Abstract The 100-nm titanium dioxide (TiO2) thin film and its composites with copper (Cu) underlayers of various thicknesses, 4 nm–16 nm, were fabricated on glass substrates by a DC-magnetron sputtering technique. Optical properties of the pristine and the composite films revealed that increasing Cu underlayer thickness greatly increased their absorption in the entire visible region, leading to a decrease in the band gap energy. This should significantly enhance the solar-driven catalytic activity. However, it was found that the photocatalytic activity under the UV radiation determined from photo-degradation of methyl orange (MO) of thick Cu underlayer films exhibited the reduction in degradation rate. The photoluminescence indicated that Cu nanoparticles at TiO2/Cu interface layer not only generated shallow level defects in TiO2 band gap but also acted as recombination centers for photo-generated carriers. This phenomenon was the result of the presence of Cu surface roughness as well as the presence of large aggregates in thick Cu layers. Therefore, the life time and the number of free carriers transported to the TiO2 surface decreased causing the reduction in photodegradation activity of TiO2 composite films.

中文翻译：

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二氧化钛/铜多层膜界面电荷转移和光催化活性的光致发光研究

摘要 通过直流磁控溅射技术在玻璃基板上制备了 100 nm 二氧化钛 (TiO2) 薄膜及其与各种厚度 (4 nm–16 nm) 铜 (Cu) 底层的复合材料。原始薄膜和复合薄膜的光学特性表明，增加 Cu 底层厚度大大增加了它们在整个可见光区的吸收，导致带隙能量降低。这将显着提高太阳能驱动的催化活性。然而，发现由厚铜底层膜的甲基橙（MO）的光降解确定的紫外辐射下的光催化活性表现出降解速率的降低。光致发光表明TiO2/Cu界面层的Cu纳米颗粒不仅在TiO2带隙中产生浅能级缺陷，而且作为光生载流子的复合中心。这种现象是铜表面粗糙以及厚铜层中存在大聚集体的结果。因此，传输到 TiO2 表面的自由载流子的寿命和数量减少，导致 TiO2 复合膜的光降解活性降低。