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X-ray Diffraction Line Profile Analysis of Undoped and Se-Doped SnS Thin Films Using Scherrer’s, Williamson–Hall and Size–Strain Plot Methods
摘要： An electrochemical route has been employed to prepare undoped and Se-doped SnS thin films. Six samples including undoped and Se-doped SnS thin films were deposited on the fluorine-doped tin oxide glass substrate. An aqueous solution containing 2 mM SnCl2 and 16 mM Na2S2O3 was used in the electrolyte. Different Se-doped SnS samples were prepared by adding the various amounts of 4 mM SeO2 solution into the electrolyte. The applied potential (E), time of deposition process (t), pH, and bath temperature (T) were kept at -1 V, 30 min, 2.1, and 60°C, respectively. After the completion of the deposition process, x-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to characterize the deposited thin films. XRD patterns clearly showed that the synthesized undoped and Se-doped SnS thin films were crystallized in the orthorhombic structure. Using Scherrer’s method, the crystallite size of deposited thin films is calculated. In addition, the crystallite size and lattice strain have been estimated using the modified form of the Williamson–Hall (W–H) method containing a uniform deformation model, a uniform deformation stress model, a uniform deformation energy density model, and by the size–strain plot method (SSP). The shape of SnS crystals was spherical in TEM images. The results showed that there was a good agreement in the particle size obtained from the W–H method and the SSP method with TEM images.
关键词： thin films,Se-doped SnS,size–strain plot method,Line profile analysis,Williamson–Hall method
更新于2025-09-09 09:28:46
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Enhanced thermal conductivity of MoS2/InSe-nanoparticles/MoS2 hybrid sandwich structure
摘要： MoS2 based hybrid structures have much attention due to their novel structures and potential applications in diverse areas, such as solar energy conversion, thermoelectric power generation and photo-transistors. In the present work, we have fabricated a novel sandwich structure of MoS2/InSe-nano-particles (NPs)/MoS2 layers on SiO2/Si substrate by a combination of chemical vapor deposition and physical vapor deposition methods. The morphology of these structures was also studied using scanning electron microscopy. In addition, we have also explored the thermal properties of these hybrid sandwich structures using temperature and power-dependent Raman spectroscopy. For MoS2/InSe-NPs/MoS2 sample, the first-order temperature coefficients of E1 2g and A1g modes were found to be (cid:1)0.01722 (cid:1)1/K, respectively, which are significantly large compared to MoS2 layers without InSe- and (cid:1)0.01575 cm NPs (i.e. MoS2/MoS2 sample). Further, the thermal conductivity of MoS2/InSe-NPs/MoS2 and MoS2/MoS2 samples on SiO2/Si substrate was extracted as ~102.3 and ~81.7 W/m-K, respectively. This work suggests an effective way to form a novel 2D-MoS2 based sandwich structure with semiconductor/metal-NPs; opening up a new scenario to understand the electronic structure of the hybrid structure, and the local strain introduced by NPs. Electron-phonon interactions at an interface can have significant effects on electrical/thermal transport through the optoelectronic devices.
关键词： Hybrid sandwich structure,Thermal conductivity,Raman spectroscopy,Tensile-strain
更新于2025-09-09 09:28:46
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On-Chip Platform for Slack-Free Carbon Nanotube Resonators
摘要： This work describes an on-chip integrated micro-actuator device for slack-free carbon nanotube (CNT) resonators, improving frequency tunability and Q factor and to study non-linear mode interaction. The device fabricated on SOI wafer with low thermal budget (<600 K) encompasses a restricted symmetrical out-of-plane vibration and a stiff in-plane electro-thermal actuator with a displacement of ~112 nm at 2.7 mW. This corresponds to 5.6% of strain for a 2 μm long suspended carbon nanotube. The in-plane mechanical resonance designed to be far from CNT resonances in MHz regime is measured at 209 kHz. The design is optimized for low power consumption, electrical and thermal isolation and is customized for dry transfer of CNTs.
关键词： carbon nanotube,micro-actuator,strain-sensor,resonator
更新于2025-09-09 09:28:46
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with pentagonal structure
摘要： Structure-property relationships have always been guiding principles for materials discovery. Here we explore the relationships to discover two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo tessellation. We ?nd that this single-layer magnet exhibits an indirect band gap of 1.06 eV with electron and hole effective masses of 0.52 and 1.93 m0, respectively, which may lead to relatively high electron mobility. The hybrid density functional theory calculations correct the band gap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is along the b axis with a sizable MAE of 153 μeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the N′eel temperatures to be 20.4 and 13.3 K using the mean ?eld and random phase approximations, respectively. We then apply biaxial strains to tune the band gap of single-layer pentagonal CoS2. We ?nd that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may ?nd single-layer semiconductor applications in optoelectronic nanodevices.
关键词： two-dimensional materials,magnon frequencies,N′eel temperature,biaxial strain,Cairo tessellation,antiferromagnetic semiconductor,density functional theory,band gap,magnetocrystalline anisotropy energy,pentagonal structure,spintronics
更新于2025-09-09 09:28:46
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In-situ assessment of strain behaviour inside tunnel linings using distributed fibre optic sensors
摘要： In modern tunnelling, deformation monitoring is an important component to ensure a safe construction. It is state of the art to measure displacements at the inner side of the tunnel lining using total stations. In addition, pointwise geotechnical sensors, e.g. electric strain gauges, may be installed in geological fault zones, which, however, do not deliver a complete picture of the internal deformations. The Institute of Engineering Geodesy and Measurement Systems (Graz University of Technology) supported by the Austrian Federal Railways (?BB-Infrastruktur AG, SAE Fachbereich Bautechnik/Tunnelbau) developed a fibre optic sensing system, which realizes thousands of measurement points inside the tunnel lining. The distributed measurements can be used to assess the in-situ strain behaviour as well as to localize failures (e.g. cracks) in the lining. This paper reports about the calibration of the fibre optic system under well-known laboratory conditions and the practical utilization of the system in mechanized and conventional tunnelling. The results demonstrate the high potential of distributed fibre optic systems and their capability especially in the operational phase to extend classical measurement methods in tunnelling projects.
关键词： distributed fibre optic sensors,strain behaviour,deformation monitoring,tunnel linings,in-situ assessment
更新于2025-09-09 09:28:46
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Evolution of ferroelectric and piezoelectric response by heat treatment in pseudocubic BiFeO3–BaTiO3 ceramics
摘要： Heat treatment of ceramics is an important process to tailor the fine electromechanical properties. To explore the criteria for optimized heat treatment in a perovskite structure of (1–x)Bi1.05FeO3–xBaTiO3 (BF–BT100x) system, the structural phase relation, ferroelectric and piezoelectric response of BF–BT36 and BF–BT40 ceramics prepared by furnace cooling (FC) and quenching process were investigated. The X-ray diffraction examination showed single pseudocubic perovskite structure for all the ceramics. The homogenous microstructure was obtained for all ceramics with relatively large grain size in the furnace cooled samples. Well saturated ferroelectric hysteresis loops and enhanced piezoelectric constant (d33 = 97 pC/N) were achieved by quenching process. Dielectric curve of BF–BT36 showed large dielectric constant at its Curie temperature, however, BF–BT40 showed diffused relaxor-like dielectric anomalies. Quenched BF–BT36 samples showed typical butterfly like field induced strain curves, however negative strain decreased in BF–BT40 ceramics. From these investigated study, it is observed that BF–BT ceramics are very sensitive to the heat treatment process (furnace cooling and quenching) on the dielectric, electromechanical properties.
关键词： Quenching process,Electric field induced strain,Dielectric relaxation,BF–BT
更新于2025-09-09 09:28:46
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Valley polarization and biaxial strain dependent conductivity of WS2/SrRuO3(1?1?1) heterostructures
摘要： The electronic structures of monolayer WS2 on top of bilayer SrRuO3(1 1 1) are studied by first-principles calculations with spin-orbital coupling. The electronic properties can be influenced by stacking patterns of WS2/SrRuO3(1 1 1) heterostructures. Meanwhile, the valley polarization can be induced in monolayer WS2 due to the broken time-reversal symmetry by the proximity to bilayer SrRuO3(1 1 1). With particular stacking patterns, larger valley splitting of monolayer WS2 obtained in A1, A3, A4 and A5 models is 11.2, 11.3, 11.1 and 11.1 meV, respectively. Moreover, with biaxial strains, the conductivity of monolayer WS2 can be effectively modulated. The Fermi level moves to a higher energy by appling tensile strains. Then the conductivity of WS2 is governed by the valley states. In addition, the mechanical strains can modify the valley polarization and band gap effectively, showing potential applications in spintronic and valleytronic devices.
关键词： Anomalous Hall effect,Valley polarization,Mechanical strain,Transition metal dichalcogenide
更新于2025-09-09 09:28:46
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Epitaxial ferroelectric oxide thin films for optical applications
摘要： Ferroelectrics are non-centrosymmetric crystalline materials that possess a spontaneous polarization that can be switched by an electric field. The electric-field-dependent optical response of these materials makes them important for optical devices, such as modulators or beam deflectors. In the inexorable drive to miniaturization, the concept of integrated thin film optical devices has led to the incorporation of ferroelectric thin films on single-crystal substrates. These structures have appealing electro-optic modulation characteristics, interesting strain-dependent bandgaps and refractive index, as well as promising possibilities for solar harvesting. Here, we review the work on epitaxial ferroelectric (FE) films for optical applications. We first show that FE thin film materials are attractive for integrated electro-optic modulators and then show that epitaxial strain can be used to enhance the FE and optical functionality of films. Next, we describe some of the photovoltaic functionality of FE thin film materials’ systems and conclude the review by highlighting some thin-film devices that exploit the aforementioned optical effects.
关键词： epitaxial strain,electro-optic modulators,thin films,photovoltaic,optical applications,ferroelectric
更新于2025-09-09 09:28:46
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Metal-insulator transition in V <sub/>2</sub> O <sub/>3</sub> thin film caused by tip-induced strain
摘要： We have demonstrated pressure-induced transition in a c-axis oriented vanadium sesquioxide (V2O3) thin film from a strongly correlated metal to a Mott insulator in a submicrometric region by inducing a local stress using contact atomic force microscopy. To have an access to a pressure range of sub-gigapascal, a tip with a large radius of 335 nm was prepared by chemical vapour deposition of platinum onto a commercial tip with a focused ion beam (FIB). The FIB-modified tip gives a good electrical contact at low working pressures (0.25–0.4 GPa) allowing unambiguously to evidence reversible metal-insulator transition in a pulsed laser-deposited V2O3 thin film by means of local investigations of current-voltage characteristics. A finite element method has confirmed that the diminution of the c/a ratio under this tip pressure explains the observed phase transition of the electron density of states in the film.
关键词： tip-induced strain,Mott insulator,metal-insulator transition,V2O3 thin film,atomic force microscopy
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