PC 24

CARRIER INJECTION AND TRAPPING IN POLYDIACETYLENE FILMS STUDIED BY OPTICAL SECOND HARMONIC GENERATION

T. Manaka, H. Kohn, Y. Ohshima, E. Lim, M. Iwamoto

Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552, Japan (manaka.t.aa@m.titech.ac.jp)

For the application of organic materials in electronic devices, carrier injection and trapping process is an important issue to discuss the device operation. Recently, we proposed a novel technique to evaluate the electric field distribution along the organic FET channel by electric field induced second harmonic generation (EFISHG) measurement [1]. Owing to the low free carrier density of organic materials, injected carriers work as excess charges that form a Poisson electric field. These motivated us to employ the SHG technique for studying the carrier motion and charge storage in polymers. In this presentation, carrier injection and trapping in polydiacetylene (PDA) film are discussed based on the SHG response.

EFISHG signals were not enhanced though the external voltage was applied to the PDA during carrier injection (see region 2 of Fig.1). On the other hand, the signals were observed after turning off the applied voltage (region 3) due to the space charge field formed by trapped carriers. Using the SHG response, the detrapping process was precisely studied, and the activation energy was was evaluated. Furthermore, time resolved SHG measurement is shown to be a powerful method for studying the dynamical injection process.

 

 

[1] T. Manaka, et al., Appl. Phys. Lett., 89 (2006) 072113.