热处理对离子注入法制备的二氧化钛薄膜光学性能的影响

【作者】 居勇峰；

【导师】 祖小涛；

【作者基本信息】 电子科技大学 ， 凝聚态物理， 2008， 硕士

【摘要】 TiO₂在紫外光下具有优异的光催化性能，在废水处理、空气净化、抗菌等环保领域有着广泛的应用，但实现其可见光催化一直是研究的难点之一。本论文提出了一种利用离子注入和后续退火制备氮掺杂TiO₂薄膜的方法，以实现TiO₂的可见光催化。首先分别向石英玻璃和蓝宝石（α-Al₂O₃单晶）中注入Ti离子，随后在氮气中退火到900℃，从而制备了N掺杂TiO₂薄膜。同时，又将注入态样品在氧气中退火，对比研究了不同基体和不同退火气氛对TiO₂薄膜光学性能的影响。本文采用SRIM 2006模拟程序、卢瑟福背散射谱（RBS）、X射线光电子能谱（XPS）测试、透射电子显微分析（TEM）和紫外-可见光吸收谱（UV-Vis），分别研究了石英玻璃和蓝宝石中注入Ti离子前后的微观结构和宏观光学性能，并对比研究样品在不同气氛中退火处理后，光学性能和微观结构上的变化，主要得到以下结果：1．室温下在石英玻璃和蓝宝石中同时注入能量为80 keV、注量为1×10¹⁷cm^-2的Ti离子，离子注入过程在基体中引入大量缺陷，紫外光区吸收显著增强，但没有明显的吸收峰出现。注入态样品中Ti主要以金属Ti和TiO₂的形式存在。2．注入态样品分别在N₂和O₂气氛中从400℃到900℃等时退火。N₂中退火到500℃时，石英玻璃基体中开始出现TiO₂的吸收边，退火到600℃时蓝宝石基体也开始出现TiO₂的吸收边，当退火温度升高到900℃时，金属Ti转变成TiO₂，同时N原子替代少量的晶格O原子形成了O-Ti-N化合物。在石英玻璃基体中TiO₂的光学带隙从500℃时的3．98 eV红移到900℃时的3．30 eV，在蓝宝石基体中TiO₂的光学带隙从600℃时的3．90 eV红移到900℃时的3．45 eV，TiO₂吸收边末端延伸到可见光区，在可见光区的吸收强度明显增加；同样，在O₂中退火时，在石英玻璃基体中TiO₂的光学带隙从500℃时的3．97 eV红移到900℃时的3．60eV，在蓝宝石基体中TiO₂的光学带隙从500℃时的3．98 eV红移到900℃时的3．60eV，随退火温度的升高，吸收边红移，但没有在氮气中明显。3．对比分析在不同基体表面形成的TiO₂薄膜的光学性能发现，不同基体对TiO₂薄膜的光学性能影响不大，然而，不同的退火气氛对TiO₂薄膜光学性能影响较大，在O₂气氛下退火由于没有N元素的掺入，光学带隙的变化并不明显；在N₂气氛下退火由于N原子替代少量的晶格O原子形成了O-Ti-N化合物，使TiO₂薄膜的光学带隙明显降低，TiO₂吸收边末端延伸到可见光区，这说明氮的引入，可使TiO₂具有可见光活性。更多还原

【Abstract】 TiO₂ has application in the filed of environmental science, e.g., wastewater treatment, air purification and antibacterial aspect, due to its excellent photocatalytic performance in UV light. In this paper, ion implantation and subsequent annealing in N₂ have been used to prepare TiO₂ films in order to obtain TiO₂ with catalysis in visible light. Ti ion-implantated fused silica andα-Al₂O₃ single crystals have been annealed in N₂ ambience. In this way, N-doped TiO₂ films are successfully prepared.In this work, optical absorption spectroscopy, Rutherford backscattering spectrometry （RBS） , transmission electron microscopy （TEM） , X-ray photoelectron spectroscopy （ XPS ） and SRIM 2006 calculation code have been utilized to characterize the optical and structural properties of samples. The results are listed as follows:1. 80 keV Ti ion implantation was performed at room temperature up at a fluence of 1×10¹⁷ cm^-2 in both fused silica andα-Al₂O₃ single crystals （sapphire） . The implantation of Ti ions has introduced many defects in substrates. Therefore, the absorption of UV waveband increased, however, there is no clear absorption peak appeared. According to XPS results, metallic Ti⁰ and TiO₂ film coexisted in the as-implanted samples.2. The as-implanted samples have been annealed in N₂ and O₂ ambience, respectively. The optical absorption edge of TiO₂ appeared in fused silica matrix at 500℃and in sapphire at 600℃, respectively, after annealing in N₂ ambience. After annealing at 900 C in N₂ ambience, a red shift of the optical absorption edge of TiO₂ was observed from 3.98 eV （500℃） to 3.30 eV （900℃） in fused silica while 3.90 eV（600℃） to 3.45 eV （900℃） in sapphire, due to the formation of O-Ti-N compound. The tail of the absorption edge extends to the visible waveband and the absorption intensity of TiO₂ increases in the visible waveband. After annealing in O₂ ambience at 500℃, the optical absorption edge of TiO₂ in both fused silica and sapphire appeared. But the red shift is not so clear as that in N₂ ambient with the increasing temperature.3. The results show that the optical properties of TiO₂ film in fused silica and α-Al₂O₃ single crystals are similar. However, the annealing ambience plays a very important role in the optical properties of TiO₂ film. For the samples annealed in the N₂ ambience at 900℃, a new compound of O-Ti-N formed because a small amount of O atoms are substituted by N atoms in the lattice of TiO₂. The formation of O-Ti- N makes the tail of the absorption edge extend to the visible waveband and the absorption intensity of TiO₂ increase in the visible waveband. This result shows that nitrogen-doped TiO₂ has catalysis in the visible light.更多还原