Ion Energy Dependence Research Articles

Ion energy dependence of helium plasma irradiation effects on the photoelectrochemical properties of tungsten oxide

Abstract Tungsten samples with fuzz nanostructures on the surface were generated using helium plasma with different incident ion energies, and then fuzz tungsten oxide electrodes were prepared by calcination. The photoelectrochemical (PEC) properties and stability of the samples were measured, and the dependence on the incident ion energy was discussed. The mechanism of the fuzz structure to enhance the PEC performance of tungsten oxide was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The results show that fuzzy sample fabricated with higher ion energy has greater PEC performance, which is mainly caused by the increase in active surface area.

SiC and Si detectors comparison for high carbon energy spectrometry

An innovative SiC Schottky junction and a traditional p-n Si surface barrier detector have been compared to detect carbon ions with MeVs kinetic energy. To this, a comparison was performed during Rutherford backscattering spectrometry (RBS) using 2–10 MeV carbon ion beams. The energy resolution and detection efficiency for RBS analysis using the two detectors and their detection electronics are presented.The detector parameters dependencies on the surface passivating layers, ion energy and current dependence, ion penetration depth, detection efficiency, energy resolution, and others are discussed.The comparison of RBS analysis with SiC and Si is investigated highlighting the advantages and disadvantages of using SiC with respect to the traditional Si surface barrier detectors. The two detectors employed for proton, helium and carbon RBS spectrometry of different targets have been also compared on the base of the literature data.

Comparison between conventional Si and new generation of SiC detector for high proton energy spectrometry

A SiC Schottky diode and a Si surface barrier detector have been compared during Rutherford backscattering spectrometry (RBS) using 2–3 MeV proton beams. Both detectors are suited to detect high energetic ions with high-energy resolution for spectroscopic analysis. The correlations between the detector parameters and the surface passivating layers, ion energy and current dependence, ion penetration depth, detection efficiency and energy resolution, are outlined. Comparative RBS analysis performed using SiC and Si detectors has been investigated to highlight the advantages and disadvantages of the use of SiC with respect to the traditional Si junction detector. RBS spectrometry has been carried out using projectiles of proton incident on different targets to analyse their composition and thickness by the detection of the backscattered ions revealed by Si and SiC detectors.

Ultrathin superconducting TaCxN1−x films prepared by plasma-enhanced atomic layer deposition with ion-energy control

This work demonstrates that plasma-enhanced atomic layer deposition (PEALD) with substrate biasing enables the preparation of ultrathin superconducting TaCxN1−x films. By comparing with films grown without substrate biasing, the enhanced ion energies yield a hundredfold reduction in room-temperature resistivity: a comparably low value of 217 μΩ cm is obtained for a 40 nm film. The ion-energy control enables tuning of the composition, counteracts oxygen impurity incorporation, and promotes a larger grain size. Correspondingly, the critical temperature of superconductivity (Tc) displays clear ion-energy dependence. With optimized ion energies, a consistently high Tc around 7 K is measured down to 11 nm film thickness. These results demonstrate the high ultrathin-film quality achievable through PEALD combined with substrate biasing. This process is particularly promising for the fabrication of low-loss superconducting quantum devices.

Monte Carlo simulation of ion kinetics in nitrogen and oxygen plasmas under non-uniform electric field conditions

The kinetics of N4+ and O− ions was numerically studied in nitrogen and oxygen plasmas in a highly non-uniform electric field. Mean ion energy and reaction rate coefficients in a background gas at pressures from 1 to 10 Torr were calculated through a Monte Carlo simulation. The ion characteristics followed the local reduced electric field at high pressures, whereas nonhydrodynamic effects leading to a nonlocal dependence of the mean ion energy and rate coefficients on the field were obtained at low pressures. As a result, the rates of N4+ ion dissociation, electron detachment from O− ions, and charge exchange in collisions between O− and O2 lagged the local field value. The non-local effect on the ion rate coefficients was more profound when the field decreased in space. We suggested a simplified method of describing ion rates in spatially varying electric fields on the basis of the Monte Carlo simulation of these rates for uniform electric field conditions and mean ion energy calculations in non-uniform fields. This method is similar to the local-mean-energy approximation utilized for describing electron swarm parameters in varying electric fields. The results of the simplified method were compared with the results of the direct Monte Carlo simulation.

Electron capture and loss in the scattering of low-energy protons with a C60 monolayer deposited on Cu(111)

Final projectile charge states are experimentally and theoretically analyzed after ${\mathrm{H}}^{+}$ ions collide with a ${\mathrm{C}}_{60}$ monolayer deposited on Cu(111) with an ample range of incoming energies (2--8 keV) in the low-energy regime. The three possible charge states (negative, positive, and neutral) are experimentally measured by using the low-energy ion scattering technique for two different collisional setups: 45\ifmmode^\circ\else\textdegree\fi{} (90\ifmmode^\circ\else\textdegree\fi{}) and 67.5\ifmmode^\circ\else\textdegree\fi{} (67.5\ifmmode^\circ\else\textdegree\fi{}) incoming (exit) angles, relative to the target surface plane, with a fixed backscattering angle of 135\ifmmode^\circ\else\textdegree\fi{}. Experimental ion fraction magnitudes and energy dependence are practically intermediate between that found in pristine Cu(111) and a thick ${\mathrm{C}}_{60}$ film, revealing the influence of the substrate on the final charge state of the projectile. Unlike these previous systems, the positive and negative ions contribute nearly evenly to the total scattered charged particles. On the theoretical side, we applied a first-principles based model that considers the fine details of the surface under analysis and assumes a projectile trajectory corresponding to a single binary collision with the more exposed carbon atoms of the ${\mathrm{C}}_{60}$ molecule. The theoretical and experimental results are independently compared with the already reported cases: ${\mathrm{H}}^{+}$ on a thick ${\mathrm{C}}_{60}$ film, ${\mathrm{H}}^{+}$ on Cu(111), and ${\mathrm{H}}^{+}$ on graphite. A detailed analysis of the electronic surface band structure allows us to draw a conclusion about the relevance of the substrate in the present system and about the aspects to be improved in our theoretical description. The contrast between experimental and theoretical results allows us to infer that trajectories involving ion penetration and multiple scattering events are particularly relevant for the projectile-target charge exchange process studied.

Modeling laser-driven ion acceleration with deep learning

Developments in machine learning promise to ameliorate some of the challenges of modeling complex physical systems through neural-network-based surrogate models. High-intensity, short-pulse lasers can be used to accelerate ions to mega-electronvolt energies, but to model such interactions requires computationally expensive techniques such as particle-in-cell simulations. Multilayer neural networks allow one to take a relatively sparse ensemble of simulations and generate a surrogate model that can be used to rapidly search the parameter space of interest. In this work, we created an ensemble of over 1,000 simulations modeling laser-driven ion acceleration and developed a surrogate to study the resulting parameter space. A neural-network-based approach allows for rapid feature discovery not possible for traditional parameter scans given the computational cost. A notable observation made during this study was the dependence of ion energy on the pre-plasma gradient length scale. While this methodology harbors great promise for ion acceleration, it has ready application to all topics in which large-scale parameter scans are restricted by significant computational cost or relatively large, but sparse, domains.

Ion Species Dependence on the Interfacial Properties of Silicon Homojunctions Bonded Using an Ion Bombardment Treatment

Surfaces of (001) p-type silicon substrates were bombarded with either Ar or Kr ions prior to direct wafer bonding using an EVG© ComBond© high-vacuum wafer-bonding system.1 Previously, we showed that this ion bombardment treatment induces a thin ~nm amorphous region at the bonded interface.2 In this study, we extend upon this previous effort towards a fundamental understanding of this amorphous interfacial region by examining the dependence of the bonded interface’s properties with two different ion species. The ion energies used spanned from a factor of 0.5 to 2.5 times of a baseline energy E0. X-ray reflectivity measurements were performed on single unbonded wafers that were ion bombarded with either Ar or Kr to determine the thickness of the amorphous region as well as its mass density compared to bulk Si. Wafers treated with Ar showed no surface mass density dependence with ion energy, while wafers treated with Kr did show an ion energy dependence. While the Ar treatment reduces the surface density to ~80% of bulk Si density regardless of the energy used, the Kr treatment reduces the surface density to as low as ~70% of bulk Si density at 2.5⋅E0. Furthermore, for a given energy, the Ar treatment resulted in thicker layers than the Kr treatments, which is consistent with SRIM3 simulations because Kr is a heavier species than Ar. Current-voltage measurements were also used to probe the electrical properties of the bonded interfaces. Band structure modeling of the current-voltage measurements revealed that the amorphous region can be modeled with a step barrier that spans the thickness of the amorphous region.References Flötgen, et al., ECS Trans., 64(5), 103 (2014).E. Liao, et al., ECS Trans., 86(5), 55 (2018).F. Ziegler, et al., The Stopping Range of Ions in Solids vol. 1, (1985). Figure 1

Ion Species Dependence on the Interfacial Properties of Silicon Homojunctions Bonded Using an Ion Bombardment Treatment

Direct wafer bonded p-type (001) silicon homojunction structures were prepared with an ion bombardment surface treatment using either Ar or Kr ions prior to bonding in a high-vacuum direct wafer bonding system. The ion energies used spanned from a factor of 0.5 to 5 times of a baseline energy E0 for Ar and 0.5 to 2.5 times for Kr. The ion bombardment surface treatment induces a thin ~nm amorphous region at the Si|Si bonded interface. X-ray reflectivity measurements were performed on ion-bombarded single unbonded wafers. It was found that the Ar treated wafers showed a weak surface mass density dependence with ion energy, while wafers treated with Kr showed a strong ion energy dependence. While the Ar treatment reduces the surface density to ~80% of bulk Si density, the Kr treatment reduces the surface density to as low as ~70% of bulk Si density using an ion energy of 2.5⋅E0. Current-voltage measurements were also used to probe the electrical resistance across the amorphous interfacial region of the bonded structures prepared with Ar ions.

Ion energy and angular distributions in planar Ar/O2 inductively coupled plasmas: hybrid simulation and experimental validation

A hybrid model, which consists of a fluid module, a sheath module and an ion Monte Carlo module, is employed to investigate the dependence of ion energy and angular distributions (IEDs and IADs) on the inductively coupled plasma (ICP) power, pressure, gas ratio, bias power and bias frequency in Ar/O2 discharges. The results indicate that the bimodal distribution appears as bias power increases or bias frequency decreases. Moreover, the low and high energy peaks of IEDs move to higher energy with the rise of bias power and O2 content. Whereas, an opposite tendency is observed with the increase of ICP power and pressure. For IADs, it is clear that a larger percentage of ions incident on the electrode have a smaller deflection angle by increasing bias power or decreasing pressure, and a similar evolution is observed with the decline of bias frequency. Besides, the better collimation of ions is obtained at larger O2 concentration, but ICP power only has little influence on IADs. In order to validate the model, a comparison between the simulated IEDs and those measured by a retarding field energy analyzer has been done, and shows a good agreement. The results obtained in this work could help us to gain more insight into the dependence of IEDs and IADs on the discharge parameters, which is of significant importance in the improvement of the etching rate and anisotropy.

Radial dose distribution model independent of species of incident ions

To understand the physical phenomena caused by heavy ion irradiation, we propose a radial dose simulation model, which is closer to reality than conventional models, and is independent of (without specifying) the species of incident ions. With the aim of disseminating our radial dose simulation results for use in radiology and radiation biology, we create a function to fit these results. Using this fitting function, anyone can calculate the radial dose distributions, which almost reproduce our simulation results, within a few seconds. In this function, incident ion energies up to ∼100 MeV/u and a stopping power up to ∼600 keV/μm are covered. Furthermore, using this model, we discuss the incident ion energy dependence on the radial dose, according to incident ion impact ionization cross-sections.

Tungsten Blister Formation Kinetic as a Function of Fluence, Ion Energy and Grain Orientation Dependence Under Hydrogen Plasma Environment

This work deals with the formation kinetic of tungsten (W) blisters under smooth plasma conditions, i.e. low hydrogen flux and energy in order to analyze the first stages of their formation. In addition, we focus on determining the W grain orientation where blisters grow preferentially. For this purpose, mirror-polished polycrystalline tungsten samples were exposed to hydrogen plasma under fixed hydrogen flux of 2.2 × 1020 m−2 s−1, with a fluence in the range of ~ 1024 m−2, ion energy of ~ 20, 120 and 220 eV, and sample surface temperature of ~ 500 K. The formation of blisters at the surface was investigated using SEM, AFM and EBSD to determine the size, the distribution and the orientation of grain where blisters are formed, respectively. The critical fluence for initiating blisters was established around 2.3 × 1024 m−2. The evolution of blister size distribution and density is discussed as function of fluence and ion energy. At lower ion energy, i.e. 20 eV, only nanoblisters (less than 150 nm) are observed whatever the fluence value (1.5 and 2.3 × 1024 m−2). At higher ion energy i.e. 120 and 220 eV, micrometric (~ few to tens of µm) blisters are observed and their density highly depends on fluence. We show that blisters can also be formed on (001) oriented grains contrarily to previous results from the literature where the (111) orientation seemed more favorable. Such information is of importance for tungsten based fusion tokamak operation and design.

Injected ion energy dependence of SiC film deposited by low-energy SiC3H9+ ion beam produced from hexamethyldisilane

Abstract We mass-selected SiC3H9+ ions from various fragments produced through the decomposition of hexamethyldisilane, and finally produced low-energy SiC3H9+ ion beams. The ion beams were injected into Si(1 0 0) substrates and the dependence of deposited films on injected ion energy was then investigated. Injected ion energies were 20, 100, or 200 eV. Films obtained were investigated with X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. X-ray diffraction and X-ray photoelectron spectroscopy of the substrates obtained following the injection of 20 eV ions demonstrated the occurrence of silicon carbide film (3C-SiC) deposition. On the other hand, Raman spectroscopy showed that the films deposited by the injection of 100 or 200 eV ions included 3C-SiC plus diamond-like carbon. Ion beam deposition using hexamethyldisilane-derived 20 eV SiC3H9+ ions is an efficient technique for 3C-SiC film formation on Si substrates.

Effects of He ion energy on blistering characteristics of Si sequentially implanted with H and He ions in various sequences

As compared to the conventional smart-cut technology based on single H ion implantation, sequential implantation of H and He ions has been demonstrated to be effective in reducing the implantation fluence and the thermal budget needed for Si layer splitting process. However, the sequential implantation method involves complicated process parameters such as ion energy and implantation sequence. The purpose of this study is to clarify the dependence of He ion energy on Si blistering characteristics by sequential implantation of H and He ions into Si in various sequences. The accelerated energy of H ions was fixed at 40 keV, while that of He ions was changed to 30, 50, and 70 keV. Both the implantation fluences of H and He ions were 1 × 1016 cm−2. The non-isothermal and isothermal annealing methods in combination with an in-situ optical microscopy (OM) detection system were adopted to determine the threshold temperatures and the onset times for blister and crater formation as well as to examine the thermal evolution of blisters and craters. The results revealed that the threshold temperatures for blister and crater formation are highly correlative to the He ion energy and implantation sequence. Higher He ion energy is preferable to blistering for the specimens first implanted with He ions, but the opposite is true for the reverse implantation sequence. This statement can be also supported by the activation energy levels required for blister and crater formation obtained from kinetics analysis. In addition, the variation of hydrogenated complexes induced by sequential implantation and annealing can be evidently identified from the Raman spectra, showing a noticeable transformation of H-related defect complexes from VH3 to Si(100):H bonding configuration due to the emergence of blisters and craters.

Comparison of optimized ion acceleration from thin foils and low-density targets for linearly and circularly polarized laser pulses

A multiparameter comparative analysis of ion acceleration with linearly and circularly polarized relativistically intense laser pulses for solid-density thin foils and low-density planar targets was performed using 3D particle-in-cell (PIC) simulations. Ion acceleration optimization was studied with 3D PIC MANDOR over the laser energy range of three orders of magnitude from three hundred millijoules to three hundred joules in a femtosecond pulse. The optimum target thickness and density was found for a given energy of the laser pulse corresponding to the maximum energy of the accelerated ions. This allows deriving a dependence of the maximum ion energy on laser energy for the optimized solid or low-density targets. The advantage of a circularly polarized laser pulse for generating the most energetic ions was demonstrated, which happens for the regimes of volumetrically heated semitransparent solid foils (directed Coulomb explosion) and of synchronized ion acceleration by slow light from low-density targets. The dependence of the maximum ion energy on laser energy for the optimized targets and both linearly and circularly polarized femtosecond pulses demonstrates a sharper-than-square-root increase.

Highly-ordered ripple structure induced by normal incidence sputtering on monocrystalline GaAs (001): ion energy and flux dependence

Low energy ion beam sputtering induced nanostructure formation on GaAs (001) surfaces at elevated temperature and at normal ion incidence has been studied for different ion energy and flux of the incident Ar+. Well-ordered nanoripples are found to develop, whose wave-vector is oriented along 〈110〉 crystallographic direction. The ripple structure is found to coarsen with ion energy, while it remains invariant with the ion flux. The evolution of the ripples can be attributed to the biased diffusion of vacancies arising from Ehrlich–Schwoebel barrier.

Energy and angular dependence of single event upsets in ESA SEU Monitor

The new generation ESA SEU Monitor is first applied to beam verification of Beijing HI-13 Tandem accelerator according to the popularization need of Europe Space Agency and at the desire of contrast of domestic acceleraor with international accelerator. Heavy ion single event cross section of ESA SEU Monitor obtained at HI-13 is compared with those from European facilities. Beam homogeneity is also analyzed based on the SEU physical bitmap. The accuracy of heavy ion beam monitoring technique at HI-13 accelerator is verified. Through combining the heavy ion testing result with the data from the other test sites, it can be observed that the differences between SEU cross sections with different heavy ion energies of the same LET value can reach 1-3 orders of magnitude in the sub-threshold zone of single event upset cross section curve below the direct ionization LET threshold. The geometrical structure, critical charge and collection efficiency of sensitive volume are constructed on the basis of testing data and process information. The physical mechanism of energy effect on single event upsets in ESA SEU Monitor is revealed through using the Monte-Carlo calculation. Nuclear reactions between incident heavy ions and material atoms can account for single event upsets below the direct ionization LET threshold. The differences in nuclear reaction type and cross section between the diferent energy heavy ions and material atoms are the root cause of the difference among heavy ion SEU cross sections with different energies at the same LET value. On the other hand, SEU bitmap nonuniformity among different blocks in memory array and different orientation dices in ESA SEU Monitor is first reported when the heavy ion is incident at a tilting angle at the low LET value. The analysis of device layout and calculation verification can account for this phenomenon. The material of interlayer dielectric with the tilting ion passing through is different when heavy ion reaches the sensitive volume of memory blocks with different data. This leads to the difference between efficient LET values inside the sensitive volume for different data blocks. Eventually the sensitivity difference in single event upset among blocks with different data occures. The applications of ESA SEU Monitor in beam calibrating, tuning of domestic accelerator and single event effect test can be broadened further. Prediction method of space single event upset rate including heavy ion energy dependence and special angular dependence based on full-physical simulation should be developed in the future.

Sub-LET Threshold SEE Cross Section Dependency With Ion Energy

This study focuses on the ion species and energy dependence of the heavy ion SEE cross section in the sub-LET threshold region through a set of experimental data. In addition, a Monte Carlo based model is introduced and applied, showing a good agreement with the data in the several hundred MeV/n range while evidencing large discrepancies with the measurements in the 10-30 MeV/n interval, notably for the Ne ion. Such discrepancies are carefully analyzed and discussed.

Study of [formula omitted]/[formula omitted] RYIED in closed and open shell Rare Earth Elements

Relative Yield Ion Energy Dependence (RYIED) was observed, named and reported as phenomenological evidence in 2005 (Reis et al., 2005). Since then, it was observed in transitions to the same subshell, and plausible explanations for the physics behind the phenomena have been proposed. In this work we present experimental evidence of the RYIED effect on the most inner transition possible in two Rare Earth Elements (REE), namely variations in the intensity ratio of Kα2/Kα1 X-rays from Tm and Yb irradiated under different conditions. These REE are particularly interesting to start with since Yb has an electronic configuration where all the subshells are completely filled, whilst Tm misses one electron in the 4f subshell. Ultrapure oxides of each element were irradiated using proton beams having energies in the range of 0.9–3.6MeV, in steps of 100keV. Spectra were collected using the CdTe detector of the HRHE-PIXE set-up of C2TN and analysed using the DT2 code. Finally, the vanishing of the effect upon charging up of the target has been observed and will be discussed.

Experimental investigation of plasma cloud scattering initiated by an accelerated electron beam

The parameters for the charged particle flow of a plasma cloud (PC) explosion initiated by an electron beam have been measured. Two types of PCs were investigated: 1) PC with a free boundary and 2) PC restricted by electrodes. It was established that the basic particle flow parameters for such a plasma explosion coincide in common with the parameters of accelerated particle flow of different types of vacuum discharges. Energy spectra have several maxima. There is a dependence of ion energy on the ion charge state. PC is scattered in a wide spatial angle. The geometry of the propagation volume affects the energy spectrum of ions.