale. In comparison with the other systems, fluoride possess optical transparency over a wide wavelength range and very low vibrational energies which make the quenching of the upconversion luminescence of the rare earth ions minimal. Which make fluoride as one of the matrix materials those people paid much attention to. The introduction of Yb³⁺ as a sensitizer at around 1μm pumping wavelength, allows a large enhancement of UC fluorescence of lanthanide ion activators. Tm³⁺ is a promising optical activator that provides the possibility for simultaneous blue and UV emissions of laser action and various applications. At prescent, the preparation of high efficient upconversion luminescence materials and the upconversion mechanisms of the materials become an urgent problem to be solved. The main contents in this thesis are as follows:1. Yb³⁺ and Tm³⁺ co-doped CaF₂ thin film was synthesized by a facial sol-gel method. The thin film in nano-scale had a uniformal surface. Strong ultraviolet up-conversion emissions from the CaF₂ microspheres were observed in the spetrum. After secondary growth under hydrothermal, large amount of sub-micron balls were closely packed on the sol-gel prepared thin films. Blue and ultraviolet up-conversion emissions were tested under the irradiation by 980 nm laser diode, no obvious changes were observed. The intensity of the ultraviolet upconversion emission from ¹I₆→³F₄(～347 nm) and ¹D₂→³H₆(～362 nm) transitons was also stronger than that of the blue upconversion from ¹D₂→³F₄(～452 nm) and ¹G₄→³H₆(～476 nm) transitions.2. Yb³⁺, Tm³⁺ co-doped CaF₂ micro-spheres composed of large amount of nano-spheres have been prepared by a facial hydrothermal method and annealing treatment. Intense ultraviolet, visible, and near infrared (NIR) upconversion luminescence was observed under the excitation of the 980 nm laser diode. In the experiment, the hydrothermal time was varied. The diameter of the synthesized sphere increased from nanoscale to micronscale. When the reaction time reached 48h, the morphology of the particles became very irregular. The up-conversion luminescence spectra of the micronscale materials showed the characteristics of bulk materials. The red upconversion emissions from ³H₄→³H₆ transition was significantly enhanced. Materials with different morphologies were obtained through the addition of mineralizer and the change of solvent and surfactant. The formation mechanism of the samples was studied. Additionally, the phenomenon of ultravilot conversion enhancement was discussed...