Manaka Takaaki

Measurement of Surface Potential at Metal/Organic-Material Interfaces by Electro-Absorption Method

The surface potential built-in vacuum deposited phthalocyanine (Pc) film on aluminium electrode is investigated by the electro-modulation method. To avoid the influence of charge injection, a sandwiched cell (Al–Pc–air–ITO) is fabricated. The modulation signal, which depends on the external electric field intensity, is detected. The properties of electro-absorption (EA) and electro-reflectance (ER) signals are analysed. The existence of the surface potential at the metal/organic-material interface induces 1f referenced ER signals. As a result, the surface potential built across the vacuum-deposited Pc film on the aluminium electrode is estimated to be 1.23 V.

Analysis of Second-Harmonic Generation from CuttbPc LB Film/Metal Interface

Second-harmonic generation signals from a CuttbPc LB film deposited on metal (Al or Au)–glass substrates were investigated. It was observed that there were two second-harmonic peaks at the wavelength of 1060 and 1250 nm in the CuttbPc/Al film, but only one peak at 1050 nm in the CuttbPc/Au film. Meanwhile the surface electric potentials (SEP) at the interfaces of LB film/metals were also measured using a Kelvin probe. The SEP in the CuttbPc/Al decreases and eventually approaches a saturated value of -1.0 V as the film thickness increases, while the SEP in the CuttbPc/Au is nearly zero. Based on the experimental results and theoretical analysis, it was considered that the space-charge-induced electric field makes a main contribution to the second-harmonic generation at 1250 nm in the CuttbPc/Al film.