| Summary: | 碩士 === 南台科技大學 === 光電工程系 === 99 === In this study, SixGeyO1-x-y films are deposited by radio-frequency reactive magnetron sputtering using Si/Ge target. During the growth, oxygen flow is fixed to 0.5 sccm. After growth, the SixGeyO1-x-y films are thermal annealed in vacuum. The annealing-induced evolution of microstructure and optical properties are investigated.
Chemical content of the films is extracted by XPS measurement and shows a dependence on RF-gun power and substrate temperature. When the RF-gun power or the substrate temperature is increased, Si and Ge content increase whereas O content decreases. Nano-crystals are formed in the 500℃ annealed films, observed by HRTEM. The size of these crystals is in the range of 2-5 nm and the volume density is 1016-1017 cm-3. When the annealing temperature is increased to 800℃, nano-sized poly-crystals are observed. The size is 3-8nm and the volume density is ~1018 cm-3. After annealing at 900℃, large amorphous clusters are observed. The XRD results indicate that the Si crystals exist in the 800℃ annealed films. This confirms the annealing of SixGeyO1-x-y films could induce the formation of Si nano-crystals. Three peaks centered at ~270 cm-1, ~486 cm-1, and ~520 cm-1 are observed by Micro-Raman measurements for all as-grown films indicating the existence of amorphous Ge-Ge bonds, amorphous Si-Si bonds, and crystalline Si-Si bonds in the samples. The annealed films show signal corresponding to crystalline Ge-Ge bonds (300 cm-1). All the results proved the annealing of SixGeyO1-x-y films is promising to obtain simultaneously Si and Ge quantum dots. The annealed SixGeyO1-x-y films emit strong light in the visible range. The emission is wavelength-tunable by changing annealing temperature.
Light emission device based on SixGeyO1-x-y films is successfully fabricated. When the applied voltage is greater than 6V, the device emits strong white light. The results confirm the feasibility of SixGeyO1-x-y for white light applications.
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