TSC study of phase transition of vanadyl phthalocyanine thin film produced on glass by molecular beam epitaxy technique

Vanadyl phthalocyanine (VOPc) films were produced on glass substrates by the MBE technique. Films produced at a substrate temperature of room temperature have a phase I, which displays absorption peaks at 680 nm and 740 nm in UV-visible spectroscopy. The red-shifted phase introduced by heating at 100°C for one hour is called phase II. We investigated the phase transition process from phase I to phase II with the TSC method. The TSCs of VOPc/glass measured under a poling temperature of 100°C and poling voltage of 600 V have three peaks. Two peaks are related to the glass substrates. The remaining peak near -30°C is related to the VOPc film. A polarization of the film is suggested to occur in the phase I to II transition region. The force between molecules is a Van der Waals force so that the depolarization in the phase transition is suggested to be below room temperature. Therefore, the peak is concluded to be due to the phase transition process of VOPc thin film