bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Porous Ni-Pt Alloy Using the Molten Salt Treatment
Authors: Fukumoto Michihisa , Takahashi Hiroki , Kutyła Dawid , Wojnicki Marek , Zabinski Piotr
Published: December 2024

Recently, it is desired to highly active electrode materials for alkaline water electrolysis to produce hydrogen in order to achieve sustainable society. As a cathode material, Ni-Pt alloy porous layer was formed by electrodepositing Pt on Ni substrate sample, followed by Al-depositing and Al-dissolving at high temperature. The Pt was electrodeposited using an aqueous solution as an electrolyte, and the Al-depositing and Al-dissolving were conducted using a molten salt as the medium. The amount of hydrogen gas was determined when water electrolysis was performed at constant voltage with a hydrogen detection gas sensor using a tubular proton conductor.
Optimizing Metal Oxide-Carbon Composites Electrodes for Supercapacitors Via Electrothermal Control on Nucleation Energy Barrier
Authors: Kim Kyungmin , Choi Wonjoon
Published: December 2024

Composites made of metal oxides with carbon substrates are promising candidates for advanced electrochemical electrodes. In most electrochemical applications, the morphological design of the active materials and substrates is a key factor to improve the performance. However, achieving the proper structure or chemical states through conventional synthesis methods inevitably involves high-cost and long-time processes. Therefore, various approaches focus on synthesizing these materials more efficiently by reducing the overall processing duration or energy-inefficient processes. Herein, we present a rational strategy to optimize the physicochemical properties of metal oxides-carbon composites for supercapacitor electrodes by controlling the nucleation energy barrier, manipulated by ultrafast electrothermal processes. We altered the nucleation trends of the precursor by varying the number of defects on the carbon substrates and converting them to the intended metal oxides via joule heating, which could induce a rapid yet programmable heating-cooling process. The electrothermal process can be divided into two steps. The first step conducts creating defects in the carbon fibers by applying high temperatures (∼1500 °C) for a few seconds before casting the precursor. The second heating step (∼600 °C) converts the precursor into active materials after drying for 0.5 seconds. After completing the entire process, NiCo₂O₄ spinel nanoparticles on carbon substrates were obtained on the defective carbon fibers, demonstrating the achievement of predesigned defects on Gibbs free energy according to classical nucleation theory. The optimized composite electrode exhibited high capacitance (∼1925 F g–1) and long cycle life (∼115–123% retention after 20,000 cycles) following electrochemical activation. This work would present a rational approach for devising efficient fabrication methods for various electrochemical electrodes.
Site-Selective Atomic Layer Deposition at TiO2 Defects Via Targeted Dehydration
Authors: Jones Jessica Catharine , Martinson Alex B. F.
Published: December 2024

Minority atomic arrangement (i.e. defects) on surfaces exhibit distinct reactivity which allows for selective surface chemistry exclusively at those sites. We present an atomic layer deposition (ALD)-based technique of site-selective ALD (SS-ALD) targeting undesirable defect sites. Defects on the TiO2 and other oxidized surfaces affect the electronic properties, interfaces, and performance of optoelectronic devices utilizing those interfaces. We present first principles calculations to predict the difference in hydration/hydroxylation of pristine TiO2 terraces and minority atomic configurations (i.e. “defects”) including step edges and oxygen vacancies. In situ ellipsometry reveals the nucleation behavior of the SS-ALD at process conditions precisely tuned for selective hydroxylation of surface defects. An island growth model for nucleation and atomic force microscopy (AFM) imaging are consistent with a site-selective growth mechanism that depends on defect density.
Atomic Layer Deposition Silver for Hydroxide Exchange Membrane Fuel Cells
Authors: Seo Beum Geun , Prinz Fritz , Shim Joon Hyung , Han Gwon Deok
Published: December 2024

The transition to e-mobility to achieve zero-emission targets has spurred the market growth of fuel cell electric vehicles (FCEVs) as one of the clean transportation means. Proton exchange membrane fuel cell (PEMFC) have been widely used as an electric propulsion system for hydrogen-fueled FCEVs. However, the electrochemical reaction of PEMFC, which produces electricity from hydrogen fuel in an acidic environment where the use of platinum group metals (PGM) is essential, is a major obstacle to improving cost and performance competitiveness. Hydroxide Exchange Membrane Fuel Cell (HEMFC) is emerging as a promising technology due to its property of being able to operate in an alkaline environment where non-PGM can be used. The practical use of HEMFC has potential significance in that it can contribute to reducing fuel cell stack cost by excluding the use of PGM and improving electrochemical performance by avoiding harsh acidic operating conditions.

In this study, it was demonstrated that high electrochemical performance can be achieved by applying the silver (Ag) catalyst synthesized by atomic layer deposition (ALD) to the HEMFC electrode [1]. We successfully deposited Ag catalyst in the form of nanoparticulate on porous carbon nanotube-based electrode layers using plasma-enhanced ALD. HEMFC comprising an ALD Ag-coated cathode achieved a high-power density of 2,154 mW/mgAg. It was verified through EIS analysis that cathodic polarization loss, which accounts for a large part of energy loss, is greatly improved in the HEMFC cathode using the optimal ALD Ag condition. This study is meaningful in that it confirmed the potential application of ALD in the design and manufacture of high-performance electrocatalysts for HEMFC in the future.

[1] Park, J.S., Seo, B.G., Koo, J., Lim, J.H., Lee, Y.S., Han, G.D., Prinz, F.B. and Shim, J.H., 2023. High-Performance Hydroxide Exchange Membrane Fuel Cell Comprising an Atomic Layer-Deposited Silver Cathode. Nano Letters, 23(17), 2023.
(Invited) A Solvent-Free, Thermally Curable Low-Temperature Organic Planarization Layer for Thin Film Encapsulation
Authors: Im Sung Gap
Published: December 2024

Thin film encapsulation (TFE) is an essential component to ensure reliable operation of environmentally susceptible organic light-emitting diode (OLED)-based display. In order to integrate defect-free TFE on display with complex surface structures, additional planarization layer is imperative to planarize the surface topography. The thickness of conventional planarization layer is as high as tens of µm, but the thickness must be reduced substantially to minimize the light leakage in smaller devices such as micro light- emitting diodes (LEDs). In this study, a thin – less than 2 µm – planarization was achieved via solvent-free process, initiated chemical vapor deposition (iCVD). By adapting copolymer from two soft, but curable monomers, glycidyl acrylate (GA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), excellent planarization performance was achieved on various nano-grating patterns. With only 1.5 µm-thick iCVD planarization layer, a 600 nm-deep trench polyurethane acrylate (PUA) pattern was flattened completely. The TFE fabricated on planarized pattern exhibit excellent barrier property as fabricated on flat glass substrate, which strongly suggests that iCVD planarization layer can serve as a promising planarization layer to fabricate TFE on various types of complicated device surfaces.
Design of PNP SiGe HBTs Towards 200 GHz fmax
Authors: Raghunathan Uppili , Shank Steven , McTaggart Sarah , Lydon-Nuhfer Megan , Luce Cameron , Hazbun Ramsey , Bosley Stephen , Vallett Aaron , Dillon Daisy , Sirohi Saurabh , Johnson Jeffrey B. , Derrickson Alexander , Jain Vibhor , Pekarik John Jack
Published: December 2024

In the three decades of production, SiGe HBTs have numerous applications including RF and high-speed mixed-signal and analog. While successive generations of BiCMOS technologies in the past have employed process and layout scaling, the advanced high performance platforms (with several 100 GHz fmax) have mostly been restricted to SiGe NPN optimization, and the Si PNP is often only offered as a dependent device with significantly slower speed. There truly exists a gap in literature with the PNP device variants showcasing good fT and fmax above 150 GHz in a BiCMOS platform. It is worth noting that much of the serviceable applications above can be designed with NPN-only topologies. However, having the complementary PNP enables several advantages, including power savings, improved gain, reduced design complexity, and improved reliability.

There are several challenges for making high performance PNP devices including reduced minority mobility in the intrinsic base from the conducting holes, elevated base current from minority electron injection into the emitter, and heterojunction barrier effect directly on the carrier pathway in the collector-base junction. The figure below shows the measured fT/fmax characteristics for a SiGe PNP with Ae = 0.12x2.5 um2 built using a 130nm technology framework optimized for a PNP-only process. The present work expands on the measured results (AC + DC) and the challenges faced in optimizing PNP performance for 200 GHz fmax and beyond.

Figure 1
200 mm Wafer Level Characterization at 2 K of Si/SiGe Field-Effect Transistors
Authors: Komericki Nikola David , Muster Pascal , Reichmann Felix , Huckemann Till , Kaufmann Daniel , Yamamoto Yuji , Lisker Marco , Langheinrich Wolfram , Schreiber Lars R , Bluhm Hendrik , Quay Ruediger
Published: December 2024

The development of a fault tolerant quantum computer necessitates an expansion to millions of physical qubits while maintaining high coherence and minimal error rates. Gated Si/SiGe spin qubits are one of the main contenders to achieve this goal, thanks to the compatibility with existing industrial CMOS processes, which heralds vast capacities and elevated quality benchmarks. Elegant architectural approaches towards scalability of qubits include the electron shuttling over long distances, which promise a reduction of peripherals and opens up space for control electronics.

The concept of Si/SiGe spin qubits and shuttling structures is based on the z-direction confinement of 2D electron gas in a Si quantum well, which is additionally tailored in the x-y-plane by potentials that arise from multiple gate layers. To trace the viability of these complex devices, it is advisable to first check basic functionality of the gate layers with teststructures, like field effect transistors (FETs). It is particularly relevant to characterize at temperatures comparable to the target operating temperature of Gated Si/SiGe spin qubits.

Recently, Fraunhofer IAF has installed a 300 mm wafer prober that can perform device characterization at temperatures as low as 2K. In the related research project, the wafer prober is implemented in a fully industry compatible feedbackloop within heterostructure growth at IHP and device fabrication at Infineon. We present in this paper the viability of this approach by comparing and discussing the current-voltage characteristics and the resulting threshold voltage measured at room temperature and at 2K of 213 FETs on a 200mm wafer. We show the significance of characterizing devices at cryogenic temperatures rather than at room temperature. At 2K, observations were made regarding the presence or absence of off-current, resulting in the clustering of I-V curves and variations in threshold voltage. The origin of these phenomena is scrutinized, examining whether they stem from the cryogenic wafer prober system or are inherent to the FET design. Possible causes are discussed and explored.

Funded by the German Federal Ministry of Education and Research (BMBF) within the QUASAR ”Semiconductor quantum processor with shuttling-based scalable architecture” project.
(Invited) Hexagonal Silicon Germanium As a Direct Bandgap Light Source
Authors: Peeters Wouter H.J. , van Lange Victor T. , van Tilburg Marvin A.J. , Belabbes Abderrezak , Jansen Marvin , Farina Riccardo , van Hemert Max C. , Vettori Marco , Verheijen Marcel A. , Botti Silvana , Bechstedt Friedhelm , Haverkort Jos E.M. , Bakkers Erik P.A.M.
Published: December 2024

All SiGe alloys in the cubic crystal phase have an indirect bandgap. Therefore, SiGe alloys are typically considered as unusable as a light source. However, if the Si1-xGex atoms are arranged in a hexagonal crystal structure, the bandgap becomes direct for x>65%. The emission occurs with a nanosecond lifetime, and is tuneable from 1.8 to 3.4um by varying the SiGe composition. The hex-SiGe alloys have a relatively large separation between the direct and indirect conduction band minima, which makes it stand out as a Group IV light source [1]. The hex-SiGe alloys are realized as shells in a core-shell nanowire geometry, using wurtzite GaAs cores as epitaxial templates to copy the hexagonal stacking to the SiGe shells.

Recently, photoluminescence studies of these core-shell nanowires resulted in the observation of amplified spontaneous emission (ASE) from hex-Si0.2Ge0.8, highlighting a positive material gain in this material system. The positive material gain is enabled by the direct bandgap of hex- Si0.2Ge0.8.

Moreover, we have grown nanowires with multiple shells of different Si1-xGex compositions. Thus, these shells contain heterostructures of hex-Si1-xGex, having a type-I band alignment, allowing us to create hex-Ge/Si0.2Ge0.8 quantum wells with light emission up to room temperature.

The observation of ASE, in combination with the ability to create type I QWs from hex-Si1-xGex, pave the way towards a laser based on hex-Si1-xGex alloys.

[1] Fadaly, E. M. T., Dijkstra, A., Suckert, J. R. et al (2020). Direct-bandgap emission from hexagonal Ge and SiGe alloys. Nature, 580(7802), 205-209.
(Invited) Heterogeneous Integration of IR Detectors with CMOS and Thin Film Transistors
Authors: Lo Yuhwa , Jiang Yunrui , Arya Shaurya , Peng Hexuan
Published: December 2024

Colloidal quantum dots (CQDs) show promising performance in IR detection because of their many unique advantages, including high material quality, flexibility in operation wavelength, easy fabrication process and suitability for heterogeneous integration with CMOS. Our presentation will cover three areas about colloidal quantum dot detectors: (a) the physical model of CQDs, (b) integration of CQDs with electronics, and (c) strategies of overcoming the limit of dark current for uncooled IR detection.

For (a), we will present a physical model considering the unique transport properties of ligand connected quantum dot detectors. The model shows how the CQD detectors perform differently than conventional p-i-n detectors and why those popular parameters derived from Shockley’s diode model such as reverse saturation current and ideality factor cannot model the CQD detectors. For (b), we will show how CQD detectors can be integrated with IGZO thin film transistors on glass substrate, GaN LEDs for wavelength converters, and Si CMOS in a back-end-of-line process. For (c), we will discuss designs of colloidal quantum dot detectors for longer IR wavelengths with minimal effects of dark current to support uncooled operation.
(Invited) Theory-Informed AI/ML for Battery Characterization
Authors: Chan Maria
Published: December 2024

The use of advanced, including in situ and operando, microscopy and spectroscopy techniques has enabled detailed characterization of battery materials during synthesis and cycling. Data-driven approaches, especially guided by computational spectroscopy, enable robust and accelerated information extraction from such microscopy and spectroscopy data. In this talk, we discuss the featurization of x-ray absorption near edge structure (XANES) for extraction of local structure and electronic properties in NMC battery cathode materials [1], and the extension thereof towards the detection of antisite defect and oxygen vacancy from multimodal EELS/XANES. We also discuss the use of data-driven approaches to accelerate the acquisition [2] and analysis [3] of XANES mapping data. Finally, we discuss the use of AI to extract relevant labeled microscopy and spectroscopy data from scientific literature [4], and recent extensions involving the use of large language models and multi-model contrastive learning.

[1] Y. Chen, C. Chen, I. Hwang, M. J. Davis, W. Yang, C.J. Sun, G. Lee, D. McReynolds, D. Allan, J. M. Arias, S. P. Ong, and M. K. Y. Chan, “Robust Machine Learning Inference from X-ray Absorption Near Edge Spectra through Featurization,” Chemistry of Materials, 36, 5, 2304–2313 (2024).

[2] S. Tetef, A. Pattammattel, Y. S. Chu, M. K. Y. Chan#, G. T. Seidler, “Accelerating nano-XANES imaging via feature selection,” Digital Discovery 3(1), 201-209 (2024).

[3] S. Tetef, A. Pattammattel, Y. S. Chu, M. K. Y. Chan#, G. T. Seidler, “Manifold Projection Image Segmentation for Nano-XANES Imaging,” APL Machine Learning 1, 046119 (2023).

[4] E. Schwenker, W. Jiang, T. Spreadbury, N. Ferrier, O. Cossairt, M. K. Y. Chan, “EXSCLAIM! -- Harnessing materials science literature for labeled microscopy datasets,” Patterns 4, 100843 (2023).Corresponding author information
Leverage Battery Research with Atomistic Modeling and Machine Learning
Authors: Onofrio Nicolas , Hellström Matti , Spiering Paul
Published: December 2024

In the quest for sustainable, high-performance energy storage, the development of advanced batteries is crucial. Addressing the complexities of battery materials and processes requires novel, data-driven research approaches. The Amsterdam Modeling Suite (AMS) offers a robust framework for simulating battery materials at multiple levels of theory, integrating atomistic engines (DFT, DFTB, ReaxFF, ML potentials) with a central driver for exploring the potential energy surfaces (PES) via molecular dynamics and Grand Canonical Monte Carlo simulations. The combination of the AMS driver with its dedicated Python interface enables the automatic screening of materials to optimize critical battery properties such as intercalation potentials, diffusion constants, activation energies, redox potentials, mechanical properties, etc.

A key innovation of AMS2024 is its platform for machine learning interatomic potentials, enhancing simulation accuracy while conserving low computational resources. With ParAMS, you can train a single or a committee of machine learning potentials, from scratch, fine-tune universal models, or actively learn the PES based on target molecular dynamics simulation. This facilitates rapid prediction of material properties and reaction mechanisms, accelerating the design and testing of new battery technologies.

Our data-driven approach empowers the battery R&D community to overcome traditional development barriers, enabling precise material performance predictions and the discovery of new materials and mechanisms towards realizing high-energy, stable, and safe energy storage systems.
(Digital Presentation) 2D Transition Metal Borides: Different Etchants for Al Removal from MAB and Application in Cd2+, Pb2+, Cu2+ and Hg2+ Sensing
Authors: Wei Shudan , Kale Girish M , Lai Xiaojun
Published: December 2024

Despite significant progress in MBene research, achieving perfect layered structures and high purity under different etching conditions remains challenging. Additionally, their potential for heavy metal ion detection in electrochemical applications is underexplored. The synthesis of MBenes, particularly MoB, involves removing Al precursor MoAlB. Recent advancements focus on high-temperature solid-state etching using Lewis bases or chemical wet etching, with wet etching proving more economical, milder, and higher purity products. This study compares various non-fluoride etchants' effects. Ammonium persulfate (APS) achieved a significant etching rate of ~71% for Al, resulting in restacked accordion-like multilayered MBene. However, high temperatures led to stable, insoluble AlxO, reducing product purity. CuCl₂ etching yielded a lower rate of ~54%, producing flake structures with copper impurities. Acid etching resulted in a perfect layered structure but lower purity, while alkali etching provided similar etching rates to APS with the highest purity. Complete Al removal at elevated temperatures caused the loss of the layered structure. Maintaining a small amount of Al during hydrothermal etching supports the layered structure, and subsequent room-temperature etching produces fluffy open-layered MBene MoB (OL-MBene).

Electrochemical studies revealed that OL-MBene-modified GCE exhibited excellent performance in detecting Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ ions individually and simultaneously, with high sensitivity and selectivity. Notably, the sensor exhibited superior performance for Cu²⁺ and Pb²⁺ ions. The varying adsorption energies of these ions explain the differences in sensitivity and selectivity, and Pb²⁺ demonstrated the highest sensitivity due to its lowest adsorption energy on the MBene surface. Competitive adsorption studies indicated that Pb²⁺ competes with Hg²⁺ for adsorption sites while having minimal impact on Cd²⁺ and Cu²⁺ adsorption. This research advances our understanding of MBene synthesis and characterization, introducing a new avenue for leveraging MBenes in sensitive and selective electrochemical sensors for environmental monitoring.

Figure 1
Effects of Ge and B Concentration in Selective Epitaxial Growth of Si1-XGex(:B) at Low-Temperature
Authors: Shin Hyerin , Yoon Dongmin , Ko Dae-Hong
Published: December 2024

As two-dimensional devices approach their scaling limits, monolithic complementary field-effect transistors have emerged to meet the demands of advanced transistors. A low thermal budget process is essential to prevent damage to the underlying layers while forming upper layers. Therefore, a low-temperature approach for the selective epitaxial growth (SEG) of SiGe(:B) in source-drain formation is necessary. The cyclic deposition and etch method was employed for its high selectivity, highlighting the need for further research into the incubation characteristics of B-doped SiGe. [1] We investigated the incubation behavior of SiGe(:B) on SiO2 under varying Ge and B concentrations in an ultra-high vacuum-chemical vapor deposition (UHV-CVD) chamber.

In this study, we investigated the influence of the Ge and B concentrations on the incubation time for SiGe(:B) on SiO2, comparing it with the epitaxial growth on Si(100) and Si(111). First, we analyzed the incubation properties of undoped Si1-xGex (0 < x < 0.4) layers. We then explored the effect of B concentration by varying the B flow rate. Our findings indicate the higher Ge concentrations extend the incubation time, independent of the total gas flow rate. In contrast, B doping reduces the incubation time compared to with that of undoped SiGe, and increasing B concentration further shortens the incubation time. Atomic force microscopy and scanning electron microscopy were used to examine amorphous formation on SiO2. In addition, high-resolution X-ray diffractometry and ellipsometry were used to analyze Ge and B concentrations, as well as growth thickness. Our study offers comprehensive insights into the low- temperature SEG process window for SiGe(:B).

Acknowledgment

This work was supported by the Technology Innovation Programs (RS-2023-00235609) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).

References

[1] Hartmann, et al. , -ECS Journal of Solid State Science and Technology 3.11 (2014): P382.
Battery Life Prediction Under Few-Shot Conditions
Authors: Wan Jiayu
Published: December 2024

Accurate prediction of battery lifetime is critical for ensuring timely maintenance and safe operations of batteries. While data-driven methods have made significant progress in battery life prediction, the lack of labeled data often leads to low model accuracy, hindering the development of these techniques. To address this challenge, we develop a semi-supervised learning technique named partial Bayesian co-training (PBCT) to enhance the modeling of battery lifetime prediction. By leveraging the low- cost unlabeled data, our model extracts hidden information to improve the understanding of the underlying patterns in the data and achieve higher accuracy in predicting battery lifetime. Our experiments demonstrate that the proposed method outperforms existing approaches by up to 19.7% on battery lifetime prediction accuracy with negligible overhead for data acquisition. Moreover, our research suggests that incorporating unlabeled data into the training process can help to uncover critical factors that impact battery lifetime, which may not be apparent with a limited amount of labeled data alone. The proposed semi-supervised PBCT approach sheds light on the future direction for efficient and explainable data-driven battery status estimation.

Reference:

1. N. Guo#, S. Chen#, J. Tao*, Y. Liu*, J. Wan*, X. Li*, "Semi-supervised Learning for Explainable Few-shot Battery Lifetime Prediction", Joule, 2024, 8, 1-17

2. Y. Liu*, S. Chen, P. Li, J. Wan*, X. Li*, "Status, Challenges, and Promises of Data-Driven Battery Lifetime Prediction under CPS Context", IET Cyber-Physical Systems: Theory & Applications, 2024, 1-11
Enhancing a-IGZO Thin-Film Transistors Performance Via Multi-Parameter Machine Learning
Authors: Yang Hyunkyu , Kim Youn Sang
Published: December 2024

Driven by miniaturization in accordance with Moore's Law, memory devices like DRAM and NAND have achieved significant performance improvements. However, this relentless scaling has encountered fundamental physical limitations, hindering further miniaturization of traditional silicon (Si)-based transistors and restricting further performance gains. To confront this challenge, research is actively exploring new materials and architectures. Among these promising candidates, the Indium Gallium Zinc Oxide (IGZO) channel transistor has emerged as particularly attractive due to its advantages in low leakage current. Despite the advantages of IGZO for low-power consumption, achieving high field-effect mobility, crucial for fast operation speeds in memory devices, remains a significant challenge.

To overcome this limitation, a novel machine learning (ML)-based approach is proposed for fabricating high-performance, ultra-thin IGZO thin-film transistors (TFTs) using sputtering process for the channel. This method optimizes the sputtering process, resulting in IGZO TFTs with outstanding multiple electrical properties simultaneously. The fabricated TFTs exhibit a high field-effect mobility of 33.2 cm²/V·s, a near-zero threshold voltage of -0.05 V, and a channel with a sub-10nm thickness. The performance of the fabricated TFTs is comparable to that of transistors produced by Atomic Layer Deposition (ALD), a technique renowned for its ability to create ultra-thin films with high quality. This achievement implies the potential of sputtering process to overcome the throughput challenges of ALD. Leveraging machine learning's strengths, the proposed method guides the optimization of the sputtering process, eliminating the need for traditional labor-intensive and trial-and-error methods. This approach has the potential to significantly accelerate the development of next-generation memory devices with unprecedented efficiency and speed.
IGZO TFT Backplane Integration for µLED Flat-Panel Display
Authors: Powell Eli , Woodard Trevor , Li Zhi , Corbett Brian , Garner Sean , Manley Robert G. , Hirschman Karl D.
Published: December 2024

Display technologies have continuously evolved since the advent of cathode ray tube (CRT) displays in the early 1900s. Thanks to modern advancements, current display thicknesses are on the order of centimeters and their area has increased 10-fold. Modern flat panel display (FPD) systems consist of a TFT backplane that controls the filtering of a backlight or the modulation of emissive devices such as OLED or microLEDs (µLEDs). MicroLED technology is favored over organic light-emitting diode (OLED) technology due to its higher brightness, energy efficiency, and longer operational lifetime. Additionally, µLEDs offer small pixel sizes, scalability to large screen sizes, and increased durability compared to OLEDs. While both technologies have their strengths and weaknesses, the choice between them depends on specific application requirements and preferences.

The primary focus of this work is the process integration of Indium Gallium Zinc Oxide (IGZO) transistors as a µLED backplane for row/column addressing. A single pixel is composed of a µLED driven by an arrangement of two transistors and a storage capacitor. The pixels are then arrayed on a glass substrate to support active-matrix control of monochrome and full color (RGB) displays from 1x1cm (50 x 50 pixels) up to 7.6 x 7.6 cm (380 x 380 pixels). Optimization of circuit parameters considering size and scan frequency was modeled using existing TFT and µLED electrical device compact models. New process parameters and procedures were determined for the proper integration of µLEDs in an existing TFT fabrication process.

Red, green, and blue µLED devices were fabricated at Tyndall National Institute on native substrates and were transferred to TFT pixels using an X-Display MTP-1003 micro-transfer printer. The performance of individual test cells was assessed using an Agilent B1500, revealing a voltage transfer characteristic indicating the ability to modulate and control µLED current. Techniques were investigated for the system integration of the active matrix with control circuitry.

Figure 1
(Invited) Ferroelectric Thin-Film Transistors for Memory and Neuromorphic Device Applications
Authors: Lee Jang-Sik
Published: December 2024

Ferroelectric materials boast a remarkable ability to maintain polarization states independently of external electric fields. This unique trait makes them ideal candidates for manipulating polarization through applied electric fields, effectively influencing the domains within these materials. By modulating polarization states, we gain precise control over channel conductance, rendering ferroelectric materials highly suitable for integration as gate dielectric layers in transistors. The incorporation of ferroelectric layers into transistors enables the regulation of channel conductance, empowering precise control over a device's electrical properties. Consequently, this enhances their effectiveness as memory elements. This innovative approach not only drives the development of high-density memory devices but also bestows ferroelectric transistors with analog memory characteristics. This quality significantly broadens their potential applications, particularly in neuromorphic devices striving to emulate the complexities of biological neural networks. In summary, ferroelectric transistors represent a promising frontier in memory technology, offering not only high-density memory solutions but also the potential to revolutionize the field of neuromorphic computing. This presentation explores these compelling prospects, detailing strategies to fully exploit the capabilities of ferroelectric materials in memory and computational applications.
(Invited) Two-Dimensional Layered Materials with Scalable and Controlled Phase/Structure-Engineered Films Toward Functional Nanoelectronics
Authors: Chueh Yu-Lun
Published: December 2024

Novel condensed matter systems can be understood as new compositions of elements or old materials in new forms. According to the definition, various new condensed matter systems have been developed or are under development in recent years. 2D layered materials, including graphene and transition metal dichalcogenides (TMDs) allow the scaling down to atomically thin thicknesses and possess unique physical properties under dimensionality confinement. The chemical vapor deposition (CVD) process is the most popular approach for all kinds of 2D materials due to its high yield and quality. In the first part of my talk, I would like to introduce the growth of high quality of 2D materials for the channel materials. Furthermore, we also demonstrated the all-transferred MoS2-based transistor arrays combing the selectively transferred MoS2 film as the channel material and the transferred Au thin films as the contact electrode, yielding uniform electrical properties with carrier mobility of 10.45 cm2V-1s-1, SS of 203.94 mV/dec, normalized Ion of 8.3 μA/μm, and on/off ratio of 105, respectively. In the 2nd part of my talk, an inductively coupled plasma (ICP) was used to synthesize transition metal dichalcogenides (TMDs) through a plasma-assisted selenization process of metal oxide (MOx) at a low temperature were demonstrated. Phase/structure-engineered-1T/2H 3D-hierarchical 2D materials derived from the MOx 3D-hierarchical nanostructures through a low-temperature plasma-assisted selenization process. The applications, including gas-/photo-sensors and resistive change memory will be reported.
(Invited) Design, Synthesis and Applications of Two-Dimensional π-Conjugated Polymers
Authors: Perepichka Dmytro F.
Published: December 2024

π-Electron conjugation in graphene gives rise to unusual electronic properties including massless charge carriers. In principle, some of these properties could be harvested in organic two-dimensional (2D) conjugated polymers which would open up the design space and tunability that are not available to inorganic 2D materials.[1] I will present our progress in synthesis of such structures as atomically thin layers on metallic surface,[2] and as bulk layered structures (2D Covalent Organic Frameworks),[3-5] via dynamic solution polymerization. I will discuss the structure-optoelectronic properties relationships in these materials and the perspectives for their applications in semiconducting devices.

[1] DF Perepichka, F Rosei, Science
2009, 323, 216.

[2] G Galeotti et al, Nat. Mater.
2020, 19, 874. D Dettmann et al, ACS Nano
2024, 18, 849.

[3] T Jadhav et al, Angew.
Chem. Int. Ed. 2019, 58, 13753. T Jadhav et al, J. Am. Chem. Soc.
2020, 142, 8862.

[4] V Lakshmi et al. J. Am. Chem. Soc.
2020, 142, 2155. E Hamzehpoor et al., in preparation.

[5] E Hamzehpoor et al. J. Am.
Chem. Soc.
2021, 143, 13274. E Hamzehpoor et al. Nat. Chem. 2023, 15, 83.
(Invited) Green Chemistry Approach to the Synthesis of Nivel Transparent Microelectronics
Authors: Castano Victor M
Published: December 2024

A review of the main developments in Green Chemistry will be presented, discussing their potential use for producing high quality optoelectronics components. A number of actual examples will be provided
(Invited) Liquid Metals for Creating Optical and Electronic Devices
Authors: Kalantar-Zadeh Kourosh
Published: December 2024

Liquid metals (LMs) constitute a group of low melting point metals and alloys that blend metallic and liquid properties. Essentially, they represent electronic liquids with intricate interfacial chemistry and physics. The softness, electrical and thermal conductivity, and distinctive interfacial chemistry of LMs have drawn significant attention across various research disciplines. These attributes render them promising materials for catalyzing chemical reactions on their surfaces to design nanoarchitectonic systems, as well as for developing diverse physical units, particularly those applicable in developing optical and electronic devices. The synergy of LM for creating semiconducting, conducting, and isolating materials in electronics is particularly unique.

The utilization of LMs as reaction media to create optical and electronic devices is gaining momentum as a paradigm. These devices are constructed from materials formed at the interface of LMs, which are either harvested from or encapsulated within the core of LM and extracted. This presentation describes such LM based reaction media and provides key examples of LM-based processes for producing functional materials. The discussion encompasses an overview of the synthesis and applications of LM-based materials in various electronic and optical applications, as well as sensing devices, illustrating their use across different physical and chemical systems. The unique features of LMs that render them promising materials for such processes will be highlighted, followed by relevant case studies and demonstrations of a variety of examples.
Doping of Tmdc-Based Device By Control of Molecule Dipole Orientations Via External Electric Field
Authors: Lai Po-Chien , Chueh Yu-Lun
Published: December 2024

Transition metal dichalcogenides (TMDCs) have emerged as promising materials in diverse electronic applications owing to their distinctive properties. Doping plays a crucial role in optimizing the performance of TMDC-based devices. In this study, we explore a novel approach to doping TMDC materials by controlling the orientation of dopants to improve material characteristics. We apply an external electric field to align permanent dipole molecules, facilitating efficient charge transfer within TMDC-based devices. This method enables precise manipulation of dopant distribution, thereby tailoring electrical properties to desired specifications. Through experimental validation, we elucidate the mechanisms governing electric field-induced dopant orientation. Our findings underscore the potential of electric field manipulation in advancing the design and fabrication of TMDC-based devices with tailored properties, thus fostering the evolution of next-generation electronic technologies.

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(Invited) Advancing Quantitative, Contactless, Non-Destructive Characterization of Photonic and Plasmonic Devices
Authors: Zapien J Antonio , Foo Yishu , Phoo May Thawda , Huqe Md Rashedul , Zhang Yun , Kwong Yee Man
Published: December 2024

Non-destructive, contactless, and fast optical spectroscopy and imaging strategies provide great advantages for the modelling and optimization of thin films and nanostructured materials in photonic and optoelectronic applications. In particular, accurate, high-precision determination of the dispersion properties of sub-wavelength materials remains challenging and overlooked despite its massively demonstrated need and benefits to the semiconductor industry. Over the years, our group has used these strategies to study self-assembled nanolasers, hybrid photonic-plasmonic sensors, and photovoltaic devices. To adapt to these challenges we develop a modelling strategy based on Finite-Difference Time-Domain (FDTD) due to its flexibility and generality that makes it suitable to model non-linear and photo-thermal effects. The advantages of FDTD include i) the ability to obtain a wide spectral response from a single time-domain simulation and ii) its capability to model non-periodic structures. Significantly, we demonstrated that quantitative FDTD modelling can achieve sub-monolayer precision thus matching the capabilities of spectroscopic ellipsometry (SE). In turn, SE stands out from other optical techniques because, as a self-referenced and phase sensitive strategy, its demonstrated precision and sensitivity and has been demonstrated in multiple spectral ranges and operation conditions. We will present and discuss the synergic use of the FDTD-SE strategy as a quantitative tool for the characterization of photonic and plasmonic subwavelength structures of interest in optoelectronic, sensing, and energy applications.

We gratefully acknowledge the financial support from the RGC (Projects CityU - 11210218, 11219919, 11215121 and 11310122) and ITC (Project ITS/461/18) of HKSAR, China.
(Invited) Ultrahigh Bulk Photovoltaic Effect Responsivity in Thin Films: Unexpected Behavior in a Classic Ferroelectric Material
Authors: Spanier Jonathan
Published: December 2024

The bulk photovoltaic effect (BPE) has drawn considerable attention due to its ability to generate photovoltages above the bandgap and reports of highly enhanced photovoltaic current when using nanoscale absorbers or nanoscale electrodes, which, however, do not lend themselves to practical, scalable implementation. I will present on how a strikingly high BPE photoresponse can be achieved in an ordinary thin-film configuration merely by tuning fundamental ferroelectric properties. Nonmonotonic dependence of the responsivity (RSC) on the ferroelectric polarization is observed and at the optimal value of the film polarization, a more than three orders of magnitude increase in the RSC from the bulk BaTiO3 value is obtained, reaching RSC close to 10-2 A W-1, the highest value reported to date for the archetypical ferroelectric BaTiO3 films. Results challenge the applicability of standard first-principles-based descriptions of BPE to thin films and the inherent weakness of BPE in ferroelectric thin films.
Topological Insulator Bismuth-Antimony Alloy Contact for Two-Dimensional Semiconductor Based Electronics
Authors: Park Hyunjun , Kwon Gihyeon , Chu Jaeyoon , Cho Mann-Ho
Published: December 2024

Two-dimensional (2D) semiconductors are considered as the most promising candidate for channel materials in next-generation electronic devices owing to their atomically thin nature [1]. In order to minimize the overall chip size, it is imperative to reduce both the channel length and the contact area of the devices. However, the reduction in contact area inevitably leads to an increase in the contact resistance (RC), and recent studies have been devoted to solving this problem. In particular, the significant achievements in reducing the RC to near quantum limits in 2D semiconductor based field-effect transistors (FET) were reported using semi-metal as bismuth (Bi) and antimony (Sb) as contact metals [2,3]. In spite of these advancements, research on the scaling-down of the metal contact with the exploration of alternative contact materials to shrink overall chip footprint remains limited.

To overcome these limitations, we propose the topological insulator (TI) as a contact metal for 2D-based electronics. TI is known to enable electron transport without backscattering at the surfaces owing to its unique surface band structures [4]. Result from these properties, the RC increase with a contact area reduction is lower compared to conventional metals, indicating high potential for TIs as an interconnector in extreme scaling regimes [5]. Additionally, the Dirac cone band structure on TIs surface [6] is expected to suppress metal-induced gap states (MIGS) similar to semi-metal contacts [2-3].

In this study, a 2D semiconductor FETs was fabricated with Bi-Sb alloy as the electrode material. Bi-Sb alloys are known to exhibit the TI phase with Sb composition ranging from 7% to 22% [7]. A 20 nm thick Ti-phase Bi-Sb alloy was synthesized using molecular beam epitaxy (MBE) on exfoliated MoS2 flakes with pre-patterned contact areas using a standard e-beam lithography process. The device was then completed by capping the TI contacts with gold. A systematic investigation of the electrical properties of the device showed that the on-current with the contact of the Ti-phase Bi-Sb alloy is enhanced compared to the bismuth-only configuration. Through this research, we aim to improve the contact characteristic of 2D based electronics in nano-scale regimes, and provide insights that can contribute to the development and commercialization of next-generation electronic devices.

References

[1] M. Chhowalla, et al., Nat. Rev. Mat, 1, 1-15 (2016).

[2] P. C. Shen, et al., Nat. 593, 211-217 (2021).

[3] W. Li, et al., Nat 613, 274-279 (2023)

[4] Y. Xia, et al., Nat. Phys, 5, 398-402 (2009).

[5] T. M. Philip, et al., IEEE Electron Device Letters, 38, 138-141 (2016).

[6] S. Tang and M. S. Dresselhaus, J. Mater. Chem. C, 2, 4710-4726 (2014)

[7] L. Fu, et al., Phys. Rev. B, 76, 045302 (2007).
(Invited) Exploring “Unconventional” Topological Nanoparticle Photonics Resonances
Authors: Giannini Vincenzo
Published: December 2024

Topological nanophotonics is a new avenue for exploring nanoscale systems from visible to THz frequencies with unprecedented control. A driving force of such a new field has been condensed matter physics. This talk will explore some phenomena that cannot be obtained in condensed matter but only in photonics. In particular, we will see that simple anisotropic nanoparticle systems allow us to project the dipolar moment in a particular direction obtaining a simple system that presents hidden symmetries in a first analysis.
Low-Temperature Evaporation Combined with Pulsed Laser Annealing for the Preparation of High-Quality p-Type Single-Crystal Tellurium-Layered Material Thin Films
Authors: Lo Chia-Hung , Chung Chia-Chen , Chueh Yu-Lun
Published: December 2024

Two-dimensional (2D) materials are currently recognized as key materials for device miniaturization due to their advantages such as perfect surface, high carrier mobility, and the ability to reduce short-channel effect. Despite significant progress in n-type two-dimensional semiconductor materials, van der Waals semiconductors with high hole mobility as the main carriers still face challenges. Tellurium layered material thin films have attracted widespread attention due to their low processing temperature and high hole mobility characteristics. Compared to other p-type 2D materials, tellurium layered material thin films offer superior uniformity and environmental durability. In this work, high-quality single-crystal p-type two-dimensional semiconductor tellurium layered material thin films were grown using low-temperature physical vapor deposition and pulsed laser annealing. This technique offers precise control over material thickness, minimal surface roughness, high uniformity, reduced defects, and improved hole carrier mobility. Electron backscatter diffraction (EBSD) analysis revealed that untreated tellurium layered material thin films had grain sizes of up to 3 micrometers. Following pulsed laser treatment, grain sizes increased to over 4 micrometers, with the main grain direction changing from (01-10) to (10-10). X-ray diffraction (XRD) results post-pulsed laser annealing showed higher peak intensities and smaller full width at half maximum (FWHM) compared to untreated and conventionally thermal annealed conditions, confirming significant enhancements in crystallinity and grain size. Additionally, minimal color change was observed in the tellurium layered material thin films after pulsed laser annealing from KAM spectra. Furthermore, significant crystallinity enhancement was also observed from high-resolution transmission electron microscopy (HRTEM) and Raman spectra.

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Exploring the Physical Characteristics of Transition Metal Dichalcogenides Under Extreme Ultraviolet (EUV) Radiation
Authors: Huang Yu-Qi , Kao Man-Yun , Hsu Che-Hao , Chueh Yu-Lun
Published: December 2024

Transition metal dichalcogenides (TMDCs) have gained a lot of attention due to their versatile applications in electronic and sensing devices. Furthermore, TMDCs are the candidates to replace Si in the semiconductor industry. However, little research focuses on TMDCs under extreme ultraviolet (EUV) radiation, which will be the mainstream lithography technique in semiconductor processes. Here, a common representative TMDC materials, MoS2 films, were subjected to synchrotron-radiation-generated EUV light. Raman spectroscopy and X-ray photoelectron spectroscopy were used to analyze the elemental concentrations and bonding environment in the materials before and after EUV irradiation. The results showed that chalcogenide vacancies in the 2D TMDCs were the dominant irradiation defects. Defects were present at all the set EUV doses, and the defect content affected the resistance of the material. This study demonstrated the defects in 2D TMDCs caused by EUV irradiation and showed the potential of EUV radiation modulating the defects and the properties of materials.