窄带Mo／Si多层膜反射镜

设计并制备了窄带M o/S i多层膜反射镜。利用高反射级次和减小M o层厚度两种方法减小M o/S i多层膜反射镜光谱宽度。对M o层厚度分别为2 nm和3 nm的M o/S i多层膜,设计了反射级次分别从1到6的多层膜系。制备方法采用直流磁控溅射技术,在国家同步辐射光谱与计量站上测试。结果表明,带宽随着反射级次增加而减少,在同一反射级次,M o层厚度为2 nm的多层膜反射光谱带宽较小。     

Study on initiation of localised corrosion on copper thin film electrode by combinational use of an EQCM with a liquid-phase ion gun

A new method allowing simultaneous measurements of anodic currents and small mass changes during initiation and early growth of a single localised corrosion site was discussed. An electrochemical quartz crystal microbalance (EQCM) was combined with a liquid-phase ion gun consisting of an Ag/AgCl microelectrode which produces chloride ions, causing local breakdown of passive film and pit growth. The method was applied to copper thin films polarised anodically at 0.6 or 0.8 V (SHE) in pH 8.4 borate buffer solution. It was found from comparison between coulometry and gravimetry that copper dissolves as Cu²⁺ during the pit growth. The shape of the pit was almost circular and the average pit current density, i_p=25 A cm⁻² was evaluated from the kinetics of 2D pit growth.     

Effect of Cr3+- based conversion films on the corrosion behaviour of electrodeposited composite ternary zinc alloys with embedded carbon nanotubes

ABSTRACT

Composite ternary zinc-based alloys Zn-Ni-P and Zn-Fe-P containing embedded multi-walled carbon nanotubes (CNT) were obtained electrochemically. They were treated additionally in an environmentally friendly chemical conversion solution for passivation based on Cr³⁺-compound. The surface morphology, chemical and phase composition of the coatings after their treatment in the passivating solution were determined by SEM, EDS and XRD analysis respectively. The corrosion behaviour of composite alloy deposits both with or without additional conversion film (CF) was investigated in a model corrosion medium of 5% NaCl using selected methods such as potentodynamic polarisation (PD) curves, electrochemical impedance spectroscopy (EIS) and polarisation resistance (R_p) measurements. The changes in the surface morphology and phase composition of the corrosion tested samples were determined by SEM and XRD analysis. The corrosion studies indicated that the presence of a CF leads to a delay in the anodic dissolution process during the polarisation.     

Ionic Gel Modulation of RKKY Interactions in Synthetic Anti‐Ferromagnetic Nanostructures for Low Power Wearable Spintronic Devices

To meet the demand of developing compatible and energy‐efficient flexible spintronics, voltage manipulation of magnetism on soft substrates is in demand. Here, a voltage tunable flexible field‐effect transistor structure by ionic gel (IG) gating in perpendicular synthetic anti‐ferromagnetic nanostructure is demonstrated. As a result, the interlayer Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction can be tuned electrically at room temperature. With a circuit gating voltage, anti‐ferromagnetic (AFM) ordering is enhanced or converted into an AFM–ferromagnetic (FM) intermediate state, accompanying with the dynamic domain switching. This IG gating process can be repeated stably at different curvatures, confirming an excellent mechanical property. The IG‐induced modification of interlayer exchange coupling is related to the change of Fermi level aroused by the disturbance of itinerant electrons. The voltage modulation of RKKY interaction with excellent flexibility proposes an application potential for wearable spintronic devices with energy efficiency and ultralow operation voltage.     

E‐field Control of the RKKY Interaction in FeCoB/Ru/FeCoB/PMN‐PT (011) Multiferroic Heterostructures

E‐field control of antiferromagnetic (AFM) orders is promising for the realization of fast, compact, and energy‐efficient AFM applications. However, as the AFM spins are strongly pinned, the E‐field control process is mainly based on the exchange bias regulation that usually confines at a low temperature. Here, a new magnetoelectric (ME) coupling mechanism for the modulation of AFM orders at room temperature is explored. Based on the FeCoB/Ru/FeCoB/(011) Pb(Mg_1/3Nb_2/3)O₃‐PbTiO₃ (PMN‐PT) synthetic antiferromagnetic (SAF) heterostructures, the external E‐field generates relative magnetization switching in the two ferromagnetic (FM) layers, leading the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction tuning. This voltage‐induced switching behavior can be repeated in a stable and reversible manner for various SAFs, which is a key challenge in the E‐field control of AFM coupling and is not resolved yet. The voltage‐induced RKKY interaction changes by analyzing the dynamic optical and acoustic modes is quantified, and with first‐principles calculations, it is found that the distortion of the Fermi surface by the lattice reconstruction is the key of the relative magnetization switching and RKKY interaction modulation. This voltage control of the RKKY interaction in ME heterostructures provides an easy way to achieve the next generation of AFM/FM spintronic applications.     

Preparation and electrical properties of ZnO‐Bi2O3‐based multilayer varistors with base metal nickel inner electrodes

In this study, ZnO‐Bi₂O₃‐based multilayer varistors (MLVs) cofired with nickel (Ni) inner electrodes were prepared by tape‐casting method. Samples were sintered in pure nitrogen (N₂) to keep Ni from being oxidized, and then reoxidized in air to obtain the nonlinear properties (reduction‐reoxidation method). The EDAX results showed that Ni inner electrodes are stable and have no evident migration into ZnO‐Bi₂O₃‐based ceramics when sintered in N₂. The influence of reoxidation temperature on microstructures and nonlinear properties of samples were studied. Samples reoxidized at the temperatures lower than 650°C showed poor nonlinear properties. After reoxidized in air at 700°C for 2 hours, samples exhibited nonlinear properties of V_1 mA=16.3 V, α=26.5, I_L=0.68 μA. At the reoxidation temperature higher than 750°C, the oxidation of Ni inner electrodes deteriorated the nonlinear properties of samples. It demonstrated that ZnO‐Bi₂O₃‐based MLVs with base metal Ni inner electrodes proposed in this work are suitable for reduction‐reoxidation method. The replacement of noble metals Pt or Ag/Pd alloys by base metal Ni is expected to lower the cost of ZnO‐Bi₂O₃‐based MLVs.     

Comparison of direct electrocaloric characterization methods exemplified by 0.92 Pb(Mg1/3Nb2/3)O3‐0.08 PbTiO3 multilayer ceramics

Electrocaloric device structures have been developed as multilayer ceramics (MLCs) based on fundamental research carried out on PMN‐8PT bulk ceramics. Two different MLC structures were prepared with nine layers each and layer thicknesses of 86 μm and 39 μm. The influence of the device design on its properties has been characterized by microstructural, dielectric, ferroelectric, and direct electrocaloric measurement. For direct characterization two different methods, ie temperature reading (thermistor and thermocouple) and heat flow measurement (differential scanning calorimetry), were used. A comparison of results revealed a highly satisfactory agreement between the different methods. This study confirms that MLCs are promising candidates for implementation into energy‐efficient electrocaloric cooling systems providing large refrigerant volume and high electrocaloric effect. Due to their micron‐sized active layers, they allow for the application of high electric fields under low operation voltages. We measured a maximum electrocaloric temperature change of ΔT=2.67 K under application/withdrawal of an electric field of ΔE=16 kV mm^?1, which corresponds to operation voltages below 1.5 kV.     

Electrochromism and reversible changes in the position of fundamental absorption edge in cathodically deposited amorphous WO3

Amorphous WO₃ (a-WO₃) films have been produced by electrodeposition from a sodium tungstate-based aqueous electrolyte. Their coloration under the action of cathode current in 1N H₂SO₄ is accompanied by a reversible shift of ∼0.42 eV in the fundamental absorption edge of the oxide towards higher quantum energies. The shift of the edge is proportional to the change in the potential of the WO₃ electrode being colored and is caused by the sequential filling, by injected electrons, of levels in the energy spectrum of electronic states formed by the unoccupied d-orbitals of W⁶⁺ centers. The optical characteristics of the W⁵⁺ centers which are formed in this case (color centers of electrochromic material) depend on whether a particular tungsten atom has a double bond to the oxygen atom (WO type bond). At the initial stage of coloration, injected electrons are captured mainly by the W⁶⁺ centers that have no such bonds. Then, W⁶⁺ centers with WO bonds, which have a higher position of the unoccupied d-orbitals on the energy scale, are also filled; this is accompanied by the appearance of an extra absorption band with maximum at ∼2 eV in the optical spectrum of films.     

Formation and Dehydration Enthalpy of Potassium Hexaniobate

The formation energetics of hydrous and dehydrated potassium hexaniobates are investigated using high‐temperature oxide melt solution calorimetry. The enthalpies of formation of K₄Nb₆O₁₇ and K₄Nb₆O₁₇·3H₂O from oxides are (?864.42 ± 10.63) and (?899.32 ± 11.48) kJ/mol, respectively. The formation enthalpy of K₄Nb₆O₁₇ from elements is (?7289.64 ± 12.50) kJ/mol, and of K₄Nb₆O₁₇·3H₂O is (?8181.94 ± 13.24) kJ/mol. The enthalpy of dehydration (ΔH_dehy) for the reaction K₄Nb₆O₁₇·3H₂O (xl, 25°C) = K₄Nb₆O₁₇ (xl, 25°C) + 3H₂O (l, 25°C) is endothermic and is 34.60 ± 7.56 kJ/mol. The ΔH_dehy per mole of water, 11.53 ± 2.52 kJ/mol, indicates the water molecules in K₄Nb₆O₁₇·3H₂O are not just physically adsorbed, but loosely bonded in the K₄Nb₆O₁₇ phase, presumably in specific interlayer sites. The loss of this water near 100°C on heating is consistent with the weak bonding of water.