Rutherford Backscattering Spectra Research Articles

Quantitative characterization of occupational sites of implanted P atoms in diamond

The authors implanted P atoms at 50 and 140-keV energies with respective fluences of 1×1014 and 2×1014/cm2 into diamond thin films synthesized by chemical vapor deposition on the type-Ib diamond substrate formed by high-pressure and high-temperature conditions. The occupational sites of implanted P atoms were determined in each processing stage of P implantation, ion-beam-induced epitaxial crystallization (IBIEC) annealing by 3-MeV-Ne2+ ion irradiation at 750°C, and thermal annealing at 850°C in vacuum, by quantitatively comparing the random and channeling yields in Rutherford backscattering (RBS) measurements. In the analysis of RBS spectra, simulated distributions were fitted to the experimentally obtained spectra and we quantitatively identified the occupational sites and ratio of implanted P atoms. In addition, we investigated the diffusion phenomenon of implanted P atoms during annealing processes from the depth profile of scattered He ions. Consequently, the averaged occupational ratio in the substitutional lattice site was stably recorded around 50%. From the depth profile in the RBS spectra, thermal diffusion of implanted P atoms was clearly observed during the last thermal annealing after MeV-IBIEC annealing. We finally discuss the potentials of the MeV-IBIEC irradiation at relatively low temperatures applying to useful and credible annealing methods for electrical activation as well as recovery of damaged crystallinity.

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.

Correlated characterization of 20Ne-implanted targets using nuclear reaction analysis, Rutherford backscattering spectrometry, and ion transport modeling

We present the preparation and characterization of a large sample of implanted noble gas targets for use in precision nuclear astrophysics measurements with intense proton beams. Tantalum and titanium backings were prepared using wet-acid etching, outgassed via resistive heating, and implanted with 20Ne+ beams from differing ion sources. These experimental targets were investigated using both nuclear reaction analysis techniques on the 1169-keV resonance in 20Ne(p, γ)21Na and Rutherford backscattering spectrometry analysis with 2-MeV α-particle beams. Results from these analyses reveal small target-to-target variations in stoichiometry, while exhibiting excellent agreement independent of ion-beam analysis method. We also present a self-consistent validation of the nuclear reaction analysis results using ion transport simulations in TRIM-2013 that rely on input parameters from SIMNRA scattering-yield fits to Rutherford backscattering spectra. In addition to a complete description of the implantation profile, this analysis method provides an alternate solution for characterizing a large sample of implanted targets when no suitable resonances are available for nuclear reaction analysis.

Effect of growth temperature and Sb over in flux ratio on the Bi content and the surface morphology of InSbBi grown by molecular beam epitaxy

We investigated the effect of VSb/IIIIn flux ratio and growth temperature on the Bi content of InSbBi material grown on an InSb substrate using molecular beam epitaxy. The Rutherford backscattering spectrum from a bulk InSb0.977Bi0.023 epitaxial film showed a 98.5% substitutional site incorporation of Bi atoms. We demonstrated that a kinetic model of the growth can accurately predict the Bi content by taking into account the extremely low desorption/hopping probability of Sb on the InSb surface due to its low growth temperature and weaker In-Bi bond. The model implies a Bi desorption energy barrier on the InSb surface and an activation energy for Sb to displace Bi of 1.27 eV and 0.29 eV, respectively.

Elemental characterization of freeze dried domestic animals’ milk using ion beam analysis techniques

Particle induced X-ray emission (PIXE) and particle induced γ-ray emission (PIGE) techniques were employed to perform elemental analysis in four milk samples of local domestic animals, namely sheep, caw, camel and goat. Additionally, Rutherford backscattering (RBS) spectra were acquired simultaneously with PIXE and PIGE to determine matrix elements. Milk samples were prepared in a simple dried base following freeze drying process. Optimization of PIXE/PIGE/RBS experimental conditions as well as data acquisition and analysis procedures were carefully addressed. Verification study was performed relying on the analysis of both IAEA-11 and IAEA-153 reference materials. Accuracies of ±5–10% together with relative standard deviations of less than 15% were mostly reported. Chemical element concentrations of 11 elements were determined, namely Na, Mg, P, S, Cl, K, Ca, Zn, Br, Rb and Sr. Obtained element concentration values were mostly in the range 1000–10000 μg/g for major elements and 5–100 μg/g for trace elements. No significant changes in elemental concentration differences for both trace and major elements were noticed in the four different milk samples. The contribution of the elements in these milk samples to the dietary recommended intakes (DRI) has been evaluated. Advantages of applying multiple ion beam analysis techniques have been discussed.

Differential evolution optimization of Rutherford backscattering spectra

We investigate differential evolution optimization to fit Rutherford backscattering data. The algorithm helps to find, with very high precision, the sample composition profile that best fits the experimental spectra. The capabilities of the algorithm are first demonstrated with the analysis of synthetic Rutherford backscattering spectra. The use of synthetic spectra highlights the achievable precision, through which it becomes possible to differentiate between the counting statistical uncertainty of the spectra and the fitting error. Finally, the capability of the algorithm to analyze large sets of experimental spectra is demonstrated with the analysis of the position-dependent composition of a SrxTiyOz layer on a 200 mm silicon wafer. It is shown that the counting statistical uncertainty as well as the fitting error can be determined, and the reported total analysis uncertainty must cover both.

Advanced microstructure, morphology and CO gas sensor properties of Cu/Ni bilayers at nanoscale

In this study, we investigated the morphology of synthesized Cu/Ni nanoparticles in trace of carbon sources by the co-deposition process of RF sputtering and RF-PECVD methods and localized surface plasmon resonance of CO gas sensing of Cu/Ni nanoparticles. The surface morphology was studied by analyzing 3D micrographs of atomic force microscopy using image processing techniques and fractal/multifractal analyses. The MountainsMap® Premium software with the two-way ANOVA (Variance analysis) and least-significant differences tests were used for statistical analysis. The surface nano-patterns have a local and global particular distribution. Experimental and simulated Rutherford backscattering spectra confirm the quality of nanoparticles. Then, prepared samples were exposed to CO gas flue to study their gas sensor application using the localized surface plasmon resonance method. Increasing the Ni layer over Cu one shows an interesting result in both morphology and gas sensing sides. Advanced stereometric analyses for the surface topography of thin films in conjunction with Rutherford backscattering spectrometry and Spectroscopic analysis make a unique study in the field.

A method to predict texture effect on ion beam channeling analysis of polycrystals and the application to study the mosaic spreading effect in highly oriented pyrolytic graphite

We propose a method to convert the channeling Rutherford backscattering spectrum yield map of a single crystal to a polycrystal through a matrix rotation technique. The rotation matrix is determined by the deviation of the crystal axial direction from the original z axis. The final yield map is created after averaging the rotated yields using the texture function as the weight factor. For highly oriented pyrolytic graphite (HOPG) exhibiting mosaic spread, the method leads to a Gaussian kernel averaging of the map obtained from a single crystal. The yield map of a single crystal is obtained by a simulation of ion trajectories in a potential field described by Moliere screened Coulomb potentials. Yield maps are calculated under variousσ values (standard deviations of mosaic spread). The simulated results are compared with experimental results obtained using 1.2 MeV alpha particle. σ is extracted through the best fitting, demonstrating that the method can be used to obtain texture details. The effects of mosaic spread on minimum yield χmin and the half-width at half maximum of angular scans ψ1/2 are systematically modeled and compared with previous theoretical equations. The study also shows that previous theoretical equations are valid only at small σ values. The proposed method can be applied to any type of polycrystal and is not limited to HOPG. It provides near-surface mosaic spread and crystallography information with a longitudinal depth resolution of tens of nanometers and is not influenced by grain shapes.

The study of channeling parameters of protons along axial and planar directions of Si

In this work, the channeling parameters, the ratio of channeling to random stopping power, and the mean channeling distance, of protons along the 〈100〉, 〈110〉, {100} and {110} directions of Si were studied in terms of the atomic potential of channels. The channeling parameters were deduced using the simulation of the channeling Rutherford backscattering spectra based on the exponential dechanneling function. The best simulation parameters were set using the Levenberg- Marquardt algorithm. The RBS/C spectra were taken in energy interval 1400–2200 keV, using a Si wafer. Considering the deduced parameters along the 〈100〉, 〈110〉, {100} and {110} directions in terms of the atomic potential of channels and using the data along the 〈111〉 and {111} channels reported in the literature, the channeling behavior of protons along the 〈111〉 and {111} direction was explained concerning the shallow and deep potentials. Finally, the mean channeling distance along the {111} channel was estimated.

Synthesis of bimetallic AuAg nanoparticles by sequential ion implantation for modifying surface-plasmon-resonance properties

Bimetallic AuAg (Au (80%) and Ag (20%)) nanoparticles (NPs) have been synthesized in fused quartz matrix using sequential ion implantation and post-annealing in air at 600 °C, 700 °C, 800 °C and 900 °C. X-ray diffraction (XRD) results confirm the formation of crystalline Au80Ag20 bimetallic NPs after annealing. Transmission electron microscopy (TEM) investigations have confirmed presence of spherical AuAg alloyed and few AuAg alloy core- Ag shell/satellite NPs. Rutherford backscattering spectra, along with fittings, revealed the mixing of Au and Ag atoms after annealing and movement of elements towards the surface. The peak position of the surface plasmon resonance (SPR) feature of Au has been shifted towards higher energy after sequential Ag implantation. The SPR peak position and intensity is further modified after annealing of Au80Ag20 NPs. The mechanism of modified SPR properties is mechanistically discussed by considering the diffusion, alloying, segregation and redistribution of Au/Ag in the host matrix.

A model to simulate large angle Rutherford backscattering spectra in GEANT4

A model was developed to simulate RBS spectra of H, He and Li ions based on the GEANT4 simulation toolkit. The simulation consists of tracking particles inside the medium and collecting kinetic energy and momentum direction at each step of the particle track. With this information, a backscattering spectrum is simulated based on Rutherford and non-Rutherford cross sections, detection angle and energy loss in the sample and the detector. The simulation of impinging particles is governed by GEANT4 physics processes, while the backscattered particle kinetic energy at the detector is evaluated manually. The developed GEANT4 model supports up to five layers, includes evaluation of energy loss straggling and multiple scattering induced energy straggling, evaluation of detector energy resolution of heavier ions. The RBS spectra obtained by our GEANT4 model were compared with the most widely used tools, specifically, IBA Data Furnace WinDF and SIMNRA, and showed a good agreement. The current model lacks evaluation of plural scattering, surface roughness, material porosity influence, etc., however, as it is open source, the users and developers can add the lacking functions.

Determination of the Oxygen Concentration in GDP Thin Films Using Rutherford Backscattering Spectroscopy

The oxygen concentration in the glow discharge polymer (GDP) capsule is one of the perturbations that most limit implosion quality. In order to investigate the feasibility of the Rutherford backscattering (RBS) technique for characterizing the oxygen concentration in a GDP capsule, the basic principle of RBS and the experimental conditions are introduced first. Then, the irradiation damage effect of incident ions on the GDP film is simulated numerically. The simulated results demonstrate that the GDP films will be damaged by the incident ions, and the vacancy damage dominates in irradiation modification. Finally, some GDP thin films are measured using RBS, and the oxygen concentration and its depth profile are obtained from the measured RBS spectrum. The simulated and experimental results prove that the oxygen concentration of GDP films can be measured precisely using RBS with an uncertainty of about 3.5%.

IBAT: A new ion beam batch analysis tool for thin samples

We present a new analysis tool and user interface for batch analysis of PIXE, PIGE, RBS and PESA spectra of thin samples. IBA analysis techniques are ideally suited for aerosol filter analysis, because of their high sensitivity and because the layer of aerosol material deposited on the filters is very thin. The analysis tool provides an easy interface for the MS-DOS executable of the GUPIX package, combined with newly developed software for Proton Induced Gamma Emission (PIGE), Rutherford Back Scattering (RBS) and Proton Elastic Scattering Analysis (PESA). For PIGE and PESA background subtraction techniques are applied to extract the gamma and hydrogen recoil peaks and calculate concentrations using suitable calibrations standards. For RBS a similar technique is applied to extract estimates for C, N and O. The results of this new analysis tool will be compared with results obtained from the PIXAN package used previously. The data will also be checked for internal consistencies within aerosol data sets using source apportionment techniques.

Quantitative Spectral Data Analysis Using Extreme Learning Machines Algorithm Incorporated with PCA

Extreme learning machine (ELM) is a popular randomization-based learning algorithm that provides a fast solution for many regression and classification problems. In this article, we present a method based on ELM for solving the spectral data analysis problem, which essentially is a class of inverse problems. It requires determining the structural parameters of a physical sample from the given spectroscopic curves. We proposed that the unknown target inverse function is approximated by an ELM through adding a linear neuron to correct the localized effect aroused by Gaussian basis functions. Unlike the conventional methods involving intensive numerical computations, under the new conceptual framework, the task of performing spectral data analysis becomes a learning task from data. As spectral data are typical high-dimensional data, the dimensionality reduction technique of principal component analysis (PCA) is applied to reduce the dimension of the dataset to ensure convergence. The proposed conceptual framework is illustrated using a set of simulated Rutherford backscattering spectra. The results have shown the proposed method can achieve prediction inaccuracies of less than 1%, which outperform the predictions from the multi-layer perceptron and numerical-based techniques. The presented method could be implemented as application software for real-time spectral data analysis by integrating it into a spectroscopic data collection system.

Detailed analysis of Ga-rich current pathways created in an n-Al0.7Ga0.3N layer grown on an AlN template with dense macrosteps

To clarify the behavior of the AlGaN in 20 nm wide Ga-rich current pathways in an n-AlGaN layer, which assists carrier localization in AlGaN-based light-emitting diodes, we performed a detailed analysis using an n-Al0.7Ga0.3N layer on AlN with dense macrosteps on a 1.0° miscut sapphire substrate. Energy-dispersive X-ray spectra, obtained using cross-sectional scanning transmission electron microscopy calibrated by Rutherford backscattering and cross-sectional cathodoluminescence spectra, indicated that AlN mole fraction in the Ga-rich current pathways was nearly ~2/3. This result is consistent with those of other research groups, suggesting that metastable Al2/3Ga1/3N is created in Ga-rich current pathways.

RBSandPIXEdata analysis by two dimensional correlation mapping techniques: On the effects of ion irradiation and sulfonation on poly(ether ether ketone) membranes

The present work proposes the use of two‐dimensional correlation mapping (2D‐CM) methods to analyze both particle induced X‐ray emission (PIXE) and Rutherford back scattering (RBS) spectra. RBS spectra of ion irradiated (H+and He2+) poly(ether ether ketone) (PEEK) films were analyzed by both generalized and hybrid 2D‐CM techniques to reveal the chemistry involved in different ion irradiation types. The analysis indicated different irradiation mechanisms using He2+and H+high energy ion beams and was assigned to X‐linking and Y‐linking, respectively. The effects of sulfonation on the structure of PEEK membranes were also analyzed from their RBS and PIXE spectra. The sequential order of elemental concentration change with increasing the degree of sulfonation (DS) was determined as: N→S→O→C, and the origin of Nitrogen was assigned to the casting solvent as revealed from nuclear magnetic resonance (NMR) spectra. In addition, Hetro‐2D‐CM‐PIXE‐RBS analysis indicated the presence of three RBS Sulfur signals, and were assigned to Sulfur at surface, in the middle and in depth. 2D‐CM techniques could be considered as a promising approach to enrich information obtained by ion beam analysis.

Depth Profiling of Layered Si−O−Al Thin Films with Secondary Ion Mass Spectrometry and Rutherford Backscattering Spectrometry

The results of depth profiling a four layered Si–O−Al thin film with different concentrations of elements in the layers are presented. Secondary-ion mass spectrometry (SIMS) and Rutherford backscattering (RBS) facilities are used to obtain the depth distributions of the element densities in the film. The data of analysis by the SIMS method are used as the initial concentration profiles in processing the Rutherford backscattering spectra using the SIMNRA program. As a result, a model film structure is constructed that describes the spectra of Rutherford backscattering obtained under various experimental measurement conditions, refines the results of analysis by the SIMS method and allows quantitative distributions with respect to the depth of the element concentration and the film density to be obtained.

In Situ Modification and Analysis of the Composition and Crystal Structure of a Silicon Target by Ion-Beam Methods

The method of Rutherford backscattering (RBS) with channeling is widely used in compositional analysis and structural determination. An experimental process line for in situ ion implantation and RBS spectrometry is presented, and its technical parameters are given. The parameters of a probing beam needed to reach a several-percent error in the study of distribution profiles of impurities and defects are detailed. The resolution of this method was estimated using the spectrum of alpha particles produced in the decay of 239Pu and based on the RBS spectrum from a silicon monocrystal. The implantation of Xe+ ions with an energy of 100 keV into a silicon monocrystal and the RBS analysis of targets in the channeling mode were performed without breach of vacuum conditions. The distribution profiles of implanted atoms and defects in irradiated monocrystals were examined.

Investigation of high indium-composition InGaN/GaN heterostructures on ZnO grown by metallic organic chemical vapor deposition

The optical properties and film quality for a series of high-In composition InGaN films grown on ZnO substrate by metal-organic chemical vapor deposition (MOCVD) are characterized by using high resolution X-ray diffraction (HRXRD), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Raman scattering spectroscopy (RSS). The In composition is evaluated by analyzing the RBS and PL emission spectra. The XPS measurements revealed the diffusion of Zn atoms from the substrate into InGaN films. All the analyses of experimental measurements have shown that the growth temperature played an important role in indium composition as well as of film quality. An optimum growth temperature is a necessary condition for obtaining high-quality films.

Crystal structure and composition of BAlN thin films: Effect of boron concentration in the gas flow

We have investigated the microstructure of BxAl1-xN films grown by flow-modulated epitaxy at 1010°C, with B/(B+Al) gas-flow ratios ranging from 0.06 to 0.18. The boron content obtained from X-ray diffraction (XRD) patterns ranges from x=0.02 to 0.09. On the other hand, boron content deduced from the aluminum signal in the Rutherford backscattering spectra (RBS) ranges from x=0.06 to 0.16, closely following the gas-flow ratios. Transmission electron microscopy indicates the sole presence of a wurtzite crystal structure in the BAlN films, and a tendency towards columnar growth for B/(B+Al) gas-flow ratios below 0.12. For higher ratios, the BAlN films exhibit a tendency towards twin formation and finer microstructure. Electron energy loss spectroscopy has been used to profile spatial variations in the composition of the films.The RBS data suggest that the incorporation of B is highly efficient for our growth method, while the XRD data indicate that the epitaxial growth may be limited by a solubility limit in the crystal phase at about 9%, for the range of B/(B+Al) gas-flow ratios that we have studied, which is significantly higher than previously thought.