Local leakage current behaviours of BiFeO3 films

The leakage current behaviours of polycrystalline BiFeO₃ thin films are investigated by using both conductive atomic force microscopy and current-voltage characteristic measurements. The local charge transport pathways are found to be located mainly at the grain boundaries of the films. The leakage current density can be tuned by changing the post-annealing temperature, the annealing time, the bias voltage and the light illumination, which can be used to improve the performances of the ferroelectric devices based on the BiFeO₃ films. A possible leakage mechanism is proposed to interpret the charge transports in the polycrystalline BiFeO₃ films.     

光对ZnO薄膜电致电阻转变效应的调控研究

利用磁控溅射技术在镀铂硅片上制备ZnO薄膜,X射线衍射测试表明ZnO薄膜为纯相结构,原子力显微镜测试显示ZnO薄膜表面平整均匀,均方根粗糙度为1.87nm.在室温下对Au/ZnO/Pt三明治结构的电输运行为进行了研究,结果表明同时存在电致电阻转变效应和光伏效应,并且光照可调控电致电阻.当光强为360μW·cm-2时,电阻调控幅度达78%,这种光调控的电致电阻转变有助于实现多态存储,提高存储密度.     

Giant low-frequency magnetoelectric torque (MET) effect in polyvinylidene-fluoride (PVDF)-based MET device

A polyvinylidene-fluoride(PVDF)-based magnetoelectric torque(MET) device is designed with elastic layer sandwiched by PVDF layers, and low-frequency MET effect is carefully studied. It is found that elastic modulus and thickness of the elastic layer have great influences on magnetoelectric(ME) voltage coefficient(α_(ME)) and working range of frequency in PVDF-based MET device. The decrease of the modulus and thickness can help increase the α ME. However,it can also reduce the working range in the low frequency. By optimizing the parameters, the giant α_(ME) of 320 V/cm·Oe(1 Oe = 79.5775 A·m~(-1) at low frequency(1 Hz) can be obtained. The present results may help design PVDF-based MET low-frequency magnetic sensor with improved magnetic sensitivity in a relative large frequency range.     

Enhanced energy storage behaviors in free-standing antiferroelectric Pb(Zr_(0.95)Ti_(0.05))O_3 thin membranes

Free-standing antiferroelectric Pb(Zr_(0.95)Ti_(0.05)O_3(PZT(95/5)) thin film is fabricated on 200-nm-thick Pt foil by using pulsed laser deposition.X-ray diffraction patterns indicate that free-standing PZT(95/5) film possesses an α-axis preferred orientation.The critical electric field for the 300-nm-thick free-standing PZT(95/5) film transiting from antiferroelectric to ferroelectric phases is increased to 770 kV/cm,but its saturation polarization remains almost unchanged as compared with that of the substrate-clamped PZT(95/5) film.The energy storage density and energy efficiency of the substrate-clamped PZT(95/5) film are 6.49 J/cm~3 and 54.5%,respectively.In contrast,after removing the substrate,the energy storage density and energy efficiency of the free-standing PZT(95/5) film are enhanced up to 17.45 J/cm~3 and 67.9%,respectively.     

Fabrication,properties, and applications of flexible magnetic films

Flexible magnetic devices, i.e., magnetic devices fabricated on flexible substrates, are very attractive in applications such as detection of magnetic field in an arbitrary surface, non-contact actuators, and microwave devices, due to their stretchable, biocompatible, light-weight, portable, and low cost properties. Flexible magnetic films are essential for the realization of various functionalities of flexible magnetic devices. To give a comprehensive understanding for flexible magnetic films and related devices, recent advances in the study of flexible magnetic films are reviewed, including fabrication methods, magnetic and transport properties of flexible magnetic films, and their applications in magnetic sensors, actuators, and microwave devices. Our aim is to foster a comprehensive understanding of these films and devices. Three typical methods have been introduced to prepare the flexible magnetic films, by deposition of magnetic films on flexible substrates, by a transfer and bonding approach or by including and then removing sacrificial layers. Stretching or bending the magnetic films is a good way to apply mechanical strain to them, so that magnetic anisotropy, exchange bias, coercivity, and magnetoresistance can be effectively manipulated. Finally, a series of examples is shown to demonstrate the great potential of flexible magnetic films for future applications.