non-Rutherford Backscattering Spectrometry Research Articles

Nanoscale Control of Structure and Composition for Nanocrystalline Fe Thin Films Grown by Oblique Angle RF Sputtering.

The use of Fe films as multi-element targets in space radiation experiments with high-intensity ultrashort laser pulses requires a surface structure that can enhance the laser energy absorption on target, as well as a low concentration and uniform distribution of light element contaminants within the films. In this paper, (110) preferred orientation nanocrystalline Fe thin films with controlled morphology and composition were grown on (100)-oriented Si substrates by oblique angle RF magnetron sputtering, at room temperature. The evolution of films key-parameters, crucial for space-like radiation experiments with organic material, such as nanostructure, morphology, topography, and elemental composition with varying RF source power, deposition pressure, and target to substrate distance is thoroughly discussed. A selection of complementary techniques was used in order to better understand this interdependence, namely X-ray Diffraction, Atomic Force Microscopy, Scanning and Transmission Electron Microscopy, Energy Dispersive X-ray Spectroscopy and Non-Rutherford Backscattering Spectroscopy. The films featured a nanocrystalline, tilted nanocolumn structure, with crystallite size in the (110)-growth direction in the 15–25 nm range, average island size in the 20–50 nm range, and the degree of polycrystallinity determined mainly by the shortest target-to-substrate distance (10 cm) and highest deposition pressure (10−2 mbar Ar). Oxygen concentration (as impurity) into the bulk of the films as low as 1 at. %, with uniform depth distribution, was achieved for the lowest deposition pressures of (1–3) × 10−3 mbar Ar, combined with highest used values for the RF source power of 125–150 W. The results show that the growth process of the Fe thin film is strongly dependent mainly on the deposition pressure, with the film morphology influenced by nucleation and growth kinetics. Due to better control of film topography and uniform distribution of oxygen, such films can be successfully used as free-standing targets for high repetition rate experiments with high power lasers to produce Fe ion beams with a broad energy spectrum.

Growth and characterization of W thin films with controlled Ne and Ar contents deposited by bipolar HiPIMS

This work is focused on controlling and optimizing the inclusion of neon (Ne) and argon (Ar) impurities in tungsten (W) reference coatings. A tungsten target has been sputtered in monopolar and bipolar High Power Impulse Magnetron Sputtering (HiPIMS) operation modes, in Ar-Ne gas mixture. It has been found that the process of noble gas retention in W thin layers is strongly dependent on both ion energy and average flux to the substrate. The ion energy can be accurately controlled by the amplitude of the positive voltage pulse while the average ion flux can be controlled by the duration of the negative pulse. Measurements of the plasma potential in front of the substrate and the ion saturation current at the substrate position allow explaining the mechanism of ion acceleration and the control of ion energy and flux. The effect of the pulsing configuration on the microstructure of the co-deposited films has been investigated by X-ray Diffractometry, Scanning Electron Microscopy and Atomic Force Microscopy, while the amount of noble gas enclosed in the coatings has been measured by Non-Rutherford Backscattering Spectrometry. Ne and Ar amount in the W co-deposited layers increases up to 3.0 at.% each as the amplitude of the positive pulse increases to + 300 V or the negative pulse duration decreases to 3 µs. The highest film crystallinity, with W(1 1 0) preferential growth, has been obtained for a positive pulse voltage of + 200 V and a negative pulse duration of 5 µs. The thickness of the deposited layers ranges between 350 nm in bipolar HiPIMS with a positive pulse voltage of + 300 V and 550 nm in monopolar HiPIMS.

Electrochemical Behavior of Composite Nanoparticles on the Corrosion of Mild Steel in Different Media

Zn0.97Mn0.03O and Zn0.87Mn0.03Fe0.1O nanoparticles have been synthesized using co-precipitation technique. The obtained nanoparticles were characterized by X-ray diffraction, and transmission electron microscopy. The elemental contents of the prepared nanoparticles were determined using particle-induced X-ray emission. Besides, the oxygen content of these nanoparticles was determined using non-Rutherford backscattering spectroscopy. The electrochemical behaviour of 10 ppm nanoparticles on the corrosion of mild steel in 0.5 M HCl and 0.5 M NaCl solutions containing 1% SDS was studied using potentiodynamic polarization curve measurements and electrochemical impedance spectroscopy techniques. The mechanism of inhibition of the studied nanoparticles was discussed and explained. Iron containing nanoparticles enhanced the corrosion protection of mild steel in 0.5 M HCl due to the ability of Fe2+ to deposit onto metal surface. However, in neutral 0.5 M NaCl medium, both nanoparticles have approximately similar efficiency.

Effect of oxygen content on CO2 absorption characteristics of Li2TiO3

In order to investigate the CO2 absorption characteristics of the low- and high-density Li2TiO3 samples, X-ray diffraction (XRD), non-Rutherford backscattering spectroscopy (NRBS) and elastic recoil detection (ERD) analyses have been performed. Crystallographic structure of a sintered and CO2 exposed samples is decided by the XRD analysis, and the NRBS and ERD analyses have evaluated the amount of CO2 absorption and H content quantitatively. The CO2 absorption characteristics of the non-stoichiometric Li2TiO3 sample are investigated. It is found that the CO2 absorption rate of the non-stoichiometric Li2TiO3 sample is much larger than that of the stoichiometric sample. The Li2TiO3 sample (80%T.D.) has a good tritium release characteristics, and we find also that the sample sintered at temperatures higher than 1,428 K absorb very little CO2 under high humidity conditions. The amount of CO2 absorption of the low-density Li2TiO3 samples is found to increase with increase in the humidity. This seems to be a catalytic effect of water vapor on CO2 absorption at the Li2TiO3 surface.

Fabrication of p-Type ZnO:N Films by Oxidizing Zn₃N₂ Films in Oxygen Plasma at Low Temperature.

The oxygen vacancy (VO) is known as the main compensation center in p-type ZnO, which leads to the difficulty of fabricating high-quality p-type ZnO. To reduce the oxygen vacancies, we oxidized Zn3N2 films in oxygen plasma and successfully prepared p-type ZnO:N films at temperatures ranging from room temperature to 300 °C. The films were characterized by X-ray diffraction (XRD), non-Rutherford backscattering (non-RBS) spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectrum, and Hall Effect. The results show that the nitrogen atoms successfully substitute the oxygen sites in the ZnO:N films. The film prepared at room temperature exhibits the highest hole concentration of 6.22 × 1018 cm−3, and the lowest resistivity of 39.47 Ω∙cm. In all ZnO:N films, the VO defects are reduced significantly. At 200 °C, the film holds the lowest value of VO defects and the strongest UV emission. These results imply that oxygen plasma is very efficient in reducing VO defects in p-type ZnO:N films, and could greatly reduce the reaction temperature. This method is significant for the development of ZnO-based optoelectronic devices.

CO2 absorption characteristics of a blanket candidate material Li2TiO3 under exposure to different gas mixture

In order to investigate the CO2 absorption characteristics of the low- and high-density Li2TiO3 samples, X-ray diffraction (XRD) and non-Rutherford backscattering spectroscopy (NRBS) analyses have been performed. Crystallographic structure of a sintered sample is decided by the XRD analysis, and the NRBS analysis has evaluated the amount of CO2 absorption quantitatively. The amount of CO2 absorption of the low-density Li2TiO3 samples is increased with increase of the humidity. We find that the humidity has effect on CO2 absorption to the low-density Li2TiO3 samples. On the other hand, the high-density samples sintered at temperatures higher than 1,470K absorb very little CO2 under high humidity conditions.

P-Type Nitrogen-Doped ZnO Films Prepared by In-Situ Thermal Oxidation of Zn3N2 Films**Supported by the National Natural Science Foundation of China under Grant Nos 10775033 and 11075038.

P-type nitrogen-doped ZnO films are prepared successfully by in-situ thermal oxidation of Zn3N2 films. The prepared films are characterized by x-ray diffraction, non-Rutherford backscattering (non-RBS) spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence spectrum. The results show that the Zn3N2 films start to transform to ZnO at 400°C and the total nitrogen content decreases with the increasing annealing temperature. The p-type films are achieved at 500°C with a low resistivity of 6.33Ω·cm and a high hole concentration of +8.82 × 1017 cm−3, as well as a low level of carbon contamination, indicating that the substitutional nitrogen (NO) is an effective acceptor in the ZnO:N film. The photoluminescence spectra show clear UV emissions and also indicate the presence of oxygen vacancy (VO) defects in the ZnO:N films. The p-type doping mechanism is briefly discussed.

Ion Beam Analysis and Electric Properties of GdBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB> Added with Nanosized Ferrites ZnFe<SUB>2</SUB>O<SUB>4</SUB> and CoFe<SUB>2</SUB>O<SUB>4</SUB>

In this study, superconducting samples of type GdBa2Cu3O7-δ added with x wt% (0 ≤ x ≤ 0.4) nanoferrites ZnFe2O4 and CoFe2O4 were prepared by the conventional solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) in order to determine the volume fraction and lattice parameters. The elemental contents of the prepared samples were determined using particle induced X-ray emission (PIXE). In addition, the oxygen-content of these samples was obtained using non-Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. It is found that the Oxygen-content of GdBa2Cu3O7-δ phase remains practically constant for low additions of both nanoferrites but it increases with high additions. The electrical resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the zero superconducting transition temperature (T0). An increase in the superconducting transition temperature Tc and the critical current density Jc is observed as x varies from 0.0 to 0.06 wt% of (ZnFe2O4)xGdBa2Cu3O7-δ, followed by a systematic decrease with increasing x. On the other hand, the Tc values for (CoFe2O4)xGdBa2Cu3O7-δ show a systematic decrease with x for both high and low additions while Jc is enhanced up to x = 0.01 wt% and decrease with further increase in x.

CO2 absorption characteristics of a Li2TiO3 blanket material under atmospheric exposure

Non-Rutherford backscattering spectroscopy (NRBS) for the composition analysis and X-ray diffraction (XRD) for the crystallographic structure analysis have been applied to the blanket candidate material, Li2TiO3, which is known to absorb CO2 though chemically stable. It is found that the amount of CO2 absorbed by atmospheric exposure of the low- and medium-density samples is greater than or comparable to that by dry CO2 gas exposure. By varying the density of the Li2TiO3 and composition of the ambient gas, conditions to minimize the amount of CO2 absorbed are discussed.

Magnetoresistance Study of Y3Ba5Cu8O18 Superconducting Phase Substituted by Nd3+ and Ca2+ Ions

Superconducting samples of type Y3−x Nd x Ba5−x Ca x Cu8O18 with 0.0 ≤ x ≤ 0.4 have been prepared via the solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) technique for phase analysis. The elemental content of the prepared samples was determined using particle-induced X-ray emission (PIXE). In addition, the oxygen content of these samples was obtained using non-Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. The results indicate that these substitutions do not affect the orthorhombic structure, while they decrease the oxygen content of Y-358 phase. The electrical resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the zero superconducting transition temperature (T 0). A slight change in the superconducting transition temperature (T c) is observed for 0 ≤ x ≤ 0.1, and then it decreases linearly with further increase in x. The linear decrease in T c is attributed mainly to the partial substitution of Ba2+ ions by Ca2+ ions rather than the partial substitution of Y3+ ions by Nd3+ ions. The effect of magnetic fields up to 4.44 kG on the electrical resistivity has been studied to investigate the vortex dynamics for the prepared samples. The experimental data, in the second stage of superconducting transition, fit well with the thermally activated flux creep (TAFC) model, and the activation energy U(B) shows a power law dependence on magnetic field as B −β . Also, the transition width is related to the magnetic field according to the relation ΔT α B n . The values of β and n are strongly dependent on the Nd3+ and Ca2+ ion substitution. The magnetic field and temperature dependence of the activation energy U(B, T) is found to be U(B, T)˜ ΔT B −η , where η = β + n. Furthermore, the critical current density at zero temperature, J c(0), as a function of the applied field was calculated for all the prepared samples. The result shows an enhancement in J c(0) of Y-358 phase at x equals 0.4 at different applied fields.

Ion beam analyses for Li2TiO3 blanket candidate material

Combined NRBS (non-Rutherford backscattering spectroscopy) and NRA (nuclear reaction analysis) methods have been applied to Li2CO3 samples with Li of various isotopic compositions. Densities of the component elements as well as the isotopic composition of Li have been determined within an error of about 10% or less. The NRBS method has also been applied to a high-density Li2TiO3 sample to investigate double-shell formation under CO2 absorption. By showing appearance of a Ti-free layer on the sample surface, usefulness of the method for investigation of the mechanism of the double-shell formation is demonstrated.

Composition change of the near-surface layer of Li2TiO3 after CO2 absorption observed with accelerator analyses

Non-Rutherford backscattering spectroscopy (NRBS), which allows for a greatly enhanced cross section for scattering, was used to analyze the atomic composition of Li-containing blanket material, 2.6-MeV proton beams were used as the probe beam to profile the atomic composition in the near-surface region down to about 2μm.Li2TiO3 ceramics samples of various densities were exposed to CO2 gas at a pressure of 1atm at room temperature in a glove box. The absorption of CO2 was observed to result in the formation of Li2CO3 on these samples in the NRBS spectra. In low and medium density samples, the density ratio of the absorbed CO2 to Li2TiO3 reached 0.5 after 1800h and CO2 absorption showed a saturation tendency of about 1400h.Li2TiO3 structures without CO2 were recovered by heating samples to 973K, with a residual positive volume change of 10%. The structure appeared to have increased capacity for CO2 absorption with an expanded near-surface layer. This characteristic could present a problem in the process of tritium recovery from the blanket materials.

Effect of chromium underlayer on the properties of nano-crystalline diamond films

This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

Preparation and characterization of Al2O3–MgO catalytic supports modified with lithium

Al2O3–MgO catalytic supports were modified with different amounts of lithium in order to obtain novel Al2O3–MgO–Li(x) formulations containing basic sites. The basic sites on samples surface were identified and quantified through CO2 chemisorptions. It was found that total amount of basic sites increases as the Li content increases. The Li identification and its content were performed through Non-Rutherford Backscattering Spectroscopy (NRBS). The Li addition to the supports produce surface morphological changes as was observed with Scanning Electron Microscopy (SEM). The addition of lithium produces a decrease in specific surface area, changing the textural properties as N2-physisorption measurements reveal. Structural characterization by X-ray diffraction (XRD) suggests that Li addition changes the crystalline structure of Al2O3 from the γ to the δ phase; additionally, this technique indicate the presence of Li2CO3, which could be attributed to the preferential reaction of Li with environmental CO2. It was not found evidence of magnesium carbonates in the fresh samples by XRD. Raman spectroscopy shows bands attributed to the lithium carbonates species corroborating the found by XRD. The obtained results suggest that these materials could be potentially attractive as catalytic supports for reactions where the basic sites are useful such as selective hydrodesulphurization.

Accurate Determination of Quantity of Material in Thin Films by Rutherford Backscattering Spectrometry

Ion beam analysis (IBA) is a cluster of techniques including Rutherford and non-Rutherford backscattering spectrometry and particle-induced X-ray emission (PIXE). Recently, the ability to treat multiple IBA techniques (including PIXE) self-consistently has been demonstrated. The utility of IBA for accurately depth profiling thin films is critically reviewed. As an important example of IBA, three laboratories have independently measured a silicon sample implanted with a fluence of nominally 5 × 10(15) As/cm(2) at an unprecedented absolute accuracy. Using 1.5 MeV (4)He(+) Rutherford backscattering spectrometry (RBS), each lab has demonstrated a combined standard uncertainty around 1% (coverage factor k = 1) traceable to an Sb-implanted certified reference material through the silicon electronic stopping power. The uncertainty budget shows that this accuracy is dominated by the knowledge of the electronic stopping, but that special care must also be taken to accurately determine the electronic gain of the detection system and other parameters. This RBS method is quite general and can be used routinely to accurately validate ion implanter charge collection systems, to certify SIMS standards, and for other applications. The generality of application of such methods in IBA is emphasized: if RBS and PIXE data are analysed self-consistently then the resulting depth profile inherits the accuracy and depth resolution of RBS and the sensitivity and elemental discrimination of PIXE.

Effect of nitrogen addition on hydrogen incorporation in diamond nanorod thin films

The effect of nitrogen addition in the feed gas on the finally incorporated amount of hydrogen in the diamond nanorods (DNRs) thin films has been investigated. The Raman spectroscopy measurements helped to understand the structural and quality changes with increasing nitrogen gas flow rate during CVD deposition. The hydrogen concentration was measured with 3.0 MeV He2+ beam using elastic recoil detection analysis technique and it was found that with the addition of nitrogen, the hydrogen concentration was increased. The results of non-Rutherford backscattering spectroscopy (NRBS) used to measure the amount of nitrogen in the DNRs thin films have shown that the incorporated nitrogen is below the detection limit of NRBS technique. Our results suggested that the addition of nitrogen has affected the overall quality of diamond films in two ways; increasing the thickness of diamond films by increasing the non-diamond carbon content and increasing the hydrogen impurity incorporation. The role of nitrogen additive on diamond growth and hydrogen incorporation is discussed.

Microstructural characterization of Ti–C–N thin films prepared by reactive crossed beam pulsed laser deposition

In this work, Raman spectroscopy has been used to characterize Ti–C–N thin films in order to obtain information about the microstructure of the deposited materials, and in particular to study the effects due to the carbon incorporation into the TiN lattice. Ti–C–N thin films were prepared using a crossed plasma configuration in which the ablation of two different targets, titanium and carbon, in a reactive atmosphere was performed. With this configuration, the carbon content in the films was varied in an easy way from 5.0 at% to 40.0 at%. Thin film composition was determined from Non-Rutherford Backscattering Spectroscopy (NRBS) measurements. X-ray photoelectron spectroscopy and X-Ray diffraction measurements were also carried out in order to characterize the films in more detail, with this being used to give support to the interpretation of the Raman spectra. The Raman results revealed that at lower carbon concentrations a solid solution Ti(C, N) is formed, whilst at higher carbon concentrations a nanocomposite, consisting of nanocrystalline TiCN and TiC immersed in an amorphous carbon matrix is obtained.

High-energy heavy ion beam annealing effect on ion beam synthesis of silicon carbide

Silicon carbide (SiC) is a superior material potentially replacing conventional silicon for high-power and high-frequency microelectronic applications. Ion beam synthesis (IBS) is a novel technique to produce large-area, high-quality and ready-to-use SiC crystals. The technique uses high-fluence carbon ion implantation in silicon wafers at elevated temperatures, followed by high-energy heavy ion beam annealing. This work focuses on studying effects from the ion beam annealing on crystallization of SiC from implanted carbon and matrix silicon. In the ion beam annealing experiments, heavy ion beams of iodine and xenon, the neighbors in the periodic table, with different energies to different fluences, I ions at 10, 20, and 30 MeV with 1–5 × 10 12 ions/cm 2, while Xe ions at 4 MeV with 5 × 10 13 and 1 × 10 14 ions/cm 2, bombarded C-ion in implanted Si at elevated temperatures. X-ray diffraction, Raman scattering, infrared spectroscopy were used to characterize the formation of SiC. Non-Rutherford backscattering and Rutherford backscattering spectrometry were used to analyze changes in the carbon depth profiles. The results from this study were compared with those previously reported in similar studies. The comparison showed that ion beam annealing could indeed induce crystallization of SiC, mainly depending on the single ion energy but not on the deposited areal density of the ion beam energy (the product of the ion energy and the fluence). The results demonstrate from an aspect that the electronic stopping plays the key role in the annealing.

Silicon carbide thin films as nuclear ceramics grown by laser ablation

Silicon carbide has been identified as a potential inert matrix candidate for advanced fuel. In this work, the growth of SiC thin films by pulsed laser deposition is reported. The stoicheometry and thickness of deposited films was investigated by non-Rutherford backscattering spectrometry. The influence of the deposition parameters, i.e. substrate temperature and laser fluence on the structure, morphology and optical properties of the deposited thin layers was studied. It was found that polycrystalline SiC thin films with uniform surface morphology were obtained at 873 K.

TiCN thin films grown by reactive crossed beam pulsed laser deposition

In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration, titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium and graphite targets in an Ar/N2 atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa. With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence on the carbon target.