Gap Characteristics Research Articles

Coexistence of doping and strain to tune electronic and optical properties of monolayer graphene

We performed first-principles calculations to study the structural, electronic and optical properties of monolayers graphene through strain and Al atoms doping with different concentrations. The results show that band gap of pristine graphene and graphene doped with 3.at% of Al consistently increases with strain, whereas the band gap of graphene doped with 6 at%, 9 at%, and 12 at% of Al initially increases and subsequently decreases as strain is introduced, and the band gap characteristics change from direct to indirect.Notably, a flat band phenomenon was found when the strain of 6.at%Al doped graphene reached 10 %. Furthermore, the study of optical properties reveals that the increase of Al doping concentration leads to a redshift of the peak in the imaginary part of the dielectric constant of graphene. This not only reduces reflectance to ultraviolet light but also enhances absorption of visible light while decreasing transmittance within the infrared and visible light ranges. Additionally, strain further induces a redshift in the imaginary part of the dielectric constant of Al-doped graphene.

Low-frequency band gap design of acoustic metamaterial based on cochlear structure

In this paper, a new chiral spiral structure based on the cochlear structure is proposed. The chiral spiral structure consists of four orthogonally oriented cochlear structures with the same geometric parameters connected at the inner endpoints of the four cochlear structures. Based on the Bloch’s theory and finite element method, the band gap characteristics of the proposed chiral spiral structure are studied. The effects of ligament bending angle (θ), the ratio of arc radius of cochlear contour (α), the ligament thickness (tc ), and the level of the chiral spiral structure (n) on the chiral spiral structure are discussed. The results show that the two-level chiral spiral structure (n= 2) has the best band gap characteristics when θ = 180° and α = 0.45. With the decrease of tc and the increase of n, the opening frequency of the first band gap gradually decreases. When n = 22, the chiral spiral structure has the lowest opening frequency, 1.91 Hz. The existence of the band gap is verified through the low amplitude elastic wave transmission tests. The distribution of the iso-frequency lines indicates that with the increase n, the propagation of elastic waves of the chiral spiral structure shows more distinct directivity, which provides a basis for the propagation control of elastic waves. These findings can provide new design ideas and directions for low-frequency vibration and noise control.

Effect of Data and Gap Characteristics on the Nonlinear Calculation of Motion During Locomotor Activities.

This study investigated how data series length and gaps in human kinematic data impact the accuracy of Lyapunov exponents (LyE) calculations with and without cubic spline interpolation. Kinematic time series were manipulated to create various data series lengths (28% and 100% of original) and gap durations (0.05-0.20s). Longer gaps generally resulted in significantly higher LyE% error values in each plane in noninterpolated data. During cubic spline interpolation, only the 0.20-second gap in frontal plane data resulted in a significantly higher LyE% error. Data series length did not significantly affect LyE% error in noninterpolated data. During cubic spline interpolation, sagittal plane LyE% errors were significantly higher at shorter versus longer data series lengths. These findings suggest that not interpolating gaps in data could lead to erroneously high LyE values and mischaracterization of movement variability. When applying cubic spline, a long gap length (0.20s) in the frontal plane or a short sagittal plane data series length (1000 data points) could also lead to erroneously high LyE values and mischaracterization of movement variability. These insights emphasize the necessity of detailed reporting on gap durations, data series lengths, and interpolation techniques when characterizing human movement variability using LyE values.

Influence of PEG content on optical band gap and laser damage characteristics of porous films

Influence of PEG content on optical band gap and laser damage characteristics of porous films

Tunable photoelectric properties of monolayer Mo1-x W x Te2 alloys: a first-principles study.

Monolayer MoTe2 and WTe2 within the two-dimensional transition metal dichalcogenides (TMDCs) material family exhibit broad potential for application in optoelectronic devices owing to their direct band gap characteristics. In this work, upon alloying these materials into a monolayer system denoted as Mo1-x W x Te2, intriguing alterations are observed in the electronic and optoelectronic properties. The photoelectric attributes of these alloys can be tailored by manipulating the respective ratios of molybdenum to tungsten (Mo/W). This investigation employs first-principles calculations based on density functional theory (DFT) to assess physical traits of two-dimensional monolayered structures composed from varying compositions of Mo1-x W x Te2. Our findings reveal that while maintaining a direct band gap characteristic across all compositions studied, there is also a reduction observed in electron effective mass near the Fermi level. Moreover, changing in the Mo/W ratio allows gradual adjustments in electronic properties such as density of states (DOS), work function, dielectric function, absorptivity, and reflectivity. Phonon dispersion curves further demonstrate the stability of Mo1-x W x Te2 systems. Notably, Mo0.5W0.5Te2 exhibits lower polarizability and reduced band gap when compared against MoTe2 and WTe2 counterparts. This research underscores how alloying processes enable customizable modifications in the electronic and optoelectronic properties of Mo1-x W x Te2 monolayer materials which is essential for enhancing nanoscale electronic and optoelectronic device design.

On the treatment of connecting conditions and the choice of admissible functions in energy method to investigate band gap characteristics of periodic beams

On the treatment of connecting conditions and the choice of admissible functions in energy method to investigate band gap characteristics of periodic beams

Multicolor vision perception of flexible optoelectronic synapse with high sensitivity for skin sunburn warning.

The development of flexible synaptic devices with multicolor signal response is important to exploit advanced artificial visual perception systems. The Sn vacancy-dominant memory and narrow gap characteristics of PEA2SnI4 make it suitable as a functional layer in ultraviolet-visible (UV-Vis) light-stimulated synaptic devices. However, such device tends to have high dark current and poor sensitivity, which is not conducive to subsequent information processing. Here, we proposed a self-powered flexible optoelectronic synapse based on PEA2SnI4 films. By introducing the electron transport layer (ETL), the dark current of the device is decreased by 5 orders of magnitude as compared to the Au/PEA2SnI4/ITO device, and the sensitivity is increased from 10.3% to 99.2% at 1.25 mW cm-2 light illumination (520 nm), indicating the vital role of the introduced ETL in promoting the separation of excitons in the interface and inhibiting the free carrier transfer. On this basis, the optoelectronic synaptic functions with integrated sensing, recognition, and memory features were realized. The array device exhibits UV-Vis light sensitivity and tunable synaptic plasticity, enabling its application for multicolor visual sensing and skin sunburn warning. This work provides an effective strategy for fabricating multicolor intelligent sensors and artificial vision systems, which facilitate the practical application of artificial optoelectronic synapses.

Investigation of the relationship between the structural and material composition and band gap characteristics of periodic metal composite beams

Investigation of the relationship between the structural and material composition and band gap characteristics of periodic metal composite beams

Temperature dependent color variations and photophysical properties of UV/IR shielding lanthanum titanate perovskite and its binary composite colorants

A2B2O7 type perovskite systems have found widespread use in various applications, owing to their exceptional thermal stabilities and adaptable lattice structure. La2Ti2O7 is one of the most studied system for optoelectronic and energy storage applications. The current work focuses on exploring the potential of La2Ti2O7 for developing ceramic colorants with near-infrared (NIR) reflective properties, ideal for energy-saving applications. Initially, co-precipitated La2Ti2O7 was calcined at different temperatures (600, 800 and 1000 °C) to realize the formation of phase pure perovskite structure. Further the composite ceramic colorants of La2Ti2O7 and Fe3O4 were developed via solid-state route at 600, 800 and 1000 °C. The phase purity and crystallinity of La2Ti2O7 and composite colorants were ascertained by the XRD analysis. The particle and chemical nature of the colorants were further characterized by SEM, TEM and XPS analysis. To comprehend the potential uses of these materials in different optoelectronic sectors, their tuneable optical band gap characteristics were determined. The NIR reflectance range of the synthesised La2Ti2O7 was found to be between 92 and 96 %, whilst the composite colorants showed values between 85 and 93 %. The influence of iron oxide doping and calcination temperature on the colour variations and photophysical characteristics of ceramic composite colorants have received special focus in this study.

Band gap tunability and wave propagation of a novel fully symmetric single-phase metamaterial

In this paper, a new type of fully symmetric single-phase metamaterial structure is proposed. Based on the finite element method, the band gap characteristics of different forms of the structure and the generation principle of the band gap are discussed. The analysis of the formation mechanism of the band gap shows that the proposed structure can achieve the purpose of expanding the band gap in the low frequency range by changing the structure and adding inclusions. Then, the variation trend of the band gap frequency range in the case of small deformation of the proposed structure is discussed. In addition, the propagation characteristics of elastic waves in the proposed structure are analyzed according to the variation characteristics of frequency contours, phase velocities and group velocities. Finally, the frequency response spectrum obtained from the propagation of elastic waves in a finite lattice composed of Model No. 3 elements further confirms the role of the proposed structure in suppressing wave propagation. The results show that the proposed structure has good band gap characteristics in a certain frequency range, which can provide ideological guidance for the design of metamaterials for achieve low-frequency sound insulation and vibration reduction.

Study on acoustic performance of new spiral sound absorbing and insulating metamaterial

Middle and low frequency band sound waves have strong penetration and diffraction abilities during the propagation process, making it difficult to attenuate. The control of middle and low frequency broadband sound waves has become a challenging topic. Therefore, it is necessary to develop new materials or structures with middle and low frequency sound absorption, insulation, and noise reduction functions. The special properties of acoustic metamaterial provide new ideas for the development of sound absorption and insulation. In order to effectively control the noise in the lower frequency band, a new spatial spiral acoustic metamaterial was designed. First, the mechanism of band gap characteristics of a new spatial spiral acoustic metamaterial is analyzed. Then, a new spatial spiral acoustic metamaterial is completed through the finite element software COMSOL Multiphysics and the calculation and analysis of sound absorption and insulation performance in the 100–2500 Hz frequency band are completed. With the help of 3D printing, the preparation of metamaterial is completed, and the comparative experimental study of sound absorption and insulation performance of spiral acoustic metamaterial is carried out to verify the accuracy of the calculation method.

Synthesis and Optical Properties of One Year Air-Stable Chiral Sb(III) Halide Semiconductors.

Chiral hybrid metal-halide semiconductors (MHS) pose as ideal candidates for spintronic applications owing to their strong spin-orbit coupling (SOC), and long spin relaxation times. Shedding light on the underlying structure-property relationships is of paramount importance for the targeted synthesis of materials with an optimum performance. Herein, we report the synthesis and optical properties of 1D chiral (R-/S-THBTD)SbBr5 (THBTD = 4,5,6,7-tetrahydro-benzothiazole-2,6-diamine) semiconductors using a multifunctional ligand as a countercation and a structure directing agent. (R-/S-THBTD)SbBr5 feature direct and indirect band gap characteristics, exhibiting photoluminescence (PL) light emission at RT that is accompanied by a lifetime of a few ns. Circular dichroism (CD), second harmonic generation (SHG), and piezoresponse force microscopy (PFM) studies validate the chiral nature of the synthesized materials. Density functional theory (DFT) calculations revealed a Rashba/Dresselhaus (R/D) spin splitting, supported by an energy splitting (ER) of 23 and 25 meV, and a Rashba parameter (αR) of 0.23 and 0.32 eV·Å for the R and S analogs, respectively. These values are comparable to those of the 3D and 2D perovskite materials. Notably, (S-THBTD)SbBr5 has been air-stable for a year, a record performance among chiral lead-free MHS. This work demonstrates that low-dimensional, lead-free, chiral semiconductors with exceptional air stability can be acquired, without compromising spin splitting and manipulation performance.

Exploring the antiviral potency of γ-FP and PA compounds: Electronic characterization, non-covalent interaction analysis and docking profiling with emphasis on QTAIM aspects

As focuses on a set of pertinent compounds that incorporate a γ-substituted halophenol linkage with pentanamide (PA). The properties of these compounds were comprehensively assessed through various analytical techniques, including density functional theory (DFT) calculations, offering insights into their geometry and electronic energy gap characteristics. Charge delocalization and stability were explored via natural bond orbital (NBO) analysis. The chemical reactivity was further scrutinized by evaluating NBO, Molecular Electrostatic Potential (MEP), Hirshfeld surface analysis and Fukui functions. The compounds were found to exhibit stability attributed to a robust hydrogen bonding network, which was corroborated by Interaction Region Indicator (IRI) and Electron Density (ED) assessments. Additionally, pharmacological properties were predicted using the PASS (Prediction of Activity Spectra for Substances) server. Molecular docking studies suggested potential antiviral and antioxidant properties, particularly concerning carbonic anhydrase. The overall results imply that these compounds possess favorable drug-like characteristics and show promise for biological efficacy. The study also includes a 2D interaction profile image of the four most interacted proteins and a Ramachandran plot to elucidate the stereochemistry of a selected protein. Furthermore, the activities of 6FDM were investigated following a comprehensive literature survey, with detailed findings presented.

Step-by-step tuning of morphology and band gap of ZnS/MoS2 photocatalyst for enhanced visible light to hydrogen fuel conversion

To address the inherent limitations of ZnS and MoS2 as visible light photocatalysts, herein, we report a step-by-step tuning of mixed sulfide composite system (ZnS/MoS2) to achieve enhanced visible light to hydrogen fuel conversion efficiency in the absence of any sacrificial agents. In the first stage, ZnS/MoS2 composite was synthesized by using a single step hydrothermal route and the photocatalytic activity of the synthesized ZnS/MoS2 composite was tuned by varying the ratio of Zn and Mo in the composite. In the second stage, the photocatalytic efficiency of the composite was further enhanced by tuning the band gap and visible light absorption characteristics of the material through cobalt doping (Co-doping) in the MoS2 co-catalyst. The hydrogen generation activity of the tuned composition (1:1.3 ratio of Zn and Mo) of the ZnS/MoS2 composite with 3% Co-doping is obtained as the best (1256 μmol of H2 in 1 h) as compared to the other compositions of the doped composites (1%, 3% and 5% Co doping). The enhanced hydrogen generation through visible light induced water splitting of the developed mixed sulfide composite systems (ZnS/MoS2 and ZnS/Co-doped MoS2) even in the absence of any sacrificial agents is ascribed to their tuned band gap and low electron-hole recombination rate.

Interplay between Growth Mechanism, Materials Chemistry, and Band Gap Characteristics in Sputtered Thin Films of Chalcogenide Perovskite BaZrS3

Interplay between Growth Mechanism, Materials Chemistry, and Band Gap Characteristics in Sputtered Thin Films of Chalcogenide Perovskite BaZrS₃

The effects of a moderate severity hurricane on gap characteristics in a longleaf pine (Pinus palustris Mill.) woodland

Modern forestry research emphasizes infusing management practices with an understanding of natural disturbance regimes—often called ecological forestry. Forestry practices that emulate aspects of natural disturbance regimes are considered an effective approach to balance silvicultural and ecological objectives. Silvicultural research is often available to guide successful regeneration in many forest types, but little information is available about gap patterns from common disturbances in the eastern U.S. like hurricanes. We examined the size, shape, and spatial distribution of canopy gaps formed in a longleaf pine woodland by Hurricane Michael across multiple landscape factors including stand size, composition, and soil types. We found high variation in many gap characteristics but no significant differences in gap size or shape among landscape factors. However, spatial distribution of gaps differed among landscape types in nuanced ways. We also found that stand size complexity may prevent the formation of very large gaps that can disrupt fire continuity in systems managed with frequent fire. The results highlight the ecological importance of hurricane events and provide insight into hurricane gap formation at the landscape scale. The implementation of silviculture practices that emulate a large, rapid, single disturbance event may be more practically applied than management based on disturbances such as lightning or insects which occur over longer timeframes.

Multiple broadband gaps and vibration suppression mechanisms for innovative star shaped metamaterial structures with triangular characteristics

Metamaterials have received extensive attention due to their special properties in the fields of wave attenuation and acoustic engineering. Many researchers have designed metamaterials with different band gap frequency ranges. In this paper, a star shaped metamaterial structure with triangular characteristics is proposed to attenuate mid and low frequency elastic waves in practical applications. The band gap and dispersion characteristics of the structure are numerically studied. The results show that the structure generates ultra-wide band gaps in the frequency range of 6000 Hz, accounting for up to 69.14%. Interestingly, by adding a support structure to the original structural unit, the bandwidth of the improved structure reached 73.89%, and multiple band gaps were opened within 2000 Hz. Finally, the vibration transmission loss of the structure is analyzed by finite element method, and the control performance of vibration transmission in periodic structures is simulated, demonstrating its potential in practical applications.

First-principles investigation of the ultra-wide band gap halides perovskite XBeF3 (X = Na, K) with pressure effects

Based on the first-principles and quasi-harmonic Debye model, the structure, electronic, optical and thermodynamic properties of XBeF3 (X = Na, K) crystals at 0 ∼ 30 GPa are systematically investigated for the first time. The lattice constant, elastic constants, and bulk modulus of NaBeF3 and KBeF3 crystals are calculated under zero temperature and zero pressure, which are consistent with the literature values. The studies of electronic properties show that the ultra-wide band gaps of NaBeF3 and KBeF3 crystals at 0 GPa are 7.096 eV and 7.720 eV, respectively. Their band gaps increase with increasing pressure, while their type is indirect without the influence of pressure. Besides, the band structure of XBeF3 crystals at 0 ∼ 30 GPa is calculated by HSE06 functional. The variation of the XBeF3 band gap calculated by the HSE06 function with pressure is consistent with the trend of GGA functional. Additionally, the optical properties including reflectivity, absorption coefficient, complex refractive index, dielectric function and conductivity of NaBeF3 and KBeF3 crystals from 0 to 30 GPa have been comprehensively investigated. Using the quasi-harmonic Debye model, the relative volume, expansion coefficient, Debye temperature and heat capacity effect with pressures and temperatures of NaBeF3 and KBeF3 at 0 ∼ 30 GPa are also researched. The Debye temperatures of NaBeF3 and KBeF3 at 300 K are calculated to be 656.38 K and 602.6 K respectively. At relatively high temperature, the heat capacity at constant volume gradually approaches the Dulong-Petit limit. The results in this paper show that NaBeF3 and KBeF3 crystals may be used in the fields of lens materials and window materials in the deep ultraviolet range. Additionally, the ultra-wide band gap characteristics of NaBeF3 and KBeF3 enable them to be useful as highly insulating layers and high-voltage capacitors.

Sound insulation prediction and band gap characteristics of four vibrators acoustic metamaterial with composite phononic crystal structure

Acoustic Metamaterial have been widely concerned because of their strong sound insulation characteristics for specific low-frequency bands. However, further optimization is still needed in terms of broadband sound insulation characteristics, and phononic crystals can generate multiple sound insulation bandwidths due to their unique bandgap characteristics. Therefore, a four vibrators acoustic Metamaterial structure with phononic crystals is proposed to broaden the sound insulation performance at medium and high frequencies while retaining the advantages of sound insulation at low frequencies. Firstly, a semi analytical method combining finite element analysis was proposed for the sound insulation performance of the structure. Afterwards, a bandgap theory based on the equivalent medium method was proposed to reveal the reasons for its characteristics. Finally, a cylindrical sleeve structure was designed for a certain rolling rotor compressor, and its sound insulation performance in the cylindrical state was verified through finite element simulation.

Analysis of the Influence of Initial Stress on the Bandgap Characteristics of Configuration-Controllable Metamaterials

Configuration-controllable metamaterials are a kind of metamaterials whose bandgaps can be effectively adjusted through configuration control, but the configuration changes also produce initial stress. In this paper, the distribution of the initial stress of the configuration-controllable metamaterial under axial displacement and the influence of initial stress on the band gap characteristics of the structure were analyzed using numerical and experimental methods. The results show that initial stress has a significant influence on the bandgap characteristics, and the position and width of the bandgap change with the magnitude of the initial stress. The bandgap distribution of the structure after considering the initial stress is more consistent with the reported experimental results. The influence of initial stress on bandgap cannot be ignored. When the compressive loading displacement is 10 mm, the frequency range of the first bandgap is 262 Hz–310 Hz and that of the second bandgap is 394 Hz–405 Hz. And the frequency range of the first and second bandgaps will be converted into 254 Hz–291 Hz and 391 Hz–400 Hz when considering initial stress. The initial stress generated by compression deformation reduces the frequency of the structural bandgap. The beginning and ending frequencies of the first bandgap will move toward low frequencies, and the first bandgap will close when the compression displacement reaches 30 mm. The initial stress generated by tensile deformation increases the frequency of the structural bandgap. The beginning and ending frequencies of the first bandgap move toward high frequencies, and the bandgap will close when the tensile displacement is 30 mm.