| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 92 === Tungsten oxides have been grown by microwave plasma enhanced chemical vapor deposition (MPECVD) directly on silicon substrate without using any catalyst. Due to the unique property of the plasma system, tungsten oxide could be synthesized in just several minutes (three to five minutes). It’s very economic for saving time and costs. In this studies, tungsten oxides have been fabricated in various morphologies, such as nano-rods (20—100nm in diameter), nano-slabs (30—100nm in thickness, 100—500nm in width and 1—2μm in length). Although the cause of different morphologies is still not very clear, from our preliminary observations and analyses, the results suggest that the temperature and the gas flow rate play an important role in the growth of these nano-materials of different morphologies.
The crystal structure and chemical composition of these nano-rods and nano-slabs were identified by the transmission electron microscopy (TEM) and energy dispersion spectrum (EDS), the diffraction patterns show that the nano-rods and nano-slabs are both single crystal. The XRD results and Raman spectra coincide with the analyses of TEM. The cathode luminescence measurements of these nano-materials have also shown in this work and the spectra reveals a red or orange emission. The vapor-solid (VS) mechanism for the growth of these nano-materials is proposed.
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