bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
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).