**2.2 Characterization of Cu/TiO2 film**

The structure and crystallization characteristics of Cu/TiO2 film were evaluated by SEM (JXS-8530F, JEOL Ltd.), EPMA (JXA-8530F, JEOL Ltd.), TEM (JEM-2100/ HK, JEOL Ltd.), EDX (JEM-2100F/HK, JEOL Ltd.), and EELS (JEM-ARM2007 Cold, JEOL Ltd.). Since these measurement instruments use electron for analysis, the sample should be an electron conductor. Since netlike glass disc was not an electron for analysis, the carbon vapor deposition was conducted by the dedicated device (JEE-420, JEOL Ltd.) for Cu/TiO2 coated on netlike glass disc before analysis. The thickness of carbon deposited on sample was approximately 20–30 nm.
