bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiscale Materials and Process Engineering for Efficient CO2 Recycling
Authors: Roy Soumyabrata , Wu Jingjie , Kibria Md Golam , Ajayan Pulickel
Published: December 2024

Renewable electricity powered conversion of carbon dioxide (CO2) to fuels and chemicals has potential to close the anthropogenic carbon cycle at meaningful scales and achieve global sustainability goals. It provides an effective route to store renewable energy in chemical bonds for its modular utilization in a circular carbon economy. However, the technological progress of this complex chemical transformation is stymied due to the lack of systematic materials design principles, poor understanding of the convoluted reaction pathways that control efficiency and selectivity, and complexities associated with elementary electron and mass transfer in the reaction environment. At a system level, issues of carbon and energy conversion efficiencies needs to be addressed. Engineering of materials and interfaces can have profound effects on the correlated bulk and surface physicochemical properties for judicious tuning of these parameters and reaction pathways. In my talk, I will present examples of our research to build a broad perspective on how the rational design of materials and processes can solve some key scientific/technological challenges in electron-driven CO2 recycling pathways through understanding of structure-activity correlations. On the materials aspect, engineering of low dimensional carbon and copper based systems will be discussed. Integration of electrochemical CO2 conversion with capture and alternative anodic oxidation reactions will be showcased to highlight emerging approaches in addressing technological challenges from a process perspective.
Fabrication and Characterization of Low Loading Dimensionally Stable IrOX Electrocatalyst for Oxygen Evolution Reaction
Authors: Kumar Prasoon , McKee Austin , Alsaedi Sattar , Jawahar Hussaini Syed Mubeen
Published: December 2024

Electrochemical water splitting is a promising technology to produce green hydrogen. Industrial water electrolysis occurs in proton exchange membrane electrolyzer but the technology faces limitation which reduces its industrial adoption and market competitiveness. The utilization of precious and rare materials like platinum, iridium or ruthenium as HER and OER electrodes is one of the main challenges plaguing the development of this technology. Unfortunately, nature presents us with an irony: most efficient electrocatalysts are the rarest of element. Hence an efficient strategy is to reduce their mass loading without compromising on its catalytic efficiency. Electrochemistry gives us the flexibility to deposit a “net” desired amount of catalytic material without wastage. In this study we present an electrochemical technique to fabricate a dimensionally stable iridium-based oxygen evolution catalyst with significantly less mass loading (~0.3mg/cm2) which exhibits comparable activity (overpotential of ~320 mV at 10 mA/cm2) and stability (>150 hrs) in contrast to commercially available catalyst in acidic media.
Pd 4d Orbital Overlapping Modulation on Au@Pd Nanowires for Efficient H2O2 Production
Authors: Deng Zhiping , Wang Xiaolei
Published: December 2024

Electrochemical synthesis of hydrogen peroxide has been emerging as an appealing process for the onsite production of this chemically valuable oxidant, while the catalyst design for H2O2 production is conducted mainly using trial-and-error approaches. It results in any knowledge acquired of active sites and catalytic mechanisms remains opaque and empirical. Herein, we design a series of Au@Pd core-shell structure nanowire to reveal the quantitative structure-performance correlation in atomic level. The structure of Pd shell was controlled by the amount of PdCl2 precursor, to achieve the epitaxial-growth of several atom layer, one layer, and surface site isolation. Electrochemical evaluation shows the selectivity is relevant to the surface structure and composition. With the reducing of surface Pd deposition, the predominant ORR mechanism on catalyst changes from the 4e- to 2e- pathway to produce H2O2. Moreover, a high kinetics mass activity (5.71 A mg-1 at 0.4V) of Au@Pd(15:1) NWs is achieved, which is almost three times larger than the state-of-the-art Pd-Hg alloy catalyst. The excellent performance can be attributed to the unique structure of Pd shell with low Pd-Pd coordination number, active sites isolation, and high Pd utilization efficiency. Structural and electrochemical analysis reveal that Pd4 structure is crucial for the ensuring high selectivity. Particle size beyond Pd4 will be more beneficial for driving the 4-electron pathway to produce H2O. Interestingly, our initial theoretical prediction by Density Functional Theory (DFT) calculations demonstrates Pd4 is a 4-electron catalyst that binds *OOH intermediate too strongly. Such discrepancy is from the oxygen coverage phenomenon under operando conditions. The oxygen coverage on Pd4 surface causes electron redistribution and weakened *OOH binding strength. It pushes Pd4-O to the peak of the volcano plot with only 0.06 eV difference from the ideal value.
Ligand-Functionalized Membranes for Lithium-Selective Electrodialysis Separations
Authors: Abels Kristen , Barbosa Botelho Amilton , Chen Xi , Tarpeh William Abraham
Published: December 2024

Selective electrodialysis requires further development of ion-selective membranes to enable the selective recovery of target ions from aqueous streams. In this work, we evaluated a library of commercial membranes to assess their potential for ion-ion separations and to elucidate the fundamental mechanisms of ion permselectivity in these materials. This screening of commercial membranes confirmed the limitations of size and electrostatic selectivity mechanisms in the separation of ions of similar size and/or charge. We then synthesized a library of novel ligand-functionalized membranes to study the impact of additional ion-specific coordinative interactions on lithium permselectivity under diffusive transport and selective electrodialysis. The complete characterization of the library of novel, ligand-functionalized membranes provides additional experimental data on the effect of not only ligand-cation interaction free energies, but also the effect of ligand grafting densities on ion permeabilities and permselectivities. For example, variation of membrane pyridine content from 0-50 mol% in a subset of the membrane library was found to have substantial impact on lithium/nickel permselectivities, including 3-4 times higher than the permselectivities measured with the commercial membranes. In the future, these experimental results could support further development of ion transport theory in ligand-functionalized membranes with ligand grafting densities included as model parameters. This work could also lead to future grafting density optimization studies with the goal of maximizing ion permeability and/or permselectivity. Membranes were also tested in four-chamber electrodialysis reactors to characterize performance during electrolysis; selectivity was still observed during operation.

Note: This presentation reflects research funded by an ECS/Toyota Young Investigator Fellowship.
Fundamentals Studies of Sludge Electrolysis Using Bovine Serum Albumin (BSA) as a Model Compound
Authors: Abbasi Ehsan , Alvarez Pugliese Christian E , Botte Gerardine G
Published: December 2024

The Haber-Bosch process is the main industrial practice for producing ammonia, known for its energy intensity. Current ammonia production is unsustainable, and the overuse of synthetic fertilizer has led to significant environmental impact in air, water, and soil. Organic waste, such as sewage sludge from domestic wastewater treatment plants represents a valuable resource for nitrogen recovery, containing approximately 6% nitrogen content (1) in dry basis.

Electrolysis of waste activated sludge (WAS) has the potential to recover nitrogen from this slurry waste (2-3), where nitrogen is mainly present in the form of proteins constituting 30-40% of the total solids in sludge (4). Developing efficient electrochemical processes to valorize organic waste such as WAS is critical to achieving sustainability goals, protecting the environment, and enabling economic development and growth (5). While efforts have been made to employ sludge electrolysis at high to moderate voltages to mineralize the organic matter completely or partially, the optimal scenario for electrolysis would involve the selective transformation of sludge components into valuable products like ammonia and other nutrients that can be further separated as a fertilizer (4). However, the complexity of sludge components, such as proteins, their solubility, denaturation, and structural variability, presents one of the main challenges that needs to be addressed in the process.

Given the complexity of real sludge, it is reasonable to begin with a model compound such as a protein to understand the fundamental behavior of the system. Bovine Serum Albumin (BSA) is a globular protein that contains approximately 15-17 percent nitrogen by weight. This protein is relatively inexpensive, readily available, and possesses appropriate structural complexity for fundamental studies. In this presentation, the most recent results for the electrochemical oxidation of BSA will be discussed, aiming to provide a better understanding of the mechanism of reaction of complex organic nitrogen compounds.

Reference:

D. Bolzonella, C. Cavinato, F. Fatone, P. Pavan and F. Cecchi, Waste Management, 32, 1196 (2012).

M. Jafari and G. G. Botte, Frontiers in Chemistry, 10, 974223 (2022).

M. Jafari and G. G. Botte, Journal of Applied Electrochemistry, 51, 119 (2021).

K. Xiao and Y. Zhou, Journal of Cleaner Production, 249, 119373 (2020).

C. Alvarez-Pugliese, D. Donneys-Victoria, W. J. Cardona-Velez and G. G. Botte, Current Opinion in Electrochemistry, 46, 101508 (2024)
Understanding the Amorphous Structure of Al- and Zn- Doped TiO2 with an Automated 4D-STEM Analysis Pipeline
Authors: Werbrouck Andreas , Paranamana Nikhila C , He Xiaoqing , Young Matthias J.
Published: December 2024

In the landscape of techniques to better understand and engineer (battery) materials and their interfaces, 4D-Scanning Transmission Electron Microscopy (4D-STEM) takes a unique and powerful place. This technique is an extension or regular STEM, where 2D diffraction data is available for every imaged pixel. Because of the high energies available at the TEM, it is not only possible to collect Bragg diffraction data, but also to characterize amorphous phases through electron-based Pair Distribution Function (ePDF) analysis, unearthing subtle, but relevant effects. Additionally, structural data can be combined with co-located Energy-Dispersive X-ray spectroscopy (EDS) data. However, the large volume of data and the complexity of diffraction analysis makes manual processing of 4D-STEM data prohibitively slow.

To solve this, and to leverage the possibilities of collecting spatially resolved structural and compositional data, we developed an automated workflow for analyzing 4D-STEM data. This workflow is cast as a Directional Acyclic Graph (DAG). First, the 4D data is split into spatially mapped crystalline and amorphous components. Then, non-local averaging and non-negative matrix factorization distill the amorphous data into a low number of higher-quality pair distribution functions (PDFs). Finally, these can be structurally refined using reverse Monte Carlo (RMC) fitting and molecular dynamics (MD).

Here we demonstrate the characterization of the amorphous structure of undoped and doped TiO2: a simple, yet very relevant system. TiO2 finds uses in lithium-ion-based energy storage, catalysis and microelectronics. One of the reasons for its attractiveness is the possibility to tune the functional properties by means of the structure: e.g. the conductivity of the material changes by means of doping and/or phase selection through annealing (anatase vs rutile). Amorphous TiO2 is subject to similar effects. Indeed, small concentrations of impurities (e.g. precursor ligands) may have a large impact on the final structure. Similarly, subtly different structures may arise at the substrate-film or film-vacuum interface. This will affect the functional properties of the films. TiO2 was deposited by atomic layer deposition (ALD) with TiCl4 and water, using AlMe3 and ZnEt2 as precursors for respectively Al and Zn doping.

Our automated approach greatly reduces the amount of time and effort necessary to interpret the data in a meaningful way. Specifically, for the TiO2, we can clearly observe how even a low level of Zn, Al and Cl impurities profoundly alter the amorphous structure. In other work submitted to this conference, we used the same approach to analyze complex, multi-element battery interfaces. Through this effort, a better understanding amorphous materials and interfaces can be gained, which can then serve as a stepping stone to study and engineer electrochemical electrode and catalyst interfaces.
Scalable Synthesis of Pt on Carbon Black Via Atomic Layer Deposition and Catalyst Layer Fabrication for Proton Exchange Membrane Water Electrolysis
Authors: Kraenbring Mena-Alexander , Piechulla Peter , Chen Mingliang , van Ommen J. Ruud , Özcan Fatih , Segets Doris
Published: December 2024

Proton exchange membrane (PEM) water electrolysis has emerged as a pivotal technology for sustainable hydrogen production, offering a clean and efficient pathway to generate hydrogen from water using renewable energy sources. Novel Pt/C catalysts fabricated via fluidized bed reactor atomic layer deposition (FBR-ALD) present promising advancements for PEM water electrolyzer cathode catalyst layers. The process enables a uniform and controllable deposition of Pt nanoparticles onto carbon support materials, enhancing catalytic activity and stability [1]. The resulting catalysts demonstrate improved electrochemical performance in PEM water electrolysis, attributed to optimized Pt dispersion and enhanced catalytic sites [2]. This study explores the synthesis and further processing of these catalysts into catalyst inks and subsequently cathode catalyst layers for water electrolysis, leveraging the precise control and scalability offered by FBR-ALD to minimize the Pt loading while maintaining high catalytic activity and performance. Detailed layer characterization techniques, including atomic force microscopy (AFM) and electrochemical analyses, elucidate the structural and electrochemical properties of the Pt/C catalysts. Insights gained from this research contribute to a decrease in expensive platinum group metal employment and the scalable development of efficient, cost-effective, and durable catalyst materials for hydrogen production through PEM water electrolysis.

[1] F. Grillo, H. Van Bui, J. A. Moulijn, M. T. Kreutzer, and J. R. van Ommen, “Understanding and Controlling the Aggregative Growth of Platinum Nanoparticles in Atomic Layer Deposition: An Avenue to Size Selection,” J. Phys. Chem. Lett., vol. 8, no. 5, 2017. doi: 10.1021/acs.jpclett.6b02978.

[2] W.-J. Lee, S. Bera, H.-C. Shin, W.-P. Hong, S.-J. Oh, Z. Wan, S.-H. Kwon, Uniform and Size-Controlled Synthesis of Pt Nanoparticle Catalyst by Fluidized Bed Reactor Atomic Layer Deposition for PEMFCs. Adv. Mater. Interfaces 2019, 6, 1901210. doi: 10.1002/admi.201901210
Development of Autonomous Reactor for High-Throughput Exploration of Electrically Conductive Copolymers Using Vapor-Phase Deposition
Authors: Gopaul Colin , Mehregan Mahya , Werbrouck Andreas , Gettler Ryan C , Paranamana Nikhila C , Brorsen Kurt P , Young Matthias J.
Published: December 2024

In the 1980s, it was reported that under specific synthesis conditions, polyacetylene, a conjugated polymer, could exhibit electrical conductivities in excess of 100,000 S/cm—putting it within striking distance of inorganic metals. However, polyacetylene is not air stable. Other air-stable conjugated polymers including poly(3,4 ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) exhibit electronic conductivities of only ~100-1000 S/cm. These lower electronic conductivities are thought to arise because the homogeneous polymerization methods conventionally used to produce these conjugated polymers lead to a stochastic distribution of molecular structures. The random distribution of molecular structure in these polymers makes it difficult to understand what aspects of the molecular structure restrict electron transport. This in turn limits the ability to rationally improve the conductivity. Recent work from our group has demonstrated monomer by monomer growth of this class of conjugated polymers through self-limiting vapor-phase oxidative molecular layer deposition (oMLD). Taking advantage of the molecular sequence control that can be achieved through oMLD, it is now possible to explore how molecular structure influences electronic conductivity. In this report, we describe the development of an autonomous reactor with multimodal in situ characterization including electronic conductivity, spectroscopy, and thickness measurements. Employing machine learning (ML) algorithms, the reactor we describe will operate autonomously to establish fundamental understanding of how synthesis conditions drive molecular structure, and how molecular structure drives properties.
Conformal Conductive Polymer Deposition on Carbon Nanotube Forests
Authors: Reinhard Andrew , Mehregan Mahya , Maschmann Matt , Young Matthias J.
Published: December 2024

Carbon nanotube (CNT) forests are highly conductive and possess a large surface area, making them promising as electrode support materials for electrochemical applications including energy storage and water desalination. However, these forests often suffer from mechanical collapse when exposed to liquids, limiting their effectiveness in wet environments. In this study, we explore the use of vapor-phase oxidative molecular layer deposition (oMLD) to deposit thin, redox-active polymer films onto CNT forests to enhance their mechanical and electrochemical properties. We evaluate the mechanical behavior of the polymer-coated CNT forests using nanoindentation compression tests and solvent evaporation tests. The modulus and buckling stress of the forests increase with the thickness of the polymer coating, indicating enhanced mechanical strength conferred by the oMLD process. Furthermore, solvent evaporation tests demonstrate that the morphology of the polymer-coated CNT forests remains undisturbed by surface tension forces, in contrast to uncoated CNT forests which collapse and densify. This preservation of morphology underscores the effectiveness of the polymer coating in protecting the CNT forests from structural degradation in liquid environments. To gain deeper insights, finite element simulations analyze the mechanical properties of both coated and uncoated CNT forests. The simulations reveal that the increase in buckling load scales with the bending stiffness of individual CNTs and their coatings, highlighting the synergistic effect of the polymer coating on the overall forest structure. Finally, electrochemical characterization in aqueous electrolyte indicates an increase in charge capacity with polymer thickness for thin films, and a decrease in charge capacity at high film thicknesses arising from restricted pore volume. This work indicates that oMLD polymer coatings enhance the mechanical strength and electrochemical activity of CNT-based substrates. The findings from this study contribute to the development of more efficient and durable CNT-based electrodes for water desalination and energy storage applications.
(Invited) ALD/MLD Enabled Novel Functional Lanthanide-Organic Thin Films
Authors: Karppinen Maarit
Published: December 2024

The combined ALD/MLD (atomic/molecular layer deposition) technique involving both inorganic and organic precursors allows us to fabricate novel functional hybrid materials not readily accessible through any other fabrication route.
1
In this presentation, I will discuss the recent efforts of my research group and our collaborators to develop new lanthanide-organic thin-film materials towards (i) upconversion coatings relevant to solar cell applications,
2,3
(ii) warm-white-light emitting thin films relevant to next-generation lightning applications,
4
and (iii) visible-light excited photoluminescent Eu-organic coatings relevant to FRET (Förster resonance energy transfer) based bioimaging applications.
5,6

References

J. Multia & M. Karppinen, Atomic/molecular layer deposition for designer’s functional metal-organic materials, Advanced Materials Interfaces
9, 202200210 (2022).

Z. Giedraityte, M. Tuomisto, M. Lastusaari & M. Karppinen, Three- and two-photon NIR-to-vis (Yb,Er) upconversion from ALD/MLD fabricated molecular hybrid thin films, ACS Applied Materials & Interfaces
10, 8845 (2018).

A. Ghazy, M. Safdar, M. Lastusaari, A. Aho, A. Tukiainen, H. Savin, M. Guina & M. Karppinen, Luminescent (Er,Ho)2O3 thin films by ALD to enhance the performance of silicon solar cells, Solar Energy Materials & Solar Cells
219, 110787 (2021).

A. Ghazy, M. Lastusaari & M. Karppinen, White-light emitting multi-lanthanide terephthalate thin films by atomic/molecular layer deposition, Journal of Materials Chemistry C
11, 5331 (2023).

A. Ghazy, M. Lastusaari & M. Karppinen, Excitation wavelength engineering through organic linker choice in luminescent atomic/molecular layer deposited lanthanide-organic thin films, Chemistry of Materials
35, 5988 (2023).

A. Ghazy, J. Ylönen, N. Subramaniyam & M. Karppinen, Atomic/molecular layer deposition of europium-organic thin films on nanoplasmonic structures towards FRET-based applications, Nanoscale
15, 15865 (2023).
Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Kawabata Katsu , Ichinose Tatsu , Suzuki Koshi
Published: December 2024

A new analytical technique has been developed for determination of metallic impurities on and in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). Particles in air could not be introduced to the plasma of ICP-MS directly because the Ar plasma could not be sustained when air was introduced. The GED exchanged air with Ar efficiently (> 99.98%), the particles came out from GED in Ar gas stream that could be introduced to the plasma of ICP-MS. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. The technique was used for the following applications:

- Metallic contamination mapping of a wafer. Multiple spots (1 cm2/spot) of 300 mm wafer were laser ablated and analyzed by ICP-MS as shown in Fig.1. E6 - E7 atoms/cm2 of detection limit was obtained. The conventional VPD-ICP-MS technique uses a 1 mL scan solution to collect metallic impurities on an entire wafer surface of 300 mm wafer, and the collected solution is analyzed by ICP-MS giving E6 - E7 atoms/cm2 detection limit. It was impossible to get the contamination mapping information at such a low concentration. TRXRF has also been commonly used for the same purpose, but the detection limit is E10 - 12 atoms/cm2.

- Particle measurement on a wafer. A spike recovery test of 20 and 50 nm Au nano-particle standard on Si wafer was performed, and individual nano-particle signals were detected by ICP-MS. The number of Au particle recovery was more than 85%. 200 nm SiO2 particles on Si wafer were also detected after the optimization of laser parameters.

- Metallic contamination mapping on a wafer bevel. Several metallic contaminants were detected at certain spots of bevel, and E4 atoms of spot contamination could be detected.

- Depth profile analysis of an ion implanted wafer. The laser ablation was performed on the same area repeatedly and the profile of As ion implanted wafer could be carried out in atmospheric pressure. This technique was also used for analysis of multi-layer film wafers.

This paper explains how the new technique overcame the issues of the conventional LA-ICP-MS technique; why an entire wafer could not be analyzed and why an accurate quantitative analysis was impossible.

Figure 1
(Invited) Metrology Along the Gate-All-Around Logic Roadmap: From Nanosheet to Complementary Field-Effect Transistors
Authors: Bogdanowicz Janusz , Saib Mohamed , Beggiato Matteo , Lorusso Gian , Brissonneau Vincent , Dupuy Emmanuel , Loo Roger , Shimura Yosuke , Akula Anjani , Arimura Hiroaki , Puttarame Gowda Pallavi , Chan BT , Zhou Daisy , Mertens Hans , P. B. Lima Lucas , Horiguchi Naoto , Biesemans Serge , Hung Joey , Turovets Igor , Wei Sun , Hoenicke Philipp , Ciesielski Richard , Charley Anne-Laure , Leray Philippe
Published: December 2024

For over 50 years, improving the functionality per unit area has been the driving force of the semiconductor industry. Since the advent of fin field effect transistors (FETs), however, this has come at the expense of an increasingly complex device architecture. This is particularly true today as the industry is transitioning from finFETs to nanosheet (NSH) FETs. The integration of the latter devices indeed introduces the use e.g. of a modified substrate with an epitaxial SiGe/Si superlattice, of lateral etching and of size-constrained and buried gate stacks. Novel metrology concepts are therefore required to control all these new processing steps.

This presentation will start by reviewing the metrology challenges encountered along the different steps of the gate-all-around (GAA) logic roadmap, from NSH to Complementary FET (CFET) [1-3]. As will be shown, the sought information moves from the surface to increasingly deeper regions of the device. This is leading to the need for so-called 3D metrology techniques focusing on buried features [4]. We will then dive into the 3D metrology solution space and demonstrate the concrete use of some of these techniques for GAA logic metrology. We conclude that, although many capabilities remain to be demonstrated, the solution space is vast such that GAA logic metrology is not expected to suffer from a capability gap. However, we foresee a heavier resort to slower solutions, which is likely to lead to a throughput or capacity gap.

Luc van den Hove, The endless progression of Moore's law, Proceeding of SPIE Advanced Lithography + Patterning, PC1205301 (2022)

Liao, Complementary Field-Effect Transistor (CFET) Demonstration at 48nm Gate Pitch for Future Logic Technology
Scaling, IEDM 2023

M. Radosavljević et al., Demonstration of a Stacked CMOS Inverter at 60nm Gate Pitch with Power Via and Direct Backside Device Contacts, IEDM 2023

J. Bogdanowicz et al., Semiconductor metrology for the 3D era, Proc. SPIE 12496, Metrology, Inspection, and Process Control XXXVII, 1249617
(Invited) Engineering Sn-Based Group IV Quantum Materials
Authors: Assali Simone , Attiaoui Anis , Del Vecchio Patrick , Rotaru Nicolas , Moutanabbir Oussama
Published: December 2024

In recent years, direct band gap GeSn semiconductors have gained major attention for the monolithic integration of infrared emitters and detectors on a Si wafer.[1] A variety of GeSn infrared sensing and imaging technologies are now being developed using industrial-compatible fabrication processes. In addition to the high potential for integration in photonic technologies, GeSn quantum materials have been proposed for the design of novel solid-state qubits architectures.[2-3] Tensile-strained Ge/GeSn quantum wells (QWs) grown on a Si wafer result in a confined 2D hole gas with light-hole (LH) states lying above the heavy-hole (HH) ones. The LH-based nature of the Ge/GeSn QW is in striking difference with canonical Si/SiGe and Ge/SiGe QWs where electrons and HH are confined, respectively.[4] Achieving LH confinement paves the way to engineering ultrafast gate-defined spin qubits and integrate them into a spin-photon interface by leveraging the direct band gap absorption in the Ge/GeSn QW. Scalable all-group IV semiconductor quantum devices will thus be at reach by using the existing large-scale Si manufacturing processing.

In this presentation, we will discuss the epitaxial growth of Ge/Ge0.86Sn0.14 QWs using a CVD reactor, reaching sharp interfaces and in-plane biaxial tensile strain up to 1.65 %.[2] Coherent QW epitaxial growth with a Ge layer thickness in the 1.5-12 nm range will be discussed by combining cross-sectional transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. Atom probe tomography (APT) measurements will be shown to precisely probe the sharpness of the Ge/GeSn interfaces and to show the absence of impurities in the QW down to the atomic level. Spectroscopic ellipsometry (SE) measurements will be discussed to demonstrate LH confinement in the Ge/GeSn QW. The effect of strain and thickness of the QW on the excitonic optical transitions identified by SE will provide clear signature of LH confinement. The integration of Ge/GeSn QW in practical LH qubits devices will be further motivated through eight-band k·p simulations of the g factor anisotropy, dipole moment, and spin-orbit interaction as a function of the QW parameters and external magnetic fields.[3] Lastly, strategies to engineer both LH and HH spin qubits using Sn-based heterostructures will be discussed to enrich the available architectures for solid-state qubits on Si.

[1] O. Moutanabbir, et al. Appl. Phys. Lett. 118, 110502 (2021).

[2] S. Assali, et al., Adv. Mater. 34, 2201192 (2022).

[3] P. Del Vecchio, O. Moutanabbir, Phys. Rev. B 107, L161406 (2023).

[4] G. Scappucci, et al., Nature Reviews Mater. 6, 926-943 (2021).
(Invited) Electrically Pumped GeSn/SiGeSn Lasers
Authors: Buca Dan , Liu Teren , Seidel Lukas , Concepción Diaz Omar , Hartmann Jean-Michel , Tchelnokov Alexei , Capellini Giovanni , Oehme Michael , Grützmacher Detlev
Published: December 2024

Si-based photonic integrated circuits, where optical components are monolithically integrated on Si Integrated Circuits, are expected to dominate the future information and communication technology infrastructure. The Si photonic (SiPh) technology, consisting of both active- and passive components, is already widely used in a wealth of applications, ranging from datacom to detection systems. Recently, SiPh entered the technology platform for cryogenic applications in the emerging fields of integrated quantum technologies, optical computing, and artificial intelligence. Nonetheless, an efficient, electrically pumped light source that can be manufactured using solely group-IV semiconductors remains a major challenge. The novel GeSn and SiGeSn semiconductors obtained by the substitutional incorporation of Sn, a semi-metal, into the Ge lattice, offer a few advantages over other group-IV semiconductor alloys: by properly selecting the alloy composition and epitaxial strain, these materials are turned into fundamental direct bandgap semiconductors. This property normally missing in Group IV makes the (Si)GeSn system very attractive for efficient light sources. Using this material system, major milestones in group-IV lasing were reached in recent years like optically pumped bulk and Multi-Quantum Wells (MQW) lasers working up to room temperature.

Building on an extensive experimental activity on optically pumped GeSn heterostructures, here we will discuss electrically pumped lasing. The accent is put on two key features: CW operation and low threshold currents. Both of these milestones are simultaneously reached in SiGeSn/GeSn MQW micro disk cavity laser diodes. We will also discuss the material design in SiGeSn/GeSn heterostructures and a possibility of strain engineering to push the electrically pumped lasing to room temperatures.
(Invited) Group IV Mid-Infrared Optoelectronics Leveraging Nanoscale Growth Substrates
Authors: Moutanabbir Oussama , Luo Lu , Kim Youngmin , Assali Simone , Atalla Mahmoud , Joo Hyo-Jun , Koelling Sebastian , Chen Melvina , Shi Xuncheng , Burt Daniel , Nam Donguk
Published: December 2024

Mid-infrared (MIR) optoelectronic devices are of utmost importance to a plethora of applications such as night vision, thermal sensing, autonomous vehicles, free-space communication, and spectroscopy. To this end, leveraging the ubiquitous silicon-based processing has emerged as a powerful strategy that can be accomplished through the use of group IV germanium-tin (GeSn) alloys. Indeed, due to their compatibility with silicon and their tunable bandgap energy covering the entire MWIR range, GeSn semiconductors are frontrunner platforms for compact and scalable MIR technologies. However, the GeSn large lattice parameter has been a major hurdle limiting the quality of GeSn epitaxy on silicon wafers. These limitations are further exacerbated as Ge1−xSnx layers and heterostructures with Sn contents at least one order of magnitude higher than the solubility are needed for device structures relevant to MWIR applications. In this regime, the as-grown layers are typically under a significant compressive strain, which impacts the bandgap directness and increases its energy at the Γ point, thus hindering the device performance and limiting the covered range of the MIR spectrum. This compressive strain build-up not only affects the band structure but also limits the incorporation of Sn atoms in the growing layer, making the control of Sn content a daunting task.

In this presentation, we will show and discuss how sub-20 nm Ge nanowires provide effective compliant substrates to grow Ge1−xSnx alloys with a composition uniformity over several micrometers with a very limited build-up of the compressive strain. Ge/Ge1−xSnx structures with Sn content spanning the 6 to 18 at.% range are achieved. We will also demonstrate the integration of the obtained materials in optoelectronic device processing leading to tunable detectors and emitters [1,2]. For instance, photodetectors based on these materials were found to exhibit a high signal-to-noise ratio at room temperature and provide a tunable cutoff wavelength covering the 2.0 µm to 3.9 µm range. Additionally, the processed detectors were also integrated in uncooled imagers enabling the acquisition of high-quality images under both broadband and laser illuminations without the use of the lock-in amplifier technique. Finally, progress towards achieving nanoscale GeSn lasers will also be discussed [2].

References:

[1] L. Luo, M. R. M. Atalla, S. Assali, S. Koelling, G. Daligou, and O. Moutanabbir, Nano Letters (in press). https://doi.org/10.1021/acs.nanolett.4c00759

[2] Y. Kim, S. Assali, H.-J. Joo, S. Koelling, M. Chen, L. Luo, X. Shi, D. Burt, Z. Ikonic, D. Nam, and O. Moutanabbir, Nature Communications 14, 4393 (2023).
Room-Temperature Light Emission from Ion-Implanted Sige/Si and Ge/Si Quantum Dots on Si(001)
Authors: Spindlberger Lukas , Aberl Johannes , Murphy Armando Felipe , Fromherz Thomas , Brehm Moritz
Published: December 2024

Si Photonics is poised to bring vast benefits to data transfer and sensing applications. Many necessary components for Si photonics have already reached the level of commercialization. Most troublesome, however, is the development of a suitable light source that can be readily integrated with Si technology and that fulfills mandatory emission characteristics [1-3]. Silicon’s indirect band gap makes the implementation of useful light-emitting diodes and lasers on Si Photonic platforms challenging, as light emission is confined to cryogenic temperatures.

In this paper, we emphasize that combining group-IV-based nanostructures and point defects can lead to direct bandgap recombination paths in Ge/Si and SiGe/Si systems, leading to pronounced luminescence emission at room temperature and above [4]. The Ge/Si and SiGe/Si nanostructures (quantum dots) can be formed via strain-driven self-assembly, while the defects are intentionally created using low-energy ion implantation [4-7]. The latter allows defects to be confined within the quantum dots while the surrounding Si matrix remains crystalline.

Due to the band structure differences of Si and Ge, the effect of resulting defects that are of the split-interstitial type are vastly different for Ge and SiGe alloys. We performed first-principles calculations to show that in the case of Ge on Si, direct bandgap recombination is enabled at the Brillouin zone center, while for SiGe alloys, direct recombination is only possible in X-direction of the Brillouin zone [8-9]. In both cases, however, pronounced photoluminescence light emission from these defect-enhanced quantum dots at room temperature is observed [6,7] This is also true for electrically-driving these light emitters in p-i-n diodes [9,10] for which the luminescence emission is barely decaying up to a sample temperature of 100°C [10].

We note that the sample structure can be modified and improved post-growth using thermal annealing and passivation of parasitic defects using hydrogen [11,12].

References:

[1] D. Thomason et al., Journal of Optics 18, 073003 (2016).

[2] D. Liang, et al., Light, Advanced Manufacturing 2, 59 (2021).

[3] S. Wirths et al., Nature Photonics 9, 88 (2015).

[4] I. A. Fischer, et al., APL Photonics 7, 050901 (2022).

[5] M. Brehm, Silicon Photonics IV, 67-103, Silicon Photonics IV: Innovative Frontiers, edited by David J. Lockwood and Lorenzo Pavesi, Springer series Topics in Applied Physics (2021).

[6] M. Grydlik, et al., Nano Lett. 16, 6802–6807 (2016).

[7] M. Grydlik, et al., ACS Photonics 3, 298–303 (2016).

[8] F. Murphy-Armando, et al., Physical Review B 103 (8), 085310 (2021).

[9] M. Brehm, et al., to be published

[10] P. Rauter et al., ACS Photonics 5, 431-438 (2018).

[11] L. Spindlberger et al., Crystals 10, 351 (2020).

[12] L. Spindlberger et al., Appl. Phys. Lett. 118, 083104 (2021).
Epitaxy of Hexagonal Ge-2H : Lessons from in Situ TEM Observations
Authors: Vincent Laetitia , Verheijen Marcel A. , Peeters Wouter , Melhem Hassan , Van den Berg Theo , Ameziane Hafssa , Patriarche Gilles , Dursap Thomas , Travers Laurent , Renard Charles , Panciera Federico , Bakkers Erik P.A.M.
Published: December 2024

Silicon and Germanium crystallize in the cubic diamond structure 3C with which they dominate definitely the electronics. Playing on crystal phases in semiconductors occurs to be a valuable mean of electronic band engineering. Remarkably, the hexagonal 2H phase of SiGe turns to get a direct band gap with light emission capabilities within a specific composition range (Si<35%). This material holds the promise to fill the gap between electronics and photonics industry using group IV semiconductors.

We use GaAs NWs with the wurtzite structure as a template to create both (1) core/shell and (2) trunk/nanobranches heterostructures [2,3]. The GaAs-wurtzite is an ideal template to copy the structure by epitaxy forcing the Ge to adopt the hexagonal crystal phase and in turn it is used here as a textbook case

The growths are followed using the in situ TEM NANOMAX. This unique microscope can be implemented either with molecular beam epitaxy (MBE) sources or with a gas injector for chemical vapor deposition (CVD). Real time TEM observations at the atomic scale show the fundamental aspects of the epitaxy and the formation of growth-related staking faults in Ge-2H.

1) On core/shell configuration[1], depending on growth conditions, different growth regimes highly impact the crystal quality of the of Ge-2H shell. On {1-100} prismatic surfaces, a regular step flow supports a flat surface and a perfect replication of the hexagonal structure However, when the step flow is destabilized, original intrinsic I3 basal stacking faults (BSF) are formed during growth. We evidence their correlation with the growth modes related to surface diffusion. Understanding the nucleation of these defects is necessary to prevent their formation during epitaxy. Possible scenarios of I3 BSF formation are discussed. Theses defects show a faulted stacking ABACABAB with only one faulted basal plane bounded by a pair of partial dislocations along <11-20> with opposite Burger vectors b=+/-1/3<1-100>. Thermal annealing induces a motion of the dislocation and an expansion of the I3 BSF resulting in a 4H stacking in the core/shell structure.

2) On wurtzite GaAs nanowires, Au catalysts are deposited on the sidewalls. Nanobranches grow with an axial direction along <1-100> and exhibit a hexagonal crystal structure[2] . With in situ observations, we study the VLS and VSS growths of Au catalyzed Ge-2H branches depending on the growth temperature.

[1] L. Vincent et al. Adv. Mat. Inter. 9-16 (2022) 2102340, doi.org/10.1002/admi.202102340

[2] A Li et al. Nanotechnology 34 (2023) 015601 doi: 10.1088/1361-6528/ac9317

Figure 1
(Invited) Recent Progress on Heteroepitaxy of Si-Sn Alloy Thin Films
Authors: Kurosawa Masashi , Shibayama Shigehisa , Sakashita Mitsuo , Nakatsuka Osamu
Published: December 2024

The realization of silicon-tin (Si1−x
Sn
x
) alloys with various compositions has been expected to open up a higher degree of freedom for designs of the electron and phonon energy band structure in group-IV alloy systems [1-4]. Theoretically, it has been predicted that a Si1-xSnx becomes a direct transition semiconductor with a sufficient Sn content, although the Sn content was varied (25–90%) among reports. Additional interest is that the Sn incorporation in Si should dramatically decrease its thermal conductivity, leading to high thermoelectric performance. One serious problem with the Si1-xSnx synthesizing is Sn precipitation during the growth because of the extremely low solid solubility of Sn in Si (0.1%), a tenth of that in Ge. Thus, the growth conditions—especially growth temperature—need to be chosen carefully. In this talk, we will review the recent progress on the crystal growth techniques of Si1−x
Sn
x
thin films [5-11] and discuss the key point to prevent Sn precipitation during the growth.

References

[1] R. A. Soref and C. H. Perry, J. Appl. Phys. 69, 539 (1991).

[2] S. N. Khatami and Z. Aksamiji, Phys. Rev. Appl. 6, 014015 (2016).

[3] Y. Nagae et al., Jpn. J. Appl. Phys. 56, 04CR10 (2017).

[4] M. Tomita et al., Jpn. J. Appl. Phys. 57 04FB04 (2018).

[5] M. Kurosawa et al., Appl. Phys. Lett. 106, 171908 (2015).

[6] M. Kurosawa et al., Appl. Phys. Lett. 111, 192106 (2017).

[7] M. Kurosawa et al., Jpn. J. Appl. Phys. 58, SAAD02 (2019).

[8] R. Yokogawa et al., ECS Trans. 98, 291 (2020).

[9] K. Fujimoto et al., Appl. Phys. Express 16, 045501 (2023).

[10] T. Oiwa et al., Ext. Abst. 2022 SSDM, Makuhari, 2022, pp. 95-96.

[11] T. Oiwa et al., Ext. Abst. 2023 SSDM, Nagoya, 2023, pp. 535-536.
(Invited) High Mobility GeSn Nanowire CMOS
Authors: Junk Yannik , Concepción Díaz Omar , Frauenrath Marvin , Sun JIngxuan , Bae Jin Hee , Bärwolf Florian , Mai Andreas , Hartmann Jean-Michel , Grützmacher Detlev , Buca Dan , Zhao Qing-Tai
Published: December 2024

As transistor scaling advances, the necessity to replace silicon with materials possessing superior carrier mobilities intensifies. Group-IV semiconductors, with a particular emphasis on GeSn alloys, are distinguished by their exceptional electron and hole mobilities, rendering them prime candidates for advanced electronic applications. The vertical gate-all-around (GAA) nanowire transistor emerges as the pivotal device architecture, offering enhanced electrostatic control and a minimized physical footprint. This paper provides a comprehensive overview of vertical GAA GeSn nanowire CMOS devices. We construct vertical GAA nanowire transistors with epitaxial GeSn heterostructures, capitalizing on advancements in material growth, precise in-situ doping, and strategic band engineering across the source, channel, and drain regions. By harnessing GeSn's superior mobilities for both electrons and holes, we have developed and fabricated both p-FETs and n-FETs. The p-FET benefits from the high hole mobility of the Ge channel and the elevated injection velocity from the GeSn source, yielding significantly enhanced performance compared to devices solely made of Ge. For n-FETs, our findings reveal that incrementally increasing the Sn content in GeSn alloys leads to continuous performance enhancements, with an 11% Sn composition achieving a fivefold increase in on-current compared to traditional Ge-based devices. These outcomes underscore the immense potential of GeSn alloys in elevating the performance and energy efficiency of next-generation nanoelectronic devices.
Etch Characteristics of Indium Tin Oxide (ITO) Using Hydrocarbon-Based Gases in Inductively Coupled Plasma (ICP)
Authors: Park Yun Jae , Hong Jong Woo , Gil Hong Seong , Kim Dong Woo , Yeom Geun Young
Published: December 2024

The etching characteristics of indium tin oxide (ITO) using hydrocarbon based gas with Ar in inductively coupled plasma (ICP) etcher were investigated. This study specifically focuses on the comparison of methane (CH4), ethane (C2H6) and, propane (C3H8) gases in terms of their effect on the etch rate, etch selectivity, dimensional loss and surface roughness of the etched ITO. The experiments demonstrated that the use of hydrocarbon gases with higher carbon content such as C2H6 and C3H8 resulted in an improved etch rate and selectivity over photoresist (PR). This improvement is attributed to the lower hydrogen content in these gases, which reduces PR etching and thus minimizes PR damage. The increased carbon content in the gas mixture also contributed to more anisotropic etch profiles, lower dimensional loss and reduced surface roughness. Specifically, C3H8 achieved the highest etch rate among the investigated gases. This suggests that these hydrocarbon gases are particularly optimal for the precise patterning required in advanced semiconductor/display technologies . Additionally, the study addressed the challenge in removing etch by-products, composed of indium (In), tin (Sn), and carbon compounds, which are deposited on the chamber walls due to the low volatility. If not removed, the polymers can contaminate the chamber and degrade device performance. These residues were efficiently cleaned using H2/Ar plasmas. The cleaning mechanism involved the formation of more volatile compounds, such as InCxHy and SnHx, which could then be removed from the chamber surfaces.