The energy loss functions (ELFs) of Fe and Ni have been derived from measured reflection electron energy loss spectroscopy (REELS) spectra by a reverse Monte Carlo analysis in our previous work. In ...this work, we present further improvements of ELFs for these metals. For Fe, we have updated ELFs at primary electron energies of 2 keV and 3 keV in a wider photon energy region (0-180 eV) with a better accuracy, which is verified by sum rules. Regarding to Ni, we supplement the ELF at primary energy of 5 keV and we also improve the data accuracy at 3 keV. Applying these new and more accurate ELFs we present the optical constants and dielectric functions for the two metals. The improvements were highlighted by comparing our present results with the previous data.
Experimental data are presented for low-energy singly charged ion transport between two insulating parallel plates. Using a beam intensity of approximately 20 pA, measurements of the incoming and ...transmitted beams provide quantitative temporal information about the charge deposited on the plates and the guiding probability. Using a smaller beam intensity (~ 1 pA) plate charging and discharging properties were studied as a function of time. These data imply that both the charge deposition and decay along the surface and through the bulk need to be modeled as acting independently. A further reduction of beam intensity to ~ 25 fA allowed temporal imaging studies of the positions and intensities of the guided beam plus two bypass beams to be performed. SIMION software was used to simulate trajectories of the guided and bypass beams, to provide information about the amount and location of deposited charge and, as a function of charge patch voltage, the probability of beam guiding and how much the bypass beams are deflected plus to provide information about the electric fields. An equivalent electric circuit model of the parallel plates, used to associate the deposited charge with the patch voltage implies that the deposited charge is distributed primarily on the inner surface of the plates, transverse to the beam direction, rather than being distributed throughout the entire plate.
Energy loss function of samarium Yang, T F; Zeng, R G; Yang, L H ...
Scientific reports,
03/2023, Volume:
13, Issue:
1
Journal Article
Peer reviewed
Open access
We present a combined experimental and theoretical work to obtain the energy loss function (ELF) or the excitation spectrum of samarium in the energy loss range between 3 and 200 eV. At low loss ...energies, the plasmon excitation is clearly identified and the surface and bulk contributions are distinguished. For the precise analysis the frequency-dependent energy loss function and the related optical constants (n and k) of samarium were extracted from the measured reflection electron energy loss spectroscopy (REELS) spectra by the reverse Monte Carlo method. The ps- and f-sum rules with final ELF fulfils the nominal values with 0.2% and 2.5% accuracy, respectively. It was found that a bulk mode locates at 14.2 eV with the peak width ~6 eV and the corresponding broaden surface plasmon mode locates at energies of 5-11 eV.
We present a detailed analysis and comparison of four models describing the extension of the electron-energy loss function from the optical limit of q→0 into the (q,ω) plane to obtain the bulk and ...surface terms of differential inverse inelastic mean free paths. We found that the best model that describes accurately and times efficiently the calculation of the energy loss function of free-electron-like materials is the combination of the Penn algorithm Phys. Rev. B 35, 482 (1987) with the Ritchie-Howie method Philos. Mag. 36, 463 (1977). Applying this model in our reverse Monte Carlo method, we determined, with high-precision, electron-energy loss functions of silicon and germanium based on the theoretical analysis of the high-energy resolution reflected electron energy loss spectroscopy (REELS) spectra, measured at 3, 4, and 5 keV incident electron energies. The refractive index n , the extinction coefficient k , and the complex dielectric function (ɛ = ɛ1 + iɛ2) were calculated from the obtained energy loss function in a wide energy loss range of 0–200 eV. The accuracy of the obtained results is justified with various sum rules. We found that the calculated optical data of Si and Ge fulfill the sum rules with an average accuracy of 0.11% or even better. Therefore, the use of these optical data in materials science and surface analysis is highly recommended for further applications.
•In our recent work we present the combined experimental and theoretical investigations of optical properties and excitation energies of metallic iridium in the energy range between 2 and 200 eV.•The ...high accuracy of the obtained results is justified with the ps- and f-sum rules.•Using the derived ELF the inelastic mean free paths of Ir were calculated from 1 eV up to 10 keV.•Moreover, we identified for the first time in the optical data the 5p3/2, 4f5/2 and 4f7/2 shell excitations of the solid Ir sample.
We present the combined experimental and theoretical investigations of optical properties and excitation energies of metallic iridium. The reflected energy loss spectroscopy (REELS) spectra of polycrystalline Ir were measured with a cylindrical mirror analyzer in UHV conditions at primary energies of 500, 1000 and 2000 eV. The energy loss function (ELF) and thereby the refractive index n and the extinction coefficient k were calculated from these REELS spectra in the loss energy range of 2–200 eV by applying our reverse Monte Carlo method. The high accuracy of the obtained results is justified with the ps- and f-sum rules. Using the derived ELF the inelastic mean free paths of Ir were calculated from 1 eV up to 10 keV. Moreover, we identified for the first time in the optical data the 5p3/2, 4f5/2 and 4f7/2 shell excitations of the solid Ir sample.
We present an absolute extraction method of optical constants of metal from the measured reflection electron energy loss spectroscopy spectra with the help of a recently developed reverse Monte Carlo ...technique. The method is based on a direct physical modeling of electron transportation with an optimization procedure of the energy loss function (ELF). The optical constants and the electron inelastic mean free path were obtained after verifying the accuracy of the derived ELF with the f- and ps-sum rules. This approach provides a valid and universal tool to investigate intrinsic properties of metals by using the electron energy loss spectroscopy technique.
We use the classical Monte Carlo transport model of electrons moving near the surface and inside solids to reproduce the measured reflection electron energy-loss spectroscopy (REELS) spectra. With ...the combination of the classical transport model and the Markov chain Monte Carlo (MCMC) sampling of oscillator parameters the so-called reverse Monte Carlo (RMC) method was developed, and used to obtain optical constants of Ni in this work. A systematic study of the electronic and optical properties of Ni has been performed in an energy loss range of 0–200eV from the measured REELS spectra at primary energies of 1000eV, 2000eV and 3000eV. The reliability of our method was tested by comparing our results with the previous data. Moreover, the accuracy of our optical data has been confirmed by applying oscillator strength-sum rule and perfect-screening-sum rule.
The interaction between Be4+ and hydrogen atom is studied using the three-body classical trajectory Monte Carlo method (CTMC) and the quasiclassical trajectory Monte Carlo method of Kirschbaum and ...Wilets (QTMC-KW). We present total cross sections for target ionization, target excitation, and charge exchange to the projectile bound states. Calculations are carried out in the projectile energy range between 10 and 1000 keV/au, relevant to the interest of fusion research when the target hydrogen atom is in the ground state. Our results are compared with previous theoretical results. We found that the classical treatment describes reasonably well the cross sections for various final channels. Moreover, we show that the calculations by the QTMC-KW model significantly improve the obtained cross sections.
•The study presents electron inelastic mean free path (IMFP) and stopping power data for hafnium dioxide using the relativistic dielectric response theory. This research provides valuable insights ...into the interaction of electrons with HfO2.•The latest energy loss function (ELF) with a broad energy loss range (up to 200 eV), derived from the reverse Monte Carlo method, has been employed for the calculation.•Two algorithms, namely the full Penn algorithm (FPA) and the super-extended Mermin algorithm (SMA), were employed to expand the optical energy loss function. The influence of the band gap on the results has been considered, particularly in the low electron energy region.
We present inelastic mean free path (IMFP) and stopping power data of the hafnium dioxide applying the relativistic dielectric response theory. The energy loss function (ELF) derived from reflection electron energy loss spectroscopy spectrum with the reverse Monte Carlo method was used for the first time to obtain the IMFP and stopping power of HfO2. The probability of the energy loss is determined by the dielectric response function εq,ω as a function of the frequency ω and the wavenumber q of the electromagnetic disturbance. Two algorithms, namely the full Penn algorithm (FPA) and the super-extended Mermin algorithm (SMA), were employed to expand the optical energy loss function, Im-1/ε0,ω, into the q,ω-plane. The results indicate that the IMFP and the stopping power obtained by using both algorithms are consistent at high electron energies, but show differences at low electron energies (less than ∼ 70 eV). This discrepancy arises from the consideration of the finite plasmon lifetimes effect in the SMA model, while it is neglected in the FPA model. Additionally, we observed that the band gap has a significant influence on the IMFP and the stopping power at low electron energies. Typically, the inclusion of the band gap leads to an increase in the IMFP, because transition channels with energies larger than E-Eg-Ev are prohibited.
PDF
