Direct probing of surface polarization in organic molecular films by Maxwell-displacement-current and electric field induced optical second harmonic generation

COLL 451

Mitsumasa Iwamoto, iwamoto.m.ac@m.titech.ac.jp, Takaaki Manaka, manaka.t.aa@m.titech.ac.jp, Eunju Lim, lim.e.aa@m.titech.ac.jp, and Ryousuke Tamura, rtamura@ome.pe.titech.ac.jp. Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo, 152-8552, Japan
The probing of dynamical behavior of dipoles and electrons in organic materials is interesting. We report a novel electrical measurement that can directly probe orientational dipolar motion in monolayers by Maxwell-Displacement-Current (MDC), and also report a novel optical technique that allows electronic charge distribution in organic materials to be probed by measuring the optical second harmonic signals induced by the electric field (EFISHG) formed in organic films. Using FET structures, electric fields formed in pentacene are selectively determined at the off- and on states, and carrier injection, accumulation, transport, and trapping are discussed. Finally, we report an advanced time-resolved microscopic optical SHG (TRM-SHG) that can visualize the real carrier motion in organic films. The intrinsic carrier mobility is determined from the visualized carrier motion. We conclude that the developed EFISHG method coupled with MDC can illustrate the carrier motion in organic materials including biomaterials, polymers, etc.