Enhancement of ferromagnetic resonance in Al_2O_3-doped Co_2FeAl Heusler alloy film prepared by oblique sputtering

Large and variable in-plane uniaxial magnetic anisotropy in a nanocrystalline （Co2FeA1）97.8（Al2O3）2.2 soft magnetic thin film is obtained by an oblique sputtering method without being induced by magnetic field or post anneaiing. The in-plane uniaxiai magnetic anisotropy varies from 50 Oe to 180 Oe （1 Oe=79.5775 A·m-1） by adjusting the sample＇s position. As a result, the ferromagnetic resonance frequency of the film increases from 1.9 GHz to 3.75 GHz.

Fabrication and magnetic properties of NiFe-ZnO nano-granular films

Excellent soft magnetic and high frequency prop- erties were obtained successfully in the （Ni75Fe25）x（ZnO）1-x granular films fabricated on the glass substrate by RF magnetron oblique sputtering. The microstructure, mag- netic and high frequency properties were investigated systematically. High resolution transmission electron micrographs show that the film consists of fcc Ni75Fe25 particles uniformly embedded in an amorphous insulating matrix ZnO with particle size a few nanometers. The （Ni75Fe25）x（ZnO）1-x films exhibit excellent soft magnetic properties in a widex range from 0.50 to 0.80 with coer- civity not exceeding 5 × 10^-4 T, which is ascribed to the exchange coupling between magnetic particles. Especially for the sample with x = 0.64, coercivities in hard and easy axes are 5.0 ×10^-5 and 3.6 × 10^-4 T, respectively, and the electric resistivity ρ reaches 1,790 μΩ.cm. The dependence of complex permeability u = u′- ju″on frequency f shows that the real part u′ is more than 130 below 500 MHz, and the ferromagnetic resonance fre- quency fr reaches 1.32 GHz, implying the promising for high frequency application.

Substrate bias effects on collector resistance in SiGe heterojunction bipolar transistors on thin film silicon-on-insulator

An analytical expression for the co/lector resistance of a novel vertical SiGe heterojunction bipolar transistor （HBT） on thin film silicon-on-insulator （SOI） is obtained with the substrate bias effects being considered. The resistance is found to decrease slowly and then quickly and to have kinks with the increase of the substrate-collector bias, which is quite different from that of a conventional bulk HBT. The model is consistent with the simulation result and the reported data and is useful to the frequency characteristic design of 0.13 μtm millimeter-wave SiGe SOI BiCMOS devices.

印刷电子应用越来越广

最早的印刷电子开始于应用喷墨印刷技术,将导电材料打印在承印物上面,形成电路或天线。经过十多年的演进,现在的印刷电子已发展出更先进的印刷方法,应用更为广泛,甚至利用喷墨技术在打印过程中直接形成电子电路、传感器,形成系统和设备。印刷电子牵涉到材料、电子和喷墨技术,可以实现超低单价成本,还可以大量制造。

Innovative coaxial high-temperature thin-film sensor with core-shell structure surpassing traditional multilayer films

High-temperature thin-film sensors(TFSs)often suffer from inadequate tolerance to elevated temperatures.In this study,an innovative approach is presented to fabricate in situ integrated TFSs with a core-shell structure on alloy components using coaxial multi-ink printing technique.This method replaces traditional layerby-layer(LbL) deposition and LbL sintering processes and achieves simplified one-step manufacturing.The coaxial TFS includes a conductive Pt core for conducting and sensing and a dielectric shell for electrical isolation and high-temperature protection.The coaxial Pt resistance grid demonstrates excellent high-temperature stability,with a resistance drift rate of only 0.08%·h^(-1) at 800 ℃,significantly lower than traditional Pt TFSs.By employing this method,a Pt thin-film strain gauge(TFSG) is fabricated that boasts remarkable high-temperature electromechanical properties.This effectively addresses the problem of sensitivity degradation experienced by traditional LbL Pt TFSGs when subjected to high temperatures.We demonstrate the system integration potential of the technique by printing and verifying the functionality of a long-path thinfilm resistance grid on turbine blades,which can withstand butane flame up to ~1300℃.These results showcase the potential of core-shell structure of the coaxial TFS for high-temperature applications,providing a novel approach to develop high-performance TFS beyond traditional multilayer structure.

Research at the University of Kent and Subsequent Research Activities

The author＇s research activities undertaken at the Applied Optics Group, the University of Kent at Canterbury are reviewed, during his time there from 1988-1992 and 1994-1996, followed by a summary of recent research. The areas of interest are high finesse ring resonators, tunable optical filters, novel optical fiber grating sensors in glass and polymer, femtosecond laser inscription and micromachining, environmental pollution monitoring, hydrogen activated Pd films on silicon and impurity measurement on silicon wafers.

LARGE ELECTROCALORIC EFFECT IN RELAXOR FERROELECTRICS

Organic and inorganic relaxor ferroelectrics used for electrocaloric effect(ECE)applications areintroduced.Relaxor ferroelectrics offer several advantages for ECE devices,e.g.,infinite stateswithout applying electric field,field-induced large polarization,no-hysteresis ofheating and cooling,small-hysteresis polarization loss,room temperature phase transition,and broad temperaturerange.The ECE in relaxor ferroelectrics under a high electric field can be described using a theorysimilar to that for first-order phase transition materials.Large ECE was observed directly inhigh-energy electron irradiated poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)68/32 mol%copolymers,P(VDF-TrFE-CFE)(CFE-chlorofluoroethylene)59.2/33.6/7.2 mol%terpolymers,P(vDF-TrFE-CFE)-P(VDF-CTFE)(CTFE-chlorotrifluoroethylene)95/5 wt%terpolymer blended films,and(PbLa)(ZrTi)O_(3)(PLZT)ceramic thin films.ECE reported inPb(Sc_(1/2)Ta_(1/2))O_(3)(PST),Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-PT)thin films is also summarized.Finally,the perspective of ECE devices is llustrated.

INFLUENCE OF Mg-DOPING ON SYNTHESIS OF SOL-GEL DERIVED BST THIN FILMS

Solid solutions of Ba_(1-x)Sr_(x)TiO_(3)(BST)type are very attractive for application in information technology,but also in microwaves for such electrically controlled devices as phase shifters,tunablefilters,steerable antennas,varactors,etc.In the present study thinfilms of a BST solid solution with x=0.4(BST60/40)were prepared by the sol-gel-type chemical solution deposition method.The influence of y=1,3 and 5 mol.%MgO doping on synthesis of BST60/40 thinfilms was studied.Thermal analysis both differential and thermogravimetric were used to determine the thermochemical properties of dried BST60/40-MgO gel powders.A multilayer spin-coating approach was utilized for the Ba_(0.6)Sr_(0.4)TiO_(3)-MgO thinfilm deposition on stainless steel substrates.X-ray diffraction analysis,SEM and EDS were utilized for thinfilm characterization in terms of its crystalline structure,microstructure and chemical composition.Raman spectroscopy investigation of MgO-doped Ba_(0.6)Sr_(0.4)TiO_(3)thinfilms grown on stainless steel substrates were also performed within the wavenumber range k=40-1070 cm^(-1).

Improving dehydrogenation properties of Mg/Nb composite films via tuning Nb distributions

t To investigate the effect of Nb on the dehydro- genation properties of Mg-Nb composite films, Mg/Nb eight- layer film and Mg- 10 at% Nb alloy film with the similar Mg- to-Nb atomic ratio were prepared by magnetron sputtering. Results show that both Mg/Nb eight-layer film and Mg- 10 at% Nb alloy film exhibit excellent de/hydrogenation properties. Mg- 10 at% Nb alloy film starts to release hydrogen at 108 ℃, and its desorption peak temperature is lower to 146 ℃, which is much better than that of pure MgH2 under the same condi- tion. Scanning electron microscopy （SEM） results demon- strate that the dispersive Nb nanoparticles in Mg/Nb eight- layer film may serve as nucleation sites for Mg ←→ MgH2 reactions, which can provide channels for H diffusion. For Mg- 10 at% Nb alloy film, the uniform distributions of Nb can accelerate the hydrogen diffusion and effectively improve the dehydrogenation kinetics for MgH2. This study provides an enlightening way for designing and preparing Mg-based composite films with excellent dehydrogenation properties.

Activating AIN thin film by introducing Co nanoparticles as a new anode material for thin-film lithium batteries

A1N/Co nanocomposite thin films were fabricated by pulsed laser deposition and investigated as new anode materials for lithium-ion batteries for the first time. The combination of electrochemically inactive A1N and Co in nanometer scale boosted the electrochemical performance of the thin films surprisingly. A high reversible capacity of 555 mAh.g^-1 after 100 discharge-charge cycles at a current density of 500 mA.g^-1 is obtained for the A1N/Co nanocomposite thin films, and 372 mAh.g^-1 can be retained at a high rate up to 16C, exhibiting promising cycle stability and rate capability. The electrochemical reaction mechanism study reveals that Co nanoparticles could not only provide high electronic conductivity for the thin films, which facilitate the thorough decomposition of A1N in the initial discharge process, but also react with Li3N to form a new species CozN during charge process, thus ensuring large capacity and high reversibility of A1N/Co nanocomposite thin films in sub- sequent cycles. This study provides a new perspective to design advanced electrode materials for lithium-ion batteries.

MAGNETOELECTRIC RESPONSES IN MULTIFERROIC COMPOSITE THIN FILMS

Multiferroic composite thinfilms of ferroelectrics and magnets have attracted ever-increasing interest in most recent years.In this review,magnetoelectric(ME)responses as well as their underlying ME coupling mechanisms in such multiferroic composite thinfilms are discussed,oriented by their potential applications in novel ME devices.Among them,the direct ME response,i.e.,magnetic-field control of polarization,can be exploited for micro-sensor applications(sensing magneticfield,electric current,light,etc.),mainly determined by a strain-mediated coupling interaction.The converse ME response,i.e.,electric-field modulation of magnetism,offers great opportunities for new potential devices for spintronics and in data storage applications.A series of prototype ME devices based on both direct and converse ME responses have been presented.The review concludes with a remark on the future possibilities and scientific challenges in thisfield.