Fabrication and characterization of rare earth doped wide bandgap semiconductors for spectral storage

Powder samples of MgS and CaS, singly doped with Eu and doubly doped with Eu and Ce, were synthesized for their usage in spectral storage. Thin films of these materials were fabricated using the pulsed laser deposition (PLD) technique. This fast and simple technique is superior to the single crystal growth or molecular beam epitaxy (MBE) as far as the storage material requirements are concerned. High optical quality films of MgS:Eu and CaS:Eu have been grown and tested.; Polycrystalline powder samples of MgS and CaS were synthesized using high temperature reduction of commercially available magnesium and calcium sulfates. These materials were singly doped with rare earth lanthanides using high temperature diffusion in powder forms. Rare earth lanthanide impurities in very small concentrations are necessary for optical applications such as spectral storage for which all the materials prepared during the course of this study were made.; Thin films of rare earth doped calcium and magnesium sulfides have been produced by using pulsed laser deposition (PLD) technique. Coating of the reactive surfaces of the PLD chamber with SiC has been performed to make them resistant to the corrosive environment and the by products of the deposition process.; Solid targets needed for thin films were fabricated from the synthesized polycrystalline powders by high-pressure cold compression technique. Deposition of thin films of CaS and MgS has been performed and to protect these films from the environment, capping layers of aluminum oxide (Al2O 3) or ZnS have been deposited over the CaS and MgS thin films.; In magnesium sulfide, oxygen doped magnesium sulfide and calcium sulfides, europium centers occur in different spectral regions. Therefore, multi-layer thin film structures were fabricated to allow for higher density of spectral storage.; Various characterization techniques such as optical microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy have been used to study the micro-particles samples. Surface profilometery was used to study thin film samples.; Characterization and material testing using high-resolution laser induced fluorescence spectroscopy and spectral holebuming are quite unique and necessary for the materials prepared in the present study. However, optical studies are beyond the scope of this project. Therefore, low temperature laser excited fluorescence and holebuming data has been presented to support the success of the fabricated thin films for spectral storage. Such studies are completely independent and self-contained investigations performed by other members of the group.