Structure and Magnetic Properties of Sn$_{1 - {rm x}}$ Co$_{rm x}$ O$_{2}$ Powder and Film

We have studied room-temperature ferromagnetism (RTFM) in Sn$_{1 - {rm x}}$Co$_{rm x}$O$_{2}$ powders and films fabricated by the sol-gel method. Our X-ray diffraction, high-resolution transmission microscopy, and X-ray photoelectron spectroscopy results show that all the samples have a pure rutile structure, and Co ions have a chemical valence of 2+. In addition, the magnetic moment per Co ion drops rapidly with the increase of Co content. Interestingly, Sn $_{1 - {rm x}}$Co $_{rm x}$O $_{2}$ films spin-coated on a Si (111) substrate have much larger magnetic moment than powder samples, because film samples have larger domain volumes, which may induce stronger long-range magnetic exchange coupling.      

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).      

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.      

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.      

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.      

Domain Structure in (NiFe/Au/Co/Au)$_{10}$ Multilayers With Perpendicular Anisotropy of Co Layers

Results of domain structures observation of individual Ni $_{80}$Fe $_{20}$ and Co sublayers in sputter deposited (NiFe/Au/Co/Au)$_{10}$ multilayers, using an element-sensitive method: the photoemission electron microscopy combined with soft X-ray magnetic circular dichroism, are presented. Also, overall domain structures were studied with magnetic force microscopy. The studies allowed us to reveal submicron stripe domains in the investigated samples and the replication of the stripe domains from the Co layers with perpendicular anisotropy to the NiFe layers with easy-plane anisotropy.      

Correlation Between the Degradation of Perpendicular Anisotropy and the Double Hysteresis Behavior in [Pd/Co]$_{rm n}$/FeMn Exchange Biased Thin Films

We clearly detected double hysteresis by increasing Co layer thickness and decreasing the number of bilayers in perpendicular exchange biased [Pd(0.6)/Co$(t)$] $_{rm n}$/FeMn(11.6 nm) thin films. In-plane tensile stress calculations confirmed that the appearance of double hysteresis is closely related to the degradation of stress-induced perpendicular anisotropy in the [Pd/Co] multilayers. Furthermore, annealing at the magnetic field applied perpendicular to the film plane directly verified that the enhancement of thermally induced perpendicular anisotropy, $K_{rm eff-induced}$, in the [Pd/Co] multilayers is the main physical reason for removal of the double hysteresis. All our experimental and theoretical results demonstrated that perpendicular anisotropy is the dominant factor in controlling the double hysteresis behavior of perpendicularly magnetized [Pd/Co]$_{rm n}$/FeMn exchange biased thin films.      

Bit Storage by 360 $^{circ}$ Domain Walls in Ferromagnetic Nanorings

We propose a theoretical design for a magnetic memory cell, based on thin-film ferromagnetic nanorings, that can efficiently store, record, and read out information. An information bit is represented by the polarity of a stable 360$^{circ}$ domain wall introduced into the ring. Switching between the two magnetization states is done by a current applied to a wire passing through the ring, whereby the 360$^{circ}$ domain wall splits into two charged 180 $^{circ}$ walls, which then move to the opposite extreme of the ring to recombine into a 360 $^{circ}$ wall of the opposite polarity.      

Planar Optical Waveguide Evanescent Wave ${rm CO}_{2}$ Sensor Based on a Clad of Alstonia Scholaris Leaf Extract

An evanescent wave biosensor is designed and developed using a single mode planar optical waveguide based on a spin coated clad of leaf extract of Alstonia Scholaris. The fabricated sensor showed ${rm CO}_{2}$ concentration dependent response. The specialty of this sensor is that it can be used when stored at room temperature (25$~^{circ}{rm C}$) up to a maximum of 25–30 days with 90% retention of original sensitivity. These ${rm CO}_{2}$ sensing biochips showed good operational efficiency for 10 cycles. The planar optical waveguide is versatile, easy to fabricate and can be used for ppm level ${rm CO}_{2}$ measurement with good sensitivity. Cross sensitivity with respect to humidity is studied. The sensor exhibited a short response time of 4–5 s and recovery time of 25 s with good repeatability and reproducibility.      

Comparison of the ${mbi A}^{*}{-}{mbi A}$ and ${mbi T}, Phi{-}Phi$ Formulations for the 2-D Analysis of Solid-Rotor Induction Machines

We present two eddy-current field potential formulations to solve rotating electrical machine problems by applying the finite-element method (FEM) using the motional ${mbi A}^{*}{-}{mbi A}$-potential formulation and the motional ${mbi T}, {bf Phi}{-}{bf Phi}$-potential formulation. We use the single-phase and three-phase solid-rotor induction motors of Problem No. 30a of TEAM Workshops to compare the potential formulations. We have solved both problems in the time domain and the frequency domain.      

A Fiber-Optic Sensor for Monitoring Trace Ammonia in High-Temperature Gas Samples With a ${hbox{CuCl}}_{2}$-Doped Porous Silica Optical Fiber as a Transducer

An optical fiber chemical sensor for detecting/monitoring trace ammonia in high-temperature gas streams has been developed. This sensor uses a ${hbox{CuCl}}_{2}$-doped porous silica optical fiber, prepared via a previously reported sol-gel process, as a transducer. Trace ammonia in a gas sample diffuses into the porous fiber to react with the doped agent to form a ${hbox{Cu}}^{2+}$-ammonia complex. The concentration of the ${hbox{Cu}}^{2+}$ -ammonia complex inside the porous silica optical fiber is proportional to ammonia concentration in the gas sample, to which the sensing porous silica fiber is exposed. Therefore, ammonia concentration in the gas sample can be detected through detecting the optical absorption signal of the formed ${hbox{Cu}}^{2+}$-ammonia complex inside the fiber by using a fiber-optic UV/Vis absorption spectrometric method. This sensor can be used to reversibly monitor trace ammonia in a gas sample at an elevated temperature up to 450 $^{circ}$C in the tested range. A detection limit of 0.24 ppmv ammonia in an air gas sample was achieved when the sensor was tested at a temperature of 450 $^{circ}$ C.      

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.      

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.      

SiGe/Si Quantum-Dot Infrared Photodetectors With ${bm delta}$ Doping

The multicolor absorption of MOS SiGe/Si quantum-dot (QD) infrared photodetectors is demonstrated using the boron $delta$-doping in Si spacers. The energy-dispersive X-ray spectroscopy shows that the Ge concentration in the wetting layers is much smaller than that in QDs. Most holes stay at the ground state in QDs instead of wetting layers. The energy band structure in QDs is calculated to understand the absorption spectrum. The absorption at 3.7–6 $mu$m is due to the intersubband transition in the SiGe QDs. The other absorption at 6–16 $mu$ m mainly comes from the intraband transition in the boron $delta$ -doping wells. Since the broadband spectrum covers most of the atmospheric transmission windows for infrared, the broadband detection is feasible using this device.      

Fabrication and Application of Ruthenium-Doped Titanium Dioxide Films as Electrode Material for Ion-Sensitive Extended-Gate FETs

A novel ruthenium-doped titanium dioxide (TiO $_{2}$: Ru) film for pH detection is based on an ion-sensitive extended gate field effect transistor (ISEGFET) sensor. For the preparation of the TiO$_{2}$ : Ru sensing film, a specific processing for metal modification of TiO$_{2}$ thin film is deposited by a co-sputtering system. After thermal annealing treatment, material analysis of the sensing layer is measured by SEM, Hall measurement system and electrical detection system. The average sensitivity of TiO$_{2}$: Ru for hydrogen ion detection is about 55.20 mV/pH (concentration range between pH1 and pH13). The effect of long-term drift for TiO$_{2}$ : Ru ISEGFET-based sensor is presented. Drift rate of the sensor for pH is 0.745 mV/h for 12 h. In order to prepare the calcium ion sensor, the sensing membrane of polymer materials is based on TiO $_{2}$: Ru ISEGFET-based sensor by physical adsorption. The average sensitivity of the calcium ion sensor in the concentration ranging between 1 M and 1$,times,$ 10$^{-3}$ M CaCl$_{2}$ is about 29.65 mV/pCa.      

A Vibration-Based PMN-PT Energy Harvester

We report design, modeling, analysis, and experimental study of a vibration-based piezoelectric energy harvester. The energy harvester is made of a composite cantilever of a single crystal relaxor ferroelectric material, $(1-x)$Pb(Mg $_{1/3}$Nb $_{2/3}$)O $_{3-x}$PbTiO $_3$ (PMN-PT), and a polydimethylsiloxane (PDMS) base layer. A PDMS proof mass is constructed at the tip of the composite cantilever beam and is used as a means to tune the system natural frequency. The use of the PMN-PT piezoelectric material and an interdigited electrodes (IDEs) design improves the energy conversion efficiency. A dynamic systems modeling approach is employed to analyze the responses and the performance of the harvester design. We have demonstrated that a prototype of the harvester with a size of 7.4 mm $,times,$2 mm $,times,$110 $mu$m outputs a voltage of 10 V (0.3 mW power) under a vibration excitation with a peak-to-peak amplitude of 1 mm at a frequency around 1.3 kHz. Based on the experimental results, the power density prediction of the proposed harvester design shows a superior performance than that of the other reported piezoelectric harvesters.      

Room-Temperature Ferromagnetic Property in MnTe Semiconductor Thin Film Grown by Molecular Beam Epitaxy

MnTe layers of high crystalline quality were successfully grown on Si(111) and Al$_{2}$O$_{3}$(0001) substrates by molecular beam epitaxy. We have investigated the structure, magnetic and electric transport properties of MnTe layers by using X-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometer, physical properties measurement system (PPMS), and X-ray photoelectron spectroscopy (XPS). Characterization of MnTe layers on Si(111) and Al $_{2}$O $_{3}$(0001) substrates by X-ray diffraction (XRD) revealed a hexagonal structure of polycrystalline growth for MnTe/Si(111) and epitaxial growth for MnTe/Al$_{2}$ O$_{3}$ (0001), respectively. Investigation of magnetic properties for MnTe layers showed ferromagnetic properties above room temperature unlike antiferromagnetic bulk MnTe materials. The great irreversibility between zero-field-cooling and field-cooling magnetization were observed. Apparent ferromagnetic hysteresis loops are measured at room temperature. In electro-transport measurements, the temperature dependence of resistivity revealed a noticeable semiconducting behaviors and showed a conduction via variable range hopping (VRH) at low temperature. From XPS results, we assume that the origin of ferromagnetism in samples may be due to the breaking of superexchange antiferromagnetic correlations between Mn spin moments arising from Tellurium vacancies.      

A Very Low Offset Preamplifier for Voltage Measurements in the $muhbox{V}$ Range

A new topology for the implementation of a very low offset voltage preamplifier is presented. The new topology employs a time-varying resistance as a probe for detecting the sign and magnitude of the equivalent input offset of an operational amplifier in a series-shunt feedback configuration and allows for continuously correcting the offset voltage by means of a proper control feedback. The most remarkable feature of the approach we propose is the fact that the offset correction can continuously be performed with the signal voltage source connected to the circuit, as its presence and magnitude do not affect the offset detection circuit. At the same time, the offset cancellation circuit has minimum effect on the output voltage of the preamplifier in the bandwidth of the signal. An actual low-offset preamplifier based on the new approach we propose has been built and tested. While employing a metal–oxide–semiconductor field-effect transistor (MOSFET) input operational amplifier with a typical input offset of 100 $muhbox{V}$ (600- $muhbox{V}$ maximum), a voltage preamplifier with a gain of 201 and an equivalent input offset voltage below 100 nV is consistently obtained, which is independent, by design, of the temperature. While characterized by these excellent performances, the system employs quite standard low-cost components and does not require any calibration procedure.      

High Permeability and Low Loss Ni–Fe Composite Material for High-Frequency Applications

A magnetic material with high permeability and low loss characteristics at high frequency is required for miniaturizing electronic components such as antennas. The key factors to keeping low magnetic loss are a high magnetic resonance frequency and the suppression of the eddy currents. We have fabricated a low-loss magnetic composite material by dispersing Ni $_{78}$Fe $_{22}$ (permalloy) fine flakes in polymers; the thickness of the flakes was less than skin depth. The magnetic loss decreased with increased stirring time, and the minimum value occurred when the agglomerated particles decreased and most of the particles were deformed into flakes. Moreover, Zn$_{5}$Ni$_{75}$Fe$_{20}$ composite material indicated high permeability when the flakes were oriented in the direction of sheets. The effect of wavelength shortening by permeability enhancement and the low loss characteristic were confirmed by experimental results of a rod antenna loaded with the developed magnetic composite material.      

Design and Characterization of a Sampling System Based on $Sigma$–$Delta$ Analog-to-Digital Converters for Electrical Metrology

This paper describes a sampling system designed using a commercial sigma–delta analog-to-digital converter ($Sigma$–$ Delta$ ADC). In addition to characterization measurements using a conventional high-quality signal generator, a Josephson waveform synthesizer that provides ultimately noise- and drift-free voltages was used. To evaluate the suitability of this sampling system as part of a transfer power standard, additional comparisons of the root-mean-square (RMS) values measured were performed against a thermal converter and the primary power sampling standard at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. Initial analysis of the measurement data shows an effective resolution in the range of 18–19 bits at an equivalent sampling rate of 64 kHz. The integral nonlinearity error of the system was measured to be within $pm 7 mu hbox{V/V}$ or one least significant bit at this resolution.