RSS 1.0Physical Science and Engineering (PSE) Division
For more information visit: http://pse.kaust.edu.sa/
Recent Submissions
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Suppressed phase segregation for triple-junction perovskite solar cells(Nature, Springer Science and Business Media LLC, 2023-03-28) [Article]The tunable band gaps and facile fabrication of perovskites make them attractive for multi-junction photovoltaics1,2. However, light-induced phase segregation limits their efficiency and stability3-5: this occurs in wide band gap (> 1.65 eV) I/Br mixed perovskite absorbers, and becomes even more acute in the top cells of triple-junction solar photovoltaics that requires a fully 2.0 eV band gap absorber2,6. We report herein that lattice distortion in I/Br mixed perovskites is correlated with the suppression of phase segregation, generating an increased ion migration energy barrier arising from the decreased average interatomic distance between A-site cation and iodide. Using a ~2.0 eV Rb/Cs mixed-cation inorganic perovskite with large lattice distortion in the top subcell, we fabricated all-perovskite triple-junction solar cells and achieved an efficiency of 24.3% (23.3% certified quasi-steady-state efficiency) with an open-circuit voltage of 3.21 V. This is, to our knowledge, the first reported certified efficiency for perovskite-based triple-junction solar cells. The triple-junction devices retain 80% of their initial efficiency following 420 hours of operation at the maximum power point.
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Nitrogen-Based Magneto-Ionic Manipulation of Exchange Bias in CoFe/MnN Heterostructures(Accepted by ACS Nano, 2023-03-27) [Article]Electric field control of the exchange bias effect across ferromagnet/antiferromagnet (FM/AF) interfaces has offered exciting potentials for low-energy-dissipation spintronics. In particular, the solid state magneto-ionic means is highly appealing as it may allow reconfigurable electronics by transforming the all-important FM/AF interfaces through ionic migration. In this work, we demonstrate an approach that combines the chemically induced magneto-ionic effect with the electric field driving of nitrogen in the Ta/Co0.7Fe0.3/MnN/Ta structure to electrically manipulate exchange bias. Upon field-cooling the heterostructure, ionic diffusion of nitrogen from MnN into the Ta layers occurs. A significant exchange bias of 618 Oe at 300 K and 1484 Oe at 10 K is observed, which can be further enhanced after a voltage conditioning by 5% and 19%, respectively. This enhancement can be reversed by voltage conditioning with an opposite polarity. Nitrogen migration within the MnN layer and into the Ta capping layer cause the enhancement in exchange bias, which is observed in polarized neutron reflectometry studies. These results demonstrate an effective nitrogen-ion based magneto-ionic manipulation of exchange bias in solidstate devices.
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Atomically Dispersed NiNx Site with High Oxygen Electrocatalysis Performance Facilely Produced via a Surface Immobilization Strategy(ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2023-03-27) [Article]Nonprecious-metal heterogeneous catalysts with atomically dispersed active sites demonstrated high activity and selectivity in different reactions, and the rational design and large-scale preparation of such catalysts are of great interest but remain a huge challenge. Current approaches usually involve extremely high-temperature and tedious procedures. Here, we demonstrated a straightforward and scalable preparation strategy. In two simple steps, the atomically dispersed Ni electrocatalyst can be synthesized in a tens grams scale with quantitative yield under mild conditions, and the active Ni sites were produced by immobilizing preorganized NiNx complex on the substrate surface via organic thermal reactions. This catalyst exhibits excellent catalysis performances in both oxygen evolution and reduction reactions. It also exhibited tunable catalysis activity, high catalysis reproducibility, and high stability. The atomically dispersed NiNx sites are tolerant at high Ni concentration, as the random reactions and metal nanoparticle formation that generally occurred at high temperatures were avoided. This strategy illustrated a practical and green method for the industrial manufacture of nonprecious-metal single-site catalysts with a predictable structure.
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On-chip Diamond MEMS Magnetic Sensing through Multifunctionalized Magnetostrictive Thin Film(Advanced Functional Materials, Wiley, 2023-03-27) [Article]Electrically integrable, high-sensitivity, and high-reliability magnetic sensors are not yet realized at high temperatures (500 °C). In this study, an integrated on-chip single-crystal diamond (SCD) micro-electromechanical system (MEMS) magnetic transducer is demonstrated by coupling SCD with a large magnetostrictive FeGa film. The FeGa film is multifunctionalized to actuate the resonator, self-sense the external magnetic field, and electrically readout the resonance signal. The on-chip SCD MEMS transducer shows a high sensitivity of 3.2 Hz mT−1 from room temperature to 500 °C and a low noise level of 9.45 nT Hz−1/2 up to 300 °C. The minimum fluctuation of the resonance frequency is 1.9 × 10−6 at room temperature and 2.3 × 10−6 at 300 °C. An SCD MEMS resonator array with parallel electric readout is subsequently achieved, thus providing a basis for the development of magnetic image sensors. The present study facilitates the development of highly integrated on-chip MEMS resonator transducers with high performance and high thermal stability.
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NMR Chemical Shifts of Emerging Green Solvents, Acids, and Bases for Facile Trace Impurity Analysis(ACS Sustainable Chemistry & Engineering, American Chemical Society (ACS), 2023-03-27) [Article]The straightforward identification of impurity signals in nuclear magnetic resonance (NMR) spectra is imperative for the structure elucidation and signal assignment of synthetic products and intermediates. To keep pace with the emergence of novel green solvents and auxiliary compounds (e.g., acids and bases), NMR impurity tables and databases must be regularly updated. This study reports the residual 1H and 13C NMR chemical shifts of 42 green solvents, acids, and bases in eight NMR solvents, namely, dimethylsulfoxide-d6, chloroform-d, D2O, CD3OD, CD3CN, acetone-d6, tetrahydrofuran-d8, and toluene-d8. The multiplicities and coupling constants of 1H signals are also determined herein. The analysis of the recorded NMR spectra provides important information regarding the reactivity or multicomponent nature of the green solvents, acids, and bases. Herein, the results of this study are combined with earlier reports on residual NMR impurities to form a comprehensive database. This database forms the basis of an online interface (http://www.nmrimpurities.com) through which users can browse solvent spectra and search for signals of unknown origins to easily identify residual impurities in NMR spectra.
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Hybrid 2D/CMOS microchips for memristive applications(Nature, Springer Science and Business Media LLC, 2023-03-27) [Article]Exploiting the excellent electronic properties of two-dimensional (2D) materials to fabricate advanced electronic circuits is a major goal for the semiconductors industry1-2. However, most studies in this field have been limited to the fabrication and characterization of isolated large (>1µm2) devices on unfunctional SiO2/Si substrates. Some studies integrated monolayer graphene on silicon microchips as large-area (>500µm2) interconnection3 and as channel of large transistors (~16.5µm2)4-5, but in all cases the integration density was low, no computation was demonstrated, and manipulating monolayer 2D materials was challenging because native pinholes and cracks during transfer increase variability and reduce yield. Here we present the fabrication of high-integration-density 2D/CMOS hybrid microchips for memristive applications — CMOS stands for complementary metal oxide semiconductor. We transfer a sheet of multilayer hexagonal boron nitride (h-BN) onto the back-end-of-line (BEOL) interconnections of silicon microchips containing CMOS transistors of the 180nm node, and finalize the circuits by patterning the top electrodes and interconnections. The CMOS transistors provide outstanding control over the currents across the h-BN memristors, which allows us to achieve endurances of ~5 million cycles in memristors as small as ~0.053µm2. We demonstrate in-memory computation by constructing logic gates, and measure spike-timing dependent plasticity (STDP) signals that are suitable for the implementation of spiking neural networks (SNN). The high performance and the relatively-high technology readiness level achieved represent a significant advance towards the integration of 2D materials in microelectronic products and memristive applications.
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Seismic evidence for a 1000 km mantle discontinuity under the Pacific.(Nature communications, Springer Science and Business Media LLC, 2023-03-27) [Article]Seismic discontinuities in the mantle are indicators of its thermo-chemical state and offer clues to its dynamics. Ray-based seismic methods, though limited by the approximations made, have mapped mantle transition zone discontinuities in detail, but have yet to offer definitive conclusions on the presence and nature of mid-mantle discontinuities. Here, we show how to use a wave-equation-based imaging method, reverse-time migration of precursors to surface-reflected seismic body waves, to uncover both mantle transition zone and mid-mantle discontinuities, and interpret their physical nature. We observe a thinned mantle transition zone southeast of Hawaii, and a reduction in impedance contrast around 410 km depth in the same area, suggesting a hotter-than-average mantle in the region. Here, we furthermore reveal a 4000-5000 km-wide reflector in new images of the mid mantle below the central Pacific, at 950-1050 km depth. This deep discontinuity exhibits strong topography and generates reflections with polarity opposite to those originating at the 660 km discontinuity, implying an impedance reversal near 1000 km. We link this mid-mantle discontinuity to the upper reaches of deflected mantle plumes upwelling in the region. Reverse-time migration full-waveform imaging is a powerful approach to imaging Earth's interior, capable of broadening our understanding of its structure and dynamics and shrinking modeling uncertainties.
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Thickness-tunable magnetic and electronic transport properties of the quasi-two-dimensional van der Waals ferromagnet Co0.27TaS2 with disordered intercalation(Accepted by Physical Review B, American Physical Society, 2023-03-27) [Article]The intercalation of magnetic elements in non-magnetic van der Waals (vdW) materials is an effective way to design novel (quasi) 2D magnets and produce exotic properties. More specifically, how exactly the intercalator is distributed within the synthetic crystal can also affect the physical properties substantially. In contrast to conventional 3d transition-metal intercalates of niobium and tantalum dichalcogenides, which commonly have 2 × 2- or Ö3 × Ö3- type ordered intercalation, we report a disordered intercalation of Co atoms between the vdW gaps of 2H-tantalum disulfide (2H-TaS2). The obtained quasi-vdW ferromagnet Co0.27TaS2 shows both perpendicular magnetic anisotropy and thickness-tunable magnetic properties. More interestingly, the temperature dependence of electrical resistivity shows a semiconductor-like behavior, in contrast to the metallic feature of other analogs in this material family. This unexpected phenomenon can be understood through a variable-range hopping mechanism, which is due to highly disordered intercalation. Moreover, Co0.27TaS2 shows a side-jump scattering dominated anomalous Hall effect, which can also be related to the disordered distribution of Co intercalators.
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Hydrocracking Mechanisms of Oxygenated Plastics and Vacuum Gasoil Blends(Elsevier BV, 2023-03-27) [Preprint]We explore the holistic composition of products obtained from hydrocracking oxygen-containing waste plastics, such as polymethylmethacrylate or polyethylene terephthalate, blended with vacuum gasoil (VGO). Reactions are performed in a semi-batch reactor at 400 ºC or 420 °C using a platinum-palladium supported on a faujasite zeolite catalyst. The gas, liquid, and solid product compositions are resolved using bidimensional chromatography (GC×GC), nuclear magnetic resonance (NMR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Then, the data are fused to resolve the composition and gain insights into the reaction mechanisms. The results reveal a synergistic transformation of heavy species from the VGO and the polymers, with a remarkable fuel selectivity (> 60%). The molecular-level description of the samples can be used to analyze and propose the reaction mechanisms of these complex blends.
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A Stable Neural Network-Based Eikonal Tomography using Hard-Constrained Measurements(Authorea, Inc., 2023-03-26) [Preprint]Eikonal tomography, or travel time inversion, has been one of the primary seismological tools for decades and has been used to understand Earth’s properties and dynamic processes. At the heart of the inversion process is the need for an accurate, and preferably flexible, eikonal solver to compute the travel time field. Most of the conventional eikonal solvers, however, suffer from first-order convergence errors and difficulties in dealing with irregular computational grids. Physics-informed neural networks (PINNs) have been introduced to tackle these problems and have shown great success in addressing those challenges. Nevertheless, these approaches still suffer from slow convergence and unstable training dynamics due to the multi-term nature of the loss function. To improve on this, we propose a new formulation for the isotropic eikonal equation, which imposes boundary conditions as hard constraints. We employ the theory of functional connections to the eikonal tomography problem, which allows for the utilization of a single loss term for training the PINN model. Through rigorous numerical tests, its efficiency, stability, and flexibility in tackling a variety of cases, including topography-dependent and 3D models, are attested, thus providing an efficient and stable PINN-based eikonal tomography.
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A wide range experimental and kinetic modeling study of the oxidation of 2,3-dimethyl-2-butene: Part 1(Combustion and Flame, Elsevier BV, 2023-03-26) [Article]2,3-Dimethyl-2-butene (TME) is a potential fuel additive with high research octane number (RON) and octane sensitivity (S), which can improve internal combustion engine performance and efficiency. However, the combustion characteristics of TME have not been comprehensively investigated. Thus, it is essential to study the combustion characteristics of TME and construct a detailed chemical kinetic model to describe its combustion. In this paper, two high-pressure shock tubes and a constant-volume reactor are used to measure ignition delay times and laminar flame speeds of TME oxidation. The ignition delay times were measured at equivalence ratios of 0.5, 1.0, and 2.0 in “air”, at pressures of 5 and 10 bar, in the temperature range of 950 – 1500 K. Flame speeds of the TME/ “air” mixtures were measured at atmospheric pressure, at a temperature of 325 K, for equivalence ratios ranging from 0.78 to 1.31. Two detailed kinetic mechanisms were constructed independently using different methodologies; the KAUST TME mechanism was constructed based on NUIGMech1.1, and the MIT TME mechanism was built using the Reaction Mechanism Generator (RMG). Both mechanisms were used to simulate the experimental results using Chemkin Pro. In the present work, reaction flux and sensitivity analyses were performed using the KAUST mechanism to determine the critical reactions controlling TME oxidation at the conditions studied.
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Flexible Oxide Thin Film Transistors, Memristors, and Their Integration(Advanced Functional Materials, Wiley, 2023-03-26) [Article]Flexible electronics have seen extensive research over the past years due to their potential stretchability and adaptability to non-flat surfaces. They are key to realizing low-power sensors and circuits for wearable electronics and Internet of Things (IoT) applications. Semiconducting metal-oxides are a prime candidate for implementing flexible electronics as their conformal deposition methods lend themselves to the idiosyncrasies of non-rigid substrates. They are also a major component for the development of resistive memories (memristors) and as such their monolithic integration with thin film electronics has the potential to lead to novel all-metal-oxide devices combining memory and computing on a single node. This review focuses on exploring the recent advances across all these fronts starting from types of suitable substrates and their mechanical properties, different types of fabrication methods for thin film transistors and memristors applicable to flexible substrates (vacuum- or solution-based), applications and comparison with rigid substrates while additionally delving into matters associated with their monolithic integration.
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Bioengineering of air-filled protein nanoparticles by genetic and chemical functionalization.(Journal of nanobiotechnology, Springer Science and Business Media LLC, 2023-03-25) [Article]Background: Various bacteria and archaea, including halophilic archaeon Halobacterium sp. NRC-1 produce gas vesicle nanoparticles (GVNPs), a unique class of stable, air-filled intracellular proteinaceous nanostructures. GVNPs are an attractive tool for biotechnological applications due to their readily production, purification, and unique physical properties. GVNPs are spindle- or cylinder-shaped, typically with a length of 100 nm to 1.5 μm and a width of 30–250 nm. Multiple monomeric subunits of GvpA and GvpC proteins form the GVNP shell, and several additional proteins are required as minor structural or assembly proteins. The haloarchaeal genetic system has been successfully used to produce and bioengineer GVNPs by fusing several foreign proteins with GvpC and has shown various applications, such as biocatalysis, diagnostics, bioimaging, drug delivery, and vaccine development. Results: We demonstrated that native GvpC can be removed in a low salt buffer during the GVNP purification, leaving the GvpA-based GVNP's shell intact and stable under physiological conditions. Here, we report a genetic engineering and chemical modification approach for functionalizing the major GVNP protein, GvpA. This novel approach is based on combinatorial cysteine mutagenesis within GvpA and genetic expansion of the N-terminal and C-terminal regions. Consequently, we generated GvpA single, double, and triple cysteine variant libraries and investigated the impact of mutations on the structure and physical shape of the GVNPs formed. We used a thiol–maleimide chemistry strategy to introduce the biotechnological relevant activity by maleimide-activated streptavidin–biotin and maleimide-activated SpyTag003-SpyCatcher003 mediated functionalization of GVNPs. Conclusion: The merger of these genetic and chemical functionalization approaches significantly extends these novel protein nanomaterials' bioengineering and functionalization potential to assemble catalytically active proteins, biomaterials, and vaccines onto one nanoparticle in a modular fashion.
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Frankenstein’s data-driven computing approach to model-free mechanics(Computational Mechanics, Springer Science and Business Media LLC, 2023-03-25) [Article]This paper proposes a data-driven method to predict mechanical responses for structures directly from full-field observations obtained on previously tested structures, with minimal introduction of arbitrary models. The fundamental concept is to directly use raw data, called patches from hereon, comprising displacement fields over large domains, obtained during data harvesting through full-field measurement. These displacement fields have been observed on domains of real structures, and hence are naturally viable solutions from static, kinematic, and constitutive viewpoint. We compile a library of such patches to compute response for new structures. Patches are assembled as pieces of a jigsaw puzzle, similar to how Frankenstein put his monster together from human patches. The approach is illustrated using a traditional beam problem for simplicity. However, the approach is not limited to beam or even solid mechanics, the concept can be applied to predict a wide range of physics and multi-physics phenomena.
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Efficient Near-Infrared Electroluminescence from Lanthanide-Doped Perovskite Quantum Cutters(Angewandte Chemie (International ed. in English), Wiley, 2023-03-25) [Article]Perovskite nanocrystals (PeNCs) deliver size and composition-tunable luminescence of high efficiency and color purity in the visible. However, attaining efficient electroluminescence (EL) in the near-infrared (NIR) region from PeNCs is challenging, limiting their potential applications. Here we demonstrate a highly efficient NIR light emitting diode (LED) by doping ytterbium ions into the PeNCs host (Yb3+:PeNCs), extending the EL wavelengths toward 1000 nm, which is achieved through a direct sensitization of Yb3+ ions by the PeNC host. Efficient quantum cutting processes enable high photoluminescence quantum yields (PLQYs) of up to 126% from the Yb3+:PeNCs. Through halide-composition engineering and surface passivation strategy to improve both PLQY and charge transport balance, we demonstrate an efficient NIR LED with a peak EQE of 7.7% at a central wavelength of 990 nm, representing the most efficient perovskite-based LEDs with emission wavelengths beyond 850 nm.
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Editorial Special Issue on Dielectrics for 2-D Electronics(IEEE Transactions on Electron Devices, Institute of Electrical and Electronics Engineers (IEEE), 2023-03-24) [Article, Editorial]It is our great pleasure to introduce this Special Issue on Dielectrics for 2-D Electronics to the IEEE TRANSACTIONS ON ELECTRON DEVICES readership. This Special Issue features the latest research aiming to clarify which would be the most suitable dielectric materials for state-of-the-art electronic devices containing 2-D materials.
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Ferroelectricity in layered bismuth oxide down to 1 nanometer(Science, American Association for the Advancement of Science (AAAS), 2023-03-24) [Article]Atomic-scale ferroelectrics are of great interest for high-density electronics, particularly field-effect transistors, low-power logic, and nonvolatile memories. We devised a film with a layered structure of bismuth oxide that can stabilize the ferroelectric state down to 1 nanometer through samarium bondage. This film can be grown on a variety of substrates with a cost-effective chemical solution deposition. We observed a standard ferroelectric hysteresis loop down to a thickness of ~1 nanometer. The thin films with thicknesses that range from 1 to 4.56 nanometers possess a relatively large remanent polarization from 17 to 50 microcoulombs per square centimeter. We verified the structure with first-principles calculations, which also pointed to the material being a lone pair–driven ferroelectric material. The structure design of the ultrathin ferroelectric films has great potential for the manufacturing of atomic-scale electronic devices.
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Experimental Assessment on the Coupling Effect of Mixing Length and Methane-Ammonia Blends on Flame Stability and Emissions(Energies, MDPI AG, 2023-03-23) [Article]Lean premixed combustion mode has become attractive for utilization in industrial gas turbines due to its ability to meet strict emissions regulations without compromising engine efficiency. In this combustion mode, the mixing process is the key player that affect the flame structure and stability, as well as the generated emissions. Many studies have investigated the aspects that influence premixed flames, including the effects of turbulence, combustor geometry, and level of partial premixing, while mostly using conventional natural gas fuel represented by methane. Recently, ammonia, a sustainable energy source, has been considered in gas turbines due to its carbon-free fuel producing no CO2. Utilizing 100% ammonia or a blend of methane and ammonia alters the combustion performance of a premixed flame due to the variation associated with the physical and chemical properties of ammonia. Thus, investigating the coupling between blend ratios and mixing length of methane-ammonia on flame stability and emissions is an essential step toward implementing ammonia in industrial gas turbines. In this study, the influence of various methane-ammonia blends, from 0 (pure methane) to XNH3 = 75%, and mixing lengths on the flame performance were studied. The mixing length was altered by delaying the injection (i.e., partially premixing) of the ammonia while using a fixed injection location for the reference methane-air mixture. This was done by using three fuel ports located at three different heights upstream of the combustion chamber. The results showed that the flame stability is negatively influenced by increasing (decreasing) ammonia fraction (mixing length ratio) and is more sensitive to the ammonia fraction than to the mixing length. At a constant equivalence ratio, the CO and NOx performances improved positively by increasing the ammonia volume fractions (especially at XNH3 = 75% compared to XNH3 = 25% and 50%) and the mixing length.
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Giant Nonlinear Optical Response via Coherent Stacking of In-Plane Ferroelectric Layers(Advanced Materials, Wiley, 2023-03-23) [Article]Thin ferroelectric materials hold great promise for compact nonvolatile memory, nonlinear optical and optoelectronic devices. Herein, we report an ultrathin in-plane ferroelectric material that exhibits a giant nonlinear optical effect: group-IV monochalcogenide SnSe. Nanometer-scale ferroelectric domains with ∼90°/270° twin boundaries or ∼180° domain walls are revealed in physical vapor deposited SnSe by lateral piezoresponse force microscopy. Atomic structure characterization reveals both parallel and antiparallel stacking of neighboring van der Waals (vdW) ferroelectric layers, leading to ferroelectric or antiferroelectric ordering. Ferroelectric domains exhibit giant nonlinear optical activity due to coherent enhancement of second harmonic fields, and the as-resulted second-harmonic generation was observed to be 100 times more intense than monolayer WS2. This work demonstrates in-plane ferroelectric ordering and giant nonlinear optical activity in SnSe, which paves the way for applications in on-chip nonlinear optical components and nonvolatile memory devices.
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High-performance MTJ-based sensors for monitoring of atmospheric pollution(AIP Advances, AIP Publishing, 2023-03-23) [Article]Solid and liquid particles in the atmosphere, referred to as airborne particulate matter (PM), have been rising significantly over the past two decades. Exposure to PM carries significant health risks such as lungs damage, heart disease, cancer, and death. PM2.5 is a subgroup of PM particles that are smaller than 2.5 µm and is a major concern as it is more harmful to health and more difficult to detect. One problematic component of PM2.5 is magnetite nanoparticles (<200 nm), which are readily absorbed into the bloodstream through the respiratory system. Eventually, magnetite nanoparticles deposit inside the brain causing neurodegenerative diseases such as Alzheimer’s or cancerous tumors by inducing oxidative stress. Additionally, Magnetite nanoparticles are often surrounded by heavy metal nanoparticles such as Cadmium and lead which are a great concern to the environment and health. Traditional PM detection methods such as laser scattering are bulky, expensive, and incapable of detecting particles smaller than 200 nm such as magnetite nanoparticles. Therefore, developing a low-cost highly sensitive sensor for monitoring magnetite nanoparticles is vital. Tunneling Magneto-Resistance (TMR) sensors are an attractive option due to their low-cost and high sensitivity toward magnetic nanoparticle detection. Moreover, developing a cheap, portable, and precise remote monitoring technique will allow for the creation of high spatial resolution highly sensitive monitoring networks for magnetic PM2.5. This work focuses on developing, modeling, and simulation of low-cost highly sensitive TMR sensor based on Magnetic Tunnel Junction (MTJ) that can detect and count magnetite nanoparticles.
