Rutherford Backscattering Method Research Articles

APPLICATION OF RUTHERFORD BACKSCATTERING METHOD FOR STUDYING RADIATION-INDUCED SEGREGATION OF HIGH-ENTROPY NICKEL-BASED ALLOYS

In this study, radiation-induced segregation was studied in high-entropy alloys (HEA) CoCrFeNi, CoCrFeMnNi, irradiated with helium ions He2+ with an energy of 40 keV at room temperature. Changes in the concentrations of HEAs and their depth distributions were studied by Rutherford Backscattering (RBS) and energy dispersive x-ray spectroscopy (EDS) methods. Measurements using the RBS and EDS methods showed that non-irradiated HEAs have a composition close to equiatomic, where the average concentration for CoCrFeNi is 24.8 atomic percents (at.%), and for CoCrFeMnNi – 20 at.%. The EDS results were significantly different from the RBS in Ni/Co concentrations, and indicated no significant changes in element distribution in both HEAs after irradiation. According to the RBS data, the largest changes in concentrations during irradiation in both HEAs relate to the enrichment of Ni atoms. In CoCrFeNi, upon irradiation, Ni/Co atoms undergo the greatest segregation, and in CoCrFeMnNi, the Ni/Co/Fe concentrations change significantly. In CoCrFeMnNi, the change in element concentrations with increasing irradiation fluence was more pronounced than in CoCrFeNi. In CoCrFeMnNi, changes in concentrations of all elements at both fluences reached 0.5–17% (0.1–3.1 at.%) and exceeded changes in CoCrFeNi, which reached 2–11% (0.5–1.9 at.%). It was found that the resistance to segregation when irradiated with helium ions under these conditions was lower for CoCrFeMnNi than for CoCrFeNi. In CoCrFeNi and CoCrFeMnNi, changes in the concentrations of Co, Fe, Cr, and Mn were significantly less than changes near sinks and defect clusters when irradiated with nickel ions with similar doses in other studies at temperatures close to the halfmelting temperature of nickel HEAs. The RBS study showed a uniform distribution of atoms in depth and resistance to segregation in CoCrFeNi, CoCrFeMnNi when irradiated with helium ions.

An examination on the porosity of Er[formula omitted] doped Ca[formula omitted] crystal using the Rutherford back-scattering method

This work investigates the porosity of ErF3 doped CaF2 crystals using the Rutherford back-scattering (RBS) method. Two ErF3:CaF2 samples of 2.0 and 5.5% doping ratios were prepared using the Bridgman method. The RBS spectra of these samples at two incident angle configurations of the projectile alpha, i.e., 0 and 30 degree, were collected using the Rutherford back-scattering spectrometer at the Joint Institute for Nuclear Research in Dubna, Russia. The measured spectra were analyzed with sample models of porous materials using the SIMNRA program. It turns out that the porous volume ratio and diameter are probably in the intervals of 18 to 22% and 2.4×1018 to 3.0×1018 atoms per cm2, respectively. However, the RBS method exhibits significant uncertainty, impeding our ability to establish a correlation between porosity characteristics and doping ratios.

Formation of SiC by Vacuum Carbidization on Porous Silicon

Planar-view TEM investigation revealed the formation of cubic silicon carbide layers on porous silicon by vacuum carbidization. The formation of cubic silicon layers in the form of a two-phase system was found. At the same time, the formed SiC layers on the mesoporous buffer layer are predominantly polycrystalline. Using the Rutherford backscattering method, it was found that the use of buffer layers of porous silicon makes it possible to obtain SiC layers of greater thickness than on a pure silicon substrate under similar conditions of vacuum carbidization. It is shown that an increase in the pore size in porous silicon layers leads to an increase in the thickness of the formed SiC layers. It has been shown by scanning electron microscopy that vacuum carbideization of porous silicon leads to formation of SiC grains in pores, partial overgrowth and sintering of pores. The dependence of the SiC grain size on the pore size was established.

Structure and corrosion behaviour of CrxAl(Si)yC coatings fabricated by the vacuum arc discharge technique

The composition, structure and corrosion behaviour of CrxAly(Si)C coatings fabricated by the arc discharge techniques using Cr-Al-Si and graphite cathodes were studied. X-ray photoelectron spectroscopy, X-ray energy-dispersive spectroscopy, nuclear reactions, and Rutherford backscattering methods were applied to determine composition of the coating, X-ray diffraction and transmission electron microscopy — to investigate the structure of the coating. Corrosion tests were performed in an electrochemical cell in a 3.5 % NaCl solution. Depletion of the cathode surface of chromium, screening of Cr+ by C+ in plasma, and selective etching of the coating upper layers are accompanied by a decrease of Cr / (Al + Si) ratio in the coatings compared to the cathode. The carbon content (CC) in CrxAl(Si)yC, determined by XPS, EDS and NR, differs by several times. The CC measured by NR correlates with the results of Raman spectroscopy and confirms the existence of a continuous carbon matrix in CrxAly(Si)C. Cr is chemical bonded with carbon, silicon — with carbon and aluminum. The Al-Si system provides the structure feature of CrxAl(Si)yC: a network of aluminum intersects the amorphous matrix. The mechanical mismatch and weak bond between the Al structures and the amorphous matrix may be the reason for the formation of defects in the form of cracks and microchannels along the boundaries.

Nickel silicide formation with rapid thermal treatment in the heat balance mode

The formation of nickel silicide layers on (111)-Si substrates during rapid thermal annealing in the heat balance mode was studied by the Rutherford backscattering method, X-ray diffraction, transmission electron microscopy, and electrophysical measurements. Nickel films of about 70 nm thickness were deposited by magnetron sputtering at room temperature. The rapid thermal treatment was carried out in a heat balance mode by irradiating the substrates backside with a non-coherent light flux of quartz halogen lamps in the nitrogen medium for 7 seconds up to the temperature range of 200 to 550 °C. The redistribution of nickel and silicon atoms to monosilicide NiSi composition starts already at a temperature of 300 °С and almost ends at a temperature of 400 °С. In the same temperature range, the orthorhombic NiSi phase with an average grain size of about 0.05–0.1 μm is formed. At a rapid thermal treatment temperature of 300 °C, two phases of silicides (Ni2 Si and NiSi) are formed, while a thin layer of unreacted Ni is retained on the surface. This fact can be explained by the high heating rate at the initial annealing stage, at which the temperature conditions of the NiSi phase formation occur earlier than the entire Ni layer manages to turn into the Ni2 Si phase. The layers with a simultaneous presence of three phases are characterized by a high roughness of the silicide-silicon interface. The dependence of the specific resistivity of nickel silicide layers shows an increase to the values of 26–30 μOhm · cm in the range of rapid thermal treatment temperatures of 200–250 °C and a subsequent decrease to the values of about 15 μOhm · cm at a rapid thermal treatment temperature of 400 °C. This value of specific resistivity is characteristic of the high conductivity of the NiSi phase and correlates well with the results of structure studies.

Surface micromorphology analysis of Cu/Ni nanocomposite thin films by power spectra density and fractal geometry

Abstract Copper (Cu) and nickel (Ni) nanoparticles have been grown simultaneously on glass and silicon substrates by RF sputtering method to form three Cu/Ni nanocomposites at different deposition times. The existence of Cu and Ni peaks in the X-ray diffraction (XRD) profiles confirms the crystalline structure of samples with Cu and Ni atomic content which have also been characterized by Rutherford backscattering (RBS) method. Moreover, the structural and morphological properties of the prepared nanocomposites have been compared with respect to their morphologies by means of atomic force microscopy (AFM) analysis. In order to compare the surface roughness over different spatial frequency ranges and evaluate surface quality, power spectral density (PSD) of each sample has been extracted from AFM data and also, the experimental and theoretical results have been compared. The fractal nature of these nanocomposites has been finally discussed.

Materials analysis by ion channeling at "Demokritos"

A new fully automated Goniometer system installed recently at the Institute of Nuclear Physics of "Demokritos" is presented. This system enables to perform materials analysis not only via the Rutherford Backscattering method, which has been used so far at "Demokritos", but also by the ion channeling technique. The first experiments carried out using the Goniometer are also presented.

Iron ions distribution profile obtained by irradiating the silicon single crystal

Iron ions with energies of 90 and 250 keV and the irradiation dose of 1016 ions/cm2 and xenon ions with energies of 100 keV and dose 7,7×1014 cm-2, 200 keV and dose 2,6 × 1014 cm-2 were implanted in the single crystal of silicon (110). The distribution profiles of implanted impurity, as well as the distribution profiles of the radiation defects in the crystal lattice, were studied by the Rutherford backscattering method in combination with channeling. The experimental results were compared with the results of simulations of binary collisions of the Monte Carlo method in the TRIM program. It is shown that the difference between the experimental data and the calculation program TRIM is more than 35% in all cases.

Engineering strain to achieve stable 92Zr targets on carbon backing

Importance of substrate heating for fabrication of strong zirconium targets (92Zr) has been discussed. The targets have been prepared using experimental facilities of target laboratory at Inter University Accelerator Centre (IUAC), New Delhi, India. Substrate heating has been tried for the first time for the fabrication of carbon backed zirconium targets. The heating of substrate exhibited improved stability, longevity and a better success rate of production of targets. In addition, a large number of wrinkle-free targets have been obtained using this technique. Elemental analysis has been performed to determine purity of the targets with X-ray fluorescence and Rutherford back-scattering spectrometry methods. These targets have successfully survived against high flux heavy ion bombardment viz. 14N and 28Si.

Beryllium-tungsten study on mixed layers obtained by m-HiPIMS/DCMS techniques in a deuterium and nitrogen reactive gas mixture

Beryllium-tungsten 2μm thick layers were co-deposited on molybdenum, graphite and silicon substrates in a reactive argon-deuterium/argon-deuterium-nitrogen gas mixture by means of combining multi-pulse High Power Impulse Magnetron Sputtering and Direct Current Magnetron Sputtering techniques. The elemental composition and thickness of the layers were well controlled during the deposition process. Structural and chemical investigations were undertaken by means of X-ray diffraction and Rutherford backscattering methods. The results showed a change in the samples structure with the adding of nitrogen into the sputtering gas mixture, evidenced by the appearance of W2N peaks in the diffraction patterns. The RBS showed in-depth uniformity of beryllium and tungsten concentrations for the deposited coatings. In order to investigate the deuterium retention mechanisms and to make an assessment of the deuterium inventory, thermal desorption spectrometry was performed. The deuterium desorption spectra for the batch of samples obtained with nitrogen showed an obvious behaviour of shifting to higher temperatures. This behaviour may be related to the nitrogen desorption.

Formation of ZnSe nanoclusters in the layers of silicon dioxide by high-fluence ion implantation and annealing

In this work we used the method of hot implantation of zinc and selenium ions into SiO2/Si structures in combination with subsequent heat treatment in order to form nanosized phases. Implantation modes for ionic synthesis chosen in such a way that the concentration of the embedded impurity is maximum approximately at the middle of the thickness of the dielectric layer. For the subsequent clustering of the impurity, it is necessary to create a high concentration of the implanted impurity at the maximum of the depth profile. The computer stimulation to select Implantation modes was carried out using the SRIM- 2013 program. Also we calculated the thickness of the silicon dioxide layer sprayed during high-dose implantation of zinc ions was. In this way, we have studied the formation of ZnSe precipitates in silicon dioxide by means of Zn (150 keV, 4×1016 cm−2) and Se (170 keV, 4×1016 cm−2) implantation at 550 °C and subsequent annealing at 1000 °C for 3 min. From analysis of XTEM images it has been showen that the use of hot implantation leads to the formation of small nanoclusters with sizes from 2 to 15 nm. Subsequent annealing results in the redistribution of nanoclusters within the implanted layer and the formation of large crystallites (up to 80 nm). To analyze the distribution of the introduced impurity throughout the sample depth the Rutherford backscattering (RBS) method was used. The band at 251-256 cm-1 associated with LO phonons of crystal ZnSe was registered in Raman spectra.

Structure and hardness of quaternary TiZrSiN thin films deposited by reactive magnetron co-sputtering

The addition of Si into (Ti,Zr)N films is considered to be perspective for their hardness enhancement as well as improvement of oxidation and wear resistance. In the present work, the influence of the silicon content and deposition temperature (270 and 600°C) on the structural and mechanical properties of magnetron sputtered TiZrSiN films is investigated. The elemental composition was determined by Rutherford backscattering and wavelength dispersive X-ray spectrometry methods, the structure and phase formation were analyzed by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Depending on Si content, x, and deposition temperature, Ts, (Ti,Zr)1−xSixNy films were formed in the following states: i) single-phase, cubic (Ti,Zr)N solid solution, ii) dual-phase nanocomposite consisting of nanograins of c-(Ti,Zr)N solid solution surrounded by an amorphous SiNz phase, iii) amorphous phase. Higher deposition temperature (Ts=600°C) promotes the formation of nanocomposite structure and reduces the intrinsic compressive stress. The maximum hardness values (26–29GPa) are observed when Si content is in the range 0.07≤x≤0.15 for both deposition temperatures.

Optical properties of pseudomorphic Ge1−xSnx (x = 0 to 0.11) alloys on Ge(001)

The characterization of the optical properties of pseudomorphic Ge1−xSnx/Ge/Si (x = 0 to 0.11) alloys from the IR to UV is presented. The Ge1−xSnx alloys were epitaxially grown on relaxed Ge grown on Si. Rutherford backscattering (RBS) and RBS ion channeling methods were used to confirm the Sn composition and substitutional nature of the Sn into the Ge lattice. The pseudomorphic nature of the Ge1−xSnx on Ge is confirmed using high resolution x-ray diffraction (HRXRD) and transmission electron microscopy. Although HRXRD reciprocal space maps indicated that the Ge1−xSnx was pseudomorphic to Ge, the shape of the Bragg peaks indicated that the sample surface was rough. The rough surface morphology is confirmed using atomic force microscopy. The complex dielectric function is reported in the IR, visible, and UV spectrum in the wavelength range of 0.2–5.06 eV. The E1, E1 + Δ1, E2, and E0 critical points are extracted using second and third derivative line shape fitting and are compared with the elastic theory calculations of strained Ge1−xSnx (x = 0 to 0.11) alloys and fully relaxed Ge1−xSnx (x = 0 to 0.11) alloys. The E0 critical point energies are observed to have slightly larger values than those calculated for completely relaxed Ge1−xSnx alloys due to the presence of compressive strain.

The interaction potential of the He+-Au system determined from Rutherford backscattering data

The potential-internuclear-distance dependences for the He+-Au system are obtained by processing measurements of particle scattering cross sections at various collision energies. The potential is shown to be independent of the collision velocity. The values obtained made it possible to introduce a correction for the difference of the above potential from the Coulomb one involved in the Rutherford backscattering method, and thus to improve the measurement accuracy. The obtained data on the screening constants enable estimation of the screening effect on the increase in the nucleosynthesis cross sections.

Doslidzhennya metodamy yadernoho mikroanalizu poverkhnevykh nanoshariv struktury zoloto−kremniy

The Rutherford backscattering and particle-induced X-ray emission methods are used to study the surface layers in gold–silicon structures, the parameters of which govern the operational characteristics of electron devices constructed on their basis. The measurements are performed on a high-precision microanalytical unit “Nuclear scanning probe” recently put into operation at the “Spectrum” laboratory. The thicknesses of a gold layer sputtered onto the specimen surface were about 17 and 20 nm for two different specimens. The layer non-uniformity was less than 1.6 nm and did not exceed the experimental error. A substantial amount of the fluorine impurity was revealed under the gold layer in the gold–silicon interface layer. Probably, it may be remnants of fluorine remaining after the etching of the silicon surface in a mixture of acids that included the hydrofluoric one (HF). The amount of fluorine detected in a series of measurements was found to strongly correlate with the current of alpha-particles at the target surface during the spectrum measurement. Since the local heating of the target depends on the current, it is evident that the local diffusion rate of fluorine atoms varied over the target surface.

Early stages of growth of gold layers sputter deposited on glass and silicon substrates

Extremely thin gold layers were sputter deposited on glass and silicon substrates, and their thickness and morphology were studied by Rutherford backscattering (RBS) and atomic force microscopy (AFM) methods. The deposited layers change from discontinuous to continuous ones for longer deposition times. While the deposition rate on the silicon substrate is constant, nearly independent on the layer thickness, the rate on the glass substrate increases with increasing layer thickness. The observed dependence can be explained by a simple kinetic model, taking into account different sticking probabilities of gold atoms on a bare glass substrate and regions with gold coverage. Detailed analysis of the shape of the RBS gold signal shows that in the initial stages of the deposition, the gold layers on the glass substrate consist of gold islands with significantly different thicknesses. These findings were confirmed by AFM measurements, too. Gold coverage of the silicon substrate is rather homogeneous, consisting of tiny gold grains, but a pronounced worm-like structure is formed for the layer thickness at electrical continuity threshold. On the glass substrate, the gold clusters of different sizes are clearly observed. For later deposition stages, a clear tendency of the gold atoms to aggregate into larger clusters of approximately the same size is observed. At later deposition stages, gold clusters of up to 100 nm in diameter are formed.

Investigation of Optical Properties of ZnO Films Deposited by RF Magnetron Sputtering

ZnO thin films with a strong c-axis orientation have been successfully deposited on quartz glass substrates at room temperature by radio frequency (rf) magnetron sputtering technology. X-ray diffraction, Rutherford backscattering, and prism coupling method were used to investigate the structure and optical properties of ZnO thin films. X-ray diffraction results shown lower sputtering pressure is propitious to increasing the crystallinity, and enhancing the c-axis orientation of the films. Rutherford backscattering analysis revealed that the films were stoichiometric ZnO, and as the sputtering pressure decreasing, the deposition rate were increased from 0.758 3nm/min to 2.892 nm min for sputtering pressure in the range from 1.0Pa to 0.5Pa. Under the lower sputtering pressure (0.5Pa) condition, the results obtained by prism coupling method investigation confirmed that the effective refractive index of ZnO films (no=1.8456，ne=1.8276) at a wavelength of 633nm is more close to Crystal Refractive index.

Interdiffusion Analysis of Au/Ti and Au/Pt/Ti Electrode Structures Grown on Diamond (001) Surface by Rutherford Backscattering Spectroscopy

We have directly studied the elemental depth profiles of Au/Ti and Au/Pt/Ti multiple-layers, which are candidates as ohmic materials for a p-type diamond substrate, grown on diamond (001) surfaces at room temperature (RT) and 550 °C using Rutherford backscattering method. Significant interlayer diffusion between Au and Ti is observed for the samples without a sandwiched Pt layer, resulting in diffusion of some Ti atoms to the surface. On the other hand, the trilayer structure of Au/Pt/Ti forms a thermally stable electrode up to 1000 °C. It is also found that the interfacial TiCx layer grown at 550 °C is thicker than that deposited at RT followed by post-deposition annealing at 550 °C. The effective thickness of the Pt layer is estimated to be more than 20 nm to prevent Ti segregation to the surface.

Deposition of hard thin films from HMDSO in atmospheric pressure dielectric barrier discharge

An atmospheric pressure dielectric barrier discharge burning in nitrogen with a small admixture of hexamethyldisiloxane (HMDSO) was used for the deposition of thin organosilicon films. The thin films were deposited on glass, silicon and polycarbonate substrates, and the substrate temperature during the deposition process was increased up to values within the range 25–150 °C in order to obtain hard SiOx-like thin films. The properties of the discharge were studied by means of optical emission spectroscopy and electrical measurements. The deposited films were characterized by the Rutherford backscattering and elastic recoil detection methods, x-ray photoelectron spectroscopy, infrared spectroscopy measurements, ellipsometry and the depth sensing indentation technique. It was found that the films' properties depend significantly on the substrate temperature at deposition. An increase in substrate temperature from 25 to 150 °C led to an increase in film hardness from 0.4 to 7 GPa and the film chemical composition changed from CHxSiyOz to SiOxHy. The films were transparent in the visible range.

IBA of ZrO2:Yb/Si thin films produced by the spray pyrolysis method

A spray pyrolysis method was used to produce thin films of ZrO2 doped with different Yb concentrations on Si(100). The films of these ionic semiconductors have potential applications as solid electrolytes in modern ceramic fuel cells of second generation. The determination of the atomic composition of the films is very important because it strongly affects the chemical and thermal stability, as well as electrical properties of the films. A combination of two Ion Beam Analysis (IBA) methods was applied to obtain the atomic composition of the films. A nuclear reaction analysis (NRA) method using a low energy deuterium beam was applied to measure the oxygen content of the films. Heavy ion Rutherford backscattering (HI-RBS) method using a 12C3+ beam was applied to measure the Yb and Zr atomic profiles of the samples. X-ray diffraction (XRD) and ellipsometry were also employed to determine structural properties and refractive index of the films, respectively. The IBA, XRD and the ellipsometry supply a wide range of information about the film layers, which can be used for qualification as well as for feedback to the films production.