bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Interface Control Process of Rare-Earth Oxides on Si for Gate Dielectric Application
Authors: Kakushima Kuniyuki
Published: December 2024

High-k gate dielectrics are indispensable to overcome the shot-channel effect in scaled CMOS devices [1]. Besides the enhanced electrostatic control of the gate electrode, high-k/Si interface properties, including interface state density, fixed charges, dipoles, carrier mobility, reliability, and so on, need to meet the requirement levels. Rare earth oxides have been intensively studied for gate dielectric applications as these oxides react with Si to form a silicate layer, whereas, for the HfO2 case, a SiO2-based low-k interface layer is formed. One of the issues for rare earth oxide gate dielectrics is controlling the reaction amount while obtaining a good interface property. In this presentation, the interface reaction of rare-earth oxides and Si is modeled and controlled by the thermal treatment process. Furthermore, the influence of the metal gate electrode on the interface is assessed.

A la-silicate interface layer is formed between the La2O3 film and Si interface. Although the La atom content in the reactively formed silicate layer generally depends on the annealing environment, a silicate/Si interface can be easily formed, which is advantageous for gate dielectric scaling. However, even under the same process, the La atom content in the silicate increases with the thinning of the initial La2O3 thickness, and the interface state density, flat-band voltage, and mobility degrade [2]. The reaction between La2O3 and Si can be modeled by oxygen atom supply from the environment, and the influence of the metal gate can explain the degradation of electrical properties. A La-rich silicate can be formed with nice interface properties by controlling the supplied oxygen atoms by selecting a proper metal gate stack [3]. The crystal grain size in the metal gate also affects the interface state density. A low interface state density can be obtained by adopting a metal gate material with nano-sized grains [4].

In conclusion, an interface control process of La2O3 film on Si is presented by limiting the oxygen atom supply during the interface reaction. La-rich silicate, a high-k film, can be obtained by adopting a proper stacked gate structure. Also, nano-sized grains in the metal electrodes can exhibit a decent interface property.

[1] J. Robertson, et al., Materials Science and Engineering R, 88, 1 (2015).

[2] K. Kakushima, et al., Solid-State Electron., 54, 715 (2010).

[3] T. Kawanago, et al., IEEE Trans. on ED, 59, 269 (2011).

[4] K. Tuokedaerhan, et al., Appl. Phys. Lett., 104, 021601 (2014).
(Invited) How Reliable Is Our Ranking of Coulombic Efficiency for Li Metal Anodes?
Authors: Gallant Betar M.
Published: December 2024

The performance of Li metal anodes is benchmarked by Coulombic efficiency.1 However, despite the singular importance of this parameter in interpreting and understanding advances in electrolyte design, there is no agreed-upon standard protocol for measuring and reporting CE. The lack of such standardization imperils attempts to rank electrolyte performance and even to understand what performance metrics have truly been achieved.

In this talk, I will share our recent efforts dedicated to understanding how cell assembly parameters affect the resulting CE that is measured in coin cells. Specifically, we examine how selection of cell parts, crimping pressure, cell assembly order, and other parameters lead to different conclusions about CE as a function of electrolyte and why. By further examining a rank order analysis of electrolyte performance subject to such common experimental variations, such as those that might be occurring between different laboratories or even different researchers within the same lab, we demonstrate the ease of drawing erroneous conclusions regarding which electrolytes are field-leading. I will discuss the implications for data-driven research approaches like machine learning, while rely crucially on having accurate metrics and ranking of performance, and make recommendations to improve standardization to bolster data quality.

M. Hobold, J. Lopez, R. Guo, et al., Nature Energy 2021, 6, 951-960.
Super Wide Area Exploration of High Conductive Oxide Solid Electrolytes Using Data-Driven Feature Value Map
Authors: Kita Yuki , Yamada Tetsuya , Shishino Kazuyuki , Hayashi Fumitaka , Teshima Katsuya
Published: December 2024

Currently, over 100,000 data on inorganic compounds was reported in the Inorganic Crystal Structure Database (ICSD). Until now, exploration of functional materials has been experimentally carried out using intuition and experience from such huge amount of materials. This approach needs several trials and errors, resulting in consuming times. Moreover, experimental space is small and only local optimization is possible. Thus, drastic improvement of material performance is difficult. To overcome this issue, we propose super wide area exploration of chemical composition using huge experimental space. In detail, we introduce data-driven exploration map that consists of intrinsic material properties, such as crystal structure, composition, and their physicochemical properties. We call the map as "feature value map", afterwards. Since functional performances are strongly dependent of material's properties, this approach should potentially lead to novel discoveries beyond the subjective perception of the researcher.

In this study, we attempted to expand this feature value map to lithium-ion conductive oxide solid electrolytes. Conventional Lithium-Ion Batteries use flammable organic compounds as electrolytes, which can burn in the worst case if the temperature of the battery rises due to a large load on the battery in some way. All-solid-state batteries use a solid electrolyte, which reduces the risk of ignition. Especially oxide solid electrolytes are known as safe and chemically stable. Although safer, oxide solid electrolytes have lower ionic conductivity and plasticity, resulting in lower battery performance. So far, several exploration approach, including elemental doping, has been carried out. But, still difficulty to satisfy 10-1 S/cm at room temperature, which is a target value for actual use. In this presentation, development of ionic conductivity correlated feature value map and super wide space exploration of materials using this map will be reported.

Acknowledgement

This work was partly supported by Priority Project in Aichi Knowledge Hub Aichi, JST Green Technologies of Excellence, the Strategic Innovation Program (SIP) of the Cabinet Office, and joint research with a company.
ML-Assisted Structural Tuning of Pyridinium Anolytes for Low Reduction Potentials with High Radical Persistence
Authors: Varenikov Andrii , Downing Dennis , Shaffer Madison T , Hickey David P , Guarr Thomas F.
Published: December 2024

In the search for useful redox-active materials for redox flow batteries (RFBs), organic compounds offer a massive design space. Attractive anolyte candidates should be easily and inexpensively produced while exhibiting very low reduction potentials, rapid electrode kinetics, high solubility, low viscosity, and very high persistence of the reduced state. However, it is often the case that molecular modifications intended to improve one of these properties will negatively impact one or more of the others, and the ideal anolyte remains elusive. Our group has largely focused on studying substituted pyridinium salts as potential anolytes for nonaqueous RFBs by accessing them via a simple yet extremely versatile synthetic route utilizing readily accessible pyrylium salts as key intermediates. Previous work from our team identified a surprising
positive
correlation between the number and strength of C-H—π interactions in the solid state and solubility, enabling us to achieve high solubility while maintaining low viscosity and fast electrode kinetics. In this talk, we will describe the use of an ML approach to identify substitution patterns that allow optimization of radical persistence while preserving low reduction potentials.
Machine Intelligence-Accelerated Optimization of All-Temperature Aqueous Electrolyte for Stable Zn-Ion Batteries
Authors: Li Yang , Dong Dejian , Chen Tianle , Wang Chunsheng , Chen Po-Yen
Published: December 2024

Rechargeable aqueous batteries are the leading candidate to meet the surging demand for safe and low-cost energy storage systems. To achieve their development, the optimization of aqueous electrolyte for wide electrochemical stability window (ESW) and stable electrolyte/electrode interfaces is crucial. However, the selection of salts and solvents is critical to dictate the ultimate performance of Zn-ion batteries. Conventional approach requires trial-and-error optimization experiments, which is time-consuming and laborious. Herein, we show an integrated workflow that combines robotics and machine learning to accelerate the optimization of all temperature stable aqueous electrolyte with programmable ESW, ionic conductivity, and electrolyte/electrode interface stability. First, an automated pipetting robot is commanded to prepare 557 electrolyte mixtures using 2 salts (ZnCl2 and Zn(OTf)2) and 2 solvents (water and methanol). After equilibration/stabilization at 30 °C, the solubility of the electrolyte mixtures is evaluated to train a support-vector machine classifier. Next, through active learning loops with data augmentation, 60 electrolyte solutions are prepared/evaluated, establishing an artificial neural network prediction model. The achieved model is capable of two main functions: (1) predicting the electrochemical performance of an electrolyte solution based on its formulation, and (2) conducting multi-objective optimization on electrolytes to identify stable electrolytes with high Coulombic efficiency, rate performance, and interfacial stability. The model-suggested electrolyte with wide ESW, high conductivity, and stable electrolyte/electrode interfaces deliver ultrahigh cyclic stability in Zn||Zn symmetric cells, as well as outstanding capacity retention, fast charge/discharge capability, and excellent efficiency in full cells. The fusion of robotics-accelerated experimentation, machine intelligence, and simulation tools facility the discovery of electrolytes that involve time-intensive experiments and multi-dimensional design spaces.
Estimating State of Charge and State of Health of Lithium-Ion Batteries in Japanese Satellite Reimei
Authors: Bolay Linda , Shironita Sayoko , Umeda Minoru , Hosono Eiji , Asakura Daisuke , Sone Yoshitsugu , Latz Arnulf , Horstmann Birger
Published: December 2024

In-orbit satellite REIMEI, developed by the Japan Aerospace Exploration Agency (JAXA), has been relying on off-the-shelf Li-ion batteries since its launch in 2005 [1]. The data from the batteries have been recorded and analyzed ever since. These comprise current and voltage measurements of several thousand cycles [2,3].

The performance and durability of Li-ion batteries is impacted by various degradation mechanisms, one of which is the growth of the solid-electrolyte interphase (SEI). Long-term SEI growth is the greatest contributor to capacity fade in lithium-ion batteries. Physics-based models for long-term SEI growth have been developed [4,5]. To show the inhomogeneous growth of the SEI in 3D, we performed microstructure-resolved simulations [6].

In this contribution, we will address several aspects of the analysis and simulation of the batteries of satellite REIMEI. We simulate long-term degradation under the generic LEO satellite cycling conditions in a P2D framework. The simulations are validated with terrestrial experiments and in-flight data provided by JAXA [1,6].

These studies are the foundation for analyzing the states of the batteries, which cannot be measured directly. To estimate the state of charge and state of health, we make use of filter techniques and the in-flight data of the satellite batteries. Kalman filters are particularly suitable for the noisy data. Since the states change on different timescales, a multi-time-scale algorithm is developed, where two filters are combined to estimate the states simultaneously. With this approach, we aim to reliably predict the lifetime of satellite batteries in orbit [3].

References

[1] M. Uno, et al., J. Power Sources, 196(20) (2011) 8755–8763.

[2] O. Mendoza-Hernandez, et al., Electrochemistry
88
(
4
) (2020) 300-304.

[3] L. Bolay, PhD thesis Ulm University, (2024), https://doi.org/10.18725/OPARU-52298

[4] F. Single, et al., ChemSusChem, 11(12) (2018) 1950–1955.

[5] L. von Kolzenberg, et al., ChemSusChem, 13(15) (2020) 3901–3910.

[6] L. Bolay, et al., J. Power Sources Advances, 14 (2022) 100083.
Early Prediction of the Failure Probabilitydistribution for Energy Storage Technologiesdriven By Domain-Knowledge-Informed Machinelearning
Authors: Alghalayini Maher , Noack Marcus , Harris Stephen J
Published: December 2024

There is a growing focus on sustainable energy sources and storage systems. The

challenge with such emerging systems is their need to be warrantied for around

15 years with just a year of early testing. This requires accurate data extrapolation

and estimation of the failure distribution. Physics-based approaches can be

overwhelmed by the complexity of degradation, and pure data-driven approaches

are inherently unable to extrapolate beyond the testing data. Here, we propose

a framework for a hybrid approach for technology-agnostic customizations of a

Gaussian process for stochastic and domain-knowledge-informed failure distribution

predictions. We equip the Gaussian process with customized non-stationary

kernels, heteroscedastic noise models, and prior-mean functions to allow for accurate

extrapolation with high accuracy. Furthermore, we minimize testing time

with a novel experiment-stopping criterion, which can significantly reduce the

required data. Our framework could revolutionize energy-storage testing, enabling

the rapid development of new technologies.
Deep Learning Models for Forecasting of Long Duration Redox Flow Battery Performance and Degradation
Authors: Saldanha Emily , Howard Amanda , Chen Yunxiang , Fu Yucheng , Bao Jie , Wang Wei , Sprenkle Vincent
Published: December 2024

Redox flow batteries have the potential to meet long duration energy storage requirements of the implementation of intermittent renewable energy technologies such as solar and wind power. However, the current process for validation of new energy storage technologies requires extensive and time-consuming testing to determine the battery performance over long-term cycling and the lifetime of the battery. In this study, we develop machine learning models for forecasting long term battery performance as well as for the diagnosis and prognosis of the degradation modes driving this performance. To train these models, we leverage a semi-analytical model to generate a large set of synthetic data across a diverse range of operating conditions, cell properties, initial conditions, degradation mechanisms, and degradation models. Based on this data, we develop deep learning models for forecasting voltage curves, cycle-level performance metrics including charging capacity, discharging capacity and energy efficiency, and degradation parameters such as membrane conductivity and electrode porosity. We compare Transformer architectures designed for time series data such as Autoformer and PatchTST, with an operator learning method called Deep Operator Networks (DeepONets) which can predict battery voltage based on the operating parameters and state of charge. By providing insights into expected model performance and lifetimes, such models have the capacity to accelerate the technology validation process, reduce the real-time testing requirements, and shorten the timeline for commercial deployment.
Machine-Learning-Based Efficient Parameterspace Exploration for Energy Storage Systems
Authors: Harris Stephen J , Alghalayini Maher , Noack Marcus , Battaglia Vincent , Higa Kenneth , Collins-Wildman Daniel
Published: December 2024

Machine learning Gaussian Process analysis is applied to search an experimental 4D parameter space that includes temperature, C rate, maximum SOC, and cycle number. Predictions are made for any point in parameter space, together with the uncertainty in each prediction
Towards Autonomous Electrochemistry: Data-Driven Computations and Robotic Experiments
Authors: Assary Rajeev S , Liang Yangang , Murugesan Vijay
Published: December 2024

Autonomous electrochemistry has significant potential to accelerate the material discovery for lithium-ion and beyond lithium-based energy storage applications, including redox flow, lithium-metal, metal-sulfur, metal-air, or multivalent batteries. While the material discovery and system optimization are essential, the performance of these energy storage devices often suffers significantly due to undesired chemical reactions or contaminations with non-inert atmosphere (O2, H2O, CO2 etc.). To this end, it is essential to utilize inert atmosphere conditions
and settings for AI-driven autonomous electrochemistry experiments. We describe an electrolyte discovery framework to perform semi-autonomous experiments to identify optimal electrolyte materials that satisfy multiple desired properties such as redox potential, solubility, and viscosity for non-aqueous redox flow energy storage application. Our contributions1-4 shows notable progress towards autonomous electrochemistry in terms of instrumentation and AI approach development, where inter institutional collaborations may be needed.

Agarwal, G.; Doan, H. A.; Robertson, L. A.; Zhang, L.; Assary, R. S., Discovery of energy storage molecular materials using quantum chemistry-guided multiobjective bayesian optimization. Chemistry of Materials
2021,
33 (20), 8133-8144.

Jain, A.; Shkrob, I. A.; Doan, H. A.; Adams, K.; Moore, J. S.; Assary, R. S., Active Learning Guided Computational Discovery of Plant-Based Redoxmers for Organic Nonaqueous Redox Flow Batteries. ACS Applied Materials & Interfaces
2023,
15 (50), 58309-58319.

Jain, A.; Shkrob, I. A.; Doan, H. A.; Robertson, L. A.; Zhang, L.; Assary, R. S., In silico discovery of a new class of anolyte redoxmers for non-aqueous redox flow batteries. Digital Discovery
2023,
2 (4), 1197-1208.

Noh, J.; Doan, H. A.; Job, H.; Robertson, L. A.; Zhang, L.; Assary, R. S.; Mueller, K.; Murugesan, V.; Liang, Y., An integrated high-throughput robotic platform and active learning approach for accelerated discovery of optimal electrolyte formulations. Nature Communications
2024,
15 (1), 2757.
(Invited) Amorphous Indium-Gallium-Tin Oxide Thin-Film Transistor with High Mobility of 40 cm2 V−1 s−1 and Excellent Stability
Authors: Lim Taebin , Sun Jiwon , Lee Solbee , Jang Jin
Published: December 2024

Metal oxide semiconductor (MOS) has been studied extensively for use in the backplane of the display due to its extremely low leakage current, low temperature and large area process. Among them, InGaZnO (IGZO) thin-film transistor (TFT) is the most popular due to its relatively high mobility and good stability. MOS TFT has a challenge to replace Low-Temperature Poly-Si (LTPS) TFT which is high cost TFT process. However, the electron mobility of IGZO is typically ~10 cm2 V−1 s−1, which is very low compared to LTPS, making it unsuitable for use in high resolution backplane of active-matrix organic light-emitting diode (AM-OLED) display. There are limitations to increasing the mobility of a-IGZO. Therefore, research on high mobility MOS such as In2O3 and InGaO (IGO) to replace LTPS is attracting attention recently. Note that Ga effectively suppresses carrier concentration and lowers the Fermi level (EF), resulting in stable on/off characteristics with excellent stability. The tin cation (Sn4+) increases the carrier concentration by having an electron orbital similar to In (In3+) and increase the overlap of the 5s orbitals. Therefore, a-InGaSnO (IGTO) TFT can have high mobility and thus a good candidate for low-cost AM-OLED TFT backplane. In our previous study, we developed back channel etched (BCE) structured dual-gate a-IGTO TFT exhibiting high mobility (39.1 cm2 V−1 s−1). When compared with a-IGZO TFT, a-IGTO TFT exhibits high mobility, excellent stability, and steep subthreshold swing (SS). We confirmed low density of state in band gap of a-IGTO. But BCE structure has an unintended parasitic capacitor between gate and source/drain electrode that can deteriorate operating characteristics. This can be improved by introducing coplanar structure TFT. It is important to secure thermal stability characteristics at high temperatures. Tin has a higher bond dissociation energy with oxygen (548 kJ/mol) than indium (360 kJ/mol). Therefore, the thermal stability can be improved in a-IGTO TFT.

In this work, we present the high-performance, coplanar structured a-IGTO TFTs fabricated on the glass substrate. The a-IGTO TFT exhibits the field-effect mobility (µFE) of 40.0 cm2 V−1 s−1, SS of 0.16 V dec−1, and on/off current ratio of > 107 at low drain voltage (VDS) of 0.1 V. Even with the short channel length of 2 μm, it shows a threshold voltage (VTH) close to 0 V (−0.3 V) and hysteresis-free characteristics. We confirmed good ohmic contact between Mo electrode with a-IGTO. At gate voltage (VGS) of +20 V, the channel resistance and contact resistance of the a-IGTO TFT are found to be 27.47 kΩ/μm and 16.77 kΩ, respectively. Additionally, we confirmed excellent thermal stability of the a-IGTO TFT, demonstrating unaffected electrical characteristics even after air annealing. The coplanar structured a-IGTO TFT can be a promising candidate for low-cost AMOLED backplane.

Figure 1
(Invited) Advancements in High-Performance Metal-Oxide TFTs Via Atomic-Layer Deposition: A Path Towards Next-Gen Display and Memory Technology
Authors: Yoon Seong Hun , Hur Jae Seok , Jeong Jae Kyeong
Published: December 2024

This paper delves into the recent advancements in crafting high-performance metal-oxide thin-film transistors (TFTs) via the atomic-layer deposition (ALD) process. As metal-oxide TFTs emerge as pivotal backplane technology for cutting-edge display products like organic light-emitting diode (OLED) televisions and selectors for 3D-DRAM, relentless efforts are underway to push the boundaries of performance through diverse methodologies. Among these, two prominent avenues, namely, adjusting cation composition ratios and innovating novel structural designs, are spotlighted. Both pathways leverage the myriad advantages offered by the ALD process over conventional sputtering methods. The paper elucidates the state-of-the-art characteristics of ALD-deposited oxide semiconductors, revealing promising prospects for ALD-derived metal oxide TFTs to emerge as prime contenders for the next generation of high-end active-matrix displays and 3D DRAM devices.

This work was supported by Institute of Information & communications Technology Planning & Evaluation (IITP) under the artificial intelligence semiconductor support program to nurture the best talents (IITP-2024-RS-2023-00253914) grant funded by the Korea government.
Improved Electrical Performance of CVD Monolayer-MoS2 TFT Via Wet Transfer of Van Der Waals Source/Drain Electrodes
Authors: Deng Yuheng , Deng Yu Heng , Sun Hao , Wang Qing He , Xu Jingping
Published: December 2024

In this study, we introduce a novel wet transfer method utilizing PMMA as a supporting tool for electrode transfer, with HF employed to facilitate the separation of the electrode from a sacrificial layer. This method is applied to fabricate source/drain electrodes for MoS2 TFTs. The implementation of the transferred Ag source/drain electrodes significantly enhances the carrier mobility of the CVD monolayer-MoS2 TFT by forming a Van der Waals contact between the monolayer MoS2 and the Ag electrode, which ensures minimal contact resistance between them. As a result, compared with its counterpart with Ag source/drain electrodes prepared by thermal evaporation, the field-effect mobility of the proposed MoS2 TFT is increased from 25.3 cm²V⁻¹s⁻¹ to 69.1 cm²V⁻¹s⁻¹, while the contact resistance is reduced from 13.7 kΩ·μm to 1.49 kΩ·μm.
Diketopyrrolepyrrole-Based Copolymers: Achieving Equally Effective Ambipolar Charge Transport in Organic Field-Effect Transistors and High-Voltage Logic Circuits
Authors: An Tae Kyu , Lee Jihoon , Kim Sung Ryong
Published: December 2024

A copolymer named PDPADPP, comprised of diketopyrrolopyrrole (DPP) and a cyano group connected by a vinylene spacer, undergoes synthesis through a palladium-catalyzed Suzuki coupling reaction. Its electrical behavior in organic field-effect transistors (OFETs) is investigated, revealing ambipolar transport characteristics. Initially, as-cast OFETs display low hole and electron mobilities of 0.016 and 0.004 cm2 V−1 s−1, respectively. However, upon thermal annealing at 240 °C, significant enhancement occurs, with balanced ambipolar transport and improved mobilities of 0.065 and 0.116 cm2 V−1 s−1 for holes and electrons, respectively. Furthermore, compact modeling utilizing the industry-standard BSIM is conducted to evaluate its potential in high-voltage logic circuits. The simulation results underscore the PDPADPP-based ambipolar transistor's excellent performance in logic applications, particularly after annealing at 240 °C, showcasing ideal circuit characteristics.
(Invited) Highly Stable Metal-Oxide Thin-Film-Transistors and Circuits for Large-Area Flexible and Stretchable Electronics
Authors: Park Sung Kyu
Published: December 2024

Thin-film transistors (TFTs) have been considered as an essential component in modern sensory and displays due to their unique electrical properties for pixel and circuit applications, as well as their compatibility with low-cost manufacturing and large-area substrates. As the thin-film electronics have rapidly advanced toward much complex functionality along with higher resolutions and refresh rates, especially with the emergence of area-scalable wide form factors such as large-area foldable and stretchable displays, the features and materials of the TFT devices must evolve to meet these demands. Metal-oxide (MO) TFTs have emerged as a promising platform to facilitate the evolution of electronic products in terms of uniformity, conformability, and reduced manufacturing costs, while enabling large-area electronics on flexible and stretchable substrates due to their cost-effective fabrication and high uniformity.However, despite these advances expanding the potential applications of MO TFTs, implementing highly robust flexible/stretchable MO TFTs with good electrical performance remains somewhat challenging. In this presentation, recent technologies 1-
4 for the structural and material approaches to achieve robust and stable high-form factor MO TFTs are introduced. Additionally, the envision and outlook for more versatile strategy to advance the development of commercial-level high-form factor electronics will be fully discussed.

References

Kim, Y.-H and S. K. Park. et al. Flexible metal-oxide devices made by room-temperature photochemical activation of sol-gel films.
Nature

..
2012
,
489,

-W Jo, J. K. Kim, K.-T. Kim, J.-G. Kang, M.-G. Kim, K.-H. Kim, H. Ko, Y.-H. Kim, and S. K. Park, “Highly stable and imperceptible electronics utilizing photo-activated heterogeneous sol-gel metal-oxide dielectrics and semiconductors”,
Advanced Materials

,
2015, 27, 1182

T. Kim, S. Moon, M. Kim, J.-W. Jo, C. Y. Park, S. H. Kang, Y.-H. Kim, and S. K. Park, “Highly scalable and robust mesa-island structure metal-oxide thin-film-transistors and integrated circuits enabled by stress-diffusive manipulation”,
Advanced Materials

,
2020, 32, 2003276.

H. Kang, J. -W. Jo, J. M. Lee, Y.-H. Kim, J.-W. Kim, S. K. Park, “Full integration of highly stretchable inorganic transistors and circuits within molecular-tailored elastic substrates on a large scale”
Nature Communications
, 2024, 15, 2814
(Invited) Development of Transparent Nanostructured Oxide Semiconductors for Electronic and Optoelectronic Devices
Authors: Varghese Oomman K , Waligo David , Schaffer Lilly , Paulose Maggie
Published: December 2024

Wide band gap oxide semiconductor films offer optical transparency in the visible region of the electromagnetic spectrum. They are a technologically relevant class of materials applied in a wide range of commercial electronic and optoelectronic devices. The films of these materials exhibit high mechanical, chemical and thermal stability. Their electrical conductivity can be tuned from conducting to insulating range. Devices such as solar cells utilize their charge transport properties along with high visible light transmittance. Advent of nanostructured films of these materials has broadened their application scope. For example, such films can serve as high surface area supports for zero and two dimensional light absorbers in solar energy conversion devices. Electrochemical anodization has emerged as an effective technique to grow ordered nanostructured films of these materials on a variety of substrates. Anodically synthesized transparent films of highly ordered titania nanotube array is an example. Recently, our group has been successful in fabricating nanotube films of other wide bandgap oxide semiconductors using anodic oxidation. These materials have shown promising electronic and optoelectronic properties. This presentation provides the details of the fabrication of these materials and their performance as electrodes in solar photoelectrochemical devices for fuel generation and chemical sensors for medical diagnosis.
Ferroelectric Properties and Bulk Photovoltaic Effects of 2D Hybrid Halide Perovskites
Authors: Park Jae Yong , Mihalyi-Koch Willa , Triggs Crhistopher T. , Roy Chris R. , Sanders Kyana M. , Wright John C. , Jin Song
Published: December 2024

Two-dimensional (2D) hybrid organic-inorganic halide perovskites have emerged as a new class of tunable 2D semiconductors with the potential to combine excellent optoelectronic properties with symmetry-enabled properties such as ferroelectricity. Although many lead-based ferroelectric 2D halide perovskites have been studied so far, there is strong motivation to develop non-toxic lead-free perovskites. In this work, we report the ferroelectricity of 2D hybrid perovskites enabled by the rational design of noncentrosymmetric hybrid structures, including examples of lead-free tin-based 2D perovskites. Polarization-electric field hysteresis and second harmonic generation measurements confirm they are ferroelectric at room temperature. The frequency-dependent ferroelectric properties of lead- and tin- based pervoskites are studied, providing switching speed of reversible change of ferroelectric domain. Furthermore, in the photodetector devices fabricated with these new 2D perovskites, we observe non-zero short-circuit photocurrents without an external voltage, essentially a bulk photovoltaic effect (BVPE). The short-circuit current is switchable and controllable with poling voltage, which shows potential multiple ferroelectric states. As the first direct experimental observation of the spontaneous ferroelectric polarization of tin-based 2D hybrid perovskites, this work opens up environmentally friendly 2D tin halide perovskites for ferroelectricity and other physical property studies and could enable potential spin-orbitronic and neuromphoric devices in the future.
(Invited) Phase Transition and Phase Engineering in Layered 2D Materials and Their Devices
Authors: Wang Ying
Published: December 2024

Two-dimensional (2D) materials have emerged as a forefront of research in materials science, driven by their exceptional and diverse properties. These materials, often with atomic thickness, exhibit phase transitions with small energy barrier, which can enable the development of energy-efficicient devices. Understanding these phase transitions is not only a fascinating scientific endeavor but also crucial for technological innovation. In this presentation, we will cover phase transitions in 2D materials, encompassing both intralayer and interlayer phenomena. We will dissect the mechanisms by which phase transitions can radically modify the electrical, optical, and mechanical properties of these materials, and discuss the engineering approaches designed to control energy barrier and transition process. Special attention will be given to the devices developed from phase transition phenomena in 2D materials, highlighting their potential applications in the realms of memory storage and sensory technology.
(Invited) Group III-Nitride Nanostructures and Devices: From Classical Optoelectronics to Artificial Photosynthesis
Authors: Sadaf Sharif , Anand Nirmal , Ghosh Dipon , Rahman Md Afjalur , Jenson Christy G
Published: December 2024

Third generation, group III-nitrides (InN, GaN, AlN and their alloys) semiconductor nanostructures have emerged as an important class of materials for a host of critical applications ranging from classical optoelectronics to quantum to artificial photosynthesis (i.e., photo(electro) chemical water splitting and CO2 reduction). Group III-nitrides exhibit unique properties including broad, tunable, direct energy bandgap, large exciton binding energy, giant spontaneous and piezoelectric polarization field, perfect conduction/valence band edge positioning to drive the redox reactions for fuel productions, interesting surface/interface properties, making them the only materials of choice for the afore-mentioned applications. In this talk, I will first present some recent advances of their epitaxy growth/synthesis, electronic, optical, and quantum properties, including the development of high efficiency visible and deep UV LEDs/laser diodes, and the realization of monolithic micro-LEDs.

A highly efficient and robust artificial photosynthesis integrated device and system (APIDS) is the key for achieving carbon-neutral alternative to fossil fuels. III-nitrides can be used as an ideal building block of APIDS because of their recently discovered photocatalytic properties demonstrating great potential in artificial photosynthesis compared to decade long studied photocatalysts. Herein, the most recent advance in the utilization of III-nitrides-based artificial leaves for building a carbon-neutral substance and energy recycling system will be presented, focusing on solar water splitting toward H2 and solar CO2 reduction toward fuels and chemicals. I will also present on III-nitrides nanostructures-based non-classical on-demand quantum light sources (single photon and entangled photons sources) generation and their usage in quantum communication and optical quantum computing protocols. Overall, the talk focuses on the unique potential of group III-nitrides materials for emerging applications.
An Investigation on the Low Voltage Ferroelectric Hf0.5Zr0.5O2 Capacitor Deposited on Phase-Controlled W Electrode
Authors: Yang Kun , Jeong Hyun Woo , Park Ju Yong , Lee Jaewook , Choi Hyojun , Lee Younghwan , Park Min Hyuk
Published: December 2024

Since the unexpected ferroelectric properties were first reported in HfO2 thin films in 2011, this material has emerged as a promising candidate for next-generation ferroelectric memory devices.[1] They are noted for their sub-10 nm thickness and compatibility with the complementary metal-oxide-semiconductor (CMOS) process. The polarization switching of ferroelectric materials is initiated when an external electric field exceeding their coercive field (Ec) is applied. Yet, the Ec value of ferroelectric HfO2 (1.0-2.0 MV/cm) is higher than that of perovskite ferroelectric materials (0.01-0.1 MV/cm), another ferroelectric material.[2] This indicates that there is a significant challenge in reducing the operation voltage for the ferroelectric HfO2 films to a certain value. Consequently, the HfO2-based capacitor that is switchable at low voltages could be applied to high-efficiency electrical devices. From this perspective, this study reports on the ferroelectric properties, especially focusing on low operation voltage (<1.6 V), of Hf0.5Zr0.5O2 (HZO) thin films deposited on phase-controlled tungsten (W) electrodes. Tungsten can be stabilized to W-α or W-β phases through controlled fabrication conditions of the sputtering system.[3] It could be confirmed that a relatively low working pressure (<4 mTorr) may stabilize the W-α phase, and a high working pressure (>8 mTorr) may stabilize the W-β phase, as analyzed by XRD (X-ray diffraction) analysis. The 8 nm HZO thin films were deposited via the ALD (atomic layer deposition) process on the 50 nm W-α and W-β electrodes. Under a low applied voltage (~1.6 V), the HZO thin films on W-α exhibit a high value of 2Pr (double remanent polarization) = 33.58 μC/cm2, while the HZO thin films on W-β show a high endurance cycle of more than 109 electric field cycles. This result can be attributed to the low Ec of the HZO thin film on W-α and W-β electrodes, 0.78 and 0.69 MV/cm, under an applied voltage of 1.6V. The notably low Ec values facilitate operations at low voltages while enhancing endurance by minimizing the electrical stress on the ferroelectric thin film. This study underscores the significance of electrode engineering in augmenting the ferroelectricity and the endurance of the HZO thin film, presenting a viable strategy for designing low-voltage and high-reliability metal-ferroelectric-metal (MFM) devices.

[1] Böscke, T. S., et al., Appl. Phys. Lett. 99.10: 102903. (2011)

[2] Lee, J., et al., Nano Converg. 10.1: 55. (2023)

[3] O’keefe, M. J., et al., J. Electron. Mater., 24, 961-967. (1995)

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(Invited) Bioinspired in-Sensor Computing for Artificial Vision
Authors: Chai Yang
Published: December 2024

The visual scene in the physical world integrates multidimensional information (spatial, temporal, polarization, spectrum, etc) and typically displays unstructured characteristics. Conventional image sensors cannot process this multidimensional vision data, creating a need for vision sensors that can efficiently extract features from substantial multidimensional vision data. Vision sensors are able to transform the unstructured visual scene into featured information without relying on sophisticated algorithms and complex hardware. In this talk, I will describe our team’s efforts towards bioinspired in-sensor computing for artificial vision. I will talk about the framework of the in-sensor computing and demonstrate a few vision sensors for different scenarios, including visual adaptation, motion perception, as well as event-driven vision sensors for spiking neural network.
All Solution-Processed High-Performance MoS2 Thin Film Transistors with the High-k Perovskite Oxide Dielectric
Authors: Joung Su-Yeon , Lee Chul-Ho
Published: December 2024

Solution-processable van der Waals (vdW) materials with atomic layered crystal structures, are increasingly recognized as promising components for emerging electronic device applications. These materials offer exceptional quality and stability, coupled with the advantage of large-scale and low-temperature processability. Among these, van der Waals-assembled thin films made from transition metal dichalcogenides in solution have recently emerged as highly potential candidates for fabricating high-performance thin-film transistors (TFTs). Despite recent progress, fully solution-processed vdW electronics remain elusive, primarily due to the absence of suitable dielectric materials and scalable fabrication methodologies.

In this report, we introduce the all solution-processed MoS2 TFTs, incorporating perovskite oxides as high-k gate dielectrics. The fabrication process involves preparing colloidal inks for each constituent layer through chemical or electrochemical exfoliation methods, followed by sequential assembly processes forming the semiconductor/dielectric heterostructure. All fabrication steps are performed at temperatures below 250 ℃. The resulting MoS2 TFTs, utilizing Dion-Jacobson-phase perovskite as the dielectric layer, demonstrate superior device characteristics. Notably, they exhibit an ON/OFF ratio exceeding 106, including high mobility (>10 cm2 V-1s-1). Additionally, the integration of high-k dielectric materials enables the transistors to operate at low leakage current (~10-11 A) and very low voltages, around approximately 5 V, significantly reducing power consumption. These TFTs are also compatible with flexible substrates, which further demonstrates their robustness and adaptability in a variety of electronic applications. The successful demonstration of low-temperature fabrication techniques for high-performance MoS2 TFTs not only marks a significant advancement in the field of solution-processable electronic devices but also paves the way for cost-effective, scalable electronics that are capable of hetero-integration.
Engineering High-Color Purity Photonic Crystal Strain Sensors via Melt-Shear Process
Authors: Lee Sang Hoon , Kim Young-Seok
Published: December 2024

Non-close-packed colloidal photonic crystals (CPhCs) are a class of optical materials characterized by their ability to reflect specific wavelengths of light, determined by the arrangement of constituent particles. The manipulation of particle spacing enables precise control over the reflected color, offering versatile coloration capabilities via mechanical or electrical means. This property renders CPhCs highly promising for diverse applications across various fields.

In this investigation, our focus lies on developing a method for fabricating uniform photonic crystal films with exceptional color purity through a uniform melt-shear process. Leveraging polystyrene@poly(methylmethacrylate)@poly(ethyl acrylate) (PS@PMMA@PEA) core-intermediate-shell (CIS) particles with polydopamine (PDA), we crafted stretchable films with tailored optical properties. By subjecting the amorphous CIS particles to high shear force, we induced alignment and crystallization during the melt shear process, yielding films with enhanced crystallinity. The superior color purity exhibited by these films stems from the absorption of scattered light by the PDA coating, which effectively suppresses unwanted reflections. To optimize the active reflection layers, we systematically varied parameters including process temperature, shear rate, pressure, thickness, and stacking method of films. This comprehensive optimization strategy culminated in photonic crystal films capable of seamless color transitions from red to blue. Such remarkable color-changing properties hold significant promise for applications in biomimetic strain and stress sensing, where precise and responsive color variations are desirable indicators.
(Invited) Flexible Electronic Devices Based on Low-Dimensional Nanomaterials and Their Integration Technologies
Authors: Ho Johnny C
Published: December 2024

Flexible electronic technology has broken through the inherent limitations of traditional silicon-based optoelectronics, possessing characteristics such as lightweight, transparency, flexibility, portability, and functional reconfigurability, providing innovative leadership for technological changes in the post-Moore era, such as the Internet of Things, artificial intelligence, and healthcare. Among numerous material systems, single crystal or highly crystalline inorganic materials are more easily compatible with semiconductor processes, possessing superior electrical properties, stability, and reliability. Therefore, they have broad application prospects in the field of flexible electronics in the future. In this presentation, I will summarize the recent activities of my team for systematic research on flexible inorganic electronic devices and integration technologies: (1) Innovative design and manufacturing methods for flexible electronic materials, developed new technologies such as arbitrary substrate compatible epitaxy, deformable semiconductor manufacturing, and ultrafast pulse irradiation synthesis, solved the problems of semiconductor flexible substrate epitaxy and room temperature plastic processing, and provided a foundation for the original innovation of flexible electronic devices. (2) The development of flexible device multi-field regulation and fusion technology has clarified the coupling relationship between physical fields, by which, broken through theoretical constraints and performance bottlenecks, achieved optoelectronic fusion integration and multifunctional visual systems, promoting the development of optoelectronic devices towards integration and intelligence.
(Invited) Edge-Computing Multimodal Flexible Sensor System
Authors: Takei Kuniharu
Published: December 2024

Daily continuous condition monitoring is now of great interests using multi-functional flexible sensors for a variety of applications including healthcare, medicine, and internet of things (IoT). Due to significant developments of wearable electronics including flexible/stretchable devices, non-invasive, home-use, personal healthcare monitoring is getting realistic in near future. Using this device platform, it is possible to realize early-stage diagnosis and remote medicine. For this purpose, vital signals from skin are the most convenient way to measure continuously data collections during daily life. Flexible sensor sheets allow it to detect multiple information including physical and chemical parameters such as electrocardiogram, respiration, temperature, perspiration, chemical contents in a body from skin precisely due to conformable covering over skin surface. To realize this platform, multiple developments including flexible sensors, wireless system, and edge system to analyse huge size of datasets are required. In this talk, I introduce a wireless multiple sensor sheet with real-time data analyses on a smartphone as an edge system. The system has a function to display real-time analysed results on a smartphone to notify the users about their conditions.

Although a lot of researches and developments are still required for practical application, these studies may help to open a door for the next step of flexible electronics.
(Invited) Designing Solution-Processed Photonic Light- and Heat-Management Structures for Solution-Processable and Printable Organic Optoelectronic Devices
Authors: Stingelin Natalie
Published: December 2024

An ever-increasing interest in the development and application of innovative optical and optoelectronic devices places greater emphasis for the advancement of new smart and functional materials that are readily processable. Significant progress has already been realized in the fields of organic light-emitting diodes (OLEDs) and photovoltaic cells (OPVs) through development of novel semiconducting materials. Here we discuss developments and advancements in materials design towards photonic structures that aid and improve light management in organic and inorganic/organic hybrid devices, with focus on solar cells. Specifically, we present a novel inorganic/organic hybrid material that is produced in a one-pot synthesis and is solution processable, and can manipulated to exhibit a refractive index of 1.5 to up to 2.05. The material is of very low optical loss and, thus, can be readily integrated into efficient photonic structures. We cover systems targeted for use in light in-coupling structures, anti-reflection coatings, and beyond. Extension to architectures for heat management, important for a broad range of photovoltaic device platforms, including inorganic, inorganic/organic hybrid and organic devices, will also be presented.
(Invited) Toward Precision Manufacturing with Electron Microscopes
Authors: Rummeli Mark
Published: December 2024

A key feature of my research is to develop a transmission electron microscope (TEM) into an atomic-scale laboratory. This innovative approach allows for the fabrication, modification, and characterization of samples, enabling crucial structure-property studies and synthesis studies to be conducted with high spatial and temporal resolution. Central to this presentation will be an exploration of various electron beam-driven chemical reactions and electron beam engineering techniques, through which we can fabricate and manipulate nano-materials at the atomic level. Such approaches are important for the development and refinement of advanced materials and technologies, for example, the efficiency and performance of electronic and photonic devices.