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Studies on Temperature and Strain Sensitivities of a Few-mode Critical Wavelength Fiber Optic Sensor
摘要： This paper studied the relationship between the temperature/strain wavelength sensitivity of a fiber optic in-line Mach-Zehnder Interferometer (MZI) sensor and the wavelength separation of the measured wavelength to the critical wavelength (CWL) in a CWL-existed interference spectrum formed by interference between LP01 and LP02 modes. The in-line MZI fiber optic sensor has been constructed by splicing a section of specially designed few-mode fiber (FMF), which support LP01 and LP02 modes propagating in the fiber, between two pieces of single mode fiber. The propagation constant difference, Δβ, between the LP01 and LP02 modes, changes non-monotonously with wavelength and reaches a maximum at the CWL. As a result, in sensor operation, peaks on the different sides of the CWL then shift in opposite directions, and the associated temperature/strain sensitivities increase significantly when the measured wavelength points become close to the CWL, from both sides of the CWL. A theoretical analysis carried out has predicted that with this temperature/strain sensor approach, the temperature/strain wavelength sensitivities are governed by the wavelength difference between the measured wavelength and the CWL. This conclusion was seen to agree well with the experimental results obtained. Combining the wavelength shifts of the peaks and the CWL in the transmission spectrum of the SFS structure, this study has shown that this approach forms the basis of effective designs of high sensitivity sensors for multi-parameter detection and offering a large measurement range to satisfy the requirements needed for better industrial measurements.
关键词： few mode fiber,temperature sensitivity,In-line Mach-Zehnder interferometer,strain sensitivity,critical wavelength
更新于2025-09-09 09:28:46
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Computational design of GeSe/graphene heterojunction based on density functional theory
摘要： Based on density functional theory, we computational designed the hetero junction composed by decreasing the interlayer distance in G/g hetero structure. The height of Schottky barrier can be demonstrated that both the intrinsic electric properties of the GeSe monolayer and graphene are well preserved in G/g hetero structure. It is found that an energy gap of 0.17 eV in graphene is opened by GeSe monolayer and graphene. The effects of interlayer coupling, strains and electric fields on the electronic structures of the designed GeSe/graphene (G/g) hetero structure are explored. We found that applying in-plane strains and the electric fields perpendicular to the G/g hetero structure can control the Schottky barriers at the G/g interface. Our results predict that the ultra-thin G/g hetero structure can be used as two-dimensional semiconductor-based optoelectronic devices.
关键词： density functional,heterostructure,GeSe monolayer,strain,electric field
更新于2025-09-09 09:28:46
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[ASME ASME 2015 International Mechanical Engineering Congress and Exposition - Houston, Texas, USA (Friday 13 November 2015)] Volume 10: Micro- and Nano-Systems Engineering and Packaging - Characterization of the Electronic Properties and Strain Sensitivity of Graphene Formed by C <sub/>2</sub> H <sub/>2</sub> Chemical Vapor Deposition
摘要： We succeed in synthesizing large-area single-layer graphene sheets with different grain size using C2H2 chemical vapor deposition process. Our graphene shows high uniformity and low sheet resistance to 1080Ω/□. By fabricating graphene-based field effect transistors (FETs), the relation between the nucleation density and the electronic properties of CVD graphene are investigated. We found that the nucleation density can severely affect the defects formation in graphene, leading to the change in the electronic properties of graphene. We also check the strain sensitivity of CVD graphene. The as-grown graphene/Cu film was fixed onto the SiO2/Si substrate with a double-sided tape. The strain device is fabricated directly on the graphene-coated Cu standard photolithography and reactive ion etching (RIE) process. Then the device is transferred onto a stretchable and flexible polydimethysiloxane (PDMS) substrate. By using a motorized stage, the piezoresistive properties of graphene-based strain sensors. The one-dimensional tensile test is performed to investigate the piezoresistive properties. A gauge factor 3.4 was achieved under the tensile deformation.
关键词： field effect transistors,chemical vapor deposition,strain sensitivity,graphene,C2H2
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A General Approach for Deformation Induced Stress on Flexible Electronics
摘要： We present a simulation approach that is based on non-linear finite element method. This simulation flow allows to calculate large deformation field and associated stress and strain. The obtained simulation result agrees well with analytic solution. We extend this simulation method to evaluate the impacts of the deformation induced stress on device performance as well as structural integrity.
关键词： bending stress,strain,deformation,flexible devices
更新于2025-09-09 09:28:46
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A Stretchable Graphene Thin-Film Sensor for Detecting All of Lateral and Vertical Strains
摘要： In this work, we propose a stretchable graphene ?lm sensor that can detect all of lateral and vertical strain with unique architecture in single sensor element since most approaches so far are only available for detecting either lateral or vertical strain, but not both. The sensor is fabricated with percolative networks of graphene nanoplatelet using spray-coating method for constructing strain sensing channel and electrode simultaneously. The sensor exhibits a high stretchability of 150% with a gauge factor of 8.56 (0–100%) and 19.8 (100–150%) in the two regimes, for lateral strain. The sensor also presents a high sensitivity for vertically applied pressure in the range of 100–20,000 Pa, belonging to general human pressure perception range. Based on the sensing properties demonstrated, the proposed graphene sensor is a promising candidate for sensor that can detect both lateral and vertical strains in single sensor element.
关键词： Graphene Strain Sensors,Graphene Thin-Film,Graphene Nanoplatelet (GNP),Flexible Transducer,Graphene Pressure Sensors,Graphene
更新于2025-09-04 15:30:14
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Effects of mechanical stretching, desorption and isotope exchange on deuterated eucalypt wood studied by near infrared spectroscopy
摘要： Deuterium exchange combined with near infrared spectroscopy was used to study the roles of accessible and inaccessible cellulose in the load transfer of eucalyptus wood. Monitoring the drying process helped to assign bands of deuterated wood samples. Polarized NIR spectra of protonated and deuterated samples confirmed that inaccessible hydroxyl groups in eucalyptus wood were preferably oriented in the longitudinal direction. The spectral changes on NIR spectra caused by mechanical strain could be highlighted by averaging loading and unloading cycles to compensate for effects of desorption and isotope re-exchange due to environmental fluctuations. After deuteration, the bands affected by mechanical strain at around 6420, 6240 and 4670 cm-1, which had been assigned to hydroxyl groups in cellulose, remained at these positions, suggesting the inaccessible cellulose fraction was the main load-bearing component in wood. A small band at around 4700 cm-1 responding to mechanical strain, becoming visible in the deuterated spectra, indicated that accessible hydroxyls also contributed to the load transfer. Furthermore, the measurements confirmed previous reports of moisture adsorption of wood under tensile stress.
关键词： accessibility,tensile strain,deuterium oxide,cellulose,Eucalyptus regnans,dichroic ratio,hydroxyl groups
更新于2025-09-04 15:30:14
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Accurate semiempirical analytical formulas for spontaneous polarization by crystallographic parameters of SrTiO3-BaTiO3 system by ab initio calculations
摘要： Spontaneous polarizations (PS’s) of BaTiO3 and SrTiO3 under various conditions are calculated ab initio using different exchange-correlation functionals. The extensive theoretical sets of PS vs. ion positions are found to lie on a single curve, despite the chemical differences and the wide variations of PS and lattice parameters. This uncovers accurate simple analytical formulas of PS of SrTiO3-BaTiO3 system expressed by ion positions; a single formula predicts both macroscopic and atomic-scale PS of SrTiO3, BaTiO3 and SrTiO3-BaTiO alloys. The accuracy of the formula is demonstrated by the application to experiments, BaTiO3-SrTiO3 (-CaTiO3) alloys, Sr4Ti4O12 with PS // a-axis, a parallel domain, and a headon domain. In addition, the present results verify empirically that oxygen displacement is the primary identifier and the origin of PS of SrTiO3 and BaTiO3 and indicate that BaTiO3 and SrTiO3 may transforms into new state by an extremely large strain, e.g., ?3%. Furthermore, the earlier prediction of headon domain without aid of defects was confirmed. The present procedures for finding formulas can be applied to other materials.
关键词： Crystallographic estimation,Polarization,Strain,Atom position,Domain,TEM
更新于2025-09-04 15:30:14
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Strain impacts on commensurate bilayer graphene superlattices: distorted trigonal warping, emergence of bandgap and direct-indirect bandgap transition
摘要： Due to low dimensionality, the controlled stacking of the graphene films and their electronic properties are susceptible to environmental changes including strain. The strain-induced modification of the electronic properties such as the emergence and modulation of bandgaps crucially depends on the stacking of the graphene films. However, to date, only the impact of strain on electronic properties of Bernal and AA-stacked bilayer graphene has been extensively investigated in theoretical studies. Exploiting density functional theory and tight-binding calculation, we investigate the impacts of in-plane strain on two different class of commensurate twisted bilayer graphene (TBG) which are even/odd under sublattice exchange (SE) parity. We find that the SE odd TBG remains gapless whereas the bandgap increases for the SE even TBG when applying equibiaxial tensile strain. Moreover, we observe that for extremely large mixed strains both investigated TBG superstructures demonstrate direct-indirect bandgap transition.
关键词： Commensurate bilayer graphene superlattices,Distorted trigonal warping,Strain,Bandgap,Direct-indirect bandgap transition
更新于2025-09-04 15:30:14
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Electronic and electrical properties of siligraphene (g-SiC3) in the presence of several strains
摘要： Based on the first principles density functional theory (DFT), we have investigated the electronic and electrical properties of siligraphene (g-SiC3) under various percentages of strain. Our results show that the electronic and electrical properties can be controlled using (0% to -10%) strain. The behavior of g-SiC3 is altered from a semi metallic to semiconductor. The electronic band gap is opened under -9% and -10% strain. Also, the geometry of g-SiC3 is altered under with these two percentages of strain due to the bond length between C-Si atoms is increasing. The electrical conductivity of siligraphene g-SiC3 as a function temperature without and with strain has been given. We detected very exciting results. It is affected and changed when at the same percentage of strain, which applied to alter the behavior of g-SiC3 to semiconductor. Then, these properties can be led to generate new 2-D nanomaterials and devices with huge control over their physical properties for a wide range of applications ranging from photovoltaic to photo-catalysis. We show that siligraphene is a very promising 2D material with great impact that can lead to exceptional results in the field of solar energy and other application. Consequently, we push the experimental researches to discover this new 2D nanomaterial (siligraphene) for using in solar cell application.
关键词： g-SiC3,DFT,Strain,siligraphene,electronic band gap
更新于2025-09-04 15:30:14
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Universality of strain-induced anisotropic friction domains on 2D materials
摘要： Van der Waals two-dimensional (2D) materials have shown various physical characteristics depending on their growth methods and conditions. Among those characteristics, the surface structural properties are crucial for the application of 2D materials, as the surface structures readily affect their atomic arrangements and/or interaction with substrates due to their atomic-scale thicknesses. Here, we report on the anisotropic friction domains of MoS2 grown not only by chemical vapor deposition (CVD) under various sulfur pressure conditions but also by a mechanical exfoliation process. The 180° periodicity of each domain and the 60° shift between adjacent domains indicate the presence of linearly aligned structures along the armchair direction of MoS2, which is determined by the optical second-harmonic generation method. The anisotropic friction domains of CVD-grown MoS2 ?akes may be attributed to linearly aligned ripples caused by an inhomogeneous strain ?eld distribution, which is due, in turn, to randomly formed nucleation sites on the substrate. The universality of the anisotropic frictional behaviors of 2D materials, including graphene, hBN, and WS2 with honeycomb lattice stacking, which differ from ReSe2 with a distorted triclinic 1T’ structure, supports our assumption based on the linearly aligned ripples along the crystallographic axes, which result from an inhomogeneous strain ?eld.
关键词： strain-induced ripples,chemical vapor deposition,mechanical exfoliation,anisotropic friction domains,Van der Waals two-dimensional materials
更新于2025-09-04 15:30:14