Browsing by Author "Ke, Jhih-Syuan"

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Controlled growth of beta-Na0.24V2O5 nanowire thin films
(2012-10-01)
Ke, Jhih-Syuan
;
Wu, Ming-Cheng
;
Weng, Sheng-Feng
;
Lee, Chi-Shen
;
應用化學系
A method to prepare well-aligned beta-Na0.24V2O5 nanowires (NWs) involves the deposition of a vanadium oxide complex onto a substrate via gaseous transport, followed by a reaction between the complex and a sodium cation (Na+) precursor coated on the substrate. Techniques to investigate the composition, crystallinity, and morphology of products as prepared include ICP-AES, X-ray powder diffraction (PXRD), SEM/transmission electron microscope (TEM), and XPS. PXRD patterns and images from a TEM confirm the single-crystalline nature of beta-Na0.24V2O5 NWs, which grow along direction [1 0 0]. Factors affecting the amount of deposited material and morphology were tested. On varying the reaction conditions, the length of the beta-Na0.24V2O5 wires is controlled in a range of 5-25 mu m. A mechanism of formation is proposed. According to measurements of field emission, the turn-on field is 7.8 V/mu m, and the maximum emission current density of 4.66 mA/cm(2) occurs at field 11 V/mu m. This method is applicable to grow other tertiary metal oxide nanostructures on glass substrate.
Controlled synthesis of VO2(R), VO2(B), and V2O3 vanadium-oxide nanowires
(2013-07-01)
Ke, Jhih-Syuan
;
Weng, Sheng-Feng
;
Wu, Ming-Cheng
;
Lee, Chi-Shen
;
應用化學系
Vanadium-oxide nanowires (NWs) V2O5, VO2(R), VO2(B), and V2O3 are deposited on a substrate to study their field-emission properties. V2O5 NWs are prepared by thermal evaporation via vapor transport of a vanadium-oxide complex under mild conditions. Films of VO2 and V2O3 wires are subsequently prepared by reducing V2O5 one-dimensional nanocrystals at 450 degrees C with hydrogen gas. The composition of the flowing H-2/Ar mixture and the duration of reduction are utilized to control the formation of VO2(R) or VO2(B) NWs. The crystallinity and morphology of products as prepared are characterized using several techniques, including powder X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The field-emission properties of the vanadium-oxide NWs as prepared exhibit a turn-on field of 4.56-7.65 V/mu m and an emission current density up to 3.68-8.36 mA/cm(2). These features indicate that vanadium-oxide NWs have potential FE emitter applications.