Device Processing Research Articles

"Lung-on-a-chip" as a tool for studying the pathophysiology of human lungs

Lung-on-a-Chip (LoC) is a microfluidic device that simulates the gas-liquid interface of the human pulmonary alveoli and is intended for pathophysiological, pharmacological and molecular biological studies of the blood-air barrier in vitro. The LoC device includes a system of liquid and gas microchannels separated by a semipermeable elastic membrane containing a polymer base and cellular elements of the alveoli. Depending on the type of LoC (single-channel, two-channel and three-channel), the membrane may contain only alveolocytes, or alveolocytes in combination with other cells: endothelial cells, fibroblasts, alveolar macrophages, tumor cells, etc. Some LoC models also include a hydrogel stroma that simulates pulmonary interstitium. The first two-channel LoC, in which there is a monolayer of alveolar cells on one side of the membrane and a monolayer of endothelial cells on the other, was developed in 2010 by the group of Ingber et al. at the Wyss Institute of Harvard University in order to reproduce the microenvironment and biomechanics of the alveoli in vitro. Modern modifications of LoC include the same elements and differ only in the design of the microfluidic system, the membrane biomaterial, the composition of the cellular and stromal elements and the special tasks being solved. In addition to LoC that reproduce the blood-air barrier, there are modifications for studying specific pathophysiological processes, screening drugs, modeling particular diseases, such as lung cancer, COPD or asthma. In this review, we analyzed the existing varieties of LoC, the biomaterials used, the methods for detecting molecular processes in microfluidic devices and the main areas of research using the "Lung-on-a-chip" technology.

Raman intensity enhancement of Raman active and forbidden modes induced by naturally occurred hot spot at GaAs edge

Abstract Edge structures are ubiquitous in the processing and fabrication of various optoelectronic devices. Novel physical properties and enhanced light-matter interactions are anticipated to occur at crystal edges due to its broken spatial translational symmetry. However, the intensity of first-order Raman scattering at crystal edges has been rarely explored, although the mechanical stress and edge characteristics have been thoroughly studied by the Raman peak shift and the spectral features of the edge-related Raman modes. Here, by taking GaAs crystal with a well-defined edge as an example, we reveal the intensity enhancement of Raman-active modes and the emergence of Raman-forbidden modes under specific polarization Raman configurations at the edge. This is attributed to the presence of hot spot at the edge, due to the redistributed electromagnetic fields and electromagnetic wave propagations of incident laser and Raman signal near the edge, which are confirmed by the finite-difference time-domain simulations. Spatially-resolved Raman intensity of both Raman-active and Raman-forbidden modes near the edge is calculated based on the redistributed electromagnetic fields, which quantitatively reproduce the corresponding experimental result. These findings offer new insights into the intensity enhancement of Raman scattering at crystal edges and presents a new avenue to manipulate the light-matter interactions of crystal by manufacturing various types of edges and to characterize the edge structures in photonic and optoelectronic devices.

PIROLIZ REAKTORINING QOVURG‘ALI SIRTI ORQALI ISSIQLIK UZATISH SAMARADORLIGINI HISOBLASH

In this article, the thermal parameters of the biomass pyrolysis thermal processing device were calculated. Also, the flow of flue gas at a temperature of 500-600 ℃ during the pyrolysis process, its movement on the ribbed surfaces of the pyrolysis reactor, and its effect on the water boiler on the outer wall of the reactor were studied. The bioreactor is made of the "pipe in a pipe" type, pyrolysis of biomass takes place in its inner pipe, and water is heated in the outer pipe due to the heat lost to the environment. At the same time, the internal pipe of the reactor allows obtaining gaseous fuel by thermal processing of biomass, and the heat in the external pipe of the boiler solves the problem of providing consumers with hot water in the heating system. The proposed device thermally processes agricultural biomass waste and provides autonomous consumers with alternative fuels and thermal energy at the same time.

Highly Efficient Lightweight Flexible Cu(In,Ga)Se2 Solar Cells with a Narrow Bandgap Fabricated on Polyimide Substrates: Impact of Ag Alloying, Cs and Na Doping, and Front Shallow Ga Grading on Cell Performance

Herein, lightweight, flexible Cu(In,Ga)Se2 (CIGS) solar cells with a narrow bandgap of ≈1 eV are grown on polyimide substrates. The poor performance of the CIGS solar cells owing to a low growth temperature (≈400 °C) is considerably improved via Ag alloying, Na doping using alkali‐silicate‐glass thin layers (ASTLs) and the CsF postdeposition treatment (CsF‐PDT), and front shallow Ga grading (surface field; SF). Along with improved device process, a notably high conversion efficiency of 21.2%, low VOC deficit of 0.346 V, and high JSC of ≈40 mA cm−2 are achieved. Ag alloying and Na doping using ASTLs predominantly improve the CIGS bulk quality, while the CsF‐PDT and SF reduce carrier recombination at the CIGS/CdS interface and vicinity. Device simulations reveal that the SF increases the electrical field at the CIGS surface under the forward bias voltage close to VOC owing to electron injection from the CdS side, which increases the chemical potential. Thus, the SF effectively repulses holes and improves the interfacial property. Device simulations also reveal that a high CIGS absorber's quality is prerequisite to benefit from the SF. Thus, CIGS solar cells showing improved bulk quality due to optimum alkali doping and Ag alloying considerably benefit from the SF.

Low temperature catalytic growth graphene with V2O5 prepared with the oxidation method and its application in optoelectronic devices

Based on our previous research on the phase transition property of non-metallic vanadium oxide for low-temperature catalytic growth of graphene, we further propose that V thin films can be deposited by sputtering and then V2O5 thin films can be prepared by oxidizing the V thin films at 400 °C in a rapid annealing furnace with oxygen, which has a better crystalline structure and surface than the V2O5 thin films directly deposited by sputtering. The V2O5 prepared by oxidation was used to catalyze the growth of graphene at 300 °C in a PECVD furnace. During the growth process, a 10-fold increase in the H2 flow rate (200 sccm) was used to repair and eliminate the suspension bonds and defects of graphene, and the quality of graphene films was improved. Due to the high resistivity of V2O5 at room temperature, V2O5 can be directly used as the interlayer of the device, and the graphene-V2O5-Si (GVS) structure photodetector is proposed, which avoids the damage and impact of the transfer process and catalytic layer removal process in the conventional graphene device process. Additionally, because of the negative temperature coefficient of resistance (TCR) of vanadium oxide materials, the optical response of the GVS device is further extended to 1550 nm.

LD-Pumped 228 nm Nd:GdVO4/Cr4+:YAG Passively Q-Switched Solid-State Laser

The 228 nm deep ultraviolet laser, leveraging its advantages of short wavelength, high photon energy, and low thermal effect, can significantly enhance the Raman signal in resonance Raman spectroscopy and demonstrates broad application potential in areas such as precision processing of photonic devices. This paper investigates a solid-state linear-cavity passively Q-switched 228 nm deep ultraviolet laser. Firstly, the laser employs an Nd:GdVO4 crystal as the gain medium, combined with Cr4+:YAG crystal passive Q-switching technology to generate 912 nm pulsed fundamental frequency light. Subsequently, a lithium metaborate (LBO) crystal is used to generate 456 nm second-harmonic light, and finally, a barium metaborate (BBO) crystal is utilized to achieve 228 nm fourth-harmonic laser output. In this paper, we investigate the variation in 456 nm and 228 nm laser output power under the cavity length of 63 mm. Ultimately, at a pump power of 41.75 W, the highest average power of 670 mW was achieved for a 456 nm blue laser output with a repetition rate of 12 kHz and a pulse width of 32 ns. Additionally, a maximum average power of 18 mW was obtained for a 228 nm deep ultraviolet laser output, featuring a repetition rate of 12 kHz and a pulse width of 33 ns.

A Formal Model of the Exploitation Process for Railway Signalling Devices

Railway signalling devices are used to ensure the safety of trains running on the railroad network. With the passage of time, the technical state of railway signalling devices deteriorates. During the exploitation of these devices, processes dependent on changes in technical states and changes in exploitation states occur. Achieving the maximum efficiency in the operation of a railway signalling system requires a shift from traditional corrective servicing to preventive service based on ongoing diagnosis of the technical state of the devices involved in train movements. An even greater opportunity is provided by the introduction of mathematical modelling methods into the exploitation testing of railway signalling devices and the prediction of their basic reliability indices well in advance. The proposed method allows the exploitation strategies for the signalling systems to be changed from a service-life-based strategy to a current-technical-state-based strategy while ensuring the required safety level.

Chasing Schottky–Mott: Metal-first non-alloyed contacts to β-Ga2O3 for interface quality and minimal surface modification

Metal-first non-alloyed ohmic and Schottky contacts are fabricated on β-Ga2O3 with a range of metal work functions (ϕM). The resulting ohmic contacts are of high quality with a contact resistance (Rc) as low as 0.069 ± 0.003 Ω mm. Measurements of the barrier heights (ϕB) indicate that metal-first processing, which preserves the as-grown/bare-substrate surface, also partially un-pins the Fermi-level in (010) and (2¯01) oriented Ga2O3. Depth-resolved XPS (x-ray photoelectron spectroscopy) measurements of the oxidation state throughout the contact metal at the contact–Ga2O3 interface indicate that most non-alloyed contact metals are at least partially oxidized by room temperature redox reactions with the underlying Ga2O3, with metals with a lower ϕM also demonstrating the greatest level of oxidation. As oxidation has been previously observed to enhance a metal’s work function, this may imply that to-date observations of indices of surface behavior << 1 on β-Ga2O3, which have been attributed to severe Fermi-level pinning, may need to be corrected to account for this partial oxidation in addition to other surface modifications during device processing demonstrated in this work.

Electroless Synthesis of Cobalt Nanowires in Magnetic Field and their Characterization by Resonant Magnetometry Methods

In this paper, a simple and effective low-temperature electroless chemical method that provides the synthesis of cobalt micro- and nanowires due to the processes of self-organization of magnetic cobalt nanoparticles under the influence of a magnetic field, using the technology of chemical synthesis of magnetic nanoparticles and nanowires is proposed. Cobalt nanoparticles have magnetic dipole moments. An external magnetic field forces them to be oriented parallel to it. Dipole-dipole interactions between magnetic nanoparticles lead to attraction between cobalt nanoparticles leading to their self-organization into nanowires, reducing their total energy. The resulting smaller nanoparticles fill the gaps between the ordered nanoparticles, leading to the formation of smooth cobalt nanowires. The magnetic and structural properties of the synthesized and commercial nanowires polarized by a magnetic field in the epoxy matrix were studied using the resonant radio-frequency magnetometry and electron microscopy methods. These methods are of interest for optimizing the coercive force of cobalt nanowires with a view to their possible use in creating permanent magnets that do not use rare earth elements, as well as in information processing devices and sensors.

Sub-1 GHz RF-based Energy-efficient Sensor Node for Secure Communication in Low-power IoT and Embedded Applications

Background: The Internet of Things (IoT) devices consist of a microcontroller unit for data processing, a low-power wireless radio module for data transmission, and various sensors for data collection. The sensor nodes and processing devices used in the Internet of Things are resource-constrained, with power consumption and security being the two most critical parameters. Objective: This paper addresses the challenges of power consumption and security in IoT scenarios. It presents a low-power and secure heterogeneous multicore sensing architecture designed for low-power IoT and wireless sensor networks. The architecture comprises a sensing and control subsystem, an information processing unit, and a wireless communication module. Methods: The architecture uses a microcontroller unit based on ARM Cortex M4, a low-power sub-1 GHz RF-compliant communication radio, and a few sensors. The proposed architecture has been implemented and tested using the Contiki Operating System. Results: The implemented sensor node architecture demonstrated performance efficiency, lower energy consumption, and higher security. Conclusion: By leveraging efficient power management, data transmission strategies, and cryptographic security, the architecture contributes to developing energy-efficient and secure IoT devices.

Ultra-fine quantitative removal of silicon materials by femtosecond laser

The development of miniaturized electronic devices is highly dependent on precision manufacturing techniques. To achieve device miniaturization, material removal and processing accuracy down to the submicrometer or even nanometer level are required. The precision machining of the mass block, a key component of the silicon micro-gyroscope, is taken as a reference. To achieve the precision positioning function of the micro-gyroscope, the mass at a certain position of the Si-based mass block must be precisely controlled. Therefore, the ultra-fine quantitative removal process of silicon materials is studied. A femtosecond laser processing system is constructed, and the evolution of micro–nanostructure and etching depth on the silicon surface is explored. An ultra-fine quantitative removal process is developed to achieve quantitative removal of different etching depths on the silicon surface. The experimental results show that the minimum removal thickness can be 0.502 µm. The processing index requirement for a silicon surface removal thickness of less than 0.001 mm has been fulfilled. It is critical to resolve the issue of high-quality manufacturing of miniaturized silicon-based devices.

Nonreciprocal spin wave channeling in ferromagnetic/heavy-metal nanostrips

Nonreciprocity, unidirectionality, and channeling are essential concepts for potential magnonic applications. Nonreciprocity and unidirectionality ensure the efficient propagation of spin waves along predetermined paths with preferential directions, disrupting the symmetry of counterpropagating waves. Channeling fosters the development of intricate spin-wave networks, enabling more sophisticated functionalities. Integrating these concepts into practical applications will shape the future of spin-wave-based information processing devices. This article theoretically studies the dynamics of spin waves in a ferromagnetic strip coupled to a heavy-metal strip, where the nonreciprocity, unidirectionality, and channeling effects are analyzed. Both backward volume (BV) and Damon–Eshbach (DE) configurations are considered, where the lateral dimensions of the heavy-metal and ferromagnetic strips can differ. Calculations show notable nonreciprocal channeling of spin waves in both DE and BV modes. In the BV configuration, the dispersion is reciprocal with nontrivial localization of lateral confined modes. It is shown that the waves can be channeled into the zones in contact with the HM, where the Dzyaloshinskii–Moriya interaction is active. In the DE configuration, the waves exhibit nonreciprocal spin-wave dispersion, allowing unidirectional and channeled spin-wave propagation. The main results are compared to micromagnetic simulations, where an excellent agreement between both methods is obtained. These findings are relevant for envisioning advanced magnonic devices, enabling precise control over spin-wave propagation for innovative, low-power, high-speed information processing.

A provably secure identity-based access control scheme for renewable energy Internet of Things

—The Renewable Energy Internet of Things (REIoT) serves as a sustainable solution to climate warming and environmental pollution, which enhances the stability and reliability of renewable energy systems (RES) by status acquisition of sensing devices (SDs) and intelligent processing of edge devices (EDs). However, the communication channel between SDs and EDs is vulnerable to potential attacks, such as impersonation, man-in-the-middle, and physical capture attacks. Moreover, the sensitive identity information of SDs and EDs cannot be openly disclosed during communication within the REIoT environment. To tackle these security issues, an identity-based device access control scheme for the REIoT (IBAC-REIoT) is proposed, which establishes a secure communication channel between SDs and EDs after mutual authentication. Access control is then conducted using pseudo-identity to ensure device anonymity and untraceability. To validate the proposed IBAC-REIoT's security, a comprehensive security analysis has been conducted, incorporating the widely accepted real-or-random (ROR) model-based formal security analysis, informal security analysis, and formal security verification using broadly accepted automated validation AVISPA tools. Finally, through the comparative analysis with other schemes, it is proved that the proposed IBAC-REIoT is superior in security features, computational and communicational cost, particularly in alleviating burden on SDs.

Design Research on Smart Wearable Devices: A Case Study of Apple Watch

Abstract. Smart wearable devices have rapidly evolved to become essential components of modern technology, transforming the way users interact with the digital world. This paper explores the design and development process of smart wearable devices, focusing on the Apple Watch as a case study. Key design principles such as sensor integration, power management, user interface, and connectivity are discussed in detail. Apple Watch, as one of the leading devices in this field, is examined through its hardware architecture, software environment, and communication protocols. Through this research, we delve into the technical challenges faced during its development and the solutions that make the Apple Watch a successful wearable product. Additionally, the paper highlights future trends in wearable device design, particularly in terms of energy efficiency and enhanced human-computer interaction. The findings indicate that the success of wearable devices, such as the Apple Watch, hinges on achieving a fine balance between performance, user comfort, and energy efficiency, while continuously innovating in the areas of sensor technology and machine learning integration. Ultimately, this study contributes to the understanding of how modern wearable devices are designed and how they can be further improved for future applications in health monitoring, entertainment, and productivity enhancement.

Quantum Sensing of Room‐Temperature Ferromagnetism in 2D Van der Waals Fe3GaTe2 Using Divacancy Spins in SiC

AbstractRoom‐temperature (RT) 2D van der Waals (vdW) ferromagnets hold immense promise for next‐generation spintronic devices for information storage and processing. To achieve high‐density energy‐efficient spintronic devices, it is essential to understand the local magnetic properties of RT 2D vdW magnets. In this work, noninvasive in situ stray field detection is realized in vdW‐layered ferromagnet Fe3GaTe2 using divacancy spins quantum sensor in silicon carbide (SiC) at RT. The structural features and magnetic properties of the Fe3GaTe2 are characterized utilizing X‐ray diffraction, scanning tsransmission electron microscopy, Raman spectrum, magnetization, and magneto‐transport measurements. Further detailed analysis of temperature‐ and magnetic field‐dependent optically detected magnetic resonances of the PL6 divacancy near the Fe3GaTe2 reveal that, the Curie temperature (Tc) of Fe3GaTe2 is ∼360 K, and the magnetization increases with external magnetic fields. Additionally, spin relaxometry technology is employed to probe the magnetic fluctuations of Fe3GaTe2, revealing a peak in the spin relaxation rate around the Tc. These experiments give insights into the intriguing local magnetic properties of 2D vdW RT ferromagnet Fe3GaTe2 and pave the way for the application of SiC quantum sensors in noninvasive in situ stray field detection of related 2D vdW magnets.

Source/Drain Epitaxy for Nanosheet-Based CFET Devices

The complementary field-effect transistor (CFET) is an attractive device architecture for beyond 1 nm CMOS technology nodes where n- and p-MOS nanosheet devices are placed on top of each other [1-3]. In the present paper, we discuss the progress in source/drain (SD) epitaxy development for nanosheet and monolithic CFET (mCFET) devices. A schematic cross-section of a mCFET stack is shown in Figure 1, in the case of a Metal-Diffusion-first (MD-first) integration scheme [3]. In this case, the p-MOS device is made first, leading to a bottom SiGe:B (B-SiGe:B) SD epi layer. The n-MOS device with top Si:P (T-Si:P) SD is placed on top of the p-MOS, which requires an isolation layer between the two devices.Figure 2 shows cross-section transmission electron microscopy (X-TEM) examples for the integration of a co-flow SiGe:B layer [4] in nanosheet and CFET structures with 48 nm and 60 nm contacted poly pitch (CPP) respectively. In case of multiple sheets (Figure 2(a)), the SiGe:B growth happens from the different Si sheets and from the Si bulk. Twin defects can be observed due to the merging of neighboring and opposing sheets. For the bottom SD in CFET structures with single nanosheets (Figure 2(b)), the majority of the SiGe:B is grown from the Si bulk which then merges with the growth fronts from the single sheets. For the pre-cleaning of the nano-sheets before epi growth, we rely on a combination of wet and low-temperature in situ PreviumTM clean [5]. A pre-epi bake is omitted to avoid dummy gate crystallization. Figure 2(c) summarizes specific Ti/SiGe:B contact resistivity (rc) levels obtained using the circular transmission line method (CTLM) for stacks based on conventional co-flow and low-temperature (LT) SiGe:B processes [6-8]. Results are plotted as a function of the material resistivity (r). A lowest rc of ~ 2×10-9 Ω.cm2 is demonstrated with LT-Si0.5Ge0.5:B (active B concentration [B]act = 2.5×1021 cm-3), which is ~ 50% lower than values obtained with conventional Si0.4Ge0.6:B, for which lower [B]act are obtained. In the present paper we will further discuss the progress towards using LT-SiGe:B cyclic deposition etch (CDE) processes in nanosheet-based devices to reduce the access resistance.X-TEM examples of the integration of T-Si:P SD in a CFET structure with 60 nm CPP are shown in Figure 3. A conventional high-temperature (HT)-Si:P [9] (Figure 3(a)) is compared with a LT-Si:P variant (Figure 3(b)). The LT-Si:P process used here is a CDE process running at 525ºC, which combines deposition with a higher order Si precursor and a HCl/GeH4 based etching steps to enable the selective epitaxial growth (SEG) of Si:P SD [10-13]. Figure 3(c) plots the specific resistivities obtained for Ti/Si:P contacts as a function of the active P-concentration ([P]act) as determined from micro-Hall measurements [6,7,13]. For the HT-Si:P process, the doping activation after epitaxy is relatively poor (10%-15%) and post epitaxy spike or laser anneals are typically used to increase the active concentration and decrease the contact resistivity. When moving to LT-Si:P processes with temperatures below 500ºC [14], [P]act can be increased up to ~ 1×1021 cm-3 and the contact resistivity reduced to ~ 2×10-9 Ω.cm2. In the present paper we will further discuss the progress of using LT-Si:P CDE processes in nanosheet-based devices and enable a benchmark of recently developed SD selective epitaxial growth options for the consistent fabrication of performant CFET devices. Acknowledgements This project has received funding from the ECSEL Joint Undertaking (JU) under grant agreement No 101007254. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and Netherlands, Germany, France, Czech Republic, Austria, Spain, Belgium, Israel. The imec core CMOS program members, local authorities and the imec pilot line are acknowledged for their support.[1] N. Horiguchi et al, IEDM2023, 29.1.[2] H. Mertens et al., VLSI2023, 1.3.[3] V. Vega et al., accepted for IITC2024.[4] A. Hikavyy et al., ECS Trans., 104 (4), pp.139-146, 2021.[5] H. B. Profijt et al., ICSI, p.143, 2015.[6] C. Porret et al, IEDM2022, 34.1.[7] C. Porret et al., SSDM2023, p. 287.[8] R. Khazaka et al., 2nd ECS Meet. Abstr., G03-1187, 2022.[9] E. Rosseel et al., ECS Trans. 75(8), pp.347-359, 2016.[10] N. Loubet et al., Thin Solid Films 520, pp.3149-3154 (2012).[11] J.M. Hartmann et al., Semicond. Sci. Technol. 28, p.025018 (2013).[12] E. Rosseel et al., ECS Transactions, 64 (6), pp.977-987, 2014.[13] R. Khazaka et al., 2020 ECS Meet. Abstr., MA2020-02, 1734, 2020.[14] E. Rosseel et al., ECS Transactions, 109 (4), pp.93-98, 2022. Figure 1

Formation of Source/Drain Structures Using Nanosecond Laser Annealing for Multichannel GAA Mosfet Devices

As metal-oxide-semiconductor field-effect transistors (MOSFETs) devices approach their dimensional scaling limits, 3D structures such as gate-all-around FETs (GAAFETs) have been introduced to improve the electrical characteristics of transistors by increasing the effective channel width. In modern logic devices with a GAA structure, in-situ doped epitaxial silicon is grown on recessed source/drain (S/D) regions using selective epitaxial growth (SEG) process. However, the SEG process poses a competitive disadvantage in terms of complexity and cost. To simplify the integration process, we propose a method for forming S/D without relying on SEG. In this study, we investigate the formation of S/D using nanosecond laser annealing process in devices with multilayer channels. Three pairs of Si/Si0.7Ge0.3 multilayer films were deposited on Si (100) substrates using ultra-high vacuum chemical vapor deposition (UHVCVD). After deposition, boron and phosphorus dopants were implanted into the structure. Samples were then subjected to nanosecond laser annealing under various conditions using a krypton fluoride (KrF) pulse laser. Finally, we obtained recrystallized and doped films that function as S/D. Transmission electron microscopy (TEM) confirmed the microstructure of recrystallized films as function of increasing laser power density. Additionally, the dopant distribution was analyzed using secondary ion mass spectrometry (SIMS). High resolution X-ray diffraction (HR-XRD) was employed to examine the strain behavior in the films. Results indicate that the nanosecond laser annealing process is a viable method for forming S/D in devices with Si/SiGe multilayer channels. Acknowledgements This work was supported by the Joint Program for Samsung Electronics at Yonsei University and the Technology Innovation Program (20010598) funded by the Ministry of Trade, Industry & Energy (MOTIE).

Reservoir Computing with Graphene-Based Lithium-Ion Operated Electric Double Layer Transistors

In recent years, the rapid development of AI technology has faced serious problems such as increasing power consumption and computational costs, while the demand for AI technology has increased. One of the possible solutions to these problems is physical reservoir computing (PRC), a form of physical implementation of machine learning that is suitable for efficiently processing time series data. It utilizes nonlinear dynamics of physical phenomena in materials or devices for information processing. There is a potential for low power consumption and miniaturization. Therefore, PRC is promising for applications such as edge AI, which requires in-situ learning without transmitting to the cloud, in environments with limited computational resources. In this context, PRC has been studied using various physical phenomena such as optical response and magnetic spin, but its performance needs to be improved. Previously, our team developed ion-gating reservoirs (IGRs) using solid-state ionic materials, such as electric double layer (EDL) and redox-based transistors (PRC devices).[1,2] In particular, a hydrogen-terminated diamond-based IGR operating in an EDL mechanism has achieved high PRC performance by the nonlinear drain (I D) current response, although the performance needs to be further improved for practical use.[1] Since the nonlinear response of IGR originates largely from the I D -V G (gate voltage) characteristic of the transistor, choosing the channel semiconductor with unique electronic transport properties can give IGRs with different characteristics. In this viewpoint, we considered using semiconductors with ambipolar electron transport (n-type and p-type) in the transistor channel to improve the performance. Therefore, in the present study, EDL ambipolar transistors were fabricated using monolayer graphene as the channel semiconductor, which exhibits ambipolar conduction due to its electronic structure (Dirac cone). We investigated the fundamental electrical characteristics of the transistor and the PRC performance. This study used monolayer graphene deposited by chemical vapor deposition as the channel semiconductor with Au/Cr source and drain electrodes. Then, an electric double layer transistor (EDLT) was fabricated by depositing a Li+- conducting solid electrolyte (amorphous Li-Nb-O) and a gate electrode (LiCoO2) by pulsed laser deposition, as shown in Fig.(a). Applying various V G to the gate electrode causes Li+ transport inside the electrolyte. The formation of EDL at the graphene channel/electrolyte interface changes the electron carrier density in graphene. The I D through the channel can thus be controlled. We evaluated the electrical characteristics of this transistor and its performance as a PRC device through a benchmark task. The I D-V G characteristics measured by sweeping the V G from -1.5 V to +1.5 V are shown in Fig. (b). When a negative V G is increased (e.g., V G < -0.2 V), Li+ moves toward the gate electrode, and holes are injected into the channel surface, forming an electric double layer (p-type conduction). On the other hand, increasing a positive V G (e.g., V G>-0.2 V) injects electrons into the channel surface (n-type conduction). Therefore, V-shaped ambipolar transistor characteristics were clearly observed. The performance of this EDLT was evaluated by the 2nd-order nonlinear autoregressive moving average (NARMA2) task, which is a time-series data prediction task requiring nonlinearity and short-term memory and is thus widely used as a typical benchmark task of PRC. The performance is evaluated by the value of the normalized mean square error (NMSE) with the nonlinear transform output of the PRC and the target (i.e., a low NMSE means high performance). The predicted waveform by the EDLT reproduced the characteristics of the target waveform well, indicating that it predicted the time-series data with high accuracy. The NMSE (the test phase) was 0.015, which was notably lowered by 40% compared to the high-performance diamond-EDLT (NMSE: 0.020 in the test phase) [1] The high performance is attributed to the unique I D-V G and transient characteristic of the ambipolar EDLT. This work was supported by JST PRESTO (grant number, JPMJPR23H4).[1] D. Nishioka, et al., Sci. Adv. 8, eade1156(2022) [2] T. Wada et al., Adv. Intell. Syst. 5, 2300123(2023). Figure 1

Implementation of Integrate-and-Fire (IF) Characteristics of 1T-Neuron Induced Solely by Light Stimuli

With the exponential growth of global data processing demands, the concurrent slowdown in processing speed has become apparent. As a remedy, research endeavors in neuromorphic systems, emulating the structural and functional dynamics of the human brain, are actively underway. Neuromorphic systems research is classified into two distinct domains, wherein synapse investigation and neuron exploration are pursued independently. As with our previous studies[1], synaptic studies have witnessed advancements across diverse realms including materials, structures, and properties[2], but neuronal investigations have lagged considerably behind synaptic endeavors. This disparity primarily arises from the formidable challenges associated with replicating the intricate characteristics inherent to human neurons. To date, the majority of scrutinized neuron components have embraced a two-terminal configuration, renowned for its structural simplicity. Nevertheless, it has been beset by technical challenges on repeatability and reliability[3, 4]. The initial research stage on three-terminal neuron devices focused on Si-based transistors, which possess a complex structure since silicon itself cannot perform the neuron function, resulting in significantly increased power consumption, disadvantageous in light of the semiconductor trend toward miniaturization.[5]. In contrast to prior investigations, this study endeavors to employ titanium dioxide (TiO2), an oxide semiconductor, as the channel material, and seeks to realize integrate-and-fire (IF) characteristics utilizing a simple 1-transistor (1T) structure with a dual gate dielectric, one of which induces abrupt changes in conductivity in the transfer curve by supplying charges and capturing them at the interface of channel layer and dielectrics. Utilizing a 1T configuration obviates the need for intricate circuitry, thereby yielding reduced power consumption. Furthermore, the most significant feature of this study is the successful implementation of IF characteristics induced solely through light stimulation without electrical stimuli, unprecedented in previous reports. While conventional neuron components primarily exhibit firing characteristics induced by electrical stimuli, with certain investigations extending to modulation through the addition of light[6], our research uniquely simulates the emergence of IF properties exclusively via optical stimulation, devoid of any voltage input. The feasibility of such photo-induced firing is attributed to the outstanding photoresponsivity of TiO2 material and its capacity to control the lifetime of the device under 365 nm wavelength light stimulation. Hence, our study represents a significant advancement in the research phase devoted to mimicking human neuronal characteristics. It holds promise for emulating a broader spectrum of human brain activities, particularly regarding low-power consumption. As a result, we anticipate an enhanced capacity to replicate sensory perceptions, including visual stimuli. Acknowledgments This work was supported by an Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korean government [24ZB1330] and UST Young Scientist+ Research Program 2023 through the University of Science and Technology [23AB2710]. References Lee, J. and J.W. Lim, Replicating the Bright-Light Therapy of Seasonal Affective Disorder Using Dual-Gate Dielectric Synaptic Transistors: An Exploration of Neuromorphic Computing Approaches. ACS Applied Electronic Materials, 2024. 6(3): p. 1904-1911. Dai, S., et al., Recent Advances in Transistor ‐Based Artificial Synapses. Advanced Functional Materials, 2019. 29(42). Zhang, X., et al., An Artificial Neuron Based on a Threshold Switching Memristor. IEEE Electron Device Letters, 2018. 39(2): p. 308-311. Park, S.O., et al., Experimental demonstration of highly reliable dynamic memristor for artificial neuron and neuromorphic computing. Nat Commun, 2022. 13(1): p. 2888. Han, J.K., et al., A Review of Artificial Spiking Neuron Devices for Neural Processing and Sensing. Advanced Functional Materials, 2022. 32(33). Han, J.K., et al., Bioinspired Photoresponsive Single Transistor Neuron for a Neuromorphic Visual System. Nano Lett, 2020. 20(12): p. 8781-8788. Figure 1

Electrochemical Impedance Spectroscopy of Bi-Based Cathode for Pellet-Type All Solid-State Fluoride Shuttle Battery

All solid-state fluoride shuttle battery (ASS-FSB) is one of the most promising rechargeable batteries due to its high energy density and cost effectiveness. The FSB operates based on conversion reactions with multi-electron transfers and does not require the use of high-cost metals like those used in lithium-ion batteries (LIBs). Therefore, the ASS-FSB is expanding research field for next generation batteries. Electrochemical impedance spectroscopy (EIS) is widely used for the analysis of energy devices such as LIB electrodes, as it can divide complicated electrochemical reactions into elemental processes based on their characteristic time constants without the need to disassemble batteries. We have reported that 3D structured electrodes can be analyzed by optimizing equivalent circuits 1–3. Although EIS is a powerful tool to understand electrochemical elemental processes in energy devices, detailed EIS analysis of ASS-FSB has not been reported. Here, we investigate the EIS analysis of a pellet-type ASS-FSB composed of a Bi-based cathode and a PbSnF4 anode, using it as an example of ASS-FSB.A Bi-based cathode cell for EIS is composed of Bi cathode (Bi/ Ce0.95Sr0.05F2.95/AB = 25/70/5 by weight), Pb0.58Sn0.42F2 anode (Pb0.58Sn0.42F2/AB = 70/5 by weight) and Ce0.95Sr0.05F2.95solid electrolyte. The loading amount of the Bi-based cathode was 10, 20, 30 mg and that of the Pb0.58Sn0.42F2 anode was fixed to be 20 mg. A three-layer pellet cell (φ10 mm) was prepared in Ar atmosphere by applying a pressure stepwise and finally reaching 740 MPa. The cell was held with 4 bolts, followed by keeping the cell under vacuum. Prior to conducting the EIS, the cells were charge with a CC (120 µA)-CV (cut off voltage of 0.9 V, down to 40 µA) mode. The EIS was carried out after 1st charge with a frequency range from 1 MHz to 100 mHz at SoC of 100% and 140 ℃.Figure 1 shows the charge and discharge curves of the pellet-type ASS-FSBs with different cathode amount measured at 140 ℃. The discharge capacity of the ASS-FSBs with 10, 20, 30 mg cathode loading was 323, 359, and 359 mAh/g-Bi, respectively. The discharge capacity was 84%, 93%, and 93% against the theoretical capacity of Bi, confirming that ASS-FSBs, especially those for 20 and 30 mg, were fabricated properly. Figure 2 represents Nyquist plots of pellet-type ASS-FSBs with different cathode amount measured at SoC 100% and 140℃. The Nyquist plots clearly show one semicircle in high-frequency region (see Fig.2 right) and a line with an angle of ~45゜ in middle-frequency region (see Fig.2 right) and a line with an angle of higher than 45゜ in low-frequency region (see Fig.2 left). Although the loading amount of the Bi cathode are different, the diameter of the semicircles is almost same, indicating that the semicircle is derived from a common element among the pellet-type ASS-FSBs. The length of the line with an angle of higher than 45゜ decreased with increase of the loading amount of the Bi cathode. The decrease is due to the increase of limiting capacitance 2. Meanwhile, the line with an angle of ~45゜ is characteristic feature of an ion transport property in depth direction. In addition, the length of the line increased proportionally to the loading amount of the Bi cathode, supporting that the line is derived from the reaction distribution. The results indicate necessity to adopt a transmission line model to analyze the pellet-type ASS-FSB by EIS.In the presentation, equivalent circuit design using a transmission line model and its attribution for the pellet-type ASSFSB with Bi-based cathode will be discussed with EIS data measured with various condition on SoC and temperature. References H. Nara, D. Mukoyama, T. Yokoshima, T. Momma, and T. Osaka, J. Electrochem. Soc., 163, A434–A441 (2016). H. Nara, K. Morita, D. Mukoyama, T. Yokoshima, T. Momma, and T. Osaka, Electrochim. Acta, 241, 323–330 (2017). H. Nara, D. Mukoyama, R. Shimizu, T. Momma, and T. Osaka, J. Power Sources, 409, 139–147 (2019). Acknowledgement This presentation is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1