non-Rutherford Elastic Backscattering Research Articles

Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

The atomic composition with less than 1–2atom% uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1MeV He+ analyzing ion beam and non-Rutherford elastic backscattering experiments with 2.53MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26eV to 4.62eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

International Atomic Energy Agency intercomparison of ion beam analysis software

Ion beam analysis (IBA) includes a group of techniques for the determination of elemental concentration depth profiles of thin film materials. Often the final results rely on simulations, fits and calculations, made by dedicated codes written for specific techniques. Here we evaluate numerical codes dedicated to the analysis of Rutherford backscattering spectrometry, non-Rutherford elastic backscattering spectrometry, elastic recoil detection analysis and non-resonant nuclear reaction analysis data. Several software packages have been presented and made available to the community. New codes regularly appear, and old codes continue to be used and occasionally updated and expanded. However, those codes have to date not been validated, or even compared to each other. Consequently, IBA practitioners use codes whose validity, correctness and accuracy have never been validated beyond the authors’ efforts. In this work, we present the results of an IBA software intercomparison exercise, where seven different packages participated. These were DEPTH, GISA, DataFurnace (NDF), RBX, RUMP, SIMNRA (all analytical codes) and MCERD (a Monte Carlo code). In a first step, a series of simulations were defined, testing different capabilities of the codes, for fixed conditions. In a second step, a set of real experimental data were analysed. The main conclusion is that the codes perform well within the limits of their design, and that the largest differences in the results obtained are due to differences in the fundamental databases used (stopping power and scattering cross section). In particular, spectra can be calculated including Rutherford cross sections with screening, energy resolution convolutions including energy straggling, and pileup effects, with agreement between the codes available at the 0.1% level. This same agreement is also available for the non-RBS techniques. This agreement is not limited to calculation of spectra from particular structures with predetermined parameters, but also extends to extracting information from real data. In particular, we have shown data from an Sb implanted sample where the Sb fluence was certified with an uncertainty of 0.6%. For this sample, and using SRIM03 stopping powers for 1.5MeV 4He in Si, the codes were able to extract the Sb fluence with an average 0.18% deviation from the certified value and a 0.11% agreement between the codes. Thus IBA is a suitable technique for accurate analysis where traceability is critical. These results confirm that available IBA software packages are, within their design limitations, consistent and reliable. The protocol established may be readily applied to validate future IBA software as well.

Investigation of light elements in nitrided steel using elastic backscattering analysis

This work describes the ability of ion beam analysis techniques IBA to simultaneously determine the concentration and the possible depth profile of some light elements, such as carbon, oxygen and nitrogen, in matrices of high atomic number Z, such as stainless steel materials. In fact, the nitriding process of some materials has the potential to improve their tribological and mechanical properties and to offer various advantages as compared with other methods used in the modification of surfaces. Gas and Plasma nitriding were applied to certain types of steel, such as AISI-304 and H-13 which are commonly used in the industry, in order to improve their hardness and their surface corrosion resistance. The improvement was correlated with the depth profile of N and the consequent structure variations. More specifically, non-Rutherford elastic backscattering (alpha, alpha) at 5MeV was performed on different samples, before and after nitriding, in order to determine the stoichiometry and the thickness of the newly formed surface nitrided layers.

Ion beam analysis of aluminium in thin layers

This work quantifies aluminium in thin surface and near surface layers. In one example, the layer overlies a thin gallium nitride layer on an aluminium oxide substrate and in a second example the aluminium exists just below the surface of an indium arsenide substrate. The technique of non-Rutherford elastic backscattering of protons was used for the samples where aluminum in the layer of interest needed to be resolved from aluminium in the sapphire substrate and the results were corroborated at the Technische Universität München using heavy ion elastic recoil detection analysis. In the second example, where it was unnecessary to isolate the signal of aluminium in the layer of interest (as the substrate contained no aluminium), then the 27 Al(d,p 01) 28 Al nuclear reaction was used. The elastic proton scattering cross section of aluminum was found to vary very rapidly over the energy range of interest.

Helium desorption from cavities induced by high energy 3He and 4He implantation in silicon

A detailed study has been made of helium release from silicon wafers implanted with MeV helium ions at fluences of 5×10 16 cm −2 and 10 17 cm −2. Thermal desorption spectrometry (TDS), neutron depth profiling (NDP), non-Rutherford elastic backscattering (NREBS) and nuclear reaction analysis (NRA) have been employed to measure the helium content and release rate during isothermal annealing at annealing temperatures of 800 and 1000°C. TDS has also been used for isochronal annealing. Transmission electron microscopy (TEM) is used to monitor changes in morphology in the formed bubble layer. The helium release results can be modeled rather well when it is assumed that the helium initially is present in overpressurized bubbles. The present study reveals a single activation energy for helium release of 1.83 (0.05) eV.

Cavities and dislocations induced in silicon by MeV He implantation

We implanted n-type silicon with 1.6 MeV helium at fluences ranging from 1×1016 to 1×1017 He/cm2 while keeping a constant dose rate. These samples were then subjected to 800 °C annealing for 30 min. The results obtained by means of cross-sectional transmission electron microscopy indicate that the density of cavities is fluence dependent with homogeneous distribution of cavity sizes when fluences of 5×1016 and 1017 He/cm2 are used. The threshold fluence required to form cavities is found to be between 1 and 2×1016 He/cm2. For the 2×1016 He/cm2 dose, we observed loop punching induced by a concerted action of overpressurized bubbles, whereas He implants at doses of 5×1016 and 1×1017/cm2 lead to the formation of {311} defects. At the same time, non Rutherford elastic backscattering (NREBS) experiments using 2.5 MeV H+ provide the fraction of helium remaining in cavities after different annealing times at 800 °C. The NREBS data show a fast He release process for short annealing times (<2000 s). Then, the He amount decreases slowly and after 30 000 s about 40% of the helium still remain in cavities. Finally, an additional implantation with 50 keV He at 5×1016 He/cm2 shows the difference in cavity size distribution between MeV and keV implantation.

(p,p) non-Rutherford backscattering analysis of silicon carbide

In this paper, (p,p) non-Rutherford elastic backscattering (NBS) measurements with 1.6 MeV proton beams have been used to determine the areal density and C/Si stoichiometric ratio in 300–1000 nm SiC x (H y ) films deposited on silicon substrates by Chemical Vapour Deposition (CVD) using two different gas sources, methane (CH 4) and ethylene (C 2H 4). At the same time, oxygen is also found in some of these samples. The results show that (p,p) NBS can be used to determine the areal density and C/Si ratio with a reasonable accuracy, especially when samples are thick or the terminal energy of the accelerator is low for analysis using a helium beam.

96/03789 Fly ash as an additive for concrete

A detailed study has been made of helium release from silicon wafers implanted with MeV helium ions at fluences of 5×1016 cm−2 and 1017 cm−2. Thermal desorption spectrometry (TDS), neutron depth profiling (NDP), non-Rutherford elastic backscattering (NREBS) and nuclear reaction analysis (NRA) have been employed to measure the helium content and release rate during isothermal annealing at annealing temperatures of 800 and 1000°C. TDS has also been used for isochronal annealing. Transmission electron microscopy (TEM) is used to monitor changes in morphology in the formed bubble layer. The helium release results can be modeled rather well when it is assumed that the helium initially is present in overpressurized bubbles. The present study reveals a single activation energy for helium release of 1.83 (0.05) eV.

96/03806 New controlling method for product distribution in Fischer-Tropsch synthesis reactions

A detailed study has been made of helium release from silicon wafers implanted with MeV helium ions at fluences of 5×1016 cm−2 and 1017 cm−2. Thermal desorption spectrometry (TDS), neutron depth profiling (NDP), non-Rutherford elastic backscattering (NREBS) and nuclear reaction analysis (NRA) have been employed to measure the helium content and release rate during isothermal annealing at annealing temperatures of 800 and 1000°C. TDS has also been used for isochronal annealing. Transmission electron microscopy (TEM) is used to monitor changes in morphology in the formed bubble layer. The helium release results can be modeled rather well when it is assumed that the helium initially is present in overpressurized bubbles. The present study reveals a single activation energy for helium release of 1.83 (0.05) eV.

Scanning mu-analysis of SiCSi 3N 4 material by proton non-Rutherford elastic backscattering

By the use of a 3 MeV proton mubeam we succeeded in studying SiCSi 3N 4 composite ceramics quantitatively. Proton backscattering in the MeV non-Rutherford energy region is more sensitive to detecting low-Z elements, such as C, N and O, than other ion beam methods when a heavier element is present in the matrix. The mubeam analysis was performed by scanning an inclined cross section of the sample for improving the depth resolution. The results confirm that a SiCSi 3N 4 composite layer can be formed on the presintered SiC substrate under the condition of an isostatic pressure of 200 MPa in N 2 atmosphere at 1850°C. About 60% of the SiC was transformed into Si 3N 4 in a surface layer of over 10 μm, when the reaction lasted one hour. The uncertainty in the concentration is not larger than ±10% in directions parallel to the target surface. The maps of nitrogen and carbon, in three dimensions, are also given in the interface region.

The activities with the Shanghai nuclear microprobe

The Shanghai nuclear microprobe features long focus quadrupole lenses, a multidetector system for complex measurements, fast random scan and TQSA data acquisition and reduction. Since its establishment in 1990, it has been widely used in the fields of biology, mineralogy and metallurgy. This paper is confined to the description of some distinct examples of its applications. They are the analysis of mineral grains embedded in manganese sulphide ores, the distinction of coexistence of gold in sulphide deposits, the micron-scale investigation of marine ores, the influence of impure elements on metallurgical products and the non-Rutherford elastic backscattering analysis of C and N in composite Si 3N 4 /SiC interface.

Non-Rutherford elastic backscattering for light element cross section enhancement

It has been shown that higher helium ion energies than required for Rutherford backscattering spectrometry (RBS) may for the light elements C, N and O produce enhancement of the elastic scattering cross section through nuclear interaction. A search has been conducted for bombarding ion energies in the range of 4.2–7.2 MeV that will produce a smoothly varying cross section to permit profiling of these elements. The special requirements for the standard samples needed to quantify the ratio of the nuclear elastic cross section to that of the electrostatic cross section (ratio of Rutherford) are described and appropriate bombarding ton energies identified. This elastic backscattering spectrometry (EBS) technique has proved to be suitable for profiling C, N and O simultaneously over a reasonable depth range while maintaining Rutherford scattering conditions for most heavier elements, thus permitting the profiling of these light elements in the presence of heavier elements.