Comparison of Alternative Techniques for Characterizing Magnetostriction and Inverse Magnetostriction in Magnetic Thin Films

We compare the direct and inverse techniques of measuring magnetostriction in magnetic thin films. We chose a set of four magnetic thin film samples (Co$_{95}$Fe$_5$, Co$_{60}$Fe$_{20}$B$_{20}$, Ni$_{65}$Fe$_{15}$Co$_{20}$, and Ni$_{80}$Fe$_{20}$) for the measurements, representing positive and negative magnetostriction and having saturation magnetostriction of magnitudes ranging from $10^{-7}$ to $10^{-5}$. We made the direct measurements on a high-precision optical cantilever beam system, and we carried out the inverse magnetostriction measurements on a nondestructive inductive $Bhbox{-}H$ looper with three-point bending stage.      

Effect of Factors on Coercivity in Sr–La–Co Sintered Ferrite Magnets

We varied the composition and sintering temperature of Sr–La–Co ferrite magnets to analyze the effects of various important factors on coercivity $(H_{rm cJ})$. We examined the effects of crystal grain size and distribution, the mechanism of magnetization reversal, the degree of crystal grain orientation (OD), and the anisotropy field $(H_{rm A})$ on $H_{rm cJ}$. We proposed an equation based on the experimental results that expresses the measured $H_{rm cJ}$ and considers these effects as $H_{rm cJ} = C_{rm t}(0.4/R_{rm h})$ OD $(H_{rm A} - H_{rm d} - H_{rm in})$, where $C_{rm t}, R_{rm h}, H_{rm d}$, and $H_{rm in}$ are the crystal grain size effects on $H_{rm cJ}$ of sintered magnet, rotational hysteresis integral corresponding to the mechanism of magnetization reversal, demagnetizing field of shape anisotropy, and interaction field between crystal grains, respectively. We found that apart from the volume ratio for single-domain crystal grains and $H_{rm A}$, the mechanism of magnetization reversal had significant effects on $H_{rm cJ}$ for Sr–La–Co sintered ferrite magnets.      

Effects of Post-Deposition Annealing and Oxygen Content on the Structural and pH-Sensitive Properties of Thin Nd $_{2}$O $_{3}$ Films

This paper describes the structural properties and sensing characteristics of thin Nd$_{2}$O$_{3}$ sensing membranes deposited on silicon substrates by means of reactive sputtering. X-ray diffraction, X-ray photoelectron spectroscopy, and atomic-force microscopy were used to study the chemical and morphological features of these films as functions of the growth conditions (argon-to-oxygen flow ratios of $20/5, 15/10$ and $10/15$; temperatures ranging from 600$~^{circ}$C to 800$~^{circ}$C). The thin Nd$_{2}$O$_{3}$ electrolyte-insulator-semiconductor devices prepared under a 15/10 flow ratio with subsequent annealing at 700$~^{circ}$C exhibited a higher sensitivity (56.01 mV/pH, in the solutions from pH 2 to 12), a smaller hysteresis voltage (4.7 mV in the pH loop $7 to 4 to 7to 10 to 7$), and a lower drift rate (0.41 mV/h in the pH 7 buffer solution) than did those prepared at the other conditions. We attribute this behavior to the optimal oxygen content in this oxide film forming a high density of binding sites and a small surface roughness.      

Optimization of Spin-Valve Structure NiFe/Cu/NiFe/IrMn for Planar Hall Effect Based Biochips

This paper deals with the planar Hall effect (PHE) of Ta(5)/NiFe$(t_{rm F})$/Cu(1.2)/NiFe$(t_{rm P})$/IrMn(15)/Ta(5) (nm) spin-valve structures. Experimental investigations are performed for 50 $mu$m$times hbox{50} mu$m junctions with various thicknesses of free layer ( $t_{rm F} = 4, 8, 10, 12, 16, 26$ nm) and pinned layer ($t_{rm P} = 1, 2, 6, 8, 9, 12$ nm). The results show that the thicker free layers, the higher PHE signal is observed. In addition, the thicker pinned layers lower PHE signal. The highest PHE sensitivity $S$ of 196 $mu$V/(kA/m) is obtained in the spin-valve configuration with $t_{rm F} = 26$ nm and $t_{bf P} = 1$ nm. The results are discussed in terms of the spin twist as well as to the coherent rotation of the magnetization in the individual ferromagnetic layers. This optimization is rather promising for the spintronic biochip developments.      

Novel Carbon Dioxide Microsensor Based on Tin Oxide Nanomaterial Doped With Copper Oxide

Carbon dioxide $({rm CO}_{2})$ is one of the major indicators of fire and therefore its measurement is very important for low-false-alarm fire detection and emissions monitoring. However, only a limited number of ${rm CO}_{2}$ sensing materials exist due to the high chemical stability of ${rm CO}_{2}$. In this work, a novel ${rm CO}_{2}$ microsensor based on nanocrystalline tin oxide $({rm SnO}_{2})$ doped with copper oxide (CuO) has been successfully demonstrated. The ${rm CuO}hbox{-}{rm SnO}_{2}$ based ${rm CO}_{2}$ microsensors are fabricated by means of microelectromechanical systems technology and sol-gel nanomaterial-synthesis processes. At a doping level of ${rm CuO}:{rm SnO}_{2} =1:8$ (molar ratio), the resistance of the sensor has a linear response to ${rm CO}_{2}$ concentrations for the range of 1% to 4% ${rm CO}_{2}$ in air at 450$^{circ}{rm C}$. This approach has demonstrated the use of ${rm SnO}_{2}$, typically used for the detection of reducing gases, in the detection of an oxidizing gas.      

Thermal Diffusivity and Related Properties of Colossal Magnetoresistive La$_{0.67}$Ca$_{0.33}$MnO $_{3}$ With Various Grain Sizes

Using the open-cell photoacoustic technique, we have measured the room-temperature thermal diffusivities of the colossal magnetoresistive material La$_{0.67}$Ca$_{0.33}$MnO$_{3 }$, sintered between 1100$;^{circ}$ C and 1350$;^{circ}$ C, with average grain sizes 1, 3, 5, and 10 $mu$m. We obtained the thermal diffusivities by analyzing the phase of photoacoustic signals in thermally thick samples using Calderon's method. We found that the insulator-metal transition temperature does not depend on the grain size ($T_{rm IM} sim 272$ K). However, the thermal diffusivity increases with grain size, with values between 0.431 and 0.969 mm $^{2}$s $^{-1}$. Other related electrical and thermal properties, including the electrical conductivity, thermal conductivity, and phonon mean free path, are also dependent on the grain size. The electronic contribution to the thermal conductivity is 2%–3% of the total thermal conductivity for smaller grain sizes (1–5 $mu$m) and increases to about 24% when the grain size is increased to 10 $mu$ m.      

Harmonic Power Standard at NIM and Its Compensation Algorithm

A new harmonic power standard has been developed at the National Institute of Metrology (NIM), Beijing, China, for the calibration of harmonic power analyzers under nonsinusoidal conditions at fundamental frequencies of 50 and 60 Hz. The standard is based on digital sampling techniques that do not require synchronization. A compensation algorithm is presented in this paper. A new definition of the uncertainty for harmonic measurement is proposed that is referred to the fundamental. A characterization signal and its application are introduced. Results have shown that over its operating range of up to 50 A, 500 V, and the sixtieth-order harmonic, the harmonic power standard has uncertainties $(k =2)$ of less than 30 $muhbox{V/V}$, 36 $mu hbox{A/A}$, and 42 $muhbox{W/VA}$ for voltage, current, and power measurements, respectively.      

CMOS Microelectrode Array for Electrochemical Lab-on-a-Chip Applications

Microelectrode arrays (MEAs) offer numerous benefits over macroelectrodes due to their smaller sample size requirement, small form factor, low-power consumption, and higher sensitivity due to increased rates of mass transport. These features make MEAs well suited for microfluidic lab-on-a-chip applications. This paper presents two implementations of MEAs with and without an on chip potentiostat. We first describe an 8$,times,$ 8 array of 6 $mu{rm m}$ circular microelectrodes with center to center 37 $mu{rm m}$ spacing fabricated on silicon using conventional microfabrication techniques. Pads are provided for external connections to a potentiostat for electrochemical analysis. The second implementation is an individually addressable 32$,times,$32 array of 7 $mu{rm m}$ square microelectrodes with 37 $mu{rm m}$ center to center spacing on a CMOS chip with built-in very-large-scale integration potentiostat for electrochemical analysis. The integrated CMOS MEA is post processed at the die level to coat the exposed Al layers with Au. To verify microelectrode array behavior with individual addressability, cyclic voltammetry was performed using a potassium ferricyanide $({rm K} _{3}{rm Fe}({rm CN})_{6})$) solution.      

Microstructure, Electrical, and Magnetic Properties of ZrO$_{2}$ Added MnZn Ferrites

We investigated the influence of ZrO$_{2}$ on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of Mn $_{0.68}$Zn $_{0.25}$Fe $_{2.07}$O $_{4}$ composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350 $^{circ}$C for 4 h in N$_{2}$/O$_{2}$ atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with ZrO$_{2}$ concentration, but excessive ZrO $_{2}$ concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the ZrO$_{2}$ concentration is not more than 0.04 wt% and then decrease with further increase of ZrO$_{2}$ concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of ZrO$_{2}$ concentration.      

Measurements of the Complex Transmission/Reflection Coefficient of a Material Using Mixed-Type Common-Path Heterodyne Interferometery

The dielectric constant, magnetic permeability, and refractive index are the fundamental optical parameters of a material. To investigate these optical parameters, a mixed-type common-path heterodyne interferometer is developed in this paper. By using this interferometer to detect the amplitudes and phases of both the transmission and reflection coefficients, the complex dielectric constant, magnetic permeability, and refractive index can be obtained using the algorithm discussed here. The validity of the mixed-type common-path heterodyne interferometer is demonstrated for visible lights, such as red, green, and blue, using lasers as light sources. Furthermore, the specifications for characterizing the optical properties of samples using the mixed-type common-path heterodyne interferometer are investigated. For example, dielectric constant $varepsilon$ , magnetic permeability $mu$, and the refractive index $n$ of $2.161 + i0.002$ , $0.9997 - i0.0009$, and $1.4699 - i3.4 times 10^{-7}$ with low uncertainties of $0.003 + i0.002$, $0.0003 + i0.0009$, and $0.0007 + i8 times 10^{-8}$, respectively, for a fused quartz measuring 632.8 nm are investigated. It also demonstrated that, in the case of the investigation in visible ranges, the measurement procedure is performed by only the common-path transmission type heterodyne interferometer.      

Development of a High-k Pr $_{2}$O $_{3}$ Sensing Membrane for pH-ISFET Application

In order to develop a pH sensor having a good pH-sensing characteristic, electrolyte-insulator-semiconductor capacitors using a high-k Pr$_{2}$O$_{3}$ thin film as the sensing membrane were fabricated on silicon substrates by reactive radio frequency sputtering. The structural and morphological features of these films with annealing at various temperatures were studied by X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. The Pr$_{2}$O $_{3}$ sensing film after annealing at 900$;^{circ}$C is suggested to the increase in the interfacial SiO $_{2}$ and silicate formation, and the high surface roughness. Therefore, a physical vapor deposition Pr$_{2}$O $_{3}$ film is adopted as a new pH-sensing layer. The result produces a pH response of 52.9 mV/pH $({rm pH}=2hbox{--}12)$, a hysteresis voltage of 17.5 mV $({rm pH}=7 to 4 to 7to 10 to 7)$, and a drift rate of 2.15 mV/h (${rm pH}=7$ buffer solution).      

Novel Built-In Current-Sensor-Based $I_{rm DDQ}$ Testing Scheme for CMOS Integrated Circuits

This paper presents a new built-in current sensor (BICS)-based $I_{rm DDQ}$ testing scheme for complementary metal-oxide semiconductor (CMOS) integrated circuits (ICs). The proposed BICS will employ short detection times and low power dissipation to effectively ensure the reliability of the BICS and reduce the impact of the circuit under test (CUT) during testing. In addition, an $I_{rm DDQ}$ testing scheme based on the proposed BICS for detecting the abnormal quiescent current is presented. A 16-kB CMOS static random access memory (SRAM) is used as the CUT in this paper to discuss the testing considerations, including fault models and the $I_{rm DDQ}$ testing strategy. The simulation results show that the proposed BICS has a much improved performance compared with that in previous works. In addition, the physical chip design of the proposed BICS-based $I_{rm DDQ}$ testing scheme for SRAM testing applications is also implemented using the Taiwan Semiconductor Manufacturing Company (TSMC) 0.18-$mu hbox{m}$ CMOS technology. The test results show that 100% fault coverage can be achieved with only a 1.23% area overhead penalty.      

CMRR in Voltage-Op-Amp-Based Current-Mode Instrumentation Amplifiers (CMIA)

The common-mode rejection ratio (CMRR) of a power-supply current-sensing current-mode instrumentation amplifier (CMIA) has theoretically been analyzed and formulated. The theory was further investigated by doing experiments using $mu$ A741 and TL071 as op-amps and CA3096 transistors as the current mirrors of the CMIA. Both theoretical and practical investigations proved that both the dc and ac performances of CMRR depend on the matching status of parameters such as $hbox{CMRR}$, open-loop gain $A$, gain-bandwidth product $hbox{GB}$, and the output resistance $R_{O}$ of the input op-amps of the CMIA. It has also been shown that, in the CMIA, unlike the voltage-mode instrumentation amplifier, voltage gain is independent of the bandwidth.      

Electromagnetic Forces Acting on the Planar Armature of a Core-Type Synchronous Permanent-Magnet Planar Motor

The core-type synchronous permanent-magnet planar motor (SPMPM) discussed in this paper includes one or more planar armatures each of which contains two sets of three-phase windings named ${rm x}$-winding and ${rm y}$-winding. For each planar armature, a magnetic field energy equation is established first. This equation describes the mechanism of the coupling between the permanent-magnet array, the ${rm x}$-winding and the ${rm y}$ -winding in the core-type SPMPM. By using virtual work principle, ${rm x}$-direction thrust force, ${rm y}$ -direction thrust force and vertical force acting on the planar armature are modeling analytically. For eliminating the coupling in these force models, the excitation flux linkages and phase currents are all transformed into ${rm d}hbox{-}{rm q}$ synchronous reference frame. From the decoupling force equations, some characteristics of the vertical component of force on the planar armature are obtained. The electromagnetic force model is helpful for the design of the contactless planar bearing and the servo control system of the SPMPM.      

Calibration of Rogowski Coils at Power Frequencies Using Digital Sampling

A new high-accuracy system for power-frequency calibration of Rogowski coils is described in this paper. The calibration system is based on nonsynchronous digital sampling. An automated prototype of the calibration system operates at currents of up to 2000 A. A semiautomated system is capable of operating at currents of up to 60 000 A. The best uncertainty $(k = 2)$ of the calibration system is estimated to be better than 50 $muhbox{A/A}$ for magnitude and 50 $muhbox{rad}$ for phase.      

Magnetic Normal Modes in Squared Antidot Array With Circular Holes: A Combined Brillouin Light Scattering and Broadband Ferromagnetic Resonance Study

We present a combined experimental investigation of magnetic normal modes in an antidot lattice using both Brillouin light scattering and broadband ferromagnetic resonance. It was fabricated on a silicon substrate using optical ultraviolet lithography. The sample consisted of a 30-nm-thick ${rm Ni}_{80}{rm Fe}_{20}$ squared antidot array with circular holes whose diameter and edge-to-edge spacing are 250 and 150 nm, respectively. Experiments were performed as a function of the applied magnetic field $mu_{0}{rm H}_{rm ext}$ in the range from $-$100 to 100 mT, with ${rm H}_{rm ext}$ applied along both the square lattice axis and its diagonal. Several peaks were observed in both the Brillouin light scattering and ferromagnetic resonance spectra, and their evolution with the intensity and the direction of the applied field ${rm H}_{rm ext}$ was measured. Micromagnetic simulations enabled us to identify the modes in terms of their symmetry obtaining a good quantitative agreement with the measured frequencies. In addition, we show how the inhomogeneity of the internal field affected the properties of the magnetic eigenmodes and their localization in different regions of the antidot lattice.      

On-Chip Voltage Reference-Based Time-to-Digital Converter for Pulsed Time-of-Flight Laser Radar Measurements

A fully integrated time-to-digital converter (TDC) for a pulsed time-of-flight laser rangefinder has been designed and fabricated by a standard 0.18-$muhbox{m}$ CMOS process. The time-to-digital conversion is realized by counting the full clock cycles of an on-chip ring oscillator between timing signals and by recording the state of its 12 phases at the moment of arrival of the timing signals and their delayed replicas. The frequency of the oscillator is stabilized to an on-chip voltage reference by means of a frequency-to-voltage-converter-based feedback loop. The resolution and single-shot precision (standard deviation) of the TDC are $sim$60 ps and less than $sim$50 ps, respectively, in a range of 80 ns. The worst-case temperature dependence of the TDC is less than 50 $hbox{ppm}/^{circ}hbox{C}$ in the temperature range of 0 $^{circ}hbox{C}$ to 70 $^{circ}hbox{C}$, corresponding to 0.6 $hbox{mm}/^{circ}hbox{C}$ at a distance of 12 m (80 ns). The power consumption of the TDC is less than 18 mW.      

Development of a New Selective Optical Sensor for Cd(II) Ions Based on 4-Hydroxy Salophen

A new sensor membrane based on immobilization of 4-hydroxy salophen on triacetyl cellulose has been developed for the determination of Cd(II) ions that displays excellent performance. The sensing membrane is capable of spectrophotometric determining of Cd(II) with an outstanding high selectivity over a dynamic range between 1.0$,times 10^{-6}$ and 5.0$,times 10^{-2}$ mol L$^{-1}$ with a limit of detection of 5.3 $,times 10^{-7}~$mol L $^{-1}$ (0.06 $mu$g mL $^{-1}$ The sensor shows a fast response time ($≪ {5}~$ min) and the membrane can be used for more than two months without observing any major deviation. The optode revealed very good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor could be used to determine cadmium ions in water and waste water samples. Different experimental parameters such as variable affecting on sensor preparation and pH of the sample solution plus response time were studied. The optodes developed in the present work were found to be stable, cost effective, easy to prepare, and efficient for direct determination of Cd(II) in a variety of aqueous samples using spectrophotometry, with satisfactory results.      

Modeling and Simulation of a Single Tin Dioxide Nanobelt FET for Chemical Sensors

This paper presents the modeling and simulation of a tin dioxide (${rm SnO}_{2}$) field-effect transistor (FET)-based nanobelt gas sensor. The model results are compared to numerical simulations and experimental data obtained from published results describing the fabrication of single crystal nanobelts grown through thermal evaporation techniques. The fabricated sensor shows good response when exposed to oxygen (${rm O} _{2}$) and hydrogen (${rm H} _{2}$) at room temperature. Gas adsorption causes changes in the electrical contacts due to oxygen vacancies in the bulk. As a result, the ${rm I}$ -${rm V}$ characteristics are very different when the device is exposed to (${rm O} _{2}$) versus (${rm H} _{2}$ ). In the presence of ${rm H} _{2}$, the behavior of the contacts is ohmic and saturation is caused by pinch-off of the channel at the drain contact. However, in the presence of ${rm O} _{2}$ , the behavior of the contacts is Schottky, and device saturation occurs at the source end of the device. Our model is based on a depletion mode MOSFET and it accounts for both ohmic and Schottky contacts when the device is exposed to oxygen or hydrogen. It also provides a possible explanation for the gate bias dependence of the saturation current seen in some published characterization data.      

Attenuated Oscillation of the Tunneling Magnetoresistance in a Ferromagnet-Metal-Insulator-Ferromagnet Tunneling Junction

The tunneling magnetoresistance (TMR) ratio is investigated in a ferromagnet-metal-insulator-ferromagnet planar tunneling junction by use of the spin-polarized free-electron model. Due to the coherence multiple reflective scatterings within the metallic layer, the TMR ratio oscillates as the metallic thickness increases. Due to the same scatterings, not only electrons with the out-of-plane energy $E_{xi}$ close to the Fermi energy $E_{F}$ but also electrons with $E_{xi}$ below $E_{F}$ can tunnel sufficiently through the tunneling junction, which leads to the attenuated oscillation of the TMR ratio.