Figure 1.

(a) Scheme of a tandem-structured TiO₂/Au/Si diode where the TiO₂ layer is stacked as the second semiconductor on a thin gold film to form double Schottky barriers. (b) A cross-sectional image of the TiO₂-deposited Au film on silicon, showing an approximately 50 nm thick layer of TiO₂ and a 10 nm thick layer of Au on the silicon. The Au layer plays a role as a common electrode to the two semiconductors and as an optical absorption layer for internal photoemission. (c) The energy band diagram for internal photoemission enhanced by the double Schottky barriers and band-to-band excitation on the two semiconductors. The red line represents internal photoemission and generation of hot electrons on the metal and the blue line represents separation of the electron/hole pairs on two semiconductors by band-to-band excitation.