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.      

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).      

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.      

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.      

Establishment of All Digital Closed-Loop Interferometric Fiber-Optic Gyroscope and Scale Factor Comparison for Open-Loop and All Digital Closed-Loop Configurations

This paper covers the design details of an all digital closed-loop interferometric fiber-optic gyroscope (ADCL-IFOG) prototype, constructed in TUBITAK UME, and scale factor comparison between open-loop and ADCL-IFOG prototypes with sine wave biasing modulation. The output of demodulation circuit, proportional to the applied rotation rate, was sampled by AD7714YN analog-to-digital converter (ADC), operated in 16 bit resolution. Error voltage, generated by microcomputer – controlled LTC 1667CG, 14 bit digital to analog converter (DAC), was sent to the phase modulator through a linear summing circuit to make Sagnac Phase Shift zero, depending on the rotation direction. For this implementation, the ultimate rotation rate of 1.84 ($^{circ}/{hbox{h}}$ ) was nullified. The averaged sensitivity of the proposed closed-loop IFOG in unit of error voltage applied to the phase modulator was determined as 132.65 $mu hbox{V}/(^{circ}/{hbox{h}}$ ). The scale factors of both the open-loop and ADCL-IFOG prototypes were compared in a range of 1–15270 ( $^{circ}/hbox{h}$) rotation rate, corresponding to Sagnac Phase Shifts varying from 0.00115 ( $^{circ}$) to 17.57448 ( $^{circ}$). The maximum peak to peak noise and the bias stability of ADCL-IFOG prototype were determined as 4.97 ($^{circ}/hbox{h}$ ) and 1.48 ($^{circ}/hbox{h}$ ) at 23.0$~^{circ}hbox{C}$ , respectively.      

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.      

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.      

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.      

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.      

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.      

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.      

Proposal of a Novel Pole Type Structures in Perpendicular MRAM for High Gb/Chip

This paper proposes a novel MRAM using perpendicular magnetic tunnel junction device for high capacity. Conventional MRAM has weak points to realize high capacity in the design structure of the cell, one of which is that using simple current injection system can generate only weak switching field. As a solution, we propose a novel MRAM that has two additional poles in this paper. Proposed novel MRAM has a strong switching field owing to two poles added on both sides of the free layer, just like perpendicular magnetic recording heads. In this paper, analysis of the switching field and useful designs for high Gb/Chip are presented. This research was done using three dimensional FEM with injected current density of $8times 10^{7}$ A/cm$^{2}$ –$6times 10^{8}$ A/cm$^{2}$ .      

A Single-Chip CMOS Smoke and Temperature Sensor for an Intelligent Fire Detector

A single-chip CMOS smoke and temperature sensor for use as an intelligent fire detector is proposed. The proposed smoke sensor measures smoke density based on the light-scattering method. The temperature sensor is integrated with the smoke sensor not only to sense heat from a fire but also to compensate for the temperature dependency of the smoke sensor. The prototype chip includes an on-chip photodiode (PD), pixel circuit, correlated double sampling (CDS) circuit, and analog-to-digital converter (ADC). The prototype chip was fabricated using a 0.35-$mu$ m CMOS process and was placed inside the smoke detection chamber, while the thermistor for the temperature sensor is placed outside the chamber. The measurement results show $pm$ 1% smoke detection accuracy over the range 4% $sim$ 25% and $pm 1~^{circ}hbox{C}$ temperature-sensing accuracy over the range $25~^{circ}hbox{C}sim 95~^{circ}hbox{C}$. The power consumption of the prototype chip is 220 nW, excluding the infrared light-emitting diode (IR LED).      

Fully Packaged Nonenzymatic Glucose Microsensors With Nanoporous Platinum Electrodes for Anti-Fouling

CMOS integrable nonenzymatic glucose microsensors with nanoporous platinum (Pt) working and counter electrode (WE/CE) were first fabricated, packaged, and characterized with biocompatible Nafion and hydrophilic polyurethane (HPU) membrane materials. Optimal packaging material and its processing condition for these nonenzymatic sensors were investigated. The optimally packaged glucose microsensor was evaluated in human blood plasma solution for checking its biocompatibility and commercial applicability. The fabricated microsensors with nanoporous Pt WE/CE had a sensitivity of 7.75 $mu$A mM $^{-1}$ cm $^{- 2}$. The packaged microsensor with Nafion membrane had better performance characteristics than packaged one with HPU. The packaged microsensor with 1:6 ratio of Nafion to ethanol exhibited a sensitivity of 0.83 $mu$ A mM$^{- 1}$ cm$^{-2}$ and stable current change in the human blood plasma solution, while the current response of nonpackaged microsensor was rapidly saturated because adsorption of various proteins and cells as expected. These data indicate that the packaged nonenzymatic microsensor with biocompatible Nafion membrane is promising and strongly applicable for in vitro and in vivo glucose monitoring systems.      

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.      

Full Wheatstone Bridge Spin-Valve Based Sensors for IC Currents Monitoring

Full Wheatstone bridge spin-valve-based electrical current sensors at the IC level are presented. Prototypes with different geometrical parameters have been designed, fabricated and fully characterized. DC characterization has been carried out, for measurement of insertion losses, linearity, voltage offset and sensitivity. Current ranges from 10 $mu{rm A}$ to 100 mA can be covered with these sensors with excellent linearity and sensitivities above 1 ${rm mV}/({rm V}cdot{rm mA})$ . AC characteristics have also been analyzed and bandwidths exceeding 100 kHz are demonstrated. Moreover, the temperature coefficients have been extracted in the range of $-20^{circ}{rm C}$ to $+60^{circ}{rm C}$. In order to highlight the design properties, dependence of the sensor's performance with external magnetic perturbations and self-heating have also been measured and quantified. The associated errors are in the range of 1%–2% of the full scale.      

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.      

Giant Magnetoimpedance Current Sensor With Spiral Structure Double-Probe

A novel giant magnetoimpedance (GMI) noncontact current sensor with spiral structure double-probe is designed. Differing from the formerly reported sensors, the probes of this sensor consist of annealed commercial amorphous ribbons which are curled to spiral tubes. Two couples of permanent magnets are applied to provide bias magnetic field. The distance between the probes and the permanent magnets is fixed at 2.4 cm. The sensor shows sensitivity of 1 V/A in the current range of $pm$ 1.5 A, measurement precision of less than 0.16% at room temperature, and good thermal stability in the temperature range between $-$20 and 30 $;^{circ}{rm C}$.      

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.