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.      

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.      

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.      

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).      

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.      

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.      

Comparison of a Multichip 10-V Programmable Josephson Voltage Standard System With a Superconductor–Insulator–Superconductor-Based Conventional System

We developed a 10-V dc programmable Josephson voltage standard (PJVS) using a multichip technique. The PJVS was based on $hbox{NbN/TiN}_{x}/hbox{NbN}$ junctions and operated using a 10-K compact cryocooler. We carried out an indirect comparison with a superconductor–insulator–superconductor-based conventional Josephson voltage standard (JVS) by measuring the voltage of a 10-V zener diode reference standard. The combined standard uncertainty of the comparison was $u_{c} = 0.03 muhbox{V}(k = 1)$, and the relative combined standard uncertainty was $3 times 10^{-9}$.      

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.      

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.      

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.      

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.      

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.      

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.      

Smooth Contact Capacitive Pressure Sensors in Touch- and Peeling-Mode Operation

Capacitive (C) pressure sensors typically sense quadratic changes in $C$ as a pressure difference $(P)$ deflects a flexible conducting diaphragm near a rigid ground plane. Touch-mode capacitive pressure (C-P) sensors, where the conducting diaphragm touches a dielectric coated ground plane, often show a more linear response, but with less sensitivity, particularly at low-$P$ . Initial contact of the diaphragm often occurs at a critical $P$. Until $P_{rm crit}$ is reached, the sensitivity is typically too low for accurate measurements. In this work, two different types of electrodes with “parabolic” and “donut” cavity-shapes have been designed, fabricated, and tested to achieve high-sensitivity at low-pressures. A flexible conducting diaphragm touches the bottom electrode smoothly, and both cavity shapes permit initial contact at a zero-pressure differential. This type of C-P sensors can have touch-mode and peeling-mode operations. The sensitivities of these sensors in two operation modes were measured, and their resolutions were smaller than 0.1 Pa at a mean pressure of ${10} ^{5}~{rm Pa}$. Both sensors in two modes have the resolution over total-pressure less than ${10} ^{-6}$, which is difficult to achieve at atmospheric pressure.      

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.      

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.      

Electrical Transport in a Semimetal–Semiconductor Nanocomposite

Measurements are presented on the low-field electrical conductivity and moderate-field current–voltage characteristics in a nanocomposite structure of ErAs particles in an $hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ host with Be compensation. The electrical conductivity displays strong temperature dependence with two types of transport mechanisms. At ${sim}hbox{205}$ K and above, the low-field conductivity appears to be dominated by free electrons in $hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$. Between 55 and 205 K, the conductivity is well explained by variable-range hopping, $sigma = A exp(-B/T^{1/4}$), via Mott's law. The transport displays a soft breakdown effect at moderate bias fields that grows in threshold field with decreasing temperature. This is attributed to impact ionization of the Be dopants.      

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.      

A Phototransistor-Based High-Sensitivity Biosensing System Using 650-nm Light

A miniature optical biosensing system based on a PMOS phototransistor and absorption photometry is proposed. The phototransistor was manufactured in a standard 0.35-$mu{rm m}$ CMOS process, and it exhibited a responsivity higher than 1000 A/W for 650-nm light. For biochemical applications, the ${rm TMB/H}_{2}{rm O}_{2}/{rm HRP}$ method was adopted as a useful basis in our system. A sample volume of only 10 $mu{rm l}$ was required to be dropped on the slide above the phototransistor. Experimental results demonstrated that a high sensitivity of 2.5 $mu{rm A/pM}$ was achieved, and the minimum HRP concentration successfully detected was 2.7 pM. This detection limit is three orders of magnitude better than that of a lately reported silicon biosensor, and is even comparable to that of a commercial spectrophotometer.