jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Xingzhou Chen | Zheng Sun | Min Zhang | Ming Li | Zhigao Hu | Kenji Watanabe | Takashi Taniguchi | David W. Snoke | Zhe-Yu Shi | Jian Wu
Source: Applied Physics Letters (article, 2023-01-23)
Field: Materials Science — Materials Chemistry

Broadband enhancement of absorption by two-dimensional atomic crystals modeled as non-Hermitian photonic scattering We report the design and fabrication of a vertical structure using a distributed Bragg reflector and dielectric material layer to achieve optimized optical absorption enhancement for a stack of monolayer WS2 and MoS2, namely, a tenfold increase in absorption over a 100 nm spectral range. Our research indicates that we can approach over 50% absorption by finely tuning the thickness of the spacer layer. Our theoretical model shows that the dependence of the absorption coefficient on the spacer thickness can be understood as a solution of a non-Hermitian Schrödinger equation. These results advance the development of broadband optical devices, including solar energy conversion and sensitive optical sensors, by using two-dimensional excitonic materials. Absorption (acoustics) ; Materials science ; Attenuation coefficient ; Optoelectronics ; Optics ; Photonic crystal ; Photonics ; Dielectric ; Scattering ; Stack (abstract data type) ; Fabrication ; Atomic layer deposition ; Distributed Bragg reflector ; Broadband ; Radiative transfer ; Layer (electronics) ; Molecular physics ; Chemistry ; Physics ; Nanotechnology ; Wavelength 2D Materials and Applications ; Metamaterials and Metasurfaces Applications ; Plasmonic and Surface Plasmon Research
Authors: J. Proff | Matthias Mail | Adrian Lindner | A. Scheuer | M. Bendrich | E. Quinet | A. Schuler | Torsten Scherer | Christian Kübel | Martin Votsmeier
Source: Topics in Catalysis (article, 2023-04-21)
Field: Materials Science — Materials Chemistry

Towards FIB-SEM Based Simulation of Pore-Scale Diffusion in SCR Catalyst Layers Abstract The diffusivity in the upper Cu-Chabazite layer of a dual layer ammonia oxidation catalyst with a lower Pt layer was investigated. In a first step, the pore structure of the upper Cu-Chabazite catalyst layer was determined by Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) slice&amp;view tomography. From the FIB-SEM data the 3D pore structure of the catalyst was reconstructed and diffusion simulations were performed on the reconstructed pore geometry, resulting in an estimated effective diffusivity of D eff / D gas = 0.31. To validate the FIB-SEM derived estimates of the diffusivity, measurements of CO oxidation on the dual layer catalyst were performed, where the CO was oxidized in the lower Pt-layer while the upper SCR layer served as an inactive diffusion barrier. In this way, the effective diffusivity can be determined from the measured CO conversion. An effective diffusion coefficient of D eff / D gas = 0.11 was obtained from the CO oxidation measurements, three times lower than the value obtained from the FIB-SEM data, but in line with previous literature data for the effective diffusivity in monolith washcoat layers. Additional NH 3 oxidation experiments were performed on the dual layer catalyst. The results were well reproduced by a reactor model applying the effective diffusion coefficient obtained by the CO oxidation experiments. The origin of this apparent inconsistency is currently not understood and requires further investigation. Thermal diffusivity ; Chabazite ; Scanning electron microscope ; Monolith ; Catalysis ; Diffusion ; Materials science ; Focused ion beam ; Analytical Chemistry (journal) ; Chemical engineering ; Layer (electronics) ; Catalytic oxidation ; Knudsen diffusion ; Chemistry ; Ion ; Composite material ; Zeolite ; Chromatography ; Porosity ; Thermodynamics ; Organic chemistry Catalytic Processes in Materials Science ; Nanoporous metals and alloys ; Electrocatalysts for Energy Conversion
Authors: Akkattu T. Biju | Sayan Shee | Sowmya Shree Ranganathappa | Mahesh S. Gadhave | Romin Gogoi
Source: ChemRxiv (preprint, 2023-08-11)
Field: Chemistry — Organic Chemistry

Enantioselective Synthesis of C-O Axially Chiral Diaryl Ethers via NHC-Catalyzed Atroposelective Desymmetrization Axially chiral diaryl ethers, a distinguished class of atropisomers possessing unique dual C-O axis, hold immense potential for diverse research domains. In contrast to the catalytic enantioselective synthesis of conventional single axis bearing atropisomers, the atroposelective synthesis of axially chiral ethers containing flexible C-O axis remains a significant challenge. Herein, we demonstrate the first N-heterocyclic carbene (NHC)-catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde-containing diaryl ethers. Mechanistically, the reaction proceeds via NHC-catalyzed desymmetrization strategy to afford the corresponding axially chiral diaryl ether atropisomers in good yields and high enantioselectivities under mild conditions. The derivatization of the synthesized product expands the utility of present strategy via access to a library of C-O axially chiral compounds. The temperature dependency and preliminary investigations on the racemization barrier of C-O bonds are also presented. Atropisomer ; Desymmetrization ; Enantioselective synthesis ; Chemistry ; Axial chirality ; Racemization ; Catalysis ; Kinetic resolution ; Carbene ; Axial symmetry ; Combinatorial chemistry ; Organic chemistry ; Stereochemistry Axial and Atropisomeric Chirality Synthesis ; Molecular spectroscopy and chirality
Authors: Minjae Jeong | S.W. Lee | S.W. Wi | K.C. Lee | Y.S. Lee
Source: Heliyon (article, 2023-09-01)
Field: Materials Science — Materials Chemistry

Valence state switching and reversible emission tunability of A2SiO4 (A = Ba, Sr, and Ca) with two-site substitution of Eu ions through simple thermal treatment We investigated the changes in the structural and luminescent properties of Eu-ion-doped A<sub>2</sub>SiO<sub>4</sub> (A<sub>2</sub>SiO<sub>4</sub>:Eu, A = Ba, Sr, and Ca) by annealing in oxidizing and reducing atmospheres. The initially synthesized samples displayed distinct, intense red emissions at approximately 600 and 700 nm, which can be attributed to the presence of Eu<sup>3+</sup> ions. The emission intensity of Eu<sup>3+</sup> was the strongest in Ca<sub>2</sub>SiO<sub>4</sub>:Eu, which exhibited the lowest lattice symmetry among the three samples. Remarkably, following annealing in a reducing atmosphere (H<sub>2</sub>), the previously observed red emission vanished, and instead, a strong green emission at around 500 nm, which is characteristic of Eu<sup>2+</sup> ions. Because of the two occupation sites of the Eu ions in A<sub>2</sub>SiO<sub>4</sub>, the emission of Eu<sup>2+</sup> strongly depends on the excitation wavelength, which is the most evident in Ca<sub>2</sub>SiO<sub>4</sub>:Eu. Conversely, after annealing in an oxidizing atmosphere (O<sub>2</sub>), the emission in the green region was suppressed and the emission in the red region returned. The reversible transition between two oxidation states occurred repeatedly by alternating H<sub>2</sub> and O<sub>2</sub> annealing, resulting in good color tunability in wide visible region with a simple ambient annealing process in a single compound. Annealing (glass) ; Ion ; Oxidizing agent ; Materials science ; Reducing atmosphere ; Doping ; Valence (chemistry) ; Luminescence ; Analytical Chemistry (journal) ; Emission spectrum ; Emission intensity ; Excitation ; Wavelength ; Photoluminescence ; Photochemistry ; Spectral line ; Chemistry ; Optoelectronics ; Metallurgy Luminescence Properties of Advanced Materials ; Glass properties and applications ; Nuclear materials and radiation effects
Authors: Ahmad Daher | Asmae Bousfiha | Iogann Tolbatov | Clève Dionel Mboyi | Hélène Cattey | Thierry Roisnel | Paul Fleurat‐Lessard | Muriel Hissler | Jean‐Cyrille Hierso | Pierre‐Antoine Bouit | Julien Roger
Source: Angewandte Chemie (article, 2023-01-30)
Field: Chemistry — Organic Chemistry

Tetrazo[1,2‐<i>b</i>]indazoles: Straightforward Access to Nitrogen‐Rich Polyaromatics from<i>s</i>‐Tetrazines Abstract The straightforward access to a new class of aza‐polyaromatics is reported. Starting from readily available fluorinated s‐tetrazine, a cyclization process with azide leads to the formation of an unprecedented tetrazo[1,2‐ b ]indazole or a bis‐tetrazo[1,2‐ b ]indazole ( cis and trans conformers). Based on the new nitrogen core, further N‐directed palladium‐catalyzed ortho ‐C−H bond functionalization allows the introduction of halides or acetates. The physicochemical properties of these compounds were studied by a joint experimental/theoretical approach. The tetrazo[1,2‐ b ]indazoles display solid‐state π‐stacking, low reduction potential, absorption in the visible range up to the near‐infrared, and intense fluorescence, depending on the molecular structure. Chemistry ; Indazole ; Tetrazine ; Palladium ; Stacking ; Halide ; Photochemistry ; Azide ; Fluorescence ; Combinatorial chemistry ; Catalysis ; Stereochemistry ; Organic chemistry Synthesis of Tetrazole Derivatives ; Click Chemistry and Applications ; Synthesis and Characterization of Heterocyclic Compounds
Authors: Hashir M. Gauri | Zachary M. Sherman | Ahmed Al Harraq | Thomas M. Truskett | Bhuvnesh Bharti
Source: Soft Matter (article, 2023-01-01)
Field: Materials Science — Materials Chemistry

Magnetic field enabled <i>in situ</i> control over the structure and dynamics of colloids interacting <i>via</i> SALR potentials Colloidal suspensions are an ideal model for studying crystallization, nucleation, and glass transition mechanisms, due to the precise control of interparticle interactions by changing the shape, charge, or volume fraction of particles. However, these tuning parameters offer insufficient active control over interparticle interactions and reconfigurability of assembled structures. Dynamic control over the interparticle interactions can be obtained through the application of external magnetic fields that are contactless and chemically inert. In this work, we demonstrate the dual nature of magnetic nanoparticle dispersions to program interactions between suspended nonmagnetic microspheres using an external magnetic field. The nanoparticle dispersion simultaneously behaves as a continuous magnetic medium at the microscale and a discrete medium composed of individual particles at the nanoscale. This enables control over a depletion attractive potential and the introduction of a magnetic repulsive potential, allowing a reversible transition of colloidal structures within a rich phase diagram by applying an external magnetic field. Active control over competing interactions allows us to create a model system encompassing a range of states, from large fractal clusters to low-density Wigner glass states. Monitoring the dynamics of colloidal particles reveals dynamic heterogeneity and a marked slowdown associated with approaching the Wigner glass state. In situ ; Dynamics (music) ; Colloid ; Field (mathematics) ; Chemical physics ; Nanotechnology ; Physics ; Materials science ; Chemistry ; Physical chemistry ; Mathematics Material Dynamics and Properties ; Magnetic and Electromagnetic Effects ; Electrostatics and Colloid Interactions
Authors: Jesse Fletcher | Giacinta Parish | J.M. Dell | Adrian Keating
Source: Small (article, 2023-04-17)
Field: Materials Science — Materials Chemistry

Morphological and Optical Transformation of Gas Assisted Direct Laser Written Porous Silicon Films Direct laser writing (DLW) of mesoporous porous silicon (PS) films is shown to selectively create spatially separated nitridized and carbonized features on a single film. Nitridized or carbonized features are formed during DLW at 405 nm in an ambient of nitrogen and propane gas, respectively. The range of laser fluence required to create varying feature sizes while avoiding damage to the PS film is identified. At high enough fluence, nitridation using DLW has been shown as an effective method for laterally isolating regions on the PS films. The efficacy in preventing oxidation once passivated is investigated via energy dispersive X-ray spectroscopy. Changes in composition and optical properties of the DL written films are investigated using spectroscopic analysis. Results show carbonized DLW regions have a much higher absorption than as-fabricated PS, attributed to pyrolytic carbon or transpolyacetylene deposits in the pores. Nitridized regions exhibit optical loss similar to previously published thermally nitridized PS films. This work presents methods to engineer PS films for a variety of potential device applications, including the application of carbonized PS to selectively engineer thermal conductivity and electrical resistivity and of nitridized PS to micromachining and selective modification of refractive index for optical applications. Materials science ; Fluence ; Porous silicon ; Carbonization ; Silicon ; Pyrolytic carbon ; Laser ; Optoelectronics ; Absorption (acoustics) ; Chemical engineering ; Nanotechnology ; Composite material ; Scanning electron microscope ; Optics ; Pyrolysis Diamond and Carbon-based Materials Research ; Silicon Nanostructures and Photoluminescence ; Semiconductor materials and devices
Authors: Aleksandar Demić | A. Valavanis | Paul Dean | Lianhe Li | A. G. Davies | E. H. Linfield | J. E. Cunningham | James Bailey | А. В. Акимов | A. J. Kent | P. Harrison
Source: Physical review. B./Physical review. B (article, 2023-06-14)
Field: Chemistry — Spectroscopy

Acoustic band engineering in terahertz quantum-cascade lasers and arbitrary superlattices We present theoretical methods for the analysis of acoustic phonon modes in superlattice structures, and terahertz-frequency quantum-cascade lasers (THz QCLs). Our generalized numerical solution of the acoustic-wave equation provides good agreement with experimental pump-probe measurements of the acoustic resonances in a THz QCL. We predict that the detailed layer structure in THz QCLs imprints up to $\ensuremath{\sim}2\phantom{\rule{0.16em}{0ex}}\mathrm{GHz}$ detuning of the acoustic mode spacing, which cannot be seen in analytical models. This effect is strongest in devices with large and abrupt acoustic mismatch between layers. We use an acoustic deformation potential within a density-matrix approach to analyze electron transport induced in a range of the most common THz QCL active-region design schemes. We conclude that acoustic modes up to $\ensuremath{\sim}200\phantom{\rule{0.16em}{0ex}}\mathrm{GHz}$ are capable of significantly perturbing QCL transport, highlighting their potential for ultrafast modulation of laser emission. Terahertz radiation ; Superlattice ; Cascade ; Laser ; Physics ; Phonon ; Acoustic wave ; Optics ; Optoelectronics ; Condensed matter physics Spectroscopy and Laser Applications ; Terahertz technology and applications ; Meteorological Phenomena and Simulations
Authors: M. Balaji | Axel Strömberg | Vladimir L. Tassev | Shivashankar Vangala | Myriam Bailly | Arnaud Grisard | Bruno Gérard | S. Lourdudoss | Yan‐Ting Sun
Source: Crystals (article, 2023-01-18)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Investigation of OP-GaP Grown on OP-GaAs Templates Using Nondestructive Reciprocal Space Mapping Orientation-patterned gallium phosphide (OP-GaP) has been grown heteroepitaxially on OP gallium arsenide (GaAs) templates using hydride vapor phase epitaxy (HVPE). The effect of OP-GaAs template fabrication methods of epitaxial-inversion and wafer bonding on the heteroepitaxial OP-GaP growth has been investigated. OP-GaP layers with a growth rate of up to 35 µm/h and excellent domain fidelity were obtained. The growth rate and the domain fidelity have been revealed/studied by scanning electron microscope (SEM). In addition, we demonstrate that the crystalline quality of the individual domains, namely, the substrate-oriented domains (ODs) and the inverted domains (IDs), can be investigated by high-resolution x-ray diffraction reciprocal space mapping (HRXRDRSM), which can also indicate the domain fidelity. Attempts to increase the growth rate and improve the domain fidelity by increasing the III and V group precursors resulted in either an increase in the growth rate in the OP-GaP layers grown on epitaxial inversion OP-GaAs template at the expense of the domain crystalline quality and fidelity or an improvement in the crystalline quality of the domains at the expense of the growth rate in the OP-GaP layers grown on wafer-bonded OP-GaAs templates. In the case of OP-GaP grown on OP-GaAs templates prepared by epitaxial inversion, the crystalline quality of the ODs is better than that of the IDs, but it shows that the quality of the inverted layer in the template influences the quality and fidelity of the grown domains. To the authors’ knowledge, exploitation of HRXRDRSM studies on OP-GaP to establish the crystalline quality of its individual domains (ODs and IDs) is the first of its kind. OP-ZnSe grown on OP-GaAs templates has also been included in this study to further emphasize the potential of this method. We propose from this study that once the growth rate is optimized from SEM studies, HRXRDRSM analysis alone can be used to assess the structural quality and to infer the domain fidelity of the OP structures. Epitaxy ; Materials science ; Wafer ; Template ; Cathodoluminescence ; Reciprocal lattice ; Optoelectronics ; Crystallography ; Nanotechnology ; Diffraction ; Layer (electronics) ; Optics ; Chemistry ; Physics Ga2O3 and related materials ; Semiconductor Quantum Structures and Devices ; GaN-based semiconductor devices and materials
Authors: Gábor Vári | Csaba Vass | Gyula Halasi | László Szabó | Krisztián Palotás | Péter Dombi | András Berkó | László Óvári | Zoltán Kónya
Source: Applied Surface Science (article, 2023-03-20)
Field: Materials Science — Materials Chemistry

New insights into thermal processes of metal deposits on h-BN/Rh(1 1 1): A comparison of Au and Rh In this paper the thermal properties of Au and Rh deposits are compared on hexagonal boron nitride (h-BN) “nanomesh” prepared on Rh(1 1 1), applying STM, XPS, low energy ion scattering (LEIS), LEED, and DFT. At room temperature, both metals essentially follow Volmer-Weber (3D) growth. Upon subsequent annealing, agglomeration (sintering), intercalation, and desorption are competing surface processes for both metals. For the more reactive Rh, we suggest an additional encapsulation mechanism: between 600 K and 750 K, fragments of decomposed h-BN diffuse locally from the bottom onto the metal clusters covering them partially. STM data indicates that agglomeration of gold nanoparticles proceeds faster compared to rhodium. At higher temperatures (∼1050 K–1100 K), all non-desorbing gold atoms diffuse below h-BN, even for large initial coverages. On the other hand, for larger Rh deposits (≥5 ML), the outermost layer always contains Rh. Accumulation of gold at the interface between h-BN and Rh(1 1 1) significantly enhances the thermal stability of h-BN, attributed to the lower reactivity of Au in the decomposition of h-BN compared to Rh(1 1 1). At elevated substrate temperatures, intercalation of individual adatoms takes place during deposition, which requires higher temperatures for rhodium due to its slower diffusion and higher probability of nucleation. Rhodium ; Nucleation ; Nanomesh ; Chemistry ; Annealing (glass) ; X-ray photoelectron spectroscopy ; Metal ; Thermal decomposition ; Intercalation (chemistry) ; Surface diffusion ; Transition metal ; Analytical Chemistry (journal) ; Materials science ; Crystallography ; Adsorption ; Chemical engineering ; Physical chemistry ; Inorganic chemistry ; Nanotechnology ; Metallurgy ; Catalysis ; Graphene Graphene research and applications ; Semiconductor materials and devices ; Thermal properties of materials
Authors: Hugo Witt | Srijani Mallik | Luis M. Vicente‐Arche | Gerbold C. Ménard | Guilhem Saïz | D. Stornaiuolo | Maria D’Antuono | Isabella Boventer | N. Bergeal | Manuel Bibès
Source: Advanced Physics Research (article, 2023-04-25)
Field: Materials Science — Materials Chemistry

Patterning of Superconducting Two‐Dimensional Electron Gases based on AlO<sub><i>x</i></sub>/KTaO<sub>3</sub> (111) Interfaces Abstract The versatility of properties displayed by two‐dimensional electron gases (2DEGs) at oxide interfaces has fostered intense research in hope of achieving exotic electromagnetic effects in confined systems. Of particular interest is the recently discovered superconducting state appearing in (111)‐oriented KTaO 3 interfaces, with a critical temperature T c ≈2 K, almost 10 times higher than that of SrTiO 3 ‐based 2DEGs. Just as in SrTiO 3 ‐based 2DEGs, fabricating devices in this new system is a technical challenge due to the fragility of the 2DEG and the propensity of bulk KTaO 3 to become conducting outside the devices upon adventitious oxygen vacancy doping. Here, three different techniques are presented for patterning Hall bars in AlO x /KTaO 3 (111) heterostructures. The devices show superconducting transitions ranging from 1.3 to 1.78 K, with limited degradation from the unpatterned thin film, and enable an efficient tuning of the carrier density by electric field effect. The array of techniques allows for the definition of channels with a large range of dimensions for the design of various kinds of devices to explore the properties of this system down to the nanoscale. Heterojunction ; Condensed matter physics ; Superconductivity ; Materials science ; Electron ; Doping ; Oxide ; Fermi gas ; Nanotechnology ; Optoelectronics ; Engineering physics ; Physics Electronic and Structural Properties of Oxides ; Magnetic and transport properties of perovskites and related materials ; Semiconductor materials and devices
Authors: Zahra Golsanamlou | Alessandro Fortunelli | Luca Sementa
Source: Advanced Functional Materials (article, 2023-12-13)
Field: Materials Science — Materials Chemistry

First‐Principles Design of Ohmic FET Devices from 2D Transition Metal Dichalcogenides Abstract A chlorine‐doped ultrathin phase of hafnium disulfide (HfS 2 ) is proposed as an ideal candidate material for 2D field‐effect transistor (FET) device applications, down to the extreme sub‐5 nm miniaturization limit. This transition metal dichalcogenide 2D material is designed to combine features of both a metal and a semiconductor, exhibiting a high electric conductivity comparable with ordinary metals, that can be abruptly cut down via gating due to an energy gap immediately below the Fermi level and its anomalous metallic properties. These unique features enable realizing an alternative design of a FET device in which electrode and channel are made of the same Cl‐doped ML HfS 2 phase, a potential breakthrough bypassing all issues associated with electronic (Schottky) and structural dis‐homogeneities or low conductivity that have hindered progress in this field. This material/design combination shall lead to a FET device with purely ohmic behavior, high metallic conductance, no interfacial contact resistance, and facile gating with extremely high on/off ratio. Materials science ; Ohmic contact ; Field-effect transistor ; Transistor ; Optoelectronics ; Doping ; Schottky diode ; Semiconductor ; Contact resistance ; Conductivity ; Miniaturization ; Nanotechnology ; Diode ; Electrical engineering ; Voltage 2D Materials and Applications ; MXene and MAX Phase Materials ; Ferroelectric and Negative Capacitance Devices