Change In Band Gap Energy Research Articles

Boron carbide biodevices for disease-specific biomarker detection: a theoretical study

An effective approach for early diagnosis of lung cancer involves detecting its biomarkers in the patient’s exhaled breath. Acetone was identified as a vital biomarker, showing significant elevation in lung cancer. Two-dimensional boron carbide materials offer benefits such as resistance to high temperatures, stability, and excellent sensitivity toward toxic gas molecules. Here, we explore acetone adsorption on the pristine and transition metal (TM)-doped (Sc, Ti, V, Cr, and Mn) boron carbide monolayers (BCMs) with density functional theory calculations. Our results revealed that the V-, Cr-, and Mn-doped BCM show larger adsorption energy values as compared to the pristine BCM surface. The change of band gap energy of surfaces after acetone adsorption is obtained between 55 and 275%. The work function variation of studied monolayers upon acetone adsorption has been also investigated and results show that V-, Cr-, and Mn-doped BCM systems are sensitive to acetone gas molecules. This work suggests that BCM-based layers can be used as a biosensor to identify VOC biomarkers such as acetone.

Synthesis of Cu2+ doped ZnO@ZnCdS thin film: Optical and electrochemical characterization

Doping strategies modify the optical and electrochemical characteristics of materials. In this research, we investigated the impact of Cu2⁺ doping in ZnO@ZnCdS nanocomposites synthesized via the co-precipitation approach. A comprehensive analysis was conducted on the structural, morphological, optical, and electrochemical features of the samples using various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Energy Dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–Visible absorption, and photoluminescence (PL). Notably, Cu2⁺ doping induces changes in morphology, crystal size, absorption spectra, and band gap energy. Surface investigations reveal a flower-like structure, while XRD analysis indicates an increase in crystal size from 25.5 to 35.2 in thin films with copper content. The absorption spectra of UV–visible-doped ZnO@ZnCdS thin films exhibit reduced peak intensity upon Cu2⁺ addition. Also, optical absorption analysis shows a shift towards longer wavelengths in the emission of ZnO@ZnCdS due to Cu2⁺ inclusion during doping. Likewise, the band gap energy ranges from 1.37 eV to 2.22 eV for ZnO@ZnCdS and Cu2⁺ doped ZnO@ZnCdS, respectively, as determined using Tauc plots. PL spectrum of the Cu2⁺ doped ZnO@CdS nanocomposite indicates emissions in the blue and green regions. Specifically, under 325 nm excitation, the copper-doped material displays a prominent blue and a less intense red emission at 420 nm at 685 nm, respectively. Furthermore, the electrochemical analysis revealed that doping caused a reduction in Rct and an elevation in CSP. These results offer important considerations for the development of cutting-edge functional optoelectronic materials.

Methanol gas sensing properties of transition metals (V, Cr, and Mn)-doped BC3 flake

Volatile organic compounds (VOCs) cause a considerable risk to human life, and it is vital to introduce highly efficient VOC biosensors. Methanol (CH3OH) was identified as a vital biomarker, showing significant elevation in both lung cancer and COVID-19 patients. Two-dimensional (2D) semiconductor gas sensors offer benefits such as excellent sensitivity, resistance to high temperatures and stability. In the present study, we explored methanol adsorption on the pristine and transition metal (TM)-doped (Sc, Ti, V, Cr, and Mn) C3B 2D flakes with the density functional theory (DFT) technique. Our results revealed that the V-, Cr-, and Mn-doped C3B show larger adsorption energy values as compared to the pristine C3B surface. The change of band gap energy of surfaces after methanol adsorption is obtained between 40 and 400 %. Besides, results show that methanol has a quick recovery at room temperature. The work function variation of studied flakes upon methanol adsorption has been also investigated and results show that V-, Cr-, and Mn-doped C3B systems are sensitive to methanol gas molecule. This work suggests that the C3B-based flakes can be used as a biosensor to identify VOC biomarkers such as methanol.

Tuning The physicochemical Properties of CeO2 Nanoparticles for Enhanced Photocatalytic and Anticancer Performance by Zn Doping

Semiconductor nanoparticles (NPs) have attracted considerable attention owing to their potential applications, such as optoelectronic devices, environmental remediation, energy conversion, and biomedical. This work was designed to tailor the physicochemical properties of CeO2 NPs by Zn doping at different concentrations (0 ≤ x ≤ 0.03) to improve their photocatalytic and anticancer performance. The modified co-precipitation route was fruitfully applied to prepare ZnxCe1-xO2 NPs (with 0 ≤ x ≤ 0.03). Different characterization facilities like XRD, TEM, SEM, EDX, FTIR, and PL spectroscopy have been employed to examine the properties of these prepared NPs. XRD data revealed that the crystallite of NPs was changed after Zn doping with the decrease of its crystal sizes. TEM and SEM imaging discovered that the NPs were further sphere-shaped with homogenous distribution. Moreover, SEM elemental mapping with EDX confirmed that the elements (Ce, O, and Zn) in prepared NPs have uniform distribution and chemical composition in prepared Zn0·03Ce0·97O2 NPs. FTIR results determined the functional groups in the prepared NPs. PL spectra observed a decrease in the recombination of electron (e−)-hole (h+) pair with increasing Zn doping due to a change in bandgap energy. Photocatalytic data indicates that the photodegradation efficiency (D) of Rh B dye of Zn0·03Ce0·97O2NPs(75.5%) under UV light during 100 min was greater than pure CeO2 NPs. Cytotoxicity analysis showed that the anticancer effect of CeO2 NPs against human liver cancer (HepG2) increases with the addition of Zn ions. Additionally, these results indicated that the addition of Zn ions to CeO2 NPs plays a role in killing cancer cells at higher concentrations. This study recommended that these NPs could be applied to potential applications in environmental pollution and cancer therapy in vivo studies.

Biomarker detection using boron carbide layer: a first-principles study

A promising strategy for detecting lung cancer requires determining its biomarkers in a patient’s exhaled breath. Acetone has been identified as an important biomarker in the cases of lung cancer. Two-dimensional materials show characteristics such as excellent sensitivity, resistance to high temperatures, and stability which are essential for their effective use in gas-sensing applications. In this work, we investigated acetone adsorption on the pristine and transition metal (TM)-doped (Fe, Co, Ni, Cu, and Zn) C3B monolayers with the density functional theory calculations. We found that the Zn-doped C3B shows a larger adsorption energy value among designed monolayers. The change of band gap energy of surfaces after acetone adsorption is obtained between 29% and 200%. Besides, results show that acetone has a quick recovery at room temperature. The work function variation of studied monolayers upon acetone adsorption has also been investigated and results show that TM-doped C3B systems are sensitive to acetone gas molecules. This work suggests that the C3B-based layers can be used as a biosensor to identify volatile organic compound biomarkers such as acetone.

Highly responsive reduced graphene oxide embedded PVDF flexible film-based room temperature operable humidity sensor

The current study reports a flexible, free-standing nanocomposite thick film based on reduced graphene oxide incorporated PVDF for room temperature humidity sensing application. A facile, cost-effective solvent casting method fabricates PVDF-RGO (PR) films with varied nanofiller loadings (0.1, 0.2, and 0.3 vol%). The structural properties, including the variation in the α, β, and γ polymorphic phases, are studied in detail from XRD, FTIR, and Raman spectra, confirming the β phase’s dominance in composite films at lower RGO content. Optical studies confirm the nanofiller-induced changes in absorbance, bandgap, and Urbach energy. For films with lower RGO concentration (PR1 and PR2), a significant increase in bandgap is observed compared to pure PVDF, and the trend reverses at a higher RGO content (PR3), whereas Urbach energy has depicted an increasing trend with the filler content. Surface morphology and roughness of the film are analyzed using FESEM and AFM images, respectively. Maximum surface roughness is observed for PR3, which is one of the reasons for the exceptional humidity response of the latter sample. The compositional analysis via XPS verified the interaction between RGO and PVDF, leading to the phase transformation. The thermogram of the films manifested the increased thermal stability of composite film due to the inclusion of RGO as a nano additive. The humidity sensing measurements show that the composite films have exhibited excellent sensitivity for the relative humidity range of 11–97% compared to pure PVDF. PR3 has shown maximum sensitivity of 98.99% with a rapid dynamic response and recovery time of 21 s and 26 s, respectively. Hence, the prepared composite has revealed an outstanding humidity response in terms of sensitivity, response/ recovery time, long-term stability, and negligible hysteresis.

Strained AlGaInAs on InP: Bandgap dependence on composition—Model benchmark and optimization

Influence of chemical composition on the bandgap of AlGaInAs deposited on InP is often calculated using models for unstrained composition and then corrected for strain-induced bandgap energy changes using deformation potentials. This method relies on up to 25 coefficients, many of which are burdened with large uncertainty. In this paper, a large set of experimental data is used to verify the accuracy of existing approaches and to search for optimal deformation potentials. It is shown that the main source of inaccuracy is not the deformation potentials, but the unstrained bandgap formulas. Additionally, a novel model is proposed, yielding the highest accuracy on our dataset. For the first time, composition determination of a quaternary alloy on InP is reported using inductively coupled plasma-optical emission spectrometry, which is used as a benchmark for modeling.

Strain Imaging of Electrode Materials in Li-Ion Batteries

Li-ion batteries operate through the migration of Li ions between the electrodes. Therefore, non-destructive observation of the migration with high spatial resolution is important.When charging and discharging, Li-ions are extracted or inserted into electrode materials, which generally causes changes in volume. An atomic force microscope (AFM) can detect and image these volume changes through current collectors with high spatial resolution, which enables us to investigate Li-ion migration without destruction. AFM detects surface displacements synchronizing the charging/discharging cycle, and provides strain images along with topography of the current collector.1) Here, we present our results of lithium titanate oxide (LTO: Li x Ti5O12). LTO is an anode material with high safety having a theoretical capacity of 160 mA h g−1 (from LiTi2O4 to Li2Ti2O4). But the phase change from spinel to rock-salt lead to very small volume changes. Therefore, it might be difficult to observe the Li migration by this method.However, Li4Ti5O12 with a spinel structure has high resistivity, whereas charged Li7Ti5O12 with a rock-salt structure is a conductor. The former is a transparent semiconductor and the latter is a dark metal. The state of charge of LTO can be observed by an optical microscope. The spatial resolution is not enough though the method is easy-to-use.2) High-resolution method has been proposed.3) Photoinduced strain imaging discriminates semi-conductors having bandgap from metallic materials with no bandgap. The method images bandgap variations based on the detection of electric strains caused by electron-hole pair generation. When electron-hole pairs are generated by photon injection, strains are induced, because the lattice constants are determined as the energy of the electron band structure becomes minimum, and the generation changes the energy configuration. The generation of electron-hole pairs is determined from the magnitude relationship between photon and bandgap energies. Bandgap energies can be measured quantitatively by scanning the injected photon energy. When the photon energies are larger than bandgap energies, strains are generated by electron-hole pairs generation. Therefore, mapping of the strains reveals changes in bandgap energies, that is, state-of-charge of LTO.The lithium metal anode has fruitful advantages that are the lowest electrode potential of Li+/Li and low density of Li, which are −3.04 V and 0.534 g/cm3, respectively. However, the lithium dendrite issue is a serious barrier standing in way of the development of high-energy-density batteries with a lithium metal anode.We have been successful in imaging electrochemical reactions in the interface between lithium metal and electrolyte using strain imaging. Precipitation and dissolution of lithium ions in the surface of lithium metal, and electrolyte flow induced by the gradient of lithium-ion concentration should cause the surface displacements of the current collector. We will be able to get a lot of knowledge and information from this observation.

Multiferroic Properties of Co, Ru, and La Ion Doped KBiFe2O5.

The magnetic, electric, dielectric, and optical (band gap) properties of ion doped multiferroic KBiFe2O5 (KBFO) have been systematically investigated utilizing a microscopic model and the Green's function theory. Doping with Co at the Fe site and Ru at the Bi site induces changes in magnetization, coercive field, and band gap energy. Specifically, an increase in magnetization is observed, while the coercive field and band gap energy decrease. This behavior is attributed to the distinct ionic radii of the doped and host ions, leading to alterations in the exchange interaction constants. The temperature dependence of the polarization P reveals a distinctive kink at the Neel temperature TN, which shifts to higher temperatures with an increase in the applied magnetic field h. Furthermore, doping with Ru and La leads to an increase in polarization. The temperature dependence of the dielectric constant exhibits two peaks at the Neel temperature TN and the Curie temperature TC. Notably, these peaks diminish with increasing frequency. Additionally, the dielectric constant demonstrates a decrease with the rise in the applied magnetic field h. This study sheds light on the intricate interplay between ion doping, structural modifications, and multifunctional properties in KBFO, offering valuable insights into the underlying mechanisms governing its behavior across various physical domains.

Insight into the role of Mg/B and Mg/Cu dual dopant on the properties of ZnO nanoparticles prepared by facile one-step combustion route for photocatalytic and antibacterial application

ZnO semiconductors are widely known to have benefits in photocatalytic and antibacterial applications. In this study, (Mg/B)–ZnO and (Mg/Cu)–ZnO were synthesized using the combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The XRD results confirmed a decrease in the crystal size and an increase in the crystallinity of the doped ZnO samples. SEM analysis confirmed the morphological changes in the structure from rod-shaped to spherical, and the particle size decreased in the doped ZnO samples. EDS analysis validated the nanoparticle composition of Zn, O, Mg, B, and Cu without impurities. Raman spectra confirmed the formation of defects due to the substitution of dopants in the ZnO lattice. All samples for FTIR analysis showed functional chemical group vibrations from Zn–O, C–H, and O–H stretching. The existence of dopant bonds with oxygen was also validated from this analysis. The change in band gap energy was observed from 3.13 to 3.10 eV in Mg/Cu–ZnO and 3.12 eV in Mg/B–ZnO sample due to the influence of the addition of dopant ions. The XPS spectra show the chemical composition of the nanoparticle samples and the oxidation numbers that correlate with the results of EDS and XRD analyses. A decrease in the emission intensity in the PL measurement was observed in the green emission region in the Mg/B–ZnO sample, which correlated with the decrease in electron recombination. The Photocatalytic application was performed by measuring its ability to degrade methyl violet dye under visible-light irradiation. The maximum deterioration after 120 min of irradiation was obtained for the Mg/Cu–ZnO, Mg/B–ZnO, and ZnO samples at 92.62 %, 92.20 %, and 80.89 %, respectively. Antibacterial activity increased against S. aureus bacteria in co-doped ZnO samples with inhibition zones of 12.15 mm, 8.15 mm, and 6.45 mm for Mg/B–ZnO, Mg/Cu–ZnO, and ZnO samples, respectively.

Layer‐Dependent Optical Modulation and Field‐Effect‐Transistor in Two‐Dimensional 4H‐SnS2 Layers

AbstractTwo–dimensional (2D) 4H‐polytype tin disulfide (SnS2) flakes are synthesized using the chemical vapor transport technique. The weak Van der Waals force between the 2D SnS2 layers offers an easy exfoliation of flakes down to a bilayer of thickness ≈2.02 (±0.1) nm using a mechanical exfoliation technique. The optical and field effect transistor (FET) characteristics of the exfoliated 2D 4H‐SnS2 layers are studied. The exfoliated layers are used to fabricate the ≈13‐layered SnS2 FET. The 4H‐SnS2 exhibits a high on/off ratio of ≈106 and mobility ≈1–4 cm2 V−1 s−1. The low mobility of the 4H‐SnS2 FET devices shows an insulating state concordant with the 2D Motts variable range hopping mechanism at varying temperatures. Moreover, it is found that the optical bandgap of the 2D SnS2 single‐crystal layers is largely widened for the bilayers and tri‐layers. The optical bandgap energies vary in the range of 2.56–1.99 eV. The significant alteration in bandgap energies of ≈0.57 eV offers downscaling of the 2D nanoscale semiconducting devices. Such layer‐sensitive changes in optical transmittance, absorbance, and bandgap energies are reflected in Commission Internationale de L'Eclairage (CIE) chromaticity, showing the distinct color of transmittance through various 2D 4H‐SnS2 layers.

Synthesis, Characterization and Impedance Analysis of CalciumDoped Zinc Oxide Nanoparticles

The calcium-doped ZnO nanoparticles, Zn1-xCaxO (x = 0, 0.025, 0.05, 0.075) were prepared by the solution combustion method. The synthesized nanoparticles were characterized by various techniques such as XRD, FTIR, Raman, FESEM-EDX, PL, Impedance, and UV-Vis. The Rietveld refinement of the X-ray diffractogram yields the crystalline structure and lattice parameters. Also, the XRD analysis shows that the substitution of Ca into ZnO does not alter the Wurtzite structure of ZnO. The crystallite size of the samples, calculated using the Scherer equation, was found to be between 46 nm and 92 nm. FTIR spectra detect the ZnO-related vibration modes of the samples. The FESEM morphological images suggest the spherical shape of the synthesized nanoparticles. The EDAX spectra identify the presence of Zn, Ca, and O atoms in the samples. The Raman active modes of the ZnO phase were identified by Raman spectral analysis. The analysis of Photoluminescence (PL) spectra gives information about the UV emission and other visible bands corresponding to violet, blue, and green emission representing different intrinsic defects in synthesized nanoparticles. Using UV-vis spectroscopy, the optical transparency and band gap values were examined. The energy band gap obtained by Tauc’s plot was decreased with the increase in Ca doping. Impedance analysis shows that the grain conductivity increased with the increase in dopant concentration. Contrarily, the total conductivity decreased with the increasing doping concentration due to increased grain boundary resistance. The proposed work demonstrates the changes in microstructure, electrical conductivity, and optical bandgap energy with Ca-doping. These synthesized Ca-doped ZnO nanoparticles could be promising materials for photocatalytic applications.

Green synthesis of SnO2 nanorods and Mo– SnO2 nanocomposite for efficient sunlight driven organic dye photodegradation in aqueous solution

Green synthesis methodology was employed for the synthesis of SnO2 and SnO2/MoO3 composite. The leaf extract of Magnifera indica which is rich in polyphenols was used for reducing the precursor metal salt into the corresponding oxides as nanomaterial. The optimum yield of nanomaterials was obtained in 120 min at 70 °C using leaf extract of the Magnifera indica. The structure, morphology, and composition, of the synthesized nanomaterials was studied by FTIR, XRD, and SEM. It was found that the materials were successfully synthesized with rod shape morphology. The catalytic ability of these synthesized materials was evaluated by degradation of Methylene blue in aqueous solution. The crystallite size, bandgap and nanostructure growth with specific shape contributed towards the enhanced photodegradation performance of SnO2/MoO3. There appears a change in bandgap energy from 3.60 eV of SnO2 to 3.36 eV of SnO2/MoO3. The photocatalytic efficiency of nanocomposite SnO2/MoO3 is enhanced to (73.0%) as compared to that of the pure SnO2 (69.0%). The most important being that minimum amount (1 mg) of the nanocomposite has been utilized during these photocatalytic experiments.

A periodic DFT study on superior adsorption of an azo dye over B3O3 monolayer

The objectives of this DFT study are to consider the adsorption properties of the 4-[2-[4-(dimethylamino) phenyl] diazenyl]-benzoic acid (p-methyl red) dye molecule on the pristine B3O3 semiconducting layer for potential application in dye-sensitized solar cells. Adsorption of dye molecules on different positions of the B3O3 nanosheet leads to the formation of the complexes with favorable adsorption energy in the range of -0.25 to -1.48 eV and the 50 to 57% percentage of change in band gap energy of the monolayer. The dye molecule is adsorbed in two forms on the B3O3 surface, the complexes of the trans-isomer with a more negative adsorption energy of -1.48 eV being more stable than -1.41 eV of the cis-isomer complexes. By the adsorption of dye molecules on the pristine B3O3 surface, the electronic properties of the surface change a lot, which in this work can be proved with the percentage of the changes in the gap energy of more than 50%. The present study results show that the studied substrate may be suitable for application in dye-sensitized solar cells via pairing with a desired dye molecule.

Investigation into Red Emission and Its Applications: Solvatochromic N-Doped Red Emissive Carbon Dots with Solvent Polarity Sensing and Solid-State Fluorescent Nanocomposite Thin Films.

In this work, a NIR emitting dye, p-toluenesulfonate (IR-813) was explored as a model precursor to develop red emissive carbon dots (813-CD) with solvatochromic behavior with a red-shift observed with increasing solvent polarity. The 813-CDs produced had emission peaks at 610 and 698 nm, respectively, in water with blue shifts of emission as solvent polarity decreased. Subsequently, 813-CD was synthesized with increasing nitrogen content with polyethyleneimine (PEI) to elucidate the change in band gap energy. With increased nitrogen content, the CDs produced emissions as far as 776 nm. Additionally, a CD nanocomposite polyvinylpyrrolidone (PVP) film was synthesized to assess the phenomenon of solid-state fluorescence. Furthermore, the CDs were found to have electrochemical properties to be used as an additive doping agent for PVP film coatings.

Enhanced Wettability, Hardness, and Tunable Optical Properties of SiCxNy Coatings Formed by Reactive Magnetron Sputtering.

Silicon carbonitride films were deposited on Si (100), Ge (111), and fused silica substrates through the reactive magnetron sputtering of a SiC target in an argon-nitrogen mixture. The deposition was carried out at room temperature and 300 °C and at an RF target power of 50-150 W. An increase in the nitrogen flow rate leads to the formation of bonds between silicon and carbon atoms and nitrogen atoms and to the formation of SiCxNy layers. The as-deposited films were analyzed with respect to their element composition, state of chemical bonding, mechanical and optical properties, and wetting behavior. It was found that all synthesized films were amorphous and represented a mixture of SiCxNy with free carbon. The films' surfaces were smooth and uniform, with a roughness of about 0.2 nm. Depending on the deposition conditions, SiCxNy films within the composition range 24.1 < Si < 44.0 at.%, 22.4 < C < 56.1 at.%, and 1.6 < N < 51.9 at.% were prepared. The contact angle values vary from 37° to 67°, the hardness values range from 16.2 to 34.4 GPa, and the optical band gap energy changes from 1.81 to 2.53 eV depending on the synthesis conditions of the SiCxNy layers. Particular attention was paid to the study of the stability of the elemental composition of the samples over time, which showed the invariance of the composition of the SiCxNy films for five months.

Growth and temperature tuned band gap characteristics of NaBi(MoO4)2 single crystal

Structural and optical properties of double sodium–bismuth molybdate NaBi(MoO4)2 semiconductor compound was investigated by x-ray diffraction, Raman and transmission experiments. From the x-ray diffraction experiments, the crystal that has tetragonal structure was obtained. Vibrational modes of the crystal were found from the Raman experiments. Transmission experiments were performed in the temperature range of 10–300 K. Derivative spectroscopy analysis and absorption spectrum analysis were performed to get information about the change in band gap energy of the crystal with temperature. It was observed that the band gap energies of the crystal at different temperatures obtained from these techniques are well consisted with each other. By the help of absorption spectrum which was obtained from transmission measurements performed at varying temperatures, absolute zero value of the band gap and average phonon energy as 3.03 ± 0.02 eV and = 24 ± 0.2 meV, respectively. Moreover, based on absorption spectrum analysis the Urbach energy of the crystal was obtained as 0.10 eV.

Nano-crystalline precursor formation, stability, and transformation to mullite-type visible-light photocatalysts

A new precursor for the formation of mullite-type visible-light active photocatalyst Bi2Al4O9 has been identified. The crystal structure of the organic–inorganic hybrid perovskite can be described using the hexagonal setting of the rhombohedral unit cell with lattice parameters a = 1.1342(2) nm, c = 2.746(1) nm, and V = 3.059(2) nm3. The presence of di-nitro-glycerin as organic component, which is centered together with two bismuth atoms at the A-sites of the ABX3-type perovskite, suggests for doubling of the a- and c-lattice parameters compared to isostructural BiAlO3 perovskite. The nano-crystalline precursor with the chemical composition [Bi2(C3H5N2O7)]Al4[O9(□1-x(H2O)x)3] (□: vacancies) decomposes at 540(10) K to a quantum-crystalline phase with an average crystallite size of 1.4(1) nm, refined from X-ray powder data Bragg reflections and confirmed by atomic pair distribution function data analysis. Further heating enables a controlled formation of quantum- or nano-crystalline mullite-type phases, depending on temperature and time. The same precursor structure could also be obtained as iron-containing phase and for Al/Fe solid-solution samples. UV/Vis diffuse reflectance spectroscopy suggests an indirect band-gap transition energy of 3.50(3) eV calculated by the Reflectance-Absorption-Tauc-DASF (RATD) method. Temperature-dependent UV/Vis allows to follow the change of band-gap energy across all associated phase transformations. The long- and short-range appearance of each phase has been presented using X-ray Bragg scattering and total scattering data analyses. This is supported by Raman and infrared spectroscopic investigations complemented by density functional theory (DFT) calculations. Moreover, the theoretical calculation confirms the incorporated di-nitro-glycerin. Thermal stabilities of the phases are investigated by using thermal analysis and temperature-dependent X-ray diffraction.

Temperature effects on optical characteristics of thermally evaporated CuSbSe2 thin films for solar cell applications

CuSbSe2 thin film was deposited by co-evaporation of binary CuSe and Sb2Se3 sources. The structural and morphological properties of the deposited thin film were investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis measurements. XRD pattern indicated that deposited thin film has an orthorhombic crystalline structure with the preferential orientation of (013) direction. SEM image presented that the thin film surface is almost uniform. The optical characteristics of the deposited CuSbSe2 thin film were investigated in detail by performing room temperature Raman, temperature-dependent transmittance spectroscopy, and photoluminescence techniques. Raman spectrum exhibited one mode at around 210 cm−1 associated with Ag vibrational mode. The derivative spectroscopy technique was used to obtain the band gap energy of the films. Temperature dependence of band gap energy was investigated by considering the Varshni model. The rate of change of band gap energy, absolute zero value of gap energy, and Debye temperature were determined as −1.3 × 10−4 eV/K, 1.21 eV, and 297 ± 51 K, respectively. The photoluminescence spectrum indicated the room temperature direct band gap energy as 1.30 eV.

Investigation of Radiation Effect on Structural and Optical Properties of GaAs under High-Energy Electron Irradiation.

A systematic investigation of the changes in structural and optical properties of a semi-insulating GaAs (001) wafer under high-energy electron irradiation is presented in this study. GaAs wafers were exposed to high-energy electron beams under different energies of 10, 15, and 20 MeV for absorbed doses ranging from 0–2.0 MGy. The study showed high-energy electron bombardments caused roughening on the surface of the irradiated GaAs samples. At the maximum delivered energy of 20 MeV electrons, the observed root mean square (RMS) roughness increased from 5.993 (0.0 MGy) to 14.944 nm (2.0 MGy). The increased RMS roughness with radiation doses was consistent with an increased hole size of incident electrons on the GaAs surface from 0.015 (0.5 MGy) to 0.066 nm (2.0 MGy) at 20 MeV electrons. Interestingly, roughness on the surface of irradiated GaAs samples affected an increase in material wettability. The study also observed the changes in bandgap energy of GaAs samples after irradiation with 10, 15, and 20 MeV electrons. The band gap energy was found in the 1.364 to 1.397 eV range, and the observed intense UV-VIS spectra were higher than in non-irradiated samples. The results revealed an increase of light absorption in irradiated GaAs samples to be higher than in original-based samples.