3:45 PM - 4:00 PM
[13p-2V-4] Study on electron injection dynamics in Au-TiO2 nanoparticle system (2) –indication of electron transfer by PEEM image of fs-laser excited pair-
Keywords:electron injection dynamics,PEEM,Au-TiO2 nanoparticle system
We are studying electron injection dynamics in Au-TiO2 nano-particle (NP) system for realizing high efficiency solar cell utilizing nanoplasmonic. Electron emission from NPs irradiated by femtosecond laser pulse are observed with a photoemission electron microscope (PEEM) having a spatial resolution of 30-nm. We obtained PEEM images indicating electron transfer from Au-NP to TiO2-NP.
TiO2 particles of 100-nm nominal size were mixed in a liquid of Au particles of 10-nm nominal size dispersed by surfactant. A drop was dripped in one quarter region on a Si wafer of 10 mm size, and the sample was baked at 500degC to form Au-NP attached TiO2-NP. This region is called mixed region. The sample had also Au and TiO2 regions.
PEEM images were observed by Hg lamp illumination as well as fs-laser irradiation. In Au and TiO2 regions, all bright spots were found at the same positions in both illuminations. On the other hand, in the mixed region, some spots seen in the Hg lamp illuminated PEEM image were not found in the fs-laser illuminated image. This indicates that electrons emitted from Au-TiO2 –NP pair are generated by the transfer of electrons from Au NP to TiO2 NP.
The PEEM images of particles illuminated by fs-laser were weaker for Au-NP than TiO2, which can be attributed to shorter lifetime of fast electrons in Au-NP. PEEM mage of Au-TiO2 –pair was brighter than TiO2 –NP, which indicates electron transfer into TiO2-NP from Au-NP which is more efficient absorber of 790-nm wavelength fs-laser than TiO2-NP.
TiO2 particles of 100-nm nominal size were mixed in a liquid of Au particles of 10-nm nominal size dispersed by surfactant. A drop was dripped in one quarter region on a Si wafer of 10 mm size, and the sample was baked at 500degC to form Au-NP attached TiO2-NP. This region is called mixed region. The sample had also Au and TiO2 regions.
PEEM images were observed by Hg lamp illumination as well as fs-laser irradiation. In Au and TiO2 regions, all bright spots were found at the same positions in both illuminations. On the other hand, in the mixed region, some spots seen in the Hg lamp illuminated PEEM image were not found in the fs-laser illuminated image. This indicates that electrons emitted from Au-TiO2 –NP pair are generated by the transfer of electrons from Au NP to TiO2 NP.
The PEEM images of particles illuminated by fs-laser were weaker for Au-NP than TiO2, which can be attributed to shorter lifetime of fast electrons in Au-NP. PEEM mage of Au-TiO2 –pair was brighter than TiO2 –NP, which indicates electron transfer into TiO2-NP from Au-NP which is more efficient absorber of 790-nm wavelength fs-laser than TiO2-NP.