Chongqing Key Laboratory of Nano Micro Composite Materials and Devices

Chongqing, China

Chongqing Key Laboratory of Nano Micro Composite Materials and Devices

Chongqing, China

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Qiang Z.,Chongqing University of Science and Technology | Gao R.,Chongqing University of Science and Technology | Gao R.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Zou J.,Chongqing University of Science and Technology | Zhang X.,Chongqing University of Science and Technology
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2016

The latest progress in the field of photo-induced current of ferroelectric coatings and devices was tentatively reviewed.The discussions focused on:i) its increasingly wide applications in optoelectronics,energyconversion and information storage; ii) the influence of the bulk properties of ferroelectric thin films,including but not limited to the band gap,polarization,barrier height at interface,microstructures of domain,grain size,depolarization field,oxygen vacancies,absorption coefficient,conductivity,and carrier lifetime,on the photo-electric conversion efficiency; iii) the existing technical problems,limiting the separation rate and collection efficiency of the carriers of the ferroelectric coatings,and their engineering solutions via innovative design of novel photovoltaic devices; iv) the controversial mechanisms responsible for the generation of photo-induced current.In addition,the development trends of the ferroelectric photovoltaic devices were also briefly discussed in a though provoking way. © 2016, Science Press. All right reserved.


Gao R.,Chongqing University of Science and Technology | Gao R.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 8 more authors.
Journal of Electronic Materials | Year: 2017

BiFeO3 (BFO) thin films with different layers were deposited on Pt/Ti/SiO2/Si substrates via the sol–gel method, and the effect of nonuniform electric field formed by asymmetry electrodes on the photovoltaic properties has been investigated through experimental approaches. The Au/BFO/Pt heterostructures show 1.3 V open-circuit voltages and ∼0.242% photovoltaic power conversion efficiency when illuminated under sunlight (AM 1.5), this high efficiency is at least one order of magnitude larger than many other values thus far reported for BFO-based devices prepared by the spin coated method. The film layer dependence of the photovoltaic effect suggests that the large open-circuit voltage and high efficiency are contributed by both the ferroelectric polarization and the asymmetric structures formed by top and bottom electrodes. Theoretical analysis indicates that the efficiency may be further significantly improved by increasing the number of film layers and the nonuniform depolarization field, implying potential applications. © 2017 The Minerals, Metals & Materials Society


Gao R.,Chongqing University of Science and Technology | Gao R.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 9 more authors.
Japanese Journal of Applied Physics | Year: 2016

A 2.5-nm-thick platinum film with the shape of a Hall bar was deposited by magnetron sputtering on weak ferromagnetic rhombohedral and tetragonal Bi0.9La0.1FeO3 thin films. An anomalous Hall effect (AHE) was observed and studied as a function of magnetic field (H) and temperature (T). For the two samples, besides the obvious difference in the anomalous Hall resistance, the anomalous Hall resistance increases sharply with decreasing temperature, and even changes sign, thus violating the conventional expression. This observation indicates strong proximity effects and local-field-induced magnetic ordering in Pt on weak ferromagnetic thin films of rhombohedral and tetragonal Bi0.9La0.1FeO3 and their contribution to the spin-related measurements should not be neglected. © 2016 The Japan Society of Applied Physics.


Luo X.D.,Chongqing University of Science and Technology | Luo X.D.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Gao R.L.,Chongqing University of Science and Technology | Gao R.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 10 more authors.
Physica B: Condensed Matter | Year: 2016

Effects of oxygen vacancies on the electrical transport properties of oxygen stoichiometric La0.8Sr0.2MnO3 and oxygen-deficient La0.8Sr0.2MnO3-δ films have been investigated. The result presents that the oxygen-deficient films annealed in vacuum show obvious increase of resistance and lattice parameter. With the sweeping voltage or temperature increasing, the resistance exhibits obvious bipolar switching effect, no forming process was needed. Oxygen deficiency in the annealed film leads to the formation of a structural disorder in the Mn-O-Mn conduction channel due to the accumulation of oxygen vacancies under high external electric field or temperatures and hence is believed to be responsible for the bipolar resistance switching effect and the enhanced resistivity compared with oxygen stoichiometric La0.8Sr0.2MnO3 film. These results may be important for practical applications in photoelectric or storage devices and point to a useful direction for other oxidizing materials. © 2015 Elsevier B.V. All rights reserved.


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

Barium zirconate titanate ceramics were fabricated by microwave sintering. Effects of microwave sintering time on microstructure, dielectric and ferroelectric properties of barium zirconate titanate ceramics have been investigated. The result shows that the ceramic samples sintered at 2.5 kW for 15–30 min are single phase perovskite structure and there is no secondary phase observed. As the microwave sintering time extends, barium zirconate titanate ceramics become more uniform and the grain size increases. The data of dielectric properties indicate that the samples prepared by microwave sintering for 15–30 min are the ferroelectrics with diffuse phase transition and the diffuseness of phase transition weakens with the extending of microwave sintering time. As microwave sintering time increases, the remnant polarization increases initially and then decreases. Moreover, the remnant polarization and the coercive field of the samples sintered for 15 and 20 min decrease as measuring frequency increases, but the measuring frequency has little effect on ferroelectricity of the sample sintered for 30 min. The temperature dependences of hysteresis loops further prove that the samples are ferroelectrics with diffuse phase transition. © 2014, Springer Science+Business Media New York.


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Journal of Alloys and Compounds | Year: 2014

Ti-doped bismuth ferrite thin films were prepared via sol-gel spin-coating method. The effects of titanium on the microstructure, optical, leakage, ferroelectric and photovoltaic characteristics have been investigated systematically. The result shows that bismuth ferrite thin films doped with 0-8 at.% Ti are rhombohedral distortion perovskite structure. The addition of titanium inhibits the grain growth and enhances the thickness uniformity and can decrease the band gap of bismuth ferrite thin films. The leakage current of bismuth ferrite thin films is effectively reduced by adding a certain amount of titanium and the leakage mechanism has been investigated. Addition of titanium increases the remnant polarization of the films. As titanium content increases, the short circuit photocurrent density decrease first and then increase, while the open circuit photovoltage increase first and then decrease. The power conversion efficiency of Ti-doped bismuth ferrite thin films increases as titanium content increases, which can be explained as a result of the increased remnant polarization and decreased band gap. © 2014 Elsevier B.V. All rights reserved.


Cao X.L.,Chongqing University of Science and Technology | Cao X.L.,Chongqing University | Cao X.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Cai W.,Chongqing University of Science and Technology | And 8 more authors.
Journal of Electronic Materials | Year: 2016

This is the first systematic report on the preparation and thermoelectric properties of n-type Pb1–xFexTe alloys. Iodine-doped n-type Pb0.85Fe0.15Te polycrystalline was prepared by melting and hot-pressing techniques. The morphology and phase structure of the prepared materials were analyzed by scanning electron microscopy and x-ray diffraction, which indicated that the samples possessed a rock-salt crystal structure and showed a biphase structure. The major phase was the polycrystalline PbTe compound and the second phase was the FeTe compound. The FeTe nano-/micro-precipitates were homogeneously distributed in the PbTe matrix, which is beneficial for the reduction of the lattice thermal conductivity. The effects of the iodine content on the thermoelectric properties of I-doped Pb0.85Fe0.15Te have been investigated. The measurement results of electrical resistivity, carrier concentration, Seebeck coefficient, and thermal conductivity in the temperature range of 300–850 K indicate that the thermoelectric transport properties of the obtained samples are sensitive to the iodine content. When the concentration of iodine is about 0.6 at.%, the maximum dimensionless figure-of-merit value of ∼0.65 at 800 K was obtained. © 2016 The Minerals, Metals & Materials Society


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.L.,Chongqing University of Science and Technology | Fu C.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Materials Science Forum | Year: 2015

Bismuth ferrite is an important material in ferroelectric photovoltaic field, because of its narrow band gap and large polarization. Doping is a common method to further improve the photovoltaic properties of bismuth ferrite. Mn-doped bismuth ferrite thin films were prepared by sol-gel method. The effects of manganese on the crystal structure, ferroelectric and photovoltaic properties have been investigated. The result indicates that Mn-doped bismuth ferrite thin films are single phase and the lattice constant increases with the increase of manganese content. As manganese content increases, the remnant polarization and coercive electric field increase, while the short circuit photocurrent density and power conversion efficiency decrease. The open circuit photovoltage increases first and reaches the maximum and then decreases as manganese content increases. The results indicate that enhanced ferroelectricity caused by addition of manganese doesn’t make improvement on the photovoltaic characteristic. © (2015) Trans Tech Publications, Switzerland.


Deng X.L.,Chongqing University of Science and Technology | Deng X.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Deng X.L.,Chongqing University | Cai W.,Chongqing University of Science and Technology | And 9 more authors.
Materials Science Forum | Year: 2015

Pure BiFeO3 ceramics and BiMnxFe1-xO3 (x=0.1, 0.15, 0.2, and 0.25) ceramics were prepared by sol-gel method. A structural phase transition from rhombohedral R3c to triangle R3m occurred in Mn-doped BFO ceramics. Mn-doped BFO ceramics exhibited better crystallinity, larger dielectric constant as well as smaller dielectric loss. Besides, a small nonlinearity of magnetization-field curves M(H) was observed, the remanent magnetization increased with the increase of manganese content, and all the BiMnxFe1-xO3 ceramics showed the typical antiferromagnetic, which could be attributed to the effective decrease in the concentration of oxygen vacancies, and the corresponding structural transition. © (2015) Trans Tech Publications, Switzerland.


Deng X.,Chongqing University | Deng X.,Chongqing University of Science and Technology | Deng X.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Huang J.,Chongqing University | And 8 more authors.
Journal of Alloys and Compounds | Year: 2016

Pure-phase perovskite BiFeO3 thin films were successfully deposited on the Pt substrates via radio frequency magnetron sputtering. The effect of O2/Ar ratio on the microstructure of BFO thin film was firstly investigated. The result shows that when O2/Ar ratio is 1:10, the BFO thin film exhibits a single perovskite phase with a dense structure. The effect of annealing temperature on the microstructure, ferroelectric, dielectric and magnetic properties of obtained thin film was subsequently investigated. The XRD result indicates that impurity phases appear whenever the annealing temperature is increased or decreased. Compared with other annealing temperatures, the BFO thin film annealed at 600 °C exhibits higher remnant polarization 2Pr of 23.26 μC/cm2, relatively larger coercive electric filed 2Ec of 563 kV/cm, higher dielectric constant of 150, lower dielectric loss of 0.03, lower leakage current density of 3.6 × 10-4 A/cm2, and saturation magnetization of 0.0036 emu/cm3. Our results provide useful information with preparing single and pure BFO thin films prepared by radio frequency magnetron sputtering to some extent. © 2016 Elsevier B.V.

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