Research on the Photocatalytic Activity of Oxide Semiconductor Films under Visible Light Illumination

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 18560313
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Electronic materials/Electric materials
• Research Institution: Shibaura Institute of Technology
• Principal Investigator: TAKAO Nagatomo Shibaura Institute of Technology, Faculty of Engineering, Professor (70052868)
• Project Period (FY): 2006 – 2007
• Keywords: photocatalysis / oxide semiconductor films / visible light response / RF sputtering / strontium titanate / perovskite structure / transition metal oxide Semiconductors / indirect transition

Research Abstract

Titanium dioxide (TiO_2) is a well-known, efficient photocatalysts. Strontium titanate (SrTiO_3)is also one of interest photocatalysts. In present work, we studied the photocatalytic activity of SrTiO_3 films in visible light region. Strontium titanate films were grown on pyrex glass and fused quartz glass by a RF magnetron sputtering. The crystalline structure of SrTiO_3 films was investigated by using X-ray diffraction. Three peaks of (100) ,(110) and (200) faces for the SrTiO_3 films on the glass substrates were observed. SrTiO_3 films are polycrystalline with perovskite structure. The absorption coefficients(α) of SrTiO_3 films were calculated from the absorbance data as a function of photon energy. The optical band gap of SrTiO_3 films was estimated according to Tauc relation [αE(hυ)]^<1/2>-E(hυ)(E(hυ): photon energy). The indirect band gap can be evaluated by extrapolating the linear portions of the plots. The indirect optical band gap of undoped SrTiO_3 films is measured to be 3.2-3.3 eV, which is in good agreement with the reported value. RF-sputtered SrTiO_3 films did not decompose methylene blue dye under UV illumination. It is one of the reasons that it is difficult to control the composition ratio than that of TiO_2 as SrTiO_3 has, the perovskite structure. Although the optimization of the film preparation conditions for activating the photocatalytic reaction was insufficient, we couldn't achieve the initial purpose. The titanium oxide (TiO_2) films fabricated by RF sputtering showed strong photocatalytic reaction under UV illumination. It is reported that TiO_2 films prepared by RF sputtering have photocatalytic activity under the visible light without doping of cation and anion by controlling the substrate temperature precisely.