bluuebunny/crossref_metadata_2025 huggingface dataset:
Observing Electrochemical Performance Trends with the Physical Scaling of Bipolar Membrane Electrodialysis for the Capture and Concentration of Atmospheric CO2
Authors: Crow Allison M , Shin Grace , Deutsch Todd G , Smith Wilson A
Published: August 2024

Bipolar membrane electrodialysis (BPMED) is a proven technology for separating ionic species driven by electrochemical potential through ion conductive membrane separators. When using a bipolar membrane (BPM) as the separator, a pH gradient is created by the generation of acid and base via water dissociation at the internal interface of an anion conductive and a cation conductive membrane. BPMED can been used for the capture and concentration of atmospheric CO2, for example when using a liquid alkaline capture sorbent, where the acidification of the capture stream can be used to regenerate pure CO2 while further basification of the remaining effluent regenerates the alkaline capture sorbent to be re-used in the direct air capture process. Current commercial BPMs require high overpotentials to drive water dissociation and can only operate at low to moderate current densities. While considerable work has gone into the development of efficient, electrochemically active BPMs through improved membrane polymer chemistries and high-activity water dissociation catalysts, little work has been done to physically scale up these materials and use them in electrodialysis-driven carbon capture and concentration systems beyond lab scale (i.e., >1 cm2).

In this presentation, we will report a scalable BPMED cell that can sense the resistive contributions of the individual membrane components (i.e., the anion exchange and cation exchange membranes, and the water dissociation at the internal BPM interface) with increasing membrane active area from 1 cm2 to 25 cm2. With this BPMED cell, changes in the BPM and water dissociation catalyst compositions and structures are related to electrochemical performance metrics (overpotential and CO2 recovery efficiency) at increasing physical scales. Electrochemical impedance spectroscopy (EIS) was used to reveal resistive contributions to the cell at increasing active area, while the inlet and outlet pH were measured to confirm the overall acidification and basification of the dialysis cell to promote carbon capture and conversion, as well as sorbent regeneration. This study aims to build a bridge between the necessary improvements in the membrane and water dissociation catalyst compositions with industrially relevant energy efficiency and conversion performance, accelerating the development of high performance BPMs.
Next Generation Lab-Scale Bipolar Membrane Electrodialysis Test System
Authors: Vulpin Olivia T. , Boettcher Shannon W.
Published: August 2024

The world of electrochemical devices has witnessed remarkable progress in recent years, with particular emphasis on the development and advancement of bipolar membranes (BPMs). This progress has predominantly centered around BPM applications within membrane electrode assembly (MEA) systems, encompassing technologies such as fuel cells and electrolyzers. The exploration of BPM in these MEA systems has allowed for an almost complete elimination of the BPM overpotential for water dissociation and has dramatically changed the playing field and viability of BPM. This rapid advancement in understanding BPM fundamentals has in part come from the commercially available and universally utilized lab-scale electrolyzer/fuel cell systems. These devices have allowed labs around the world to focus on finite aspects of the BPM without being slowed by the debates of varying test stands.

With the development of advanced, MEA optimized BPM and increased understanding of BPM fundamentals, the time is right to embark on the next phase of BPM research. This next phase looks to expand the use of BPM to non-MEA systems, including CO2 sequestration systems, electrodialysis, brine remediation, organic acid/base production, and more. These non-MEA systems present unique challenges and opportunities that demand innovation. To begin the expansion of advanced BPM to non-MEA applications we present here a lab-scale BPM electrodialysis system that allows for small membrane sizes and full system monitoring. This system is cheap to build, highly modular, easy to operate, and allows for a wide range of non-MEA systems to be explored. With this, we hope to speed up the translation of advanced, MEA optimized BPM to non-MEA applications.
Design of Lithium Metal Anode and Other High-Capacity Alloy Anodes Solid-State Batteries in Context of Contact Loss between Anode and Solid Electrolyte Separator
Authors: Molel Leshinka Leshinka , Fuller Thomas
Published: August 2024

Cyclic volume changes and non-uniform electrodeposition/stripping, among other cycling-induced chemo-mechanical degradation of lithium metal and lithium-alloy solid state batteries, lead to contact loss between the anode and the solid electrolyte separator[1, 2]. In-operando experiments have shown ac-

celerated short-circuiting behavior due to contact loss in “anode-free” solid-state batteries[2]. Simulations reveal the relationship between active area fraction and the ratio of effective conductivities in made-up active area configurations[3]. Through modeling experiments using imputed active con-tact area of lithium-metal anode batteries, we quantify the effects of this contact loss in terms of accelerated chemo-mechanical degradation and de-creased rate capability. Specifically, we (1) quantify the interfacial resistance due to this contact loss, (2) show non-uniform local current density distribution such that local current densities could exceed lithium filament growth critical current densities, (3) show uniaxial stress inhomogeneity due to non-uniform reaction at the anode/separator interface, and (4) show non-uniform reaction distribution at the positive electrode.

Besides allowing for the optimization of designs to minimize contact loss, our work sheds light on tradeoffs in the design of solid electrolyte separators.

References

[1] John A. Lewis, Francisco Javier Quintero Cortes, Yuhgene Liu, John C. Miers, Ankit Verma, Bairav S. Vishnugopi, Jared Tippens, Dhruv Prakash, Thomas S. Marchese, Sang Yun Han, Chanhee Lee, Pralav P. Shetty, Hyun Wook Lee, Pavel Shevchenko, Francesco De Carlo, Christo-pher Saldana, Partha P. Mukherjee, and Matthew T. McDowell. Linking void and interphase evolution to electrochemistry in solid-state batteries using operando X-ray tomography. Nature Materials, 20(4):503–510, 4 2021.

[2] John A. Lewis, Stephanie E. Sandoval, Yuhgene Liu, Douglas Lars Nelson, Sun Geun Yoon, Runzi Wang, Ying Zhao, Mengkun Tian, Pavel Shevchenko, Emilio Martı́nez-Pañeda, and Matthew T. McDowell. Ac-celerated Short Circuiting in Anode-Free Solid-State Batteries Driven by Local Lithium Depletion. Advanced Energy Materials, 2023.

[3] Evans Leshinka Molel and Thomas F. Fuller. Application of Open-Source, Python-Based Tools for the Simulation of Electrochemical Systems. Journal of The Electrochemical Society, 170(10):103501, 10 2023.
A Large-Scale Electrometallurgical Treatment of Waste Printed Circuit Board (WPCB) in Ethylene Glycol for Metal Recovery
Authors: Le Qingguo , Jin Yangxin
Published: August 2024

The accumulating generation of E-Waste is gaining more concern. This work reported an environmental-friendly approach, slurry electrolysis (SE), to highly effectively recover metals embedded in Waste Printed Circuit Board (WPCB). The reusable ethylene glycol (EG) is employed as the electrolyte, simple and cheap graphite rod, and copper strip function as anode and cathode, respectively. And it could operate at room temperature and pressure. EG can withstand for hours or days of electrolysis with no sign of degradation but evaporation. It has shown a good selectivity in the leaching solution with metal ions. The metals with high activity could be electrochemically oxidized but not reduced. The metals with low activity could undergo both. From the current results, the system has demonstrated a moderate faraday efficiency of the cathode of 67.7%, successfully recovered 95-97% copper from the real WPCB powder with 61% copper, 24% Al, 10% Zn, 3% Sn and some trace metals. Notably, the extracted metals are all in powder form and easily extractable, indicating that it requires only some facile treatments to make the powder eligible for replacement from mining. This study proved another novel approach to recovering metals from E-Waste on an industrial scale.
(Invited) Trials and Tribulations on Scaling Metal Recovery Technology from Lab to Market
Authors: Lippert Cameron , Landon James , Rassoolkhani Alan , Boehme Lindsay
Published: August 2024

PowerTech Water, Inc. d/b/a ElectraMet (ElectraMet) is a cleantech company founded in 2014 in Lexington, KY with the goal of applying carbon and electrochemistry to solve fundamental challenges in wastewater and process water applications. There exists a broad array of separation applications that could be tackled through electrochemical routes, and ElectraMet has worked on many of them.

Early in ElectraMet’s history, focus was directed towards salt removal applications such as salt-free water softening, brackish water desalination, and ultra-pure water production. While some traction was found in these spaces, penetration of a new technology versus entrenched incumbents such as reverse osmosis and distillation made the sales process difficult. Limitations in what the technology could and could not do were also determined. Therefore, within the first few years of operation, focus shifted towards particular customer pain points, specifically metals separation applications. Problematic metals concentrations are present in drinking water, industrial effluents, and storm runoff, just to name a few. As a growing but still small business, it is important to choose a beachhead market where you can have the strongest value proposition, and electrochemical separations of metals offered a unique opportunity to solve challenges in the metals separation space. Therefore, considerable work has gone into developing these separation processes for specific metals and specific markets.

In this talk, the early history of the company will be reviewed, including technology, funding, and market applications. The impact of strategic advisors and early successes will be discussed with regards to the direction of the company. Ultimately, product-market-fit and the strategies and struggles in building a small business will be presented. Efforts will be made to highlight possible pitfalls, roadblocks, and opportunities as seen through this particular journey.
(Invited) Achieving Circularity in the Battery Industry through Salt Splitting Electrolysis
Authors: Akuzum Bilen , Hackl Lukas , Pohlman Garrett , Bandaru Siva Rama Satyam
Published: August 2024

In an era focused on sustainability, Aepnus Technology introduces a transformative approach in electrochemical engineering that enables circularity in the manufacturing of battery chemicals. Aepnus’ innovation centers on advanced gas diffusion electrodes (GDEs), engineered to significantly boost efficiency and lower the costs of electrolytic salt splitting processes. GDEs offer a cost-effective alternative to traditional planar electrodes, and open new reaction pathways for versatile product generation. For example, GDE’s can improve on the incumbent technologies capable of converting sodium sulfate waste into useful chemicals such as sodium hydroxide and sulfuric acid. Aepnus’ GDEs are poised to revolutionize the recycling of sodium sulfate, the largest waste product of the lithium battery supply chain.

The application of these GDE’s can extend into the synthesis of various metal hydroxides and other essential commodity chemicals. Aligning with the principles of circular economy and eco-manufacturing, our project addresses challenges in electrolyzer design, catalyst advancement, and reactor optimization. We underscore the translation from academic research to scalable solutions, integrating our technology seamlessly into existing industrial processes.

This presentation will delve into the environmental and operational advantages of Aepnus GDEs, their role in reducing the ecological footprint of chemical manufacturing for the battery industry, and our journey to manufacture chemicals in ways that are circular and carbon neutral. Additionally, we will provide insights into the setbacks of existing electrochemical technologies such as membrane electrolysis and bi-polar electrodialysis (BPED), while demonstrating the real-world applicability of our technology through performance data at lab and pilot-scales.
(Invited) Accelerated Three Electrode Cell (TEC) Testing for Optimizing Electrodes in Conventional Alkaline Electrolysis and Anion Exchange Membrane Water Electrolysis
Authors: Abellán Gonzalo , Lloret Vicent , Seijas Da Silva Alvaro
Published: August 2024

The merging of conventional Alkaline Electrolysis (AEL) and Proton Exchange Membrane Water Electrolysis (PEMWE) has led to the development of Anion Exchange Membrane Water Electrolysis (AEMWE). At this juncture, both AEL and AEMWE technologies offer an advantage over PEMWE as they do not require critical raw components and materials (CRM).[1] While AEMWE has demonstrated higher efficiencies than AEL with thin membranes and low concentrations of KOH, AEL technology addresses the significant stability challenge posed by anionic membranes by employing KOH electrolyte with novel zero-gap configurations, relying on stable diaphragms. Consequently, AEL technology offers a more cost-effective and scalable solution for current large-scale hydrogen production, while AEMWE remains a promising solution that will most probably be implemented on larger scales in the following decade. In any case, both technologies require more efficient and scalable catalysts for lowering the overall cell voltage of electrolyzers. Along this front, Matteco’s patented processes stand at the forefront of manufacturing highly active and stable catalysts and electrodes crafted from Layered Double Hydroxides (LDHs), which have gained increasing attention due to their low overpotentials and promising stabilities.[2] However, Beyond the intrinsic qualities of the catalysts, a myriad of factors —electrolyte concentration, substrate type, and the catalyst/substrate interface— play pivotal roles in determining electrolyzer activity and stability, forming a complex multiparameter matrix that will condition the final performance of the electrolysers. Contrary to three-electrode catalyst testing conditions for PEMWE, in which acids are used to simulate the real conditions of electrolyzers, AEL- and AEMWE-TEC testing can be performed using realistic conditions, from 0.1 to 7M alkaline electrolytes.

Thus, this work presents the results of Matteco’s accelerated TEC testing to decipher the complex multiparameter alkaline electrolysis matrix, obtaining the most promising catalysts, substrates, and processes that deliver the best performances and stabilities of AEL and AEMWE technologies.

References:

[1] N. Du, C. Roy, R. Peach, M. Turnbull, S. Thiele and C. Bock, Chemical Reviews, 122, 11830 (2022).

[2] L. Hager, M. Hegelheimer, J. Stonawski, A. T. S. Freiberg, C. Jaramillo-Hernández, G. Abellán, A. Hutzler, T. Böhm, S. Thiele and J. Kerres, Journal of Materials Chemistry A, 11, 22347 (2023).
A New Integration Scheme to Prevent Chemical Attack on Floating Polysilicon Gate of Non-Volatile Memory
Authors: Yang Yuming , Kong KIM Foong , Teh Young Way , Zhou Guanyu , Yu Nianhong , Yu Kankan
Published: August 2024

Silicon pitting has been observed on floating gate polysilicon layer of embedded non-volatile memory(e-NVM) process due to chemical attack caused by HBr residual interacting with moisture. This paper successfully demonstrates a new integration scheme for a robust floating gate process against silicon attack for embedded stacked/split gate non-volatile memory process. Firstly, CF4 was introduced into floating gate polysilicon etch recipe to replace HBr, which has been CMOS gate polysilicon etch gas in traditional logic process due to the advantage of higher selectivity despite the disadvantage of low vaporability, for better or cleaner process control. Secondly, an additional plasma removal stripping (PRS) clean step was added before chemical removal stripping (CRS) to give better etch by-product cleaning, even though there is no photoresist and lithography involved on the poly blanket etch for the better etch by-product cleaning. This new scheme has been verified using inline optical inspection defect-scan to prove the sufficient process margin for better mass production control that came from improved manufacturing Queue-time margin (longer waiting time) between dry-etch step, CRS step, and subsequent downstream process steps.

Keywords—Flash Memory, NVM, Floating Gate, HBr, Plasma Etching, Q-time, Chemical Attack, Silicon Pitting
Numerical Analysis of Thickness Uniformity Improvement with Different Inlet Plate Numbers during APCVD Process
Authors: Le Phuoc , Chen Jyh-Chen , Hu Chieh , Tu Chun-Chin , Chen Liang-Chin
Published: August 2024

As the nanometer line width in the semiconductor industry further shrinks, the surface flatness requirements for atmospheric pressure chemical vapor deposition epitaxial silicon films have further increased. Through a series of numerical simulations, this study analyzes the use of inlet plates to solve the problem of uneven wafer thickness during atmospheric pressure chemical vapor deposition. The results show that without the inlet plate, the deposition rate is lower at the center of the wafer and higher at the edge of the wafer. Wafer epitaxy thickness uniformity can be improved when inlet plates are used. By adjusting the position of the inlet plates, this unevenness can be further improved. As the number of inlet plates increases from 0 to 3, the wafer thickness non-uniformity decreases from 12.5% to 1.8% respectively. When the number of inlet plates continues to increase, the thickness uniformity of the wafer can be further improved. When the number of inlet plates is 5, the thickness unevenness of the wafer reaches 0.7%.
Effect of Thickness and Sidewall Slope of Photoresist Mask on Etch Profile of Copper Interconnect
Authors: Cho Yoon Jae , Ha Su Myung , Chung Chee Won
Published: August 2024

We performed high density plasma reactive ion etching of copper thin films using organic gas mixture to define fine patterns less than 10 μm for the application of display devices. However, since redeposition in dry etching of copper thin films frequently occurs due to extremely low reactivity, the etch variables which affect the formation of redeposition were investigated. In this study, the photoresist (PR) masks were employed to etch copper thin films. The effects of the thickness of PR and the sidewall slope of PR on etch profile and redeposition were examined.

The thickness of PR mask were in the range of 3 μm ~ 1 μm and the sidewall slopes of the PR mask were in the range of 90° ~ 45°. The etch profile and etch mechanism of dry etching using different masks were evaluated using field emission scanning electron microscopy and X-ray photoelectron spectroscopy. Finally, an etching method to reduce and/or avoid the redeposition in dry etching of copper thin films will be proposed.

Acknowledgement : This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (20019504) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device.
Design of Charge Transfer Donor-Acceptor Co-Crystals with Long Lived Charge Carriers
Authors: Shivanna Mohana , Abou Taka Ali , Schrader Paul E , Ramasesha Krupa , Allendorf Mark , McCaslin Laura M , Stavila Vitalie
Published: August 2024

Organic donor-acceptor co-crystals with long exciton lifetimes have emerged as a promising class of semiconductors for their unique photophysical properties. These are crystalline, single-phase materials composed of two or more different compounds in a stoichiometric ratio, providing a platform for unveiling the structure–property relationships at a molecular level. Importantly, co-crystals that are packed through π stacking interactions have the ability to form charge transfer (CT) excitons within donor-acceptor pairs.1,2,3 We hypothesize that co-crystals with a high degree of CT will have longer exciton lifetimes. Therefore, we design and synthesized of new co-crystals using derivatives of N,N-bis(3-pentyl)-perylene-3,4:9,10-bis(dicarboximide) (PDI, acceptor) with a series of donor molecules, including peri-xanthenoxanthene (PXX), perylene, and triphenylene. High quality single crystals were isolated by slow evaporation at room temperature from suitable solvent mixtures. Their crystal structures were successfully refined by single-crystal X-ray diffraction and the phase purity was validated by powder diffraction. Crystal structures revealed that the driving force for forming these co-crystals is π...π stacking. We measured diffuse reflectance UV/visible spectra of each of these co-crystals and compared with computed spectra to assign the observed electronic transitions. DFT calculations provide additional insights into the nature of the excited state CT interactions which can be derived from ground state electronic structure calculations. Transient absorption measurements were conducted to understand their long exciton lifetime for each of as synthesized co-crystals. We conclude that this study supported our previous hypothesis and such materials are potentially useful in applications ranging from photovoltaics and opto-electronics to photocatalysis.

References

1) A. Abou Taka, J. E. Reynolds Iii, N. C. Cole-Filipiak, M. Shivanna, C. J. Yu, P. L. Feng, et al. Phys.

Chem. Chem. Phys. 2023, 25, 27065.

2) L. Sun, Y. Wang, F. Yang, X. Zhang and W. Hu. Adv. Mater.
2019, 31, 1902328.

3) I. Schlesinger, N. E. Powers-Riggs, J. L. Logsdon, Y. Qi, S. A. Miller, R. Tempelaar, et al.
Chem.

Sci.,
2020, 11, 9532–9541.
Electrochemical Doping Induced Crystallinity in Organic Mixed Ionic/Electronic Conductors
Authors: Flagg Lucas Q
Published: August 2024

Organic mixed ionic-electronic conductors (OMIECs) are an exciting class of new materials with a range of potential applications including biosensors, electrochromics, thermoelectrics, and neuromorphic computing. These applications all require ionic transport from an electrolyte into the organic active layer during operation. Characterization of this electrolyte and ion swollen state is essential to understanding device operation on a fundamental level. However, this swollen state is particularly difficult to study because it requires development of in-situ techniques. Here, we utilize in-situ Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) to study the crystallinity of the swollen state of OMIECS as a function of applied potential and processing conditions. We find doping induced crystallinity across a variety of different polymer backbones. Finally, we use organic electrochemical transistors (OECTs) to correlate the electronic conductivity with these doping induced morphological changes.
(Invited) A General Approach to Induce Ultralong Room Temperature Phosphorescence in Organic Small Molecules
Authors: Ivancevic Marko R , Wisch Jesse A , Burlingame Quinn C , Rand Barry P. , Loo Yueh-Lin
Published: August 2024

Interest in organic small molecules that exhibit second-scale phosphorescence at room temperature has grown immensely in recent years due to their potential applications in sensing, anticounterfeiting, and bioimaging. However, such material systems are rare—requiring second-scale triplet lifetimes, efficient intersystem crossing, and slow rates of nonradiative recombination. This third requirement has been met by isolating phosphors in a rigid matrix, or by aggregating them into densely packed crystals or powders to suppress the molecular vibrations that lead to recombination. While these techniques work well for a small subset of molecules with specific properties, most isolated molecules in a rigid matrix do not phosphoresce, and most macroscopic aggregates experience significant triplet quenching. In this work, we find a middle ground between these extremes by forming microscopic [approximately submicron sized] phosphor aggregates in rigid polymer matrices using a simple drop casting and thermal annealing process. Using this technique, we activate second-scale phosphorescence at room temperature in 20 molecules that do not otherwise phosphoresce using conventional matrix-isolation or crystallization approaches. We find that increased chromophore loading increases aggregate sizes. Excitons are thus able to diffuse further and interact more, and triplet-triplet annihilation dominates. Furthermore, we determine that excimer formation in some aggregates leads to increased rates of triplet generation—complementing the effect of nonradiative recombination suppression and further enhancing phosphorescence. In sum, the simplicity and robustness of this blending approach significantly loosens the design constraints to access second-scale emission with organic phosphors, allowing researchers to choose from a broader catalog of organic materials to match the desired properties for a given application.
(Invited) Order, Disorder, and Energy Loss in Organic Photovoltaics
Authors: Rand Barry P.
Published: August 2024

We will discuss our recent work to better understand the role of charge transfer (CT) states in organic solar cell function. For one, we have been exploring organic semiconductor-based thin films that feature crystalline grains of up to 1 mm in extent, termed microcrystalline films. We have found that CT states incorporating these long-range-ordered films can be highly delocalized, contributing to noticeably lower energy losses. In another system, we are studying donor-acceptor pairs that feature very high optical gaps (>3 eV) but relatively small frontier orbital energy offset (<1 eV). Such interfaces present multiple CT states that reveal new insight about photocurrent generation and nonradiative recombination at donor-acceptor interfaces. Finally, we have developed a framework to discriminate between dynamic and static disorder contributions. Both are shown to contribute, and the relative contribution depends on materials choice and temperature.
(Invited) Sustainable and Non-Toxic Hydrogel-Based Dye-Sensitized Solar Cell: Performance Evaluation Under Indoor Illumination
Authors: Domenici Sara , Speranza Roberto , Bella Federico , Gatti Teresa , Lamberti Andrea
Published: August 2024

Indoor photovoltaics have gathered growing interest amongst researchers, as a mean to exploit the indoor lighting we use in our daily life to power small devices. Dye-sensitized solar cells (DSSCs) represent good candidates for such applications[1]. However, when it comes to indoor applications, there is an increased demand for non-toxic and non-flammable solvents for electrolytes. The implementation of water-based electrolytes is a promising way to address these issues, whilst also ensuring the eco-friendliness and sustainability of these devices[2]. In this work, aqueous gel electrolytes incorporating a iodide/triiodide redox couple were made with a bio-sourced polymer, xanthan gum[3]. DSSCs were assembled using screen-printed TiO2 semiconducting layers treated with TiCl4 and sensitized with an organic dye, D131. As counter electrode, Pt sputtered FTO was used. The performance of the cells was investigated under indoor light intensities between 500 and 1000 lux.

[1]: Jilakian, M., & Ghaddar, T. H. (2022). Eco-Friendly Aqueous Dye-Sensitized Solar Cell with a Copper (I/II) Electrolyte System: Efficient Performance under Ambient Light Conditions. ACS Applied Energy Materials, 5(1), 257-265.

[2]: Bella, F., Gerbaldi, C., Barolo, C., & Grätzel, M. (2015). Aqueous dye-sensitized solar cells. Chemical Society Reviews, 44(11), 3431-3473.

[3]: Galliano, S., Bella, F., Bonomo, M., Viscardi, G., Gerbaldi, C., Boschloo, G., & Barolo, C. (2020). Hydrogel electrolytes based on xanthan gum: green route towards stable dye-sensitized solar cells. Nanomaterials, 10(8), 1585.
(Electronics and Photonics Division Award) Research Advances Wide- and Ultrawide-Bandgap Power Switching Devices
Authors: Anderson Travis J.
Published: August 2024

Wide bandgap semiconductors such as SiC and GaN (WBG) and emerging ultrawide-bandgap materials such as Ga2O3, AlGaN, and Diamond (UWBG) represent the next-generation materials for high performance medium voltage and high voltage power switch technology. Such devices have a wide range of immediate Naval applications, including high-power satellite communications and radar, unmanned underwater and aerial vehicles, ship drive components, and hybrid vehicle inverters. Vertical SiC power device technology has matured rapidly over the past two decades, owing to advances in substrates, a fundamental understanding of epitaxial growth to eliminate performance-limiting defects, as well as device design breakthroughs. This has enabled breakthroughs in highly integrated module design for medium voltage power conversion with switching frequency >100 kHz. In parallel, lateral GaN-based high electron mobility transistor (HEMT) technology has been highly successful for RF power amplifiers and is well positioned to supersede GaAs-based microwave circuits. Recently, GaN-based vertical and lateral power devices have attracted significant interest due to promising device results coupled with progress in native substrate, epitaxial growth, and processing technology developments. This seminar will present an overview of the WBG/UWBG power device efforts at NRL. This research has four primary focus areas – 1) thermal management in III-N power device structures by diamond thin film integration, 2) characterization of substrate materials and homoepitaxial layers used for drift regions of power devices identify appropriate specifications and benchmark performance, 3) process module development, particularly for selective area doping by ion implantation, and 4) pilot production manufacturing of 1.2kV-class PiN diodes including reliability assessments to identify and mitigate performance limiting defects.
Trap Assessment and Mobility Simulation of Amorphous Indium Gallium Zinc Oxide Thin Film Transistors
Authors: Mattsson Måns Johannes , Parker Jared , Wager John F , Graham Matt Werden
Published: August 2024

Ultra-broadband photoconduction (UBPC) is used to measure the sub-gap trap density of amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) across the bandgap, from the valence band mobility edge to within 0.15 eV (~6kBT) of the conduction band mobility edge. Figure (a) is a plot of the total integrated trap density (Ntraps, green) and the sub-gap density of states (dNtraps/dE, blue) as measured by UBPC for traps located just below the conduction band mobility edge (E-EC = 0). Three Gaussian sub-gap states are observed with peak energies of 0.9, 0.7, and 0.4 eV below the conduction band mobility edge. Note that the width of the 0.4 eV peak (180 meV) is much larger than that of the other two deeper peaks (45 meV). All three of these peaks are likely associated with oxygen vacancies, but it is unclear why the 0.4 eV trap is so much broader than all the other deeper oxygen vacancy derived donor trap states.

The black dotted curves included in Figure (b) are experimental EKV mobility (μEKV) versus overvoltage (VG-VON) plots obtained at three different temperatures (0 °, 20 °, and 100 °C). The red dashed curves are simulated mobility curves obtained assuming that only conduction band tail states act as electron traps to degrade the mobility. Since these red simulated curves grossly overestimate the experimental mobility, other traps must be operative in establishing the black experimental mobility curves. In fact, the inclusion of the 0.4 eV trap measured by UBPC in addition to the conduction band tail states in the simulation (blue curves) leads to excellent agreement between experimental and simulated mobility for all three temperatures (0 °, 20 °, and 100 °C). In summary, it is demonstrated how the mobility of a-IGZO can be simulated by including the experimentally observed DoS of a 0.4 eV centered Gaussian trap state.

References:

1. Mattson, G. W., Vogt, K. T., Wager, J. F., & Graham, M. W. (2023). Illuminating trap density trends in amorphous oxide semiconductors with ultrabroadband photoconduction. Advanced Functional Materials, 33(25). https://doi.org/10.1002/adfm.202300742

2. J.F. Wager (2022), “Amorphous semiconductor mobility physics & TFT modeling,” in Amorphous Oxide Semiconductors, Hosono, H., & Kumomi, H., (pp. 105–123), Wiley.

Figure 1
Spatial Nonuniformity of Photoresponse in SiC UV Avalanche Photodiodes Operating in Linear and Geiger Mode
Authors: Habersat Daniel B , Sampath Anand , Schuster Jonathan , Smith Jeremy , Derenge Michael , Garrett Gregory , VanMil Brenda , Wraback Michael , Bellotti Enrico , Zhu Mike , Ghandi Reza , Dolinsky Sergei , Aghayan Mehrnegar
Published: August 2024

Silicon Carbide's intrinsic material properties, along with the availability of low-defect density, 6" substrates, make it an attractive material system for visible-blind ultraviolet (UV) detectors. Avalanche photodiodes (APDs) made from SiC have been shown to operate both as linear mode detectors with high gain (>10⁷) and as single-photon avalanche detectors (SPADs) with competitive photon detection efficiency. However, reported spatial non-uniformities in photoresponse of these devices will reduce sensitivity [1,2].

In this paper, we examine the impact of device geometry, epitaxial variations, and crystal anisotropy on the spatial uniformity of photoresponse in SiC APDs. Photoresponse maps are generated using a fast 285 nm pulsed LED source that is tightly focused to a ~10 µm spot. Response maps are measured for devices with different geometries fabricated on the same chip in both linear-mode and Geiger-mode. Measurements on standard pin diodes will be presented, along with separate absorption, charge, and multiplication (SACM) structures.

Experimental results indicate that all devices exhibit localized regions of high photoresponse at gain > 1000 and that the spreading of the photoresponse is highly directional. Finger diodes with 120 μm x 30 μm mesas exhibit good response uniformity with a variation < 30% across the device. In contrast, diodes with 60 and 90 μm square-shaped mesas exhibit similar uniform response spreading along one edge that is bounded by the size of the mesa, but a >10x drop in relative response over ~30-40 μm in the orthogonal direction which is much shorter than the extent of the mesa. Devices with 100 μm circular mesas exhibit somewhat similar results to the square diodes, but with the presence of multiple hot spots in response.

Experimental results are analyzed through 3D numerical modeling of devices which accounts for the effects of doping and thickness variations across the substrate as well as the anisotropy of impact ionization. Modeling indicates that small variations in the thickness in the drift regions of a diode can yield meaningful variations in avalanche gain across the mesa. The impact of anisotropic impact ionization will be considered using full-band 3D Monte Carlo calculations.

X. Bai, H.-D. Liu, D. C. McIntosh and J. C. Campbell, "High-Detectivity and High-Single-Photon-Detection-Efficiency 4H-SiC Avalanche Photodiodes," IEEE J. Quantum Electron. 45
300-303 (2009). DOI: 10.1109/JQE.2009.2013093.

L. Su et al, "Recent progress of SiC UV single photon counting avalanche photodiodes," J. Semicond.
40 121802 (2019). DOI: 10.1088/1674-4926/40/12/121802.

Figure 1
Electrochemical Weakening Material Strength for Accelerated Thinning of Silicon Carbide Substrates
Authors: Wu Chun-Huang , Li Shu-Cheng , Lin Yu-Tang , Chien Bill Po-Yen , Chiou Yu-Sheng , Huang Wei-Chi , Cheng Chao-Chia , Lee Benjamin T.-H.
Published: August 2024

This paper presents a novel approach to expedite the thinning of silicon carbide (SiC) substrates, a crucial step in enhancing material performance and extending chip longevity by reducing volume resistivity. The traditional methods of SiC substrate thinning, such as diamond wheel grinding and plasma etching, have inherent limitations, including the risk of wafer breakage and high processing costs. In response to these challenges, we propose an innovative technique involving the electrochemical etching attenuation of SiC strength, offering a cost-effective and efficient solution.

In this study, we employed an electrochemical method to initially weaken the SiC substrate from the surface to a defined depth, followed by fine-tuning its thickness using a conventional diamond grinding wheel. Remarkably, our results demonstrate that SiC substrates subjected to electrochemical treatment exhibit well-structured lattices free from residual stresses. This novel approach not only reduces the risk of wafer breakage but also enhances the material's integrity (Figure 1).

To gain deeper insights into the effects of electrochemistry on SiC material strength, advanced characterization techniques, including scanning electron microscopy, were employed. Our findings reveal that the electrochemically treated SiC surface exhibits a sponge-like morphology, with a cross-sectional profile showcasing prominent columnar structures (Figure 2). This sponge-like structure is attributed to the removal of silicon atoms during anodization, affirming the effectiveness of electrochemical methods in rapidly attenuating the material strength of SiC substrates, thereby facilitating their efficient thinning through grinding without compromising substrate integrity.

In summary, this research highlights the potential of electrochemical methodologies for the initial weakening of SiC substrates, leading to accelerated and cost-effective thinning processes. This breakthrough not only expedites SiC substrate thinning but also contributes significantly to the advancement of SiC substrate thinning and grinding techniques, promising substantial benefits for future semiconductor device fabrication.

Figure 1
Piezoelectric Biomedical Material, Poly-L-Lactic Acid (PLLA), in the Treatment of Spinal Epidural Compression: Diagnosis, Monitoring, and Postoperative Support
Authors: Huang Chun-Ju , Kao Fu-Cheng , Lin Zong-Hong
Published: August 2024

This study aims to design an intelligent biomedical piezoelectric material for monitoring the pressure in the spinal epidural space caused by postoperative hematoma compression (spinal epidural hematoma). Hematoma compression in the spinal epidural space is a clinically challenging condition that is difficult to diagnose, and failure to address it within forty-eight hours may lead to severe consequences. Given its urgency, prompt and accurate diagnosis and intervention are crucial. Due to its elusive diagnostic nature, patients often miss the opportune time for treatment. Therefore, this study utilizes poly L-lactic acid (PLLA), an FDA-approved highly biocompatible biomaterial. After undergoing high-pressure polarization, PLLA exhibits excellent piezoelectric properties, making it an ideal material for monitoring intracavitary pressure. Additionally, since postoperative hematoma formation is a primary cause of spinal epidural membrane compression, this study integrates urokinase, a potent thrombolytic protein, with PLLA electrospun fibers, enabling preliminary treatment upon pressure detection.This intelligent organic biomedical material not only enables real-time monitoring of postoperative spinal epidural space pressure but also passively utilizes ultrasound to release urokinase from PLLA fibers for initial treatment when pressure is detected. Furthermore, the application of electrospun PLLA biomedical material makes the material more easily moldable and simplifies the manufacturing process, expanding its potential applications. In summary, this technology combines expertise in organic materials science, electrochemistry, and clinical medicine, offering an innovative approach to addressing the crisis posed by hematoma compression in the spinal epidural space. In future clinical applications, this technology holds the promise of providing earlier and more effective treatment for patients, potentially becoming a significant breakthrough in the fields of medical electronics and biomedical engineering.

Keywords: Piezoelectric Biomaterial, Pressure Monitoring Sensor, Drug Control Release, Postoperative Support, Diagnostic Innovation
(Invited) Aiot-Integrated Digital Imaging Sensor for Molecular-Fingerprint Profiling of Extracellular Vesicles in Liquid Biopsy
Authors: Lin Hsing-Ying , Huang Chen-Han , Hsu Peng-Wei , Yao Hsien-Wen , Lan Wei-Chun , Yen Tao-Yun , Wen Jin-De , Hsiao Bo-Jiun , Chung Yun-Hsien , Chou I-Hsuan , Lin Ting-Yi
Published: August 2024

The advancement of liquid biopsy techniques for non-invasive tumor analysis holds immense potential in continuously tracking tumor status—recurrence, progression, and treatment response—in real-time. To comprehensively assess tumor evolution, cellular diversity, and drug resistance mechanisms, a pivotal step involves scrutinizing proteins and nucleic acids within extracellular vesicles (EVs) present in biofluids. Our focus lies in crafting an advanced digital bead-based sensor system that seamlessly evaluates the molecular profile of EVs in glioblastoma cases. Our innovative approach enriches tumor-relevant genetic data within EVs using antibody-specific magnetic beads, subsequently amplifying it via reverse transcription recombinase polymerase amplification system across forty thousand droplets. These results are scrutinized using a compact imaging device. The core strengths of our methodology include: (a) Streamlined Sample Processing: Our system facilitates ultra-sensitive miRNA detection in EVs within a rapid ninety-minute window, owing to optimized sample preparation and a compact detection mechanism; (b) Enhanced Signal Clarity: Employing a straightforward isothermal assay significantly boosts the fluorescent signal-to-noise ratio within each 70-µm droplet, achieving over 104 turnovers of fluorescent reporters on a chip; (c) Real-Time Data Analysis: Our system seamlessly captures real-time imaging data for the edge computing, utilizing trained YOLOv5 models for classification, and presents genetic results on the smartphone. Its user-friendly design enables utilization by healthcare workers with varying skill levels. This pioneering approach has the potential to offer affordable, rapid, and informative diagnostics particularly beneficial for underserved regions and healthcare systems facing financial constraints. Furthermore, its adaptability for diverse cancers could revolutionize the pace of diagnosis and treatment decision-making through liquid biopsy, potentially establishing its widespread application in global healthcare.
(Invited) Revolutionizing Diagnostic Access: Emerging Advanced Manufacturing Technologies for Wearable Sensors
Authors: Ray Tyler R
Published: August 2024

Persistent disparities exist in access to state-of-the-art healthcare disproportionately affecting underserved and vulnerable populations. Advances in wearable sensors enabled by additive manufacturing (AM) offer new opportunities to address such disparities and enhance equitable access advanced diagnostic technologies. Such technologies provide a pathway to rapidly prototype bespoke, multifunctional wearable sensors thereby circumventing traditional barriers in resource-limited environments, such as the necessity for specialized facilities, technical expertise, and capital-intensive processes. Here, we highlight several emerging areas of innovation that are revolutionizing the efficiency and cost-effectiveness of sensor development. In this context this talk will present our recent efforts concentrated on developing (A) enhanced methodologies for fabricating laser-induced graphene (LIG)-based sensors, (B) 3D-printing technologies for fabricating high-resolution flexible electronics, and (C) new modalities for wearable microfluidic sensing platforms.
(Invited) Reversible Electrical Percolation in a Stretchable and Self-Healable Silver-Gradient Nanocomposite Bilayer
Authors: Lee Minbaek
Published: August 2024

The reversibly stable formation and rupture processes of electrical percolative conducting path in organic and inorganic insulating materials are prerequisites for operating non-volatile resistive memory devices. However, it has been one of challenging tasks for such resistive switching in dynamically cross-linked polymers capable of intrinsic stretchability and self-healing. This is attributed to the uncontrollable interplay between the conducting filler and the self-healing polymer. In this talk, the development of the self-healing, stretchable, and reconfigurable resistive random-access memory will be presented. The device was fabricated via the self-assembly of a silver-gradient nanocomposite bilayer which is capable of easily forming the metal-insulator-metal structure. To realize stable resistive switching in dynamic molecular networks, our device features the following two properties. First, self-reconstruction of nanoscale conducting fillers in dynamic hydrogen bonding for self-healing and reconfiguration. Second, stronger interaction among the conducting fillers than with polymers for the formation of robust percolation paths. Based on these unique features, we successfully demonstrated stable data storage of cardiac signals, damage-reliable memory triggering system using a triboelectric energy-harvesting device, and touch sensing via pressure-induced resistive switching.
Effect of Amino Acids Used As Intercalating Agents on Electro-Magnetic Properties of Montmorillonite Clay Nanostructures
Authors: Kilina Svetlana V. , Thapa Dinesh , Oas Victoria
Published: August 2024

Layered clay minerals, such as montmorillonite (MMT) with a chemical formula (FeMg)0.25Al1.5Si4O10(OH)2.nH2O, belong to non-toxic, natural, low-cost, abundant materials. Usage of unnatural amino acids (AA) with COOH-CH-NH2 moiety as intercalating agents results in formation of clay nanoplatelets of about 1 nm in thickness. Such organically modified MMT nanostructures (nano-MMT) have improved dispersion, mechanical, flame retardancy, thermal, transport, biocompatibility, and biodegradability properties, making them suitable for tissue engineering. Using first-principle calculations based on the density functional theory (DFT), we study structural parameters governing the interaction between AA molecules, such as 5-aminovaleric acid (AA1), 2-aminopimelic acid (AA2), and DL-2-aminocaprylic acid (AA3), and the nano-MMT. We investigate how these interactions are affected by the concentration of Fe(II)/Mg doping in the nano-MMT, protonation/deprotonation of amino acids, and water environment. Our calculations reveal high sensitivity of magnetic response of nano-MMT to the type of AA, its conformation at the nanocaly surface, and interactions with water molecules. Thus, transition in magnetic orders from ferromagnetism to antiferromagnetism or ferrimagnetism can be achieved by changing the alignment of the AA molecule on the surface. The introduced charge to the AA via its protonation increases the AA-nanoclay interaction, while the magnetization is reduced by about 1.5 times, compared to their neutral counterparts. The predicted tunability of magnetic properties may permit magnetic separation, visualization and imaging of cells, and may also have a therapeutic benefit of these materials. Thus, our calculations show that the molecule-MMT interactions can be probed by electro-magnetic techniques, which extends experimental tools for studding these materials for bio-applications.