Edge Band Research Articles

Band manipulation and spin texture in interacting moiré helical edges

We develop a theory for manipulating the effective band structure of interacting helical edge states realized on the boundary of two-dimensional time-reversal symmetric topological insulators. For sufficiently strong interaction, an interacting edge band gap develops, spontaneously breaking time-reversal symmetry on the edge. The resulting spin texture, as well as the energy of the the time-reversal breaking gaps, can be tuned by an external moir\'e potential (i.e., a superlattice potential). Remarkably, we establish that by tuning the strength and period of the potential, the interacting gaps can be fully suppressed and interacting Dirac points re-emerge. In addition, nearly flat bands can be created by the moir\'e potential with a sufficiently long period. Our theory provides an unprecedented way to enhance the coherence length of interacting helical edges by suppressing the interacting gap. The implications of this finding for ongoing experiments on helical edge states is discussed.

Remote Sensing Monitoring of Rice Fields: Towards Assessing Water Saving Irrigation Management Practices

Rice cultivation is one of the largest users of the world’s freshwater resources. The contribution of remote sensing observations for identifying the conditions under which rice is cultivated, particularly throughout the growing season, can be instrumental for water, and crop management. Data from different remote sensing platforms are being used in agriculture, namely to detecting anomalies in crops. This is attempted by calculating vegetation indices (VI) that are based on different vegetation reflectance bands, especially those that rely on the Red, Green, and near-infrared bands, such as the Normalised Difference Vegetation Index (NDVI) or the Green Normalised Difference Vegetation Index (GNDVI). However, particular features of different crops and growing conditions justify that some indices are more adequate than others on a case-to-case basis, according to the different vegetation’s spectral signatures. In recent years, a vegetation index related to the Red Edge reflectance band, the Normalised Difference Red Edge (NDRE) has shown potential to be used as a tool to support agricultural management practices; this edge band, by taking a transition position, is very sensitive to changes in vegetation properties. This work, focusing on the rice crop and the application of different irrigation practices, explores the capability of several VIs calculated from different reflectance bands to detect variability, at the plot scale, in rice cultivation in the Lower Mondego region (Portugal). The remote sensing data were obtained from satellite Sentinel-2A imagery and using a multispectral camera mounted on an Unmanned Aerial System (UAS). By comparing several vegetation indices, we found that NDRE is particularly useful for identifying non-homogeneities in irrigation and crop growth in rice fields. Since few satellite sensors are sensible in the Red Edge band and none has the spatial resolution offered by UAS, this study explores the potential of UAS to be used as a useful support information tool in rice farming and precision agriculture, regarding irrigation, and agronomic management.

Characterization of Nickel Oxide Nanoparticles Synthesized under Low Temperature.

In this study, ultrafine nickel oxide nanoparticles (NiO NPs) were well synthesized using a simple wet chemical method under low temperature, 300 °C. An Ni(OH)2 precursor was well precipitated by dropping NH4OH into an Ni(Ac)2 solution. TG-DTA showed that the weight of the precipitate decreases until 300 °C; therefore, the precursor was heat-treated at 300 °C. X-ray diffraction (XRD) patterns indicated that hexagonal-structured NiO NPs with (200) preferred orientation was synthesized. In addition, BET specific surface area (SSA) and HRTEM analyses revealed that spherical NiO NPs were formed with SSA and particle size of 60.14 m2/g and ca. 5–15 nm by using the low temperature method. FT-IR spectra of the NiO NPs showed only a sharp vibrating absorption peak at around 550 cm−1 owing to the Ni-O bond. Additionally, in UV-vis absorption spectra, the wavelength for absorption edge and energy band gap of the ultrafine NiO NPs was 290 nm and 3.44 eV.

Effect of Dust Deposition on Chlorophyll Concentration Estimation in Urban Plants from Reflectance and Vegetation Indexes

Using reflectance spectroscopy to monitor vegetation pigments is a crucial method to know the nutritional status, environmental stress, and phenological phase of vegetation. Defining cities as targeted areas and common greening plants as research objects, the pigment concentrations and dust deposition amounts of the urban plants were classified to explore the spectral difference, respectively. Furthermore, according to different dust deposition levels, this study compared and discussed the prediction models of chlorophyll concentration by correlation analysis and linear regression analysis. The results showed: (1) Dust deposition had interference effects on pigment concentration, leaf reflectance, and their correlations. Dust was an essential factor that must be considered. (2) The influence of dust deposition on chlorophyll—a concentration estimation was related to the selected vegetation indexes. Different modeling indicators had different sensitivity to dust. The SR705 and CIrededge vegetation indexes based on the red edge band were more suitable for establishing chlorophyll-a prediction models. (3) The leaf chlorophyll concentration prediction can be achieved by using reflectance spectroscopy data. The effect of the chlorophyll estimation model under the levels of “Medium dust” and “Heavy dust” was worse than that of “Less dust”, which meant the accumulation of dust had interference to the estimation of chlorophyll concentration. The quantitative analysis of vegetation spectrum by reflectance spectroscopy shows excellent advantages in the research and application of vegetation remote sensing, which provides an important theoretical basis and technical support for the practical application of plant chlorophyll content prediction.

Disorder and phase diagrams of higher-order topological insulators

In this work, we study the disorder effects on the bulk-boundary correspondence of two-dimensional higher-order topological insulators (HOTIs). We concentrate on two cases: (i) bulk-corner correspondence, (ii) edge-corner correspondence. For the bulk-corner correspondence case, we demonstrate the existence of the mobility gaps and clarify the related topological invariant that characterizes the mobility gap. Furthermore, we find that, while the system preserves the bulk-corner correspondence in the presence of disorder, the corner states are protected by the mobility gap instead of the bulk gap. For the edge-corner correspondence case, we show that the bulk mobility gap and edge band gaps of HOTIs are no longer closed simultaneously. Therefore, a rich phase diagram is obtained, including various disorder-induced phase transition processes. Notably, a disorder-induced transition from the non-trivial to trivial phase is realized, distinguishing the HOTIs from the other topological states. Our results deepen the understanding of bulk-boundary correspondence and enrich the topological phase transitions of disordered HOTIs.

Influence of zinc ion concentration on structure, morphology and optical properties of spray deposited ZnO thin films

<p>Zinc Oxide (ZnO) thin films were deposited for five different molarity (M) of Zinc acetate hydrated (0.075, 0.1, 0.125, 0.15, 0.175 M) using simple spray technique to study the effect of zinc ion concentration on structure, morphology and optical properties. The XRD patterns of deposited ZnO thin films show hexagonal crystal structure with wurtzite symmetry. The effect of molarity on morphology was studied using scanning electron microscopy (SEM). The elemental analysis was studied by using energy dispersive X-ray analysis (EDX). The optical absorption was recorded by using systronics double beam spectrophotometer (2201). Crystallite size estimated from XRD data was in nanometre (nm) range; however, films deposited for 0.15 M zinc acetate show maximum crystallite size (66 nm) as compared to other samples. All the films show low absorption in wide range (340-999 nm) of electromagnetic spectrum. However, ZnO film deposited for 0.15 zinc acetate hydrated shows maximum blue shifting of absorption edge and higher band gap (3.8 eV) as compared to other samples.</p>

Compositional dependence of structural, physical, and, in particular, optical parameters of Se50–xTe30Sn20Sbx chalcogenide glassy systems

Through this paper, we describe the compositional dependency on physical, structural and optical properties of Se50–xTe30Sn20Sbx (x = 2, 4, 6, and 8) chalcogenide bulk glassy systems, synthesized via the melt quenching method. X-ray diffraction patterns of all the samples conspicuously confirm the formation of the amorphous structure. Various structural parameters like density, molar volume, compactness, atomic density and other associated parameters have been evaluated and the effect of Sb incorporation within the network has been discussed. The studied glass is rigidly connected, as suggested by the gradual increment in the values of estimated average coordination. Tauc's extrapolation method has been employed to determine optical bandgap energy from UV–Vis spectroscopic data, which reveal that optical bandgap energy decreases as Sb content increases. The bond distribution within the glassy network has been studied and discussed. The Mean bond energy and cohesive energy of the glassy systems have been estimated by using the chemical bond approach (CBA). The glass transition temperature varies with composition. The position of the valence band edge and conduction band edge has been determined to inspect the applicability of the as-prepared samples in designing semiconductor devices.

Activation ability of Gd dopant in the ZnSe single crystals

Rare-earth elements are widely used as doping materials as they considerably change the semiconductor optical, electrical, magnetic and radiative properties. This work explores the influence of Gadolinium (Gd) as a dopant on the radiative, optical and magnetic properties of the Zinc Selenide (ZnSe). ZnSe single crystals were grown by the physical transport method and doped during the growth process using a GdSe source. A wide range of characterization equipment was employed to analyze the obtained ZnSe:Gd single crystals. Intracenter radiative transition of the Gd has not been detected. Gd ions activate the background impurities, causing radiative transitions from the conduction band to the Cu2+ level and intracenter transitions within V3+, V2+ and Cr2+ ions. At the same time, the edge band intensity is dependent on the dopant concentration. Optical transmittance decreases, but the position of the fundamental absorption band is unchanged. Single crystals have a zinc blende crystal structure, and Gd ions do not form complexes with native defects or background impurities.

Crop Classification Based on Red Edge Features Analysis of GF-6 WFV Data.

A red edge band is a sensitive spectral band of crops, which helps to improve the accuracy of crop classification. In view of the characteristics of GF-6 WFV data with multiple red edge bands, this paper took Hengshui City, Hebei Province, China, as the study area to carry out red edge feature analysis and crop classification, and analyzed the influence of different red edge features on crop classification. On the basis of GF-6 WFV red edge band spectral analysis, different red edge feature extraction and red edge indices feature importance evaluation, 12 classification schemes were designed based on GF-6 WFV of four bands (only including red, green, blue and near-infrared bands), stepwise discriminant analysis (SDA) and random forest (RF) method were used for feature selection and importance evaluation, and RF classification algorithm was used for crop classification. The results show the following: (1) The red edge 750 band of GF-6 WFV data contains more information content than the red edge 710 band. Compared with the red edge 750 band, the red edge 710 band is more conducive to improving the separability between different crops, which can improve the classification accuracy; (2) According to the classification results of different red edge indices, compared with the SDA method, the RF method is more accurate in the feature importance evaluation; (3) Red edge spectral features, red edge texture features and red edge indices can improve the accuracy of crop classification in different degrees, and the red edge features based on red edge 710 band can improve the accuracy of crop classification more effectively. This study improves the accuracy of remote sensing classification of crops, and can provide reference for the application of GF-6 WFV data and its red edge bands in agricultural remote sensing.

Improving remote sensing retrieval of water clarity in complex coastal and inland waters with modified absorption estimation and optical water classification using Sentinel-2 MSI

The estimation of water clarity in coastal and inland waters from satellite images is limited by significant uncertainties attributable to the optical complexity of these waters. To address this issue, we propose an improved semi-analytical model for retrieving the Secchi disk depth (ZSD) based on the mechanistic model (Lee model) developed by Lee et al. (2015). In the Lee model, a quasi-analytical algorithm (QAA) was employed to estimate the total absorption coefficient (a(λ)) and total backscattering coefficient (bb(λ)) to retrieve the diffuse attenuation coefficient (Kd(λ)). ZSD was then estimated by remote sensing reflectance (Rrs) and Kd. In this study, two improvements were made to the Lee model based on the band specifications of the Sentinel-2 Multispectral Instrument (MSI). First, the reference wavelength (λ0) was shifted from 560 nm and 665 nm to the longer red edge band 705 nm, and the modified empirical formula for estimating a(λ0) was applied to improve ZSD retrieval. Second, waters were classified into different optical water types (OWTs), and the optimal ZSD algorithm was identified for each OWT to further improve the accuracy of ZSD estimation. The proposed model (denoted as QAA_OWT) was calibrated and evaluated with in situ data (N = 399) collected from waters with various optical properties including a lake (Daihai Lake) dominated by colored dissolved organic matter (CDOM), a macrophytic lake (Ulansuhai Lake), and coastal water (the Bohai Sea) dominated by suspended sediments. The validation showed that QAA_OWT improved the accuracy of ZSD retrieval (0.18–5.0 m), with the averaged percentage difference (MAPD) decreasing from 31.9% to 24.9% and the root mean square deviation (RMSD) decreasing from 0.38 m to 0.32 m. The model was further applied to satellite images from the Sentinel-2 Multispectral Instrument (MSI) and independently assessed based on in situ-satellite match-ups (N = 31). The results verified the reliability of the model (MAPD = 31.8%, RMSD = 0.16 m). Time series MSI-derived ZSD maps clearly characterized the spatio-temporal patterns of the water clarity of Daihai Lake. Such maps are of significance in the accurate evaluation of the effectiveness of pollution control measures and aquatic ecosystem protection for lakes with low water quality. Sensitivity analysis revealed the robustness and insensitivity of the proposed model to input noise. This model could be applicable to many satellite sensors with spectral bands similar to those of Sentinel-2 MSI. Furthermore, it can be used as an effective tool for highly accurate remote sensing retrieval of ZSD in optically complex coastal and inland waters.

Landsat-8 vs. Sentinel-2: Landuse Landcover Change Analysis and Differences in Gudur Municipality

With the recent free availability of moderate to high spatial resolution data (10m-30m), land use analysis became more robust. The launch of Sentinel-2a by the European Space Agency, coupled with the availability of free Landsat data, availed more analysis capabilities for the science community with a wide variety of temporal, spatial, and spectral capabilities. This study compares the synergetic use of Landsat and Sentinel-2 in mapping Land Use Land cover themes in Gudur, explicitly utilizing the red edge band of Sentinel-2. A combination of both sentinel and Landsat data results in higher spatial resolution. Classification of the red edge band produces better resolution than the classification of Landsat Imagery.

Low altitude multispectral mapping for road defect detection

Pothole’s defect is major damages indicated the road condition visually, and the structural defects due to some potential causes. Nowadays, new forms of remote sensing technique were widely used, but less studies in the application of low altitude multispectral mapping. The potential of multispectral images is its help better in resolution due to its spectral characteristic. Hence, it helps a lot in feature classification with proper training sample, classifier used, and spectral band composite. Thus, this study aims to extract the defective roads by using the multispectral image of Parrot Sequoia with low flight altitude. This study tries to detect a pothole's existence from band combination and supervised classification other than its common use which ultimately for agriculture purposes. The classifier used in this is Maximum Likelihood, Support vector machine (SVM) and Mahalanobis Distance. 15 different probability of band stacks of green, NIR, red edge, and red band were used as multispectral images. The comparison of the performance between the types of classifier and band combination was modeled and discussed in this study. Classifier algorithm maximum likelihood gives the lowest error of 0.108m² with a combination of NIR + red edge band. SVM gives the lowest error of 0.427m² with a combination of green + NIR + red edge + red band. While Mahalanobis distance gives the lowest error of -0.082m² with a combination of red edge + red band. Averagely, Mahalanobis distance gives the lowest error of 0.299m² of all bands used. Keywords: Road, pothole, UAV, multispectral, UAV and detection

Comparison of the electronic, optical and photocatalytic properties of MoSe2, InN, and MoSe2/InN heterostructure nanosheet-A first-principle study

Recently, investigation on two-dimensional (2D) metal dichalcogenides has attracted significant attention owing to their impressive electronic structure and optical properties for optoelectronics and photocatalytic applications. Nevertheless, the higher rate of the photo-generated carriers and the electron-hole recombination process limits their technological applications. A promising strategy may consist of constructing 2D heterostructures that could potentially enhance their photocatalytic activities. This work reports the structure, electronic structure, optical, interfacial, and photocatalytic properties of MoSe2/InN heterostructure nanosheet. The interfacial interaction between the MoSe2 and the InN layers was the van der Waals bonding type. The valence band edge and conduction band edge positions of consecutive layers were altered near the Fermi level and formed type-II band orientation. The electronic structure and work function results confirmed that heterojunction potentially possesses improved photocatalytic activity. This work provides the basics for the future development of various enhanced heterostructures for photocatalytic applications.

Impact of the reproductive organs on crop BRDF as observed from a UAV

Several crops bear reproductive organs (RO) at the top of the canopy after the flowering stage, such as ears for wheat, tassels for maize, and heads for sunflowers. RO present specific architecture and optical properties as compared to leaves and stems, which may impact canopy reflectance. This study aims to understand and quantify the influence of RO on the bi-directional variation of canopy reflectance and NDVI.Multispectral camera observations from a UAV were completed over wheat, maize, and sunflower just after flowering when the RO are fully developed and the leaf layer with only marginal senescence. The flights were designed to sample the BRDF with view zenith angles spanning from nadir to 60°and many compass directions. Three flights corresponding to three sun positions were completed under clear sly conditions. The camera was always pointing to two adjacent plots of few tenths of square meters: the RO were manually removed on one plot, while the other plot was kept undisturbed.Results showed that the three visible bands (450 nm, 570 nm, 675 nm), and in a lesser way the red edge band (730 nm) were strongly correlated. We, therefore, focused on the 675 nm and 850 nm bands. The Bi-Directional Reflectance (BRF) of the canopy without RO shows that the BRF values were almost symmetrical across the principal plane, even for maize and sunflower canopies with a strong row structure. Examination of the BRF difference between the canopy with and without RO indicate that the RO impact canopy BRDF for the three crops. The magnitude of the impacts depends on crop, wavelength and observational geometry. These observations are generally consistent with realistic 3D reflectance simulations. However, some discrepancies were noticed, mainly explained by the small magnitude of the RO effect on canopy BRF, and the approximations made when simulating the RO layer and its coupling with the bottom canopy layer. We finally demonstrated that the RO layer impact the estimates of canopy traits such as GAI as derived from the multispectral observations.

Extraction of fractional vegetation cover in arid desert area based on Chinese GF-6 satellite

Abstract The red edge band is considered as one of the diagnosable characteristics of green plants, but the large-scale remote sensing retrieval of fractional vegetation coverage (FVC) based on the red edge band is still rare. To explore the application of the red edge band in the remote sensing estimation of FVC, this study proposed a new vegetation index (normalized difference red edge index, RENDVI) based on the two red edge bands of Chinese GaoFen-6 satellite (GF-6). The FVC estimated by using three vegetation indices (NDVI, RENDVI1, and RENDVI2) were evaluated based on the field survey FVC obtained in Minqin Basin of Gansu Province. The results showed that there was a good linear correlation between the FVC estimated by GF-6 WFV data and the FVC investigated in the field, and the most reasonable estimation of FVC was obtained based on RENDVI2 model (R 2 = 0.97611 and RMSE = 0.07075). Meanwhile, the impact of three confidence levels (1, 2, and 5%) on FVC was also analyzed in this study. FVC obtained from NDVI and RENDVI2 has the highest accuracy at 2% confidence, while FVC based on RENDVI1 achieved the best accuracy at 5% confidence. It could be concluded that it is feasible and reliable to estimate FVC based on red edge bands, and the GF-6 Wide Field View (WFV) data with high temporal and spatial resolution provide a new data source for remote sensing estimation of FVC.

Crop distribution extraction based on Sentinel data

Remote sensing identification and classification of crops is the use of remote sensing for estimating crop planting area of timely and accurate monitoring of crop growth and plant diseases and insect pests in advance to make the product output to estimate the key and premise of the study using Sentinel-1 and Sentinel-2 satellite, by random forest algorithm, the traditional optical wavelengths and vegetation index The backward scattering field of red edge information and radar information in feature selection and feature classification, including winter wheat summer corn orchard woodland town water and bare land set three controls, such as the first group contains radar time characteristics, the characteristics of the second control group contains red edge long, the third group includes traditional vegetation index for phase characteristics, analyzed the different classification accuracy. The results from the confusion matrix show that the red edge band edge after index and the radar scattering information to join the crop classification accuracy is improved effectively. Sentinel optical and radar satellites with a time resolution of 5–6 days have great potential for crop monitoring research.

联合GF-6和Sentinel-2红边波段的森林地上生物量反演

光谱反射率能反映地物差异，是森林地上生物量（Aboveground Biomass，AGB）遥感反演的理论基础。红边波段处于近红外与红光波段交界处快速变化的区域，能对植被冠层结构和叶绿素含量的微小变化做出快速反应，对植被生长状况较敏感。研究以GF-6和Sentinel-2多光谱影像作为数据源，结合野外调查AGB数据，构建落叶松和樟子松AGB线性和非线性估测模型，通过比较模型精度选择最优模型进行森林AGB反演和空间分布制图。结果表明：GF-6和Sentinel-2影像红边波段反射率与落叶松、樟子松AGB均呈显著相关（P<0.05），红边波段对AGB估测较敏感。多变量估测模型整体估测效果优于单变量模型，所有模型中多元线性回归模型取得了最优的决定系数（落叶松R²=0.66，樟子松R²=0.65）和最低的均方根误差（落叶松RMSE=31.45 t/hm²，樟子松RMSE=54.77 t/hm²）。相比单个数据源，联合GF-6和Sentinel-2影像构建的多元线性回归模型估测效果得到了显著提升，模型RMSE对于落叶松和樟子松AGB估测分别最大降低了22.9%和11.2%。增加红边波段进行AGB估测能显著提高模型估测精度，三组数据源分别加入红边波段信息后进行建模，模型RMSE得到了显著降低。GF-6拥有800 km观测幅宽和高效的重访周期，可以快速地提供大尺度时间序列数据，在森林地上生物量反演和动态监测方面有着很大潜力。;Spectral reflectance can reflect the difference of ground objects, which is the theoretical basis of forest aboveground biomass (AGB) in remote sensing inversion. Red edge band is located in the special wavelength and scope which change fast at the junction of near-infrared and red bands, which can quickly respond to the small changes of vegetation canopy structure and chlorophyll content. Compared with other bands, red edge band is more sensitive to vegetation growth and chlorophyll change. In this study, GF-6 and Sentinel-2 multispectral images were used as data sources, and the linear and nonlinear models were constructed on the basis of Larch and Scotch pine field survey data for AGB estimation. The estimation accuracy of all models was compared, and the model with the highest estimation accuracy was regarded as the optimal model for the final AGB mapping in the study area. The results showed that the red edge reflectance of GF-6 and Sentinel-2 images were both significantly correlated with AGB (P<0.05), and red edge bands were more sensitive to AGB estimation than other bands. On the whole, the estimation effect of multivariable estimation model was better than that of univariate model. Multivariate linear regression (MLR) model obtained the highest determination coefficient (R²=0.66 for Larch and 0.55 for Scotch pine) and the lowest root mean square error (RMSE=31.45 t/hm² for Larch and 54.77 t/hm² for Scotch pine). Compared with single data source (GF-6 or Sentinel-2), the estimation effect of multiple linear regression model constructed by combining GF-6 and Sentinel-2 images was significantly improved, and the RMSE of AGB estimation model for Larch and Scotch pine decreased by 22.9% and 11.2% in highest measure, respectively. Taking the red edge band as additional variables for AGB estimation can significantly improve the estimation accuracy and effect of the model. The RMSE of the model was significantly reduced by adding red edge band information to three groups of data sources which are GF-6, Sentinel-2 and Sentinel-2 combined with GF-6. GF-6 has an observation width of 800 km and efficient revisit period, which can provide large-scale time series data quickly. As a remote sensing data source, GF-6 has great potential in forest aboveground biomass estimation and dynamic monitoring.

Theoretical investigation on hbox {BeN}_{{2}} monolayer for an efficient bifunctional water splitting catalyst

The search for an active, stable, and abundant semiconductor-based bifunctional catalysts for solar hydrogen production will make a substantial impact on the sustainable development of the society that does not rely on fossil reserves. The photocatalytic water splitting mechanism on a hbox {BeN}_{{2}} monolayer has here been investigated by using state-of-the-art density functional theory calculations. For all possible reaction intermediates, the calculated changes in Gibbs free energy showed that the oxygen evolution reaction will occur at, and above, the potential of 2.06 V (against the NHE) as all elementary steps are exergonic. In the case of the hydrogen evolution reaction, a potential of 0.52 V, or above, was required to make the reaction take place spontaneously. Interestingly, the calculated valence band edge and conduction band edge positions for a hbox {BeN}_{{2}} monolayer are located at the potential of 2.60 V and 0.56 V, respectively. This indicates that the photo-generated holes in the valence band can oxidize water to oxygen, and the photo-generated electrons in the conduction band can spontaneously reduce water to hydrogen. Hence, the results from the present theoretical investigation show that the hbox {BeN}_{{2}} monolayer is an efficient bifunctional water-splitting catalyst, without the need for any co-catalyst.

Effect of electron-phonon interaction and valence band edge shift for carrier-type reversal in layered ZnS/rGO nanocomposites

The artificial stacking of nanohybrid films helps to enhance their properties and thus intrigues researchers to explore this possibility in emerging technologies. The layer-by-layer approach was used to fabricate samples of zinc sulfide/reduced graphene oxide (ZnS/rGO) by using spin coating technique. The structure and optoelectronic properties has been extensively studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–VIS-NIR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Hall measurements. Raman spectrum elucidates the phonon contribution of ZnS and breathing mode of κ-point phonons and sp2 bonds of carbon atoms of rGO. The electron-phonon interactions reveal reduction in electron mobility and enhancement in holes contribution with rGO content leading to surface charge transfer doping (SCTD). XPS results explain the valence band edge and conduction band edge to form type-I band alignment to reconfirm carrier-type reversal. A change in the dispersion of refractive indices along with a small rise in the value of absorption coefficient in terahertz (THz) region for ZnS/rGO nanocomposite films has been observed. These results will open up new opportunities to furthering the science of this technologically important class of materials for future electronics.

Design selective band antenna using coupling sidewall and multi resonator for wireless communications

Design and simulation of antenna with performance operating at bandwidth (4.5-6.5) GHz, with center frequency 5.5 GHz. This antenna constriction from two cylindrical antenna shapes and four cylindrical resonators with include iris to matching impedance, to enhancement sharp edge band and four tuned between coupling sidewall to removed distortions. Improving the frequency selection of the bandwidth requirement antenna is by adjusting the cylinder length of the antenna The proposed antenna is operating ideal filter because the edge of the band rejection is matched the edge of the bandwidth requirement which makes it perform well including broad edges for the band rejection and sharp edges of the bandwidth requirement together with a little insertion between two types and good return loss of the bandwidth requirement. CST software used to investigate and simulated results.