| Summary: | 碩士 === 國立東華大學 === 物理學系 === 102 === Two-dimensional (2D) crystalline Bi2Te3 nanoplates were fabricated by a solvothermal method. Organic surfactants of polyvinylpyrrolidone (PVP). Bismuth (III) oxide (Bi2O3) and tellurium dioxide (TeO2) were used for sources of Bi and Te, respectively. The solvothermal method was processed in an autoclave at 200 ºC, and ethylene glycol (EG) and sodium borohydride (NaBH4) were exploited as solvent and reducing agent, respectively. During the solvothermal reaction, the 2D crystalline Bi2Te3 nanoplates were monodispersively synthesized. The structures and morphologies of the Bi2Te3 nanoplates were characterized via field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The FESEM images showed that the as-prepared Bi2Te3 nanoplates are hexagonal with edge lengths of ~100-150 nm. Chemical quantitative analysis from XPS verified that the Bi2Te3 nanoplates consist of only Te and Bi, and the elemental ratio of Bi:Te is 2:3. Room-temperature XRD results demonstrate the Bi2Te3 nanoplates to be a hexagonal phase in space group R-3m with lattice constants of a = b = 4.38 Å, c = 30.48 Å, α = β =90º, and γ = 120º. The selected area electron diffraction (SAED) patterns of the Bi2Te3 nanoplates are in good agreement with the XRD results. The variable XRD results demonstrates that the volumes of the 2D Bi2Te3 nanoplates expand and contract at low and high temperatures, indicating that thermal contraction occurs in the 2D Bi2Te3 nanoplates.
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