[17a-G202-1~8] 12.5 Organic solar cells

[17a-G202-8] Observation of plural photon numbers in multiphoton ionization of TiO₂ nanoparticles

Bochao Li¹, Hao Li¹, Boyu Ji¹, Jinquan Lin¹, 〇Toshihisa Tomie^1,2 (1.CUST, 2.AIST)

Keywords:TiO2, plural photon numbers in multiphoton ioization, Ti 3d defect states

Multiphoton ionization by fs laser gives information on ionization energy of states where electrons are supplied. In the observation of TiO2 nanoparticles with photoemission electron microscope, PEEM, we observed a jump of slope of non-linear increase of brightness with increasing laser power. From the waveength of the jump, we cocluded binding energy of electron sourc state is 6.2 eV. This is attributed to Ti 3d defect state 0.8 eV below Fermi level. wenoticed that brightness was enhance at high laser power, and the slope showed 10-photon, which cannot be explained by ionizayion from valence band. presently we have no explanation of such asteeo slope.