Role of the defect in determining the properties of PbTi_(0.9)Ni_(0.1)O_3 thin films

摘要

PbTiO_3 with oxygen-vacancy-stabilized d~8 ion substitution has attracted significant attention as a promising photo-ferroelectric material, but less effort to understand the effect of defect structures on its macroscopic properties limits further modification of the functionality via defect engineering. Herein, a comparable investigation of highly-(111) oriented PbTiO_3 (PTO) and PbTi_(0.9)Ni_(0.1)O_3 (PTN) thin films is reported to realize the critical role of defect structures on the evolution of electrical and photovoltaic properties. It is found that the PTO thin film shows the space-charge-limited-current mechanism, while the PTN thin film obeys the Poole-Frenkel emission mechanism. Also, the dielectric abnormal peak emerges in the PTN thin film. Notably, the ferroelectric polarization still keeps a large value but the band gap is lowered, and thus a significant increment of photovoltaic properties is achieved in the PTN thin film. These experimental results can be well explained if the formation of dopant-vacancy complexes is taken into account.