Crystal growth of Hg1−xMnxSe for infrared detection

2007

In this work, we report on the successfully growing Hg"1"-"xMn"xSe bulk crystals using a mixed, travelling heater method and Bridgman method, two-step procedure. Firstly, and with the aim of reducing Hg high pressure related to the high temperature synthesis reaction between the components in elemental form, HgSe crystals were synthesized and grown by the cold travelling heater method. Secondly, previously sublimated Mn and Se were incorporated to complete the desired composition. Then, the Bridgman growth was carried out by heating the alloy at a temperature of about 880^oC and lowering it at rate of 1mm/h through a gradient of 25^oC/cm. The Hg"1"-"xMn"xSe crystals were characterized by sc…

Modeling of Magnetoresistive-Based Electrical Current Sensors: A Technological Approach

2007

The utilization of modeling tools can, in many cases, help us in the design and final prototyping of any sort of sensors. In this paper, we describe a finite-element method (FEM) model applied to a hybrid technology involving a full Wheatstone bridge spin-valve-based electrical current sensor. After validating the model against experimental results, we focus our studies on geometrical aspects of the sensor configuration, in order to detect possible deviations that may have occurred during the fabrication process. In this regard, the characteristics of the behavior of the sensor depending on lateral displacements and inclination are included. Moreover, the frequency response of the sensor is…

Vapor growth of Hg1−xCdxI2 on glass using CdTe buffer

2001

Abstract Vapor phase epitaxy (VPE) of Hg1−xCdxI2 layers on glass substrates covered by a CdTe buffer layer has been studied. The buffer layers of 2–4 μm thickness were formed by VPE using polycrystalline CdTe and Cd metal sources. The Hg1−xCdxI2 layers were grown using a (Hg1−yCdy)1−z(I2)z polycrystalline source, with a composition in the range of y=0.1–0.5 and z=0.5–0.8. Scanning electron microscopy and X-ray diffraction studies have shown that the composition and structure of Hg1−xCdxI2 layers depend strongly on the VPE conditions. Varying the growth time and source composition, it has been possible to obtain Hg1−xCdxI2 layers with the composition x in the range from approximately 0 (HgI2…

Crystal growth of ZnO micro and nanostructures by PVT on c-sapphire and amorphous quartz substrates

2010

Abstract ZnO micro and nanostructures in the form of tripods, grains, arrows and wires have been grown at temperatures as low as 500–300  ∘ C by a vapour transport method without catalysis and using a well selected value of the carrier gas flow. A transition state between grains and nanowires is reported being characterized by arrow-like structures which are constituted by a pyramidal head and a tail that is growing from the basal plane of the head. In order to understand the effect of growth conditions on the morphology of micro and nanostructures, an analysis of temperature and species concentration conditions has been carried out. In addition two different kinds of substrates have been u…

Address Event Representation (AER) approach to resistive sensor arrays

2020

Address event representation (AER) has become an excellent strategy when approaching traditional frame based applications, mainly vision sensors. In this paper, and Within this scope, the potential of the AER paradigm is demonstrated when considering resistive (non-vision) sensor arrays. For showing quantitative evidences, MOS AMS 0.35 μm versions of some of the circuit cells typically used in AER systems, such as Winner-Take-All (WTA) circuits, have been implemented and analyzed. In these unit-cells, basic resistance-controlled sources are considered as per sensing devices. Preliminary simulation results demonstrate that this approach is valid for a wide range of resistive sensors.

Magnetic Tunnel Junction (MTJ) Sensors for Integrated Circuits (IC) Electric Current Measurement

2013

We report on MgO Magnetic Tunnel Junction (MTJ) devices focusing on their potential application in the measurement of electrical current at the integrated circuit level. Single devices and full bridges have been specifically developed for this purpose. A sort of different designs regarding their geometry arrangement as well as the number of constitutive elements have been tested. Experimental characterization has been performed and results including impedance and sensitivity measurements are given.

Design of Advanced Digital Systems Based on High-Speed Optical Links

2012

Optical fiber links offer very important benefits as EMI immunity, low losses, high bandwidth, etc, so an increasing number of communication applications are being developed and deployed. At both sides of these optical links, the optical data signal has to be converted to (or from) the electronic domain. The processing of such a high speed optical signals is not straightforward in most cases, and special considerations need to be taken into account for a proper electronic design.

Dual-band printed dipole antenna for Wi-Fi 802.11n applications

2010

A dual-band compact printed dipole antenna for Wi-Fi 802.11n applications in the 2.45 and 5.5 GHz bands is presented. The proposed antenna consists of two printed dipoles with the arms located onto both sides of the dielectric substrate and a bended stripline. This feed scheme makes easy the integration of the antenna with the electronic subsystem and avoids the radiation towards the device. For the design and optimisation, a specifically developed finite-difference time-domain based code is used. The antenna has then been fabricated, simulated and measured. The return losses highly match the Wi-Fi frequency specifications with a moderate gain (between 1 and 3 dBi) and efficiency better tha…

Design, fabrication, and analysis of a spin-valve based current sensor

2004

Abstract In this work, we suggest a novel current sensor design, based on spin valve technology, with a full Wheatstone bridge configuration. The principal characteristic is that the four magnetoresistance sensing elements, fully active, are deposited and patterned at the same time. This way, differences among them should be insignificant, so improving voltage offset and drift temperature parameters. The complete IC fabrication process involves only three lithography steps, making the process cheaper and faster. In order to get a balanced bridge, the measured current must be properly driven, by means of an auxiliary PCB. Some prototypes, with different input impedances, have been fabricated…

Circuit simulators for circuit analysis in graduate engineering courses

2018

Circuit simulators are extensively used as an aid in many courses at the graduate level in many different engineering and applied sciences programs. SPICE (Simulation Program with Integrated Circuits Emphasis) based software programs have been used for long due to their traditional market position. If we focus on circuits analysis and linear systems subjects, the features that are required from a given simulator can be found in student/limited versions of commercial EDA (Electronic Design Automation) suites or in freeware/open source codes. In this contribution, we analyse and compare the most revelant characteristics of a representative set of the software packages that are commonly adopte…

Calculation of the characteristic impedance of microstrips using a full-wave 2-D FDTD scheme

1997

The frequency dependence of the characteristic impedance of microstrip lines has been investigated by many authors using 3D-FDTD formulations. In the present letter, a two-dimensional FDTD scheme is used to calculate both the propagation constant and the characteristic impedance of the fundamental quasi-TEM mode in a microstrip which, in fact, is a hybrid mode. Because of the substantial reduction of computer resources required for the calculations, this method can be used as a design tool. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 58–60, 1997.

Editorial Article for Open Journal of Antennas and Propagation

2013

Antennas help communicate the World. Antennas make possible that millions of people can watch the Champions League. Antennas allow the positioning of billions of vehicles around our planet. And they also allow handling vehicles through our neighbor planets. By propagating waves through antennas you can send huge amounts of data in milliseconds. Besides, you can also tell somebody that you love him or her. Antennas have allowed communicate the people in these places where cables cannot. But antennas are not only used for communication. Antennas can be used for heating food, for detecting people, for guiding vessels, for founding treasures, for monitoring breath, for harvesting energy and so …

Vapor phase epitaxy of Hg1−xCdxI2 on sapphire

1998

Abstract We demonstrate the possibility of growing Hg 1− x Cd x I 2 layers on sapphire substrates by vapor-phase epitaxy (VPE). The successful growth has been carried out using an α-HgI 2 polycrystalline source and a CdTe buffer layer grown on sapphire by metalorganic vapor phase epitaxy (MOVPE) before the Hg 1− x Cd x I 2 VPE growth. The Hg 1− x Cd x I 2 /sapphire 20–40 μm thick layers with a uniform composition in the range of x =0.2–0.6 were grown at 220–250°C for 70–300 h. The layers were studied by scanning electron microscopy, energy disperse X-ray analysis and X-ray diffractometry. Results on the layer characterization are reported and the effect of VPE conditions on the layer proper…

Full-wave FDTD design and analysis of wideband microstrip-to-waveguide transitions

2003

Wideband transitions are designed and analysed by using two different approaches of the finite-difference time-domain (FDTD) method, in combination with the theory of nonuniform transmission lines. These transitions consist of a ridged waveguide-based taper between a shielded microstrip and a standard X-band rectangular waveguide. In the first step, a full-wave 2D-FDTD scheme is used to calculate the dispersion characteristics, as well as the geometry dependence of the impedance in the double ridged waveguide. Once these design curves have been obtained, the stepped transmission line transformer theory is used to design the tapers. In a former step, the nonuniform 3D-FDTD technique is appli…

A DC behavioral electrical model for quasi-linear spin-valve devices including thermal effects for circuit simulation

2011

An advanced model for quasi-linear spin-valve (SV) structures is presented for circuit simulation purposes. The model takes into account electrical and thermal effects in a coupled way in order to allow a coherent representation of the sensor physics for design purposes of electronics applications based on these sensor devices. The model was implemented in Verilog-A and used in a commercial circuit simulator. For testing the model, different SV structures have been specifically fabricated and measured. The characterization included DC measurements as well as steady-state and transient thermal analysis. From the experimental data, the parameters of the model have been extracted. The model re…

Analytical compact modeling of GMR based current sensors: Application to power measurement at the IC level

2010

An analytical compact model for giant magnetoresistance (GMR) based current sensors has been developed. Different spin-valve based full Wheatstone bridge sensors, with the current straps integrated in the chip, have been considered. These devices have been experimentally characterized in order to extract the model parameters. In this respect, we have focused on the sensors linear operation regime. The model, which allows the individual description of the magnetoresistive elements, has been implemented in a circuit simulator by means of a behavioral description language: Verilog-A. We also propose the use of the devices in a direct power measurement application at the integrated circuit (IC)…

A new bi-faced log periodic printed antenna

2005

In this paper, a new design of a broadband planar printed antenna based on the academic log periodic antenna is presented. The antenna consists of a series of printed dipoles, distributed on both faces of the substrate. Some configurations are explored, with a different number of printed dipoles. These are designed, simulated, fabricated, and measured. The calculated and measured return losses and radiation patterns are presented. The utility of the proposed antenna associated with its frequency bandwidth is better than 80%. The measured absolute gain is 6.5 dBi, and the front-to-back ratio is around 8 dB. The presented antenna should find wide applications in wireless communication systems…

A novel current-based approach for very low variation detection of resistive sensors in wheatstone bridge configuration

2014

Measuring low H field and currents with AMR sensors

2017

The growing demand from the automotive industry for high accuracy magnetic sensors and the need to perform high resolution angular position measurements have been the drivers for the industrial research in magnetic sensing technologies. This paper describes the design and characterization of several experimental devices implementing simple magnetoresistive structures targeting contactless current measurement in the tens to hundreds of milliamps range with sub-mA resolution. The ultimate goal is to extend the application area of magnetoresistive sensors beyond their current niche in automotive into more general applications. The initial set of devices tested to-date has shown a sensitivity o…

FDTD analysis of E-sectoral horn antennas for broad-band applications

1997

The finite-difference time-domain (FDTD) method is applied to study the performance of E-plane sectoral horn antennas designed for broad-band applications. These antennas (proposed for 6-18 GHz phased arrays) have a large bandwidth, and they are easily array integrated. These antennas have a highly complicated geometry that is modeled using a polygonal approximation in the curved boundaries. Perfect matched layers (PMLs) combined with first-order absorbing boundaries are employed to simulate the free-space environment in the FDTD mesh.

Automated Soil Moisture Monitoring Wireless Sensor Network for Long-Term Cal/Val Applications

2012

The design and development of a wireless sensor network for soil moisture measurement in an unlevelled 10 km × 10 km area, is described. It was specifically deployed for the characterization of a reference area, in campaigns of calibration and validation of the space mission SMOS (Soil Moisture and Ocean Salinity), but the system is easily extensible to monitor other climatic or environmental variables, as well as to other regions of ecological interest. The network consists of a number of automatic measurement stations, strategically placed following soil homogeneity and land uses criteria. Every station includes acquisition, conditioning and communication systems. The electronics are batt…

Under The Background Influence (UTBI): 2006 Opportunity for Flight

2006

Growth and characterization of GdxHg1−xSe crystals

2008

Abstract The growth of GdxHg1−xSe crystals by the vertical Bridgman method was studied in the composition range 0⩽x⩽0.1. The structural and electronic properties of GdxHg1−xSe crystals were investigated as a function of composition. It was found that an increase in gadolinium content up to x=0.01 results in a decrease of structural defects and an increase in electron mobility up to the maximum value of μ77≈2.8×105 cm2/V s. Structural defects start to increase at x>0.01, and the formation of Gd2Se3 amorphous phase takes place at x>0.03. On the base of the electron-spin resonance investigation, it was shown that the Gd incorporates into the HgSe host in Gd3+ charge state at the concentration …

Integration of GMR sensors with different technologies

2016

Less than thirty years after the giant magnetoresistance (GMR) effect was described, GMR sensors are the preferred choice in many applications demanding the measurement of low magnetic fields in small volumes. This rapid deployment from theoretical basis to market and state-of-the-art applications can be explained by the combination of excellent inherent properties with the feasibility of fabrication, allowing the real integration with many other standard technologies. In this paper, we present a review focusing on how this capability of integration has allowed the improvement of the inherent capabilities and, therefore, the range of application of GMR sensors. After briefly describing the …

Postgraduate level analog microelectronics course based on cadence IC software and AMS 0.35 µm technology

2021

An analog microelectronics design course at the post-graduate level is described in this paper. In 30 h, students with different engineering background receive a basic but solid formation by implementing a complete microelectronics design flow, following current industry standards. The course deals with fundamental design blocks as well as specific computer aided design tools. This course can be taught, as it is, as a fundamental module in general electronics/communications masters, but it can be also tuned to match specific curriculum constraints, if required. It has been successfully taught for two years, with minor adjustments, within the Telecommunications Engineering Master, at the Un…

Current-Based Measurement Technique for High Sensitivity Detection of Resistive Bridges With External Balancing Through Control Voltages

2017

We present a novel approach based on differential measurements of dc currents with very high sensitivity suitable for the detection of very small variations of resistors in Wheatstone full-bridge configurations. External control voltages allow for the compensation of the bridge unbalancing avoiding the need of changing its elements so making the solution suitable for integrated sensor systems. The proposed current-based measurement technique has been implemented through three different circuits, in transimpedance configuration and without the use of any further amplification stage, employing only two active blocks that allow for a very high integration level. The main characteristics of the…

Synthesis and characterization of ZnO nano and micro structures grown by low temperature spray pyrolysis and vapor transport.

2012

In this work we present a systematic study of ZnO micro and nanostructures grown by spray pyrolysis (SP) and by physical vapour transport (PVT) on glass and c-sapphire substrates at low temperatures. Optimised growth conditions have allowed to obtain homogeneous ZnO nanolayers composed of quasi-spherical nanoparticles in the range 2 to 8 nm by spray pyrolysis, while by PVT the selected growth conditions allow to produce a wide variety of morphologies (tripods, grains, arrows and wires) of nano and microsize dimension. Grazing incidence X-ray diffraction, field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), selected area electron dif…

Quasi‐digital front‐ends for current measurement in integrated circuits with giant magnetoresistance technology

2014

In this study, the authors report on two different electronic interfaces for low-power integrated circuits electric current monitoring through current-to-frequency (I-f) conversion schemes. This proposal displays the intrinsic advantages of the quasi-digital systems regarding direct interfacing and self-calibrating capabilities. In addition, as current-sensing devices, they have made use of the giant magnetoresistance (GMR) technology because of its high sensitivity and compatibility with standard complementary metal oxide semiconductor processes. Single elements and Wheatstone bridges based on spin-valves and magnetic tunnel junctions have been considered. In this sense, schematic-level si…

A numerical study of thermal conditions in the THM growth of HgTe

2002

A numerical simulation of the travelling heater method (THM) process in the growth of HgTe is carried out. The whole system (furnace, ampoule and charge) is taken into account in the frame of a quasi-steady-state model. The mass conservation condition for the solute in the liquid zone permits the determination of the rate of advance of the crystallisation isotherm as a function of the heater position. We claim to study the evolution of different magnitudes along the growth process, searching for the physical reasons which could be at the origin of defects in the form of thin layers observed in some growing experiences. To solve the governing equations of fluid flow, heat transfer and mass t…

Self-Healing of Redundant FLASH ADCs

2022

For the design of high-speed ADCs, the traditional speed-accuracy trade-off can only be solved at the expense of power consumption. Using fast small transistors takes full advantage of technology scaling but induces large amounts of random variability. Redundancy has been proposed as a way to cope with variability in FLASH converter and open the trade-off. The offset of redundant comparators are measured and only the best candidates which have been selected are powered-up. However, the candidate selection is usually carried out in foreground and a lot of silicon area is thus occupied by comparators that will only be used once, during calibration. In this paper we show how such an approach, …

Giant Magnetoresistance (GMR) sensors for 0.35µm CMOS technology sub-mA current sensing

2014

This paper reports on the design and fabrication of microelectronic structures for non-invasive indirect electric current sensing at the IC level. A 0.35 ?m CMOS ASIC has been specifically developed for this purpose. Then, a low temperature post-process, fully compatible with the CMOS technology, has been applied for depositing Giant Magnetoresistive (GMR) sensors. Preliminary experimental results for obtaining the sensitivity of the devices are presented. The detection limit is estimated to be about 5 ?A.

Quasi-static magnetoresistive sensor modeling for current-time conversion circuit applications

2011

In this paper we report a current-to-time converter (CTC) suitable for current sensor monitoring in low power applications. Based on a discrete resistence-to-frequency converter and a Giant MagnetoResistance (GMR) current sensor. Simulations have been done using a quasi-static electrical Verilog-A model for the GMR current sensor. A reduced set of parameters has been extracted to characterize the GMR sensor's behavior. The application has been analyzed making use of different sensors, whose device parameters were previously extracted. Finally, the accuracy of the models has been tested by comparing with experimental transient measurements.

Crystal Growth of HgSe by the Cold Travelling Heater Method

2002

We report on the low-temperature synthesis and growth of HgSe crystals making use of the cold travelling heater method. Ingots so obtained are analyzed by means of scanning microscopy, including EDAX and backscattered electron modes, and X-ray diffraction techniques.

CMOS Capacitance-to-Time Converter-Based Interface for Differential Capacitive Sensors

2020

This paper presents pre-layout simulation results on a CMOS implementation of a capacitance-to-time converter-based electronic interface for differential capacitive sensors. Its simple architecture, comprising only three operational amplifiers (OA) and a digital mixer (inverted XOR gate) allows, by properly setting the values of seven biasing resistors, to fit the working range anywhere from few fF to hundreds of pF, giving the output quasi-digital signals (T and PW) in the useful μs-ms range (appropriate for direct interfacing with general purposes microcontrollers). A couple of illustrative examples are provided.

Advanced Giant Magnetoresistance (GMR) sensors for Selective-Change Driven (SCD) circuits

2021

Nowadays, bio-inspiration is driving novel sensors designs, beyond vision sensors. By taking advantage of their compatibility with standard CMOS technologies, the integration of giant magneto-resistance (GMR) based magnetic sensors within such event-driven approaches is proposed. With this aim, several topologies of such GMR sensors have been designed, fabricated and characterized. In addition, integrated circuit interfaces of a standard CMOS technology are also proposed. Their suitability for this approach is then demonstrated by means of Cadence IC simulations.

Monolithic integration of GMR sensors for standard CMOS-IC current sensing

2017

Abstract In this work we report on the development of Giant Magnetoresistive (GMR) sensors for off-line current measurements in standard integrated circuits. An ASIC has been specifically designed and fabricated in the well-known AMS-0.35 μm CMOS technology, including the electronic circuitry for sensor interfacing. It implements an oscillating circuit performing a voltage-to-frequency conversion. Subsequently, a fully CMOS-compatible low temperature post-process has been applied for depositing the GMR sensing devices in a full-bridge configuration onto the buried current straps. Sensitivity and resolution of these sensors have been investigated achieving experimental results that show a de…

A low-cost compact uniplanar Quasi–Yagi printed antenna

2008

A low cost directive uniplanar broadband printed Quasi–Yagi antenna design is presented. As a particular realization, some prototypes have been designed to operate in the 2.45 GHz band. They have been then modeled, fabricated onto standard printed circuit dielectric substrate and tested successfully. For the design and the modeling processes, we have make use of FDTD based in-house developed algorithms. The obtained bandwidth is, for all the considered cases, better than 15%. The main radiation characteristics are 2–5.5 dBi gain, depending on the number of director elements, and better than 25 dB front-to-back ratio. Overall antenna size was, in any case lesser than 1 λ × 0.5 λ. © 2008 Wile…

Temperature and pressure dependence of the optical absorption in hexagonal MnTe

2000

The absorption edge of hexagonal (NiAs structure) antiferromagnetic MnTe has been measured by means of light transmission experiments carried out at different temperatures in the range 16--420 K $(P=1\mathrm{bar})$ and hydrostatic pressures up to 9 GPa $(T=295\mathrm{K}).$ An indirect band gap has been found, in agreement with previous band-structure calculations, with an energy of ${E}_{\mathrm{ig}}=1.272\ifmmode\pm\else\textpm\fi{}0.013\mathrm{eV}$ at room temperature and pressure. The temperature dependence of the absorption edge is linear above the N\'eel temperature ${T}_{N}=310\mathrm{K},$ with a temperature coefficient $dE/dT=\ensuremath{-}(3.5\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode…

Self-Assembled Zinc Oxide Quantum Dots Using Spray Pyrolysis Methodology

2011

Self-assembled ZnO quantum dots (QDs) have been obtained on different substrates by using the atmospheric spray pyrolysis methodology under well-defined growth conditions. The evolution of size and...

Printed Antennas for Sensor Applications: A Review

2014

With the expansion in number and requirements of modern wireless communications, the technology related to their associated antennas has been continuously improved. Among other options, printed antennas offer excellent features, such as low weight, profile, and cost, while maintaining good performance characteristics. In addition, their straightforward integration with electronics has opened new fields of application such as smart sensing systems. Printed antennas can be used in different parts of a wireless smart sensor as a radio link, sensing element, or even as energy harvester. In this paper, we present a thorough review of recent advances of printed antennas as regards their use in sm…

Quasi-digital conversion for resistive devices: application in GMR-based IC current sensors

2013

Resistive devices, including sensors, are used in a huge range of applications within different scenarios. When a complete system is considered, a quasi-digital output is often recommendable. If the conversion is operated at device level, some problems such as noise disturbs, insertion losses and so on, can be reduced. In this work, we describe a resistance-tofrequency (R-f) converter with a suggested application in low current monitoring by means of GiantMagnetoResistance (GMR) sensors. Specific devices have been designed and microfabricated. The system has been tested by means of discrete components with a PCB. The complete microsystem monolithic integration in a standard CMOS technology …

Sub-mA current measurement by means of GMR sensors and state of the art lock-in amplifiers

2015

Electric current measurement at the range of μA in integrated circuit has been traditionally carried out by micro-electronically engineered systems, such as current mirrors or charging capacitors. However, off-line, i.e., non-intrusive methods provide advantages related to size and power consumption. In this sense, giant magnetoresistance (GMR) magnetic sensors are optimal due to their sensitivity and CMOS compatibility. In this work, we make use of specifically designed CMOS GMR-based current sensors in combination with a custom electronic interface based on a low-voltage low-power lock-in amplifier, demonstrating the capability of this combination for current measurement in the range of μ…

A new approach to the crystal growth of Hg1−xMnxTe by the cold travelling heater method (CTHM)

2001

Abstract In order to obtain crystals with a homogeneous composition and to reduce the Hg high pressure related to the temperature synthesis reaction between the components in elemental form, Hg 1− x Mn x Te bulk crystals were produced by the cold travelling heater method (CTHM). Following the technique initially proposed for the growth of CdHgTe by the Triboulet group, the feed material was a split ingot of two segments, one of HgTe and the other of MnTe, with cross-sectional areas chosen to establish the desired final composition. The growth was carried out at a temperature of 600°C and a rate of 2 mm/h. The Hg 1− x Mn x Te crystals have been characterised by scanning electron microscopy, …

Effect of structural and compositional inhomogeneities on spin-glass transition in Hg1−x−yCrxMnySe crystals

2004

Abstract We report experimental results on the growth of Hg 1 −x−y Cr x Mn y Se crystals and their magnetic susceptibility χ ( T ) in dependence on the crystal structure and composition. It was found that the crystals with the Mn composition y =0.01–0.08 exhibit the spin-glass transition temperature T g =100–110 K. An increase of y value leads to the saturation of the χ max and T g characteristics in the composition ranges of y >0.06 and y >0.02, respectively. This phenomenon is explained as a result of phase-separated magnetic behavior caused by the formation of HgCr 2 Se 4 inclusions and textures.

Electrical Modeling of Monolithically Integrated GMR Based Current Sensors

2018

We report on the electrical compact model, using Verilog-A, of a monolithically integrated giant magnetoresistance (GMR) based electrical current sensors. For this purpose, a specifically designed ASIC (AMS $0.35\mu \mathrm{m}$ technology) has been considered, onto which such sensors have been patterned and fabricated, following a two-steps procedure. This work is focused on the DC regime model extraction, giving evidences of its good performance and stating the bases for subsequent model improvements.

Growth and characterisation of MnTe crystals

2001

We report on the low temperature growth of MnTe crystals by means of travelling solution methods. Two different processes are considered; a classical THM process using a low temperature presynthesised MnTe ingot, and a modified THM process, in which an increasing length of solvent zone collects the tellurium that was added to the stoichiometric charge to decrease the reaction temperature. Ingots from the two methods are analysed by means of scanning electron microscopy, X-ray diffractometry, resistivity, susceptibility and optical absorption measurements.

Spray pyrolytic deposition of ZnO thin layers composed of low dimensional nanostructures

2010

Abstract ZnO nanolayers composed of fine nanostructures have been successively grown by spray pyrolytic deposition at 300  ∘ C over amorphous glass substrates. As deposited samples were analysed by scanning electron microscopy (SEM), showing a granular morphology with grain size in the limit of the microscope resolution. CL measurement shows a broad near band edge (3.4 eV) emission of ZnO in the UV region and the defect level emissions in the green region of the spectrum. The use of intermittent spray pyrolytic deposition is shown as an alternative to increase the homogeneity of the samples when temperatures near to the precursor pyrolytic decomposition is selected, long depositions times a…

A 4K-Input High-Speed Winner-Take-All (WTA) Circuit with Single-Winner Selection for Change-Driven Vision Sensors

2019

Winner-Take-All (WTA) circuits play an important role in applications where a single element must be selected according to its relevance. They have been successfully applied in neural networks and vision sensors. These applications usually require a large number of inputs for the WTA circuit, especially for vision applications where thousands to millions of pixels may compete to be selected. WTA circuits usually exhibit poor response-time scaling with the number of competitors, and most of the current WTA implementations are designed to work with less than 100 inputs. Another problem related to the large number of inputs is the difficulty to select just one winner, since many competitors ma…

Giant Magnetoresistance (GMR) Magnetometers

2016

Since its discovering in 1988, the Giant Magnetoresistance (GMR) effect has been widely studied both from the theoretical and the applications points of view. Its rapid development was initially promoted by their extensive use in the read heads of the massive data magnetic storage systems, in the digital world. Since then, novel proposals as basic solid state magnetic sensors have been continuously appearing. Due to their high sensitivity, small size and compatibility with standard CMOS technologies, they have become the preferred choice in scenarios traditionally occupied by Hall sensors. In this chapter, we analyze the main properties of GMR sensors regarding their use as magnetometers. W…

Sensing properties of ZnO nanostructured layers

2017

Nanostructured ZnO layers have been deposited onto SiO 2 /Si substrates by spray pyrolysis, with previously patterned interdigitated gold electrodes. We have then measured the capacitive and resistive response against ambient parameters such as relative humidity and illumination.

GMR Based Sensors for IC Current Monitoring

2013

The Giant MagnetoResistance (GMR) effect is a magnetic coupling mechanism that can be obtained in multilayer structures of few nanometers thick. In these devices, and at room temperature, the resistance is a function of the external magnetic field, at optimal levels for being used as sensors. Since the GMR effect was reported, scientists and engineers have dedicated their effort to this topic. This way, after two decades, a a very good knowledge of the GMR underlying physics together with notable designs of GMR based devices are nowadays available. They were initially used in the read heads of hard drives, but the constant evolution that this technology has experienced has open new fields o…

Broadband printed dipole with integrated via-hole balun for WiMAX applications

2010

A broadband balanced printed dipole antenna for WiMAX applications (2.5/3.6 GHz) is presented. An integrated via-hole balun is used to feed the antenna and a Yagi-like scheme is proposed to improve the gain. The design has been optimized by means of parametric FDTD simulations. The antenna was fabricated and measured, giving a bandwidth higher than 50% and a gain higher than 4 dBi. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:52–55, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25671

Design of Yagi-like printed antennas for WLAN applications

2007

A directive broadband printed Yagi-like antenna design is presented. We have focused on the 2.45 GHz WLAN band, at which some designs have been carried out. For the design and the modelling processes, we made use of FDTD based in-house developed algorithms. Some selected prototypes have then been fabricated onto a low-cost printed circuit board dielectric substrate and tested successfully. Bandwidths higher than 10% and moderate to high (>7 dBi) gains can be obtained this way. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2174–2178, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22655

Low-pressure synthesis and Bridgman growth of Hg1−xMnxTe

1999

To reduce Hg high pressure related to the high-temperature synthesis reaction between the components in elemental form, Hg 1-x Mn x Te bulk crystals were produced by a two-step procedure including (I) the alloy synthesis using HgTe crystals grown by the cold travelling heater method and elemental Mn and Te to complete the desired composition, followed by (II) the Bridgman growth. The growth was carried out at temperature in the range of 700-850°C and rate of 1 mm/h. The Hg 1-x Mn x Te crystals have been characterised by X-ray diffractometry, energy dispersive X-ray analysis, Fourier transformed infrared spectroscopy and Hall effect techniques. Although the distribution coefficient of Mn was…

Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

2009

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among o…

Monolithic integration of Giant Magnetoresistance (GMR) devices onto standard processed CMOS dies

2014

Giant Magnetoresistance (GMR) based technology is nowadays the preferred option for low magnetic fields sensing in disciplines such as biotechnology or microelectronics. Their compatibility with standard CMOS processes is currently investigated as a key point for the development of novel applications, requiring compact electronic readout. In this paper, such compatibility has been experimentally studied with two particular non-dedicated CMOS standards: 0.35 μm from AMS (Austria MicroSystems) and 2.5 μm from CNM (Centre Nacional de Microelectrònica, Barcelona) as representative examples. GMR test devices have been designed and fabricated onto processed chips from both technologies. In order …