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Large tunability of strain in WO3 single-crystal microresonators controlled by exposure to H2 gas
摘要： Strain engineering is one of the most effective approaches to manipulate the physical state of materials, control their electronic properties, and enable crucial functionalities. Because of their rich phase diagrams arising from competing ground states, quantum materials are an ideal playground for on-demand material control, and can be used to develop emergent technologies, such as adaptive electronics or neuromorphic computing. It was recently suggested that complex oxides could bring unprecedented functionalities to the field of nanomechanics, but the possibility of precisely controlling the stress state of materials is so far lacking. Here we demonstrate the wide and reversible manipulation of the stress state of single-crystal WO3 by strain engineering controlled by catalytic hydrogenation. Progressive incorporation of hydrogen in freestanding ultra-thin structures determines large variations of their mechanical resonance frequencies and induces static deformation. Our results demonstrate hydrogen doping as a new paradigm to reversibly manipulate the mechanical properties of nanodevices based on materials control.
关键词： Tungsten Trioxide,Hydrogen Doping,MicroElectroMechanical Systems,WO3,Transition Metal Oxides,Oxide MEMS,Strain Engineering,Chemical Strain
更新于2025-09-11 14:15:04
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55.1: <i>Invited Paper:</i> Achieving high uniformity of 200 mm GaN‐on‐Si LED epiwafers for micro LED applications
摘要： One of the big challenges of micro LED displays is to reduce cost/increase yield and establish excellent manufacturability. Galliumnitride on silicon (GaN-on-Si) LED epiwafers offer fundamental cost advantages to the entire process flow for micro LEDs compared with conventional GaN-on-sapphire LED epiwafers. However, due to the difficulties of epitaxial growth of GaN-on-Si, demonstration of such cost advantages in micro LED application is not wide-spread yet. In this presentation, we have demonstrated excellent emission uniformity with well- controlled strain by precise strain-engineering. This opens the way to use the advantages of GaN-on-Si LED epiwafers in the entire supply chain of micro LED making and thus reduce cost significantly and enable high yield manufacturing.
关键词： curvature,GaN-on-Si,200 mm epiwafer,reproducibility,micro LED,emission wavelength uniformity,strain-engineering
更新于2025-09-11 14:15:04
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Pulsed Laser Deposition of Rocksalt Magnetic Binary Oxides
摘要： Magnetic binary oxides with the rocksalt structure constitute an important class of materials for potential applications as electronic or electrochemical devices. Moreover, they often become a theoretical playground, due to the simple electronic and crystal structures, in the quest for novel phenomena. For these possibilities to be realized, a necessary prerequisite would be to grow atomically ordered and controllably-strained binary oxides on proper substrates. Here we systematically explore the use of pulsed laser deposition technique (PLD) to grow three basic oxides that have rocksalt structure but different chemical stability in the ambient atmosphere: NiO (stable), MnO (metastable) and EuO (unstable). By tuning laser fluence FL, an epitaxial single-phase NiO thin-film growth can be achieved in a wide range of growth temperatures 10 ≤ TG ≤750 °C. At the lowest TG, the out-of-plane strain raises to 1.5%, which is five times higher than in NiO film grown at 750 °C. MnO thin films that had long-range order were successfully deposited on the MgO substrates after appropriate tuning of deposition parameters. The growth of MnO phase was strongly influenced by FL and the TG. EuO films with satisfactory quality were deposited by PLD after oxygen availability had been minimized. Synthesis of EuO thin films at rather low TG = 350 °C prevented thermally-driven lattice relaxation and allowed growth of strained films. Overall, PLD was a quick and reliable method to grow binary oxides with rocksalt structure in high quality that can satisfy requirements for applications and for basic research.
关键词： Thin films,Nickel monoxide,Long-range ordered,Manganese monoxide,Europium monoxide,Strain engineering
更新于2025-09-11 14:15:04
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Anisotropic Electron–Phonon Interactions in Angle-Resolved Raman Study of Strained Black Phosphorus
摘要： Few layer black phosphorus (BP) with in-plane puckered crystalline structure has attracted intense interest for strain engineering owing to both its significant anisotropy in mechanical and electrical properties as well its high intrinsic strain limit. Here we investigated the phonon response of few layer BP under uniaxial tensile strain (~7%) with in-situ polarized Raman spectroscopy. Together with the first-principles density functional theory (DFT) analysis, the anisotropic Poisson’s ratio in few-layer BP was verified as one of the primary factors that caused the large discrepancy in the trend of reported Raman frequency shift for strained BP, armchair (AC) direction in particular. By carefully including and excluding the anisotropic Poisson’s effect in the DFT emulations, we rebuilt both trends reported for Raman modes shift. Furthermore, the angle-resolved Raman spectroscopy was conducted in-situ under tensile strain for systematic investigation of the in-plane anisotropy of BP phonon response. The experimentally observed thickness and crystallographic orientation dependence is elaborated using DFT theory as strong correlation between the strain perturbated electronic band structure and the phonon vibration modes. This study provides insight, both experimentally and theoretically, for the complex electron-phonon interaction behavior in strained BP, which enables diverse possibilities for strain engineering of electrical and optical properties in BP and alike two-dimensional (2D) nano materials.
关键词： black phosphorus,anisotropic Poisson’s ratio,electron-phonon interactions,angle-resolved Raman spectroscopy,strain engineering
更新于2025-09-10 09:29:36
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Experimental Characterization of the Influence of Transverse Prestrain on the Piezoresistive Coefficients of Heavily Doped n-Type Silicon
摘要： Strain has been integrated into many silicon devices, as it has an essential impact on carrier mobility and crystal symmetry. Those parameters respond differently under both biaxial and uniaxial, so their effect needs to be quantified to successfully employ the strain engineering in different silicon applications. As an extended step toward utilizing strain in enhancing the sensitivity and the temperature independency of a 3-D stress sensor, the effect of uniaxial transverse strain onto the piezoresistive (PR) coefficients of heavily doped n-type silicon will be experimentally characterized. A new design was developed to apply the transverse tensile and compressive uniaxial stresses onto the silicon substrate using a highly compressive nitride layer. This stressing technique was integrated with six PR elements rosette to fully calibrate the PR coefficients, where unstrained, tensile, and compressive strained PRs are fabricated within the same chip to accurately quantify the strain impact. Four-point bending, stress-free temperature, and hydrostatic test were used to typically measure the PR coefficients. Strain values of 0.065% and 0.083% ε were achieved locally using both the tensile and compressive stressors, respectively. Under this level of strain, the typical result shows opposite impact for both the tensile and compressive transverse strains on the longitudinal and transverse PR coefficients. Moreover, an increase up to 80% can be achieved for the pressure coefficient of heavily doped n-type silicon due to the compressive transverse strain.
关键词： metal–oxide–semiconductor (MOS) local transistors,3-D piezoresistive (PR) sensor,n-type silicon,strain,strain engineering,piezoresistivity
更新于2025-09-09 09:28:46
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Engineering SrSnO <sub/>3</sub> Phases and Electron Mobility at Room Temperature Using Epitaxial Strain
摘要： High-speed electronics require epitaxial films with exceptionally high carrier mobility at room temperature. Alkaline-earth stannates with high room-temperature mobility show outstanding prospects for oxide electronics operating at ambient temperatures. However, despite significant progress over the last few years, mobility in stannate films has been limited by dislocations due to the inability to grow fully coherent films. Here, we demonstrate the growth of coherent, strain-engineered phases of epitaxial SrSnO3 (SSO) films using a radical-based molecular beam epitaxy approach. Compressive strain stabilized the high-symmetry tetragonal phase of SSO at room temperature (RT), which, in bulk, exists only at temperatures between 1062 K and 1295 K. We achieved a mobility enhancement of over 300% in doped films compared with the low temperature orthorhombic polymorph. Using comprehensive temperature-dependent synchrotron-based X-ray measurements, electronic transport and first principles calculations, crystal and electronic structures of SSO films were investigated as a function of strain. We argue that strain-engineered films of stannate will enable high mobility oxide electronics operating at RT with the added advantage of being optically transparent.
关键词： phase transition,Hybrid molecular beam epitaxy,half-order diffraction,strain engineering,density functional theory,high mobility,Octahedral rotations
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Lausanne (2018.7.29-2018.8.2)] 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Elastic Strain Engineering for Ultralow Mechanical Dissipation
摘要： Extreme stresses can be produced in nanoscale structures, a feature which has been used to realize enhanced materials properties, such as the high mobility of silicon in modern transistors. Here we show how nanoscale stress can be used to realize exceptionally low mechanical dissipation, when combined with “soft-clamping” — a form of phononic engineering. Specifically, using a non-uniform phononic crystal pattern, we colocalize the strain and flexural motion of a free-standing Si3N4 nanobeam. Ringdown measurements at room temperature reveal string-like modes with quality (Q) factors as high as 800 million and Q × frequency exceeding 1015 Hz.
关键词： optomechanics,strain engineering,nanomechanics
更新于2025-09-09 09:28:46
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Semiconducting defect-free polymorph of borophene: Peierls distortion in two dimensions
摘要： In contrast to the well-defined lattices of various two-dimensional (2D) systems, the atomic structure of borophene is sensitive to growth conditions and type of the substrate which results in rich polymorphism. By employing ab initio methods, we reveal a thermodynamically stable borophene polymorph without vacancies which is a semiconductor unlike the other known boron sheets, in the form of an asymmetric centered-washboard structure. Our results indicate that asymmetric distortion is induced due to Peierls instability which transforms a symmetric metallic system into a semiconductor. We also show that applying uniaxial or biaxial strain gradually lowers the obtained band gap and the symmetric configuration is restored following the closure of the band gap. Furthermore, while the Poisson’s ratio is calculated to be high and positive in the semiconducting regime, it switches to negative once the metallicity is retrieved. The realization of semiconducting borophene polymorphs without defects and tunability of its electronic and mechanical response can extend the usage of boron sheets in a variety of nanoelectronic applications.
关键词： Peierls distortion,strain engineering,two-dimensional materials,semiconductor,borophene
更新于2025-09-09 09:28:46
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Strain engineering of chevron graphene nanoribbons
摘要： In this work, we theoretically investigate the material and transport properties of strained chevron graphene nanoribbons (CGNRs) which can be easily synthesized by the bottom-up fabrication technology. Because of the unique atomic structures, the energy and pressure of the CGNRs vary asymmetrically along compressive and tensile strains. Under the two strain directions, the CGNRs’ bandgaps and carrier effective masses in the conduction band minimum and the valence band maximum are all reduced. The transport properties are promoted accordingly, except some negative differential conductance behaviors caused by energy state localizations. When the tensile strains exceed a criterion value, the C–C bonds in the inner sides of the CGNR corners will be broken in sequence. Meanwhile, the CGNRs can restore their initial unstrained states rapidly when the strains are removed. However, if the broken bonds are saturated by foreign atoms, such as H, a novel kind of stable carbon structure will be obtained. The investigations suggest possible applications of strain engineered CGNRs in transport devices.
关键词： carrier effective masses,strain engineering,transport properties,chevron graphene nanoribbons,bandgap
更新于2025-09-04 15:30:14