Prof. Dr. Maksym Yarema
Prof. Dr. Maksym Yarema
Assistant Professor at the Department of Information Technology and Electrical Engineering
Additional information
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Spring Semester 2025
Number | Unit |
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227-0669-00L | Chemistry of Devices and Technologies |
- Impact of Cation Distribution on Photoluminescence of Ag-In-Se/ZnSe Core/Shell NanocrystalsAnnina Moser, Olesya Yarema, Noemi Rusch, Nikola Dordevic, Weyde Lin, Deniz Bozyigit, Nuri Yazdani, Maksym Yarema, Mathieu Luisier and Vanessa WoodACS Nanoscience Au, American Chemical Society, 2024.
Ag–In–Se/ZnSe core/shell nanocrystals exhibit good photoluminescence quantum yield (PLQY), yet intriguingly, the maximum PLQY is first reached after several days of storage. We hypothesize that this may be due to cationic rearrangement in the nanocrystal post-synthesis. To test this hypothesis, we computationally generated ternary Ag–In–Se and quaternary Ag–In–Zn–Se nanocrystals with varying degrees of cationic disorder, as quantified by the distribution of the metal cation valence electrons in the tetrahedra around Se anions. We then used density functional theory-parametrized tight-binding simulations to study the electronic structure and optical properties of these systems as a function of the homogeneity of the valence electron distribution in a tetrahedron. We found that homogeneous distribution of cations leads to a larger band gap and optical coupling, and that, in the presence of Ag_In or In_Ag antisite defects, the introduction of intermediate valence Zn cations decreases the variance in valence electrons and improves the optical properties. We further simulated the impact of a Zn-gradient shell and rearrangement of cations in the outer layers of the nanocrystals and find that diffusion of Zn into the nanocrystal and cationic rearrangement can explain the post-synthetic increase of PLQY. This work highlights the importance of developing syntheses for multinary nanocrystals that result not only in size and composition uniformity but also in nanocrystals with a uniform distribution of charge.
- 3D Confinement Stabilizes the Metastable Amorphous State of Antimony Nanoparticles - A New Material for Miniaturized Phase Change Memories?Anne Frommelius, Konstantin Wirth, Thorsten Ohlerth, Dario Siebenkotten, Simon Wintersteller, Ahed Abouserie, Hongchu Du, Joachim Mayer, Maksym Yarema, Thomas Taubner and Ulrich SimonSmall, vol. 20: no. 44, pp. 2402257, Wiley-VCH, 2024.
The wet-chemical synthesis of 3D confined antimony nanoparticles (Sb-NP) at low and high temperatures is described. Using reaction conditions that are mild in temperature and strong in reducing power allows the synthesis of amorphous Sb-NP stabilized with organic ligands. Exchanging the organic ligand 1-octanethiol by iodide enabled to investigate the unusual strong stability of this metastable material through simultaneous thermal analysis combining differential scanning calorimetry and thermogravimetric analysis. Additionally, in situ high temperature powder x-ray diffraction (p-XRD) shows a significant increase in stabilization of the amorphous phase in comparison to thin layered, 1D confined Sb or bulk material. Further, it is shown with scattering-type scanning near-field optical microscopy (s-SNOM) experiments that the optical response of the different phases in Sb-NP make the distinctness of each phase possible. It is proposed that the Sb-NP introduced here can serve as a 3D-confined optically addressable nanomaterial of miniaturized phase change memory devices.
- Structural Ordering in Ultrasmall Multicomponent Chalcogenides: The Case of Quaternary Cu-Zn-In-Se NanocrystalsMaksym Yarema, Nuri Yazdani, Olesya Yarema, Nikola Dordevic, Weyde M.M. Lin, Deniz Bozyigit, Sebastian Volk, Annina Moser, Alexandra Turrini, Petr A. Khomyakov, Maarten Nachtegaal, Mathieu Luisier and Vanessa WoodAdvanced Materials, vol. 36: no. 44, pp. 2406351, Wiley-VCH, 2024.
The compositional tunability of non-isovalent multicomponent chalcogenide thin films and the extent of atomic ordering of their crystal structure is key to the performance of many modern technologies. In contrast, the effects of ordering are rarely studied for quantum-confined materials, such as colloidal nanocrystals. In this paper, the possibilities around composition tunability and atomic ordering are explored in ultrasmall ternary and quaternary quantum dots, taking I-III-VI-group Cu-Zn-In-Se semiconductor as a case study. A quantitative synthesis for 3.3 nm quaternary chalcogenide nanocrystals is developed and shown that cation and cationic vacancy ordering can be achieved in these systems consisting of only 100s of atoms. Combining experiment and theoretical calculations, the relationship between structural ordering and optical properties of the materials are demonstrated. It is found that the arrangement and ordering of cationic sublattice plays an important role in the luminescent efficiency. Specifically, the concentration of Cu-vacancy couples in the nanocrystal correlates with luminescence quantum yield, while structure ordering increases the occurrence of such optically active Cu-vacancy units. On the flip side, the detrimental impact of cationic site disorder in I-III-VI nanocrystals can be mitigated by introducing a cation of intermediate valence, such as Zn (II).
- Inkjet-Printed Phase Change Memory DevicesHanglin He, Dhananjeya Kumaar, Kevin Portner, Till Zellweger, Florian M. Schenk, Simon Wintersteller, Vitor Vlnieska, Alexandros Emboras, Vanessa Wood and Maksym YaremaAdvanced Electronic Materials, vol. 10: no. 11, pp. 2400203, Wiley-VCH, 2024.
Phase change memory (PCM) is among the most promising candidates for the next generation of storage-class and main memory systems in the computing era beyond Moore's law. However, the widespread installment of PCM devices is limited by the high price-per-bit and complex fabrication process. In this paper, it is shown that functional PCM memory devices can be printed, proving low-cost avenues for non-silicon memory technologies. Taking Ge-Sb-Te (GST) as a case study, PCM inks are prepared and optimize their structural, rheological, and printing parameters. GST layers are then printed onto PCM devices in the planar configuration, showing excellent performance, such as non-volatility, resistivity contrast, low cycle-to-cycle variability, and endurance of at least 100 cycles. This paper provides a novel approach to liquid-based engineered PCM devices through inkjet printing, enabling patterned memory layers, lower price-per-bit, and customizable multi-material PCM arrays.
- Palladium Zinc Nanocrystals: Nanoscale Amalgamation Enables Multifunctional Intermetallic ColloidsOlesya Yarema, Annina Moser, Chun-Wei Chang, Jasper Clarysse, Florian M. Schenk, Eda Egüz, Hanut Vemulapalli, Neeru Mittal, Eldho Edison, Yi-Hsuan Wu, Denis A. Kuznetsov, Christoph R. Müller, Markus Niederberger, Christian Franck, Vanessa Wood and Maksym YaremaAdvanced Functional Materials, vol. 34: no. 31, pp. 2309018, Weinheim: Wiley-VCH, 2023.
Intermetallic nanocrystals are emerging materials for energy, catalysis, and biomedical applications, but combining two or more metals at the nanoscale remains challenging. The amalgamation reaction represents a convenient method for hundreds of intermetallic compositions, as it relies on fast and efficient alloying of liquid metals into presynthesized metallic seeds. Here, Pd-Zn nanocrystals, prepared via Zn amide thermolysis on the surface of Pd nanocrystals and subsequent amalgamation alloying, are investigated. Size-uniform nanocrystals and control over a wide range of Pd-Zn compositions are achieved. This allows deriving a phase diagram at the nanoscale, in which miscibility gaps and three phases with broad solid solutions are detected. Furthermore, the formation of homogeneous ZnO shells for Pd-Zn compositions extending beyond phase solubility limits is observed. Full chemistry control for Pd-Zn nanocrystals enables a rational choice of materials for selected energy applications, achieveing an extended lifetime of Zn-ion batteries for Zn-rich PdZn2 stoichiometry, superior electrocatalytic properties for nearly stoichiometric PdZn halite phase, and the stability and efficiency of high-voltage cathodes benefiting from ZnO shell protection around Pd3Zn10 nanocrystals are reported. This paper exemplifies the multifunctionality of intermetallics Pd-Zn nanocrystals, while this methodology can be extended to many other bimetallic nanomaterials.
- Phase-Controlled Synthesis and Phase-Change Properties of Colloidal Cu-Ge-Te NanoparticlesDhananjeya Kumaar, Matthias Can, Helena Weigand, Olesya Yarema, Simon Wintersteller, Rachel Grange, Vanessa Wood and Maksym YaremaChemistry of Materials, vol. 36: no. 13, pp. 6598-6607, American Chemical Society, 2024.
Phase-change memory (PCM) technology has recently attracted a vivid interest for neuromorphic applications, in-memory computing, and photonic integration due to the tunable refractive index and electrical conductivity between the amorphous and crystalline material states. Despite this, it is increasingly challenging to scale down the device dimensions of conventionally sputtered PCM memory arrays, restricting the implementation of PCM technology in mass applications such as consumer electronics. Here, we report the synthesis and structural study of sub-10 nm Cu-Ge-Te (CGT) nanoparticles as suitable candidates for low-cost and ultrasmall PCM devices. We show that our synthesis approach can accurately control the structure of the CGT colloids, such as composition-tuned CGT amorphous nanoparticles as well as crystalline CGT nanoparticles with trigonal alpha-GeTe and tetragonal Cu2GeTe3 phases. In situ characterization techniques such as high-temperature X-ray diffraction and X-ray absorption spectroscopy reveal that Cu doping in GeTe improves the thermal properties and amorphous phase stability of the nanoparticles, in addition to nanoscale effects, which enhance the nonvolatility characteristics of CGT nanoparticles even further. Moreover, we demonstrate the thin-film fabrication of CGT nanoparticles and characterize their optical properties with spectroscopic ellipsometry measurements. We reveal that CGT nanoparticle thin films exhibit a negative reflectivity change and have good reflectivity contrast in the near-IR spectrum. Our work promotes the possibility to use PCM in nanoparticle form for applications such as electro-optical switching devices, metalenses, reflectivity displays, and phase-change IR devices.
- Electrochemical Activation of Fe-LiF Conversion Cathodes in Thin-Film Solid-State BatteriesJoel Casella, Jȩdrzej Morzy, Evgeniia Gilshtein, Maksym Yarema, Moritz H. Futscher and Yaroslav RomanyukACS Nano, vol. 18: no. 5, pp. 4352-4359, American Chemical Society, 2024.
Transition metal fluoride (TMF) conversion-type cathodes promise up to 4 times higher gravimetric energy densities compared to those of common intercalation-type cathodes. However, TMF cathodes demonstrate sluggish kinetics, poor efficiencies, and incompatibility with many liquid electrolytes. In this work, coevaporated heterostructured iron and lithium fluoride (Fe-LiF) cathodes are investigated in thin-film solid-state batteries with a LiPON electrolyte and a lithium metal anode. The cells were cycled 2000 times at a cycling rate of 6C. They show a gradual improvement in voltaic efficiency (37–53%) and specific capacity (146–216 mAh/g) during cycling. After 2000 cycles, the cathode capacity reaches 480 mAh/g at a cycling rate of C/3.6, close to its theoretical capacity of 498 mAh/g, at room temperature conditions. This capacity gain is correlated with an observed electrochemically activated nanorestructuring of the cathode, characterized by cycling-induced coarsening (from 2.8 to 4.2 nm) of the metallic iron phase and its accumulation near the current collector interface, as well as lithium fluoride phase accumulation near the LiPON interface.
- Phase-Change Memory from Molecular TelluridesFlorian M. Schenk, Till Zellweger, Dhananjeya Kumaar, Darijan Bošković, Simon Wintersteller, Pavlo Solokha, Serena De Negri, Alexandros Emboras, Vanessa Wood and Maksym YaremaACS Nano, vol. 18: no. 1, pp. 1063-1072, American Chemical Society, 2023.
Phase-change memory (PCM) is an emerging memory technology based on the resistance contrast between the crystalline and amorphous states of a material. Further development and realization of PCM as a mainstream memory technology rely on innovative materials and inexpensive fabrication methods. Here, we propose a generalizable and scalable solution-processing approach to synthesize phase-change telluride inks in order to meet demands for high-throughput material screening, increased energy efficiency, and advanced device architectures. Bulk tellurides, such as Sb₂Te₃, GeTe, Sc₂Te₃, and TiTe₂, are dissolved and purified to obtain inks of molecular metal telluride complexes. This allowed us to unlock a wide range of solution-processed ternary tellurides by the simple mixing of binary inks. We demonstrate accurate and quantitative composition control, including prototype materials (Ge–Sb–Te) and emerging rare-earth-metal telluride-doped materials (Sc–Sb–Te). Spin-coating and annealing convert ink formulations into high-quality, phase-pure telluride films with preferred orientation along the (00l) direction. Deposition engineering of liquid tellurides enables thickness-tunable films, infilling of nanoscale vias, and film preparation on flexible substrates. Finally, we demonstrate cyclable and non-volatile prototype memory devices, achieving performance indicators such as resistance contrast and low reset energy on par with state-of-the-art sputtered PCM layers.
- Coupling to octahedral tilts in halide perovskite nanocrystals induces phonon-mediated attractive interactions between excitonsNuri Yazdani, Maryna I. Bodnarchuk, Federica Bertolotti, Norberto Masciocchi, Ina Fureraj, Burak Guzelturk, Benjamin L. Cotts, Marc Zajac, Gabriele Rainò, Maximilian Jansen, Simon C. Boehme, Maksym Yarema, Ming-Fu Lin, Michael Kozina, Alexander Reid, Xiaozhe Shen, Stephen Weathersby, Xijie Wang, Eric Vauthey, Antonietta Guagliardi, Maksym V. Kovalenko, Vanessa Wood and Aaron M. LindenbergNature Physics, vol. 20: no. 1, pp. 47-53, Nature, 2023.
Understanding the origin of electron-phonon coupling in lead halide perovskites is key to interpreting and leveraging their optical and electronic properties. Here we show that photoexcitation drives a reduction of the lead-halide-lead bond angles, a result of deformation potential coupling to low-energy optical phonons. We accomplish this by performing femtosecond-resolved, optical-pump-electron-diffraction-probe measurements to quantify the lattice reorganization occurring as a result of photoexcitation in nanocrystals of FAPbBr₃. Our results indicate a stronger coupling in FAPbBr₃ than CsPbBr₃. We attribute the enhanced coupling in FAPbBr₃ to its disordered crystal structure, which persists down to cryogenic temperatures. We find the reorganizations induced by each exciton in a multi-excitonic state constructively interfere, giving rise to a coupling strength that scales quadratically with the exciton number. This superlinear scaling induces phonon-mediated attractive interactions between excitations in lead halide perovskites.
- HiFi-DRAM: Enabling High-fidelity DRAM Research by Uncovering Sense Amplifiers with IC ImagingMichele Marazzi, Tristan Sachsenweger, Flavien Solt, Peng Zeng, Kubo Takashi, Maksym Yarema and Kaveh Razavi51st IEEE/ACM International Symposium on Computer Architecture (ISCA 2024), Buenos Aires, Argentina, pp.133-149, Piscataway, NJ: IEEE, June 29 - July 3, 2024.
DRAM vendors do not disclose the architecture of the sense amplifiers deployed in their chips. Unfortunately, this hinders academic research that focuses on studying or improving DRAM. Without knowing the circuit topology, transistor dimensions, and layout of the sense amplifiers, researchers are forced to rely on best guesses, impairing the fidelity of their studies. We aim to fill this gap between academia and industry for the first time by performing Scanning Electron Microscopy (SEM) with Focused Ion Beam (FIB) on recent commodity DDR4 and DDR5 DRAM chips from the three major vendors. This required us to adequately prepare the samples, identify the sensing area, and align images from the different FIB slices. Using the acquired images, we reverse engineer the circuits, measure transistor dimensions and extract physical layouts of sense amplifiers — all previously unavailable to researchers. Our findings show that the commonly assumed classical sense amplifier topology has been replaced with the more sophisticated offset-cancellation design by two of the three major DRAM vendors. Furthermore, the transistor dimensions of sense amplifiers and their revealed physical layouts are significantly different than what is assumed in existing literature. Given commodity DRAM, our analysis shows that the public DRAM models are up to 9x inaccurate, and existing research has up to 175x error when estimating the impact of the proposed changes. To enable high-fidelity DRAM research in the future, we open source our data, including the reverse engineered circuits and layouts.
- Unravelling the amorphous structure and crystallization mechanism of GeTe phase change memory materialsSimon Wintersteller, Olesya Yarema, Dhananjeya Kumaar, Florian M. Schenk, Olga V. Safonova, Paula Macarena Abdala, Vanessa Wood and Maksym YaremaNature Communications, vol. 15: no. 1, pp. 1011, Nature, 2024.
The reversible phase transitions in phase-change memory devices can switch on the order of nanoseconds, suggesting a close structural resemblance between the amorphous and crystalline phases. Despite this, the link between crystalline and amorphous tellurides is not fully understood nor quantified. Here we use in-situ high-temperature x-ray absorption spectroscopy (XAS) and theoretical calculations to quantify the amorphous structure of bulk and nanoscale GeTe. Based on XAS experiments, we develop a theoretical model of the amorphous GeTe structure, consisting of a disordered fcc-type Te sublattice and randomly arranged chains of Ge atoms in a tetrahedral coordination. Strikingly, our intuitive and scalable model provides an accurate description of the structural dynamics in phase-change memory materials, observed experimentally. Specifically, we present a detailed crystallization mechanism through the formation of an intermediate, partially stable ‘ideal glass’ state and demonstrate differences between bulk and nanoscale GeTe leading to size-dependent crystallization temperature.
- Synthesis and Electronic Structure of Mid-Infrared Absorbing Cu₃SbSe₄ and CuₓSbSe₄ NanocrystalsAnnina Moser, Olesya Yarema, Gregorio Garcia, Mathieu Luisier, Filippo Longo, Emanuel Billeter, Andreas Borgschulte, Maksym Yarema and Vanessa WoodChemistry of Materials, vol. 35: no. 16, pp. 6323-6331, Washington, DC: American Chemical Society, 2023.
Aliovalent I–V–VI semiconductor nanocrystals are promising candidates for thermoelectric and optoelectronic applications. Famatinite Cu₃SbSe₄ stands out due to its high absorption coefficient and narrow band gap in the mid-infrared spectral range. This paper combines experiment and theory to investigate the synthesis and electronic structure of colloidal CuₓSbSe₄ nanocrystals. We achieve predictive composition control of size-uniform CuₓSbSe₄(x = 1.9–3.4) nanocrystals. Density functional theory (DFT)-parametrized tight-binding simulations on nanocrystals show that the more the Cu-vacancies, the wider the band gap of CuₓSbSe₄ nanocrystals, a trend which we also confirm experimentally via FTIR spectroscopy. We show that Sb꜀ᵤ antisite defects can create mid-gap states, which may give rise to sub-bandgap absorption. This work provides a detailed study of CuₓSbSe₄ nanocrystals and highlights the potential opportunities as well as challenges for their application in infrared devices.
- Colloidal Ternary Telluride Quantum Dots for Tunable Phase Change Optics in the Visible and Near-InfraredDhananjeya Kumaar, Matthias Can, Kevin Portner, Helena Weigand, Olesya Yarema, Simon Wintersteller, Florian Schenk, Darijan Boskovic, Nathan Pharizat, Robin Meinert, Evgeniia Gilshtein, Yaroslav Romanyuk, Artemios Karvounis, Rachel Grange, Alexandros Emboras, Vanessa Wood and Maksym YaremaACS Nano, vol. 17: no. 7, pp. 6985-6997, Washington, DC: American Chemical Society, 2023.
A structural change between amorphous and crystalline phase provides a basis for reliable and modular photonic and electronic devices, such as nonvolatile memory, beam steerers, solid-state reflective displays, or mid-IR antennas. In this paper, we leverage the benefits of liquid-based synthesis to access phase-change memory tellurides in the form of colloidally stable quantum dots. We report a library of ternary MxGe1-xTe colloids (where M is Sn, Bi, Pb, In, Co, Ag) and then showcase the phase, composition, and size tunability for Sn-Ge-Te quantum dots. Full chemical control of Sn-Ge-Te quantum dots permits a systematic study of structural and optical properties of this phase-change nanomaterial. Specifically, we report composition dependent crystallization temperature for Sn-Ge-Te quantum dots, which is notably higher compared to bulk thin films. This gives the synergistic benefit of tailoring dopant and material dimension to combine the superior aging properties and ultrafast crystallization kinetics of bulk Sn-Ge-Te, while improving memory data retention due to nanoscale size effects. Furthermore, we discover a large reflectivity contrast between amorphous and crystalline Sn-Ge-Te thin films, exceeding 0.7 in the near-IR spectrum region. We utilize these excellent phase-change optical properties of Sn-Ge-Te quantum dots along with liquid based processability for nonvolatile multicolor images and electro-optical phase-change devices. Our colloidal approach for phase-change applications offers higher customizability of materials, simpler fabrication, and further miniaturization to the sub-10 nm phase-change devices.
- Highly Responsive Mid-Infrared Metamaterial Enhanced Heterostructure Photodetector Formed out of Sintered PbSe/PbS Colloidal Quantum DotsRaphael Schwanninger, Stefan M. Koepfli, Olesya Yarema, Alexander Dorodnyy, Maksym Yarema, Annina Moser, Shadi Nashashibi, Yuriy Fedoryshyn, Vanessa Wood and Juerg LeutholdACS Applied Materials & Interfaces, vol. 15: no. 8, pp. 10847-10857, Washington, DC: American Chemical Society, 2023.
Efficient and simple-to-fabricate light detectors in the mid infrared (MIR) spectral range are of great importance for various applications in existing and emerging technologies. Here, we demonstrate compact and efficient photodetectors operating at room temperature in a wavelength range of 2710–4250 nm with responsivities as high as 375 and 4 A/W. Key to the high performance is the combination of a sintered colloidal quantum dot (CQD) lead selenide (PbSe) and lead sulfide (PbS) heterojunction photoconductor with a metallic metasurface perfect absorber. The combination of this photoconductor stack with the metallic metasurface perfect absorber provides an overall ∼20-fold increase of the responsivity compared against reference sintered PbSe photoconductors. More precisely, the introduction of a PbSe/PbS heterojunction increases the responsivity by a factor of ∼2 and the metallic metasurface enhances the responsivity by an order of magnitude. The metasurface not only enhances the light–matter interaction but also acts as an electrode to the detector. Furthermore, fabrication of our devices relies on simple and inexpensive methods. This is in contrast to most of the currently available (state-of-the-art) MIR photodetectors that rely on rather expensive as well as nontrivial fabrication technologies that often require cooling for efficient operation.
- Solvent-free synthesis of photoluminescent carbon nanoparticles from lignin-derived monomers as feedstockMárcia G.A. da Cruz, Joy N. Onwumere, Jianhong Chen, Björn Beele, Maksym Yarema, Serhiy Budnyk, Adam Slabon and Bruno V.M. RodriguesGreen Chemistry Letters and Reviews, vol. 16: no. 1, pp. 2196031, London: Taylor & Francis, 2023.
Photoluminescent carbon nanoparticles (CNPs), such as carbon dots (CDs), have attracted much attention owing to a unique set of properties, like high and tunable fluorescence. In this way, the use of carbon-rich lignin has been demonstrated to be a sustainable approach to producing a broad range of photoluminescent CNPs. However, the valorization of this complex polyphenol is limited when it comes to green and efficient ways of conversion. In addition, the existing solvothermal approaches using lignin often result in CDs with low photoluminescence, while flammable and/or toxic solvents are employed. Here, we depolymerized technical lignins, i.e. kraft and soda, through electroreductive cleavage in two different sustainable media: deep eutectic solvent and levulinic acid. After depolymerization, lignin-derived monomers were generated, with a predominance of aryl ether and phenolic groups, which were further combined with 1,2-Phenylenediamine to produce N-doped CNPs in a solvent-free approach. Photoluminescent CNPs with varied sizes were generated (5-50 nm), which presented a wide photoluminescence emission, from blue to red, depending on solvent polarity. These results demonstrate a feasible and sustainable route for the solvent-free synthesis of photoluminescent CNPs using lignin-derived monomers as carbon source, which may find applications in a wide range of fields.
- Crystal habit analysis of LiFePO4 microparticles by AFM and first-principles calculationsKevin-P. Gradwohl, Peter Benedek, Maxim Popov, Aleksandar Matkovic, Jürgen Spitaler, Maksym Yarema, Vanessa Wood and Christian TeichertCrystEngComm, vol. 24: no. 39, pp. 6891-6901, London: Royal Society of Chemistry, 2022.
LiFePO4 (LFP) microparticles with a faceted crystal habit have been fabricated by hydrothermal synthesis. Three different surfactants were employed to control the crystal habits of the particles, which ranged from cubes over different diamond-shaped platelets to pyramids. Crystallographic models of the particles with the lowest matching Miller indices were determined based on the data acquired by atomic force microscopy (AFM) and gave insight into the synthesis process. The analysis of the crystal facets of the observed particles implied the importance of the (2 1 0) facet, which was previously neglected. First-principles investigations based on density functional theory revealed a surface energy for (2 1 0) of 0.83 J m(-2), contributing 2.5% of the surface area of the equilibrium shape of LFP crystals.
- Ligand Tuning of Localized Surface Plasmon Resonances in Antimony-Doped Tin Oxide NanocrystalsOlexiy Balitskii, Oleksandr Mashkov, Anastasiia Barabash, Viktor Rehm, Hany A. Afify, Ning Li, Maria S. Hammer, Christoph J. Brabec, Andreas Eigen, Marcus Halik, Olesya Yarema, Maksym Yarema, Vanessa Wood, David Stifter and Wolfgang HeissNanomaterials, vol. 12: no. 19, pp. 3469, Basel: MDPI, 2022.
Aliovalent-doped metal oxide nanocrystals exhibiting localized surface plasmons (LSPRs) are applied in systems that require reflection/scattering/absorption in infrared and optical transparency in visible. Indium tin oxide (ITO) is currently leading the field, but indium resources are known to be very restricted. Antimony-doped tin oxide (ATO) is a cheap candidate to substitute the ITO, but it exhibits less advantageous electronic properties and limited control of the LSPRs. To date, LSPR tuning in ATO NCs has been achieved electrochemically and by aliovalent doping, with a significant decrease in doping efficiency with an increasing doping level. Here, we synthesize plasmonic ATO nanocrystals (NCs) via a solvothermal route and demonstrate ligand exchange to tune the LSPR energies. Attachment of ligands acting as Lewis acids and bases results in LSPR peak shifts with a doping efficiency overcoming those by aliovalent doping. Thus, this strategy is of potential interest for plasmon implementations, which are of potential interest for infrared upconversion, smart glazing, heat absorbers, or thermal barriers.
- Status and challenges of multi-junction solar cell technologyAdil Baiju and Maksym YaremaFrontiers in Energy Research, vol. 10, pp. 971918, Lausanne: Frontiers Media, 2022.
The ongoing energy transition to curb carbon dioxide emissions and meet the increasing energy demands have enhanced the need for integration of renewable energy into the existing electricity system. Solar energy has been gaining an increasing market share over the past decade. Multi-junction solar cells (MJSCs) enable the efficient conversion of sunlight to energy without being bound by the 33% limit as in the commercialized single junction silicon solar cells. III-V semiconductors have been used effectively in space applications and concentrated photovoltaics (CPV) over the past few decades. This review discusses the working and components of MJSCs at cell level as well as module level for space applications and CPV. The fabrication procedure, material acquirement of MJSCs is analyzed before introducing the current challenges preventing MJSCs from achieving widespread commercialization and the research direction in the future where these challenges can be addressed.
- Engineering of Oxide Protected Gold NanoparticlesJean-Marc Von Mentlen, Jasper Clarysse, Annina Moser, Dhananjeya Kumaar, Olesya Yarema, Takumi Sannomiya, Maksym Yarema and Vanessa WoodThe Journal of Physical Chemistry Letters, vol. 13: no. 25, pp. 5824-5830, Washington, DC: American Chemical Society, 2022.
Gold nanoparticles that are partially or fully covered by metal oxide shells provide superior functionality and stability for catalytic and plasmonic applications. Yet, facile methods for controlled fabrication of thin oxide layers on metal nanoparticles are lacking. Here, we report an easy method to reliably engineer thin Ga2O3 shells on Au nanoparticles, based on liquid-phase chemical oxidation of Au–Ga alloy nanoparticles. We demonstrate that, with this technique, laminar and ultrathin Ga2O3 shells can be grown with ranging thickness from sub- to several monolayers. We show how the localized surface plasmon resonance can be used to understand the reaction process and quantitatively monitor the Ga2O3 shell growth. Finally, we demonstrate that the Ga2O3 coating prevents sintering of the Au nanoparticles, providing thermal stability to at least 250 °C. This approach, building on dealloying of bimetallic nanoparticles by the solution-phase oxidation, promises a general technique for achieving controlled metal/oxide core/shell nanoparticles.
- In Situ Formation of Lithium Polyacrylate Binder for Aqueous Manufacturing and Recycling of Ni-Rich CathodesRamesh Shunmugasundaram, Rajalakshmi Senthil Arumugam, Peter Benedek, Maksym Yarema, Paul Baade and Vanessa WoodJournal of the Electrochemical Society, vol. 169: no. 6, pp. 060504, Bristol: IOP Publishing, 2022.
Water has now become the standard process solvent for graphite-based anodes, eliminating the use of toxic and costly N-Methyl-pyrrolidone (NMP) in anode manufacturing. Ideally, water could also become the standard for cathodes; however, water-based processing of NMC cathode materials induces lithium leaching, which reduces their specific capacity and leads to capacity fade. Here, we demonstrate that leached lithium ions can be exploited during aqueous slurry preparation to create a Li-containing polymer binder that enables cathode performance comparable to those fabricated using NMP. Specifically, we show that leached lithium ions from LiNi0.8Mn0.1Co0.1O2 (NMC 811) particles react with polyacrylic acid (PAA) to form a lithium polyacrylate (LPA) surface coating and binder. Because the resulting LPA binder is water soluble, aqueous-based recycling of the cathode particles is feasible and over 90% capacity retention is shown in recycled material after 100 cycles.