Rutherford Backscattering Spectrometry Techniques Research Articles

Low temperature sputtering deposition of Al1−xScxN thin films: Physical, chemical, and piezoelectric properties evolution by tuning the nitrogen flux in (Ar + N2) reactive atmosphere

This work investigates the physical properties of Al1−xScxN thin films sputtered at low temperatures by varying the process conditions. Specifically, the films were deposited at room temperature by applying a radio frequency power equal to 150 W to an AlSc alloy (60:40) target, varying the nitrogen flux percentage in the (Ar + N2) sputtering atmosphere (30%, 40%, 50%, and 60%) and keeping constant the working pressure at 5 × 10−3 mbar. The structural and chemical properties of the Al1−xScxN films were studied by x-ray diffraction and Rutherford backscattering spectrometry techniques, respectively. The piezoelectric response was investigated by piezoresponse force microscopy. In addition, the surface potential was evaluated for the first time for Sc-doped AlN thin films by Kelvin probe force microscopy, providing piezoelectric coefficients free from the no-piezoelectric additional effect to the mechanical deformation, i.e., the electrostatic force. By alloying AlN with scandium, the piezoelectric response was strongly enhanced (up to 200% compared to undoped AlN), despite the low deposition temperature and the absence of any other additional energy source supplied to the adatoms during thin film growth, which generally promotes a better structural arrangement of polycrystalline film. This is a strategic result in the field of microelectromechanical systems completely fabricated at low temperatures.

Fabrication and characterization of thin 94Zr target with gold backing for nuclear lifetime measurements using DSAM

For lifetime measurements of excited nuclear states in the sub-picosecond range, a thin target with a thick backing of high-Z material is required. To meet these specifications, a thin isotopic94Zr target of thickness 1.14 ± 0.05 mg/cm2, with backing of 4.7 ± 0.2 mg/cm2 thick Au layer, has been fabricated using the cost-effective cold rolling technique at the target laboratory of Inter-University Accelerator Centre (IUAC), New Delhi. The thickness verification and purity check of the fabricated target have been carried out by non-destructive Energy Dispersive X-ray Fluorescence (EDXRF) and Rutherford Backscattering Spectrometry (RBS) techniques. The results of these measurements are in good agreement with each other. The elemental composition, purity and surface morphology have been explored by Energy Dispersive X-ray Spectrometry (EDS) and Scanning Electron Microscopy (SEM) techniques. The fabricated target has been successfully used with a16O ion beam in a recent γ-ray spectroscopy experiment for lifetime measurements using the Doppler Shift Attenuation Method (DSAM) at IUAC, New Delhi.

Reaction-Diffusion-Driven Stoichiometric Gradient in Coevaporated Superconducting NiBi3 Thin Films

The intermetallic compound NiBi3 belongs to the interesting class of superconductors that are based on strong ferromagnetic elements. Although NiBi3 has been grown in single-crystal form and has also been demonstrated to form at the interface of Ni and Bi layers, uniform NiBi3 thin films have yet to appear in the literature. In this work, we have explored the codeposition method, wherein high-purity Ni and Bi metals are evaporated simultaneously at controlled rates, to study the dynamics involved in the formation of NiBi3 films. We have used the Rutherford backscattering spectrometry (RBS) technique to make a quantitative stoichiometric comparison of codeposited films grown at two different evaporation rates of Bi, while keeping the evaporation rate of Ni fixed. We find that, due to the highly diffusive nature of the Bi atoms in this system, the growth dynamics favors the formation of almost stoichiometric NiBi3 only at the top surface (few tens of nanometers) of the films, whereas there is a nonlinear stoichiometric variation toward the substrate. The average local bonding environment around Ni, studied by synchrotron-based X-ray absorption spectroscopy, agreed with the overall findings of RBS. Since the physical properties of NiBi3 are sensitive to the ratio of Ni and Bi, we find the superconducting transition and magnetic coercivity to be consistent with the above observations.

Characterization of a Nb-Pb composite target

A thin Nb target on a Pb backing was fabricated using the rolling technique. In the present work, the characterization of the sample has been carried out using various techniques to study the surface morphology, crystallography, elemental analysis, thickness and electrical conductivity useful for the intended use of the target prepared. The thin Nb target was analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Rutherford back-scattering spectroscopy (RBS) techniques. The uniform and smooth surface of the sample was confirmed by SEM imaging. The presence of oxygen in the EDS spectra and peaks corresponding to crystal planes of PbO2 in the XRD spectrum confirms the oxidation of Pb foil. The XRD spectrum shows clear peaks corresponding to (011), (002), (112) crystal planes of pure Nb. The thickness of the thin Nb foil measured using the RBS techniques was found to be 0.8 mg/cm2. The current(I)-voltage(V) curve (relationship between the current flowing through an electronic device and the applied voltage across its terminals) at room temperature for the Pb and Nb/Pb foils was plotted and showed linear relationship between applied voltage and current flowing through the target foil. The measured electrical conductivity indicates an enhancement of 35.9 % for Nb/Pb foil relative to the conductivity measured for the Pb foil.

Tungsten oxide thin film for room temperature nitrogen dioxide gas sensing

Tungsten oxide (WO3) thin films for gas sensing have been successfully deposited using reactive direct current (DC) magnetron sputtering at different deposition temperatures (300 °C, 400 °C and 500 °C). The structural, morphological properties, thickness and composition have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering spectrometry (RBS) techniques. To investigate the effect of deposition temperature on the gas sensing properties of deposited thin films on alumina substrates, was conducted using the Kenosistec gas sensing unit. WO3 thin film deposited at 500 °C exhibited a higher response when sensing Nitrogen dioxide (NO2) at room temperature as compared to the thin films prepared at 300 °C and 400 °C, respectively. However, as deposited WO3 thin films exhibited low sensitivity when sensing reducing gases such as hydrogen (H2) and ammonia (NH3), which was an indication of good selectivity properties of WO3 related sensors.

Characterization of agricultural biomass by particle induced x-ray emission and Rutherford backscattering techniques

Particle-induced x-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) techniques are non-destructive elemental analyses method with high sensitivity and capability for multi-element analysis in one spectrum. These techniques have not been used for the elemental characterization of biomass. So, this study characterized and evaluated elemental compositions of some selected agricultural biomass (Palm kernel shell (PKS), coconut shell (CS), cassava peel (CP), and Africa star apple seed shell (ASASS)) using combined PIXE and RBS. The results were compared with the ultimate analysis and optical-based techniques. Results from PIXE and RBS analysis confirm the presence of C, O, S, Na, Mg, P, Si, K, Ca, Fe, Cl, Al, Ti, Cu, and Zn in the tested biomass samples. Estimation of RBS accuracy by direct comparison with the ultimate analysis of some biomass samples showed a wide disparity of ±10.7% and ±2.57% in the RBS data for carbon and oxygen in PKS and a disparity of ±5.22% and ±0.55% in the RBS data for carbon and oxygen in coconut shell respectively. In the case of minor and trace element concentrations, estimated errors in the range of 1–3% and 2.68–4% were observed for optically based techniques compared with PIXE and RBS analysis, respectively.

New setup for basic radiobiology studies using a 3 MV TandetronTM: Design and developments

The aim of the study was to upgrade the Horia Hulubei National Institute for Physics and Nuclear Engineering existing facility - a 3 MV TandetronTM accelerator - to be used in radiobiology experiments. Irradiations were performed with 1.95 MeV protons (beam with uniform distribution over a 30 mm2). Particle fluence was determined with plastic track detectors and live monitored using Rutherford Backscattering Spectrometry technique. Absolute and relative dose (Advanced Markus ion chamber) and the lateral quality of the irradiation spot (radiochromic film) were measured. The dosimetric measurements were confirmed by Geant4 simulations of the dose averaged Linear Energy Transfer, the Bragg peak profile and the beam lateral energy distribution. A complete setup for exposing in vitro cell cultures to the particle beams was constructed from scratch. Preliminary data of survival rate of V79 fibroblast cells are reported. The obtained results are similarly with data reported using other proton beam facilities.

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.

Experimental study and thermal spike modeling of sputtering in SiO2 thin films under MeV Auq+ heavy ion irradiation

The sputtering of silicon dioxide (SiO2/Si) thin films deposited onto silicon substrates and irradiated by swift Auq+ heavy ions (q = +4 to +9) has been investigated both by experiment and via numerical modeling by varying the kinetic energy from 10 to 40 MeV. The induced sputtering yields were determined experimentally via the Rutherford backscattering spectrometry (RBS) technique using a 2‐MeV He+ ion beam. The obtained experimental results were first plotted versus the target electronic stopping power together with previous data available for the same projectile‐target system at high kinetic energies, indicating increased sputtering yields with increasing electronic energy loss. Then, the whole data were compared with numerical sputtering yield values derived both from the inelastic thermal spike model and the SRIM‐2013 simulation code by including, respectively, nonlinear elastic spikes and linear elastic collision cascades. A good agreement was observed between the measured sputtering yield data and i‐TS predicted values over higher incident energies used by using refined parameters of the ion slowing down with reduced thermophysical properties of the SiO2 thin film. Finally, the synergy between electronic and nuclear energy loss processes inducing sputtering at low incident energies was discussed through the comparison between experimental and numerical yield data.

Applications of Rutherford backscattering analysis methods to nuclear physics experiments

Target properties such as thickness and composition are essential ingredients in nuclear physics experiments, therefore, dedicated analyses to evaluate them before and/or after the measurement are often performed. In some experimental techniques, the exploited detectors allow for the evaluation of these properties on-line, i.e. directly during the experiment. In this paper, we report on the use of analysis methods coming from the Rutherford backscattering spectroscopy technique to obtain on-line information on the target used in a nuclear physics experiment. This measurement was performed at INFN LNL by exploiting the low-energy Coulomb excitation technique. The results have been compared with an independent Rutherford backscattering spectroscopy analysis of the same target performed at INFN LABEC in Florence.

Growth and Characterization of ZnO and Al-Doped ZnO Thin Films by a Homemade Spray Pyrolysis

In this work, we have prepared the undoped and Al-doped ZnO thin films by a homemade spray pyrolysis method at 450°C onto glass substrates. The X-ray diffraction patterns of undoped ZnO and aluminized zinc-oxide (AZO) thin films exhibit hexagonal wurtzite crystal structure with high crystalline quality, the crystallite size is nanometric. The morphology of the undoped and Al-doped ZnO thin films also indicate that all samples have a nanoscale grain size around 50 nm, and the microstructure of ZnO films is highly influenced by the aluminum doping. The two films are characterized by UV-visible spectrophotometry showing that the films have a whole optical transmission above 85% in the visible range. The composition of our films is obtained by energy dispersive spectrum, confirmed by Auger electron spectroscopy (AES) and by Rutherford back-scattering spectrometry (RBS) techniques.

Atomic composition, structure, and electrical properties of In1-xGaxSb films deposited by magnetron sputtering

This article reports the formation of polycrystalline In1-xGaxSb films (x = 0, 0.2, 0.4, 0.5, and 1) deposited by magnetron sputtering on SiO2/Si substrates and a comprehensive characterization of their atomic composition, structure, and electrical properties. The structural and electrical characteristics of the films can be easily tuned by varying the stoichiometry of the compounds. The atomic composition of the films was investigated with particle induced x-ray emission and Rutherford backscattering spectrometry (RBS) techniques (the latter as a function of depth), while grazing incidence x-ray diffraction analysis yielded valuable information about the structure of the films. In1-xGaxSb films were polycrystalline, with crystallite sizes in the range 18–42 nm. Combining RBS and scanning electron microscopy results, it was possible to infer the overall density and also the density of the crystalline portion of the films, which turned out to be significantly distinct. A non-negligible fraction of oxygen atoms has been detected in all films, most prominently in the ternary ones, contributing to the formation of high density amorphous In2O3 and Ga2O3 in films with 40% and 50% Ga, while amorphous antimony oxide phases are predominant in the binaries as well as the ternary compound with 20% Ga. The electrical characterization of the films was performed using four point and Hall effect methods and the results show a consistent increase in resistivity with Ga concentration.

High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy

The recently discovered phenomenon of Néel spin–orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependent resistance measurements. The thin film composition was determined using both inductively coupled plasma optical emission spectroscopy and Rutherford backscattering spectrometry techniques. The MBE-grown films were found to show a superior smooth morphology and a low defect concentration, resulting in reduced scattering of the charge carriers.

Defect evolution in Ni and solid-solution alloys of NiFe and NiFeCoCr under ion irradiation at 16 and 300 K

Single-phase concentrated solid-solution alloys (SP-CSAs) have shown unique chemical complexity at the levels of electrons and atoms, and their defect evolution is expected to be different from conventional dilute alloys. Single crystals of Ni, NiFe and NiFeCoCr are chosen as model systems to understand the chemical complexity on defect formation and damage accumulation in SP-CSAs under ion irradiation. The high-quality crystals were irradiated at 16 and 300 K to different ion fluences, to form irradiated region with little to heavy damages. The ion-induced damage was determined using Rutherford backscattering spectrometry technique along a channeling direction (RBS/C) and the level of lattice damage in irradiated Ni and SP-CSAs was quantified from Monte Carlo (MC) simulations. The results are interpreted using the Multi Step Damage Accumulation model to reveal material damage accumulation kinetics. Key findings of the study are that in case of room temperature irradiations the damage level measured for complex alloys at the highest irradiation fluence of 2 × 1015 cm−2 (∼3 dpa) is significantly higher than that obtained for pure nickel samples and suggest two-step damage accumulation process with a defect transformation taking place at a fluence of about 1.5 × 1015 cm−2. Moreover, structural and damage kinetic differences clearly imply that, with increasing degree of chemical complexity and high solid-solution strengthening effects from Ni to NiFe and to NiFeCoCr, the enhanced lattice stiffness resists to randomization of atomic configurations and inhibits the growth of extended defects.

Ion Beam Analysis for recession determination and composition estimate of Aerospace Thermal Protection System materials

The study of Thermal Protection Systems (TPS) is largely performed in Plasma Wind Tunnel (PWT) facilities where sample wear rate is of main interest and the knowledge of its relation with sample surface temperature desirable. The intrusive and indirect methods employed so far reduce the reliability and the accuracy of these tests.A new joined technique based on both the Surface Layer Implantation of radioactive tracers and on the emissivity-free Dual Color Infra-Red thermography allows the online measure of both the TPS wear rate and the surface temperature without any preparation (i.e. modification) of the sample. Other Ion Beam Analysis techniques like the Rutherford Backscattering Spectrometry (RBS) can be employed off-line to perform integrative, quantitative and still not intrusive analysis of TPS composition and of the structure modifications occurred during the PWT tests.In this work we present the results of a discrete wear rate measurement of an ablative TPS implanted with 7Be ions and the feasibility study of the RBS technique to investigate the oxidation of ceramic TPS.

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.

Li depth profiles of metal/Li-electrolyte/metal capacitors under biasing studied by means of MeV ion beam analysis techniques

Li Depth profiles at the interfaces of capacitors of Cu/LiPON/Cu and Al/LiPON/Al prepared on buffer Ti layer /SiO2glass and Au/LATP/Au (LiPON = Li3.3PO3.8N0.2, LATP = Li3.1Al0.84Ti1.16Ge1.27P1.73O12) under biasing bottom metal against top metal at earth potential have been in-situ measured by means of elastic recoil detection analysis (ERD) and Rutherford backscattering spectrometry (RBS) techniques. Li has been found to be enriched near the interface with electrode biased negatively, while it is depleted near that biased positively. The Li depth profile in electrolyte has been theoretically calculated, taking into account the transport faction of Li ions, based on hopping diffusion model of Li ions under potential gradient. It is shown that the Li depth profile calculated as a solution of diffusion equation at steady state agrees qualitatively well with the experimental ones and the transport fraction of Li ions in electrolyte is less than unity.

A comparative study of epitaxial InGaAsBi/InP structures using Rutherford backscattering spectrometry, X-ray diffraction and photoluminescence techniques

In this work, we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3%–4% range. XRD data showed that the InGaAsBi layers are more homogeneous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low-temperature PL exhibited multiple emission peaks; the peak energies, widths, and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at a random orientation together with channeled measurements allowed both an estimation of the bismuth composition and analysis of the structural properties. The RBS channeling showed evidence of higher strain due to possible antisite defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channeling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.

Study of C, Al, Si and Ge sputtering yield amplification by ion beam analysis and co-sputtering simulation software

In 1991 Berg discovered the phenomenon he called sputtering yield amplification (SYA). He considered that the explanation of the phenomenon was related to the difference in the masses of the atoms involved, i.e. the target atoms, the incident ion, usually Ar, and the added atoms, which were heavier than the target atoms. Today, with additional experimental results, it is thought that the surface binding energy is also involved. In this study, thin films of C, Si, and Ge were deposited using targets with small pieces of W added to the different targets, and Al films were deposited with small pieces of Ti added to the target. The spatial distribution of both the total deposit and that of each element was measured, and the same distributions were simulated using the co-sputtering simulation (Co-SS) software. The simulation parameters of the Co-SS software are the angular distribution of the atoms sputtered from the target and the sputtering yields. The analysis showed that the addition of one, two and three pieces of W to the C and Si targets resulted in a SYA of 66%, 35% and 43%, and 15%, 42% and 74%, respectively. However, there was no change in the sputtering yield of Ge with the addition of W. The SYA for the Al target with the pieces of Ti was 9%, 23% and 15%. The angular distribution of the atoms sputtered from the targets was also affected by the presence of W or Ti inserts as well as the W atomic concentration. The elementary spatial distribution, the thin film thickness and the W atomic percentage were measured by Rutherford backscattering spectrometry, profilometry and x-ray photoelectron spectroscopy techniques, respectively.

High energy (150 MeV) Fe11+ ion beam induced modifications of physico-chemical and photoluminescence properties of high-k dielectric nanocrystalline zirconium oxide thin films

Abstract This work presents the influence of dominated electronic energy loss over nuclear energy loss induced by swift heavy ion (SHI) irradiation on the physico-chemical, optical and other properties of RF grown zirconium oxide (ZrO2) thin films. For this purpose, thin films of ZrO2 grown on glass substrate were irradiated by 150 MeV Fe11+ ions with a range of fluence from 2E12 to 5E13 ions/cm2 to understand the mechanism of induced modifications and defects generation. The XRD results confirmed that the virgin and irradiated ZrO2 thin films were crystalline in nature with monoclinic and tetragonal structure. The crystallite size varied from 19.93 nm to 46.43 nm with varying ion fluence. Strain, dislocation density and stacking fault were used to investigate the changes in structural parameters. Tauc's plot method was employed for the quantitative evaluation of optical energy band gap (Eg) that exist in the range of 4.45–4.62 eV. The transmittance (%) of the virgin and Fe11+ ions irradiated samples was determined in the range of 35.69–66.09% using UV–Vis. spectroscopy. Further, the refractive index was determined using different methods significantly depends on the optical band gap. The broad PL emission peaks were obtained at 375 nm and 440 nm with the excitation wavelength (λex.) of 300 nm. The variation in PL intensity with increasing ion fluence was attributed to the creation or annihilation of primary or complex defects. FTIR spectroscopy was employed for the analysis of chemical modifications in vibrational bonds of samples and the band obtained 660 cm−1was assigned to the asymmetrically coupled Zr–O–Zr stretching which presents the strong vibration in samples. The band intensity increased up to the fluence 5E12 ions/cm2 and decreased at a higher fluence of 1E13 ions/cm2. Rutherford backscattering spectroscopy technique was used to determine the thickness (165 nm) of the samples.