• Taniguchi, Hiroki
• Terasaki, Ichiro
• Okazaki, Ryuji
• Shiraishi, Yuuka

Abstract

<jats:p>We report the electrical conductivity and the Seebeck coefficient of a SrTiO3 single crystal under 405-nm laser illumination from 10 to 30 K. We find that the photoconductivity exponentially increases with decreasing temperature, suggesting a gradual metal-insulator transition. Assuming the carrier mobility reported in the preceding studies, we have evaluated the carrier concentration to be 8×109cm−3 at maximum, which corresponds to 10−7ppm impurities in the case of chemical doping. Such ultralow doping is realized only when the energy of the incident light is slightly lower than the bandgap. In this situation, the incident light penetrates the whole sample with a small probability of electron–hole creation. We find that the observed photo-Seebeck coefficient seriously disagrees with the calculated values from the carrier concentration. In order to remedy this discrepancy, we have proposed a phenomenological model in which the quantum paraelectric behavior of SrTiO3 screens the thermoelectric voltage.</jats:p>

Topics

• impedance spectroscopy
• single crystal
• mobility
• electrical conductivity
• photoconductivity