bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Modified SAB Methods for Hybrid and All-Cu Bonding for 3D Integration below 200ºC
Authors: Suga Tadatomo , Otsuka Kanji
Published: February 2024

Two methods of Surface Activated Bonding (SAB) will be proposed to enable low-temperature hybrid bonding for 3D integration.

A modified one involves surface activation processes using Ar fast-atom-beam bombardment with simultaneous co-sputtering of Si nano-adhesion layer, followed by sequential plasma irradiation with N2 radicals. These processes combine hydrophilic treatment and bonding in a low-vacuum chamber. The Si nano-adhesion layer and the sequential plasma treatment appear to enhance hydrophilicity, which enables low-temperature bonding of both Si oxides and Cu pads as hybrid bonding. Bonding in a low-vacuum environment helps to avoid void generation caused by air entrainment.

The other one is the standard SAB. But we will connect two device wafers not in a hybrid bonding but in all-Cu bonding. A small insulation layer surrounds the area around the Cu electrode on the wafers, while the rest is covered with Cu solid layers. These solid layers constitute the ground layer, power layer, or their paired layers and may contribute to heat dissipation when connected to thermal vias. The two wafers are connected only by bonding on the Cu electrodes and solid layers. The insulating parts around the Cu electrodes do not necessarily have to be bonded, and the gaps may be kept in a vacuum. Of course, the bonded surfaces need to be flattened, and a new division and layout design of the solid electrode will be required.

Cu-Cu direct bonding is possible at room temperature by applying the standard SAB directly. Of course, this requires bonding in an ultra-high vacuum condition, which inevitably reduces the throughput. However, room temperature bonding is overwhelmingly advantageous for bonding different types of devices and wafers. It is expected to become a powerful tool for 3D heterogeneous integration of devices in the future.

Figure 1
(Second Best Paper Award) Preferred Grain Orientation to Enhance Interdiffusion at Room Temperature in Atomic Diffusion Bonding: A Fundamental Study Using Ni and Cu Films
Authors: Kikuchi Shun , Goto Fuki , Shimatsu Takehito , Uomoto Miyuki
Published: February 2024

Atomic diffusion bonding (ADB) of wafers using thin metal films is a promising process to achieve room-temperature wafer bonding [1,2]. During ADB processing, the bonding performance is enhanced by crystal lattice rearrangement, which occurs when two film surfaces mutually contact at room temperature. It is reasonable to infer that the degree of the interdiffusion of the two films at the bonded interface, including crystal lattice rearrangement, depends on the surface roughness and crystallographic grain orientation of the metal films used for bonding. For this study, after Ni film and Cu film were bonded using ADB, the interdiffusion at the bonded Ni/Cu film interface was examined quantitatively using values of saturation magnetization M
s. We assessed the effects of crystallographic preferred grain orientation on the interdiffusion thickness at the bonded interface.

The Ni film thickness was fixed at 20 nm, but the Cu film thickness was varied from 5 nm to 300 nm. For both films, Ta underlayer films were used. Surface roughness S
a, as estimated using AFM of Ni(20 nm) film, was 0.25 nm. The value of S
a for Cu films increased from 0.21 nm to 0.85 nm as the Cu film thickness was increased from 5 nm to 300 nm. XRD findings revealed that both Ni and Cu films showed the (111) preferred grain orientation, but the orientation was degraded at Cu thicknesses of less than 50 nm. Figure 1 presents a STEM cross-section image of bonded Ni(20 nm)/Cu(50 nm) films as an example: no vacancy was observed at the bonded interface. Figure 2 presents values of the interdiffusion thickness T
ID for bonded films as a function of the Cu film thickness. T
IDshowed a maximum of 6.5 nm for a 50-nm-thick Cu film. S
a decreased as the Cu thickness decreased from 50 nm. However, T
ID decreased remarkably. Results suggest that deterioration of the (111) preferred grain orientation of Cu films with reduction of film thickness degraded the interdiffusion at the Ni/Cu bonded interface.

To support this assumption, Ti underlayers were used underneath Ni(20 nm) and Cu(10, 20 nm) films to enhance the degree of the (111) preferred grain orientation of these films. Results indicate that T
ID at the Ni(20 nm)/Cu(10 nm) bonded interface was enhanced to 5.4 nm, which was one order greater than that of the bonded films with Ta underlayers, indicating that enhanced bonding performance of ADB can be achieved with low surface roughness and a high degree of (111) preferred grain orientation. This enhancement is expected to be obtained also via ADB processing using other metal films having an fcc crystal structure, such as Au, Ag, and Al.

T. Shimatsu and M. Uomoto, J. Vac. Sci. Technol., B 28, 706 (2010).

T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).

Figure 1
Atomic Diffusion Bonding in Air Using Oxide Films
Authors: Shimatsu Takehito , Uomoto Miyuki , Fukunaga Hitomi , Makita Hiroyuki , Suzuki Yudai , Kozuka Yuhei , Muraoka Arina , Saito Takayuki
Published: February 2024

Atomic diffusion bonding (ADB) of wafers is a promising process to achieve room-temperature wafer bonding [1]. For ADB processing, thin films are fabricated on two flat wafer surfaces using sputter deposition, with subsequent bonding of the two films on the wafers in vacuum. In addition to thin metal films [1], both oxide [2] and nitride [3] thin films are useful for bonding.

For this study, after demonstrating ADB “in air” using oxide films, we compared the resultant bonding performance to that obtained using ADB “in vacuum” with the oxide films. Table 1 presents the surface free energy values at the bonded interface γ for quartz glass wafers bonded using 5-nm-thick Y2O3 film on each side. Using ADB in vacuum, great bonding strength was achieved for as-bonded wafers: the blade could not be inserted between the wafers. Using ADB in air, γ for as-bonded wafers was small, only 0.25 J/m2, but low-temperature annealing at 150 °C enhanced γ to 1.6 J/m2. At 200 °C, γ becomes greater than 2 J/m2. The annealing was conducted in air using a hot plate. Figure 2 portrays STEM cross-section images of Y2O3(5 nm)/Y2O3(5 nm) films (A) bonded in vacuum (as-bonded) and (B) bonded in air (annealed at 150 °C). The bonded interface is not visible in image (A). However, a slightly low-density bonded interface is partially visible in image (B). The difference of the bonded interface structure is consistent with that of γ presented in Table 1.

Various oxide films such as TiO2, ITO, SiO2, and WO3 are useful for ADB in air, as is true also for ADB in vacuum, although post-bonded annealing at a low temperature of 150 °C is necessary for ADB in air to achieve γ greater than 1 J/m2. The bonding process of ADB in air is more convenient to execute than that in vacuum. Moreover, any mirror-polished wafer can be bonded using ADB in air, as is true also using ADB in vacuum. It is likely that H2O gas in air can adsorb on the fresh surface of oxide films efficiently and that well-hydrophilic films surfaces can be obtained easily when the deposited oxide films are removed from the vacuum chambers; in fact, low-temperature annealing at 150 °C enhanced γ remarkably. ADB in air using oxide films is useful for some applications if post-bonded annealing at low temperatures is acceptable for bonding processes.

T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).

T. Shimatsu, H. Yoshida, M. Uomoto, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.51 (2021).

M. Uomoto, H. Yoshida, T. Shimatsu, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.45 (2021).

Figure 1
Improved Thermal Boundary Conductance in Annealed Direct Wafer Bonded Si-Ge
Authors: Huynh Kenny , Liao Michael Evan , Pfeifer Thomas , Yan Xingxu , Rebhan Bernhard , Floetgen Christoph , Pan Xiaoqing , Hopkins Patrick E , Goorsky Mark S.
Published: February 2024

The evolution of structural and thermal properties of wafer bonded Si|Ge with annealing is investigated in this study. Theoretical work suggests that the thermal boundary conductance between amorphous Si and Ge provide improved thermal properties as compared to a crystalline Si to Ge interface, and wafer bonded systems provides a fabrication method to experimentally test this theory [1]. EVG® ComBond® equipment was used for bonding under high vacuum (~10-8 mtorr) at room temperature to remove unwanted native surface oxides [2-4]. The bombardment of the surfaces prior to bonding produces an amorphous region at the bonded interface that has been seen in many other bonded systems [5,6]. In the as-bonded sample, high resolution scanning transmission electron microscopy revealed a ~1.2 nm amorphous region at the bonded interface. Subsequent annealing was done in an effort to recrystallize the amorphous interface. Previous work has shown that recrystallization between Si|Si wafer bonded samples occurred when annealed at 450 °C for 12 hours [3]. After annealing at 600 °C for 2 hours, the amorphous interface was observed to decrease to ~0.9 nm. Complete recrystallization is observed when the sample was annealed at 600 °C for 48 hours.

Preliminary thermal results show that the thermal boundary conductance (TBC) of the as bonded sample is 47 ± 5 MW/(m2K). The TBC for the sample annealed at 600 °C for 48 hours is 94 ± 5 MW/(m2K), an improvement by a factor of two compared to the as-bonded interface. These results demonstrate that the TBC can be improved through annealing of the interface and that improvements due to an amorphous-amorphous interface do not dominate the thermal boundary conductance in this system. We consider that the improvements are due to recrystallization of the interface and/or to increased interdiffusion, which has been observed to increase TBC in epitaxially grown Si-Ge interfaces [7].

K. Gordiz, et al., J. Appl. Phys., 121(2), p.025102 (2017)

V. Dragoi, et al., ECS Trans., 86(5), 23 (2018)

C. Flötgen, et al., ECS Trans., 64(5), 103 (2014)

M.E. Liao, et al., ECS Trans., 86(5), 55 (2018)

Y. Xu, et al., Ceramics International, 45, 6552 (2019)

F. Mu, et al., Appl. Surf. Sci., 416, 1007 (2017)

Z. Cheng, et al., Nature communications, 12(1), p.6901 (2021)

Figure 1
(Invited) Wafer Bonding for MEMS Integration and Packaging
Authors: Niklaus Frank , Jo Gaehun , Edinger Pierre , Gylfason Kristinn B. , Bleiker Simon J.
Published: February 2024

Wafer bonding is a critical manufacturing process for a vast number of experimental and commercial microelectromechanical system (MEMS) devices [1-5]. Wafer bonding is used for both the hermetic sealing of MEMS [3-5], and for integrating MEMS with electronic integrated circuits (IC) [1-2]. In this invited talk we present recent examples of wafer bonding approaches targeted at hermetic sealing of emerging MEMS devices such as silicon photonic MEMS [3, 4]. In these processes, the MEMS are sealed by wafer bonding and transferring individual lids, while at the same time keeping the final total die thickness as thin as possible. Furthermore, we also present examples of wafer bonding techniques targeted at integrating MEMS or nanoelectromechanical systems (NEMS) directly on top of electronic integrated circuits (IC), thereby closely packaging the MEMS devices with the electronic circuits that provide an interface to the outside world [1-2]. Ultimately the presented wafer bonding approaches can contribute to further miniaturization and thickness reduction of the final packaged MEMS components.

REFERENCES

[1] Fischer, A.C., Forsberg, F., Lapisa, M., Bleiker, S.J., Stemme, G., Roxhed, N. and Niklaus, F., 2015. Integrating mems and ics. Microsystems & Nanoengineering, 1(1), pp.1-16.

[2] Lapisa, M., Stemme, G. and Niklaus, F., 2011. Wafer-level heterogeneous integration for MOEMS, MEMS, and NEMS. IEEE Journal of Selected Topics in Quantum Electronics, 17(3), pp.629-644.

[3] Jo, G., Edinger, P., Bleiker, S.J., Wang, X., Takabayashi, A.Y., Sattari, H., Quack, N., Jezzini, M., Lee, J.S., Verheyen, P. and Zand, I., 2022. Wafer-level hermetically sealed silicon photonic MEMS. Photonics Research, 10(2), pp.A14-A21.

[4] Edinger, P., Jo, G., Van Nguyen, C.P., Takabayashi, A.Y., Errando-Herranz, C., Antony, C., Talli, G., Verheyen, P., Khan, U., Bleiker, S.J. and Bogaerts, W., 2023. Vacuum-sealed silicon photonic MEMS tunable ring resonator with an independent control over coupling and phase. Optics Express, 31(4), pp.6540-6551.

[5] Wang, X., Bleiker, S.J., Edinger, P., Errando-Herranz, C., Roxhed, N., Stemme, G., Gylfason, K.B. and Niklaus, F., 2019. Wafer-level vacuum sealing by transfer bonding of silicon caps for small footprint and ultra-thin MEMS packages. Journal of microelectromechanical systems, 28(3), pp.460-471.

Figure 1
(Invited) Near-Field Optics and Its Applications in Nanophotonic Devices: A Review
Authors: Wong Victor , Fanchini Giovanni
Published: February 2024

In our presentation, we will offer an overview of aperture-type scanning near field optical microscopy (SNOM) – a family of nano-optical imaging techniques derived from scanning probe microscopy which are capable of subwavelength resolution, and the development of three dimensional (3D) SNOM methods undertaken by our group to locally image the distribution of the electromagnetic radiation in the proximity of nanoparticles and nano-objects.[1] We will discuss a few applications in which we took advantage of 3D-SNOM to design specific optical nanosystems for light harvesting device applications. Specific case studies that will be presented include the design of plasmonic thin-film solar cells enhanced by random arrays of copper nanoparticles,[2] and the use of 3D-SNOM for characterizing evanescent waveguides self-assembled from of copper nanoparticles assembled on thin films of graphene.[3] In the final part of our talk, we will we present near-field scanning thermoreflectance imaging (NeSTRI), a new pump-probe technique invented in our group (see Figure 1) in which an aperture-type SNOM is used to contactlessly determine the thermal conductivity of inhomogeneous thin films and low-dimensional systems at the nanoscale for heat-spreading and thermoelectric applications.[4,5] These examples well represent the versatility of SNOM imaging and its potential for designing an even wider family of nano-optical devices.

[1] P Bazylewski, S Ezugwu, G Fanchini, Applied Sciences 7 (2017) 973

[2] S Ezugwu, H Ye, G Fanchini, Nanoscale 7 (2016) 252-260

[3] T Ouyang, A Akbari-Sharbaf, J Park, R Bauld, MG Cottam, G Fanchini, RSC Advances 5 (2015) 98814-98821

[4] S Ezugwu, S Kazemian, DYW Choi, G Fanchini, Nanoscale 9 (2017) 4097-4106

[5] S Kazemian, S Ezugwu, G Fanchini, Proc. SPIE 10926, Quantum Sensing and Nano Electronics and Photonics XVI, 109260L (1 February 2019); doi: 10.1117/12.2509828

Figure 1
(Invited) Confined and Free-Standing Perovskite Nanowires for X-Ray Detection
Authors: Wallentin Jesper
Published: February 2024

Metal halide perovskites (MHPs) have shown excellent results in many applications, including X-ray scintillation detection. Nanowires could offer improved sensitivity by exploiting nanophotonic light guiding, and the MHP stability could be improved by growing nanowires physically protected in anodized aluminum oxide (AAO). We use a one-step solution low-temperature method to grow arrays of long single-crystalline CsPbBr3 nanowires in an AAO template. The diameters can be adjusted by the AAO template, ranging from 30 to 360 nm, and the length can be controlled up to 15 μm (Fig 1(a)) [1]. The nanowires show excellent stability, with no obvious lack in photoluminescence after months of storage in air. The X-ray scintillation shows no systematic degradation over 2 weeks of continuous X-ray exposure, but an unexpected positive correlation with room humidity. The excellent stability allows tomographic 3D X-ray imaging at better than 3 μm resolution [2].

Surprisingly, we find that free-standing CsPbBr3 nanowires can be obtained by the same method (Fig 1(b)) [3]. The length of the vertically aligned nanowires is controlled from 1 to 20 μm with the precursor amount. The nanowires are single-crystalline and exhibit excellent photoluminescence and clear light guiding (Fig 1(c)). Lithography methods for MHPs have been limited because of their solubility in polar solvents. However, we show that o-xylene can be used in a perovskite-compatible electron beam lithography (EBL) process based on nonpolar solvents [4]. Combining these results, we demonstrate single nanowire devices with excellent photoresponse. Recently, we have developed a gas-phase halide exchange method based on HCl or Cl2 to convert the green-emitting CsPbBr3 to blue-emitting CsPb(BrxCl1-x)3. [5]. Using the aforementioned EBL process, we selectively convert segments of nanowires to CsPb(BrxCl1-x)3 and create axially heterostructured nanowires (Fig 1(d)).

1 Z. Zhang, H. Dierks, N. Lamers et al., "Single-Crystalline Perovskite Nanowire Arrays for Stable X-ray Scintillators with Micrometer Spatial Resolution"
ACS Applied Nano Materials 5 (1), 881 (2022) http://doi.org/10.1021/acsanm.1c03575

2 H. Dierks, Z. Zhang, N. Lamers, and J. Wallentin, "3D X-ray microscopy with a CsPbBr3 nanowire scintillator"
Nano Res. 16 (1), 1084 (2023) https://doi.org/10.1007/s12274-022-4633-7

3 Z. Zhang, N. Lamers, C. Sun, C. Hetherington, I. G. Scheblykin, and J. Wallentin, "Free-Standing Metal Halide Perovskite Nanowire Arrays with Blue-Green Heterostructures"
Nano Lett. 22 (7), 2941 (2022) http://doi.org/10.1021/acs.nanolett.2c00137

4 N. Lamers, Z. Zhang, and J. Wallentin, "Perovskite-Compatible Electron-Beam-Lithography Process Based on Nonpolar Solvents for Single-Nanowire Devices"
ACS Applied Nano Materials 5 (3), 3177 (2022) http://doi.org/10.1021/acsanm.2c00188

5 N. Lamers, Z. Zhang, I. G. Scheblykin, and J. Wallentin, "Multisegment Heterostructured CsPb(Br1-xClx)3 Perovskite Nanowires using Gas-Phase Anion Exchange"
In review (2023)

Figure 1
(Invited) Growth of Hexagonal Boron Nitride by MOCVD for Electronic and Photonic Applications
Authors: Kim Jong Kyu
Published: February 2024

Hexagonal boron nitride (h-BN) is a 2-dimensional (2D) layered insulating material. Thanks to its wide bandgap of ~6 eV and high thermal conductivity, h-BN has been widely utilized as an ideal substrate, gate dielectric material, passivation layer, and atomic tunnelling layer for 2D electronic devices. Recently, it has gained more attention as active material for photonics applications due to its potential for stable quantum emitters in the visible spectral range, as well as deep-ultraviolet emitters and detectors due to its exceptionally high internal quantum efficiency despite its indirect bandgap. However, mechanically exfoliated bulk h-BN and h-BN films grown on catalytic metal substrates by conventional chemical vapor deposition (CVD) systems have been mainly used to study the fundamental properties, lacking in scalability for practical implementation of h-BN.

Here, we exploit the scalable approach to grow h-BN on various substrates such as sapphire, Si, and GaN, by using metal-organic chemical vapor deposition (MOCVD). A few-layer h-BN films were successfully grown on those substrates. In particular, we successfully accomplished the conformal growth of few-layer h-BN over an array of Si-based nanotrenches with 45 nm pitch and the aspect ratio of ~ 7:1. Moreover, it was found that at a specific MOCVD growth condition, a very unique h-BN film can be grown on GaN substrates, in which few-layer h-BN film is suspended on GaN nanoneedles. The combination of state-of-the-art microscopic and spectroscopic analyses revealed that the suspended h-BN films exhibit unprecedented deep ultraviolet photoluminescence spectra with local variation in band-edge emission. In addition, the h-BN films show unprecedented atomic stacking configuration, the mechanism of which will be discussed with optical and structural characterizations and theoretical calculations.
(Invited) Thermoelectric Transport in Nanostructured 3D Topological Insulators and Stacked 2D Materials / Ferecrystals
Authors: Nielsch Kornelius
Published: February 2024

Research in thermoelectric (TE) quantum structures was greatly propelled by the pre[1]diction in the early 1990s of a significant boost in TE efficiency by quantum size effects. Recently, research interest has shifted from quantum size effects in conventional semiconductors toward new types of quantum materials (e.g., topological insulators [TIs], Weyl and Dirac semimetals) characterized by their nontrivial electronic topology. Bi2Te3, Sb2Te3, and Bi2Se3, established TE materials, are also TIs exhibiting a bulk bandgap and highly conductive and robust gapless surface states. The signature of the nontrivial electronic band structure on the TE transport properties can be best verified in transport experiments using nanowires and thin films. However, even in nanograined bulk, the typical peculiarities in the transport properties of TIs can be seen. The signature of TI surface states on the thermoelectric properties of nanowire model systems will be discuss in depth and how these states can be modified by chemical modifications and in the vicinity of magnetic insulators.

In the second part, we will report a different material class of stacked 2D materials based on metal monochalcogenides (MMCs), topological insulators and non-van der Waals (nvW) 2D Materials called ferecrystals via atomic layer deposition (ALD). The ferecrystals can be tailored to exhibit unusual properties such as low thermal conductivity or electronic or magnetic properties. The electronic properties of the 2D materials are modified by the interactions between the interwoven layered and non-layered materials. We have developed ferecrystal combinations, where the 2D material is the electronically active or in-active layer by selection of the bandgap for each layer.

Figure 1
(Poster Award - 2nd Place) Layer-Number Engineered Momentum-Indirect Interlayer Excitons with Large Spectral Tunability
Authors: Yao Wendian , Yang Dong , Li Dehui
Published: February 2024

The diversity of two-dimensional (2D) materials provides van der Waals heterostructures with abundant degrees of freedom and makes the family a promising candidate to realize novel optoelectronic devices and an attractive platform for exploring physical phenomena. Interlayer excitons in type-II van der Waals heterostructures are equipped with an oriented permanent dipole moment and long lifetime and thus would allow promising applications in excitonic and optoelectronic devices. However, in the widely studied van der Waals heterostructures constructed by transition metal dichalcogenides, the formation of interlayer excitons is limited by the lattice mismatch, rotational and translational alignment between the constituent layers, increasing the complexity of the device fabrication. Here, I will report on the robust momentum-indirect interlayer exciton emission with widely tunable emission energy via layer engineering in transition metal dichalcogenide/2D perovskite heterostructures. The transition metal dichalcogenides with different thicknesses and 2D perovskites with different layer numbers of the inorganic octahedral slabs are stacked to form type-II van der Waals heterostructures without considering special orientation arrangement and momentum mismatch. The presence of interlayer excitons is supported by the excitation-power- and temperature-dependent photoluminescence studies, photoluminescence excitation spectroscopy, time-resolved photoluminescence decay studies and electric field-dependent photoluminescence studies. Taking advantage of the thickness- or layer-number-dependence of the electronic band structure of the constituent materials, the emission energy of the interlayer excitons in our heterostructures can be tuned from 1.3 eV to 1.6 eV, providing strong evidence for the applications of van der Waals interface engineering to broad-spectrum optoelectronics. In addition, the diffusion coefficient of interlayer excitons in our heterostructures can be estimated to be ~10 cm2 s−1, which is at least one order of magnitude larger than that in the van der Waals heterostructures with Moiré superlattice, suggesting a non-localized nature that would be beneficial to the excitonic devices. Our study would offer new insights into the nature of interlayer excitons and provoke further research into their dynamics.
(Invited) Self-Powered Image Sensors Based on Vertical Van Der Waals 2H/1T' -MoTe2 Homojunctions
Authors: Hu Yunxia , Gao Zhaoli , Luo Zhengtang , Huo Xiaoyu
Published: February 2024

Image sensors can convert optical images into electrical images, which play important roles in industrial application fields and emerging applications, including digital cameras, biomedical imaging, and machine visions. [1, 2] Compared to traditional three-dimensional rigid materials, two-dimensional (2D) materials with excellent electrical, optoelectrical, and mechanical properties exhibit great potentials in novel image sensors. This work aims to synthesize large scale van der Waals 1T’/2H MoTe2 homojunctions and fabricate image sensors for self-powered imaging functions. Firstly, a two-step chemical vapor deposition (CVD) method is adopted to synthesize the 1T’/2H MoTe2 homojunctions via tellurization process of molybdenum film. Secondly, the structural design of the self-powered photodetector based on 2H MoTe2 with asymmetric electrodes and the corresponding optoelectrical properties are investigated. [3] Thirdly, an image sensor consisting of a self-powered MoTe2 photodetectors array is constructed and exhibits excellent imaging functions with zero power electrical consumption. This work will open a new route to build image systems based on 2D materials, showing great opportunities in digital image systems with ultralow power consumption and excellent imaging functions.

Acknowledgement

This work was fully supported by a grant from the National Natural Science Foundation of China (Project No. 52022003).

References

[1] S. Goossens, G. Navickaite, C. Monasterio, S. Gupta, J. J. Piqueras, R. Pérez, G. Burwell, I. Nikitskiy, T. Lasanta, T. Galán, E. Puma, A. Centeno, A. Pesquera, A. Zurutuza, G. Konstantatos, F. Koppens, Broadband image sensor array based on graphene–CMOS integration. Nat. Photonics 11 (2017) 366-371.

[2] M. Bigas, E. Cabruja, J. Forest, J. Salvi, Review of CMOS image sensors. Microelectron. J. 37 (2006) 433-451.

[3] H. Qiao, Z. Y. Huang, X. H. Ren, S. H. Liu, Y. P. Zhang, X. Qi, H. Zhang, Self‐powered photodetectors based on 2D materials. Adv. Opt. Mater. 8 (2019) 1900765.
(Invited) Low-Dimensional Carbon Materials - Synthesis and Properties
Authors: Wågberg Thomas
Published: February 2024

Low-dimensional carbon materials, such as graphene, graphene nanoribbons, PCBM, and carbon nanotubes have been frequently applied in various devices and applications for energy conversions. These system possess fundamentally interesting electronic, mechanical and optical properties that can be used beneficially to optimize performance of such devices, but concurrently their usage is challenging due to their diversity and controllability. Here we give presentation of the usage of graphene, graphene nanoribbons, PCBM, and fullerene nanorods for applications as solar cells, field-effect transistors, and PV-driven electrolysis. We are covering all aspects from synthesis to device performance, with an emphasis on properties such as charge transfer, charge mobility and how these properties relate to device performance.

Figure 1
(Invited) Photoactive Inorganic Nanosystems for Environmental and Energy-Related Applications
Authors: Moretti Elisa
Published: February 2024

Nowadays, one of the main technological challenges that we are facing is the ability to provide a sustainable supply of clean energy and, among all renewable sources, solar energy displays the greatest potential. Recently, the development of novel synthetic strategies has led to the preparation of nanostructured materials displaying unique properties compared to the bulk counterpart systems, with controlled and tunable morphologies able to enhance the activity and selectivity of a heterogenous process.

This talk will focus on the importance of tuning the morphological features of a catalyst as a strategy to improve its photoactivity, focusing on how rationally designing inorganic materials at the nanoscale can lead to shapes and structures suitable to enhance the performance of industrially and environmentally important processes. The talk will discuss some energy and environmental applications that can be addressed by multi-component systems synthesized via the bottom–up approach, highlighting their structure-reactivity relationship. Photocatalytic H2 production and purification and drugs degradation will be presented as successful cases history [1-3].

[1] E. Moretti, L. Storaro, A. Talon, P. Riello, A. Infantes Molina, E. Rodríguez-Castellón, Appl. Catal. B: Environmental 168 (2015) 385.

[2] M. Telkhozhayeva, B. Hirsch, R. Konar, E. Teblum, R. Lavi, M. Weitman, B. Malik, E. Moretti, G.D. Nessim, Appl. Catal. B: Environmental 318 (2022) 121872.

[3] L. Liccardo, M. Bordin, P.M. Sheverdyaeva, M. Belli, P. Moras, A. Vomiero, E. Moretti, Adv. Funct. Mater. (2023) in press.
(Invited) Piezocatalysis for Treating a Massive Industrial Dye Solution and Hydrogen Production
Authors: Wu Jyh Ming
Published: February 2024

As a fossil fuel substitute, among the various renewable alternative energy sources, hydrogen fuel is a clean energy source being developed in advanced industrial nations worldwide. Photocatalytic water splitting yields hydrogen through redox reactions underlying direct water decomposition. Although water splitting is a promising method of yielding clean energy from the sunlight without contaminating byproducts, sunlight is a desultory source of energy, which limits the amount of solar radiation owing to its dependence on time (day or night), geographical position, and season.Redox reactions remain one of the most promising methods of producing hydrogen and decomposing industrial wastewater. However, for most critical practical industrial applications, the robust light attenuation of wastewater results in meager quantum yield, thus significantly limiting the commercial applications of photocatalysis. Therefore, novel approaches to evaluating parameters, including cost-effectivity, high efficiency, and long-time stability, are highly desirable for developing next-generation catalysts. In particular, such technology would be up-and-coming for simultaneously producing hydrogen gas and decomposing industrial wastewater without light irradiation. This talk will report how 2D transition metal dichalcogenides can be used for piezocatalyts for highly efficient wastewater treatment of a massive industrial dye solution and hydrogen production without applied light irradiation by utilizing a closed-loop system with a low-frequency natural water flow. Our newly developed piezoelectrocatalysts system provides the first evidence of the effective production of hydrogen gas and the simultaneous decomposition of dye molecules in wastewater without light irradiation, thus providing a promising method for treating industrial wastewater and producing clean energy.
(Invited) Wireless Healthcare Flexible Sensor System
Authors: Takei Kuniharu
Published: February 2024

Daily continuous health condition monitoring is now of great interests using multi-functional flexible sensors. In particular, vital signals from skin are the most convenient way to measure continuously data collections during daily life. For this purpose, flexible sensor sheets allow it to detect multiple information 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.
Modeling Competitive Reaction Heat Sources and Variable Cooling Rates Applicable to Thermal Runaway Onset in Lithium-Ion Batteries
Authors: Shurtz Randy C. , Kurzawski Andrew , Hewson John
Published: February 2024

Two main types of exothermic processes are known to initiate thermal runaway in Lithium-Ion batteries. If mechanical failure of the separator causes an electrical short circuit, the cell’s energy can be released through electrochemical discharge reactions. The full stored energy can be released as heat within the cell for internal short circuits, raising the cell temperature by several hundred degrees Celsius. Different thermochemical reactions occur when Lithium-Ion cells are heated; the anode and cathode materials decomposing with the electrolyte can result in similarly large temperature rises. Our work shows that thermodynamics constrain key reactant species for both decomposition paths to be in common. Interactions and competition between these chemical pathways for heat release are considered in this modeling study, including relative magnitudes of thermal contributions from each reaction pathway and limiting reactant effects. An effective oven temperature concept is defined, which allows thermal runaway initiation via internal short circuits versus external heating to be compared. Temperature and reaction inhomogeneities occurring in the presence of internal localized internal short circuits lead to variations in the balance between electrochemical and thermochemical reactions across the domain of the cell. A simple homogeneous analysis is compared to a higher-dimensional inhomogeneous analysis. The effectiveness external cooling strategies to mitigate an internal short circuit event is investigated.

Acknowledgements:

This article has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in and to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan https://www.energy.gov/downloads/doe-public-access-plan. This abstract has been approved for release as SAND2023-01585A.
Investigation of the Effect of Safety Function Failure in Lithium-Ion Battery Systems at High Overvoltage
Authors: Haß Jan , Schieber Christina , Jaroch Nikolas , Meilinger Florian , Schweiger Hans-Georg
Published: February 2024

Balancing circuits in lithium-ion cell battery systems have the task of compensating for deviations in the capacity of the individual cells that arise due to manufacturing tolerances and ageing effects. It must be noted that a malfunction of this system can lead to great damage or even the destruction of the battery system. If cells are continued to be charged due to a fault in the BMS, the current interruption device (CID) will be the last protective function of a cell against overcharging. This irreversibly separates the positive and negative poles of the cell, and the cell’s resistance suddenly increases dramatically. The process of triggering the CID can also be triggered by the ageing process of the cell or other internal faults in the cell. If cells are interconnected to battery systems, a large voltage drop can be observed at the cell with a triggered CID, if a load is connected to the battery system. Under normal overcharge test conditions, cells are tests with twice the nominal cell voltage. In this case, the CID also functions correctly, and the charge current is interrupted. At significantly higher voltages, which occur in the cases described above, voltages close to maximum system voltage can be observed. At these voltage levels, the CID may not work properly. E.g., by overcharging and possible explosion of the cell may occur. For a more detailed investigation, a test series with 3 different chemistries was realized and the overcharge with 3 different voltage levels was investigated. It was found that on the investigated conditions, a more severe cell behavior was observed. Therefore updating abuse testing procedure are recommended or the usage of CIDs in cells battery systems should be avoided.

Figure 1
In-Situ Quantification of the Ageing Dynamics in Lithium-Ion Cells up to Failure-Near Conditions
Authors: Scharpmann Philippa , Leonhardt Robert , Tichter Tim , Schmidt Anita , Krug von Nidda Jonas
Published: February 2024

Implementing end-of-life (EOL) lithium-ion batteries from automotive applications in stationary energy storages is of utmost relevance for a sustainable handling of scarce resources. Beneficial from an economic and ecological perspective, such second-life applications urgently require a guarantee for safe operation. Unlike the state of health (SOH), defined by classical performance indicators such as capacity and voltage, the state of safety (SOS) of an aged battery cannot be assessed straightforward. Its determination requires a plethora of cells to be tested which is a particular challenge for new technologies with limited access to EOL batteries.

For providing cells with a defined SOH at a reasonable timescale, we herein propose a novel method of greatly accelerating the ageing process of lithium-ion batteries. In a preliminary test series, lithium-ion NMC pouch cells are exposed to incrementally increasing temperatures, current rates and/or states of charge (SOC), until thermal runaway is induced. In this manner, the critical state in proximity to cell failure is spotted for individual and combined stress parameters. Based on this knowledge, cell-specific test parameters for heavily accelerated ageing are developed. In this protocol, electrical abuse conditions are defined by over/under charging and high current rates. Typically, the cells are cycled utilizing a depth of discharge above 100 %.

The accelerated aging dynamics under these critical conditions are monitored by systematic capacity, open circuit voltage and electrochemical impedance spectroscopy (EIS) measurements. This enables a comparative assessment of the electrical behaviour, following conventional vs. heavily accelerated ageing. Such knowledge will in turn help to define the threshold to which cyclic ageing can be accelerated without changing the characteristic degradation mechanisms of lithium-ion batteries.
Investigation of Water Ingress Driven Circuit Board Faults As a Contributory Factor to Battery Thermal Runaway
Authors: Johns Phillip , Torelli Daniel
Published: February 2024

Recent high-profile examples of battery fires in electric vehicles (EV’s) during the aftermath of Hurricane Ian [1] have led to increased public visibility of the susceptibility of EV batteries to thermal failure due to water immersion or ingress.

Although clearly an issue for manufacturers and users of automotive EV’s, this issue poses a particular challenge in the rapidly increasing micromobility market with nearly 800 million battery powered 2- and 3-wheeled vehicles (such as e-bikes or scooters) expected to be in operation by 2040 [2]. With privately owned micromobility vehicles generally not subject to the rigorous servicing or maintenance schedules of automotive EV’s, and fleets of rented e-bikes / scooters subjected to prolonged rough handling and environmental exposure, the risk of failure in these vehicles due to improper handling, water ingress or mechanical abuse is very real.

Testing and failure recreation of thermal runaway in lithium-ion based micromobility battery packs within Exponent’s European laboratory (London) has shown that even small amounts of moisture ingress to sensitive electronic components of the battery pack, such as the battery protection circuitry, can lead to thermal runaway of the cells within the battery pack. Such failures are often highly dependent on battery pack design (and physical condition) and may only manifest in the days or weeks after water immersion or ingress.

The study presented here investigated specific conditions and behaviours of saltwater ingress-driven circuit board faults in lithium-ion battery packs, and demonstrated localised temperature increases of ~100 °C, even at relatively low fault currents (mA’s), showing the potential for circuit board faults to propagate to cell thermal runaway.

Further studies investigated the effect of full, partial and targeted immersion of lithium-ion battery packs in 5 wt% NaCl solution, demonstrating the influence of the volume of water ingress and ingress location within the battery pack on the potential for battery thermal runaway. This paper will also discuss design aspects and/or mitigation methods to protect from such failure modes.

[1] - https://content.govdelivery.com/accounts/USDHSFACIR/bulletins/333744b

[2] - https://www.faraday.ac.uk/wp-content/uploads/2023/02/Faraday_Insights_16_FINAL.pdf
Challenges and Solutions for Integration of Energy Storage Systems in Hot Desert Regions
Authors: Maher Kenza
Published: February 2024

The increasing utilization of solar renewable energy sources in the Gulf Cooperation Council (GCC) regions, including countries such as Saudi Arabia, the UAE, and Qatar, highlights the pressing need for energy storage systems (ESS) to ensure grid stability. ESS can store excess energy during peak generation and supply it during periods of low generation or high demand. However, the harsh environmental conditions and extreme temperatures that are typical of hot desert regions can impact the performance and lifespan of ESS, creating unique integration challenges.

Our work explores these challenges and offers solutions for integrating energy storage systems in hot desert regions. Our research shows that while the integration of ESS in hot desert regions is technically feasible and economically viable, it requires careful planning, design, and maintenance to ensure optimal performance and longevity. The solutions we present in this work can provide valuable guidance for engineers, policymakers, and stakeholders who are working towards a sustainable and resilient energy future in hot desert regions.

During the presentation, I will delve into the specific challenges that the harsh environmental conditions and extreme temperatures in hot desert regions pose for the integration of energy storage systems. I will provide examples of how these challenges can impact the performance and lifespan of ESS. Furthermore, I will highlight the solutions that we have identified and presented in our research, which can help overcome the challenges and improve the effectiveness of energy storage systems in hot desert regions.
(Invited) Improving Certainty in Battery Safety Profiles through Early-Stage Evaluation
Authors: Bates Alex Martin , Albertus Paul , Jeevarajan Judith , Mukherjee Partha P. , Torres-Castro Loraine
Published: February 2024

There is currently a great desire to reduce carbon emissions through electrification of all transportation sectors by utilizing battery energy storage. However, existing technology is unable to meet the performance target demands of certain transportation sectors (e.g., aviation). As a result, and due to a growing demand for conventional Li-ion battery materials, there is significant motivation to generate new battery technologies. During early-stage of development, the primary focus is demonstrating the achievement of performance metrics for the anticipated application. Once performance metrics have been demonstrated, the focus turns to scale-up. It isn’t until the later stages of development, perhaps even during the push for large scale manufacturing, that safety is more closely analyzed. At that stage, a significant amount of research dollars has been invested into that technology. To complicate matters, it is widely understood that the safety profile of large format cells (e.g., multi-layer pouch cells) can be significantly different than the safety profile of small format cells (e.g., coin cells) of the exact same chemistry.

The work presented here examines the gap that exists in the understanding of a commercial-scale full cell's safety characteristics through a combination of characterization, experiments, and modeling using only information gained at the lab-scale, early-stage development (i.e., materials and small format cells). Characterization and experiment will be developed in such a way as to determine and quantify key metrics that will be utilized as modeling inputs. A modeling framework will utilize those key metrics to predict the large format safety profile of a specific chemistry. Experimental work, where cells are exposed to abusive conditions, will allow for the refinement of input parameters and refinement of the modeling framework to increase certainty in large format safety profile. This talk will highlight the planned approach to utilize a battery technology’s materials and small format cells to develop a picture of what may be expected in the safety profile of a large format cell.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
New Method for Designing Robust External Short-Circuit Protection Systems at Different Scales
Authors: Kriston Akos , Bonato Christian , Pfrang Andreas
Published: February 2024

External short circuit is one of the failure modes of Li-ion and other batteries that potentially leads to serious damage such as, overheating and/or thermal runaway. Therefore in this work we test and analyse the short circuit behaviour of different system sizes from coin cells, 10Ah pouch cells and upto large scale automotive high voltage battery packs. It was found that the complex short circuit behavior can be described by 3 regions independently of the size of the battery. In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature is reached and cell rupture, venting and electrolyte leakage may occur. Then the current stabilizes at the maximum mass transport region independently of the external short circuit. This complex time behavior need to be covered by different fuses, circuit breaker and intelligent battery management system. The protection strategy depends on several factors, which makes the design process complex. We introduce the normalized resistance ratio which allows the comparison of external shorts with different external resistance and cells and with different capacities. We demonstrate that the estimation of the maximum external short circuit current derived in this work is more accurate than other calculations at different levels. Furthermore we developed and present a generalized visualisation of the full time-current window which potentially help scientists and engineers to design more robust external short circuit protection systems. With this method we also demonstrate that the currently used external short circuit design methods may potentially lead to unsafe regions especially in the soft short region. We also propose a testing protocol which can be applied in standards, regulations without jeopardizing the safety of testing personnels and infrastructure.