Fabricating TiO₂ Thin Film On Silicon Substrate With Micro-nanoscale Structures

Photocatalysis Technology has a wide application prospect as an efficient, clean technology in dealing with environmental pollution issues. Among the semiconductors, TiO2 is the most common photocatalyst due to the advantage of chemical durability, non-toxic, low cost. Since its higher photocatalytic activity with larger surface area, TiO2 powder has been widely applied. However, the application of TiO2 powder is limited, because it is easy to be poisoned and hard to recycle in slurry phase. The TiO2 film supported by a carrier (such as glass, metal, ceramics and other materials) is made to facilitate their recycling. Currently, the surface area of TiO2 film is the main reason for limiting the development of this technology. Therefore, enlarging surface area of TiO2 film and optimizing supported carrier to improve the performance of photocatalyst is a direction for further development.To solve the problem of the poor performance of photocatalysis of TiO2 film with lower surface area, we proposed silicon substrate as a carrier to obtain a surface having a micro-nano composite structure by anisotropic etching. And then, a thin TiO2 film has been grown on this substrate by controlling hydrothermal reaction time and calcination temperature, which could regulate the surface morphology of TiO2 film and increase their catalytic efficiency. The properties of the samples are characterized by SEM, XRD, UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of TiO2 films has been applied on degrading methyl orange and methylene blue.This paper mainly focuses on the following three parts:(1) We have developed a simple, low cost method to fabricate silicon substrate with micro-nanoscale structure. The structure exhibits anti-reflective properties characterized by UV-vis diffuse reflectance spectrum, the reflectivity of the Si wafer was reduced from above 35% to below 5%. From the characterization of SEM, we can see that the micro-nanoscale structure has higher surface area, which enlarges the carrying amount of TiO2 thin films and increases the surface area of TiO2 film. Thus it could improve the performance of photocatalysis.(2) In this paper, TiO2 film is prepared by using chemical growth method on the surface of silicon. Since â–³G of the reaction between TiCl4 and Si-H is below 0, which indicates that the reaction can be spontaneous at room temperature. The primary steps for synthesizing TiO2 are similar to sol-gel method. Then, the films are reacted with the mixing solution composed of tetrabutyltitanate, acetic acid and deionized water by hydrothermal reaction. By controlling of the preparation time and calcination temperature, we can adjust surface morphology of TiO2 film. We characterize their property by SEM and XRD.(3) The photocatalytic efficiency of the above films has been applied on degradation of methyl orange and methylene blue. We test the photocatalytic performance:substrates with large area and stronger light absorption has better photocatalytic performance; Stirring can enhance the reaction of photocatalysis process through kinetic analysis, but the photocatalysis performance will be constant...