Abstract We have studied the effect of grain size on the photocatalytic activity of TiO2 thin films grown by atomic layer deposition technique. A number of thin films of different crystallinity (anatase, rutile, amorphous) and grain sizes (55 nm to 715 nm) were grown on Si substrates under different processing conditions, by varying the reactor temperature, deposition time or buffer layers. The films are characterized by scanning electron microscopy, grazing incidence x-ray diffraction, x-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy. The photocatalytic activity was examined by measuring the degradation rates of methylene blue in aqueous solutions under the ultraviolet light irradiation. The photocatalytic activity exhibits a maximum for grains of average size of 200 nm, indicating existence of two competing effects, which occur when the average grain size decreases: increase of active surface area (which promotes a high photocatalytic activity) and increase of grain boundaries (which degrades the photocatalytic activity).

中文翻译：

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晶粒尺寸对原子层沉积法生长的 TiO2 薄膜光催化活性的影响

摘要 我们研究了晶粒尺寸对通过原子层沉积技术生长的 TiO2 薄膜的光催化活性的影响。在不同的处理条件下，通过改变反应器温度、沉积时间或缓冲层，在硅衬底上生长了许多不同结晶度（锐钛矿、金红石、无定形）和晶粒尺寸（55 nm 至 715 nm）的薄膜。通过扫描电子显微镜、掠入射X射线衍射、X射线光电子能谱、二次离子质谱和原子力显微镜对薄膜进行表征。通过测量紫外光照射下亚甲基蓝在水溶液中的降解率来检测光催化活性。对于平均尺寸为 200 nm 的晶粒，光催化活性表现出最大值，