钒掺杂纳米TiO_2薄膜的结构和光吸收性能

Microstructure and Photo-absorption Property of V-doped Nano-TiO_2 Thin Films

采用磁控溅射法制备了不同V含量的纳米TiO2薄膜,利用SEM、XRD、Ram an光谱和UV-vis吸收光谱对V掺杂TiO2薄膜的表面形貌、结晶特性、晶格应力和光吸收性能进行了分析.结果表明,V掺杂可促进TiO2薄膜晶粒的定向生长,得到尺寸分布较均匀的哑铃状晶粒,且可抑制薄膜的晶格膨胀和金红石型晶粒的生成.V掺杂TiO2薄膜处于压应力状态,且应力随V含量增加而增大.V掺杂使导带底向带隙延伸,TiO2薄膜光学带隙变窄,光响应范围从紫外区红移到可见光区域,提高了薄膜对可见光的吸收率.

V-doped nano-TiO2 thin films with different V-dopings were prepared by magnetron sputtering method. The microstructure observation and crystallization mechanism of the films were performed by scanning electron microscope（SEM） and X-ray diffractometer （XRD）. Raman spectrum and UV-vis transmittance spectrum of the films were also accomplished by Raman spectrometer and ultraviolet-visible spectrometer. The stress in crystal lattice and photo-absorption property of the films were studied. The results indicate that vanadium dopant in nano-TiO2 thin films can induce the oriented crystallization of TiO2 and form sizable dumbbell-state crystal grains. The addition of vanadium to TiO2 thin films suppresses the expanding of crystal lattice and the generation of rutile. The stress in the V-doped nano-TiO2 films increases with the increase of vanadium content. With the addition of vanadium, the energy level of conduction band of the nano-TiO2 lowers and stretches to bandgap. Thus the bandgap of nano-TiO2 is narrowed down. As a result, the optical absorption edge of the V-doped nano-TiO2 thin films shifts from ultraviolet zone to visible one, enhancing the absorptivity of the films on visible light.