Showing papers on "Lattice constant published in 2019"
16 Jan 2019
TL;DR: Chuang et al. as mentioned in this paper explored the electronic properties of PtX2 with respect to film thickness and found that octahedral 1T is the most stable, whereas the 3R structure has comparable stability relative to the 1T, implying possible synthesis of 3R.
Abstract: Platinum-based transition metal dichalcogenides have been gaining renewed interest because of the development of a new method to synthesize thin film structures. Here, using first-principles calculation, we explore the electronic properties of PtX2 (X = S, Se, and Te) with respect to film thickness. For bulk and layered structures (1 to 10 layers), octahedral 1T is the most stable. Surprisingly, we also find that the 3R structure has comparable stability relative to the 1T, implying possible synthesis of 3R. For a bulk 1T structure, PtS2 is semiconducting with an indirect band gap of 0.25 eV, while PtSe2 and PtTe2 are both semi-metallic. Still, all their corresponding monolayers exhibit an indirect semiconducting phase with band gaps of 1.68, 1.18, and 0.40 eV for PtS2, PtSe2, and PtTe2, respectively. For the band properties, we observe that all these materials manifest decreasing/closing of indirect band gap with increasing thickness, a consequence of quantum confinement and interlayer interaction. Moreover, we discover that controlling the thickness and applying strain can manipulate van Hove singularity resulting to high density of states at the maximum valence band. Our results exhibit the sensitivity and tunability of electronic properties of PtX2, paving a new path for future potential applications. Layered Pt-based dichalcogenides possess thickness-dependent electronic band structures. A team led by Feng-Chuan Chuang at National Sun Yat-Sen University performed first-principles calculations to investigate the interplay between thickness and electronic properties of PtX2 dichalcogenides, where X = S, Se, and Te. In bulk PtX2, the most stable configuration was found to be 1T, although the metastable 3R structure had comparable formation energy, indicating that both 1T and 3R polytypes could be synthesized experimentally. To explore the thickness-dependent properties of PtX2, bulk lattice constants were used to construct the layered structures from monolayer up to ten layers, followed by crystal structure relaxations, and it was consistently found that the electronic band gap decreases as the number of layers increases. Furthermore, PtS2 possesses diverging density of states, indicative of possible presence of van Hove singularities.
127 citations
TL;DR: In this paper, the authors revealed the principles for regulating both the elastic and plastic behaviors by composition modification and Mo addition in an fcc-phase quaternary CoCrFeNi system with the assistance of ab initio and thermodynamics calculations.
123 citations
TL;DR: In this paper, a homogeneous precipitation method was used to synthesize ZnO, NiO nanoparticles and ZnNO-NiO nanocomposites with and without surfactants, sodium dodecyl sulphate (SDS) and hexamethylenetetramine (HMT) to alter the composition of nanocomposition.
102 citations
TL;DR: In this article, the formation of cubic phase of spinel Co-Zn ferrite NPs were confirmed through XRD, FT-IR and FE-SEM techniques, and the structural investigation of NPs by XRD revealed that the lattice parameter "a" decreases with the introduction of the RE in the ferrite structure by the substitution of Fe3+ by RE ions.
99 citations
TL;DR: In this article, the authors investigated the solid solution strengthening effect in AlxCoCrNi medium-entropy alloy (MEA) with different Al content (x 0 − 7 ǫ ).
96 citations
TL;DR: In this article, the solid solution formation and consolidation of the (Ta,Zr,Nb)C single-phase ceramic made from commercial TaC, ZrC and NbC powders prepared by spark plasma sintering at the temperature of 1920°C was investigated.
96 citations
TL;DR: In this paper, the elastic I = 1 p-wave ππ scattering amplitude is calculated together with the isovector timelike pion form factor using lattice QCD with N f = 2 + 1 dynamical quark flavors.
93 citations
TL;DR: In this article, the biaxial strain effects on the orbital, spin-orbit, and optical properties of monolayer transition-metal dichalcogenides (TMDCs) were analyzed using ab initio calculations.
Abstract: When considering transition-metal dichalcogenides (TMDCs) in van der Waals heterostructures for periodic ab initio calculations, usually, lattice mismatch is present, and the TMDC needs to be strained. In this study we provide a systematic assessment of biaxial strain effects on the orbital, spin-orbit, and optical properties of the monolayer TMDCs using ab initio calculations. We complement our analysis with a minimal tight-binding Hamiltonian that captures the low-energy bands of the TMDCs around the $K$ and ${K}^{\ensuremath{'}}$ valleys. We find characteristic trends of the orbital and spin-orbit parameters as a function of the biaxial strain. Specifically, the orbital gap decreases linearly, while the valence (conduction) band spin splitting increases (decreases) nonlinearly in magnitude when the lattice constant increases. Furthermore, employing the Bethe-Salpeter equation and the extracted parameters, we show the evolution of several exciton peaks, with biaxial strain, on different dielectric surroundings, which are particularly useful for interpreting experiments studying strain-tunable optical spectra of TMDCs.
90 citations
TL;DR: In this paper, the synergetic optimization of electronic and thermal transport properties in rhombohedral GeTe doped with transition metal Ti is reported, where the Seebeck coefficient of Ge1-xTixTe is significantly increased and the corresponding thermal conductivity is decreased.
89 citations
TL;DR: The results show that epitaxial growth of antimonene on different substrates allow the electronic properties of these films to be tuned by substrate-induced strain and stress.
Abstract: Antimonene, a new semiconductor with fundamental bandgap and desirable stability, has been experimentally realized recently. However, epitaxial growth of wafer-scale single-crystalline monolayer antimonene preserving its buckled configuration remains a daunting challenge. Here, Cu(111) and Cu(110) are chosen as the substrates to fabricate high-quality, single-crystalline antimonene via molecular beam epitaxy (MBE). Surface alloys form spontaneously after the deposition and postannealing of Sb on two substrates that show threefold and twofold symmetry with different lattice constants. Increasing the coverage leads to the epitaxial growth of two atomic types of antimonene, both exhibiting a hexagonal lattice but with significant difference in lattice constants, which are observed by scanning tunneling microscopy. Scanning tunneling spectroscopy measurements reveal the strain-induced tunable bandgap, in agreement with the first-principles calculations. The results show that epitaxial growth of antimonene on different substrates allow the electronic properties of these films to be tuned by substrate-induced strain and stress.
79 citations
TL;DR: In this article, the formation of a single cubic spinel phase of Co2+ doped nickel ferrite nanoparticles is confirmed by X-ray diffraction analysis, and their structural properties, such as lattice parameter, average crystal size and Xray density are investigated in detail.
TL;DR: In this article, double perovskite Ba2InTaO6 was investigated in terms of its structural, electronic, optical, elastic, mechanical, thermodynamic and thermoelectric properties using density-functional theory.
Abstract: In the present paper, double perovskite Ba2InTaO6 was investigated in terms of its structural, electronic, optical, elastic, mechanical, thermodynamic and thermoelectric properties using density-functional theory (DFT). The generalized gradient approximation (GGA) in the scheme of Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson (mBJ) potential were employed for the exchange–correlation potential. The computed lattice constant was found to be in agreement with the available experimental and theoretical results. The electronic profile shows a semiconducting nature. Further analysis of the complex dielectric constant e(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity (ω) and energy loss function were also reported with the incident photon energy. The elastic constants were also calculated and used to determine mechanical properties like Young's modulus (Y), the shear modulus (G), Poisson's ratio (ν) and the anisotropic factor (A). The electrical conductivity (σ/τ) and Seebeck coefficient (S) also demonstrated the semiconducting nature of the compound with electrons as the majority carriers. The value of the power factor was calculated to be 1.20 × 1012 W K−2 m−1 s−1 at 1000 K. From thermodynamic investigations, the heat capacity and Gruneisen parameter were also predicted.
TL;DR: In this paper, a density functional FP-LAPW+lo method was used to explore the structural, electronic, optical, elastic, thermoelectric and thermodynamic properties of the spinel oxides ZnRh2O4 and CdRh 2O4.
TL;DR: In this article, the authors investigate the effect of strain on the morphology and composition of GeSn layers grown on Ge/Si virtual substrates and demonstrate that the lattice parameter can be tuned to reduce the strain in the growing top layer (TL) leading to the incorporation of Sn up to 18.5% and higher.
Abstract: We investigate the effect of strain on the morphology and composition of GeSn layers grown on Ge/Si virtual substrates. By using buffer layers with controlled thickness and Sn content, we demonstrate that the lattice parameter can be tuned to reduce the strain in the growing top layer (TL) leading to the incorporation of Sn up to 18 at. %. For a 7 at. % bottom layer (BL) and a 11-13 at. % middle layer (ML), the optimal total thickness tGeSn = 250-400 nm provides a large degree of strain relaxation without apparent nucleation of dislocations in the TL, while incorporating Sn at concentrations of 15 at. % and higher. Besides facilitating the growth of Sn-rich GeSn, the engineering of the lattice parameter also suppresses the gradient in Sn content in the TL, yielding a uniform composition. We correlate the formation of the surface cross-hatch pattern with the critical thickness hG for the nucleation and gliding of misfit dislocations at the GeSn-Ge interface that originate from gliding of pre-existing threading dislocations in the substrate. When the GeSn layer thickness raises above a second critical thickness hN, multiple interactions between dislocations take place, leading to a more extended defective ML/BL, thus promoting additional strain relaxation and reduces the compositional gradient in the ML. From these studies, we infer that the growth rate and the Ge-hydride precursors seem to have a limited influence on the growth kinetics, while lowering temperature and enhancing strain relaxation are central in controlling the composition of GeSn. These results contribute to the fundamental understanding of the growth of metastable, Sn-containing group-IV semiconductors, which is crucial to improve the fabrication and design of silicon-compatible mid-infrared photonic devices.
TL;DR: In this paper, a high-entropy oxide nanocrystalline powder with chemical and microstructure homogeneity has been successfully synthesized, for the first time by a modified solution combustion synthesis method at synthesis temperature above 623
TL;DR: For cost-effective fabrication of pure and 0.8% Dy doped PbI2 thin films on FTO substrate using spin coating process, a facile microwave route (within 15'min) at 700W power was developed as discussed by the authors.
TL;DR: In this article, pure and 2% Mn, Fe and Zn doped NiO nanoparticles were synthesized by co-precipitation method at calcination temperature 550°C.
TL;DR: In this paper, the one pot synthesis of pure and Cd2+doped PbI2 (Pb2+ = 0.97 ǫ A) nanostructures by simple chemical route at room temperature was reported.
TL;DR: This Account focuses on advances in exciton-plasmon coupling and light-matter interactions with plasmonic nanoparticle lattices, and introduces the fundamentals of ultrasharp surface lattice resonances.
Abstract: Rationally assembled nanostructures exhibit distinct physical and chemical properties beyond their individual units. Developments in nanofabrication techniques have enabled the patterning of a wide range of nanomaterial designs over macroscale (>in.2) areas. Periodic metal nanostructures show long-range diffractive interactions when the lattice spacing is close to the wavelength of the incident light. The collective coupling between metal nanoparticles in a lattice introduces sharp and intense plasmonic surface lattice resonances, in contrast to the broad localized resonances from single nanoparticles. Plasmonic nanoparticle lattices exhibit strongly enhanced optical fields within the subwavelength vicinity of the nanoparticle unit cells that are 2 orders of magnitude higher than that of individual units. These intense electromagnetic fields can manipulate nanoscale processes such as photocatalysis, optical spectroscopy, nonlinear optics, and light harvesting. This Account focuses on advances in exciton-plasmon coupling and light-matter interactions with plasmonic nanoparticle lattices. First, we introduce the fundamentals of ultrasharp surface lattice resonances; these resonances arise from the coupling of the localized surface plasmons of a nanoparticle to the diffraction mode from the lattice. Second, we discuss how integrating dye molecules with plasmonic nanoparticle lattices can result in an architecture for nanoscale lasing at room temperature. The lasing emission wavelength can be tuned in real time by adjusting the refractive index environment or varying the lattice spacing. Third, we describe how manipulating either the shape of the unit cell or the lattice geometry can control the lasing emission properties. Low-symmetry plasmonic nanoparticle lattices can show polarization-dependent lasing responses, and multiscale plasmonic superlattices-finite patches of nanoparticles grouped into microscale arrays-can support multiple plasmon resonances for controlled multimodal nanolasing. Fourth, we discuss how the assembly of photoactive emitters on the nanocavity arrays behaves as a hybrid materials system with enhanced exciton-plasmon coupling. Positioning metal-organic framework materials around nanoparticles produces mixed photon modes with strongly enhanced photoluminescence at wavelengths determined by the lattice. Deterministic coupling of quantum emitters in two-dimensional materials to plasmonic lattices leads to preserved single-photon emission and reduced decay lifetimes. Finally, we highlight emerging applications of nanoparticle lattices from compact, fully reconfigurable imaging devices to solid-state emitter structures. Plasmonic nanoparticle lattices are a versatile, scalable platform for tunable flat optics, nontrivial topological photonics, and modified chemical reactivities.
TL;DR: In this article, X-ray diffraction and vibrational spectroscopy techniques were employed to study the structure, cation distribution and ordering in the Co2+ substituted nickel ferrite (NCFO) samples.
TL;DR: In this article, the superparamagnetic properties of NiSm0.1Fe1.9O4 (NSF) and NiEr 0.1 Fe1.1O4(NEF) nanomaterials were analyzed using field emission scanning electron microscope (FESEM) and transmission electron microscopes (TEM).
TL;DR: In this article, a finite element model has been developed to predict the sound transmission loss (STL) of the pyramidal lattice sandwich structure with solid trusses (PLSSST), and simulation results have been compared with those obtained experimentally.
TL;DR: In this paper, the authors obtained bulk ZnGa2O4 single crystals directly from the melt, which are characterized by a stoichiometric or near-stoichiometric composition with a normal spinel structure at room temperature and by a narrow full width at half maximum of the 400 peak of (100)-oriented samples of 23 arcsec.
Abstract: Truly bulk ZnGa2O4 single crystals were obtained directly from the melt. High melting point of 1900 ± 20 °C and highly incongruent evaporation of the Zn- and Ga-containing species impose restrictions on growth conditions. The obtained crystals are characterized by a stoichiometric or near-stoichiometric composition with a normal spinel structure at room temperature and by a narrow full width at half maximum of the rocking curve of the 400 peak of (100)-oriented samples of 23 arcsec. ZnGa2O4 is a single crystalline spinel phase with the Ga/Zn atomic ratio up to about 2.17. Melt-grown ZnGa2O4 single crystals are thermally stable up to 1100 and 700 °C when subjected to annealing for 10 h in oxidizing and reducing atmospheres, respectively. The obtained ZnGa2O4 single crystals were either electrical insulators or n-type semiconductors/degenerate semiconductors depending on growth conditions and starting material composition. The as-grown semiconducting crystals had the resistivity, free electron concentration, and maximum Hall mobility of 0.002–0.1 Ωcm, 3 × 1018–9 × 1019 cm−3, and 107 cm2 V−1 s−1, respectively. The semiconducting crystals could be switched into the electrically insulating state by annealing in the presence of oxygen at temperatures ≥700 °C for at least several hours. The optical absorption edge is steep and originates at 275 nm, followed by full transparency in the visible and near infrared spectral regions. The optical bandgap gathered from the absorption coefficient is direct with a value of about 4.6 eV, close to that of β-Ga2O3. Additionally, with a lattice constant of a = 8.3336 A, ZnGa2O4 may serve as a good lattice-matched substrate for magnetic Fe-based spinel films.
TL;DR: In this article, a sol-gel synthesis of Zn doped spinel Co1-xZnxFe2O4 (where x = 0.0, 0.1,0.2, and 0.3) was reported.
Abstract: The finely controlled nanostructured cubic spinel ferrites pave the way to synthesize nanomaterials with specific properties for particular applications. In this paper, we report sol-gel synthesis of Zn doped spinel Co1-xZnxFe2O4 (where x= 0.0, 0.1, 0.2, and 0.3) ferrite nanoparticles. X-ray diffraction confirms the single phase cubic structure of nano ferrites with average particle size estimated between 55.38 to 32.87 nm and validated by Transmission electron microscopy (TEM) results (±1). The lattice parameter was found to increase with increasing Zn doping concentration. The samples exhibit normal dielectric behaviour of Maxwell-Wagner type of interfacial polarization that decreases with increasing frequency of the applied field. Temperature-dependent magnetic properties were investigated with the aid of physical property system. The hysteresis measurements of the samples show clearly enhancement in magnetic parameters as the temperature goes down to 20 K. Tuning of magnetic properties has been witnessed as a function of doping and temperature under the influence of externally applied magnetic field, has been discussed in this paper.
TL;DR: In this article, the synthesis of pure and Cu doped lead sulfide (PbS) nanoparticles was facilely achieved, and the good crystalline nature of the nanoparticles were confirmed via X-ray diffraction (XRD) analysis.
TL;DR: The emergence of high piezoelectricity, high carrier mobility, low lattice thermal conductivity and photocatalytic water splitting abilities in the proposed vdW heterobilayer signifies enormous potential for its versatile applications in nanoscale energy harvesting, e.g., nano-sensors in medical devices, future nanopiezotronics, 2D thermoelectrics and solar energy conversion.
Abstract: A stable 2D van der Waals (vdW) heterobilayer, constituted by boron monophosphide (BP) and Gallium Nitride (GaN) monolayers, has been explored for different kinds of energy conversion and nanoelectronics. The nearly matched lattice constants of GaN and BP are commensurate with each other in their lattice structures. The out-of-plane inversion asymmetry coupled with the large difference in atomic charges between the GaN and BP monolayers induces in the heterobilayer a giant out-of-plane piezoelectric coefficient (|d33|max ≈ 40 pm V−1), which is the highest ever reported in 2D materials of a finite thickness. It is much higher than the out-of-plane piezoelectric coefficient reported earlier in multilayered Janus transition metal dichalcogenide MXY (M = Mo, W; X, Y = S, Se, Te) (|d33|max = 10.57 pm V−1). Such a high out-of-plane piezoelectricity found in a BP/GaN heterobilayer can bring about gigantic strain-tunable top gating effects in nanopiezotronic devices based on the same. Moreover, electron mobility (∼104 cm2 V−1 s−1) is much higher than that of transition metal dichalcogenides and conventional semiconductors. The origin of low lattice thermal conductivity (κL ∼ 25.25 W m−1 K−1) in BP/GaN at room temperature, which is lower than that of black phosphorene (78 W m−1 K−1), buckled arsenene (61 W m−1 K−1), BCN (90 W m−1 K−1), MoS2 (34.5 W m−1 K−1) and WS2 (32 W m−1 K−1) monolayers, has been systematically investigated via phonon dispersion, lattice thermal conductivity, phonon lifetime and mode Gruneisen parameters. The valence band maximum (VBM) and conduction band minimum (CBM) arising from GaN and BP monolayers respectively result in a type II vdW heterobilayer, which is found to be thermodynamically favorable for photocatalytic water splitting in both acidic and neutral media. The exciton binding energies are comparable to those of MoS2 and C3N4 single layers, while the absorbance reaches as high as ∼105 cm−1 in the visible wavelength region. The emergence of high piezoelectricity, high carrier mobility, low lattice thermal conductivity and photocatalytic water splitting abilities in the proposed vdW heterobilayer signifies enormous potential for its versatile applications in nanoscale energy harvesting, e.g., nano-sensors in medical devices, future nanopiezotronics, 2D thermoelectrics and solar energy conversion.
TL;DR: Highly reversible K+ extraction and insertion in the layers are achieved, with a good cycling stability of up to 200 cycles (83% of retention), and the structural evolution of this material during the electrochemical processes is explored.
TL;DR: In this paper, the effect of doping on morphological features was monitored using Field emission scanning electron microscope (FESEM) images, which confirmed the cubic spinel structure of cobalt ferrite nanoparticles.
TL;DR: In this paper, the effect of Mn doping on the properties of inorganic CsPbCl3 nanocrystals was investigated and further validated with density functional theory (DFT) calculations, which provided insight into the important properties of these semiconducting compounds such as their lattice parameter, electronic band structure, density of states, dielectric constant, absorption coefficient and refractive index.
Abstract: Wide energy gap inorganic halide perovskites have become emerging candidates for potential applications in modern optoelectronics devices. However, to date, these semiconducting compounds have not been explored theoretically to a significant extent. Herein, we performed ab initio computations to explain the structural, electronic and optical behaviour of inorganic CsPbCl3 and Mn-doped CsPbCl3 nanocrystals (NCs). We also synthesized these NCs and further validated our experimental results with density functional theory (DFT) calculations. The results provide insight into the effect of Mn doping on the important properties of CsPbCl3 NCs such as their lattice parameter, electronic band structure, density of states, dielectric constant, absorption coefficient and refractive index. After geometry optimization using the Limited-memory Broyden–Fletcher–Goldfarb–Shanno (LBFGS) algorithm, a reduction in the lattice parameter from 5.605 A to 5.574 A was observed after doping Mn in the CsPbCl3 NCs, which is in good agreement with the calculated results from the X-ray diffraction (XRD) pattern (5.610 A to 5.580 A) and high-resolution transmission electron microscopy (HRTEM) images (5.603 A to 5.575 A). The incorporation of Mn in CsPbCl3 was observed in the electronic band structure in the form of additional states present in the energy gap and an increment in the band gap of the CsPbCl3 NCs. This result is consistent with the photoluminescence (PL) plot, which showed dual color emission in the case of the Mn-doped CsPbCl3, which is attributed to the Mn2+ d-band to d-band transition. The partial density of states (PDOS) of the Mn-doped CsPbCl3 NCs clearly indicates the contribution of the Mn 3d orbitals to the upper valence band and conduction band together with the contribution of the Pb 6p and Cl 3p orbitals. Moreover, a blue-shift phenomenon was observed from the dielectric constant and absorption coefficient spectra, which is due to the incorporation of Mn in CsPbCl3. Also, a significant peak was observed in the absorption coefficient and dielectric constant spectra around 2.08 eV, which is in good agreement with the PL plot. This DFT study with experimental observation provides a way to investigate this type of compound and to tailor its interesting characteristics through doping.
TL;DR: In this article, the formation of single phase cubic spinel with crystallite sizes in the range of 30-42nm was characterized by X-ray diffraction (XRD), Mossbauer Spectroscopy (MS), and Vibrating Sample Magnetometer (VSM).