Piezoelectric aluminum nitride thin films for microelectromechanical systems

This article reports on the state-of-the-art of the development of aluminum nitride (AlN) thin-film microelectromechanical systems (MEMS) with particular emphasis on acoustic devices for radio frequency (RF) signal processing. Examples of resonant devices are reviewed to highlight the capabilities of AlN as an integrated circuit compatible material for the implementation of RF filters and oscillators. The commercial success of thin-film bulk acoustic resonators is presented to show how AlN has de facto become an industrial standard for the synthesis of high performance duplexers. The article also reports on the development of a new class of AlN acoustic resonators that are directly integrated with circuits and enable a new generation of reconfigurable narrowband filters and oscillators. Research efforts related to the deposition of doped AlN films and the scaling of sputtered AlN films into the nano realm are also provided as examples of possible future material developments that could expand the range of applicability of AlN MEM

Near 6 GHz Sezawa Mode Surface Acoustic Wave Resonators using AlScN on SiC

Surface Acoustic Wave (SAW) devices featuring Aluminum Scandium Nitride (AlScN) on a 4H-Silicon Carbide (SiC) substrate, offer a unique blend of high sound velocity, low thermal resistance, substantial piezoelectric response, simplified fabrication, as well as suitability for high-temperature and harsh environment operation. This study presents high-frequency SAW resonators employing AlScN thin films on SiC substrates, utilizing the second SAW mode (referred to as the Sezawa mode). The resonators achieve remarkable performance, boasting a K2 value of 5.5% and a maximum Q-factor (Qmax) of 1048 at 4.7 GHz, outperforming previous benchmarks. Additionally, a SAW resonator with a 960 nm wavelength attains 5.9 GHz frequency with record K2 (4.0%) and Qmax (887). Our study underscores the potential of the AlScN on SiC platform for advanced radio-frequency applications.Comment: 19 pages, 5 figures in main text and 3 figures in supplementar

Piezoelectric aluminum nitride thin films for microelectromechanical systems

This article reports on the state-of-the-art of the development of aluminum nitride (AlN) thin-film microelectromechanical systems (MEMS) with particular emphasis on acoustic devices for radio frequency (RF) signal processing. Examples of resonant devices are reviewed to highlight the capabilities of AlN as an integrated circuit compatible material for the implementation of RF filters and oscillators. The commercial success of thin-film bulk acoustic resonators is presented to show how AlN has de facto become an industrial standard for the synthesis of high performance duplexers. The article also reports on the development of a new class of AlN acoustic resonators that are directly integrated with circuits and enable a new generation of reconfigurable narrowband filters and oscillators. Research efforts related to the deposition of doped AlN films and the scaling of sputtered AlN films into the nano realm are also provided as examples of possible future material developments that could expand the range of applicability of AlN MEMS

Frequency Tunable Magnetostatic Wave Filters With Zero Static Power Magnetic Biasing Circuitry

A single tunable filter can reduce the complexity, loss, and size when compared to switchable filter banks and enable new applications. Although magnetostatic wave tunable filters offer broad and continuous frequency tuning and high-quality factor (Q-factor), they consume high power and require large electromagnets to alter the magnetostatic wave velocity for filter frequency tuning. Here, we demonstrate miniature and high selectivity magnetostatic wave tunable filters with zero static power realized in Yttrium Iron Garnet thin films. The center frequency can be tuned via current pulses applied to a magnetic bias assembly from 3.36 GHz to 11.09 GHz with an insertion loss of 3.2 dB to 5.1 dB and out-of-band third order input intercept point (IIP3) of 41 to 44 dBm. Overall, the adaptability, wide frequency tuning range, and zero static power consumption of the tunable filter position it as a critical technology, effectively addressing challenges in broadband ADCs, RF transceivers, broadband digital phased array antennas, and interference mitigation in 5G and 6G networks. Broadly frequency tunable, high selectivity filters open new avenues for more efficient and dynamic RF front ends, ensuring optimal performance and seamless communication in the ever-evolving landscape of modern wireless technologies.Comment: The main manuscript contains 6918 words and 5 figures comprising 15 panels in total. The supplementary document consists of 14 Supplementary Notes and 30 Supplementary Figure

Non-Volatile Control of Valley Polarized Emission in 2D WSe2-AlScN Heterostructures

Achieving robust and electrically controlled valley polarization in monolayer transition metal dichalcogenides (ML-TMDs) is a frontier challenge for realistic valleytronic applications. Theoretical investigations show that integration of 2D materials with ferroelectrics is a promising strategy; however, its experimental demonstration has remained elusive. Here, we fabricate ferroelectric field-effect transistors using a ML-WSe2 channel and a AlScN ferroelectric dielectric, and experimentally demonstrate efficient tuning as well as non-volatile control of valley polarization. We measured a large array of transistors and obtained a maximum valley polarization of ~27% at 80 K with stable retention up to 5400 secs. The enhancement in the valley polarization was ascribed to the efficient exciton-to-trion (X-T) conversion and its coupling with an out-of-plane electric field, viz. the quantum-confined Stark effect. This changes the valley depolarization pathway from strong exchange interactions to slow spin-flip intervalley scattering. Our research demonstrates a promising approach for achieving non-volatile control over valley polarization and suggests new design principles for practical valleytronic devices.Comment: Manuscript (22 pages and 5 figures), supporting informatio

Scalable and Stable Ferroelectric Non-Volatile Memory at > 500 ∘^\circC

Non-volatile memory (NVM) devices that reliably operate at temperatures above 300 $^\circ$C are currently non-existent and remains a critically unmet challenge in the development of high-temperature (T) resilient electronics, necessary for many emerging, complex computing and sensing in harsh environments. Ferroelectric Al$_x$Sc$_{1-x}$N exhibits strong potential for utilization in NVM devices operating at very high temperatures (> 500 $^\circ$C) given its stable and high remnant polarization (PR) above 100 $\mu$C/cm$^2$ with demonstrated ferroelectric transition temperature (TC) > 1000 $^\circ$C. Here, we demonstrate an Al$_{0.68}$Sc$_{0.32}$N ferroelectric diode based NVM device that can reliably operate with clear ferroelectric switching up to 600 $^\circ$C with distinguishable On and Off states. The coercive field (EC) from the Pulsed I-V measurements is found to be -5.84 (EC-) and +5.98 (EC+) (+/- 0.1) MV/cm at room temperature (RT) and found to decrease with increasing temperature up to 600 $^\circ$C. The devices exhibit high remnant polarizations (> 100 $\mu$C/cm$^2$) which are stable at high temperatures. At 500 $^\circ$C, our devices show 1 million read cycles and stable On-Off ratio above 1 for > 6 hours. Finally, the operating voltages of our AlScN ferrodiodes are < 15 V at 600 $^\circ$C which is well matched and compatible with Silicon Carbide (SiC) based high temperature logic technology, thereby making our demonstration a major step towards commercialization of NVM integrated high-T computers.Comment: MS and S

Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector

The observation of Higgs boson production in association with a top quark pair (tt H¯ ), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb−1, and considering Higgs boson decays into b¯ b, W W ∗, τ +τ −, γγ , and Z Z∗, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the tt H¯ searches using a dataset corresponding to integrated luminosities of 4.5 fb−1 at 7 TeV and 20.3 fb−1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total tt H¯ production cross section at 13 TeV is measured to be 670 ± 90 (stat.) +110 −100 (syst.) fb, in agreement with the Standard Model prediction

Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.

Silicon recording arrays with integrated circuitry for in-vivo neural data compression.

This thesis presents the design, testing, implantation and limitations of neural recording arrays with integrated CMOS circuitry. A fully-implantable 3D neural recording microsystem has been developed that features site selection, amplification, time-division multiplexing, and spike detection circuitry. The fundamental limits and tradeoffs involving size, power consumption, multiplexer speed, quantization noise, spike detection and discrimination, and neural data compression have been analyzed and presented. The 256-site 3D microsystem is capable of recording up to 32 channels of simultaneous neural signals at a data rate that is compatible with current transcutaneous telemetry platforms. A capacitively-coupled neural recording amplifier has been developed to solve the do baseline stabilization problem. The amplifier uses subthreshold NMOS transistors with an incremental resistance of greater than 10 10 O to realize an integrated high-pass filter below 100Hz while providing an in-band gain of 39dB. The amplifier has a high-frequency cutoff of 9.9kHz for anti-aliasing, and the low-frequency cutoff of the amplifier is tunable. The total integrated noise of the amplifier from 100Hz to 10kHz is 9.2muVrms, which is lower than that of a 165mm2 iridium electrode in saline. The amplifier consumes 84muW of power from +/-1.5V supplies and occupies 0.177mm2 in 3mum features. The performance of this amplifier has been evaluated during hundreds of hours of in-vivo experiments. This thesis presents amplified, time-division-multiplexed neural recordings for the first time. The design and limitations of time-division multiplexers are presented including the tradeoffs among supply scaling, load capacitance, sampling frequency, and number of channels. The current multiplexer design samples 8 neural channels onto a single output lead at a sampling frequency of 20kHz/channel. A spike detection ASIC has been developed to compress the neural data in-vivo, allowing hundreds of channels to be recorded simultaneously over a wireless interface. The spike detector successfully detects neural spikes in the presence of neural and circuit noise and achieves a bandwidth savings of 92% while still preserving the key features of the waveshape necessary for spike discrimination. When a spike is detected, this ASIC serially shifts the 5-bit amplitude and 5-bit address of the spike off of the chip over a single data lead at 2.5Mbps. The spike detection ASIC occupies 2mm x 3mm in 0.5mum features and consumes 2.6mW of power from a 3V supply. Tradeoffs in terms of power consumption and circuit area to improve the performance of the spike detection ASIC are presented.Ph.D.Applied SciencesBiological SciencesBiomedical engineeringElectrical engineeringNeurosciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124278/2/3137911.pd

Research on micro-sized acoustic bandgap structures.

Phononic crystals (or acoustic crystals) are the acoustic wave analogue of photonic crystals. Here a periodic array of scattering inclusions located in a homogeneous host material forbids certain ranges of acoustic frequencies from existence within the crystal, thus creating what are known as acoustic (or phononic) bandgaps. The vast majority of phononic crystal devices reported prior to this LDRD were constructed by hand assembling scattering inclusions in a lossy viscoelastic medium, predominantly air, water or epoxy, resulting in large structures limited to frequencies below 1 MHz. Under this LDRD, phononic crystals and devices were scaled to very (VHF: 30-300 MHz) and ultra (UHF: 300-3000 MHz) high frequencies utilizing finite difference time domain (FDTD) modeling, microfabrication and micromachining technologies. This LDRD developed key breakthroughs in the areas of micro-phononic crystals including physical origins of phononic crystals, advanced FDTD modeling and design techniques, material considerations, microfabrication processes, characterization methods and device structures. Micro-phononic crystal devices realized in low-loss solid materials were emphasized in this work due to their potential applications in radio frequency communications and acoustic imaging for medical ultrasound and nondestructive testing. The results of the advanced modeling, fabrication and integrated transducer designs were that this LDRD produced the 1st measured phononic crystals and phononic crystal devices (waveguides) operating in the VHF (67 MHz) and UHF (937 MHz) frequency bands and established Sandia as a world leader in the area of micro-phononic crystals