| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系 === 91 === In this experiment , RF-sputtering deposition method was applied to prepare CdSe-doped glass thin film which can be used as the optical switching of red laser. there are two ways to prepare sputtering targets :one is to utilize sol-gel process; another is to put CdSe chips on SiO2 target (chips-on-target method). Chips-on-target method allows both the high-power sputtering and stable process possible and has much convenience. It is preferred as the better way to prepare semiconductor doped glass (SDG) thin film. UV-Visible Spectroscopy and Photoluminescence Spectroscopy (PL) are used to measure the linear optical properties and to estimate the band gap. The results showed that the primary factor affecting the size of the micro-crystals is the concentration of CdSe, whereas the effect due to sputtering power is small. As revealed by the electron Probe X-ray Micro-analyzer (EPMA), the composition in samples prepared by chips-on-target method possesses pretty high amount of CdSe up to 87%. The CdSe-doped glass thin film with fine crystallinity prepared by RF-sputteing at low temperature without heating substrates has been proved by TEM analysis. By analyzing the size of the microcrystals, the size of microcrystals grows as the amount of CdSe increases. Both the analysis of crystalline size and energy gap by PL correspond to the anticipation of the quantum- confinement theory. Z-scan measurement showed that the micro-crystalline glass thin film with the band gap less than that of the laser photon energy provides huge nonlinear absorption effects. The thin film with the thickness of 1 μm reveals that the transmittance change increases as the light intensity and repeating rate increase and the biggest change can be up to 43%. By incorporating all the analyses of absorption coefficient, band gap and Z-scan measurement, the mechanism of this nonlinear absorption effect observed in this experiment is identified as thermal effect.
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