Isothermal capacitance transient spectroscopy of grain-boundary interfacial states in Bi-doped SrTiO3 ceramics

It is shown that an isothermal capacitance transient spectroscopy (ICTS) technique is applicable to evaluate the interfacial state of SrTiO3 ceramics. ICTS signals were observed for Bi-doped and undoped SrTiO3 ceramics, and ascribed to interfacial states of grain boundaries. The interfacial states were located at Ei=0.7 eV below the conduction band for the Bi-doped samples and at Ei=0.5 eV for the undoped sample. This result indicates that the dopant bismuth caused deeper interfacial states in energy. The semiquantitative simulation of the ICTS signals suggests that the interfacial density of states of the SrTiO3-Bi2O3 system is more broad compared with other electronic ceramics such as ZnO-Bi2O3 and SiC-BeO systems.