Shenggui Zhao

Positive colossal magnetoresistance effect in ZnO∕La0.7Sr0.3MnO3 heterostructure

In this letter, an oxide heterostructure has been fabricated by successively growing La0.7Sr0.3MnO3 and ZnO layers on a LaAlO3 (100) substrate using pulsed laser deposition. The ZnO∕La0.7Sr0.3MnO3 heterostructure exhibits good rectifying behavior and a positive colossal magnetoresistance (MR) effect over a temperature range of 77–280K. The maximum MR values are determined to be about 53.9% at H=0.5T and 36.4% at H=0.3T. A possible explanation is given in terms of the effect of magnetic fields on the depletion layer and the capture carriers effect at the interface.

Ultraviolet photovoltage characteristics in ZnO/La0.7Sr0.3MnO3 heterostructure

Ultraviolet photovoltage characteristics have been observed in a ZnO/La0.7Sr0.3MnO3 heterostructure, which exhibits reproducible rectifying characteristics. The peak photovoltage is about 0.704 V and the rise time is about 10 ns for the photovoltaic pulse at T = 78 K when the heterostructure is irradiated by a 248 nm laser pulse of 25 ns duration. The peak photovoltages and the full widths at half-maximum decrease with increasing temperature. These might be attributed to the change in the fractions of the ferromagnetic insulating phases in the depletion layer.

Photoinduced effect on carrier transport properties in La0.7Sr0.3MnO3/Si heterostructure

The photoinduced effect on carrier transport properties has been investigated in the La0.7Sr0.3MnO3/Si heterostructure prepared by the pulsed laser deposition method. A giant photoinduced relative change in the resistance of about 6783% in the current-perpendicular-to-plane (CPP) geometry of the heterostructure has been observed when it is irradiated by a 532 nm laser at T = 270 K. The rising time of about 100 µs in the CPP geometry of the heterostructure under modulated laser irradiation of 200 µs duration seems to be independent of temperature. This provides an innovation for potential application in functional optical and electrical devices.

Voltage-modulated negative and positive magnetoresistance in La0.7Sr0.3MnO3/Si heterostructure

Magnetotransport properties have been investigated in a La0.7Sr0.3MnO3/Si heterostructure, which exhibits good rectifying behaviour and voltage-modulated negative and positive magnetoresistance effects. The application of magnetic fields induces an increase in the current at a low bias voltage and a decrease at a high bias. This is caused by the effect of the voltage on the ferromagnetic state in the La0.7Sr0.3MnO3 film at the interface by the field-direction-dependent lattice distortion at a high bias voltage.

Transport and photoresponse properties in Pr0.5Ca0.5CoO3/Nb-SrTiO3 heterostructure

Transport and photoresponse properties of the heterostructure consisting of a Pr0.5Ca0.5CoO3 film and a Nb-SrTiO3 substrate were investigated. The Pr0.5Ca0.5CoO3 film exhibits semiconducting behavior and the resistances are decreased when irradiated by a 532 nm laser. The rectifying behaviors are observed in the heterostructure. The ideality factors and the diffusion voltages monotonically decrease with increasing the temperature. The photovoltatges of the heterostructure under the irradiation approach the saturation at about . The minority carrier lifetime of is estimated from the time response properties in the falling process of photovoltages. These results reveal that the Pr0.5Ca0.5CoO3 heterostructures have great potentials in photoresponse and photoelectric conversion applications.

Magnetroresistance and Current-voltage Chiaracteristics in La 2/3 Sr 1/3 MnO 3 /ZnO Composite Films: Magnetroresistance and Current-voltage Chiaracteristics in La 2/3 Sr 1/3 MnO 3 /ZnO Composite Films

利用脉冲激光沉积的方法在Si（100）氧化成SiO2的基片上制备了（La2/3Sr1/3MnO3）x/（ZnO）1-x混合物薄膜,研究了薄膜的磁电阻和伏安特性.X射线衍射分析表明,除了衬底SiO2的衍射峰以外,分别出现了La2/3Sr1/3MnO3（101）的衍射峰和ZnO（002）的衍射峰,且它们形成了两相共存体系.实验表明：x=0.3的混合物薄膜表现为半导体导电特性,而x=0.4的样品则出现了典型的金属-绝缘相变.所制备的样品表现出了低场磁电阻效应和非线性伏安特性.在0.7T磁场的作用下,x=0.3的样品在温度为60K时取得的最大磁电阻值为28.8%.通过对伏安关系拟合表明,在La2/3Sr1/3MnO3和ZnO颗粒之间存在一定的耗尽层,且产生了界面缺陷态.

Transport Property and Photoinduced Relaxation Effect in Sm0.5Ca0.5MnO3 Film

Abstract Charge-ordering Sm0.5Ca0.5MnO3 film has been deposited on a (100)-LaAlO3 substrate by a RF magnetron sputtering method, and the X-ray diffraction analysis shows that the film has better epitaxial character. The film exhibits the semiconductor-type conduction with the increase of the temperature. The magnetic field and laser irradiation induce the reduction in the resistance of the film, which is attributed to the delocalization effect of manganites. The photoinduced relaxation effect of the film reveals that the resistance is exponentially dependent on the time and the time constant increases with the temperature increasing due to the growing thermal fluctuation.