Abstract
化學氣相沈積法(Chemical Vapor Deposition，CVD)被廣泛應用於成長固 態薄膜層與製備微細粒子，此法為氣相形成固態膜或微粒子之一種化學反 應程序。在本論文中以四異丙烷氧化鈦(titanium tetraiso-propoxide， TTIP)和四乙基烷氧化矽(tetraethyl orthosilicate，TEOS)為反應物， 經以減壓化學氣相沈積法製備二氧化鈦(titania，TiO2)和二氧化矽( silica，SiO2)混合粒子。由吾人之研究中發現，改變TTIP濃度並不影響 粒子沈積形態，主要受到基材表面影響，表面愈是粗糙則產生較立體化的 粒子。而於本系統中粒子的沈積位置和形態有一定的模式，於入口處為龜 裂之薄膜，在此處為單獨TiO2的成份，於波峰處則為緻密的粒子沈積，此 處含有TiO2和SiO2的混合粒子，出口處則為鬆散的超微粒子堆積，生成粒 子的附著力很差。尾端收集的混合粒子經由XRPD鑑定，為TiO2銳鈦礦( anatase)晶相和可能是SiO2白矽石(cristobalite)的晶相，經由在空氣中 以900℃高溫退火4小時，發現銳鈦礦晶相增強，白矽石晶相則減弱，且沒 有TiO2金紅石(rutile)晶相產生。當調整不同TTIP/TEOS濃度比時，由 SEM/EDX和TEM/EDX元素分析發現，隨著TTIP濃度之增加，Ti對Si在產物中 之相對量增加，但是增加到一定程度便趨於緩和，降低反應溫度，Si元素 在產物中之含量有明顯減少。 Chemical vapor deposition (CVD) has wide applications in growthing thin solid films and producing fine powders. The method is a basically synnthesis of thin solid film or fine particles from gaseous reactants. In my thesis, the precursors are TTIP and TEOS. Mixed powders of TiO2 and SiO2 are produced by the reduced pressure CVD process.In my research, the morphology of the coated particles is not effected by variation of the concentration of TTIP. The surface of the substrate is found to be the dorminant factor. The rougher the substrate surface is, the clear the particles phase is. The film formed near the entrance is cracked, and contains TiO2 only. At the peak region of the deposition flux curve, the layer formed by particles deposited is dense and compact, and contains mixed TiO2 and SiO2 particles. At the exit area, the deposite areThe X-ray diffraction patterns of the mixed powders collected at the exit area show that particles TiO2 are in anatase phase and SiO2 particles are likely in cristobalite phase. When annealed at 900℃ in atmosphere for 4 hours, the anatase phase becomes more evident, but the cristobalite phase relatively weakens. The rutile phase of TiO2 does not show up.Based on SEM/EDX and TEM/ EDX analysis results, we find that Ti/Si ratio in the product increases with increasing the TTIP/TEOS ratio. But this increase tends to saturate. At a lower reaction temperature, the Si content in the product drops sharply.