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.      

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.      

High Bulk Spin Scattering Asymmetry in CPP Spin Valves With Alternated Monatomic $[hbox{Fe/Co}]_{rm n}$ Superlattice

We confirmed the structural properties of trilayered epitaxial films with AML [Fe/Co]_n and Au spacer on Au electrode by RHEED and TEM. A considerably large DeltaRA (2.61 mOmegamum²) resistance area product was observed in all metallic current perpendicular-to-plane giant magneto-resistance (CPP-GMR) spin-valve elements by using alternate monatomic epitaxial [Fe/Co]_n ferromagnetic layer with IrMn layer on the top. The estimated spin scattering asymmetry coefficient beta and interface asymmetry coefficient gamma was 0.81 and 0.43 plusmn 0.05, respectively. This value of beta is higher than that of Fe₅₀Co₅₀/Cu laminated with Cu spacer or Heusler alloy which is largest value ever reported at room temperature.     

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.      

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.      

Structural Stability and Magnetic Properties of the TbCu$_{7}$ -Type SmCo$_{x - 0.4}$Ti$_{0.4} (x = 5.0hbox{–}8.5)$ Alloys

We have studied the composition dependence, thermal stability, long-term stability at 500°C, and magnetic properties of the nanostructural TbCu₇-type (1:7) Sm-Co-Ti alloys. We prepared the SmCox-0.4Ti_0.4 alloys with a wide composition range from x = 5.0 to x = 8.5 by high-energy ball-milling, followed by annealing at 700-1100°C for 2 h. After annealing at 700°C, the powders with x = 7.0-8.5 showed a single 1:7 structure, while the powders with x = 5.0-6.5 presented the 1:7 plus CaCu₅-type (1:5) structure. At an annealing temperature higher than 800°C, a minor Th₂Zn₁₇-type (2:17) phase precipitated in the matrix of the 1:7 phase. Intrinsic coercivity iHc exhibits a maximum of 2.3 T at room temperature and 0.4 T at 500°C in the x = 7.0 samples annealed at 700°C. The temperature coefficient of iHc seems stable as the Sm/Co ratio changes from 1/6.5 to 1/7.5. The coercivity decreased with increasing annealing temperature Ta, from 2.3 T at Ta = 700°C to 1.3 T at Ta = 1100°C, which is mainly attributed to the grain growth from 35 nm for Ta = 700°C to 1 ?m for Ta = 1100°C. After holding at 500°C for up to 360 h, the microstructure and magnetic properties of the 1:7-type nanograin alloys remained almost unchanged, indicating a structurally and magnetically long-term stabilization at the potential high-temperature application environment.     

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.      

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.      

Electric Field Sensing Scheme Based on Matched $ hbox{LiNbO}_{3}$ Electro-Optic Retarders

In this paper, a wideband-electric-field-sensing scheme that uses optically matched integrated optics electrooptic devices and coherence modulation of light is described. In a coherence modulation scheme, the integrated optics sensor detects the electric field and imprints it around an optical delay. The optical delay is generated by a birefringent optical waveguide in a lithium niobate (LiNbO₃) integrated optics two-wave interferometer. The modulated optical delay, acting as an information carrier, is transmitted through an optical fiber channel. At the receiver, light is demodulated by a second integrated optics two-wave interferometer, which also introduces a second optical delay. The optical delays on the sensor and demodulator are matched at the same value. The integrated optics demodulator measures the autocorrelation of light around the optical delay value, and the imprinted electric field is recuperated as a linear variation of the received optical power. The matching of the sensor and demodulator allows a direct detection of the electric field, giving a unique feature to this fiber-integrated optics scheme. The experimental setup described here uses two pigtailed LiNbO₃ electrooptic crystals: one acting as the electric field sensor and the other acting as the optical demodulator. The wideband sensing range on the experimental setup corresponds to frequencies between 0 and 20 kHz.     

Improvement of Electrical Properties of $hbox{Ba}_{{bf 0.7}}hbox{Sr}_{bf 0.3}hbox{TiO}_{bf 3}$ Capacitors With an Inserted Nano-Cr Interlayer

The metal–insulator–metal (MIM) capacitors were prepared with $hbox{Ba}_{0.7}hbox{Sr}_{0.3}hbox{TiO}_{3}hbox{/Cr/Ba}_{0.7}hbox{Sr}_{0.3}hbox{TiO}_{3}$ (BST/Cr/BST) dielectric and Pt electrode. The multilayer BST/Cr/BST was sputtered onto $hbox{Pt/Ti/SiO}_{2}hbox{/Si}$ substrate. The presence of nano-Cr interlayer affects the electrical properties of the capacitors. The temperature coefficient of capacitance (TCC) of capacitors with 2 nm Cr is about 69% of that of capacitors without Cr. In a previous work, the formation of the $hbox{TiO}_{2}$ secondary phase was found after the BST/Cr/BST dielectrics were annealed at 1023 K in $hbox{O}_{2}$ atmosphere for 1 h. It is suggested that the nano-Cr interlayer as a catalyst leads to the $hbox{TiO}_{2}$ formation during the annealing in $hbox{O}_{2}$ atmosphere. The negative value of TCC of BST can be compensated by the positive TCC of $hbox{TiO}_{2}$, and the temperature stability in the dielectric constant can be realized for capacitors with nano-Cr interlayer. The voltage stability of BST is also improved with the insertion of nano-Cr interlayer, and the quadratic coefficient in voltage coefficient of capacitance (VCC) of Pt/BST/Cr(2 nm)/BST/Pt is about 30% of that of the BST capacitor without Cr. The effects of Cr thickness on TCC, VCC, dissipation factor, and leakage current density of Pt/BST/Cr/BST/Pt parallel plate capacitors are investigated.      

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.      

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.      

Raman Studies of ${rm Ti}_{bm{ 1-x}} {rm Fe}_{bm x} {rm O}_{bm 2}$ Nanoparticles

Ti_1-xFe_xO₂ (x = 0.00-0.13) nanoparticle samples were prepared by hydrolysis method. We investigated the effects of Fe doping on the structural and magnetic properties of the Ti_1-xFe_xO₂ nanoparticle system. Scanning electron microscopy and X-ray diffraction measurements confirm that the particle size of the powder is in nanoscale, and that the magnetic Fe impurities substitute for the Ti sites in the anatase TiO₂ phase. All the samples with x > 0 were found to be super-paramagnetic at room temperature by magnetization measurements. Raman spectra also strongly support that the Fe atoms go into the Ti-site in theTiO₂ structure. For comparison, ceramic Ti_1-xFe_xO₂ samples were also prepared by usual ceramic method. Ferromagnetism was observed only in the ceramic Ti_1-xFe_xO₂ system. Additional Raman peak at around 610 cm^-1 is observed only in the ceramic samples. This may be related to the clusters created by mixture of various valence state of Fe, which probably would be the cause for ferromagnetism observed in the ceramic Ti_1-xFe_xO₂ system.     

$hbox{Mg}_{1-{rm x}}hbox{Co}_{rm x}hbox{Fe}_{1.98}hbox{O}_{4}$ Ceramics With Promising Magnetodielectric Properties for Antenna Miniaturization

We have studied the effects of concentration of cobalt and sintering temperature on the complex relative permittivity and permeability of MgFe_1.98O₄ ferrite ceramics. All samples were doped with 3 wt% Bi₂O₃ to improve the sintering properties of the Mg_1-xCo_xFe_1.98O₄ ceramics and thus attain a low dielectric loss tangent. X-ray diffraction data indicated that the ferrite samples all have a single-phase spinel structure and that there was no reaction between the ferrite and Bi₂O₃. In terms of microstructure development and grain growth, the effect of Bi₂O₃ is much more pronounced than that of Co. At a given concentration of Co, the magnetic properties can be fairly explained by a magnetic circuit model. The relationship between static permeability and the concentration of Co can be understood by using the single-ion model combined with the local uniaxial anisotropic model. Among the samples we prepared, Mg_0.96Co_0.04Fe_1.98O₄ sintered at 1000degC for 2 h has almost equal real permeability and permittivity-both approximately 10 - as well as sufficiently low dielectric and magnetic loss tangent over a range 3 to 30 MHz [the high-frequency (HF) band]. These properties that should be useful for miniaturization of HF antennas.     

Characterization of the Temperature Dependence of the Piezoresistive Coefficients of Silicon From ${-}150,^{circ}$C to ${+}125,^{circ}$C

Stress sensing test chips are widely utilized to investigate integrated circuit die stresses arising from assembly and packaging operations. In order to utilize these test chips to measure stresses over a wide range of temperatures, one must have values of six piezoresistive coefficients for n- and p-type silicon over the temperature range of interest. However, the literature provides limited data over the desired range, and even the data at room temperature exhibit wide discrepancies in magnitude as well as sign. Thus, this work focuses on an extensive experimental study of the temperature dependence of the fundamental piezoresistive coefficients, pi₁₁, pi₁₂, and pi₄₄, for both p- and n-type silicon from -150degC to +125degC, as well as a number of useful combined coefficients. Measurements were performed using stress sensors fabricated on (001) silicon. In order to minimize errors associated with misalignment with the crystallographic axes on (001) silicon wafers, anisotropic wet etching was used to accurately locate the axes. Four-point bending (4PB) was used to generate the required stress in strip-on-beam samples, and finite-element simulations were used to determine the states of stress in the silicon material.     

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.      

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.      

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.