Urbach Energy Eu Research Articles

Elucidating temperature-dependent local structure change and optical properties in GeTe phase-change material

Phase-change memory emerges as a top contender for non-volatile data storage applications. We report here a systematic change in local structure and crystallization kinetics of binary GeTe thin films using temperature-dependent resistivity measurements, which offers single-stage crystallization at around 187 °C, corroborated with x-ray diffraction. Furthermore, the change in chemical bonding upon crystallization is determined through x-ray photoelectron spectroscopy core level spectra, which reveals the existence of Ge and Te components that align with the GeTe crystal structure. Also, an investigation was carried out employing a UV–Vis–NIR spectrophotometer to explore the evolution of optical bandgaps (Eg), Tauc parameter (B) representing the local disorder, and Urbach energy (Eu) of the GeTe material, as it undergoes the transition from a disordered amorphous state to a crystalline state. As crystallization progresses, a consistent shift of Eg from 0.92 to 0.70 eV corresponds to as-deposited amorphous at room temperature and crystalline at 250 °C, respectively. In addition, the reduction in Eu (from 199.87 to 141.27 meV) and a sudden increase of B around crystallization temperature is observed upon increasing temperature, indicating direct observation of enhanced medium-range order and distortion in short-range order, respectively, in GeTe thin films, revealing improved structural and optical properties. These enhancements make the GeTe material ideal for data storage applications of phase-change memory for next-generation computing technology.

Inflated electronic and optical assessment of gC3N4/ZnO nanocomposite as a potential emissive layer material for OLED application

Organo-inorganic nanocomposite materials have been proven to be novel hybrid materials with inflated electronic and optical performance that can be tailored with the judicious selection of the building units or their combinations. Here, hydrothermal, thermal polycondensation, and ultrasonication techniques were used to synthesize pure ZnO, gC3N4, and gC3N4/ZnO with varying weights % such as 10%, 15%, 20%, and 25% of ZnO inorganic filler elements in gC3N4 matrix. The crystalline phase (hexagonal wurtzite) and crystallite size (10.0 nm, 17.6 nm, and 15.90 nm) of the synthesized materials were examined by X-ray diffractometer. The FESEM and HRTEM characterizations revealed the sheet-like gC3N4 and spherical-type ZnO nanoparticle-like microstructures of the samples. The present functional groups, corresponding vibrational frequency, chemical states, and binding energy were investigated using FTIR and XPS spectroscopic methods. Optical parameters such as optical band gap energy (Eg = 3.24 eV), Urbach energy (Eu = 0.41 eV), refractive index (n= 1.99), emission quantum yield (∼ 69.03%), and color purity of the nanocomposites were examined using UV visible and photoluminescence spectroscopic techniques. IV and Hall measurements techniques were used to determine the semiconducting parameters of the optimized sample, such as conductivity (∼62.90×10−5 S/cm), carrier mobility (∼ 44.1 cm2/Volt. Sce), carrier concentrations (∼1.825×1014 cm−3), and sheet resistance (∼1.062×103 Ω/cm2). Due to their excellent optical and electrical behavior, the nanocomposite materials were found to be fairly suitable as a potential emissive layer material for OLED applications.

Fabrication, Physical, Structural, Optical Properties, and γ‐Ray Attenuation Attributes of Germanate Borosilicate Glasses: Role of GeO2

AbstractSamples of germanium borosilicate glasses with chemical formula 50.5B2O3 + 0.5CeO2 + 10SiO2 + (20‐x) CaO + 19Na2O + XGeO2 with 0 (GeO0) ≤ X ≤ 5 (GeO5) mol% were fabricated by using the melt quenching technique. Structure, physical, and optical properties as well as radiation attenuation capacity was examined. XRD data confirmed that GeOX samples were in amorphous state. The density (ρ) of the prepared glass samples increased from 2.24 to 2.55 g/cm3, while the molar volume (Vm) slightly declined from 26.8 to 26.42 cm3/mol. The UV absorption edge shifted to a higher wavelength as the concentration of GeO2 increased. The values of direct band gap ranged from 3.36 to 2.91 eV, and the indirect ranged from 3.12 to 2.75 eV. Urbach energy (Eu) values fluctuated between 0.65 to 0.16 eV. As the Ge4+ ion increased, the glass sample's refractive index enhanced. Mass attenuation coefficients (MACs) of GeOX samples increased from 6.788 to 10.381 cm2/g at 0.015 MeV. The GeO5 sample possessed the lowest half value layer (HVL) and mean free path (MFP). Effective atomic number (Zeff) of GeOX possessed the same trend of MAC. Results confirmed that the suggested GeOX glasses can be applied in different optical and radiation attenuation applications.

Effect of various processing parameters on the properties of ZnO thin films

Zinc oxide (ZnO) thin films are essential in opto-/piezo-electronics due to their transparency, high electron mobility, wide bandgap (∼3.37 eV), and high excitonic binding energy (60 meV). Effects of processing parameters on ZnO thin films, such as the molarity, ageing, thickness, and calcination temperature, on the microstructural and optical properties deposited by sol-gel spin-coating are investigated under one roof. X-ray diffraction (XRD) confirmed the polycrystalline nature of all films, along with a dominant orientation (002) plane, indicating the formation of a c-axis oriented hexagonal wurtzite structure of ZnO regardless of the processing parameters. Peak intensities varied for all samples and exhibited the highest peak intensity annealed at 500 °C, which correlates with the increase in crystallite size from 15.93 to 16.41 nm due to a decrease in defect density via the thermal expansion. 0.4 M aged solution over 70 h showed the variation in the crystallite size and dislocation density, indicating the improvements in the thin film quality. Thickness-dependent ZnO thin films also improved the crystallinity, which was confirmed by high peak intensities. Decreasing the Urbach energy (Eu) of 0.4 M solution indicates reduced lattice imperfections/defects and high electronic quality of thin-film materials. Deposited ZnO films with an ageing time of 70 h and thickness of 109 nm exhibit the highest refractive index of 3.9 and 2.6, indicating light interaction and optimal density. The optimized conditions of sol-gel derived ZnO thin films augment the ease of development of economic devices for practical implications in opto-/piezo-electronics.

Particularities of optical behavior of Ag8SiS6 single crystal

Ag8SiS6 single crystal was grown by directional crystallization from melt. A crystal sample was investigated by optical ellipsometry and spectroscopy. This sample had nonlinear spectral dependences of the refractive index n and the extinction coefficient k. The presence of a sharp maximum in the spectral dependence of the refractive index and a rather sharp decrease in the values of the extinction coefficient k at the wavelength of 780 nm were found. The behavior of the optical absorption edge of the Ag8SiS6 single crystal in the temperature range of 77…300 K was studied. An exponential dependence of the absorption coefficient α obeying the Urbach rule was observed at all the investigated temperatures. The optical pseudo-gap Eg* and the Urbach energy EU were calculated from the obtained experimental data. An increase in temperature of the Ag8SiS6 crystal was found to lead to a monotonic, almost linear decrease in Eg* (1.853…1.615 eV) and a monotonic nonlinear increase in EU (44.32…55.01 meV). The contributions of the temperature-independent (EU)X,C and temperature-dependent (EU)T components to the total Urbach energy EU for Ag8SiS6 were evaluated within the Einstein model.

Sr-doped ZnO thin film on a silicon substrate (100) grown by sol-gel method: Structural and optical study

In the current study, Sr-doped ZnO thin films were fabricated through a sol-gel route on a silicon substrate (100). The structural, optical, and morphological studies were examined through XRD, UV–vis, PL spectroscopy, and SEM. The crystalline superiority is enhanced through increasing Sr content while the optical bandgap is reduced because of lattice distortion and the production of active imperfections in ZnO, which may be the reason for bandgap tailing. The grain sizes observed are 53, 54, and 60 nm for ZnO, ZnSr1%, and ZnSr2%. Microstructural and strain were explored through Scherrer, W–H, and SSP methods. Furthermore, peak broadening was investigated using these methods. UV–Vis spectroscopy was employed to investigate the band gap of all grown thin films, which are 3.37, 3.28, and 3.20 eV of ZnO, ZnSr1% and ZnSr2%. The optical study was carried out to investigate the band gap, including different parameters such as Absorbance (A), transmittance (T), absorption coefficient (α), band gap (Eg) using different methods, band gap by derivative method, urbach energy (Eu), skin depth (δ), optical density (OD), refractive index (n), extinction coefficient (k), optical conductivity (σopt), dielectric constants (εr, εi), and Tan (α) were also explored. PL spectroscopy was used to study the defects in grown thin films. SEM was employed to examine the morphology of all fabricated thin films. ZnO thin film is widely studied for optoelectronics applications.

Influence of Graphene on Sheet Resistivity and Urbach Enery of Nano TiO<sub>2</sub> for DSSC Electrode

Importance of renewable energy cannot be over emphasized. Titanium IV oxide (TiO<sub>2</sub>) is the most suitable semiconductor for dye sensitized solar cell (DSSC) due to its chemical stability, non toxicity and excellent optoelectronic properties. In this research TiO<sub>2</sub> is coated on graphene to enhance its charge transport aiming to reduce recombination which is a main set back in DSSCs. undestanding graphene- TiO<sub>2 </sub>contact is therefore essential for DSSC application. TiO<sub>2</sub> thin films were deposited on single layer graphene (SLG) as well as on flourine tin oxide (FTO) using doctor blading technique. The films were annealed at rates of 2°C /min and 1°C/min up to a temperature of 450°C followed by sintering at this temperature for 30 minutes. Four point probe SRM-232 was used to measure sheet resistance of the samples. The film thickness were obtained from transmittance using pointwise unconstrained minimization approximation (PUMA). UV –VIS spectrophotometer was employed to measure transmittance. Resistivity of TiO<sub>2</sub> on both FTO and Graphene were of order 10<sup>-4</sup> Ωcm. However, TiO<sub>2</sub> annealed on graphene matrix exhibited a slightly lower resistivity 5.6 x10<sup>-4</sup> Ωcm as compared to 6.0x10<sup>-4 </sup>Ωcm on FTO. Optical transmittance on visible region was lower for TiO<sub>2</sub> on FTO than on SLG, 71.48% and 80.11% respectively. Urbach energy (Eu) for weak absorption region decreased with annealing rate. Urbach energies for 1°C/min TiO<sub>2 </sub>on FTO and SLG were 361 meV and 261meV respectively. This was used to account for decrease of disoders of films due to annealing. A striking relation between sheet resistivity and urbach was reported suggesting SLG as a suitable candidate for photoanode of a DSSC.

Tri-Step Water-Assisted Strategy for Suppressing Cs4PbBr6 Phase in Printable Carbon-Based CsPbBr3 Solar Cells to Achieve High Stability.

Often deemed the "natural nemesis" of perovskites, water molecules have been largely circumvented by the majority of researchers in the field of perovskite solar cells. This has resulted in significant hurdles in investigating the beneficial impacts of water molecules on perovskite crystallization. Herein, it is found that by utilizing ethanol with minimal water content and subjecting all-inorganic perovskite to three distinct annealing temperatures within the same solvent, the residual CsBr can be effectively removed, and the formation of the Cs4PbBr6 phase can be curtailed. By selecting an optimal water content, substantial improvements are observed in the crystalline quality of CsPbBr3, the perovskite/carbon interface, and the mesoporous filling effect. The Urbach energy (Eu) is reduced from 38.96 to 35.59meV, and the defect density decreased from 4.16×1014 to 3.39×1014cm-3. As a result, the power conversion efficiency (PCE) improved from 7.55% in the control group to 9.37%. Under severe environmental conditions with a temperature (T) of 85°C and a relative humidity (RH) of 40%, tracking tests over 1200h retained 89.3% of the initial PCE. This research signifies a breakthrough in the fabrication of highly stable and efficient all-inorganic printable mesoscopic perovskite solar cells.

Quantification of the strong, phonon-induced Urbach tails in β-Ga2O3 and their implications on electrical breakdown

In ultrawide bandgap (UWBG) nitride and oxide semiconductors, increased bandgap (Eg) correlates with greater ionicity and strong electron–phonon coupling. This limits mobility through phonon scattering, localizes carriers via polarons and self-trapping, broadens optical transitions via dynamic disorder, and modifies the breakdown field. Herein, we use polarized optical transmission spectroscopy from 77 to 633 K to investigate the Urbach energy (Eu) for many orientations of Fe- and Sn-doped β-Ga2O3 bulk crystals. We find Eu values ranging from 60 to 140 meV at 293 K and that static (structural defects plus zero-point phonons) disorder contributes more to Eu than dynamic (finite temperature phonon-induced) disorder. This is evidenced by lack of systematic Eu anisotropy, and Eu correlating more with x-ray diffraction rocking-curve broadening than with Sn-doping. The lowest measured Eu are ∼10× larger than for traditional semiconductors, pointing out that band tail effects need to be carefully considered in these materials for high field electronics. We demonstrate that, because optical transmission through thick samples is sensitive to sub-gap absorption, the commonly used Tauc extraction of a bandgap from transmission through Ga2O3 >1–3 μm thick is subject to errors. Combining our Eu(T) from Fe-doped samples with Eg(T) from ellipsometry, we extract a measure of an effective electron–phonon coupling that increases in weighted second order deformation potential with temperature and a larger value for E||b than E||c. The large electron–phonon coupling in β-Ga2O3 suggests that theories of electrical breakdown for traditional semiconductors need expansion to account not just for lower scattering time but also for impact ionization thresholds fluctuating in both time and space.

Synthesis of thermochromic CdHgI4 thin film: Insight into the thickness-dependent structural, morphological, linear, and nonlinear spectroscopic properties

This study introduces an in-depth exploration of structural, morphological, linear, and nonlinear optical properties of CdHgI4 thin films deposited by the thermal evaporation technique. In this study, cadmium tetra iodomercurate (CdHgI4) nanopowder was synthesized by fusion method from which thin films of various thicknesses (150 to 450 nm) were deposited on glass substrates by thermal evaporation technique. The Structural investigation conducted by X-ray diffractometer (XRD) established that both CdHgI4 nanopowder and thin film formed in a single phase with a tetragonal crystallographic system. However, the CdHgI4 nanopowder and films display a different preferred orientation as corroborated by texture coefficient determination (Tc). The microstructural features obtained by High-resolution transmission electron microscopy (HRTEM) revealed that the powder particles were agglomerated; however, the particles of thin film were well-defined with high compactness and uniform size. The purity as well as stoichiometry were judged by energy dispersive X-ray analysis confirming the absence of any impurities and samples adopted near stoichiometry features. The surface morphology done by field emission scanning electron microscope revealed that films constituted of nanostructured grains with noticeable growth particles with increasing thickness. The CdHgI4 nanopowder had a direct optical transition of band gap of about 1.41 eV evaluated from diffuse reflectance spectroscopy. The band gap of thin films determined from specular optical spectroscopy varied from 2.20 to 1.58 eV, as the thickness changed from 150 to 450 nm. The thickness dependence of other linear optical parameters, such as Urbach energy (Eu), refractive index (n), optical dielectric constants (ε1, ε2), the surface and volume energy loss (SELF, VELF), were elaborately discussed. The nonlinear optical properties including first-order linear susceptibility, third-order susceptibility (χ(1), χ(3)), NL refractive index (n2), and two-photon absorption coefficients (βc) were greatly dependent on the film thickness.

Investigation of the structural and optical characteristics of La2FeCrO6 double perovskite for optoelectronic applications

La2FeCrO6 nanoparticles were prepared using sol-gel method and their linear and non-linear optical properties were investigated. Optical transmittance and absorption were measured for wavelengths between 200 and 1000 nm using UV–visible analysis at room temperature. The results demonstrated the potential use of La2FeCrO6 in optoelectronics applications due to its interesting optical properties. Transmittance and absorption, as well as absorption coefficients, band gap (Eg), Urbach energy (Eu), refractive coefficients, optical conductivity, and dielectric function were examined. According to the analysis, the band gap energy was determined to be 3.501 eV using the Tauc method, while the Urbach energy value was 0.324 eV. Non-linear sensitivities of the first and third order were also calculated, along with linear and non-linear refractive constants. The results lead to the conclusion that La2FeCrO6 represents a promising material for applications in the field of optical electronics, taking into consideration its optical properties, whether linear or non-linear.

Dysprosium-enriched polymer nanocomposites: Assessing radiation shielding and optical properties

This paper includes a comprehensive analysis of the radiation shielding, optical properties, and structural makeup of polymer composites that contain Dy2O3 additions. XRD-pattern investigates the effect of loading Dy2O3 content on PS, with the average crystallite size of Dy2O3 decreases from 39 nm to 30 nm as Dy2O3 increases from 2.5 to 7.5 wt% in the PS matrix. The optical properties of the nanocomposites showed that with the increase in the Dy2O3 content, the transmittance, as well as the direct and indirect band gap, decreased. The EgIndirect bandgap decreased from 3.1 to 2.75 eV with a Dy2O3 increase from 0 to 7.5 wt%, while the Egdirect Bandgap reduced from 4.6 to 4.35 eV. While the Urbach energy Eu and the refractive index increase, Eu rises from 0.48 to 0.60 e V, and n improves from 1.4 to 1.78 from 0 to 7.5 wt%. In order to conduct an accurate analysis of the gamma-ray attenuation capabilities of the selected new polymer composites, these composites were manufactured with varying proportions of the additive components. With the assistance of a Na(Tl) detector, experimental assessments were carried out on the gamma rays throughout a broad spectrum of photon energies, ranging from 81 keV up to 1416 keV. The sample encased in PS/Dy7.5 demonstrates excellent radiation attenuation, and it is important to note that this novel polymer shielding material does not include any hazardous components.

Influence of pH on growth, structural, thermal, linear and nonlinear optical properties of L-asparagine monohydrate single crystal

This report presents investigation on influence of pH on growth, structural, thermal, linear and nonlinear optical properties of L-asparagine monohydrate (LAM) single crystal for the first time. Single crystals of LAM were grown at different pH by solution growth method by allowing slow evaporation of solvent. Crystal grown at pH 6.4 grows slowly as compare to other crystals grown at other pH values. The slight variation in lattice parameters of grown crystals has been confirmed by powder X-ray diffraction study. FT-IR study confirms the presence of functional groups of LAM in all grown crystals. Influence of pH on optical quality of crystals has been discussed. The crystal grown at pH 5.4 has maximum optical transparency and shows 2 and 20 % more transmission than crystals grown at pH 4.4 and 6.4, respectively. Other optical parameters like cutoff wavelength (λmax), band gap (Eg), linear refractive index (n), reflectance, extinction coefficient (k), electrical susceptibility (χ), optical conductivity(σop), electrical conductivity (σel) and Urbach energy (Eu) of all crystals have been evaluated from transmission data. The LAM crystal grown at pH 6.4 show high values of third order nonlinear optical parameters, as compare to other grown crystals, that attest its suitability for applications like higher harmonic generation, optical switching, optical limiting and other photonic applications over other grown crystals. Thermal stability of the grown crystals has been attested by TG-DTA study.

Structural, Optical and Dielectric Properties of Some Nanocomposites Derived from Copper Oxide Nanoparticles Embedded in Poly(vinylpyrrolidone) Matrix.

Polymer nanocomposite films based on poly(vinyl pyrrolidone) incorporated with different amounts of copper oxide (CuO) nanoparticles were prepared by the solution casting technique. The PVP/CuO nanocomposites were analyzed by X-ray diffractometry (XRD), scanning electron microscopy, UV-Visible absorption spectroscopy and dielectric spectroscopy. The XRD analysis showed that the monoclinic structure of cupric oxide was maintained in the PVP host matrix. The key optical parameters, such as optical energy gap Eg, Urbach energy EU, absorption coefficient and refractive index, were estimated based on the UV-Vis data. The optical characteristics of the nanocomposite films revealed that their transmittance and absorption were influenced by the addition of CuO nanoparticles in the PVP matrix. Incorporation of CuO nanoparticles into the PVP matrix led to a significant decrease in band gap energy and an increase in the refractive index. The dielectric and electrical behaviors of the PVP/CuO nanocomposites were analyzed over a frequency range between 10 Hz and 1 MHz. The effect of CuO loading on the dielectric parameters (dielectric constant and dielectric loss) of the metal oxide nanocomposites was also discussed.

Emergence of enhanced photocatalytic response in GO-hBN nanocomposites with tuned non-linear optical and surface electronic properties

The hexagonal Boron Nitride (hBN) nanostructures with tuned physicochemical properties find huge applications in optoelectronic devices. Herein, we have synthesized nanocomposite of hBN with graphene oxide (GO) in various ratios to acquire composition-dependent variation in their structural, surface electronic, linear, and non-linear optical properties. The insertion of GO in hBN nanosheets has modified their strain landscape, the electronic charge transfers from GO to hBN, increased the working time of free charge carriers, and suppressed electron-hole recombination, thus modifying its work function (WF). GO-hBN nanocomposites observed to have reduced bandgap where creation of defect induced mid-gap states lead to enhancement in non-linear absorption of two photons. Herein, we have established a linear relationship between Urbach energy (Eu), a measure of disorders and non-linear absorption coefficient (αNL). Additionally, we have observed that the tuned bandgap of the nanocomposites has significantly enhanced their performance as high-performance photocatalysts for the degradation of methyl orange, compared to bare hBN or GO. As a result, we discovered that Eu, αNL, WF and photodegradation activity of GO-hBN nanocomposites exhibit analogous variations in response to changes in the content of GO. Thus, by strategically prioritizing the modification of a single parameter while considering the potential effects on other relevant properties for application purpose, GO-hBN can effectively harness large spectrum areas for catalytic and optoelectronic applications.

Vanadium oxides nanostructures for adsorption of Methylene blue, vehicle exhaust and soot of ink as low carbon applications

In this study, V2O5 nanoparticles were synthesized via facile method by annealing ammonium meta vanadate at 450 °C for 1 h. The resulting nanoparticles were analyzed using X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy to investigate their structural and morphological properties. The optical properties of the prepared samples were examined using UV–VIS spectrophotometry. The XRD measurements indicated an orthorhombic V2O5 structure with an average crystallite size of 21.34 nm as calculated using the Debye-Scherrer formula. The synthesized V2O5 nanoparticles showed a plate like rod structure with an average size around 55 nm through TEM and HRTEM analysis. The Urbach energy (Eu) of V2O5 was calculated to be 1.07ev. The V2O5 nano-adsorbents were tested for their effectiveness in the selective removal of MB from an aqueous medium, as well vehicle exhaust and soot of ink from non-aqueous media. During the adsorption process, the impact of several factors including time, adsorbent dose, and different initial concentrations were investigated. Equilibrium adsorption isotherms were evaluated using Langmuir and Freundlich equations. The Langmuir model was found to be a better fit for the adsorption equilibrium, with correlation coefficients of 0.915, 0.904, and 0.912 for MB, vehicle exhaust, and soot of ink, respectively. The experimental kinetic results of V2O5 were found to fit the pseudo-second-order model for both aqueous and non-aqueous media with a higher correlation factor indicating chemisorption during the adsorption process.

Synthesis and characterization of Bi2O3–B2O3–SiO2–MgO glasses: Structural, optical, and shielding properties

The systematic investigation of the impact of Bi2O3 on the structural, spectroscopic, and radiation features of 15SiO2 - 75B2O3 - (10-x) MgO - xBi2O3, x= (0 ≤ x ≥ 10) glasses were studied. The increase in glass density as Bi2O3 content increase is due to the incorporation of Bi2O3 into the glass network. XRD patterns indicate an amorphous, glassy nature of the glasses. The optical absorption spectra suggest that as the content of Bi2O3 increases, the optical band gap (Eopt.) widens and the Urbach energy (Eu) decreases. It has been observed that the opposite trend between the (Eopt.) and (Eu). The radiation shielding characteristics of MgBi glasses have been evaluated through the assessment of several fundamental radiation attenuation variables. As Bi2O3 content increases would enhance properties like (HVL), (MFP), and (Zeq), especially at lower energy ranges. Adding Bi2O3 to the glassy system has a positive impact on enhancing its neutron attenuation ability. The MgBi-10 glass has the best shielding performance against fast neutrons. The MgBi-10 glass sample shows promising properties for optical and radiation shielding purposes.

Optical characterization and defect-induced behavior in ZnAl1.999Ho0.001O4 spinel: Unraveling novel insights into structure, morphology, and spectroscopic features

The ZnAl1.999Ho0.001O4 phosphor, prepared by the solid-state method, crystallizes in the cubic spinel structure. Morphology and chemical composition homogeneity were determined via Energy Dispersive X-ray and SEM analysis. The (Eg) optical band gap was evaluated from the UV/vis absorption spectrum, confirming direct transition behavior according to Tauc's law. The Urbach energy (Eu) in the ZnAl1.999Ho0.001O4 spinel was higher than that in the ZnAl2O4 spinel, indicating increased disorder and a higher concentration of defects due to Ho3+ ions. The penetration depth (δ(λ)), optical extinction (k(λ)), and refractive index (n(λ)) were assessed across wavelengths (λ). The room temperature absorption spectrum revealed several peaks corresponding to the 4f-4f transitions of Ho3+ ions.

Effect of Co/Nd co-doping on the structural, optical, and morphological properties of ZnO nanorods grown on silicon substrate Si (100) by hydrothermal method

In this study, single-doped (cobalt (Co), neodymium (Nd)), and co-doped (Co/Nd) ZnO thin films were fabricated through the hydrothermal method on a silicon substrate (100) and investigated structural, morphological, and optical characteristics. In this work, tunable bandgap engineering of single-phase Co/Nd co-doped ZnO nanorods was reported to be controlled through variation of dopant concentrations. The concentration of neodymium varies as 4, 8, and 12 % by weight, while cobalt is fixed up to 4 %. XRD confirms the phase purity and high crystalline nature of the prepared nanorods. The physical structural parameters such as-fabricated nanorods were investigated in detail. Furthermore, Scherrer, Williamson-Hall (W–H), and size-strain plot (SSP) methods were used to investigate the crystallite size and lattice strain. The optical parameters like absorbance (A), transmittance (%T), energy bandgap (Eg), skin depth (δ), optical density (Dopt), optical conductivity (σopt), Urbach energy (Eu), and extinction coefficient (k), were investigated by UV–vis spectra. This study shows that grown films are suitable for modern optoelectronic applications.

Doping and precoating by Cu-metal and annealing impacts on some physical properties and applications of MnS thin films

We prepared thin films of manganese sulfide (MnS) using a thermal evaporation technique. These films were pre-coated and doped with Cu ((MnS)1-xCux, x = 0.05 g). A lot of work was done on these films using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV/VIS/NIR spectrophotometry, and a two-probe approach to figure out their structure, shape, optical properties, and electrical properties. We investigated various factors including the optical energy gap (Eg), refractive index (n), extinction coefficient (k), Urbach energy (Eu), dielectric constants (εr), dispersion parameters, activation energy (ΔE), mobility, photocatalytic analysis, and Seebeck coefficient. The XRD analysis showed that the thin films were amorphous. The direct optical energy gaps of the pure, Cu pre-coated layer, and Cu-doped MnS films were measured at 3.17 eV, 1.88 eV, and 2.45 eV, respectively. Annealing the films at different temperatures showed normal refractive index dispersion in the NIR region. The addition of copper, both as a pre-coating layer and as doping, resulted in a decrease in film resistivity, indicating their semiconducting nature. FE-SEM analysis provided valuable insights into the morphology of the thin films, revealing a uniform and smooth surface. The electrical characteristics showed that film resistivity decreased with copper addition, confirming enhanced conductivity. These properties hold significance in the development of absorber layers for second-generation solar cells, thermoelectric characteristics, and photocatalysis applications.