Optical Band Gap Energy Research Articles

The incident photons cut-off energy, the optical linear equations and the electron phonon interactions in ZnO thin films annealed at different temperatures

The using RF-magnetron sputtering, the ZnO thin films were deposited on glass substrates at room temperature. Then using an electrical furnace in the presence of argon gas, they were annealed at different temperatures (400–600 °C). It was found that with taking Nc = 4, Za = 2, Ne = 8 for ZnO films for covalently bonded crystalline and amorphous chalcogenides, the constant β has values of about 0.37 ± 0.04 and for halides and most oxides that have ionic structure the constant β has values of about 0.26 ± 0.04 eV. It can be seen that with increasing annealing temperature absorption edge these films have a shifting behavior towards larger wavelength. Due to shifting behavior of defects distribution of atoms into films, the values of the cut-off energy, E cut-off and the λ cut-off of these films were about 3.48 eV and 355 nm, respectively. The ZnO films annealed at 500 °C specially above 3 eV have maximum value of optical density. The different linears fitting of ln (⍺) for films were obtained as y = Ex + F where 10<E < 12.5 and 14<F < 16. The ZnO films annealed at 600 °C have minimum value of electron phonon interaction (Ee-p) in a bout of 0.858 eV. The optical band gap and disordering energy plots of these films can be fitted by linear relationship EU and Eg = 0.0989–0.148 EU. We found that as deposited ZnO films have minimum value of steepness parameter σ in about of 30.93 × 10 −2eV.

A closer look at the fabrication of some doped metal ions in borophosphate glass system and their structural, elastic, optical, and gamma-ray shielding characteristics

Borophosphate host glasses doped with zinc oxide (ZnO), titanium dioxide (TiO2), tellurium dioxide (TeO2), or cerium oxide (CeO2) were synthesized using rapid quenching techniques. Fourier transform infrared (FTIR) spectra, along with deconvoluted FTIR spectra, were recorded in the 400–4000 cm−1 range. Using the models of Tauc and Urbach, the optical energy band gaps of these glasses were found to be 3.212, 3.289, 3.262, 3.087, and 2.475 eV respectively. Due to the incorporation of different metal ions into the prepared glasses, the density increased and the molar volume decreased, making the glass structure highly compact. Since the elastic moduli are directly related to the average cross-link density, the shear and longitudinal moduli show a forward proportionality with the average cross-link density. Detailed reporting focused on the mass attenuation coefficients (μm) and exposure build-up factors (EBF), crucial for evaluating the shielding properties of the material within the energy range of 0.015–15 MeV and penetration depth up to 40 mean free paths (mfp). Glass samples doped with tellurium dioxide exhibited the highest gamma attenuation due to their higher effective atomic number compared to the other samples. Compared to Portland concrete, the prepared glass composites showed higher mass attenuation coefficients across the entire investigated energy range. These results suggest that although Borophosphate glasses doped with cerium oxide have preferred mechanical properties compared with the other prepared glasses, Borophosphate glasses doped with tellurium dioxide could serve as transparent shielding material for medical applications due to their higher attenuation coefficient.

Impact of different rinsing temperatures on SnS thin films created using the SILAR technique

The (SnS) thin films were prepared by Successive Ionic Layer Adsorption and Reaction (SILAR), a versatile and simple method. The cationic and anionic solutions SnCl2.2H2O and Na2S.9H2O respectively were used as precursor materials, which will be deposited on glass substrates to study the effect of rinsing temperature on the properties of our thin films. The structural, morphological, and optical properties were investigated by using X-ray diffraction, Energy Dispersive X-ray analysis (EDX), Scanning Electron Microscopy (SEM) and spectrophotometer. X-ray Diffraction (XRD) patterns indicated that the deposited SnS thin films have an orthorhombic crystal structure. Uniform deposition of the material over the entire glass substrate was shown by Scanning Electron Microscopy (SEM). The optical band gap energy ranged from 1.5 to 1.82eV for direct transitions and from 0.6 to 0.95eV for indirect transitions.

Atomic layer deposition, mechanical, wear resistance, and optical properties of (Cr1-xAlx)2O3 films on Si (100)

This study presents the comparison of microstructure, mechanical, tribological, and optical properties of the ternary chromium-aluminum oxide films ((Cr1-xAlx)2O3) with binary Cr2O3 and Al2O3 films, deposited by atomic layer deposition at 275 °C. The atomic growth per cycle of the Al atoms increased from 3.1 to 8.5 atoms/nm2 on chromium oxide film. The Al2O3 films were X-ray amorphous. The Cr2O3 films contained crystallites of the eskolaite phase. Nano-size (diameter from 3 to 5 nm) crystallites with cubic symmetry and matching with that of cubic γ-Al2O3 or η-Al2O3 phases were observed in (Cr1-xAlx)2O3 films. The ternary film with Al/(Al + Cr) of 0.40 showed the highest hardness (18.4 GPa) and elastic modulus (169.4 GPa), whereas the wear rate of this film decreased by ∼80 % compared with Cr2O3 films. Optical band gap energy values corresponding to the indirect transition model decreased from 2.93 eV for the Cr2O3 film to 2.58 eV for the Cr-Al-O films.

CaAl1.5Fe0.5O4/6%Ni-ZnO nanocomposites: Synthesis, characterization and effective photocatalyst for the photocatalytic degradation of methylene blue dye

This study focuses on synthesizing and analyzing properties of calcium aluminate photocatalytic nanoparticles using the microwave (MW) combustion method by following the rules of green chemistry and investigates their effectiveness in the adsorption of methylene blue (MB) dye which is a crucial contaminant that enters water resources. The synthesized nanoparticles, including CaAl2O4 (CAO), CaAl1.5Fe0.5O4 (CAFO), 6 %Ni-ZnO (NZO), and CaAl1.5Fe0.5O4/6%Ni-ZnO (CAFONZO) composites, were characterized using various techniques. XRD analysis confirmed the formation of spinel structures in all samples. The crystallite size and lattice constants were determined, showing a reduction in Crystallite size of CAO from 45.98 nm to 37.55 nm after Fe3 + doping. Then, with the formation of CAFONZO Crystallite size 13.99 nm was obtained. FT-IR analysis revealed the chemical interactions between atoms in the spinel structures Nitrogen adsorption/desorption isotherms were used to determine the specific surface area of nanoparticles, pore volume, and pore size. Specific surface area of CAO, CAFO, and CAFONZO are 1.637, 1.745, and 9.903 (m2/g), respectively. SEM and TEM images provided insight into the morphology and size of the nanoparticles. According to TEM images, after Fe3 + doping, the size of particles decreased from 85 to 32 nm. UV-DRS was performed to determine the optical band gap energy of the photocatalysts. The calculated band gap values of pure CAO, CAFO, and NZO nanoparticles were 3.2 eV, 2.5 eV, and 2.7 eV, respectively. Mott-Schottky analysis indicated the type of semiconductors and the energy levels of the conduction and valence bands. Valence band (VB) values of CAFO and NZO are 2.86 eV and 2.03 eV, respectively. The photocatalytic activity of the nanoparticles was evaluated by degrading MB under visible light illumination. The adsorption studies were conducted by varying the dosage, pollutant concentration, and pH. The results showed that CAFONZO nanoparticles exhibited the highest photocatalytic efficiency, achieving 96 % degradation of MB within 120 min. The combined photocatalyst demonstrated improved efficiency compared to the individual components.

Scaling up features of photocatalytic degradation and radiation shielding of multicomponent Cr–Co–Zn nanoferrites

Optical, photocatalytic activity, and radiation shielding studies were conducted on CrxCo0.8Zn0.2Fe2-xO4 (0.0 ≤ x ≤ 0.1, Δx = 0.02) nanoferrites for water treatment and radiation shielding applications. The optical absorption analysis revealed that the optical band gap energy values range from 1.864 to 1.803 eV as assessed through Tauc plots. Further analysis of photocatalytic degradation showed that the Cr0.06Co0.8Zn0.2Fe1.94O4 sample exhibited superior methylene blue (MB) dye removal compared to other samples, with an efficiency of 96.74% in 60 min. Additionally, the present nanoferrites exhibited excellent stability in photocatalytic degradation over multiple cycles. The study also investigated the linear attenuation coefficient (LAC) of the current ferrite nanoparticles, demonstrating increased LAC values with higher Cr content, while the half value layer (HVL) diminished with further Cr concentration. The HVL values indicated the potential efficacy of our nanoferrites as radiation shields when compared to standard radiation shielding materials. Overall, this research suggests a new direction for optimizing spinel nanomaterials for applications in water treatment and radiation shielding.

Investigation of structural, optical, and magnetic properties of NiFe2O4 for efficient photocatalytic degradation of organic pollutants through photo fenton reactions

Nowadays, water pollution generated from textile effluents is one of the major problems for the human race and ecology. Hence, development of sustainable strategies to lower the water pollution level has become a burning need. In this regard, the present study focuses on the preparation of nano catalyst NiFe2O4 to catalyze the chemical reactions on industrial organic dyes for their fast cleansing from water. By sol-gel auto-combustion technique, NiFe2O4 nanoparticles were synthesized and exposed to thermal process at temperatures of 400, 600, and 800 °C. Highly crystalline phase with spinel cubic structured NiFe2O4 was formed with a crystal size of 18.71 nm, which was confirmed by XRD analysis. The FTIR spectra showed two fundamental absorption bands in the range 597.80–412.59 cm−1, which are the characteristics of tetrahedral M − O and octahedral M − O bond in NiFe2O4. The surface morphology of calcined NiFe2O4 was investigated by scanning electron microscope (SEM). The nanoparticle size analyzer exhibited that the synthesized NiFe2O4 nanoparticles had an average particle size of ∼ 291.3 nm. Three stage decomposition patterns were observed for NiFe2O4, which was analyzed by a temperature programmed STA. Zeta potential analyzer showed that the synthesized sample S1 and S2 were stable in the dispersion medium. Also, NiFe2O4 exhibited optical band gap energies for direct band transitions within the visible spectrum measured to be 1.43–1.45 eV, rendering them effective as photocatalysts under sunlight. The samples showed magnetic measurements by VSM with saturation magnetization, coercivity, remnant magnetization value of 66.81 emu/g, 4.13 Oe and 12.94 emu/g, respectively. The synthesized photocatalyst, NiFe2O4, at 400 °C, significantly degraded three toxic organic pollutants—Methylene blue, Rhodamine B, and Congo Red—under visible light through ‘Photo-Fenton’ reaction mechanisms. Among the three dyes, Methylene Blue exhibited the highest degradation percentage with a rate constant of 0.0149 min−1 and followed pseudo-first-order kinetic model.

Impact of hydrogen plasma treatment on ITO substrate for enhanced performance of CdS/CdTe solar cells

The indium tin oxide (ITO) film was treated with 100 W-power hydrogen plasma for 5 min before being used as a substrate to fabricate thermally evaporated CdS thin films. The structural, optical, and electrical properties of ITO and grown CdS films affected by pre-deposition plasma treatment were studied. SEM images show that the surface of ITO film becomes smoother after treatment. AFM analysis determines a decrease and increase in the surface roughness of ITO and CdS thin films after treating the ITO substrate. The XRD patterns show an improvement in the crystallinity of the fabricated thin films. Increasing the optical energy bandgap up to 3.699 eV and.2.481 eV for ITO and deposited CdS films respectively. So, design simple CdS/CdTe solar cells at a device temperature of 300 K. Enhancing the photovoltaic parameters and an increment of about 20 % in solar cell performance.

Insight into deposition duration-varied crystallinity, optical parameters, morphology and electrical properties of solution-processed nanostructured CdSSe thin films

Nanostructured cadmium sulpho selenide (CdSSe) films have been grown onto glass substrates for different deposition durations via a facile solution-based method known as chemical bath deposition (CBD). XRD studies revealed that the crystallites in the films possessed hexagonal (wurtzite) structures with predominant orientation along the (002) plane. The crystallite size increased from ∼5.95 nm to ∼16.69 nm with the increase in deposition duration from 1 h to 4 h. The absorbance, transmittance and reflectance measurements were carried out. A transparency of ∼(50–80) % was obtained for the films. The direct optical energy band gap was found to decrease from 1.982 eV to 1.952 eV with the increment of deposition duration from 1 h to 4 h. SEM micrographs of the films revealed the presence of nano spherical-shaped grains with an average size ranging from ∼305 nm to ∼612 nm. HRTEM images illustrated the presence of compact nano-spherical grains and nano-crystallites distributed in random orientations. Raman spectroscopy divulged the presence of CdSe and CdS vibrational Raman modes and overtones in the films. PL spectra revealed a prominent red emission band along with weak luminescent bands in the yellow-red emission region. The presence of Cd–Se and Cd–S bonds in the films was validated using FTIR analysis. Electrical investigation revealed the linear current‒voltage relationship for the films with the rise in conductivity with deposition duration. Hence, deposition duration stands out as a vital parameter for modulating the properties of CdSSe thin films for use in photovoltaic devices and optoelectronics.

Green synthesis of zinc oxide nanoparticles using Terminalia arjuna bark extract: structural, optical and photocatalytic study

Abstract Zinc oxide (ZnO) nanoparticles have been successfully synthesized by using Terminalia arjuna bark extract via a green route. Structural analysis using X-ray diffraction confirmed the prepared samples are crystalline having hexagonal wurtzite structure with space group P63 mc and average crystallite size is found to be 8.93 nm. Rietveld refinement of the data was carried out using Material Analysis Using Diffraction (MAUD) software and reliability parameters of the refinement have been obtained. Optical properties of the sample investigated by ultraviolet – visible diffuse reflectance spectroscopy reveal an absorption peak to lie at 348 nm and the direct optical band gap energy using Kubelka–Munk function is found to be 3.20 eV. Morphological investigation using scanning electron microscopy revealed that ZnO nanoparticles are nearly spherical and agglomerated. Energy-dispersive X-ray spectrometry analysis showed the presence of Zn and O only. Transmission electron microscopy imaging confirmed the predominant hexagonal structure of the prepared nanoparticles having average particles size of 9.66 nm, which is in agreement with the X-ray diffraction result. Fourier transform infrared spectroscopy was used to identify the functional groups and different vibrational modes present in the sample. The photocatalytic activity of the prepared ZnO nanoparticles was studied using methylene blue (MB) dye under a single wavelength UV light source (λ = 254 nm). The degree of degradation of MB solution was about 56 % within 120 min of illumination to UV light and the degradation reaction follows first order kinetics with rate constant 0.00434 min−1.

Sustainable nonvolatile resistive switching memory using chitosan/MEH-PPV polymer blend

Functionalization of materials is crucial in modern science and technology, particularly biodegradable ones, to reduce the increasing electronic waste affecting the planet. In this study, the electronic behavior of chitosan was modified by incorporating the MEH-PPV polymer. Four composites with weight percentages of 0.25 (S1), 0.5 (S2), 1 (S3), and 1.5 (S4) wt% were prepared. The optical energy bandgap of these composites ranged from 2.0 to 3.02 eV. These materials were studied for their potential use in resistive switching memory (ReRAM). Two device classes: Class A (drop cast) and Class B (spin coat), were developed. The Class A S4-based device exhibited memory behavior with a minimum of 20 write/erase cycles. The other devices in this class demonstrated poor conductivity and data noise. Class B devices exhibited no switching, except for the S3-based device. Our research suggests that the thickness of class A devices has a notable impact on their performance limitations. The study shows that the chitosan:MEH-PPV blend holds promise for environmentally friendly ReRAMs, and optimizing the thickness and weight ratio can significantly improve device performance.

Effect of sputter power on red-shifted optoelectronic properties in magnetron sputtered Ag/ZnO thin films

This study explores Ag/ZnO thin films on glass (Corning 0211) substrates, which were deposited using dc/rf magnetron reactive sputtering at varying Ag-sputter powers. The impact of Ag-sputter power on physical properties, such as structural, surface, compositional, optical, and electrical properties, is systematically explored. Grazing angle x-ray diffraction affirms a single-phase hexagonal wurtzite ZnO structure in all films, predominantly oriented along (002) normal to the substrate. Thin films deposited at 90 W Ag-sputter power exhibit superior structural and morphological properties, including greatest crystallite and grain size, minimum stress, and roughness. Electrical studies indicate that the material exhibits a semiconducting nature, with its electrical resistivity decreasing to a minimum of 0.8 Ω cm at 95 W. At this level of Ag sputter power, the films demonstrate low resistivity, high mobility (0.49 cm2/V s), a charge carrier concentration of 9.6 × 1019 cm−3, and an optical transmittance of 79%, along with an optical band gap energy (Eg) of 3.06 eV. This underscores the influence of Ag sputter power in tailoring Ag/ZnO thin films for optoelectronic applications.

Vapor Growth of All-Inorganic 2D Ruddlesden-Popper Lead- and Tin-Based Perovskites.

The 2D Ruddlesden-Popper (RP) perovskites Cs2PbI2Cl2 (Pb-based, n = 1) and Cs2SnI2Cl2 (Sn-based, n = 1) stand out as unique and rare instances of entirely inorganic constituents within the more expansive category of organic/inorganic 2D perovskites. These materials have recently garnered significant attention for their strong UV-light responsiveness, exceptional thermal stability, and theoretically predicted ultrahigh carrier mobility. In this study, we synthesized Pb and Sn-based n = 1 2D RP perovskite films covering millimeter-scale areas for the first time, utilizing a one-step chemical vapor deposition (CVD) method under atmospheric conditions. These films feature perovskite layers oriented horizontally relative to the substrate. Multilayered Cs3Pb2I3Cl4 (Pb-based, n = 2) and Cs3Sn2I3Cl4 (Sn-based, n = 2) films were also obtained for the first time, and their crystallographic structures were refined by combining X-ray diffraction (XRD) and density functional theory (DFT) calculations. DFT calculations and experimental optical spectroscopy support band-gap energy shifts related to the perovskite layer thickness. We demonstrate bias-free photodetectors using the Sn-based, n = 1 perovskite with reproducible photocurrent and a fast 84 ms response time. The present work not only demonstrates the growth of high-quality all-inorganic multilayered 2D perovskites via the CVD method but also suggests their potential as promising candidates for future optoelectronic applications.

Optical, magnetic and electrical properties of new binary MnTiO3-modified Ba(Zr,Ti)O3 materials as solid solution

The complex binary MnTiO3-modified lead-free ferroelectric Ba(Zr0.2Ti0.8)O3 materials were successfully fabricated using a simple wet chemical method. X-ray diffraction and Raman scattering spectral studies revealed that Mn cations were randomly distributed within the host lattice, reducing the optical band gap energy from 3.16 eV (pure Ba(Zr0.2Ti0.8)O3) to 2.43 eV (9 mol.% MnTiO3). The magnetic properties of Ba(Zr0.2Ti0.8)O3 compounds varied with MnTiO3 addition, transitioning from weak-ferromagnetism to typical ferromagnetism and further exhibiting antiferromagnetic-like and/or paramagnetic-like behavior. The maximum magnetic moment was obtained at around 19.4 memu/g, along with a coercive field and remanent magnetization of 92 Oe and 0.6 memu/g, respectively. Additionally, nonlinear polarization with a maximum electrical polarization of 3.11 μC/cm2 remained at 9 mol.% MnTiO3-modified Ba(Zr0.2Ti0.8)O3 compounds. We expected that the observed both ferromagnetism and nonlinear polarization in MnTiO3-modified Ba(Zr0.2Ti0.8)O3 compounds at room temperature would facilitate their use in smart electronic devices.

Evaluating Optical Properties of Mixed-Phase 2D MoSe2/Poly(vinyl alcohol) Nanocomposite Film.

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase.

High-performance Bi2O3 nanoflakes for advanced energy storage applications

In this work, Bi2O3 nanoflakes (NFs) were synthesized using the co-precipitation method. To understand the crystal structure-surface morphology and their functional properties such as optical band-gap energy, specific capacitance and magnetic properties are examined by various analytical techniques including X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), High-Resolution Transmission Electron Microscopy (HRTEM), Vibrating Sample Magnetometer (VSM), UV–Visible Diffuse Reflectance Spectroscopy (UV-DRS), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, and Cyclic Voltammetry (CV). FE-SEM confirmed the formation of the nanoflakes, while HRTEM verified their monoclinic crystal structure and provided details on the orientation of the lattice planes. XRD result showed distinctive peaks corresponding to the α-phase, indicating a crystallite size of 8.21 nm. Raman and XPS results are also demonstrated formation of the Bi2O3 NFs with their signature bands. VSM analysis revealed the presence of both magnetic and nonmagnetic phases in the Bi2O3 NFs. Optical studies indicated a promising band gap of 1.9 eV, suggesting potential for optoelectronic applications. Surface analysis confirmed the composition of Bi+ and O2− in the NFs. Additionally, electrochemical assessments through CV demonstrated a significant specific capacitance of 537 F/g at 20 mV/s. Nyquist plot analysis suggested an equivalent circuit R(CR)(CR), indicating an optimal fit. Furthermore, we have made the systematic comparison of optical band gap energy of Bi2O3 with reported different nanostructures such as Peanut, needles, rod and flakes and found that the present study nanoflakes offer much lower band energy compared to above mentioned all other morphologies. Due to the obtained lower energy band gap and specific capacitance performance of the Bi2O3 NFs, it is strongly suggested to the advanced energy storage applications.

Exploring the impact of iron doping on the photocatalytic efficiency of TiO2 coatings produced on Ti via PEO

In this study, composite coatings of TiO2/Fe3+ were developed by incorporating Fe(NO3)3 into TiO2-based coatings, produced via plasma electrolytic oxidation (PEO) on unalloyed titanium. The ability of these coatings to photodegrade methylene blue (MB) under visible light was investigated. The morphology, chemical composition, and optical properties of the PEO coatings were characterized using various techniques, including X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, and UV–Vis diffuse reflectance. All coatings exhibited a porous structure, with phase analysis revealing the formation of anatase and rutile phases during the coating process. The coatings were also found to be hydrophobic. Increasing the concentration of Fe(NO3)3 in the composite coatings from 0 to 0.1 g/L resulted in a decrease in the optical band gap energy from 3.05 eV to 2.95 eV. The PEO coating with 0.10 g/L of Fe(NO3)3showed the highest photocatalytic activity (PA), achieving 70 %. This improvement in PA is likely due to the formation of a heterojunction, which effectively separates electron/hole pairs.

Oxygen vacancy modulated optical and dielectric properties of photoactive γ-Fe2WO6

Ferrite compounds have gained scientific attention for their multifunctional attributes. This investigation explores the structural, optical, dielectric and conductivity properties of polycrystalline γ-Fe2WO6 synthesized by the solid state route. The X-ray diffraction confirmed the orthorhombic structure and single-phase formation, while the electron microscopy showed uniform distribution of dense micrometer-sized grains in γ-Fe2WO6. The FTIR spectroscopy analysis validated the presence of active stretching and bending modes, signifying oxygen anion vibration at both Fe and W sites. The simultaneous presence of Fe2+ and Fe3+ ions in the matrix, as confirmed by X-ray photoelectron spectroscopy (XPS), results in an augmented optical energy band gap and contributes to dielectric permittivity due to the charge carrier hopping mechanism between the trap sites. The compound manifests semiconductor attributes, evident in its indirect optical band gap measuring 1.7 eV. It is observed that the compound has effectively degraded the Methylene Blue (MB) under the visible light within 40 min with a degradation efficiency up to 63 %. The material's electrical conductivity, follows the Jonscher's power law, signifies its semiconductor nature and adheres to the Small Polaron tunneling model for charge conduction between neighboring sites. The impedance (Z′) curves exhibit dielectric relaxation (≤ 10 kHz) with a similar activation energy to the dc conductivity study. The activation energy, determined from both the impedance and conductivity analyses, indicates a connection with the migration of oxygen vacancies within the material. Our observation reveals the presence of oxygen vacancies, which possibly act as in-gap electron traps, enhancing the correlated optical and ac conductivity properties, making it an appealing material for diverse multifunctional applications.

Investigations on structural, morphological and UV light detection characteristics in p- ZrO2/ n-Si Heterostructure based devices

The development of hetero-structured based UV photodiode is a rapidly growing interest in the area of optoelectronic applications. In recent years, one of the next generation semiconductor material zirconium dioxide (ZrO2), has attracted much attention for UV photodiode applications. The curent research work focuses on the fabrication of ultraviolet (UV) photodetectors using ZrO2 nanocrystals with different molar concentrations. Using the co-precipitation method, ZrO2 nanocrystals were formed onto n-Si substrate. The prepared ZrO2 nanocrystals were characterized by XRD, UV–visible spectroscopy, FeSEM, HRTEM, PL spectroscopic analysis. The structural analysis of ZrO2 nanoparticles shows the cubic space groups with ((Fm-3m, Z = 4) and (Im-3m, Z = 1) respectively. The morphological analysis reveals the irregular shape and highly agglomerated. The TEM and HR-TEM images, and SAED pattern of ZrO2 NPs were obtained at higher mole concentration. The optical energy band gap of ZrO2 nanocrystals were determined in between 3.12 and 2.86 eV. The PL emission spectrum of ZrO2 nanoparticles shows highly intensive emission bands between 360 nm and 520 nm. The optimum ZrO2 (0.3 M) nanocrystal layers were formed onto n-Si substrate which was stacked between top and bottom Ag electrodes. The current-voltage measurements (I–V) plots and ln J-V plots characteristics of the fabricated Ag/p-ZrO2/n-Si/Ag devices were investigated under dark and UV illumination. The p-ZrO2/n-Si junction diodes exhibit the ideal rectifying function at higher molar concentration of ZrO2 diode, and the reverse saturation with maximum photo sensitivity was investigated.

Structural and optical study of RF-magnetron sputtering SnO2 thin films: impact of post annealing temperature

Tin oxide (SnO2) thin films are prepared using radio frequency magnetron sputtering (RF) method and then annealed at different temperatures in the range of 550–750 °C for 1 h. The effects of annealing temperature on the structural and optical properties of the films are investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometer. It is evident that the annealed films have flat surface with smooth morphology. Based on the XRD graph, as deposited films were amorphous and the annealed films had polycrystalline nature and contain the SnO2 tetragonal rutile phase. According to Raman spectra, the annealed films revealed three vibration modes Eg, A1g and B2g at the frequencies of Sn-O bond vibrations, which related to the SnO2 phase. The samples exhibit an average optical transmittance with more than 80 % between 400 − 700 nm. The refractive index values were in the range of 0.9-2.4 at visible wavelength. It is found that with increasing annealing temperature the films become more transparence while the refractive index and the extinction coefficient increased. The optical band gap energy decreases with increasing annealing temperature that means that the optical quality of annealed films is improved.