Elastic Recoil Detection Technique Research Articles

Sputtering and structural modifications induced in silicon dioxide (SiO2) thin films under (10–40 MeV) Auq+ heavy ion irradiation

Surface sputtering and structural modifications induced in silicon dioxide thin films (SiO2/Si) deposited on silicon substrates and irradiated by swift (10–40 MeV) heavy Auq+ (q = +4, +6, +7, and +9) ions were investigated by grazing‐incidence X‐ray diffraction (GIXRD) spectroscopy, Rutherford backscattering (RBS) spectrometry and time‐of‐flight elastic recoil detection (ToF‐ERDA) technique. The GIXRD analysis of the as‐deposited and irradiated samples revealed increasing structural modifications of the SiO2 thin films under Auq+ ion impacts with increasing ion‐beam energy. The changes consisted of decreased grain sizes with increased strain accompanied by a phase transformation from crystalline to amorphous films. RBS analysis showed a decrease in the mean stoichiometric (O/Si) ratio from (2.2 ± 0.1) to (1.7 ± 0.1), due to preferential sputtering of oxygen, as the incident ion energy increased. The obtained RBS‐results were then completed by those of ToF‐ERDA analysis technique using a 40 MeV Au9+ heavy ion beam. The preferential sputtering yield ratios (YSi/YO) were determined experimentally both versus electronic stopping power and ion fluence. The obtained results were then compared to numerical values derived from the inelastic thermal spike (i‐TS) model, Sigmund's analytical formula and SRIM simulation code. A good agreement was observed between the measured preferential sputtering data and the i‐TS calculated values, when considering both nuclear elastic and electronic inelastic collision mechanisms. Besides, a close correlation is observed between the electronic stopping power dependent measured sputtering yields and the XRD peak intensity degradation per unit fluence. These observations suggest that the same mechanism of MeV heavy ion‐irradiation induced extended atomic disordering, occurs both in the case of structural modifications and surface sputtering. Finally, the obtained experimental results are discussed on the basis of the i‐TS model.

Behaviors of H, D, and Li in water-soaked LATP solid electrolytes at room temperature

The elastic recoil detection (ERD) technique was employed to measure the depth distributions of lithium (Li) and hydrogen isotopes (H and D) near the surface of NASICON-type LATP (Li1+xAlxTi1−x/2Ge1−x/2P3−yO12) solid electrolytes soaked in water (H2O and D2O) at room temperature for 1–80 days. The ERD spectra demonstrated H and D absorption on the LATP surface by H2O and D2O soaking and Li segregation to the top surface. Moreover, the field emission-scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) images, and atomic absorption spectrophotometry (AAS) indicated the formation of numerous black substances with approximately 0.5 × 3.0 µm2 in area and < ∼50 nm in thickness and the dissolution of Li in water. Li migration from the bulk to the surface may occur through the reactions of H2O and D2O with Ge, subsequently leading to H and D trapping at Li substitutional sites.

Dynamic behavior of Li depth profiles in solid state Li ion battery under charging and discharging by means of ERD and RBS techniques

Change in Li depth profiles of Ti/NbO/LiPON/LMO/Ti and Ti/LMO/LiPON/NbO/Ti (NbO=Nb2O5, LiPON=Li3.3PO3.8N0.2, LMO = LiMn2O4) batteries prepared on Si substrate on one cycle of charging and discharging has been in-situ measured from both Ti/NbO and Ti/LMO sides by ERD (elastic recoil detection analysis) and RBS (Rutherford backscattering spectroscopy) techniques with 9 MeV O+4 ion beam, in order to understand Li transport between NbO to LMO. It is found that on over-charging of the Ti/NbO/LiPON/LMO/Ti battery Li charged in NbO diffuses into top Ti film, but on the Ti/LMO/ LiPON/NbO battery Li does not diffuse into bottom Ti film, but returns back to LMO, reacts with top Ti film and segregates at the Ti surface. The difference in Li transport in both batteries is discussed in terms of the difference in Fermi levels at the interfaces of LMO/Ti and NbO/Ti on the Si substrate.

Change in Li depth profiles of Au/LCO/mixed LATP-LAGP/Pt battery under discharging studied by ion beam analysis techniques with 9 MeV O4+ ions

Li depth profiles in Au/LCO/mixed LATP-LAGP/Pt battery (mixed LATP-LAGP (LATP/LAGP) = Li1+X+YAlYTi2−YGeXP3−XO12, LCO = LiCoO2) under discharging by biasing Pt to Au at earth potential, have been measured from both Au and Pt surfaces by means of reflection elastic recoil detection (ERD) and Rutherford backscattering spectrometry (RBS) techniques with 9 MeV O4+ ions. Ge and Ti compositions of a mixed LATP-LAGP electrolyte and thickness of LCO were determined from RBS spectrum for the as-prepared specimen, where Y and X in LATP were estimated to be 0.84 and 1.27, respectively. On charging at 2.4 V for 25 min, Li composition in LCO measured from the Au surface by ERD was reduced down to ~0.3 and hereafter on discharging at 0.5 V for 25 min the composition was not enriched, but contrary was further reduced to 0.2. However, by successive discharging at 1.0, 1.5 and 2.2 V for 50 min the composition was enriched. On the other hand, it was found from the Pt surface that Li charged in the electrolyte near Pt by biasing at 2.4 V for 20 min was reduced by discharging at 1.0 V for 20 min. By further discharging for 20 min Li was not reduced, but contrary was enriched. Both anomalous transports of Li under discharging are discussed in terms of diffusion of Li atoms in the counter direction to the biasing which is caused by the transport fraction of Li ions in the electrolyte less than unity.

Luminescence of silicon nanoparticles from oxygen implanted silicon

Oxygen with a kinetic energy of 20 keV is implanted in a silicon wafer (100) at different fluences, followed by post-implantation thermal annealing (PIA) performed at temperatures ranging from 1000 to 1200 °C, in order to form luminescent silicon nanoparticles (SiNPs) and also to reduce the damage induced by the implantation. As a result of this procedure, a surface SiOx layer (with 0 < x < 2) with embedded crystalline Si nanoparticles has been created. The samples yield similar luminescence in terms of peak wavelength, lifetime, and absorption as recorded from SiNPs obtained by the more conventional method of implanting silicon into silicon dioxide. The oxygen implantation profile is characterized by elastic recoil detection (ERD) technique to obtain the excess concentration of Si in a presumed SiO2 environment. The physical structure of the implanted Si wafer is examined by grazing incidence X-ray diffraction (GIXRD). Photoluminescence (PL) techniques, including PL spectroscopy, time-resolved PL (TRPL), and photoluminescence excitation (PLE) spectroscopy are carried out in order to identify the PL origin. The results show that luminescent SiNPs are formed in a Si sample implanted by oxygen with a fluence of 2 × 1017 atoms cm−2 and PIA at 1000 °C. These SiNPs have a broad size range of 6–24 nm, as evaluated from the GIXRD result. Samples implanted at a lower fluence and/or annealed at higher temperature show only weak defect-related PL. With further optimization of the SiNP luminescence, the method may offer a simple route for integration of luminescent Si in mainstream semiconductor fabrication.

High resolution Li depth profiling of solid state Li ion battery by TERD technique with high energy light ions

Abstract Li depth profiles in Au/Si/LiPON/LCO/Au (LCO = LiCoO2, LiPON = Li3.3PO3.8N0.2) thin films battery under charging condition, prepared on self-supporting Al substrate, have been in situ measured by means of transmission elastic recoil detection (TERD) and Rutherford backscattering spectroscopy (RBS) techniques not only with 5.4 MeV He2+ ion beam without absorber, but also 9 MeV O4+ ion beam with Al absorber. In experiments with 5.4 MeV He2+, well-resolved step-wise TERD spectra have been observed, from which thickness and Li composition of constituent films of the battery are directly estimated. The Li transport from LCO to Si films through LiPON as well as return-back of Li from Si to LCO films and Li leakage into the Al substrate out of the battery system by over-charging under charging condition have been observed in the experiments both 5.4 MeV He2+ and 9 MeV O4+. The latter result indicates that these techniques are applicable to testing degradation of the battery performance by repetition of charging and discharging. Both results are compared in details with each other.

The effect of surface oxidation on hydrogen absorption in Ti-6Al-4V alloy studied by elastic recoil detection (ERD), X-ray diffraction and nanohardness techniques

The effect of naturally occurring oxide and oxidised layers formed by ion implantation and thermal oxidation on hydrogen absorption was investigated in Ti-6Al-4V alloy samples as a possible candidate for hydrogen storage. The samples were implanted with two different oxygen fluences (1.5 × 1017 and 3.0 × 1017 ions/cm2) at room temperature and 550 °C, and comparison was made with thermally oxidised samples at a temperature of 550 °C for 2 h. All samples were afterwards hydrogenated at 550 °C for 2 h. The elastic recoil detection analysis show that approx.14 at.% H was absorbed in as-received and thermally oxidised samples. The native oxide layer and the oxidised layer formed by thermal oxidation enhanced the absorption of hydrogen regardless of their different thickness and stoichiometry. The amount of hydrogen, however, was significantly lower in implanted samples, approx. 3–5 at.%, suggesting that oxygen ions implanted in alloy prevent hydrogen absorption. It was found that the average amount of absorbed hydrogen within the projected depth was reduced due to implantation of oxygen ions regardless of their fluences and implantation temperature. The hydrides were not determined in any of investigated samples while the surface hardness of all samples increases after hydrogenation although to different extent.

Electron gun with a transmission photocathode for the Joint Institute for Nuclear Research photoinjector

Photocathode electron guns are key to the generation of high-quality electron bunches, which are currently the primary source of electrons for linear electron accelerators. The photogun test bench built at the Joint Institute for Nuclear Research (JINR) is currently being used to further develop the hollow (backside irradiated) photocathode concept. A major achievement was the replacement of the hollow photocathode by a technologically more feasible transmission photocathode made from a metal mesh that serves as a substrate for films of various photomaterials. A number of thin-film cathodes on quartz glass substrates are fabricated by photolithography. The vectorial photoeffect (related to the surface-normal component of the wave electric field) is observed and found to significantly affect the quantum efficiency. The dependence of the quantum efficiency of diamond-like carbon photocathodes on the manufacturing technology is investigated. The Rutherford backscattering and elastic recoil detection techniques are combined to carry out an elemental analysis of the films. An estimate of the emittance of a 400 pC electron beam is obtained using the cross-section method.

Dynamic Measurements of Hydrogen and Lithium Distributions in Lithium-Cobalt-Oxide Films with Charging and Heating Using Elastic Recoil Detection Techniques

The migrations of lithium (Li) as well as hydrogen (H) in multi-layers thin films of Au/LiCoO2 (thickness: approximately 42nm/80nm), deposited onto one face of Li1.4Ti2Si0.4P2.6O12–AlPO4 (LATP) substrates, were dynamically observed with electric charging as well as isochronal annealing in vacuum by combining elastic recoil detection (ERD) analysis with Rutherford backscattering spectrometry (RBS)with 9.0-MeV O4+ ion-probe beams. The ERD spectra clearly revealed that Li atoms of approximately 9.4 at% migrated from the LiCoO2 surface to the LiCoO2/LATP interface with H absorption by a charge of approximately 0.48 e/cm2, which the acquiredvoltage was1.65V. In addition, the diffusion of Li atoms to the LATP bulk occurred with H release by isochronal annealing at only 323K for 10min.The presence of H significantly influences the Li+ ion conduction for the Li-battery systems.

On the analysis of H in thin layers of Pt electroless contacts using elastic recoil detection technique

Cadmium telluride CdTe is a II–VI binary semiconductor, which has multiple applications, especially in nuclear, X-ray and gamma ray detection. In such applications, the material can be made more resistive by compensation with halogen elements like Cl. However, this compensation has a side-effect on the detectors, the “polarization effect”, which decreases the detector efficiency. One way to reduce this effect is the use of quasi-ohmic contacts deposited by a spontaneous electro-chemical deposition method, so-called “electroless deposition”, of metals such as Pt. Indeed, the use of this electroless deposition method will induce a great amount of hydrogen in the solution and, consequently, part of it will be present in the new formed layers. Since hydrogen content will affect the electrical and optical properties of semiconductors, the aim of this paper is to investigate the concentration profile of H in the contact layers, using Elastic Recoil Detection Analysis technique ERDA, where samples are analyzed as a function of the dilution and pH value of the deposition solution. The preliminary results show that a H atomic concentration as high as 2×1020atoms/cm3 is found in the interfacial layer. Correlations with detection properties and a new polarization healing model are proposed.

Dynamic measurements of Li depth profiles in a Li‐ion battery system under charging condition by means of ERD and RBS techniques

Depth profiles of Li in a Li‐ion battery system of Au/LiCoO2/LATP/Pt (LATP:Li1+X+YAlYTi2−YGeXP3−XO12) have been in situ measured at several stages of charging by means of the elastic recoil detection (ERD) and Rutherford backscattering (RBS) techniques with 9 MeV O4+ ion beam. The thicknesses of LiCoO2 and Au are estimated from the RBS spectrum for the as‐received specimen to be 190 and 27 nm, respectively. From the ERD spectrum, it is also found that there exists impurity hydrogen of ~5% in LiCoO2. Moreover, it is found from the ERD data analysis after the first charging of 0.48 × 1016 e/cm2 to Au electrode that the fractional concentration of Li in LiCoO2 at the interface with Au electrode steeply decreases to 0.8, recovers with depth toward the interface with LATP and attains at 1.3 above the original value. With increasing the amount of charge supplied, the slope in the Li composition from Au electrode to LATP increases gradually. The data on the charging is concluded to include the irradiation effects due to the incident O ions, since the data on a non‐irradiated part of the specimen obtained after finish of the charging shows that Li is almost completely reduced from LiCoO2. The dynamics of Li composition in LiCoO2 as a function of charging supplied is discussed in connection with hydrogen impurity and irradiation effect of the incident O ions. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Thermal Behavior of Hydrogen Retained in Amorphous-titanium-hydride Thin Films

Changes in hydrogen distribution near the surface of non-stoichiometric titanium hydride (TiHx; x=0.49) thin films possessing an amorphous structure and approximately 170 and 400 nm thick, prepared by a magnetron ion-sputtering device, were investigated by combining an elastic recoil detection (ERD) technique with Rutherford backscattering spectrometry (RBS) one after isochronal annealing at different temperatures (300-500 K) for 10 min. The concentration of hydrogen atoms retained in TiHx thin films completely vanished at much lower temperatures of 350-400 K, as compared with the decomposition temperature (approximately 473 K) of δ-phase titanium hydride (δ-TiH1.92). In addition, the thickness of TiHx thin films also reduced with an increase in temperature. The rapid decrease of the hydrogen concentration in TiHx thin films below 400 K is caused by thermal desorption of hydrogen atoms, detrapped from the amorphous structure and associated, in addition, with Ti evaporation.

Hydrogen absorption and emission characteristics of Pt/Li4SiO4/Pt hydrogen storage materials exposed to air at room temperature

Hydrogen storage and emission characteristics of Pt/Li4SiO4/Pt composite materials exposed to normal air at room temperature have been studied by means of elastic recoil detection analysis, RBS, and weight gain measurement techniques. The thermal annealing curves of Pt/Li4SiO4/Pt sandwich specimens with Pt layers of 1 and 10 nm in thickness measured by elastic recoil detection technique indicate that the hydrogen emission of residual hydrogen takes place in the two stages, and 70% of hydrogen retained is emitted at the first stage, which finishes at a temperature of ~350 K. The hydrogen storage curves at the first run indicate that the saturation storage levels of the specimens of 1 and 10‐nm Pt layers pre‐heated at 423 K are 12 wt.% and 14 wt.%, respectively. The hydrogen storage curve of the specimen with 10 nm Pt layers annealed at temperature of 773 K indicates that the initial slope of the weight gain is considerably larger than that at the first run. This fact seems to indicate that the high temperature annealing brings about enhancement in the absorption rate caused by formation of Pt‐Si‐Li‐O complex oxides through the interfacial reaction between the Pt layer and Li4SiO4. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Elastic recoil detection studies of near-surface hydrogen in cavity-grade niobium

Recent studies of the quality factor degradation mechanisms in superconducting RFniobium cavities at high surface magnetic fields revealed that RF performance may dependon the total hydrogen content in the 40 nm thick near-surface layer. Hydrogen distributionin niobium and its near-surface content variations after different chemical surfacetreatments has been addressed in previous studies. However, only chemical treatments werestudied while heat treatments are equally important. In this work we use the elastic recoildetection (ERD) technique to systematically study the distribution of hydrogen in niobiumsheet and cavity cutout samples subjected to chemical and heat treatments typicallyperformed on niobium cavities. Our results indicate the near-surface segregation ofhydrogen at the niobium oxide/niobium interface, and do not show any significantvariation in hydrogen content after various heat and chemical treatments. We do notobserve a direct correlation between total hydrogen content and the high fieldQ slope. Consequences of the observed hydrogen segregation are discussed in the framework of theNbHx phase diagram.

Interaction of water vapor with gamma-radiation-induced defects in proton conductive polymers

The correlation between protonic conduction and the amount of radiation-induced defects in gamma-ray-irradiated perfluorosulfonic acid (PFSA) polymers (Aciplex-SF-1004 ®) has been investigated using a direct-current resistance method, transmission spectroscopy for the ultraviolet (UV) and visible (Vis) wavelength ranges and Fourier transform infrared (FTIR) spectroscopy with the attenuated total refraction (ATR) technique. The proton conductivity of the polymers, which are irradiated with a dose of up to 532 kGy under vacuum at room temperature and subsequently exposure to air, is enhanced by approximately three orders of magnitude as compared to that of the unirradiated polymer. The UV–Vis spectra of the irradiated polymers reveal the presence of fluorocarbon radicals, which increase with the irradiation dose. It is also observed in the UV–Vis and FTIR spectra that peroxy free radicals, unsaturated species (COF), and a carboxyl group (COOH) containing a carbon-oxygen double bond are formed by reactions of the fluorocarbon radicals with oxygen or water vapor in air. In addition, an increase in the hydrogen concentration is observed in the near-surface regions of the irradiated polymers by using an elastic recoil detection (ERD) technique. The production of charge carriers such as protons and oxonium ions (H 3O +) by the interaction of water vapor with the activating-radiation-induced defects leads to the enhancement of the proton conductivity.

Change in hydrogen absorption characteristic of SrCe 0.95Yb 0.05O 3 − δ by electron beam modification

Changes in the hydrogen absorption property of orthorhombic perovskite-type oxide ceramics (SrCe 0.95Yb 0.05O 3 − δ ), irradiated up to dose of 7.6 and 15 MGy with1.8 MeV electron beams, have been investigated using optical absorption in the visible and infrared wavelengths, X-ray photoelectron spectroscopy (XPS) and elastic recoil detection (ERD) technique. For the electron irradiation dose up to 7.6 MGy, the production of oxygen vacancies, conversion of Ce 4+ to Ce 3+ ions and segregation of SrO to the surface occurred. However, the hydrogen absorption property hardly changes by the radiation induced phenomena. For further irradiation up to 15 MGy, Sr and Ce hydroxides were formed on the topmost surface. In addition, the hydrogen content in near surface significantly depended on the humid atmosphere. The results are due to dissociation of water with the surface activated by radiation damage and show the improvement of the hydrogen absorption characteristic.

Thermally induced interfacial interactions between various metal substrates and a-SiC thin films deposited by a polymer-source chemical vapor deposition

Amorphous silicon carbide (a-SiC) thin films have been deposited onto a variety of substrates, including silicon, SiO 2, Si 3N 4, Cr, Ti and refractory metal-coated silicon, by means of a polymer-source chemical vapor deposition (PS-CVD), at a substrate temperature of 800 °C. The poly(dimethylsilane) (PDMS) was used as a high-density single-source molecular precursor for the PS-CVD process. Capacitance–voltage ( C– V) measurements were systematically used to evaluate the impurity level of the deposited a-SiC films. In addition, elastic recoil detection (ERD) and X-ray photoelectron spectroscopy (XPS) techniques were used to determine the elemental composition of the films and their interface with substrates. Scanning electron and atomic force microscopies were also employed to characterize the surface morphology of the films. The impurity levels of the a-SiC films were found to be clearly correlated with the nature of the underlying substrates. The Pt–Rh and TiN-coated Si substrates are shown to lead to the lowest impurity level (∼1 × 10 13 cm −3) in the PS-CVD grown a-SiC films, while Cr and Ti-coated Si substrates induce much higher impurity concentrations. Such high impurity levels are shown to be a consequence of a strong metallic diffusion of the metallic species (Cr or Ti). In contrast, no diffusion was observed at the interface of a-SiC with either Pt–Rh or TiN. Our results pinpoint TiN-coated Si as the electrode material of choice that satisfies best all the criteria required for the integration of a-SiC into opto-electronic devices.

Hydrogen Accumulation in Surface of Perfluorosulfonic Acid Membranes after γ-Ray Irradiation using Elastic Recoil Detection Techniques

Electrical conductivity measurements and elastic recoil detection (ERD) analysis were carried our on perfluorosulfonic acid membranes that were irradiated by 60Co γ-ray. Maximum electrical conductivity of irradiated specimen was obtained at 40–60 °C, though that of unirradiated specimen increased with increasing temperature. And 4000-fold higher conductivity was obtained in irradiated membrane at 40 °C under dry condition. ERD analysis indicated that hydrogen concentration of the irradiated membrane is 1.5-fold higher than that of the unirradiated specimen. It is considered that the γ-ray generates a lot of site that can trap hydrogen and the trapped hydrogen cannot easily move. As the results, irradiated membrane retains more hydrogen than unirradiated one and the electrical conductivity of irradiated membrane is higher than that of unirradiated membrane in any conditions. γ-Ray irradiation is effective for improving the electrical conductivity of proton-conducting membranes.

Measurement of the transport of hydrogen isotopes near the surface of metal-hydride and deuteride using elastic recoil detection technique

The thermal behavior of hydrogen isotopes near the surface of δ-phase titanium hydride and deuteride covered with an oxide layer has been investigated using the elastic recoil detection (ERD) technique. The hydrogen isotopes concentrations near to the surface of the hydride and deuteride decreased exponentially as a function of annealing time in the temperature range of 423–488K. Also a hydrogen concentration gradient is formed at the surface. The change of the hydrogen distribution with annealing time at several temperatures was analyzed using mass balance equations in which elementary processes such as diffusion, trapping and detrapping at vacant trap sites are taken into account. The effective diffusion rates of hydrogen isotopes to the topmost oxide layer and thermal detrapping rates of hydrogen isotopes at the hydride–oxide interface were estimated. Moreover, the activation energies for the effective diffusion rate and the thermal detrapping rate were determined to be 0.54±0.10 and 1.20±0.02eV, respectively.

Formation of bubbles and extended defects in He implanted (1 0 0) Si at elevated temperatures

The formation and thermal evolution of He bubbles and extended defects in Si are studied as a function of the implantation ( T i) and annealing ( T a) temperatures. (1 0 0) Si wafers were implanted with 40 keV He + ions to a fluence of 1 × 10 16 cm −2 at temperatures T i from 300 to 623 K. After the implantations the samples were submitted to thermal treatments for 600 s at temperatures T a from 673 to 1073 K. The samples were analyzed using transmission electron microscopy (TEM), Rutherford backscattering/channeling (RBS/C) and elastic recoil detection (ERD) techniques. The results obtained show that the microstructure characteristics of the bubble and the extended defect systems, as well as their thermal evolution behavior, depend significantly on the implantation temperature. A correlation between the dynamic annealing behavior and the bubble and defect formation process is proposed.