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Excess heat capacity in a bolometric detector has the consequence of increasing or leading to multiple device time constants.  The Mo/Au bilayer transition edge sensor (TES) bolometric detectors initially fabricated for the high resolution mid-infrared spectrometer (HIRMES) exhibited two response thermalization scales, one of which is a few times longer than estimates based upon the properties of the bulk materials employed in the design. The relative contribution of this settling time to the overall time response of the detectors is roughly proportional to the pixel area, which ranges between ∼0.3 and 2.6 mm2.  Use of laser ablation to remove sections of the silicon membranes comprising the pixels results in a detector response with a smaller contribution from the secondary time constant.  Additional information about the nature of this excess heat capacity is gleaned from glancing incidence X-ray diffraction, which reveals the presence of molybdenum silicides near the silicon surface which is a consequence of the bi-layer deposition.  Quantitative analysis of the concentration of excess molybdenum, estimated with secondary ion mass spectroscopy, is commensurate to the additional heat capacity needed to explain the anomalous time response of the detectors. [ABSTRACT FROM AUTHOR]

This article describes a simple though extremely effective sensor for acetone monitoring in the breath. The sensor is capable of monitoring the presence of acetone at parts per million (ppm) concentrations, thus being suitable for a diabetes diagnosis. It has a dimension of $3 {\,\,\mathrm {mm}} \times 6 {\,\,\mathrm {mm}}$ and a cost of less than one dollar. The small dimensions allow one to greatly limit the power required to increase its temperature, and its high selectivity with respect to other gases present in the breath reduces the risk of false-positive responses. The sensor is based on a thin alumina substrate on which platinum strips are deposited on both faces. A thin Nb2O5 layer with a nanometric thickness provides the required sensitivity and selectivity. Sensor prototypes have been characterized by field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) and proved an inherent linear response up to a few ppm of acetone. [ABSTRACT FROM AUTHOR]

This paper discloses two high-sensitivity probes for Eddy Current Nondestructive Test (NDT) of buried and surface defects. These probes incorporate eight and 32 magnetoresistive sensors, respectively, which are optimized for high sensitivity and spatial resolution. The signal processing and interfacing are carried out by a full-custom application-specific integrated circuit (ASIC). The ASIC signal chain performs with a thermal input-referred noise of 30 nV/ $\sqrt{\text{Hz}}$ at 1 kHz, with 66 mW of power consumption, in a die with 3.7×3.4 mm $^2$. NDT results are presented, showing that there is an increase in spatial resolution of surface defects when contrasted to prior art, enabling the probes to resolve defects with diameters of 0.44 mm, pitches of 0.6 mm, and minimum edge distance as low as 0.16 mm. The results also show that the probe for buried defects is a good all-round tool for detection of defects under cladding and multiple-plate flat junctions. [ABSTRACT FROM AUTHOR]

A kirigami-based strategy was investigated for strain transduction, using serpentine gold traces embedded in thin-film Parylene C. Multiple kirigami slit designs were evaluated via COMSOL simulation and mechanical force testing; sensors having tightly packed slits stretched up to 17.5 mm (350% strain) before mechanical failure and 9 mm (180% strain) before electrical failure. Strain transduction was achieved by monitoring DC resistance changes during stretching. DC resistance linearly increased with strain, with sensitivities up to 0.16 $\Omega$ /mm (gauge factor = 0.007) and minimal hysteresis. High-frequency trace impedance and inter-trace capacitance were also investigated during strain cycling. Capacitance increased with strain and high-frequency impedance show a nonlinear strain relationship. The biocompatible construction and extremely low profiles (20 $\mu \text{m}$ thick) of these sensors are attractive for minimally invasivein vivostrain sensing applications. [2018-0130] [ABSTRACT FROM AUTHOR]

Superconducting titanium thin films are good candidates for transition edge sensors. In this paper, we deposit titanium thin films on cooled silicon-on-insulator substrates by using electron-beam evaporation. The deposition rate dependence of the film stress, resistivity, and superconducting transition temperature are presented and analyzed. The relationship between film electrical properties and thickness is discussed. For investigating the heating influence on thin Ti films, a depth profile of oxygen diffusion in the films is also analyzed by X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

We report on investigation of the mechanical properties of paper electronics (printed and made out of paper). One key objective of such paper electronics is to achieve ultraflexibility. Therefore, it is important to understand electrical functionality and reliability of paper electronics under various physical (mechanical) deformations. Here, we show the general mechanical properties of the cellulose paper used and its electrical behavior under applied strain, tackling the main effects that need to be identified when building paper-based systems, from product performance and stability perspective. An overview of the stress–strain behavior of silver ink on paper is discussed, and then, we tackle a more specific analysis of the performance variations of paper sensors made with recyclable household materials when exposed to various mechanical conditions of tensile and compressive bending. This paper is important for developing stable wearable sensors for incorporation into Internet of Everything applications. [ABSTRACT FROM PUBLISHER]

This paper deals with the development of an accurate and precise humidity sensor, which is based on the extension of Thompson and Lampard theorem and a sol–gel-based thermally and chemically stable metal oxide thin film. In light of the extension of the theorem, most appropriate conductors are shaped around the material and the resulting sensor has cross conductance, which is the function of thickness only. It is fabricated and tested for different ranges of humidity. It is found that the fabricated sensor has outstanding static and dynamic characteristics. [ABSTRACT FROM PUBLISHER]

In this paper, we are proposing a novel rapid sol–gel thin-film porous metal–oxide-based surface acoustic wave (SAW) humidity sensor. For the SAW sensor, the center frequency of 433.92 MHz has been selected, and the device has been configured in a high-frequency oscillator circuit to explore the frequency response in the presence of water vapor. The sensitive thin film of sol–gel $\gamma $ -Al2O3 coated with a drop dry method offers very high surface-to-volume ratio with the distribution of micropores making the sensor highly sensitive for moisture detection. Pore morphologies of the film have been studied by field emission scanning electron microscope and atomic force microscopy. The \gamma $ phase of alumina of the film has been characterized with X-ray diffraction. The sensor has been tested from 3% relative humidity (RH) to 85% RH. The proposed sensor has very fast ( T_{r}= 1 s) response time and excellent yield ratio in comparison with the conventional commercial capacitive aluminum oxide sensor. The sensitivity (3%–20% RH) and the hysteresis (3%–85% RH) are found to be 120-Hz/% RH and 0.3%, respectively. The sensor can be useful for different applications, including moisture dispersion inside electronic gadgets, dryers, ovens, textile production, semiconductor device processing, food processing, medicine, and sealed packages. [ABSTRACT FROM PUBLISHER]

This paper presents a surface-micromachining technology to fabricate silicon carbide (SiC)-based capacitive micromachined ultrasonic transducers (CMUTs). The use of dc-sputtered amorphous SiC as a structural layer allows the fabrication process to limit the temperature to a thermal budget of 200 °C, which is the lowest reported to date, making this technology ideally suited for above-IC integration. The high Young's modulus of the deposited SiC film, along with its very low residual stress, results in high strength and resilient CMUT membranes. The placement of the suspended aluminum electrode directly at the bottom side of the membrane reduces the effective size of the electrostatic transduction gap, resulting in superior electro-mechanical coupling. Fabricated transducers are tested in air with both continuous-wave and pulsed signals, using a pitch-and-catch configuration. The transducer pair, composed of 110-μm-diameter membrane arrays, exhibits a resonant frequency of 1.75 MHz, a 3 dB-bandwidth of 0.15 MHz, and a transmission gain of -38 dB. The CMUT prototypes showcase the versatility of low-temperature dc-sputtered SiC films applied in the field of MEMS. [ABSTRACT FROM AUTHOR]

We present an enhanced in-plane capacitive readout for sensing out-of-plane displacement in a MEMS acoustic sensor. The sensor is fabricated in a multi-user silicon-on-insulator process, using a thicker device layer to reduce misalignment between moving and fixed comb fingers. This misalignment is found to reduce the sensitivity and render the response nonlinear. In addition, incorporation of a branched comb design doubles the readout capacitor surface area for a given sensor size, to further increase the sensitivity. These two modifications restore linearity to the readout and increase its sensitivity to displacement by an order of magnitude. [ABSTRACT FROM AUTHOR]

We report on the design, fabrication, and characterization of a microfabricated 3D magnetic field sensor that is suitable for co-integration with inertial sensors to form single-chip inertial measurement units. In contrast to classical resonant MEMS magnetometers, which are based on Lorentz force measurement, our sensor uses permanent magnetic materials and piezoresistive detection with silicon strain gauges of nanometric section, leading to low power consumption and high sensitivity for small sensor size. Thin multilayers of CoFe and PtMn as ferro- and antiferromagnetic materials are integrated within the MEMS fabrication process. Sensitivities of 1.09 V/T for x- and y- components of the magnetic field and 0.124 V/T for z- component of the magnetic field were measured, respectively. To be sensitive to magnetic fields along all three spatial directions, two permanent magnetization directions on the same die are required. Implementation of the two magnetization directions was validated by a measured correlation of 99.7% between x- and y- sensitivity axes. Power consumption of the 3D sensor is for polarization with a 100 μA dc current. With resolutions of 100 nT/√Hz for x- and y-component of the magnetic field and 350 nT/√Hz for z- component, the sensor is suitable for precise measurement of earth magnetic field. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis of a new zigzag C-axis inclined multi-layer ZnO thin-film bulk acoustic wave resonator (FBAR) as a viscosity sensor to monitor the lubrication performance of engine oil and other liquids. Free vibration and forced vibration for the FBAR loaded with liquids are analyzed. Equations necessary to calculate the sensitivity are derived. The numerical analysis shows that as the number of layers increases, the absolute sensitivity increases as well. The influences on the sensitivity of C-axis inclined angle, Q-factor, and thickness are also investigated. The results provide a foundation for further design of multi-layer FBAR viscosity sensors. [ABSTRACT FROM AUTHOR]

This paper introduces an improved method for monitoring and controlling the contact condition of terahertz on-wafer probes to enhance the measurement repeatability as well as probe lifetime. This method enables accurate contact force and contact angle measurements without modification to the standard probe station. Both probe contact force and contact angle are crucial for RF measurement repeatability. Repeatable probe contact force can be achieved by properly monitoring and controlling the strain generated at designated positions on the terahertz probe due to probe deformation induced by contacting the test substrate. Contact angle can be measured by asymmetrical strain on symmetrical positions of the probe when the probe is contacting the test substrate with angular misalignment. In this work a WR-1.5 (500 GHz-750 GHz) probe with integrated strain sensor is developed and tested. Mechanical tests show that the integrated sensors have a contact force resolution of 0.2 mN and a contact angle resolution of 0.05^\circ about the center. RF tests show that repeatable measurements can be achieved with 3 mN contact force after adjusting probe contact angle using the integrated sensors, as compared to a previously reported value of 15 mN. [ABSTRACT FROM AUTHOR]

A very sensitive thin-film sensor was developed using a meandering coplanar line fabricated from Sr33Ti16O51 film (3 \mu \textm thick), amorphous Co85Nb12Zr3 film ( 1~\mathrm mm \times 2.45 mm, 0.3–2 \mu \textm thick), and Cu/Cr film (2/0.1 \mu \textm ). The deposited SrTiO film enhanced the sensitivity of a magnetic field sensor, a phase change of more than 30°/Oe and a gain of over −40 dB being achieved simultaneously. The maximum phase change (sensitivity) was observed for a CoNbZr film thickness of $\sim 0.5$ –1 \mu \textm . The sensitive bias field and carrier frequency increased as the CoNbZr film thickness increased. The optimum CoNbZr film thickness was realized by the tradeoff between the sensitive bias field and the volume of the CoNbZr film. [ABSTRACT FROM AUTHOR]

Until recently, our work on superconducting thin film phonon sensors for cryogenic detector applications was limited to silicon substrates only. We have now successfully extended low T/sub c/ (/spl les/100 mK) tungsten sensor technology and sensor fabrication capability to include high purity germanium substrates as well. Here, we describe a technique for fabricating low T/sub c/ superconducting tungsten films on germanium, and we present first results from cryogenic characterization experiments with these films. We also summarize our work on the development of a process to independently etch aluminum and tungsten films deposited on the same germanium substrate. The capability to selectively etch aluminum and tungsten films is critical for the fabrication of our silicon and soon also germanium detectors which utilize overlapping thin films of superconducting tungsten and aluminum for the phonon sensors. Due to the nature of their operation, we refer to these sensors as W/Al Quasiparticle trap assisted-Electrothermal feedback-Transition edge (QET) Sensors. [ABSTRACT FROM PUBLISHER]

During the 1980s a SQUID-based superconducting gradiometer prototype utilizing bulk niobium and wire superconducting components cooled by liquid helium was developed by the US Navy. This sensor was successfully utilized in demonstrations for sea mine countermeasures and for the detection of UneXploded Ordnance (UXO). Advances in this sensor technology are being pursued for longer detection ranges and for more versatile operation. An advanced sensor prototype using all thin film niobium circuits and a new liquid helium cooling concept has been built to provide significant increases in sensitivity. In addition, a high Tc sensor concept using liquid nitrogen refrigeration has been developed to reduce package size and to simplify logistic and support requirements for field operation. This paper will review the current status and plans of this program, specifically describing the recent advances in sensor development and results from the demonstration to detect UXO. [ABSTRACT FROM PUBLISHER]