Studies On The Photoelectric Properties And Carrier Dynamics In Perovskite Oxide Low-dimensional Structures

Due to strong couplings between charge,spin,orbit,and lattice in perovskite-type materials,a variety of energetically competing electronic phases with different electric and magnetic properties coexist,leading to rich exotic effects such as ferroelectric,piezoelectric,dielectric,pyroelectric and photovoltaic effect,high-temperature superconductivity,colossal magnetoresistance,metal-insulator transition and optical nonlinearity.Especially,by being combination with the traditional semiconductor process,perovskite oxide low-dimensional structures can miniaturize and integrat the functional devices,which attract more and more attentions.Researches on perovskite oxide functional and electrical properties are significant not only for understanding the physical mechanisms of strongly correlated systems and but also for expanding their applications.In this thesis,the photoelectric properties of perovskite oxide low-dimensional structures are studied.The photoelectric effect is deeply analyzed in perovskite oxide low-dimensional structures.A new explanation for the mechanism of the impact zone is offered in photoelectric effect.The impact of partial irradiation is studied on the whole perovskite oxide.The photo-induced carrier dynamics is explored in it.For the unique electronic structures of perovskite oxide low-dimensional structures,the impact of temperature and magnetic field on the photoelectric effect is studied in perovskite oxide low-dimensional structures.The enhancement of quantum efficiency of photoelectric effect by the interface effect is first found in perovskite oxide low-dimensional structures.This discovery can greatly expand the application of perovskite oxides.The main results are listed as following:（1）The impact of partial irradiation on the state of conductivity and the distribution of photo-induced carriers is studied in the SrTiO₃ single crystal.The photoelectric effect in SrTiO₃ single crystal is found to be an entire effect.No matter how large the irradiation area of the SrTiO₃ single crystal is,it takes part in the photoelectric effect as a whole.The photo-induced carriers move freely in SrTiO₃ single crystal like in a conductor.The photovoltages and photocurrents can be measured in tilting SrTiO₃ single crystal.The photovoltge of irradiation area depends on the laser energy density,the number of lattice steps and the tilted angle of SrTiO₃ single crystal.The photovoltge of non-irradiation area depends on the photovoltge of irradiation area and the distance of carrier propagation in non-irradiation area.The ground point plays a determining role in potential distribution in SrTiO₃ single crystal.（2）The La_2/3Ca_1/3MnO_3-δfilm is prepared by pulsed laser deposition.The photo-induced resistance effect is studied in La_2/3Ca_1/3MnO_3-δfilm irradiated by different wavelengths laser.Because of the oxygen vacancy,A high change of photo-induced resistance is found in La_2/3Ca_1/3MnO_3-δfilm.The photoelectric response of La_2/3Ca_1/3MnO_3-δfilm irradiated by 808 nm laser is higher than 505 nm laser at room temperature.The laser energy and bias current are important factors that impact the photo-induced resistance.The change of photo-induced resistance in La_2/3Ca_1/3MnO_3-δfilm is stable when the laser energy is constant.The change of photo-induced resistance in La_2/3Ca_1/3MnO_3-δfilm increases with the decreasing temperature.（3）The photo-induced magnetoresistance and magnetic-field modulated photoelectric response are studied in the multiferroic perovskite oxide BiFeO₃/Si heterojunction.There is ferroelectric photovoltaic effect in the BiFeO₃/Si heterojunction.Different wavelengths laser have different effects on photo-induced magnetoresistance in the BiFeO₃/Si heterojunction.The effect of 1064 nm laser is stronger than the effect of 532 nm laser.The transient photovoltaic effect in BiFeO₃/Si heterojunction can be modulated by the magnetic-field.The transient photovoltaic in BiFeO₃/Si heterojunction first increase and then decrease with the increasing magnetic-field.The magnetic-field has a distinctive modulation effect on open-circuit photovoltage and short-circuit photocurrent.The photovoltage and photocurrent can be easier saturated when the BiFeO₃/Si heterojunction irradiated by 1064 nm laser.（4）Different periods（LaAlO₃/SrTiO₃）_n superlattices on SrTiO₃ single crystal substrates are prepared by pulsed laser deposition.The enhancement of quantum efficiency of photoelectric effect by the LaAlO₃/SrTiO₃ interface effect is studied in（LaAlO₃/SrTiO₃）_n superlattices.The photoelectric effect in（LaAlO₃/SrTiO₃）_n superlattices is found to be an entire effect.No matter how large the irradiation area of the（LaAlO₃/SrTiO₃）_n superlattices is,it take part in the photoelectric effect as a whole.Because of the impact of interface effect,the quantum efficiency of photoelectric effect is much higher than the laser irradiating the surface area.The bias voltage can modulate the quantum efficiency of photoelectric effect when the laser irradiating the interface area.The bias voltage can improve the interface effect of the quantum efficiency of photoelectric effect.