Pure ZnO and Na-doped ZnO nanoparticles (Na = 1%, 3%, and 5%) have been synthesized by the simple co-precipitation method. XRD patterns and Rietveld refinement confirm the P63mc space group corresponding to the single-phase hexagonal wurtzite crystal structure of ZnO. SEM micrographs show a spherical particle structure with an average particle size of 40–60 nm in all prepared samples. XPS studies reveal the existence of defect-level states and oxygen vacancies (Vo’s) in all the synthesized samples; Vo’s increase with Na doping. UV-Visible spectroscopy indicates a decrease in the energy band gap from 3.23 eV to 3.19 eV with increasing Na concentration for Na-doped ZnO nanoparticles. The Photoluminescence spectroscopy results confirm the presence of defect-level emissions and lattice defects, including Vo’s, in all the prepared samples, and these increase with increasing Na doping. FTIR spectra confirm the presence of functional groups and chemical bonding at the ZnO interface. In the FTIR spectra, a weak absorption peak around 670 cm−1 confirms the presence of Na in the ZnO matrix, and the strong peak around 532 cm−1 indicates the formation of hexagonal wurtzite ZnO nanoparticles. VSM measurements show room-temperature ferromagnetism (RTFM) in all Na-doped ZnO nanoparticle samples. RTFM increases with enhancing Na-doping and increasing Vo’s, and a maximum saturation magnetization of 54.73 × 10−4 emu/gm was found in the 5% Na-doped ZnO sample. The origin of RTFM in the Na-doped ZnO system may be Vo’s and defects. The RTFM in the Na-doped ZnO system may be a suitable material for future spintronic applications.
X-Ray Photoelectron Spectroscopy (XPS) has been utilized to extract local electrical potential profiles by recording core level binding energy shifts upon application of a DC and/or AC [Square Wave (SQW)] bias at different frequencies. To carry out these measurements, co-planar capacitor devices with a polyethylene membrane (PEM) coated with Ionic Liquids (ILs); N,N-Diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) and/or its 1:1 vol mixture with N,N-Diethyl-2-methoxy-N-methylethanaminium tetrafluoroborate (DEME-BF4) are constructed. Analyses were carried out in-operando; such that XPS measurements were performed simultaneously with current and Electrochemical Impedance (EIS) measurements under UHV environment. ILs have complex charging/discharging dynamics, and they induce formation of Electrical Double Layer (EDL) at the interface of the electrode. Certain properties of this process can be extracted via AC modulation under appropriate time windows. Herein, two frequencies, 10 kHz and 0.1 Hz, were selected to investigate the effects of fast polarization and slow migratory currents, respectively. Local electrical potential developments were extracted at different locations on the device, from the variations in binding energies before and after adding two equivalent resistors in series to the device in three different configurations. This modification of the circuit allowed us to quantify the AC currents passing through the device, as well as the system’s resistance and capacitance under specific conditions. Moreover, majority of the resultant XPS data could be faithfully reproduced by the LT-Spice simulation software, which enabled us to construct realistic equivalent circuit models of the electrochemical systems investigated. With this non-invasive nature of the methodology, XPS becomes a useful tool for extracting localized electrochemical information and may be of great importance in better understanding of energy harvesting and storage systems.
Angle-resolved soft X-ray emission spectroscopy (SXES) provides a powerful probe of anisotropic electronic structures; however, quantitative interpretation of angular emission intensities has long been impeded by the convolution of intrinsic transition anisotropy and extrinsic X-ray self-absorption effects. In particular, for layered materials such as graphite, the extent to which experimentally observed angular dependences reflect intrinsic π- and σ-bonding characteristics remains insufficiently clarified. In this study, we systematically investigate the exit-angle dependence of the C–K soft X-ray emission spectra of highly oriented pyrolytic graphite (HOPG) over a wide angular range, extending from the grazing-exit critical angle (GEc) to 90°, using an EPMA-based SXES system equipped with a rotation–tilt specimen stage. Raw emission intensities exhibit pronounced angular variations arising from a convolution of intrinsic emission anisotropy and geometry-dependent attenuation. By explicitly incorporating X-ray self-absorption into the angular analysis and comparing raw and normalized spectra, we quantitatively separate the intrinsic angular distributions of the π- and σ-bonding components from absorption effects associated with photon escape depth. After absorption correction and normalization, the angular dependences of the π- and σ-derived intensities show good quantitative agreement with theoretically predicted transition-probability distributions over most exit angles. In contrast, spectra acquired in the immediate vicinity of the grazing-exit critical angle exhibit pronounced deviations from absorption-corrected behavior, characterized by a strong suppression of the σ component and a relative enhancement of the π component, indicating additional optical and near-surface effects beyond conventional bulk emission models. These results establish a quantitative framework for interpreting angle-dependent C–K soft X-ray emission in graphite, clarify the respective roles of intrinsic electronic anisotropy and self-absorption, and highlight grazing-exit SXES as a sensitive regime for exploring anisotropic and near-surface phenomena in layered materials. The present approach provides a practical and experimentally grounded framework for interpreting angle-resolved soft X-ray emission from bulk anisotropic materials.
Employing first-principles calculations, this study systematically investigates the electronic structure, optical properties, and photocatalytic activity of a phosphorus-doped g-C3N4/WSSe heterojunction. The undoped g-C3N4/WSSe heterostructure possesses an indirect band gap of 2.18 eV and operates via a Z-scheme charge-transfer mechanism. Phosphorus doping introduces localized impurity states within the bandgap, resulting in a slight narrowing of the bandgap. Importantly, the dopant converts the Z-scheme alignment into a type-II configuration and changes the bandgap from indirect to direct. Furthermore, P-doped impurity junctions exhibit higher electron mobility and stronger visible light absorption. The calculation results for Delta G_H* indicate that P doping primarily modulates the electronic properties of the heterojunction, while its effect on surface hydrogen adsorption exhibits a different trend. This highlights the necessity of implementing synergistic surface modification strategies. These theoretical results offer useful guidance for designing efficient heterojunction photocatalysts.
Charge transfer between perylene and bromine molecules was studied using X-ray absorption fine structure spectroscopy near the carbon and bromine K edges (C K and Br K NEXAFS). The effect of the top-contact gold layer was examined. Bromine molecules construct a pi-complex with perylene molecules in the form of Br3-, as confirmed by the Br K NEXAFS spectrum showing an intermediate spectral shape between Br2 and Br-. The pi-complex became unstable when evacuated and bromine substitution reaction proceeded, presenting characteristic spectral features of Br-C bonds in both the Br and C K NEXAFS spectra. The Br-substituted perylene formed a charge-transfer complex in a similar manner as the unsubstituted perylene, and the vacant state in the perylene molecules was confirmed by the 1 s to singly unoccupied molecular orbital (SUMO) transition at the absorption edge in the C K NEXAFS spectrum. The SUMO at the top-contact gold interface was filled with Au electrons and remained unoccupied in the bulk, as confirmed by the probing depth-dependent spectra.
Nickel oxide (NiO) thin films were fabricated on glass substrates using the successive ionic layer adsorption and reaction (SILAR) method, and the influence of deposition cycles on their surface evolution and multifunctional properties was systematically investigated. The central objective of this work was to understand how a single fabrication parameter-the number of SILAR cycles-controls morphology, crystallinity, defect chemistry, electrical transport, and antibacterial activity. Structural analyses revealed the formation of cubic NiO with improved crystallinity at intermediate deposition cycles. Atomic force microscopy showed that surface roughness decreases initially and then increases at higher cycles due to grain agglomeration. X-ray photoelectron spectroscopy confirmed Ni2+ as the dominant oxidation state, with cycle-dependent variations in hydroxyl and oxygen-related surface species. Optical investigations indicated that defect-related emissions are minimized at intermediate cycles, while electrical measurements revealed a transition from n-type to p-type conductivity at higher cycle numbers. In addition, all films exhibited measurable antibacterial activity against E. coli under visible-light irradiation, with performance influenced by surface and structural characteristics. These findings demonstrate that controlled adjustment of SILAR cycles provides an effective strategy to tailor the structural quality and multifunctional behavior of NiO thin films, offering potential for applications in optoelectronics, surface coatings, and antimicrobial technologies.
We propose a surrogate model that uses the full wide-energy-range (survey) X-ray photoelectron spectroscopy (XPS) spectrum to quantitatively capture spectral shapes and changes in the sample structure (e.g., an In2O3/Si bilayer) as functions of film thickness. Although it was known that XPS survey spectra could be calculated for each sample structure using the NIST Simulation of Electron Spectra for Surface Analysis (SESSA), version 2.2.0 of Standard Reference Data 100 (SRD 100), exploring solutions for the sample structure required an unacceptably large amount of computational time to obtain accurate and error-assessed results. The necessity to solve this problem led us to propose a surrogate model that generalizes the calculation results of SESSA. A key feature is the explicit decomposition of the survey spectrum into contributions from individual electron orbitals, with their thickness dependence characterized by response functions for which we quantify the attenuation length by defining the total electron attenuation length as the average distance a photoelectron with an initial kinetic energy of Ek travels before losing target energy (4E) through multiple scatterings and being detected at a reduced kinetic energy of E ' k(= Ek-4E). Unlike analyses that rely solely on peak intensities, our approach uses the full spectrum to enable accurate and efficient thickness estimation.
The electronic structures of stable, singlet N-heterocyclic carbenes (NHC) have been studied via calculated Kshell (C1s and N1s) vertical, ionization energies. We propose an electronic parameter NEP (Novak electronic parameter) which can describe electronic structure properties of free NHC molecules. NEP is derived from K-shell core ionization energies for C and N atoms of carbene moiety which are deducible from X-ray photoelectron spectroscopy. NEP allows estimating sigma-electron donating and pi-electron accepting abilities NHC. The carbenes studied include classical and non-classical NHC. The calculations were performed using GW method implemented in NWChem software. We pay special attention to the effects of alkylation, aromatic ring substitution and ring enlargement on NHC electronic structure.
We report accurate atomic data of photoionization and photoabsorption for neon like Ar8+ and K9+ ions. These include ionization threshold limits, transition energies, oscillator strengths, radiative rates, and quantum defects of electric dipole (E1) transitions for various Rydberg series originating from the 1s22s22p6(1S0) ground state up to the n = 20 level. The calculations of the photoionization and photoabsorption are performed in the framework of the relativistic configuration interaction approach implemented in the Flexible Atomic Code. The obtained results of 2s2p6(2S1/2)np and 2s22p5(2P)ns/nd resonance series show a good agreement with the available literature values for Ar8+ and K9+ ions. In addition, we report new calculations on K-shell photoexcitations (1s2s22p6(2S1/2)np) in both ions. These results are critically needed in modeling and diagnostics as well as interpretation of high-resolution spectra from astrophysical and fusion plasmas.
The multi-configuration Dirac-Hartree-Fock method (MCDHF) and the corresponding large-scale calculation program GRASP2K were used to systematically study the 2p-1s radiative transition processes of the inner-shell excited states of Z = 12-54 C-like ions. The electric dipole E1 radiation transition and the magnetic quadrupole M2 forbidden transition process are included. The X-ray spectra of some C-like ions are given. Electron correlation effect is fully considered. The high-order relativistic effects, such as Breit Interaction (BI) correction, quantum electro dynamics (QED) correction and finite nuclear mass correction etc. are also considered. The calculated results are in good agreement with other theoretical and experimental results.
This manuscript presents a comprehensive study on the spectral properties and photoionization dynamics of atoms encapsulated by fullerene cages, specifically focusing on a hydrogen atom encapsulated in a C36 fullerene. For this objective, we use a comprehensive relativistic methodology, leveraging the Dirac-Coulomb Hamiltonian in a relativistic configuration interaction scheme, incorporating a power-exponential potential to simulate the fullerene cage's confining effect. By incorporating the Gaussian potential, the Dirac equation is modified to provide solutions covering both continuous and bound state wave functions. As a case study, thorough investigations are performed on the changes in energies, transition rates, wave functions, photoionization cross sections, and photoelectron angular distribution parameters for the hydrogen atom inside a C36 fullerene cage. We perform a detailed analysis, compare our results with other available data, and find good agreement. This study is not only important in the field of atomic physics and quantum chemistry but also offers insights into the design of nanocomposite materials and the development of optical materials and photonic devices.
X-ray Photoelectron Spectroscopy (XPS) is a crucial technique for material surface analysis, yet interpreting its spectra is often challenging for both human analysts and automated methods due to the prevalence of variable spectral shifts and overlapping peaks. This project introduces a machine learning solution using a Spatial Transformer Network (STN), a type of neural network that implicitly learns to align spectra. An STN model was designed to classify the chemical environments present in an input spectrum, using functional groups as a proxy. The model was trained and tested on a large synthetic dataset of 100,000 spectra, created by linearly combining real experimental data from a library of 104 polymers. Beamson and Briggs (1993) To simulate experimental variability, random uniform shifts and broadening were applied to the data. The STN was found to effectively correct for random electrostatic shifts (up to 3.0 eV) and achieved relatively high accuracy (similar to 82%) in identifying functional groups, despite utilizing a much simpler architecture than previous work. These findings demonstrate that neural networks can effectively learn the underlying relationships between spectral features and chemical composition when they are able to intrinsically account for variable shifts. This work advances the development of more reliable automated XPS analysis, offering potential as an assistive tool for researchers and as a core component in future autonomous systems like self-driving laboratories.
We have investigated the electronic structure of Ba4Ir3O10 within the density-functional theory (DFT) using the generalized gradient approximation while considering strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. Ba4Ir3O10 has a quasi-2D structure composed of buckled sheets, which constitute corner-connected Ir3O12 trimers containing three distorted face-sharing IrO6 octahedra. The Ir atoms are distributed over two symmetrically inequivalent sites: the center of the trimer (Ir1) and its two tips (Ir2). The Ir1-Ir2 distance within the trimer is quite small and equals to 2.58 & Aring; at low temperature. As a result, the clear formation of bonding and antibonding states at the Ir1 site occurs. The large bonding-antibonding splitting stabilizes the dyz-orbital-dominant antibonding state of t2g holes and produces a wide energy gap at the Fermi level. However, the energy gap opens up only with taking into account strong Coulomb correlations at the Ir2 site. Therefore, we have quite a unique situation when the insulating state is driven by both the dimerization at the Ir1 site and Mott insulating behavior at the Ir2 one. We have investigated resonant inelastic x-ray scattering (RIXS) spectra at the Ir L3 edge. The calculated results are in good agreement with experimental data. The RIXS spectrum possesses several sharp features below 2.1 eV corresponding to transitions within the Ir t2g levels. The excitation located from 2.1 to 4.6 eV is due to t2g-eg and O2p-t2g transitions. The wide structure situated at 6.2-12 eV appears due to O2p-eg and charge transfer transitions. We have also presented comprehensive theoretical calculations of the RIXS spectrum at the oxygen K edge.
Determination of the electron inelastic mean free path (IMFP) in complex and functional materials is a fascinating problem for which scattered results can be found in present literature. Knowledge of the IMFP is crucial in determining the probing depth of several important techniques based on the collection of electrons excited by external probes. In particular no experimental data can be found for several oxides including MoO3, a promising material used in several forms for applications. To the purpose of measuring the IMFP, we performed accurate constant initial state (CIS) Si2p photoemission experiments on Si wafers covered with layers of amorphous MoO3 of variable thickness, using synchrotron radiation in a variable photon energy range 135-280 eV at the BEAR beamline at Elettra. In particular the SiOx photoemission peak has been analyzed, selecting only those photoelectrons which originate from the native oxide layer of the silicon wafer. The electron Inelastic Mean Free Path has been derived using a first-order treatment for elastic scattering. This latter is justified by the particular experimental conditions, namely the use of a thin overlayer and a small analyzer acceptance angle. Present IMFP results are compared with previous semi-empirical models, improving our present knowledge of the IMFP curve in amorphous MoO3 and opening new experimental possibilities for accurate measurements of the probing depth in functional materials.
The three-dimensional potential energy surfaces around the equilibrium geometries of OIO & oline;(X1A1) and OIO (X2B1) were calculated with two double hybrid density functionals XYGJ-OS and XDH-PBE0 and three hybrid density functionals B3LYP, MPW1PBE and B97-3 in conjunction with various basis sets. The potential energy surfaces were used in calculations of anharmonic vibrational wavefunctions of OIO & oline;(X1A1) and OIO(X2B1) by virtue of discrete variable representation. Therefrom, the vibrational frequencies including anharmonicity of both states were obtained, and the Franck-Condon factors between these two states were calculated including allowance for anharmonicity and Duschinsky effect. The X2B1 <- X1A1 band of the anion photoelectron spectroscopy of OIO was then simulated using the computed Franck-Condon factors broadened with a Gaussian line shape. Based on the theoretical Franck-Condon factors, a more detailed assignment of the observed vibrational structure of the photoelectron spectrum, which includes the photodetachment from vibrational excited states of OIO & oline;(X1A1) has been proposed. Comparison between the simulated and experimental spectra by iterative FranckCondon analysis procedure has been made, the equilibrium geometrical parameters for OIO anion have been derived to be r(OI)= 1.8508 +/- 0.0003 & Aring; and theta(OIO)= 107.9 +/- 0.3 degrees.
Magnetic circular dichroism in photoemission provides a powerful tool for probing the electronic and magnetic structure of ferromagnets. In the threshold regime, the use of laboratory light sources enables magnetic domain imaging with photoelectron emission microscopy (PEEM), but the achievable magnetic contrast is typically weak, leading to long acquisition times. In this work, we present a theoretical study of contrast enhancement in threshold-photoemission PEEM based on symmetry considerations and relativistic one-step photoemission calculations. We show that surface symmetry imposes specific relations among the fundamental dichroic intensities and the corresponding asymmetries, which can be exploited by momentum selection using an aperture in the PEEM. As a prototype system, we investigate in-plane and perpendicular magnetized Fe(001). Our results demonstrate that sizable magnetic domain contrast can be achieved at low photon energies by selecting appropriate emission directions, providing a practical route toward efficient laboratory-based magnetic domain imaging.
