Electron Energy Loss Distributions Research Articles

Comparison of the secondary electrons produced by proton and electron beams in water

The secondary electrons produced in water by electron and proton beams are compared with each other. The total ionization cross section (TICS) for an electron impact in water is obtained by using the binary-encounter-Bethe model. Hence, an empirical equation based on two adjustable fitting parameters is presented to determine the TICS for proton impact in media. In order to calculate the projectile trajectory, a set of stochastic differential equations based on the inelastic collision, elastic scattering, and bremsstrahlung emission are used. In accordance with the projectile trajectory, the depth dose deposition, electron energy loss distribution in a certain depth, and secondary electrons produced in water are calculated. The obtained results for the depth dose deposition and energy loss distribution in certain depth for electron and proton beams with various incident energies in media are in excellent agreement with the reported experimental data. The difference between the profiles for the depth dose deposition and production of secondary electrons for a proton beam can be ignored approximately. But, these profiles for an electron beam are completely different due to the effect of elastic scattering on electron trajectory.

Intensity distribution analysis of cathodoluminescence using the energy loss distribution of electrons

We present an intensity distribution analysis of cathodoluminescence (CL) excited with a focused electron beam in a luminescent thin film. The energy loss distribution is applied to the developed analysis method in order to determine the arrangement of the dipole locations along the path of the electron traveling in the film. Propagating light emitted from each dipole is analyzed with the finite-difference time-domain (FDTD) method. CL distribution near the film surface is evaluated as a nanometric light source. It is found that a light source with 30nm widths is generated in the film by the focused electron beam. We also discuss the accuracy of the developed analysis method by comparison with experimental results. The analysis results are brought into good agreement with the experimental results by introducing the energy loss distribution.

Interaction of low energy electrons with iron surface: Energy loss and penetration depths

SynopsisWe present Monte Carlo simulation of low energy electrons backscattered from iron (Fe) surface. We take into account both elastic and inelastic collisions during the simulation. In our simulations the primary electron energy is 150 eV and the incidence angle of the electron beam with respect to the surface is varied between 1° and 90 °. The backscattered electron energy loss distributions for primary and as well for secondary electrons and the distribution of maximum electron penetration depths in the Fe sample were calculated using only the bulk and also the surface dielectric function.

Interaction of low energy electrons with platinum surface

We present Monte Carlo simulation of low energy electrons backscattered from platinum (Pt) surface. We take into account both elastic and inelastic collisions during the simulation. For the case of the elastic scattering of electrons by Pt atoms we use the static field approximation with non-relativistic Schrödinger partial wave analysis. For the case of inelastic scattering we use the dielectric response formalism. In our simulations the primary electron energy is 250eV and the incidence angle of the electron beam with respect to the surface is varied between 1° and 90°. The backscattered electron energy loss distributions for primary and as well for secondary electrons and the distribution of maximum electron penetration depths in the Pt sample were calculated using only the bulk and also the surface dielectric function. We found that the maximum attained depth of the electrons is around 20Å, i.e. the electrons are at the vicinity of the surface. Therefore we expect that the experimental data will be close to our simulation using surface-excitations modes.

Pulse height distribution of signals produced by exposing a thin GEM chamber to beta rays from an Sr-90 source

Researchers at Changwon National University’s Radiation Detector Development Laboratory(RDD) fabricated a single-channel double-GEM(gas electron multiplier) chamber and measured the pulse height distribution of signals produced by exposing the chamber to an Sr-90 source provided by the Korea Research Institute of Standards and Science(KRISS). A beta-ray electron incident on the GEM chamber ionizes gaseous molecules in the drift region of the chamber by means of electromagnetic interactions. After the leased electrons are amplified by electron avalanches in the GEM stages, the multiplied electrons go from the lowest GEM foil toward the anode of the chamber and induce one signal pulse, corresponding to the incident electron, on the readout pad. The charge signal distribution measured during Sr-90 radioactive source irradiation was compared with the simulation done by using a Landau probability distribution. The energy loss distribution of beta-ray electrons, which deposited part of their energy in a thin GEM chamber while traversing gases within the drift region of that chamber, was in good agreement with the calculation of the Landau probability distribution. The pulse height distributions for energy losses of beta-ray electrons incident on the chamber due to Sr-90 disintegrations were observed in order to select a suitable gas mixture for the chamber. The ratios of the Ar/CO2 gas were 75/25, 80/20, 85/15, and 90/10.

Electron scattering from pyrimidine

Electron scattering from pyrimidine (C4H4N2) was investigated over a wide range of energies. Following different experimental and theoretical approaches, total, elastic and ionization cross sections as well as electron energy loss distributions were obtained.

Interaction model for electron scattering from ethylene in the energy range 1–10 000 eV

We present new experimental electron energy loss distribution functions for ethylene (C2H4) measured with two different apparatus (Liège and Madrid) in different incident electron energy ranges. Theoretical cross sections for electron scattering from C2H4 were calculated using the screening-corrected additivity rule (IAM-SCAR) method. Through a critical comparison of our new data and existing results from other groups, we obtain a self-consistent set of recommended interaction cross section values and energy loss spectra. Finally, electron tracks in C2H4 are simulated with our Low Energy Particle Track Simulation (LEPTS) in order to demonstrate the efficacy of our recommended data.

Stopping power for electrons in pyrimidine in the energy range 20–3000 eV

In this work, we present new experimental electron energy loss distribution functions for pyrimidine (C4H4N2) measured for the incident energy range 30–2000eV. Theoretical total and elastic cross sections for electron scattering from pyrimidine were calculated using the screening-corrected additivity rule (IAM-SCAR) method. Based on the mean energy loss observed in the experiment and the theoretical integral inelastic cross section, the stopping power for electrons in pyrimidine is calculated in the energy range 20–3000eV.

Electron scattering from tetrahydrofuran

Electron scattering from Tetrahydrofuran (C4H8O) was investigated over a wide range of energies. Following a mixed experimental and theoretical approach, total scattering, elastic scattering and ionization cross sections as well as electron energy loss distributions were obtained.

Energy loss of electrons backscattered from solids: measured and calculated spectra for Al and Si

Electron energy loss distributions relative to Al and Si are calculated for primary electron energies ranging from 500 eV to 2000 eV under the assumption that experimental spectra arise from electrons undergoing a single large‐angle elastic scattering event (so‐called V‐type trajectories). The method used to calculate the spectra is based on the combination of the Chen and Kwei dielectric formalism with the V‐type trajectory modeling. Good agreement is found between calculated and measured spectra. Copyright © 2012 John Wiley & Sons, Ltd.

Electron–methane interaction model for the energy range 0.1–10 000 eV

Electron interaction cross sections with methane have been collected from literature in order to recommend an extensive data set ranging from 0.1–10 000 eV. We have calculated total and elastic cross sections. Complementary experimental electron energy loss distributions covering a wide energy range (20–3000 eV) were measured using two different experimental setups and are here presented for the first time. Bringing together these new contributions and existing information, an interaction model at the molecular level for electrons in CH 4 is developed in the form of a Monte Carlo simulation. Finally, we use this to calculate the stopping power of methane and compare it with tabulated data provided by the NIST database.

Reconstruction of electrons with the Gaussian-sum filter in the CMS tracker at the LHC

The bremsstrahlung energy loss distribution of electrons propagating in matter is highly non-Gaussian. Because the Kalman filter relies solely on Gaussian probability density functions, it is not necessarily the optimal reconstruction algorithm for electron tracks. A Gaussian-sum filter (GSF) algorithm for electron reconstruction in the CMS tracker has therefore been developed and implemented. The basic idea is to model the bremsstrahlung energy loss distribution by a Gaussian mixture rather than by a single Gaussian. It is shown that the GSF is able to improve the momentum resolution of electrons compared to the standard Kalman filter. The momentum resolution and the quality of the error estimate are studied both with a fast simulation, modelling the radiative energy loss in a simplified detector, and the full CMS tracker simulation.

Monte Carlo simulation of electron transmission through the scattering masks with angular limitation for projection electron lithography

We calculated electron energy loss and angular distributions for electrons transmitted through masks for electron projection lithography by a Monte Carlo (MC) simulation method. After comparing the improved continuous slowing down approximation model, the direct MC model, and the intensive direct MC model, the last model was used. The energy loss distributions calculated by the latter two models are much better than by the first model and the intensive direct MC model can be applied to more materials than the direct MC model. The effect of mask thickness on energy loss, transmission, and contrast was analyzed. We found that, for a W/Cr/Si3N4 mask, the thicker the scattering layer the wider the angular distribution, the lower the transmission, and the higher the contrast. But the thickness of the membrane Si3N4 layer has less effect on the contrast.

Electron Energy Loss Distributions in Solid and Gaseous Hydrocarbons

The dipole oscillator strength distributions for solid and for gas phase cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene were constructed from experimentally derived optical constants and from atomic X-ray absorption cross sections. Monte Carlo simulations of the energy loss by electrons of initial energy from 10 keV to 1 MeV in these media were performed using cumulative inelastic cross sections obtained from a formulation incorporating the constructed dipole oscillator strength distributions. In the solid phase, the energy loss distributions, the most probable energy losses, and the mean energy losses for electrons show little effect due to the conjugation of $pi bonds. However, there are large differences between the gases, and there is a considerable effect due to condensation. The most probable and the mean energy losses for 1 MeV incident electrons in solid cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene are in the ranges 22-24 and 47-48 eV, respectively. Comparison with data for water suggests that the values for the solid phases of hydrocarbons are acceptable approximations for the liquid phase. Density normalized stopping powers, inelastic mean free paths, and ranges for electrons in the various hydrocarbons are also presented. 36 refs., 4 figs., 7 tabs.

Electron Energy-Loss Distributions in Solid, Dry DNA

Experimentally derived optical constants and X-ray attenuation cross sections were used to construct the complete dipole oscillator strength distribution for solid, dry DNA. Monte Carlo simulations of the energy loss by electrons of initial energy 5 keV to 1 MeV in DNA were performed using cumulative inelastic cross sections obtained from a formulation incorporating the constructed dipole oscillator strength distribution. The energy-loss distribution, the most probable energy loss and the mean energy loss for electrons in DNA are compared to those for liquid water, gaseous water and gaseous hexane. For the most part, the calculations show that electron energy loss in DNA is very similar to that in liquid water; however, it is quite different from both gaseous water and gaseous hexane. The mean energy losses for a 1 MeV incident electron in DNA, liquid water, gaseous water and gaseous hexane are 57.9, 56.8, 50.9 and 38.4 eV, respectively. The large differences found between the predictions for DNA and for the gaseous media bring into serious question calculations of radiation-induced damage in DNA which make use of cross sections for gaseous media. Stopping powers and continuous-slowing-down approximation ranges for the media for electrons are also presented.

Formation of complex features using electron-beam direct-write decomposition of palladium acetate

A focused electron beam has been used to selectively decompose thin films of palladium acetate, (Pd–Ac), resulting in the formation of ≤50 nm wide conductive Pd-rich features. The formation of features from various film thicknesses of Pd–Ac has been investigated using a wide range of electron energies. Monte Carlo simulations of electron energy loss distributions in Pd–Ac films were calculated over a wide range of film thicknesses and electron energies. The Monte Carlo calculations were used to predict the volume over which the energy of the electron beam is deposited within the films. Thin conductive wires having profiles from high aspect ratio to almost circular cross sections produced by varying the electron beam energy were in agreement with the Monte Carlo predictions. Complex multilayer Pd–Ac features were then fabricated by performing overlapping exposures of Pd–Ac films with differing electron beam energies.

A study of the order of the π* temporary anion states of 1,4-cyclohexadiene by electron scattering

The symmetries of the two low-lying π* temporary anion states of 1,4-cyclohexadiene are studied by electron energy loss and angular distribution measurements. Analysis of the vibrational modes excited by the resonances and the angular distribution of electrons exciting a totally symmetric vibrational mode provide two independent means to confirm that the 2A u anion state lies below the 2B 3g state.

Spectral transformation of EXELFS data — NiO on Ni(100) and Ni(110)

Extended electron energy loss fine structure (EXELFS) spectra have been obtained from the K-level of oxygen in NiO films grown on both the Ni(100) and Ni(110) surfaces. The spectra indicate that the oxide films grown on both surfaces have Ni-O bond lengths of 2.08 Å, identical to those of bulk NiO. These analyses agree with previous measurements on the Ni(100) surface. As in previous experiments the actual measurements made is of N( E) rather than direct measurement of the electron energy loss distribution N( E). The EXELFS spectra from these two surfaces are used to illustrate the influence of this collection scheme on the radial distribution function obtained by Fourier transformation of the raw data. To obtain the direct analog of the radial distribution function found from the EXAFS experiment one must either resort to spectral integration or appropriate scaling of the distribution function found from the EXELFS experiment.

Spectral Transformation of Exelfs Data and a Structural Examination of Nitrogen on Cu(100) and Cu(110) Surfaces

ABSTRACTEXtended Electron Energy Loss Fine Structure (EXELFS) spectra have been obtained above the K-edge of nitrogen atoms adsorbed on Cu. The radial distribution functions obtained from the fine structure indicate N-Cu bond lengths of 1.84(±.03) Å and 1.81(±.03) Å for nitrogen on the Cu(100) and Cu(110) surfaces respectively. As in previous EXELFS measurements, the actual measurements made are of N"(E) rather than direct measurement of N(E), the electron energy loss distribution. The EXELFS spectra from these two surfaces are used to illustrate the influence of this collection scheme on the radial distribution function obtained by Fourier transformation of the raw data. To obtain the direct analog of the radial distribution function found from the EXAFS experiment one must either resort to spectral integration or appropriate scaling of the distribution function found in the EXELFS experiment.

Kilovolt electron energy loss distribution in Si

Using the electron-beam-induced barrier currents and the Monte Carlo simulation methods it was possible to determine the depth-dose function as well as the distribution function of the generation source for electron-hole pairs perpendicular to the injection direction. The depth-dose function was compared with results obtained by Everhart and Hoff. By fitting the simulated barrier current profile to the measured one the authors could estimate the relatively small width of the space charge region of the p-n junction employed for the measurements. Furthermore, the spatial dose distribution of Si was described in an analytic approximation of the Monte Carlo simulation using two Gaussian functions concerned with the spreading of the penetrating electron beam and the diffusion of the primary electrons within the target, respectively. This approximation was based on treatments of the scattering process of the primary electrons given by Bethe and co-workers, Bothe and Archard.