Dependence Of Structural Properties Research Articles

Thickness dependent structural and electrical properties of pulsed laser deposited Y0.95Ca0.05MnO3 thin films and the effect of high energy oxygen ion irradiation

Thickness dependent structural and electrical properties of pulsed laser deposited Y0.95Ca0.05MnO3 thin films and the effect of high energy oxygen ion irradiation

Bilayer period and ratio dependent structure and mechanical properties of TiN/MoN superlattices

Transition metal nitrides are widely used in the hard materials and protective coatings industry, but are limited by their low fracture toughness. Encouraged by previous studies on remarkable simultaneous improvements in strength and ductility through superlattice (SL) architectures, various TiN/MoN SL thin films were developed on MgO (100) substrates. By varying their bilayer periods (Λ) between 2 and 23 nm with bilayer ratios (Γ = ℓMoN:ℓTiN) of 0.5, 1, 2, and 2.7, their individual effects on structure and mechanical properties can be revealed. All SLs—independent of Λ, Γ, and nitrogen-to-metal (N/Me) ratio (within the analysed variations)—exhibit a rocksalt structure with high-order satellite peaks in X-ray diffraction. While the SLs with Γ = 2 have the lowest hardness (H)—presumably due to their overall lowest N/Me ratio—the SLs with Γ = 2.7 are the hardest with a neat superlattice effect. The SLs with Γ = 1 and 2.7 have a comparable superlattice effect on fracture toughness (KIC), peaking at Λ = 9.9 and 9.3 nm, respectively. Of all the SLs investigated, those with Γ = 1 provide the best blend of mechanical properties and dry sliding coefficient of friction (µ), such as H = 34.8±1.6 GPa, KIC = 4.1±0.2 MPa√m, and µ = 0.27 when Λ = 9.9 nm. Deepening current understanding of superlattice effects in general—particularly the influence of bilayer periods and ratios—in relation to the nitrogen supply and heterogeneous microstructures, our study accelerates the design of nanolayered coatings with desired structure-property combinations.

(Invited) Quantitative in Vitro/In Vivo Fluorescence Bioimaging with Graphene Quantum Dots

Graphene Quantum Dots (GQDs) are novel carbon nanomaterials consisting of few layers of partially functionalized graphitic carbon. Their nanometer-scale size together with functional groups render GQDs more water soluble and biocompatible than many other nanocarbon constructs. Like many nanocarbons, GQDs possess structure-dependent optical properties, exhibiting confinement-defined fluorescence in the visible and defect-originated emission in the near-infrared (NIR). These properties give GQDs a certain advantage for applications in therapeutic tracking, imaging, analyte detection and targeted drug/gene delivery. In addition to tracing the location of therapeutic or analyte, GOD fluorescence allows for several modes of quantitative assessment within these applications. In vitro it is utilized to evaluate relative amounts of therapeutics or analytes present within the cells at a certain time period. In vivo NIR emission of the GQDs-based sensors implanted under the skin can help detect trace quantities of analyte in the body, while their NIR fluorescence in animal organs can quantify relative therapeutic uptake over time.The present work introduces novel studies and analytical tools exploring and enhancing such imaging modalities. Although GQD in vitro fluorescence microscopy imaging is often used to quantitate their (and payload) uptake and excretion, this method suffers from multiple discrepancies including the analysis of dead cells, cellular debris and non-internalized nanomaterials, and can be also time and resource-consuming. Our work aiming to circumvent these issues utilizes Artificial Intelligence (AI) approach to provide more accurate quantification of the uptake/excretion of the GQDs and their payload. In this application the AI algorithms developed in house do not only optimize the imaging, but also provide automated image analysis streamlining the assessment of a variety of GQD biomedical applications including therapeutic delivery and targeting. In vivo quantitative animal imaging with several different types of GQDs, from pristine to doped with rare earth metals for NIR fluorescence enhancement, is performed to evaluate GQD organ accumulation over time. Defect or dopant-originated NIR GQD fluorescence in the range of 900 – 1060 nm due to its high penetration depth can be observed from the organs of sedated live mice and utilized for GQD uptake tracking. NIR imaging of the excised organs allows for quantitative biodistribution assessment with further microscopic confirmation of the GQD content in organ tissue slices. Quantitative optical imaging and analysis presented in this work for GQDs can aid the further advancement of these novel nanomaterials in therapeutic delivery and analyte detection applications in vitro and in vivo.

Rational Design of Highly Phosphorescent Nanoclusters for Efficient Photocatalytic Oxidation.

Analyzing the molecular structure-photophysical property correlations of metal nanoclusters to accomplish function-oriented photocatalysis could be challenging. Here, the selective heteroatom alloying has been exploited to a Au15 nanocluster, making up a structure-correlated nanocluster series, including homogold Au15, bimetallic AgxAu15-x and CuxAu15-x, trimetallic AgxCuyAu15-x-y, and tetrametallic Pt1AgxCuyAu15-x-y. Their structure-dependent photophysical properties were investigated due to the atomically precise structures of these nanoclusters. Cu-alloyed CuxAu15-x showed intense phosphorescence and the highest singlet oxygen production efficiency. Moreover, the generation of 1O2 species from excited nanoclusters enabled CuxAu15-x as a suitable catalyst for efficient photocatalytic oxidation of silyl enol ethers to produce α,β-unsaturated carbonyl compounds. The generality and applicability of the CuxAu15-x catalysts toward different photocatalytic oxidations were assessed. Overall, this study presents an intriguing Au15-based cluster series enabling an atomic-level understanding of structure-photophysical property correlations, which hopefully provides guidance for the fabrication of cluster-based catalysts with customized photocatalytic performance.

Study of the microstructure of asphalt concrete using X-ray computed tomography

A mechanical digital twin (a mechanical finite-element model) of an asphalt concrete sample has been developed in the framework of a project for recycling polymer composite materials with fibrous reinforcement (fiberglass) as an alternative for crushed stone in the asphalt concrete production. A methodology of using X-ray computed tomography (XCT) for analysis of the asphalt concrete microstructure and calculation of the mechanical properties is developed. The data processing chain for developing a digital twin of the asphalt concrete microstructure, based on X-ray micro-computed tomography (XCT) image includes the following steps: 1) image enhancement; 2) image segmentation; 3) analysis of the morphology of pores and solid particles; 4) transformation of the segmented image into a voxels-based finite element (FE) model. It is demonstrated that the XCT resolution of 40 μm is sufficient for a reliable identification of microstructural parameters, i.e., volume fractions of the components, distributions of voids (pores) in size, shape and spatial position, as well as distributions of the crushed brittle additives (fiberglass chips) in size. The FE model constitutes a digital twin of the material, and, after specifying the characteristics of the material components, can be used for simulation of the thermomechanical and functional properties of the material. The developed procedure is exemplified in the calculation of statistics of the compression and shear moduli of the asphalt concrete with addition of crushed fiberglass particles. The dependence of the calculated elastic properties on the size of the digital twin is studied. It is shown that a model size of 10 mm and more is sufficient for the microstructural representativity and calculation of the homogenization characteristics. The results can be used for analysis of the microstructure and structure-dependent thermomechanical properties of asphalt concrete. The developed finite element model can be used for modelling of the visco-elastic response of asphalt concrete and its behavior under cyclic loading.

Unraveling the orientation-dependent mechanics of dental enamel in the red-necked wallaby

Dental enamels of different species exhibit a wide variety of microstructural patterns that are attractive to mimic in bioinspired composites to simultaneously achieve high stiffness and superior toughness. Non-human enamel types, however, have not yet received the deserved attention and their mechanical behaviour is largely unknown. Using nanoindentation tests and finite element modelling, we investigate the mechanical behaviour of Macropus rufogriseus enamel, revealing a dominating influence of the microstructure on the effective mechanical behaviour and allowing insight into structural dependencies. We find a shallow gradient in stiffness and low degree of anisotropy over the enamel thickness that is attributed to the orientation and size of microstructural features. Most notably, M. rufogriseus’s modified radial enamel has a far simpler structural pattern than other species’, but achieves great property amplification. It is therefore a very promising template for biomimetic design. Statement of significanceThe diversity of dental enamel structures in different species is well documented, but the mechanical behaviour of non-human enamel types is largely unknown. In this work, we investigate the microstructure and structure-dependent mechanical properties of marsupial enamel by nanoindentation and finite element simulations. Combining these methods gives valuable insights into the performance of modified radial enamel structures. Their stiffness and toughness stems from a unique structural design that is far less complex than well-studied human enamel types, which makes it a uniquely suitable template for biomimetic design.

Systematic exploration of structure-property relationships in colorless polyimides derived from stereoisomeric dianhydrides and various diamines

This study explores the structure-property relationships in colorless polyimides (CPIs) synthesized from stereoisomeric (exo- and endo-form) alicyclic dianhydrides, combined with various diamines. The structural configurations of 5,5’-(1,4-phenylene)bis[hexahydro-(3aR,4R,5R,7S,7aS)-rel-4,7-Methanoisobenzofuran-1,3-dione] (BzDA-exo) and 5,5-(1,4-phenylene)bis(hexahydro-4,7-methanoisobenzofuran-1,3-dione) (BzDA-endo) were confirmed as exo- and endo-forms, respectively, through 1H NMR and 2D NOESY NMR analyses. Wide-angle X-ray scattering (WAXS) data revealed that stereoisomeric structures influence polymer chain packing in synthesized CPIs. The investigation extended to the chemical and physical structure-dependent properties such as physical, thermal and optical properties of the PIs. Notably, structure-dependent physical and thermal properties were evident, with a particularly strong structure-property relationship manifesting in the coloration and yellow index (Y.I.) of PIs. These systematic characterizations offer profound insights into the design and optimization of chemical and physical structures in CPIs, highlighting the versatility of stereoisomeric monomers for various applications.

Symmetry-breaking-induced off-resonance second-harmonic generation enhancement in asymmetric plasmonic nanoparticle dimers

Abstract The linear and nonlinear optical properties of metallic nanoparticles have attracted considerable experimental and theoretical research interest. To date, most researchers have focused primarily on exploiting their plasmon excitation enhanced near-field and far-field responses and related applications in sensing, imaging, energy harvesting, conversion, and storage. Among numerous plasmonic structures, nanoparticle dimers, being a structurally simple and easy-to-prepare system, hold significant importance in the field of nanoplasmonics. In highly symmetric plasmonic nanostructures, although the odd-order optical nonlinearity of the near-surface region will be improved because of the enhanced near-fields, even-order nonlinear processes such as second-harmonic generation (SHG) will still be quenched and thus optically forbidden. Under this premise, it is imperative to introduce structural symmetry breaking to realize plasmon-enhanced even-order optical nonlinearity. Here, we fabricate a series of nanoparticle dimers each composed of two gold nanospheres with different diameters and subsequently investigate their structural asymmetry dependent linear and nonlinear optical properties. We find that the SHG intensities of gold nanosphere dimers are significantly enhanced by structural asymmetry under off-resonance excitation while the plasmonic near-field enhancement mainly affects SHG under on-resonance excitation. Our results reveal that symmetry breaking will play an indispensable role when designing novel coupled plasmonic nanostructures with enhanced nonlinear optical properties.

Delineating Dy3+ and Sm3+ in thermally stable strontium silicate apatites for multifunctional applications

The structural, optical and temperature dependent luminescence properties of a series of Sr2Y8-xREx(SiO4)6O2 (RE=Dy and Sm) silicate phosphors are investigated for their multifunctional applications. The phosphors were synthesized using the solid-state reaction route with varying doping levels and characterized for phase purity. X-ray Diffraction analysis revealed the hexagonal crystal structure of (Sr2RE2)(RE6)(SiO4)6O2, indicating the incorporation of rare earth (RE) ions into two distinct crystallographic sites, thereby augmenting the luminescence properties. Dy3+ doped compounds exhibit intense yellow emission, promising white light generation when paired with InGaN blue LED chips. Sm3+ doped samples show orange-red emission around 601 nm, attributed to multipole-multipole interactions, with rapid decay curves suitable for high-speed response LEDs. Correlated Color Temperature (CCT) values were computed to assess the commercial viability of these phosphors in luminescence applications and the role of lighting in the growth of indoor plants and office spaces is discussed. The Sr2Y7.8Dy0.2(SiO4)6O2 phosphor with remarkable quantum yield of 63.56% demonstrated a thermal stability of 0.27 eV with enhanced sensitivity of about 0.39% K−1 and Sr2Y7.8Sm0.2(SiO4)6O2 with stability around 0.31eV with sensitivity of 1.11% K⁻¹ at 100K reveals them as potential candidates for optical temperature sensing. These results declare the competence of synthesized novel silicate apatites in solid-state lighting and optical thermometry.

Mg-Composition Dependent Cycle Stability in Zn<sub>1-x</sub>Mg<sub>x</sub>O Li-ion Battery: Transition from Electronic Transport-Limited to Ionic Transport Limited Cycles

This study explores Mg-composition dependent cycle stability in a Zn<sub>1-x</sub>Mg<sub>x</sub>O Li-ion battery, where battery cycles transition from an electronic transport-limited to an ionic transport limited regime. We investigated the impact of Mg doping in Zn<sub>1-x</sub>Mg<sub>x</sub>O nanocrystals on Li-ion battery performance, focusing on Mg compositions between x=0.05 and x=0.15. Mg composition dependent structural and electrical properties were explored using field effect transistors (FETs) and various microscopic/spectroscopic methods. The electronic conductivity was found to be sensitive to changes in Mg composition. Consistently, the initial capacity decreased with an increase in Mg composition, aligning with the reduction in electronic conductivity due to Mg doping. However, with successive cycles, the capacity became independent of the electronic conductivity, an outcome attributed to the formation of a solid-electrolyte interphase (SEI) and the conversion reactions. Initially, Mg doping reduces electronic conductivity due to increased carrier trapping, leading to lower discharge capacity. However, as cycling progresses, the impact of Mg doping diminishes. The formation of the SEI layer becomes more influential, significantly affecting Li-ion transport. Over time, factors like SEI formation, conversion reaction dynamics, and structural changes within the electrode start to dominate the battery's capacity, rather than the initial electronic conductivity influenced by Mg doping. This understanding can guide the development of materials with lower resistance, facilitating faster charging and discharging rates. More importantly, this study indicates that the initial capacity is closely tied to the conductivity of the Zn<sub>1-x</sub>Mg<sub>x</sub>O material.

3D porosity, flow, and transport characteristics of two L chondrites reveal wet accretion-related cosmic web-like porosity

Porosity, with its structure-dependent flow properties (permeability and tortuosity) and transport properties (thermal conductivity and thermal diffusivity), is closely related to the accretion, thermal metamorphism, and associated hydrothermal alteration of ordinary chondrite (OC) parent bodies. Using synchrotron radiation microtomography (SRμCT), we reveal the varying porosity structures in two L chondrite falls of low (Mezö-Madaras L3.7) and high (Bath Furnace L6) petrologic types and quantify porosity properties, such as shape and connectivity, and related effective permeability and tortuosity factor. Although the two specimens demonstrate similar effective permeabilities, they exhibit significantly different tortuosity factors and textures of porosity, which include notable differences in void throat diameters, complexity and density of the interconnected void network, heterogeneity in void distribution, and the extent of primary and secondary porosity. The complex relationships among porosity, permeability, tortuosity, and thermal conductivity can be explained by the varying void arrangements related to varying grain sizes among the petrologic types of OCs, which in turn reflect their varying evolutionary paths.Electron microprobe and attached energy-dispersive X-ray spectrometer reveal signs of hydrothermal alteration in both petrologic types. High-energy SRμCT imaging (0.65 μm voxel size) reveals the presence of a new microporosity substructure resembling a microscopic cosmic web, which may be linked to fluid-assisted metamorphism and hydrothermal alteration during wet accretion of the parent body. Furthermore, the proportion of this continuous porosity may be related to the temperatures associated with different petrologic types, and the wet accretion model may resolve the lack of correlation between petrologic types and porosity of OCs. Finally, the uncovered cosmic web-like microporosity structure may explain the observed concurrent high thermal conductivity, low permeability, and high porosity of the high-petrologic-type OCs.

Rietveld refined structural and sintering temperature dependent electromagnetic properties of Al3+ substituted Ni–Co ferrites prepared through sol–gel auto combustion method for high-frequency and microwave devices

Rietveld refined structural and sintering temperature dependent electromagnetic properties of Al3+ substituted Ni–Co ferrites prepared through sol–gel auto combustion method for high-frequency and microwave devices

Tunable 2D Conjugated Porous Organic Polymer Films for Precise Molecular Nanofiltration and Optoelectronics.

Structural design of 2D conjugated porous organic polymer films (2D CPOPs), by tuning linkage chemistries and pore sizes, provides great adaptability for various applications, including membrane separation. Here, four free-standing 2D CPOP films of imine- or hydrazone-linked polymers (ILP/HLP) in combination with benzene (B-ILP/HLP) and triphenylbenzene (TPB-ILP/HLP) aromatic cores are synthesized. The anisotropic disordered films, composed of polymeric layered structures, can be exfoliated into ultrathin 2D-nanosheets with layer-dependent electrical properties. The bulk CPOP films exhibit structure-dependent optical properties, triboelectric nanogenerator output, and robust mechanical properties, rivaling previously reported 2D polymers and porous materials. The exfoliation energies of the 2D CPOPs and their mechanical behavior at the molecular level are investigated using density function theory (DFT) and molecular dynamics (MD) simulations, respectively. Exploiting the structural tunability, the comparative organic solvent nanofiltration (OSN) performance of six membranes having different pore sizes and linkages to yield valuable trends in molecular weight selectivity is investigated. Interestingly, the OSN performances follow the predicted transport modeling values based on theoretical pore size calculations, signifying the existence of permanent porosity in these materials. The membranes exhibit excellent stability in organic solvents at high pressures devoid of any structural deformations, revealing their potential in practical OSN applications.

Aggregation induced strong photoluminescence at room temperature in large-area C8BTBT thin films

Study of optical properties of 2,7-dioctyl[1]benzothieno[2,3-b]benzothiophene (C8BTBT) is promising for applications in low-cost and flexible optoelectronic devices. Here, we systematically investigated the thickness dependent structural and photophysical properties of large-area C8BTBT films. The large-area C8BTBT thin films of different thickness below 80 nm were prepared by off-centre spin coating method. Grazing incidence X-ray diffraction measurements confirm the highly crystalline nature of the thin films and reveal that crystal coherence length increases with increase of film thickness. The film morphology and its thickness were studied using atomic force microscopy. Further, optical absorption and emission behaviors of the thin films were analyzed. The results show strong ultraviolet (UV) emissions at room temperature. The photoluminescence behaviour of higher-thickness films differs from that of lower-thickness films. The thickness dependent UV emission spectra are explained in terms of defects and aggregation behavior of C8BTBT thin films. We determine the impact of thickness and aggregation (J- and H-type) on emission behaviors of the C8BTBT thin films. Our findings open a new avenue for the future optimization and prospective applications in photonics based on two-dimensional organic semiconductors.

A review on ZnO and its modifications for photocatalytic degradation of prominent textile effluents: Synthesis, mechanisms, and future directions

Effective and eco-friendly approaches are essential for dealing with organic pollutants in industrial waste. Textile dyes are toxic and carcinogenic, and releasing them into the environment leads to water pollution, posing significant health risks to all living beings and endangering aquatic life. The use of semiconducting metal oxides for photocatalytic pollutant degradation has emerged as an advanced wastewater treatment strategy. The multifunctional nature of ZnO, stemming from its affordability, environmentally friendly characteristics, structure-dependent properties, and ability to fully mineralize pollutants, positions it as a superior photocatalyst compared to other materials. However, its primary drawback is poor performance in visible light. This review delves into various synthesis techniques and their effects on morphology, structure, and band gap, and its subsequent influence on the photocatalytic performance. The review highlights the effect of doping ZnO with various alkaline earth metals, transition metals, noble metals, rare earth metals, and non-metals, along with studies reported on ZnO-metal oxide nanocomposites for photocatalytic dye degradation, by providing insights into the photodegradation mechanism involved. Furthermore, this review extensively investigates the strategies to improve ZnO's efficiency in degrading textile dyes, namely cationic and anionic dyes, under visible light conditions. For thorough understanding, the influence of various operational parameters such as catalyst loading, irradiation source, dye concentration, reaction time, and reaction kinetics on photocatalytic efficiency have been investigated in detail. The review also addresses existing challenges and potential future directions, providing some insights for possible development in this field.

Insight on Cu-doping dependent structural, electronic and optical properties of AgZnF3 Fluro-perovskite for solar cell applications: A DFT study

The density function theory (DFT) with GGA and PBE was employed to determine the structural, electrical, and optical characteristics of pure and Cu doped AgZnF3 type Fluro-perovskite. The structural properties of composite are calculated in realistic agreement with those testified in the literature. The band gap of the hybrid AgZnF3 is small and indirect. AgZnF3 contained a calculated band width of 1.52 eV. AgZnF3's total electronic properties were principally controlled by the Zn atom, whereas the Zn-d state and the F-p state had a minor impact on its partial electronic properties and state density. Cu doping modified AgZnF3's electrical band structure by narrowing the band gap. With increasing doping concentrations, the partial densities of states, which are likewise impacted by doping concentrations decreased. This material is appropriate for a variety of applications due to the improvement in optical characteristics and decrease in the band gap.

Dichotomous effect of dietary fiber in pediatrics: a narrative review of the health benefits and tolerance of fiber.

Dietary fibers are associated with favorable gastrointestinal, immune, and metabolic health outcomes when consumed at sufficient levels. Despite the well-described benefits of dietary fibers, children and adolescents continue to fall short of daily recommended levels. This gap in fiber intake (i.e., "fiber gap") might increase the risk of developing early-onset pediatric obesity and obesity-related comorbidities such as type 2 diabetes mellitus into adulthood. The structure-dependent physicochemical properties of dietary fiber are diverse. Differences in solubility, viscosity, water-holding capacity, binding capability, bulking effect, and fermentability influence the physiological effects of dietary fibers that aid in regulating appetite, glycemic and lipidemic responses, and inflammation. Of growing interest is the fermentation of fibers by the gut microbiota, which yields both beneficial and less favorable end-products such as short-chain fatty acids (e.g., acetate, propionate, and butyrate) that impart metabolic and immunomodulatory properties, and gases (e.g., hydrogen, carbon dioxide, and methane) that cause gastrointestinal symptoms, respectively. This narrative review summarizes (1) the implications of fibers on the gut microbiota and the pathophysiology of pediatric obesity, (2) some factors that potentially contribute to the fiber gap with an emphasis on undesirable gastrointestinal symptoms, (3) some methods to alleviate fiber-induced symptoms, and (4) the therapeutic potential of whole foods and commonly marketed fiber supplements for improved health in pediatric obesity.

Hydrogen-bonded organic framework derived ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production

The introduction of metal complex units makes it possible to expand the functional applications of metal hydrogen-bonded organic frameworks (M-HOFs). An M-HOFs-templated strategy was developed to construct ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production. Due to the weak and feasible hydrogen-bonding interactions, the nonmetallic units on HOFs can be quickly replaced by S2− in aqueous solution and derived into porous sulfides without pyrolysis process. Surprisingly, the surface area of ZnCdS/ZnS heterojunction was up to 320 m2 g−1. The ultra-fine heterojunction with high porosity offered more surface reaction sites and shortened carrier transport distance, improving separation efficiency of photogenerated electrons and holes. The size and structure-dependent properties of ZnCdS/ZnS heterojunction exhibited excellent photocatalytic hydrogen evolution rate, which was 1.68 mmol h−1 without cocatalyst. This study provides a novel strategy for constructing ultra-fine heterojunction with high porosity and high surface area to achieve efficient H2 evolution.

Thickness dependent structural, morphological, and magnetic properties of PLD grown CoFe thin film

The objective of the present investigation is to optimize the thickness of Pulse Laser Deposition (PLD)-grown CoFe thin films to achieve minimal effective Gilbert damping (αeff) for potential spintronics applications. The effect of the thickness (5-30 nm) of CoFe ultra-thin films on the Si/SiO2 substrate on the structural, morphological and magnetic properties has been reported. The X-ray diffraction (XRD) peak at 44.5° shows the growth of CoFe along the (110) crystal plane. A nearly square M-H loop with high saturation magnetization (Ms) suggests good crystalline growth of CoFe film. A high coercive field (Hc) observed in the thinnest 5 nm film is due to defects such as dislocations and stacking faults that appear at very low thickness. These defects gradually decrease with an increase in CoFe film thickness, as evident from a decrease in the Hc and an increase in the Ms. The value of αeff is largest for the thinnest 5 nm film due to defects and magnetic inhomogeneities present at this thickness. The damping is reduced by approximately one-third for the 10 nm thin film in comparison to the 5 nm film, which signifies a good quality film with fewer disorders.

Strain dependent electronic structure, phonon and thermoelectric properties of CuLiX (X=S,Te) half Heusler compounds

We report the strain dependent electronic, phonon and thermoelectric properties of Li-based Half-Heusler compounds. A direct bandgap of 1.50 eV (for CuLiS) and 1.03 eV (for CuLiTe) is observed from HSE calculations. CuLiX (X = S,Te) in their conventional structure are mechanically and dynamically stable semiconductors. However, the compression beyond −15 % (for CuLiS) and −10 % (for CuLiTe) destabilizes the crystal structure due to the overlapping of atomic charge spheres. At the same time, expansion above 4 % produces instability in both systems. The maximum value of Seebeck coefficient significantly increases from ∼1500 μ/VK in both alloys ∼2400 μ/VK in CuLiS and ∼2000 μ/VK in CuLiTe after the application of 5 % compressive strain at 300 K. These alloys achieve maximized thermoelectric efficiency via strain engineering, and thus require further experimental research.