Monolithic sensor integration in CMOS technologies

© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Besides being mainstream for mixed-signal electronics, CMOS technology can be used to integrate micro-electromechanical system (MEMS) on a single die, taking advantage of the structures and materials available in feature sizes around 180 nm. In this article, we demonstrate that the CMOS back-end-of-line (BEOL) layers can be postprocessed and be opportunistically used to create several kinds of MEMS sensors exhibiting good or even excellent performance, such as accelerometers, pressure sensors, and magnetometers. Despite the limitations of the available mechanical and material properties in CMOS technology, due to monolithic integration, these are compensated by the significant reduction of parasitics and system size. Furthermore, this work opens the path to create monolithic integrated multisensor (and even actuator) chips, including data fusion and intelligent processing.This work was supported in part by Baolab Microsystems; in part by the Spanish Ministry of Science, Innovation and Universities (MCIN); in part by the State Research Agency (AEI); in part by the European Social Fund (ESF) under Project RTI2018-099766-B-I00; in part by MCIN/AEI/10.13039/501100011033 under Grant PID2021-123535OB-I00; and in part by ERDF, “A way of making Europe.” The associate editor coordinating the review of this article and approving it for publication was Prof. Jean-Michel Redoute.Peer ReviewedPostprint (author's final draft

High performance readout circuits and devices for Lorentz force resonant CMOS-MEMS magnetic sensors

In the last decades, sensing capabilities of martphones have greatly improved since the early mobile phones of the 90’s. Moreover, wearables and the automotive industry require increasing electronics and sensing sophistication. In such echnological advance, Micro Electro Mechanical Systems (MEMS) have played an important role as accelerometers and gyroscopes were the first sensors based on MEMS technology massively introduced in the market. In contrast, it still does not exist a commercial MEMS-based compass, even though Lorentz force MEMS magnetometers were first proposed in the late 90’s. Currently, Lorentz force MEMS magnetometers have been under the spotlight as they can offer an integrated solution to nowadays sensing power. As a consequence, great advances have been achieved, but various bottlenecks limit the introduction of Lorentz force MEMS compasses in the market. First, current MEMS magnetometers require high current consumption and high biasing voltages to achieve good sensitivities. Moreover, even though devices with excellent performance and sophistication are found in the literature, there is still a lack of research on the readout electronic circuits, specially in the digital signal processing, and closed loop control. Second, most research outcomes rely on custom MEMS fabrication rocesses to manufacture the devices. This is the same approach followed in current commercial MEMS, but it requires different fabrication processes for the electronics and the MEMS. As a consequence, manufacturing cost is high and sensor performance is affected by the MEMS-electronics interface parasitics. This dissertation presents potential solutions to these issues in order to pave the road to the commercialization of Lorentz force MEMS compasses. First, a complete closed loop, digitally controlled readout system is proposed. The readout circuitry, implemented with off-the-shelf commercial components, and the digital control, on an FPGA, are proposed as a proof of concept of the feasibility, and potential benefits, of such architecture. The proposed system has a measured noise of 550 nT / vHz while the MEMS is biased with 300 µA rms and V = 1 V . Second, various CMOS-MEMS magnetometers have been designed using the BEOL part of the TSMC and SMIC 180 nm standard CMOS processes, and wet and vapor etched. The devices measurement and characterisation is used to analyse the benefits and drawbacks of each design as well as releasing process. Doing so, a high volume manufacturing viability can be performed. Yield values as high as 86% have been obtained for one device manufactured in a SMIC 180 nm full wafer run, having a sensitivity of 2.82 fA/µT · mA and quality factor Q = 7.29 at ambient pressure. While a device manufactured in TSMC 180 nm has Q = 634.5 and a sensitivity of 20.26 fA/µT ·mA at 1 mbar and V = 1 V. Finally, an integrated circuit has been designed that contains all the critical blocks to perform the MEMS signal readout. The MEMS and the electronics have been manufactured using the same die area and standard TSMC 180 nm process in order to reduce parasitics and improve noise and current consumption. Simulations show that a resolution of 8.23 µT /mA for V = 1 V and BW = 10 Hz can be achieved with the designed device.En les últimes dècades, tenint en compte els primers telèfons mòbils dels anys 90, les capacitats de sensat dels telèfons intel·ligents han millorat notablement. A més, la indústria automobilística i de wearables necessiten cada cop més sofisticació en el sensat. Els Micro Electro Mechanical Systems (MEMS) han tingut un paper molt important en aquest avenç tecnològic, ja que acceleròmetres i giroscopis varen ser els primers sensors basats en la tecnologia MEMS en ser introduïts massivament al mercat. En canvi, encara no existeix en la indústria una brúixola electrònica basada en la tecnologia MEMS, tot i que els magnetòmetres MEMS varen ser proposats per primera vegada a finals dels anys 90. Actualment, els magnetòmetres MEMS basats en la força de Lorentz són el centre d'atenció donat que poden oferir una solució integrada a les capacitats de sensat actuals. Com a conseqüència, s'han aconseguit grans avenços encara que existeixen diversos colls d'ampolla que encara limiten la introducció al mercat de brúixoles electròniques MEMS basades en la força de Lorentz. Per una banda, els agnetòmetres MEMS actuals necessiten un consum de corrent i un voltatge de polarització elevats per aconseguir una bona sensibilitat. A més, tot i que a la literatura hi podem trobar dispositius amb rendiments i sofisticació excel·lents, encara existeix una manca de recerca en el circuit de condicionament, especialment de processat digital i control del llaç. Per altra banda, moltes publicacions depenen de processos de fabricació de MEMS fets a mida per fabricar els dispositius. Aquesta és la mateixa aproximació que s'utilitza actualment en la indústria dels MEMS, però té l'inconvenient que requereix processos de fabricació diferents pels MEMS i l’electrònica. Per tant, el cost de fabricació és alt i el rendiment del sensor queda afectat pels paràsits en la interfície entre els MEMS i l'electrònica. Aquesta tesi presenta solucions potencials a aquests problemes amb l'objectiu d'aplanar el camí a la comercialització de brúixoles electròniques MEMS basades en la força de Lorentz. En primer lloc, es proposa un circuit de condicionament complet en llaç tancat controlat digitalment. Aquest s'ha implementat amb components comercials, mentre que el control digital del llaç s'ha implementat en una FPGA, tot com una prova de concepte de la viabilitat i beneficis potencials que representa l'arquitectura proposada. El sistema presenta un soroll de 550 nT / vHz quan el MEMS està polaritzat amb 300 µArms i V = 1 V . En segon lloc, s'han dissenyat varis magnetòmetres CMOS-MEMS utilitzant la part BEOL dels processos CMOS estàndard de TSMC i SMIC 180 nm, que després s'han alliberat amb líquid i gas. La mesura i caracterització dels dispositius s’ha utilitzat per analitzar els beneficis i inconvenients de cada disseny i procés d’alliberament. D'aquesta manera, s'ha pogut realitzar un anàlisi de la viabilitat de la seva fabricació en massa. S'han obtingut valors de yield de fins al 86% per un dispositiu fabricat amb SMIC 180 nm en una oblia completa, amb una sensibilitat de 2.82 fA/µT · mA i un factor de qualitat Q = 7.29 a pressió ambient. Per altra banda, el dispositiu fabricat amb TSMC 180 nm presenta una Q = 634.5 i una sensibilitat de 20.26 fA/µT · mA a 1 mbar amb V = 1 V. Finalment, s'ha dissenyat un circuit integrat que conté tots els blocs per a realitzar el condicionament de senyal del MEMS. El MEMS i l'electrònica s'han fabricat en el mateix dau amb el procés estàndard de TSMC 180 nm per tal de reduir paràsits i millorar el soroll i el consum de corrent. Les simulacions mostren una resolució de 8.23 µT /mA amb V = 1 V i BW = 10 Hz pel dispositiu dissenyat

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Towards Single-Chip Nano-Systems

Important scientific discoveries are being propelled by the advent of nano-scale sensors that capture weak signals from their environment and pass them to complex instrumentation interface circuits for signal detection and processing. The highlight of this research is to investigate fabrication technologies to integrate such precision equipment with nano-sensors on a single complementary metal oxide semiconductor (CMOS) chip. In this context, several demonstration vehicles are proposed. First, an integration technology suitable for a fully integrated flexible microelectrode array has been proposed. A microelectrode array containing a single temperature sensor has been characterized and the versatility under dry/wet, and relaxed/strained conditions has been verified. On-chip instrumentation amplifier has been utilized to improve the temperature sensitivity of the device. While the flexibility of the array has been confirmed by laminating it on a fixed single cell, future experiments are necessary to confirm application of this device for live cell and tissue measurements. The proposed array can potentially attach itself to the pulsating surface of a single living cell or a network of cells to detect their vital signs

MEMS piezoelectric vibrational energy harvesters and circuits for IoT applications

In the Internet of Things (IoT) world, more and more sensor nodes are being deployed and more mobile power sources are required. Alternative solutions to batteries are the subjects of worldwide extended research. Among the possibilities is the harvesting of energy from the ambient. A novel energy harvesting system to power wireless sensor nodes is a necessity and inevitable path, with more and more market interest. Microelectromechnaical systems (MEMS) based piezoelectric vibrational energy harvesters (PVEH) are considered in this thesis due to their good energy densities, conversion efficiency, suitability for miniaturization and CMOS integration. Cantilever beams are favored for their relatively high average strains, low frequencies and simplicity of fabrication. Proof masses are essential in micro scale devices in order to decrease the resonance frequency and increase the strain along the beam to increase the output power. In this thesis, the effects of proof mass geometry on piezoelectric vibration energy harvesters are studied. Different geometrical dimension ratios have significant impact on the resonance frequency, e.g., beam to mass lengths, and beam to mass widths. The responses of various prototypes are studied. Furthermore, the impact of geometry on the performance of cantilever-based PVEH is investigated. Namely, rectangular and trapezoidal T-shaped designs are fabricated and tested. Optimized cross-shaped geometries are fabricated using a commercial technology PiezoMUMPs process from MEMSCAP. They are characterized for their resonant frequency, strain distribution and output power. The output of an energy harvester is not directly suited as a power supply for circuits because of variations in its power and voltage over time, therefore a power management circuit is required. The circuit meets the requirements of responding to an input voltage that varies with the ambient conditions to generate a regulated output voltage, and the ability to power multiple outputs from a fixed input voltage. In this thesis, new design architectures for a reconfigurable circuit are considered. A charge pump which modifies dynamically the number of stages to generate a plurality of voltage levels has been designed and fabricated using a CMOS 0.13 μm technology. This provides biasing voltages for electrostatic MEMS devices. Electrostatic MEMS require relatively high and variable actuation voltages and the fabricated circuit serves this goal and attains a measured maximum output voltage of 10.1 V from a 1.2 V supply. In this thesis, design recommendations are given and MEMS piezoelectric harvesters are implemented and validated through fabrications. T-shaped harvesters bring improvements over cantilever designs, namely the trapezoidal T-shaped structures. A cross-shaped design has the advantage of utilizing four beams and the proposed proof mass improves the performance significantly. A cross-coupled circuit rectifies the output efficiently towards an optimal energy harvesting solution

MEMS Oscillator를 탑재한 우주발사체용 위성항법수신기 성능 향상

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부, 2021.8. 박찬국.In this dissertation, the environmental and performance results of TCXO (temperature controlled crystal oscillator) and MEMS (micro electro mechanical system) oscillator are presented. The test results for each oscillator are compared, and based on the test results for the GNSS receiver to which each oscillator is applied, the replaceability of TCXO with MEMS oscillator is discussed. TCXO is a component that supplies a fixed and stable reference frequency by using a quartz crystal with a piezo electric effect, and it has low phase noise, high Q factor fitted for a resonator. The TCXO is widely used in precise clock and timing equipment as well as GNSS receivers. Through many temperature tests during development, the high level of frequency stability over temperature can be achieved by the surrounding compensation circuit. MEMS oscillator drastically reduced its size and weight by introducing micro scale manufacturing and packaging technology and uses silicon as a resonator. This reduction in size and weight makes MEMS oscillator robust under physical stress such as vibration and shock. However, silicon, which is used as a resonator of MEMS oscillator, has lower frequency stability over temperature compared to a quartz crystal, and relatively high phase noise occurs as the complex compensation circuit is required. Despite its advantages, the MEMS oscillator has not been widely used so far due to the tendency to use existing TCXOs. Electronic devices in space launch vehicles experience significant vibration, acceleration, and shock at the flight events such as lift-off, engine shutdown, stage, and pairing separation. And the performance tests under these physical stresses to verify operability should be conducted. In the pyrotechnic shock test, the GNSS receiver equipped with TCXO as a reference oscillator cannot maintain signal tracking, making the position fix fail. This phenomenon was caused by a sudden change in frequency output of TCXO due to the shock, and to address this issue, a MEMS oscillator, which is known to be robust in harsh environmental and stress conditions, was chosen to be utilized as a reference frequency oscillator instead of TCXO. To use the MEMS oscillator as a reference frequency of a GNSS receiver, the pyrotechnic shock, vibration, and temperature test for the MEMS oscillator itself were performed before assemble the GNSS receiver. In order to check the behavior of the GNSS receiver under the reference frequency change, the test using a signal generator, which simulates the reference frequency change without physical shock, was performed. After the test for the MEMS oscillator itself, the test of the GNSS receiver with the MEMS oscillator was conducted. The GNSS receiver can maintain signal tracking and calculate position normally under the pyrotechnic shock test, and the vibration and temperature tests are done without any issues. In environmental and performance tests, there are no problems due to the high phase noise of the MEMS oscillator, and the navigation accuracy was not much different from the existing GNSS receiver with TCXO.본 학위논문에서는 온도보상 수정발진기와 멤스 발진기에 대한 환경시험 및 성능시험 결과를 제시한다. 또한 각각을 탑재한 위성항법수신기에 대한 검증시험을 통해 위성항법수신기에 널리 사용되고 있는 온도보상 수정발진기를 물리적인 충격에 강인한 멤스 발진기로 대체하고자 한다. 온도보상 수정발진기는 압전성질을 지닌 쿼츠를 이용하여 안정적이고 정확한 주파수를 출력하는 부품으로 위상잡음과 손 실이 작아 기준주파수로 적합하다. 온도보상 수정발진기는 이미 정밀시계와 시각장치에 많이 이용되고 있으며, 위성항법수신기에도 널리 사용되고 있다. 단순한 수정진동자는 주변 온도에 민감하게 반응하지만 온도보상 수정발진기는 주변 온도를 측정하는 보상회로가 삽입되어 높은 온도 안정성을 보인다. 멤스발진기는 멤스 기술과 반도체 생산 기술에서 파생된 제조 기술을 바탕으로 온도보상 수정발진기와 비교해서 크기와 무게를 크게 줄였다. 크기가 작아짐에 따라 물리적인 충격과 진동에 강하나 출시 초기에는 높은 위상잡음과 온도변화에 의해 주파수 안정성이 낮아 제한적인 용도에만 사용되어 왔다. 최근 반도체 제작기술의 발달로 멤스 발진기도 온도보상 수정발진기 수준의 잡음 성능을 보이며, 시스템과의 일체화가 더욱 쉬워 응용분야가 넓어지고 있다. 우주발사체의 전자탑재물은 엔진 점화 혹은 페어링 분리와 같은 이벤트가 있을 때마다 강한 진동, 가속도 및 충격을 겪는다. 따라서 전자탑재물 제작시 온도, 진동, 가속도 및 충격과 같은 환경시험 을 수행하는데 온도보상 수정발진기를 탑재한 위성항법수신기가 파이로 충격시험시 항법신호를 놓치는 놓치는 문제가 발생하였다. 이 현상은 위성항법수신기에 탑재된 온도보상 수정발진기의 출력주파수가 충격에 의해 급격히 변하였기 때문이며 이를 위해서 여러 종류의 온도보상 수정발진기를 시험해보았으나 해결이 어려웠다. 멤스 발진기의 위성항법수신기 적용가능성을 확인하기 위해 먼저 파이로 충격환경 하에서 기존 수신기 추적루프에 대한 분석을 제시한다. 그리고 멤스 발진기에 대해 기존에 수행했던 온도, 진동 및 파이로 충격시험을 수행하고 온도보상 수정발진기와 주파수 출력을 비교하였다. 물리적인 환경인 진동과 파이로 충격 이외에 온도에 대해서도 멤스 발진기는 온도보상 수정발진기에 비해 좋은 주파수 안정성을 보였다. 멤스 발진기 자체의 환경시험 이후 위성항법수신기에 탑재하여 동일한 환경에서의 동작 성능을 확인하였고, 온도보상 수정발진기가 탑재된 기존의 위성항법수신기와 비교하여 성능차이가 없었으며 파이로 충격시험에서는 항법신호를 놓치지 않고 연속적인 항법을 수행하였다. 앞서 수행된 시험을 바탕으로 멤스 발진기를 위성항법수신기에 탑재하는데는 문제가 없음이 확인되어 온도보상 수정발진기를 대체할 수 있을 것으로 판단된다.Chapter 1 Introduction . 1 1.1 Motivation and Background 1 1.2 Objectives and Contributions . 4 1.3 Organization of the Dissertation . 5 Chapter 2 Oscillators for Timing Source 6 2.1 Barkhausen Criterion 7 2.2 TCXO . 9 2.2.1 TCXO Fundamentals . 10 2.2.2 TCXO Oscillator model 14 2.2.3 Pierce Oscillator Design Example . 19 2.2.4 TCXO in GNSS receivers . 23 2.3 MEMS Oscillator . 29 2.3.1 Electrostatic MEMS Oscillator model 33 Chapter 3 Environmental Test Results of Oscillators . 41 3.1 Oscillator Behavior under Environmental Stress . 43 3.1.1 Vibration and Acceleration Sensitivity 44 3.1.2 Temperature Sensitivity . 49 3.1.3 Pyrotechnic Shock . 56 3.2 Frequency Stability during the Temperature Test . 60 3.3 Frequency Stability during the Vibration Test 64 3.4 Frequency Stability in Pyrotechnic Shock Test 70 Chapter 4 Simulation with GNSS Receiver under Reference Frequency Change . 74 4.1 Tracking Loop of GNSS Receiver 75 4.2 GNSS Receiver Operation under the Change of Reference Frequency 86 4.3 False Frequency Lock 96 Chapter 5 Environmental Test Results of GNSS Receiver . 103 5.1 Navigation Performance during the Temperature Test . 105 5.2 Navigation Performance during the Vibration Test 108 5.3 Navigation Performance during the Pyrotechnic Shock Test 111 Chapter 6 Conclusion 115 Bibliography 117박

Ultra-High Frequency Nanoelectromechanical Systems with Low-Noise Technologies for Single-Molecule Mass Sensing

Advancing today's very rudimentary nanodevices toward functional nanosystems with considerable complexity and advanced performance imposes enormous challenges. This thesis presents the research on ultra-high frequency (UHF) nanoelectromechanical systems (NEMS) in combination with low-noise technologies that enable single-molecule mass sensing and offer promises for NEMS-based mass spectrometry (MS) with single-Dalton sensitivity. The generic protocol for NEMS resonant mass sensing is based on real-time locking and tracking of the resonance frequency as it is shifted by the mass-loading effect. This has been implemented in two modes: (i) creating an active self-sustaining oscillator based on the NEMS resonator, and (ii) a higher-precision external oscillator phase-locking to and tracking the NEMS resonance. The first UHF low-noise self-sustaining NEMS oscillator has been demonstrated by using a 428MHz vibrating NEMS resonator as the frequency reference. This stable UHF NEMS oscillator exhibits ~0.3ppm frequency stability and ~50zg (1zg = 10-21 g) mass resolution with its excellent wideband-operation (~0.2MHz) capability. Given its promising phase noise performance, the active NEMS oscillator technology also offers important potentials for realizing NEMS-based radio-frequency (RF) local oscillators, voltage-controlled oscillators (VCOs), and synchronized oscillators and arrays that could lead to nanomechanical signal processing and communication. The demonstrated NEMS oscillator operates at much higher frequency than conventional crystal oscillators and their overtones do, which opens new possibilities for the ultimate miniaturization of advanced crystal oscillators. Low-noise phase-locked loop (PLL) techniques have been developed and engineered to integrate with the resonance detection circuitry for the passive UHF NEMS resonators. Implementations of the NEMS-PLL mode with generations of low-loss UHF NEMS resonators demonstrate improving performance, namely, reduced noise and enhanced dynamic range. Very compelling frequency stability of ~0.02ppm and unprecedented mass sensitivity approaching 1zg has been achieved with a typical 500MHz device in the narrow-band NEMS-PLL operation. Retaining high quality factors (Q's) while scaling up frequency has become crucial for UHF NEMS resonators. Extensive measurements, together with theoretical modeling, have been performed to investigate various energy loss mechanisms and their effects on UHF devices. This leads to important insights and guidelines for device Q-engineering. The first VHF/UHF silicon nanowire (NW) resonators have been demonstrated based on single-crystal Si NWs made by bottom-up chemical synthesis nanofabrication. Pristine Si NWs have well-faceted surfaces and exhibit high Q's (Q ≈ 13100 at 80MHz and Q ≈ 5750 at 215MHz). Given their ultra-small active mass and very high mass responsivity, these Si NWs also offer excellent mass sensitivity in the ~10?50zg range. These UHF NEMS and electronic control technologies have demonstrated promising mass sensitivity for kilo-Dalton-range single-biomolecule mass sensing. The achieved performance roadmap, and that extended by next generations of devices, clearly indicates realistic and viable paths toward the single-Dalton mass sensitivity. With further elaborate engineering, prototype NEMS-MS is optimistically within reach.</p

Piezoelectric and Magnetoelastic Strain in the Transduction and Frequency Control of Nanomechanical Resonators

Stress and strain play a central role in semiconductors, and are strongly manifested at the nanometer-scale regime. Piezoelectricity and magnetostriction produce internal strains that are anisotropic and addressable via a remote electric or magnetic field. These properties could greatly benefit the nascent field of nanoelectromechanical systems (NEMS), which promises to impact a variety of sensor and actuator applications. The piezoelectric semiconductor GaAs is used as a platform for probing novel implementations of resonant nanomechanical actuation and frequency control. GaAs/AlGaAs heterostructures can be grown epitaxially, are easily amenable to suspended nanostructure fabrication, have a modest piezoelectric coefficient roughly twice that of quartz, and if appropriately doped with manganese, can form dilute magnetic compounds. In ordinary piezoelectric transducers there is a clear distinction between the metal electrodes and piezoelectric insulator. But this distinction is blurred in semiconductors. An integrated piezoelectric actuation mechanism is demonstrated in a series of suspended anisotype GaAs junctions, notably pin diodes. A dc bias was found to alter the resonance amplitude and frequency in such devices. The results are in good agreement with a model of strain based actuation encompassing the diode’s voltage-dependent carrier depletion width and impedance. A bandstructure engineering approach is employed to control the actuation efficiency by appropriately designing the doping level and thickness of the GaAs structure. Actuation and frequency are also sensitively dependent on the device’s crystallographic orientation. This combined tuning behavior represents a novel type of depletion-mediated electromechanical coupling in piezoelectric semiconductor nanostructures. All devices are actuated piezoelectrically, whereas three techniques are demonstrated for sensing: optical interferometry, piezoresistance and piezoelectricity. Finally, a nanoelectromechanical GaMnAs resonator is used to obtain the first measurement of magnetostriction in a dilute magnetic semiconductor. Resonance frequency shifts induced by field-dependent magnetoelastic stress are used to simultaneously map the magnetostriction and magnetic anisotropy constants over a wide range of temperatures. Owing to the central role of carriers in controlling ferromagnetic interactions in this material, the results appear to provide insight into a unique form of magnetoelastic behavior mediated by holes

Advances in Solid State Circuit Technologies

This book brings together contributions from experts in the fields to describe the current status of important topics in solid-state circuit technologies. It consists of 20 chapters which are grouped under the following categories: general information, circuits and devices, materials, and characterization techniques. These chapters have been written by renowned experts in the respective fields making this book valuable to the integrated circuits and materials science communities. It is intended for a diverse readership including electrical engineers and material scientists in the industry and academic institutions. Readers will be able to familiarize themselves with the latest technologies in the various fields