Evidence of ferroelectric behaviour in CaCu3Ti4O12 thin films deposited by RF-sputtering

Abstract

The origin of abnormal ferroelectric and unusual piezoelectricity in the polycrystalline CaCu 3 Ti 4 O 12 (CCTO) thin films deposited by RF-sputtering on Pt/Ti/SiO 2 /Si (100) substrates was explored. The CCTO thin films, deposited at room temperature followed by annealing at 600°C for 2 h in a conventional furnace, have a cubic structure with lattice parameter a = 7.379 ± 0.001 Å and without any secondary phases. No polarization loss up to 10 10 switching cycles, with a switched polarization ∆P of 30 µC/cm 2 measured at 400 kV/cm was evidenced. The piezoelectric coefficient investigated by piezoresponse force microscopy (PFM) was approximately 9.0 pm/V. This may be the very first example of exploring the origin of ferroelectric behaviour for a material that possesses space charge polarization with highly resistive grain boundaries in the polycrystalline state.

High-performance piezoelectric energy harvesting in amorphous perovskite thin films deposited directly on a plastic substrate

“…Piezoelectricity in this amorphous state is believed to come mainly from the dipolar polarization of TiO 6 octahedra distributed randomly in a network of dipole units. The evidence of dipolar polarization (or ferroelectricity) has been reported in polycrystalline CCTO thin films processed by various deposition techniques [30][31][32][47][48][49] .…”

“…3h and reported previously 32 . The two arcs in the amorphous state create two intercepts on the Z' axis (x-axis); the first and second intercepts indicate the grain boundary resistance and the resistance at the interface between the film and electrode, respectively 32,49 . A higher pO 2 decreased the interfacial resistance, which was related to the changed chemical states with fewer oxygen vacancies.…”