宁波材料所在柔性磁传感薄膜材料与器件研究方面取得系列进展

正柔性智能可穿戴设备的快速发展,提出了磁电功能器件柔性化的要求。由于磁性材料的逆磁致伸缩特性,弯曲或拉伸状态所产生的应力/应变会改变磁性薄膜的磁各向异性,从而影响磁性器件的性能。如何避免应力磁各向异性对柔性磁性器件性能产生不利的影响,是柔性磁性薄膜与器件发展中所面临的重要挑战之一。近年来,中科院宁波材料所磁性材料与器件重点实验室磁电子材料与器件研究团队,系     

柔性磁传感薄膜材料与器件研究成果

<正>柔性智能可穿戴设备的快速发展,提出了磁电功能器件柔性化的要求。由于磁性材料的逆磁致伸缩特性,弯曲或拉伸状态所产生的应力/应变会改变磁性薄膜的磁各向异性,从而影响磁性器件的性能。如何避免应力磁各向异性对柔性磁性器件性能产生不利的影响,是柔性磁性薄膜与器件发展中所面临的重要挑战之一。近年来,中国科学院宁波材料技术与工程研究所磁性材料与器件重点实验室磁电子     

针对玻璃基片石英试杆影响的磁光薄膜磁性参数的估算方法

对于直接重写磁光记录薄膜的磁性测量,实际测得的磁滞回线是磁光薄膜与玻璃基片和石英试杆共同作用的结果,不能由此图直接确定基本的磁性参数。根据磁光薄膜的曲线和玻璃基片与石英试杆的曲线之间的特点,提出一种简单有效的方法快速直接确定基本的磁性参数。     

用于微电机系统的Co-Pt-P磁性薄膜的制备

使用电沉积方法制备了用于微电机系统的Co-Pt-P磁性薄膜。研究了次磷酸钠的浓度对薄膜的沉积速率、厚度、成分、表面形貌及磁性能的影响。结果表明:提高次磷酸钠的浓度,有利于加快沉积速率,提高薄膜中钴和磷的质量分数。Co-Pt-P磁性薄膜是一种典型的瘤状颗粒膜。磷的析出有利于细化薄膜表面颗粒,限制畴壁位移,从而大大提高薄膜的矫顽力。然而,高浓度的次磷酸钠会破坏镀液的稳定性,使薄膜的磁性能下降。     

钼酸钠对电沉积Co-Pt-Mo磁性薄膜性能的影响

在纯铜表面制备了Co-Pt-Mo磁性薄膜,并研究了钼酸钠的质量浓度对Co-Pt-Mo磁性薄膜性能的影响。结果表明:随着钼酸钠的质量浓度的增加,Co-Pt-Mo磁性薄膜的厚度和电流效率显著提高,钴和钼的质量分数逐渐增大,使得比饱和磁化强度增大。然而,当钼酸钠的质量浓度为10 g/L时,由于剧烈的析氢和金属氢氧化物胶体的阻碍作用,使得电流效率下降,Co-Pt-Mo磁性薄膜表面的颗粒发生团聚现象,孔隙率增大,矫顽力降低。当钼酸钠的质量浓度为8 g/L时, Co-Pt-Mo磁性薄膜具有致密的结构和最大的矫顽力。     

磁场下电沉积制备Co-Pt-P磁性薄膜

在磁场下电沉积制备Co-Pt-P磁性薄膜。研究了电流、温度、磁场强度对薄膜性能的影响。结果表明:磁场对镀层的成分、微观结构及磁性能有一定程度的影响。     

Fe掺杂对ZnS稀磁薄膜的磁特性影响

制备了Fe掺杂Zn S稀磁薄膜(Fe掺杂量x=0. 000,0. 005,0. 010,0. 015),利用XRD、PL光谱以及磁性测试系统测量分析了Fe掺杂对Zn S薄膜的晶体结构、发光特性及磁特性的影响。结果表明,薄膜的饱和磁化强度随Fe掺杂量x增加而逐渐增大,Fe掺杂量x> 0. 005时,薄膜的结晶品质逐渐变差,缺陷数量随之增多,导致磁信号通过缺陷传导而逐渐增强,致使其饱和磁化强度增大。     

脉冲电沉积Co-W磁性薄膜

采用脉冲电沉积法制备Co-W 磁性薄膜.研究脉冲周期和占空比对沉积速率,Co-W薄膜的形貌、结构以及磁性能的影响.结果表明:脉冲周期与占空比对薄膜的沉积速率、形貌、结构和磁性能都有较大的影响.随着脉冲周期和占空比的不断增加,沉积速率呈现先增大后减小的趋势;而Co-W薄膜的矫顽力呈现减小的趋势.这主要是由于晶粒尺寸增大的缘故.AFM研究表明:随着占空比增大,薄膜颗粒增大,表面平整度下降,空隙率增加;脉冲周期影响薄膜表面聚集颗粒团;增大脉冲周期,该聚集团会增大.     

化学镀CoWP薄膜的制备及磁性研究

利用化学镀的方法制备了CoWP磁性薄膜。研究了施镀时间对化学镀CoWP薄膜矫顽力和饱和磁化强度的影响,并利用场发射扫描电子显微镜(FSEM)、X射线衍射(XRD)和振动样品磁强计(VSM)研究了CoWP磁性薄膜的表面形貌、成分、微结构及磁学性能。结果表明,化学镀CoWP薄膜主要为hcp结构Co相,晶粒大小为2~3μm;随着施镀时间的增加,CoWP薄膜的饱和磁化强度也随之增大,最高达到122emu/g;CoWP薄膜的矫顽力都在250Oe以下。通过计算Kelly-Hankel(δM)曲线,证实了CoWP磁性薄膜中存在交换耦合作用,产生了剩磁增强效应。     

Fe掺杂对ZnS稀磁薄膜的磁特性影响

制备了Fe掺杂Zn S稀磁薄膜(Fe掺杂量x=0. 000,0. 005,0. 010,0. 015),利用XRD、PL光谱以及磁性测试系统测量分析了Fe掺杂对Zn S薄膜的晶体结构、发光特性及磁特性的影响。结果表明,薄膜的饱和磁化强度随Fe掺杂量x增加而逐渐增大,Fe掺杂量x 0. 005时,薄膜的结晶品质逐渐变差,缺陷数量随之增多,导致磁信号通过缺陷传导而逐渐增强,致使其饱和磁化强度增大。     

Evaluation of sub-micrometer parylene C films as an insulation layer using electrochemical impedance spectroscopy

We investigated the insulation performance of sub-micrometer parylene C films over time using electrochemical impedance spectroscopy (EIS). For this, interdigitated electrodes were fabricated and completely encapsulated with parylene C in thicknesses of 50, 100, 200, and 500 nm. The EIS was measured in phosphate buffered saline (PBS) solution under an accelerated aging condition at 90 °C over 45 days. To analyze the EIS data, the equivalent circuit models of coating at different stages of coating degradation were used and the lumped circuit parameters of the best fitted equivalent circuit model were extracted by curve fitting. The analysis of impedance using the equivalent circuit model and the FTIR measurements suggest that sub-micrometer parylene C coatings exhibited delamination resulting from water diffusion from the top surface as soon as being immersed in PBS solution, although the degree of delamination varied depending on the film thickness. The penetration of water through sub-micrometers thick parylene C films can occur as quickly as the film is in contact with solution, unlike for thicker coatings in several micrometers where water diffusion would be saturated before water reaches the bottom surface of the coating.     

交流阻抗谱研究钙磷陶瓷电沉积层的结构

用交流阻抗技术研究了不同电沉积时间的钙磷陶瓷沉积层。结果表明，沉积时间不同的陶瓷沉积层的交流阻抗谱存在显著的差别。采用双层结构物理模型，对不同沉积时间陶瓷沉积层的交流阻抗谱进行计算机拟合，得到的等效电路各元件拟合值显示：电极表面钙磷陶瓷为内密外疏型梯度沉积层。在陶瓷电沉积过程中，钙磷晶粒同时沉积于距电极表面不同距离的部位，沉积层厚度增加的同时内层密度也在逐渐增加，整个 只层的梯度结构处于动态变化之中。     

A carbon nanotube film as a radio frequency filter

This paper proposes a new concept for the application of carbon nanotubes to electronic devices. A carbon nanotube (150-200 nm width, few μm length) film grown on a metal sensitized quartz surface was modeled using a two-pole lumped element equivalent circuit consisting of a capacitor, an inductor, and two resistors. The capacitor was in series with the inductor resulting in band-stop filter characteristics with a central frequency of 18 MHz. The reactive subcircuit was in parallel with one resistor and in series with the other. The magnitude of the parallel resistance had a large influence on the efficiency of the reactive elements and the filter quality factor. A two-dimensional carbon nanotube film is expected to be suitable in the design of miniaturized RF filters.     

Impedance study of the passive film on stainless steel 304 in pH 8 carbonate solution

The effects of applied d.c. potential and polarization time on the passivation of stainless steel 304 (SS304) were investigated in deaerated 1 M NaHCo₃ aqueous solutions at pH 8. Electrochemical impedance spectroscopy was used in conjunction with a rotating disc electrode. The data were analysed by considering an equivalent circuit. The changes in impedance parameters at applied d.c. potential signal changes in the properties of passive films on SS304 and allow to distinguish the parameters at low potential (–0.6 to 0.3 V vs SCE) from a different one at high potential (0.5 to 0.8 V vs SCE). The oxidation reactions were controlled by both charge transfer and mass transfer processes. Diffusional resistance was high for both passive films and was considered to represent the resistance to movement of ions or vacancies through the surface layer of oxide films. It is deduced that the passive film present in the low potential region is partially dissolved at 0.4 V vs SCE and that a new passive film is formed in the higher potential region. The equivalent circuit used to obtain the best fit and the fitting parameters was dependent on the electrode potential and the polarization time. The reproducibility of the impedance spectra at constant potentials demonstrate that the passive film formation is highly irreversible process. No traces of localized corrosion were detected but, for a high potential and long polarization time, the electrode surface coloration to a uniform gold colour confirms the film thickening.     

Fluorinated functionalized EDOT-based conducting films

Three ethylenedioxithiophene (EDOT) derivatives bearing either perfluoro- or ether perfluoro-alkyl chains were synthesized with the objective to prepare films with dry and chemically immobilized lubrication properties. The corresponding fluorinated PEDOT films were deposited on platinum surface by electropolymerization. Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) analyses (both quartz resonant frequency and resonant admittance) of the growing steps are described. The electroactive behavior of the films versus their doping level was followed by electrochemical impedance spectroscopy (EIS) through equivalent circuit fitting procedure and compared to their CV responses. Hysteresis in fit parameters corresponding to capacity and film resistance between the forward and the backward scans are observed and discussed. Control of the chemical structures and charge effects on PEDOT chains are followed by an XPS analysis. From these analyses, it appears that the fluorinated side-arm does not alter both the growing and the electrical properties of the films in respect to the pristine PEDOT taken as reference.     

Multiferroic nanoscale Bi(2)FeCrO(6) material for spintronic-related applications

We report the control of the growth mode of Bi(2)FeCrO(6) thin and ultrathin films by either tuning the pulsed laser deposition parameters or by using a buffer layer. The films are epitaxial and the heterostructures exhibit very smooth interfaces, thus eliminating the main obstacle in the realization of tunnel junctions. By characterizing the functional properties of thin films we find that Bi(2)FeCrO(6) retains its room temperature multiferroic character even at the nanoscale. The coexistence of these properties in ultra-thin Bi(2)FeCrO(6) films will pave the way to design multifunctional devices for applications in spintronics and electronics, such as ferroelectric tunnel junctions or magnetic tunnel junctions with ferroelectric barriers.     

Effect of pH,Fluorination, and Number of Layers on the Inhibition of Electrochemical Reactions by Grafted,Hyperbranched Poly(acrylic acid) Films

We report the electrode-passivation properties of both fluorinated and unmodified hyperbranched poly(acrylic acid) (PAA) films as a function of pH and the number of PAA layers. Both cyclic voltammetry and ac-impedance spectroscopy show that the extent of blocking increases with the number of layers, regardless of the solution pH. However, passivation resulting from unfluorinated PAA films decreases with increasing pH, while passivation due to fluorinated films increases with increasing pH. Three-layer fluorinated films can increase the charge transfer resistance of the electrode by up to a factor of 6 × 10⁴. Although Randles' equivalent circuit can be used to model the electrochemistry of electrodes covered with unfluorinated PAA, fluorinated PAA-coated electrodes often require additional circuit elements due to the high resistance of these hydrophobic films.     

Electrochemical impedance study of Li-ion insertion into the raw acid-oxidized carbon nanotubes

Electrochemical impedance spectroscopy (EIS) was applied for the raw acid-oxidized multiwall carbon nanotubes during Li-ion insertion with the electrolyte of 1M LiPF₆ in EC and DMC. Impedance spectroscopy consists of two separated arcs in the high and intermediate range frequency. The high frequency arc is attributed to Li migration within the surface films and the medium frequency arc is associated with the charge transfer. Obtained spectra were analyzed with an equivalent circuit model. Kinetic parameters such as the charge transfer resistance, film resistance, diffusion coefficient and exchange current were evaluated. The contribution of the film to the measured impedance response is discussed.     

The inductive behavior derived from hydrolysis of polyaniline

Electrochemical impedance spectroscopy (EIS) was used to study the impedance characteristics of polyaniline (PANI) films deposited by cyclic voltammetry with different anodic potential limits. The presence of benzoquinone (BQ) as hydrolysis product of PANI was evident for PANI films deposited with anodic potential limits ≥0.80 V. The data from EIS for PANI film with inbuilt BQ reveals an inductive behavior. The existence of inductive behavior for PANI film under different applied bias potentials was brought out through fitting of EIS data with equivalent circuits and deducing the value of an inductor element (L). The inductive behavior was attributed to arise due to the presence of BQ within PANI films and adequately supported by the results from X-ray photoelectron spectroscopy (XPS). The value of L reaches saturation for the PANI film synthesized with an upper potential limit of 0.90 V and measured at 0.70 V. The EIS and XPS results of the poly(N-methylaniline) (PNMA) film prepared under similar conditions corroborated with the observation that the presence of BQ within PANI results inductive characteristics to PANI     

An Investigation of Current Reversal Mode for Gas Sensing With a Solid Electroyte

Current reversal mode (CRM) is a dynamic measuring technique, which has the potential to determine accurately the equilibrium emf of a solid electrolyte sensor, while providing additional information regarding sensor resistance. This can be exploited as a diagnostic tool. A fundamental study, using an oxygen sensor with yttria-stabilized zirconia as the solid electrolyte, has been performed to identify the CRM parameters of frequency and bias voltage for making accurate measurements. A mathematical model has been developed for the application of CRM in terms of an equivalent electrical circuit. The predictions of the model agree well with the experimental data.