利用塊式高分子模板及具圖案奈米洞以溶液成長晶體法來成長二氧化鈦奈米針陣列

Abstract

本論文主要利用塊式高分子及電子束微影法製作奈米模板，並以溶液成長晶體法於奈米模板上成長二氧化鈦單晶態奈米針結構，進一步研究此奈米材料的結構鑑定與特性分析。 第二章主要討論表面改質的二氧化鈦奈米顆粒可因其親水性之不同而分散於PS-b-PMMA塊式高分子中之任何一相，介面活性劑可利用共價鍵結方式與二氧化鈦顆粒表面連結，此法可以使介面活性劑不會脫落而使得奈米顆粒分散於塊式高分子中不至於產生聚集。 第三章討論以Ti離子模式加入PS-b-P4VP溶液中使之分散於PVP相中，在利用旋轉塗佈使之形成單層膜結構，利用氧氣電漿將高分子膜移除後可形成二氧化鈦的晶種陣列，最後再以此晶種以溶膠-凝膠法成長陣列結構的二氧化鈦奈米針，在使用不同分子量的塊式高分子系統中可以發現，不同的分子量所做出的晶種間距不同，因此可以利用此法來操控二氧化鈦奈米針陣列的密度。 第四章討論利用電子束微影的技術製作出不同尺寸大小的奈米洞，並以此奈米洞來成長二氧化鈦，進一步的發現在適當的電場強度下可於30-50 nm尺寸大小的奈米洞中成長出具有單晶態的直立且單根二氧化鈦奈米針，此外不同的起使酸鹼值及尿素添加量亦改變二氧化鈦成長時的機制。 藉由本論文的研究將有助於瞭解以塊式高分子模板成長二氧化鈦奈米結構的機制，此外單一根直立且具有單晶態的二氧化鈦奈米針亦可在適當的操控下成長出來，此種新型態的材料將可用在太陽能電池等光電應用上。

In the thesis, we report that using solution crystal growth method to grow TiO2 nanoneedles via blockcopolymer templates and nanocavities templates from E-beam lithography. The TiO2 nanoneedles crystal structure and properties have been studies in the thesis. In chapter 2, ordered aggregates of surfactant-modified TiO2 nanoparticles in the selective block of lamellar assemblies of the diblock copolymer PS-b-PMMA have been firstly prepared. The hydrophobic or hydrophilic nature of the tethered surfactant determines the location of TiO2 nanoparticles in the corresponding block, as confirmed by transmission electron microscopy, differential scanning calorimetry and Fourier-transform infrared spectroscopy. The modes of dispersion of TiO2 in the blocks depend on the type of bonding between the surfactant and TiO2 (covalent or ionic). Photoluminescence studies of these nanocomposites demonstrate that the location of TiO2 nanoparticles affect the block copolymer’s luminescence at different wavelengths. In chapter 3, we studies, arrayed, needle-like nanostructures of rutile phase crystal TiO2 were grown on a Si substrate containing TiO2 seeds prepared through a thin polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer template. The morphology of the deposited TiO2 nanostructures was characterized by field-emission scanning electron microscopy, X-ray diffraction and transmission electron microscopy (TEM). By using TiO2 seeds prepared from their diblock copolymer PS-b-P4VP template, arrayed, needle-like rutile TiO2 nanostructures with variable spatial positions and densities were fabricated. The distance between two TiO2 needle bunches (120nm and 160 nm) could be controlled using block copolymer templates with different molecular weights. Furthermore, in chapter 4, we report that single, aligned TiO2 nanoneedles having diameters in the tens of nanometers can be grown through a solution crystal growth process from patterned nanocavities under the influence of an electric field. The electric field, which we applied perpendicular to the substrate plane, drove the precursor solution into the cavities by overcoming the surface tension encountered and oriented the TiO2 nanoneedles during the growth process. The effect of initial pH value of the precursor solution and urea concentration were studied and discussed. We believe that this new class of aligned TiO2 nanostructures will find a wide range of future applications.