| Summary: | 碩士 === 中原大學 === 物理研究所 === 99 === This paper focuses on the fabrication of tri(8-hydroxyquinolinate)aluminium (Alq3) and 8-hydroxyquinoline (8Hq) crystals from physical vapor transport (PVT) method and the properties of these crystals characterized by photoluminescence (PL), UV-visible absorption spectroscopy (UV-visible), Fourier Transform Infrared Spectroscopy (FT-IR), and Powder X-ray Diffraction (XRD). First, from FTIR, PL, uv-vis, and XRD, the as-received Alq3 powder is confirmed to have meridional structure (mer-Alq3) with mixed phase, and after thermal treatment at 395℃, the facial structure (fac-Alq3) with δ-phase is obtained. Then, by using these two different source (mer-Alq3 and fac-Alq3) powders, the side-wall deposition due to constitutional supersaturation (CSS) in PVT is observed. From a control of different transport vapors (N2, O2, dry air, or wet air) inside the PVT tube with various vapor pressures (1 ~ 700 torr), the side-wall deposition of Alq3 and 8Hq are observed to occur at 100 ~ 270℃ and at room temperature, respectively. Furthermore, the deposition of Alq3 has two different crystal phases depending on the source powder. The β-Alq3 is obtained from mer-Alq3 source powder and α-Alq3 from fac-Alq3 source powder. This phenomenon can be explained by a picture associated with activated barrier crossing diagram. Finally, by using various transport gases but with a fixed pressure of 400 torr, the formation mechanism of 8Hq crystals is found to be strongly related to the content of H2O. In dry gases, needle-like 8Hq crystals are formed preferential; while in wet gases, the side-wall is compactly covered by 8Hq with short needles. The content of H2O inside the PVT tube is believed to play an important role to the dissociation of Alq3 and to the side-wall deposition of 8Hq.
|
|---|
