Naval Research Laboratory Research Articles

Interplanetary Influence on Thermospheric Mass Density: Insights From Deep Learning Analyses

AbstractIn this study, the thermospheric mass density (TMD) features observed by the CHAllenging Minisatellite Payload between 2002 and 2010 were extracted using deep learning (DL) technology; the TMD features were then mapped and modeled with the Interplanetary environment information (IEI), solar radiation, and geomagnetic indices. The DL model was used to simulate the TMD features during Day of Year (DOY) 222–241 in 2014, a period that experienced complex solar‐terrestrial environmental variations. We explore the TMD features under different solar‐terrestrial environmental conditions and discuss the effects of various inputs by comparing the DL simulation results with satellite observations from Gravity Recovery and Climate Experiment‐A and Swarm‐A, as well as the simulation results from Jacchia‐Bowman 2008, Naval Research Laboratory Mass Spectrometer Incoherent Scatter radar model 2.1, and Drag Temperature Model 2013. These results show that the DL model can better capture the TMD features after adding IEI. Part of these TMD features, including the high‐latitude TMD enhancement during the space hurricane event (DOY 232, 2014) and global TMD variations under complex solar‐terrestrial environmental disturbances (DOY 222–225, 2014), cannot be well described by the geomagnetic indices. The DL model indicates that the east‐west component of the interplanetary magnetic field (IMF By) has a great impact on TMD variations, and its modulation is different from the typical energy injection process during storms. Our results emphasize the crucial influence of IEI on TMD under both geomagnetic disturbances and quiet conditions.

A complete electrode model for plasma impedance probes

Plasma impedance probes measure the impedance spectrum of an antenna immersed in a plasma. The 1964 work of Balmain remains the standard method to interpret these data, using the peak in the magnitude at the upper-hybrid frequency to infer plasma electron density. The primary limitations of Balmain's model are the assumption of a homogenous plasma and a cylindrical dipole. This work presents a numerical model applicable to inhomogeneous plasma and arbitrary antenna geometry based on the cold, fluid approximation given by Balmain. This model solves Poisson's equation using the finite element method and accounts for the effects of the dipole using the plasma complete electrode model (PCEM). The PCEM is developed in this article and accounts for the voltage shunting effects of the dipole elements, the discrete current to the dipole, and the plasma sheath surrounding the dipole. The sheath is incorporated as a contact impedance between the dipole and the plasma in a manner analogous to the complete electrode model of electrical impedance tomography. The first portion of this paper presents the mathematical framework of the PCEM, starting from Maxwell's equations. The second part of the paper compares the output of this numerical method to Balmain's work and to data collected by an impedance probe in the Space Physics Simulation Chamber at the U.S. Naval Research Laboratory. The PCEM results agree with both the observed data and the prior modeling done by Balmain. An additional consequence of the numerical study is the observation that some second-order resonances not predicted by Balmain's model can be attributed to the presence of the plasma sheath.

Rapid detection of incipient foil failure and remediation for longevity in repetitively pulsed, electron-beam-pumped excimer lasers for fusion research.

The use of an electron beam to pump an excimer laser has the advantage of being readily scalable to higher laser energies at high efficiency. Typically, a pulsed power driver generates the electron beam in a vacuum diode that consists of an electron emitter and a thin anode foil that holds the vacuum against the atmospheric-pressure laser gas. Even a miniscule leak in the anode foil can lead to an electrical breakdown in the vacuum diode, resulting in the destruction of the foil and evidence of the failure mechanism. The problem is even more onerous at the high voltage, high current, and pulse repetition frequencies needed for the large-area diodes used in excimer lasers for fusion research. Electra is one such laser used at the Naval Research Laboratory to develop excimer laser technologies for inertial fusion energy. To achieve longevity on Electra, it was necessary to instantly detect an incipient foil failure and halt the pulsed power drivers so the physical cause(s) could be studied. This rapid detection was accomplished using an optically filtered photodiode that senses the presence of argon emission from a Penning discharge vessel attached to the vacuum diodes. Details of this "Spectral Penning Leak Detector" device and its operation are presented. The diagnostics allowed the identification of a recurrent pinhole leak in the anode foil induced by cathode spots, which were created by electron emission from the foil during post-pulse voltage reversals. Eliminating the voltage reversals increased the continuous operation of the Electra laser from hundreds of shots to over 90 000 shots.

The Feature Analysis and Modeling of Upper Atmospheric Midnight Density Maximum

The features of upper atmospheric midnight density maximum (MDM) around low geographic latitudes are studied based on neutral mass densities data at altitudes 360–480 km, derived from the accelerometer measurements aboard on the three polar orbiting satellites CHAMP (CHAllenging Minisatellite Payload), GRACE-A (Gravity Recovery and Climate Experiment-A), and SWARM-C (The Earth's Magnetic Field and Environment Explorers-C). The MDM appears during the local times from 23:00 to 02:00 LT (Local Time), whose peak locates at the low latitudes within 15∘ and two valleys locate at the middle latitudes between 35∘ and 45∘ on both hemispheres separately. The structure of MDM drifts toward the southern hemisphere overall. The MDM's amplitude decreases with increases in altitude and solar radiation level. The seasonal effect weakens the MDM's amplitudes around the summer and winter solstices, while the amplitudes around the spring and autumn equinoxes are extremely significant due to the slight seasonal difference between both hemispheres. Three atmospheric density models DTM2000 (Drag Temperature Model 2000), NRLMSISE00 (US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar Extended atmosphere model), and JB2008 (Jacchia-Bowman 2008 model) are used to simulate the MDM along these three satellites' orbits, and compared with the observations. It is found that the JB2008 model is failed to describe the MDM, and the other two models underestimate the MDM's amplitudes at altitudes 360 km and 480 km: the simulated amplitudes by the DTM2000 model are 46% and 53% of the observed amplitudes, respectively, and only 33% and 26% for the NRLMSISE00 model. These three models are also failed to depict the MDM's variation with altitude, solar radiation level, and seasonal effects. In order to correct the model prediction, a 6th-order Legendre polynomial of geographic latitude, coupled with arguments of local time and altitude, is designed to fit the MDM signals from the three satellites' observations. In terms of amplitude and phase of the MDM, the fitting results agree with the observations very well, and the correlation coefficient is 0.923. It indicates that this empirical polynomial could be helpful to the density model correction and high accuracy prediction of spacecrafts in low Earth orbits.

ANCHOR: Global Parametrized Ionospheric Data Assimilation

AbstractANCHOR is a novel assimilative model developed at the U.S. Naval Research Laboratory, which was designed for rapid assimilative runs. ANCHOR uses recently developed PyIRI model for the background and for the formation of the background covariance matrix. It only takes a few minutes for ANCHOR to complete the data assimilation (DA) for one day, including data pre‐processing and model set up. ANCHOR extracts ionospheric parameters from radio occultation (RO) and ionosonde data using PyIRI formalism and assimilates them as point measurements into maps of the background parameters using a Kalman Filter approach. This paper introduces the ANCHOR algorithm, discusses its coordinate system and background, explains the background covariance formation, discusses the extraction of the ionospheric parameters from the data and the assimilation process, and, finally, shows the results of the observing system simulation experiment with synthetic data simulated using the SAMI3 model. ANCHOR reduces the root mean square errors in the analysis by more than a half for all of the ionospheric parameters in comparison to the background. Finally, this paper discusses advantages and limitations of the parametrized ionospheric DA, highlighting the avenues for its future improvement.

On the importance of middle-atmosphere observations on ionospheric dynamics using WACCM-X and SAMI3

Abstract. Recent advances in atmospheric observations and modeling have enabled the investigation of thermosphere–ionosphere interactions as a whole-atmosphere problem. This study examines how dynamical variability in the middle atmosphere (MA) affects intra-day changes in the thermosphere and ionosphere. Specifically, this study investigates ionosphere–thermosphere interactions during different time periods of January 2013 using the Specified Dynamics Whole Atmosphere Community Climate Model, eXtended version (SD-WACCM-X), coupled to the Naval Research Laboratory (NRL) ionosphere of the Sami3 is Another Model of the Ionosphere (SAMI3) model. To represent the weather of the day, the coupled thermosphere–ionosphere system is nudged below 90 km toward the atmospheric specifications provided by the Navy Global Environmental Model for High-Altitude (NAVGEM-HA). Hindcast simulations during January 2013 are carried out with the full dataset of observations normally assimilated by NAVGEM-HA and with a degraded dataset where observations above 40 km are not assimilated. Ionospheric regions with statistically significant changes are identified using key ionospheric properties, including the electron density, peak electron density, and height of the peak electron density. Ionospheric changes show a spatial structure that illustrates the impact of two different types of coupling between the thermosphere and the ionosphere: variability induced by wind-dynamo coupling through electric conductivity and ion-neutral interactions in the upper thermosphere. The two simulations presented in this study show that changing the state of the MA affects ionosphere–thermosphere coupling through changes in the behavior and amplitude of non-migrating tides, resulting in improved key ionospheric specifications.

Intercomparison of aerosol optical depths from four reanalyses and their multi-reanalysis consensus

Abstract. The emergence of aerosol reanalyses in recent years has facilitated a comprehensive and systematic evaluation of aerosol optical depth (AOD) trends and attribution over multi-decadal timescales. Notable multi-year aerosol reanalyses currently available include NAAPS-RA from the US Naval Research Laboratory, the NASA MERRA-2, JRAero from the Japan Meteorological Agency (JMA), and CAMSRA from Copernicus/ECMWF. These aerosol reanalyses are based on differing underlying meteorology models, representations of aerosol processes, as well as data assimilation methods and treatment of AOD observations. This study presents the basic verification characteristics of these four reanalyses versus both AERONET and MODIS retrievals in monthly AOD properties and identifies the strength of each reanalysis and the regions where divergence and challenges are prominent. Regions with high pollution and often mixed fine-mode and coarse-mode aerosol environments, such as South Asia, East Asia, Southeast Asia, and the Maritime Continent, pose significant challenges, as indicated by higher monthly AOD root mean square error. Moreover, regions that are distant from major aerosol source areas, including the polar regions and remote oceans, exhibit large relative differences in speciated AODs and fine-mode versus coarse-mode AODs among the four reanalyses. To ensure consistency across the globe, a multi-reanalysis consensus (MRC, i.e., ensemble mean) approach was developed similarly to the International Cooperative for Aerosol Prediction Multi-Model Ensemble (ICAP-MME). Like the ICAP-MME, while the MRC does not consistently rank first among the reanalyses for individual regions, it performs well by ranking first or second globally in AOD correlation and RMSE, making it a suitable candidate for climate studies that require robust and consistent assessments.

Bio-Optical Properties near a Coastal Convergence Zone Derived from Aircraft Remote Sensing Imagery and Modeling

Bio-optical and physical measurements were collected in the Mississippi Sound (Northern Gulf of Mexico) during the spring of 2018 as part of the Integrated Coastal Bio-Optical Dynamics project. The goal was to examine the impact of atmospheric and tidal fronts on fine-scale physical and bio-optical property distributions in a shallow, dynamic, coastal environment. During a 25-day experiment, eight moorings were deployed in the vicinity of a frontal zone. For a one-week period in the middle of the mooring deployment, focused ship sampling was conducted with aircraft and unmanned aerial vehicle overflights, acquiring hyperspectral optical and thermal data. The personnel in the aircraft located visible color fronts indicating the convergence of two water masses and directed the ship to the front. Dye releases were performed on opposite sides of a front, and coincident aircraft and unmanned aerial vehicle overflights were collected to facilitate visualization of advection/mixing/dispersion processes. Radiometric calibration of the optical hyperspectral sensor was performed. Empirical Line Calibration was also performed to atmospherically correct the aircraft imagery using in situ remote sensing reflectance measurements as calibration sources. Bio-optical properties were subsequently derived from the atmospherically corrected aircraft and unmanned aerial vehicle imagery using the Naval Research Laboratory Automated Processing System.

Nitric Oxide Concentration: A New Data Set Derived From SABER Measurements

AbstractVertical profiles of nitric oxide (NO) concentration are derived between 120 and 250 km using updated NO emission rates measured by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. The Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar (MSIS) 2.1 model is used to provide the required parameters of temperature, atomic oxygen number density, and molecule oxygen number density needed to derive the NO concentrations using a non‐local thermodynamic equilibrium (non‐LTE) model. The SABER NO concentration shows a significant correlation with solar activity with larger peak NO concentrations and higher altitude extent during solar maximum years compared to those during the solar minimum years. The SABER NO agrees well with the MSIS 2.1 NO at altitudes above 120 km for all latitudes, while the pronounced SABER‐MSIS NO discrepancy below 120 km is likely due to the temperature underestimation by MSIS 2.1. A detailed error analysis is presented and considers systematic and random errors in all the terms in the non‐LTE model used to derive the NO concentration. Random error in MSIS 2.1 temperature and atomic oxygen dominates the uncertainty in single NO profiles above 120 km. We estimated a systematic error up to ∼36% between 120 and 250 km during solar maximum years.

Investigation of Atmospheric Anomalies due to the Great Tohoku Earthquake Disturbance Using NRLMSISE-00 Atmospheric Model Measurement

In this study, the atmospheric changes for the 9.0-magnitude Tohoku earthquake, which occurred on March 11, 2011, are analyzed. The March 11, 2011 earthquake was preceded by a large foreshock on March 09, 2011 with magnitude M 7.3 and depth 32 km at 02:45:20 UT near the east coast of Honshu, Japan. The earthquake doesn’t limit its effects on the Earth’s lithosphere, hydrosphere and biosphere; it also extends its effects to the atmosphere because of the gas emissions, which produce large-scale seismic waves from the ground and release gases into the atmosphere. In this study, the anomalies of the atmospheric parameters are studied by using one of the atmospheric models from the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Extension 2000 (NRLMSISE-00) model data to analyze the atmospheric anomalies of the Tohoku Earthquake on March 11, 2011. The atmospheric parameters of atomic oxygen (O), hydrogen (H), atomic nitrogen (N), helium (He), argon (Ar), molecular oxygen (O2), molecular nitrogen (N2), total mass density (ρ), neutral temperature (Tn), exospheric temperature (Tex) and anomalous oxygen (AO) are used for analysis during the earthquake occurrence. The epicenter of the Tohoku earthquake, with a geographical location of latitude 38.30° N and longitude 142.37° E, is used for the NRLMSISE-00 model as input parameters to analyze the output of atmospheric parameters. To compare the atmospheric changes caused by the earthquake, 5 days before and after the earthquake are considered. To detect where the atmospheric parameters increased or decreased from the earthquake day, the percentage deviation of the NRLMSISE-00 model is applied. The results indicate that there were atmospheric parameter anomalies that occurred a few days before, following and during the earthquake on March 11, 2011. Except for hydrogen (H), all atmospheric parameters average daily percentage deviation values were positive during the 5 days before and after with respect to the main earthquake shock on March 11, 2011. The NRLMSISE-00 model can capture the atmospheric parameter anomalies of the Tohoku earthquake well.

Inner Front Cover Image

ON THE INNER FRONT COVER: Hs27 fibroblasts stained for Vinculin (green) and F‐actin/phalloidin (red) on etched grooved quartz, illustrating the concept of a focal adhesion confinement mechanism in contact guidance at shallow groove depths.Credit: Jinny L. Liu & Michael C. Robitaille (U.S. Naval Research Laboratory, USA) image

PyIRI: Whole‐Globe Approach to the International Reference Ionosphere Modeling Implemented in Python

AbstractThe International Reference Ionosphere (IRI) model is widely used in the ionospheric community and considered the gold standard for empirical ionospheric models. The development of this model was initiated in the late 1960s using the FORTRAN language; for its programming approach, the model outputs were calculated separately for each given geographic location and time stamp. The Consultative Committee on International Radio (CCIR) and International Union of Radio Science (URSI) coefficients provide the skeleton of the IRI model, as they define the global distribution of the maximum useable ionospheric frequency foF2 and the propagation factor M(3,000)F2. At the U.S. Naval Research Laboratory, a novel Python tool was developed that enables global runs of the IRI model with significantly lower computational overhead. This was made possible through the Python rebuild of the core IRI component (which calculates ionospheric critical frequency using the CCIR or URSI coefficients), taking advantage of NumPy matrix multiplication instead of using cyclic addition. This paper explains in detail this new approach and introduces all components of the PyIRI package.

Inner Back Cover Image

ON THE INNER BACK COVER: Hs27 fibroblasts stained for Vinculin (green) and F‐actin/phalloidin (red) on etched grooved quartz, illustrating the concept of a focal adhesion confinement mechanism in contact guidance at shallow groove depths.Credit: Jinny L. Liu & Michael C. Robitaille (U.S. Naval Research Laboratory, USA) image

A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

The Sun plays a role in influencing Earth’s climate, making it important to have accurate information about variations in the Sun’s radiative output. Models are used to recover total solar-irradiance (TSI) variations in the past when direct space-based measurements are not available. One of the most cryptic such TSI reconstructions is the one by Hoyt and Schatten (J. Geophys. Res. 98, 18, 1993, HS93). The rather vague description of the model methodology, the arbitrary selection of solar indices it employs, and the short overlap between the HS93 series and directly measured TSI values has hindered any evaluation of the performance of this model to this day. Here, we aim at rectifying this by updating the HS93 model with new input data. In this way we are also contributing in the discussion on the possible long-term changes in solar irradiance.We find that the analysis by HS93 included a number of erroneous processing steps that led to an artificial increasing trend towards the end of the reconstructed TSI series as well as shifting the peak of the TSI in the mid-twentieth century back in time by about 11 years. Furthermore, by using direct measurements of the TSI we determined that the free parameter of the model, the magnitude of variations (here defined as percentage variations of the difference between the maximum to minimum values), is optimal when it is minimised (being ≤0.05%). This is in stark contrast to the high magnitude of variations, of 0.25%, that was imposed by HS93. However, our result is consistent with more recent estimates, such as those from the Spectral And Total Irradiance REconstruction (SATIRE) model and Naval Research Laboratory TSI (NRLTSI), which were used by the Intergovernmental Panel on Climate Change (IPCC). Overall, we find that the previously reported agreement of the HS93 TSI series to temperature on Earth was purely due to improper analysis and artefacts of the processing.

Synchrotron Capabilities in a Laboratory Setting: In Situ X-Ray Absorption Spectroscopy of Disordered Vanadium Ferrite Electrodes for Lithium-Ion Batteries

X-ray absorption spectroscopy (XAS) provides important information on metal oxidation state andelement-specific coordination, but data collection has historically required the energy specificityand brilliance of a synchrotron facility. Recent developments in detectors and optics are nowbringing XAS capabilities to the laboratory setting through multiple commercially availableinstruments. At the U.S. Naval Research Laboratory, we use laboratory-based XAS to explore thelocal electronic and atomic structure of a class of disordered vanadium ferrite (VFe2Ox) aerogelsthat exhibit promising performance for electrochemical energy-storage applications such asrechargeable lithium-ion batteries.1,2 These materials are synthesized by an epoxide-promoted sol–gel reaction of iron chloride and vanadium isopropoxide, with the resulting fluid-filled gelsrendered as high surface area aerogels via supercritical-CO2 drying. During the initial sol–gelsynthesis, electroinactive metals such as aluminum, zinc, and zirconium may also be substitutedfor vanadium and iron to alter the local electronic environment and corresponding electrochemicalperformance of VFe2Ox. Heat treatment of as-dried VFe2Ox aerogels under either O2-containingor inert atmosphere yields disordered or nanocrystalline variants, respectively. The resulting seriesof native and substituted VFe2Ox materials are evaluated as powder-composite cathodes versuslithium metal in coin cells with conventional nonaqueous lithium-ion electrolyte. We correlatesuch critical battery-performance parameters as total specific capacity, high-rate capability, andcycle life as a function of VFe2Ox composition and its degree of structural order/disorder, asmeasured with in-situ XANES and EXAFS. In parallel with experimental observations,calculations on VFe2Ox reveal that V incorporates into the defective spinel structure at tetrahedralsites and that both disorder induced by vacancies and Fe/V tetrahedral occupation lowers theoverall energy and opens an electronic energy gap that establishes the redox sequence duringlithiation.1. C. N. Chervin, J. S. Ko, B. W. Miller, L. Dudek, A. N. Mansour, M. D. Donakowski, T.Brintlinger, P. Gogotsi, S. Chattopadhyay, T. Shibata, J. F. Parker, B. P. Hahn, D. R. Rolison,and J. W. Long, J. Mater. Chem. A 3, 12059 (2015).2. C. N. Chervin, R. H. DeBlock, J. F. Parker, B. M. Hudak, N. L. Skeele, J. S. Ko, D. R. Rolison,and J. W. Long, RSC Adv. 11, 14495 (2021).

Designing Architected Nickel Hydroxide Cathodes for Rechargeable Alkaline Nickel–Zinc Batteries

Now that dendrite-suppressing Zn sponge anodes developed at the U.S. Naval Research Laboratory [1] offer a safer route to aqueous batteries that can power a wide range of end uses including electric vehicles, portable electronic devices, and backup energy storage, we need better cathodes. With high rate capability and deep theoretical utilization of the zinc (DOD ≥ 40%) now routine in alkaline electrolytes, storing and delivering more than one electron per metal-centered active material in the cathode is next. We focus on moving the Ni cathode past the 0.8–0.9 electrons per Ni characteristic of fabricating the cathode using β-Ni(OH)2 to tap the extra capacity inherent to α-Ni(OH)2 (theoretical: 1.67 electrons/Ni). Substituting Al3+ into α-Ni(OH)2 stabilizes the alpha phase from conversion to beta phase upon contact with and cycling in aqueous KOH and shifts positive the cell voltage for oxygen evolution (OER), the parasitic charging reaction that affects coulombic efficiency and limits cycle life [2]. We have now redesigned a classic powder composite Ni cathode (carbon black + Ni(OH)2 + binder) into an architected Ni electrode to improve charging efficacy. Using microwave-assisted deposition of Al-substituted α-Ni(OH)2 nanosheets onto a freestanding carbon nanofiber paper electrode wires the active material in 3D to the current-collecting carbon throughout the volume of the electrode. The architected Ni cathodes are tested in alkaline cells versus zinc sponge anodes and demonstrate that architected electron-wiring improves the capacity, rate, and cycle stability of Ni cathodes relative to conventional powder-composite electrodes. Varying the synthetic conditions achieves mass loadings that approach technologically relevant values. The enhanced electrochemical performance of architected Ni cathodes and architected Zn anodes provides a pathway to energy dense, safe, rechargeable Ni–Zn batteries.[1] Parker, J.F.; Chervin, C.N.; Pala, I.R.; Machler, M.; Burz, M.F.; Long, J.W.; Rolison, D.R. Rechargeable Nickel–3D Zinc Batteries: An Energy-Dense, Safer Alternative to Lithium-Ion. Science 2017, 356, 415–418 (10.1126/science.aak9991).[2] Kimmel, S.W.; Hopkins,B.J.; Chervin, C.N.; Skeele, N.L.; Ko, J.S.; DeBlock, R.H.; Long, J.W.; Parker, J.F.; Hudak, B.M.; Stroud, R.M.; Rolison, D.R.;Rhodes, C.P.Capacity and Phase Stability of Metal-Substituted α-Ni(OH)₂ Nanosheets in Aqueous Ni–Zn Batteries. Mater. Adv. 2021, 2, 3060–3074 (10.1039/D1MA00080B).

3D Silver Sponge Electrodes for High-Rate Faradaic Deionization of High-Salinity Waters

The availability of potable water is a growing global challenge that requires implementing water-purification technologies across a range of production scales from municipal systems to personal, distributed use. Reverse osmosis effectively desalinates high-salinity waters (e.g., undiluted seawater) at large scale, yet may be less suited to small-scale use due to the high-pressure pumps and regular maintenance required for operation. Capacitive deionization (CDI) utilizes high-surface-area carbon electrodes that can offer a more down-scalable desalination approach, but the relatively low capacity of double-layer storage mechanisms limits their use to low-salinity input (brackish water). Alternatively, faradaic deionization (FDI) materials that exhibit redox mechanisms for ion storage present an opportunity to displace reverse-osmosis systems in small-scale desalination systems. As one example, the redox reaction, Ag(s) + Cl–(aq) ↔ AgCl(s) + e–, can be exploited for Cl– capture in desalination cells that pair Ag/AgCl electrodes separated by a cation exchange membrane.1,2 We use macroporous silver “sponges” developed at the U.S. Naval Research Laboratory as millimeters-thick flow-through electrodes that show practical salt absorption capacities >100 mg/g while maintaining high salt removal rate courtesy of this kinetically facile conversion reaction. We investigate different silver sponge architectures and their effect on desalination throughput (L/m2/h) and energy consumption (Wh/L) for inputs up to seawater-level salinity using a custom computer-controlled batch-testing system. These readily fabricated, scalable Ag sponges serve as an attractive archetype electrode for high-performance faradaic desalination. 1 P. Srimuk, S. Husmann, and V. Presser, RSC Adv., 2019, 9, 14849–14858. 2 J. Ahn, J. Lee, S. Kim, C. Kim, J. Lee, P.M. Biesheuvel, and J. Yoon, Desalination, 2020, 476, 114216.

Towards Controlled Transfer of (001) β-Ga2O3 to (0001) 4H-SiC Substrates

We demonstrate successful blistering of He-implanted (001) β-Ga2O3, bonding to (0001) 4H-SiC, and initial results towards large-area transfer of (001) β-Ga2O3 to 4H-SiC. Compatible with large-scale processing, exfoliation is an important step in controlled-thickness transfer of films for heterogeneous integration. Furthermore, integration of β-Ga2O3 to high thermal conductivity materials will be crucial for thermal management of β-Ga2O3-based power devices. Two-inch (001) β-Ga2O3 wafers were implanted with He+ at an energy of 160 keV and a dose of 5×1016 cm-2, which are the same implant parameters used previously to successfully exfoliate (010) β-Ga2O3.1 Strain fringes were observed after the implant which corresponded to a maximum strain of ~1.7%, which is higher than the ~1% strain when implanting (010) β-Ga2O31 likely due to the larger Poisson’s ratio of (001) β-Ga2O3.2 The implanted substrates were then bonded to (0001) 4H-SiC at room temperature using a ~5 nm thin Ti interlayer to assist with the bond. Both unbonded implanted substrates and the bonded structures were first annealed at 200 °C for 10 hours to simultaneously initiate He bubble nucleation at the implanted projected range (~0.68 μm) and strengthen the bond. Then, even after annealing at 500 °C for 10 hours to initiate He bubble growth, the (001) β-Ga2O3 did not transfer to the (0001) 4H-SiC. Unlike what was observed for (010) β-Ga2O3,1 blistering did not even occur at this temperature. Annealing at 800 °C for up to 12 hours resulted in ~10 μm blisters for the unbonded substrates, which is typically an indication that large wafer-area transfer can be achieved if bonding was done prior to annealing.3 However, the β-Ga2O3 substrate did not wafer split from the bonded structure, and instead only small area transfers up to ~200 μm were achieved. Only ~7% of the total bonded area transferred while the entire structure remained bonded. Strategies to improve transfer will be presented, including initiating a cold split prior to exfoliation and refined annealing strategies to improve He bubble nucleation and larger bubble growth at the projected range. These are promising results towards achieving large wafer-scale (001) β-Ga2O3 composite wafers, and when combined with subsurface damage-free chemical mechanical polishing,4 these composite wafers would be suitable for subsequent devices and/or epitaxial growth.The authors would like to acknowledge the support from the Office of Naval Research through a MURI program, grant No. N00014-18-1-2429. This research was performed while M.E.L. and J.S.L. held an NRC Research Associateship award at the U.S. Naval Research Laboratory.References M.E. Liao, et al., ECS J. Solid State Sci. Technol., 8(11), P673 (2019).K. Adachi, et al., J. Appl. Phys., 124, 085102 (2018).M. Bruel, et al., Jpn. J. Appl. Phys., 36, 1636 (1997).M.E. Liao, et al., J. Vac. Sci. Technol. A, 41, 013205 (2023). Figure 1

Micr -Transfer Printing for Efficient 3DHI of 100-300mm Wafers and Glass Panels

This paper presents an analysis of using micro-transfer printing (MTP) for three-dimensional heterogeneous integration (3DHI) of diverse components made using 100mm, 200mm and 300mm wafers with large area glass substrates. Techniques for achieving high throughput and high wafer and substrate utilization, despite their size mis-matches, are described in detail along with MTP’s pros and cons versus alternative wafer-to-wafer and die-to-wafer 3DHI technologies. MTP, a massively parallel pick-and-place process, efficiently transfers large arrays of ultra-thin (<10 micron), small, diverse components (“x-chips”) from one or more source wafers to destination substrates. MTP enables disruptive 3DHI of compound semiconductors, including GaN, GaAs, InP, SiGe and emerging materials, silicon and passive components for wireless and optical communications, power management, sensor, photonics and other analog / mixed signal applications. Since the x-chips are ultra-thin and active side up, standard copper redistribution layer (RDL) technology may be readily used to interconnect the x-chips and destination die, resulting in very short path lengths and, hence, minimum parasitics. ASM AMICRA and X Display Company supply R&D and production MTP manufacturing systems. More than twenty MTP systems are installed worldwide at X-FAB, Micross Components, Tyndall National Institute, Teledyne, the Naval Research Laboratory, the University of Illinois Urbana Champaign, the University of Ghent / imec, UPVfab and undisclosed leading manufacturers.

Electromagnetic and mechanical performance of 3D printed wave-shaped copper solid superstructures

The increasing concern over electromagnetic wave (EMW) contamination has led to the emergence of the EMW-absorbing superstructure element. Cementitious composites typically possess poor electromagnetic wave reflectivity, but this was improved through 3D printing technology, which offers greater productivity and design flexibility. In this study, a new wave-shaped EMW absorbing superstructure was manufactured using 3D cement printing, and mechanical testing showed a significant improvement in flexural and shearing strength. Molecular dynamic simulation was utilized to investigate the mechanism of the enhanced mechanical properties at the molecular scale. The EMW absorption performance of the printed specimens was analyzed from 1 GHz to 18 GHz through the Naval Research Laboratory (NRL) equipment, exhibiting a significant improvement in reflectance, especially in the low-frequency domain. Based on experimental results, the optimized design of the superstructure was proposed, which possesses an average reflection loss of −25 dB, a peak reflectivity of −37.4 dB, and an absorbing bandwidth of 17 GHz. These findings suggest that the 3D-printed EMW absorber element has great potential for use in minimizing electromagnetic contamination in various applications.