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Results for “Strain engineering”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Imaging supermoiré relaxation in helical trilayer graphene

In twisted van der Waals materials, local atomic relaxation can alter the underlying electronic structure. Characterizing lattice reconstruction and its susceptibility to strain is essential for understanding emergent electronic states, especially in multilayers in which interference between moiré lattices yields larger supermoiré patterns whose energy is highly sensitive to local stacking. Here, in this study, we image spatial modulations in the electronic character of helical trilayer graphene, which indicate relaxation into a superstructure of large domains with uniform moiré periodicity. We show that the supermoiré domain size is increased by strain and can be altered in the same device while preserving the local properties within each domain. Finally, we observe a higher conductance at the domain boundaries, consistent with predictions that they host counterpropagating edge modes. Our work provides a real-space visualization of moiré-periodic domains, reveals two independently tunable length scales and demonstrates strain engineering as a route towards designing correlated topological networks at the supermoiré scale.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Relation between interfacial shear and friction force in 2D materials

Understanding the interfacial properties between an atomic layer and its substrate is of key interest at both the fundamental and technological levels. From Fermi level pinning to strain engineering and superlubricity, the interaction between a single atomic layer and its substrate governs electronic, mechanical and chemical properties. Here, we measure the hardly accessible interfacial transverse shear modulus of an atomic layer on a substrate. By performing measurements on bulk graphite, and on epitaxial graphene films on SiC with different stacking orders and twisting, as well as in the presence of intercalated hydrogen, we find that the interfacial transverse shear modulus is critically controlled by the stacking order and the atomic layer–substrate interaction. Importantly, we demonstrate that this modulus is a pivotal measurable property to control and predict sliding friction in supported two-dimensional materials. The experiments demonstrate a reciprocal relationship between friction force per unit contact area and interfacial shear modulus. As a result, the same relationship emerges from simulations with simple friction models, where the atomic layer– substrate interaction controls the shear stiffness and therefore the resulting friction dissipation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stress-tolerant non-conventional microbes enable next-generation chemical biosynthesis

Microbial chemical production is a rapidly growing industry, with much of the growth fueled by advances in synthetic biology. New approaches have enabled rapid strain engineering for the production of various compounds; however, translation to industry is often problematic because native phenotypes of model hosts prevent the design of new low-cost bioprocesses. Here, in this work, we argue for a new approach that leverages the native stress-tolerant phenotypes of non-conventional microbes that directly address design challenges from the outset. Growth at high temperature, high salt and solvent concentrations, and low pH can enable cost savings by reducing the energy required for product separation, bioreactor cooling, and maintaining sterile conditions. These phenotypes have the added benefit of allowing for the use of low-cost sugar and water resources. Non-conventional hosts are needed because these phenotypes are polygenic and thus far have proven difficult to recapitulate in the common hosts Escherichia coli and Saccharomyces cerevisiae.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Strain effects on stability of topological ferroelectric polar configurations in (PbTiO3) n /(SrTiO3) n superlattices

The (PbTiO3)n/(SrTiO3)n (PTO/STO) superlattice system has been shown to exhibit interesting topological phases (e.g., vortices and skyrmions) in addition to normal ferroelectric domain states. Existing studies are mostly focused on the dependence of topological polar distributions and properties of PTO/STO superlattice on its periodicity. Here, we study the strain effect on the topological phase transitions and ferroelectric domain structures employing phase-field simulations. We summarized in an isotropic strain (in-plane misfit strain along the x direction is equal to that along the y direction) periodicity phase diagram displaying the stability regions of different polar topological states, including normal ferroelectric twins, vortices, skyrmions, and mixtures of vortices and twins. We also analyzed the polarization configurations under anisotropic in-plane strains (in-plane misfit strain along the x direction is not equal to that along the y direction) and demonstrated that the strain anisotropy can be used to tune the directions of vortex arrays along either the [100] pc or [010] pc directions or labyrinth vortex arrays. This work offers guidance to manipulating polar structures in the PTO/STO superlattices via strain engineering.

Physics↗
DOE OSTI2025

Magnetic compressibility of layered ferromagnet under pressure

This study systematically investigates the magnetic properties of the layered ferromagnet MnPt 5 As under pressure through a combination of experimental measurements and theoretical simulations. MnPt 5 As exhibits a ferromagnetic transition at approximately 301 K. Neutron diffraction measurements under applied pressures up to ∼4.9 GPa were performed over a temperature range from 320 to 100 K to probe its magnetic behavior. The results confirm that the Mn atoms maintain a ferromagnetic order under applied pressures, consistent with the ambient-pressure findings. However, magnetic anisotropy is notably suppressed. To further elucidate the compressibility of magnetic anisotropy in MnPt 5 As, x-ray diffraction under pressure was conducted. The results reveal that the c-axis undergoes a greater and more rapid compression compared to the ab -plane, which may contribute to the observed suppression of Mn ferromagnetic ordering along the c -axis. Additionally, theoretical calculations indicate that magnetic ordering exhibits a similar pressure-induced trend under applied pressure, supporting the experimental observations. These findings offer insights into the pressure-dependent magnetic properties and anisotropy of MnPt 5 As, with potential implications for strain engineering in Mn-based magnetic devices.

Electronic band structure↗
DOE OSTI2025

Modeling strain and quantum confinement in GaAs/Ga x In 1−x P superlattices for spin-polarized electron sources

In this study, we systematically design and simulate a series of GaAs-based superlattice configurations aimed at enhancing heavy-hole–light-hole band splitting while simultaneously optimizing band alignment to reduce the conduction band barrier, thereby facilitating efficient electron transport. These combined effects are crucial for achieving high electron spin polarization and high quantum efficiency, the two key performance metrics of next-generation spin-polarized electron sources. We investigated three types of superlattice architectures: (1) compressively strained GaAs wells on GaInP barriers, yielding a maximum band splitting of 140 meV, (2) lattice-matched GaAs/GaInP structures, resulting in the maximum band splitting of 75 meV, and (3) tensile strained GaAs wells on GaInP barriers, with a maximum band splitting of 40 meV. The results demonstrate the tunability of heavy-hole–light-hole band splitting and establish a design framework for high-performance spin-polarized photocathodes based on a combination of strain engineering, quantum confinement, and optimized heterostructure design.

Electron sources↗
DOE OSTI2025

How transparent is graphene? A surface science perspective on remote epitaxy

Remote epitaxy is the synthesis of a single crystalline film on a graphene-covered substrate, where the film adopts epitaxial registry to the substrate as if the graphene is transparent. Despite many exciting applications for flexible electronics, strain engineering, and heterogeneous integration, an understanding of the fundamental synthesis mechanisms remains elusive. Here we offer a perspective on the synthesis mechanisms, focusing on the foundational assumption of graphene transparency. We identify challenges for quantifying the strength of the remote substrate potential that permeates through graphene, and propose Fourier and beating analysis as a bias-free method for decomposing the lattice potential contributions from the substrate, from graphene, and from surface reconstructions, each at different frequencies. We highlight the importance of graphene-induced reconstructions on epitaxial templating, drawing comparison to moiré epitaxy. We highlight the role of the remote potential in tuning surface diffusion and adatom kinetics on graphene, which are crucial for navigating the competition between remote epitaxy and defect-seeded mechanisms like pinhole epitaxy. In light of this weak remote potential, we re-evaluate the current state-of-the-art experimental evidence, highlighting why it remains challenging to experimentally validate a ‘remote’ epitaxy mechanism that cannot be explained by alternatives, such as pinhole-seeded epitaxy or serial van der Waals epitaxy. We end with one experimental example that, to out knowledge, cannot be explained by competing mechanisms: a different long-range epitaxial relationship for GdPtSb films grown on graphene/sapphire, compared to direct epitaxy on sapphire. We suggest for future experiments that directly measure the remote potential and impact of tuneable growth kinetics.

epitaxy↗
DOE OSTI2022

Comparative chemical genomic profiling across plant-based hydrolysate toxins reveals widespread antagonism in fitness contributions

Abstract The budding yeast Saccharomyces cerevisiae has been used extensively in fermentative industrial processes, including biofuel production from sustainable plant-based hydrolysates. Myriad toxins and stressors found in hydrolysates inhibit microbial metabolism and product formation. Overcoming these stresses requires mitigation strategies that include strain engineering. To identify shared and divergent mechanisms of toxicity and to implicate gene targets for genetic engineering, we used a chemical genomic approach to study fitness effects across a library of S. cerevisiae deletion mutants cultured anaerobically in dozens of individual compounds found in different types of hydrolysates. Relationships in chemical genomic profiles identified classes of toxins that provoked similar cellular responses, spanning inhibitor relationships that were not expected from chemical classification. Our results also revealed widespread antagonistic effects across inhibitors, such that the same gene deletions were beneficial for surviving some toxins but detrimental for others. This work presents a rich dataset relating gene function to chemical compounds, which both expands our understanding of plant-based hydrolysates and provides a useful resource to identify engineering targets.

09 BIOMASS FUELS↗
DOE OSTI2023

Insights into the transcriptional regulation of poorly characterized alcohol acetyltransferase-encoding genes (HgAATs) shed light into the production of acetate esters in the wine yeast Hanseniaspora guilliermondii

Abstract Hanseniaspora guilliermondii is a well-recognized producer of acetate esters associated with fruity and floral aromas. The molecular mechanisms underneath this production or the environmental factors modulating it remain unknown. Herein, we found that, unlike Saccharomyces cerevisiae, H. guilliermondii over-produces acetate esters and higher alcohols at low carbon-to-assimilable nitrogen (C:N) ratios, with the highest titers being obtained in the amino acid-enriched medium YPD. The evidences gathered support a model in which the strict preference of H. guilliermondii for amino acids as nitrogen sources results in a channeling of keto-acids obtained after transamination to higher alcohols and acetate esters. This higher production was accompanied by higher expression of the four HgAATs, genes, recently proposed to encode alcohol acetyl transferases. In silico analyses of these HgAat’s reveal that they harbor conserved AATs motifs, albeit radical substitutions were identified that might result in different kinetic properties. Close homologues of HgAat2, HgAat3, and HgAat4 were only found in members of Hanseniaspora genus and phylogenetic reconstruction shows that these constitute a distinct family of Aat’s. These results advance the exploration of H. guilliermondii as a bio-flavoring agent providing important insights to guide future strategies for strain engineering and media manipulation that can enhance production of aromatic volatiles.

Seixas, Isabel↗
DOE OSTI2022

Rubisco regulation in response to altered carbon status in the cyanobacterium Synechococcus elongatus PCC 7942

Abstract Photosynthetic organisms possess a variety of mechanisms to achieve balance between absorbed light (source) and the capacity to metabolically utilize or dissipate this energy (sink). While regulatory processes that detect changes in metabolic status/balance are relatively well studied in plants, analogous pathways remain poorly characterized in photosynthetic microbes. Here, we explored systemic changes that result from alterations in carbon availability in the model cyanobacterium Synechococcus elongatus PCC 7942 by taking advantage of an engineered strain where influx/efflux of a central carbon metabolite, sucrose, can be regulated experimentally. We observed that induction of a high-flux sucrose export pathway leads to depletion of internal carbon storage pools (glycogen) and concurrent increases in estimates of photosynthetic activity. Further, a proteome-wide analysis and fluorescence reporter-based analysis revealed that upregulated factors following the activation of the metabolic sink are concentrated on ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and auxiliary modules involved in Rubisco maturation. Carboxysome number and Rubisco activity also increased following engagement of sucrose secretion. Conversely, reversing the flux of sucrose by feeding exogenous sucrose through the heterologous transporter resulted in increased glycogen pools, decreased Rubisco abundance, and carboxysome reorganization. Our data suggest that Rubisco activity and organization are key variables connected to regulatory pathways involved in metabolic balancing in cyanobacteria.

Plant Sciences↗
DOE OSTI2020

Large spin Hall effect in Si at room temperature

Silicon's weak intrinsic spin-orbit coupling and centrosymmetric crystal structure are a critical bottleneck to the development of Si spintronics, because they lead to an insignificant spin Hall effect (spin current generation) and inverse spin Hall effect (spin current detection). In this work, we undertake current, magnetic field, crystallography dependent magnetoresistance, and magnetothermal transport measurements to study the spin transport behavior in freestanding Si thin films. We observe a large spin Hall magnetoresistance in both $\mathcal{p}$ – Si and $\mathcal{n}$ – Si at room temperature and it is an order of magnitude larger than that of Pt. One explanation of the unexpectedly large and efficient spin Hall effect is spin-phonon coupling instead of spin-orbit coupling. The macroscopic origin of the spin-phonon coupling can be large strain gradients that can exist in the freestanding Si films. This discovery in a light, earth abundant and centrosymmetric material opens a new path of strain engineering to achieve spin dependent properties in technologically highly developed materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Stress-induced phase transitions in nanoscale CuInP 2 S 6

Using the Landau-Devonshire approach and available experimental results, we constructed multiwell thermodynamic potential of the layered ferroelectric CuInP 2 S 6 (CIPS). The analysis of temperature dependences of the dielectric permittivity and lattice constants for different applied pressures unexpectedly reveals the critically important role of a nonlinear electrostriction in this material. With the nonlinear electrostriction included we calculated the temperature and pressure phase diagrams and spontaneous polarization of a bulk CIPS, within the assumed range of applicable temperatures and applied pressures. Using the developed thermodynamic potential, we revealed the strain-induced phase transitions in thin epitaxial СIPS films, as well as the stress-induced phase transitions in СIPS nanoparticles, the shape of which varies from prolate needles to oblate disks. Furthermore, w also revealed the strong influence of a mismatch strain, elastic stress, and shape anisotropy on the phase diagrams and polar properties of a nanoscale CIPS, and derived analytical expressions allowing for elastic control of the nanoscale CIPS polar properties. Hence obtained results can be of particular interest for the strain engineering of nanoscale layered ferroelectrics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

First-principles study of electron transport in ScN

We investigate the conduction-band structure and electron mobility in rocksalt ScN based on density functional theory. The first-principles band structure allows us to obtain band velocities and effective masses as a function of energy. Electron-phonon scattering is assessed by explicitly computing the q-dependent electron-phonon matrix elements, with the inclusion of the long-range electrostatic interaction. The influence of free-carrier screening on the electron transport is assessed using the random phase approximation. We find a notable enhancement of electron mobility when the carrier concentration exceeds 10 20 cm -3 . We calculate the room-temperature electron mobility in ScN to be 587 cm2 /Vs at low carrier concentrations. When the carrier concentration is increased, the electron mobility starts to decrease significantly around n = 10 19 cm -3 , and drops to 240 cm 2 /Vs at n = 10 21 cm -3 . We also explore the influence of strain in (111)- and (100)-oriented ScN films. For (111) films, we find that a 1.0% compressive epitaxial strain increases the in-plane mobility by 72 cm 2 /Vs and the out-of-plane mobility by 50 cm 2 /Vs. For (100) films, a 1.0% compressive epitaxial strain increases the out-of-plane mobility by as much as 172 cm2 /Vs, but has a weak impact on the in-plane mobility. Our study sheds light on electron transport in ScN at different electron concentrations and shows how strain engineering could increase the electron mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Theory of nonlinear terahertz susceptibility in ferroelectrics

An analytical theory is developed for predicting the nonlinear susceptibility of ionic polarization to continuous electromagnetic waves in both bulk and strained thin film ferroelectrics. Using a perturbation method for solving the nonlinear equation of motion for ionic polarization within the framework of Landau-Ginzburg-Devonshire theory, the full second-order nonlinear susceptibility tensor is derived as a function of frequency, temperature, and strain. Here, the theory predicts the coexistence of a significantly enhanced second-order dielectric susceptibility and a relatively low dielectric loss in BaTiO 3 films with a strain-stabilized monoclinic ferroelectric phase and in a strained SrTiO 3 film near its temperature-driven second-order ferroelectric-to-paraelectric phase transition. In this paper, we establish a theoretical framework for predicting and exploiting nonlinear interactions between terahertz waves and ferroelectric materials and, more generally, suggest exciting opportunities to strain-engineer nonlinear dynamical properties of ferroelectrics beyond the static and quasistatic limits.

36 MATERIALS SCIENCE↗