Ion Rutherford Backscattering Research Articles

Cryogenic heavy ion RBS-ERDA depth profiling of ion implanted PET films

The analysis of thin films using heavy ions offers some specific advantages over traditional light ion beam analysis techniques. In this work, polyethylene terephthalate (PET) substrate was implanted with 150 keV Ag+-ions at low temperature at fluences of 1.00 x 1016 and 5.00 x 1016 ions/cm2. A newly constructed low temperature chamber equipped with heavy ion Rutherford Backscattering Spectrometry (HI-RBS) and Elastic Recoil Detection Analysis (HI-ERDA) detectors was used for sample characterisation, using 14 MeV 28Si4+-ions at an irradiation fluence of about 2.40 x 1013 ions/cm2. The analyses were carried out at room temperature and with the sample holder cooled to liquid nitrogen temperature. Silicon beam irradiation effects on the PET were then compared at room- and low-temperature measurements. Significant hydrogen loss of about 64 % relative to pristine PET was observed for room-temperature measurements, whereas for low-temperature analyses the hydrogen loss was about 12 %. The significant release of hydrogen atoms from the surface region of the PET was accompanied by a drastic change in the surface layer composition. For room-temperature measurements, there was surface enhancement of the carbon content by about 31 %, while for low-temperature measurements the accumulation was about 9 % compared to the nominal 45 % content in pristine PET.

Ion-Beam and X-Ray Methods of Elemental Diagnostics of Thin Film Coatings

We show how the combined use of the methods of Rutherford backscattering of ions and X-ray fluorescence analysis under conditions of total external reflection of the flow of exciting hard X-ray radiation and registration of the X-ray radiation output during ion excitation allows to effectively diagnose the elemental composition of thin-film coatings and films of dry residues of liquids. These methods and the features of their experimental application are briefly described. Examples of the complex methodological analysis of real objects are given. The possibility of increasing the efficiency of the methods of X-ray fluorescence analysis of materials due to the inclusion in the X-ray optical schemes of experimental measurements of flat X-ray waveguide resonators is indicated.

Analysis of Natural Diamonds by Rutherford Backscattering

The method of Rutherford backscattering (RBS) of 4He ions is used to detect impurities in the surface region of natural diamond crystals. In order to decrease the influence of luminescence from the surface of diamond, the recording of scattered ions is performed by an annular detector, which decreases the statistical error and improves the measurement accuracy. The limit of impurity detection is 1014 at/cm2 for light impurities and 1012 at/cm2 for heavy impurities.

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.

Ионно-пучковые и рентгеновские методы элементной диагностики тонкопленочных покрытий

Abstract We show how the combined use of the methods of Rutherford backscattering of ions and X-ray fluorescence analysis under conditions of total external reflection of the flow of exciting hard X-ray radiation and registration of the X-ray radiation output during ion excitation allows to effectively diagnose the elemental composition of thin-film coatings and films of dry residues of liquids. These methods and the features of their experimental application are briefly described. Examples of the complex methodological analysis of real objects are given. The possibility of increasing the efficiency of the methods of X-ray fluorescence analysis of materials due to the inclusion in the X-ray optical schemes of experimental measurements of flat X-ray waveguide resonators is indicated.

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.

Oxygen diffusion in TiO2 films studied by electron and ion Rutherford backscattering

The diffusivity of oxygen in thin, sputter-deposited TiO2 films, as can be used in RRAMs, is measured using electron and ion backscattering techniques. The as-grown sample consisted of two layers (Ti16O2 and Ti18O2) and was annealed between 500°C and 900°C. The depth profiles of 18O, as measured with both techniques, were similar. The extent of diffusion was much larger than expected from the literature data for O diffusion in single-crystal rutile, suggesting that defects in the sputter-deposited film play an essential role in the diffusion process.

On the manifestation of phosphorus-vacancy complexes in epitaxial Si:P films

In situ doped epitaxial Si:P films with P concentrations >1 × 1021 at./cm3 are suitable for source-drain stressors of n-FinFETs. These films combine the advantages of high conductivity derived from the high P doping with the creation of tensile strain in the Si channel. It has been suggested that the tensile strain developed in the Si:P films is due to the presence of local Si3P4 clusters, which however do not contribute to the electrical conductivity. During laser annealing, the Si3P4 clusters are expected to disperse resulting in an increased conductivity while the strain reduces slightly. However, the existence of Si3P4 is not proven. Based on first-principles simulations, we demonstrate that the formation of vacancy centered Si3P4 clusters, in the form of four P atoms bonded to a Si vacancy, is thermodynamically favorable at such high P concentrations. We suggest that during post epi-growth annealing, a fraction of the P atoms from these clusters are activated, while the remaining part goes into interstitial sites, thereby reducing strain. We corroborate our conjecture experimentally using positron annihilation spectroscopy, electron spin resonance, and Rutherford backscattering ion channeling studies.

Role of the substrate on the magnetic anisotropy of magnetite thin films grown by ion-assisted deposition

Magnetite (Fe3O4) thin films were deposited on MgO (001), SrTiO3 (001), LaAlO3 (001) single crystal substrates as well on as silicon and amorphous glass in order to study the effect of the substrate on their magnetic properties, mainly the magnetic anisotropy. We have performed a structural, morphological and compositional characterization by X-ray diffraction, atomic force microscopy and Rutherford backscattering ion channeling in oxygen resonance mode. The magnetic anisotropy has been investigated by vectorial magneto-optical Kerr effect. The results indicate that the magnetic anisotropy is especially influenced by the substrate-induced microstructure. In-plane isotropy and uniaxial anisotropy behavior have been observed on silicon and glass substrates, respectively. The transition between both behaviors depends on grain size. For LaAlO3 substrates, in which the lattice mismatch between the Fe3O4 films and the substrate is significant, a weak in-plane fourfold magnetic anisotropy is induced. However when magnetite is deposited on MgO (001) and SrTiO3 (001) substrates, a well-defined fourfold in-plane magnetic anisotropy is observed with easy axes along [100] and [010] directions. The magnetic properties on these two latter substrates are similar in terms of magnetic anisotropy and coercive fields.

Structure of Si near-surface layer after 64Zn+ ion implantation at elevated temperature

The results of studying the structure and composition of the surface layer of a Si plate after 64Zn+ ion implantation and thermal annealing in oxygen are presented. The ions are implanted into a substrate heated to a temperature of 400°C. Radiation defects and profiles of implanted Zn and oxygen diffused into the substrate are studied by means of 1.7-MeV He+-ion Rutherford backscattering spectroscopy using the channeling technique. The implanted layers are visualized using high-resolution transmission electron microscopy in combination with electron diffraction and energy dispersive microanalysis. Atomic-force microscopy is used to study the surface morphology.

Spectrometry of the Rutherford backscattering of ions and the Raman scattering of light in GaS single crystals irradiated with 140-keV H 2 + ions

The methods of the Raman scattering of light and Rutherford backscattering are used to study the degree of structural disorder in layered GaS crystals before and after irradiation with 140-keV H2+ ions. It is shown that the distribution of the crystal’s components over depth is homogeneous; for doses as high as 5 × 1015 cm−2, the stoichiometric composition of the compound’s components is retained. The experimental value of the critical dose for the beginning of amorphization amounts to about 5 × 1015 cm−2 and is in accordance with the calculated value. The results obtained by the method of the Raman scattering of light confirm conservation of crystalline structure and the start of the amorphization process.

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.

Nuclear-physical analysis of the contamination on the surface of a COMPLAST panel after 12-year exposure at the ISS

Using methods of X-ray fluorescence analysis (XRFA), the Rutherford backscattering of ions (RBS) and spectral X-ray microanalysis (SXRM) in combination with scanning electron microscopy (SEM), we study the elemental composition and structure of contaminants on the surface of a metallic panel with samples of different materials exposed to outer space for 12 years. It turns out that the main elements of the contaminants are C, O, Si, S, Ca, Fe, and Zn. Since these elements are the constituents of materials located on the panel, they are present as a result of destruction of the materials under the action of outer-space factors. X-ray phase analysis (XRPA) of the contaminants shows that carbon is present in the form of an amorphous graphite phase with a small addition of crystalline graphite, while the other components are in an amorphous state. Crystalline silicium dioxide and other silicium compounds are not found.

Ion fluence dependence of the total sputtering yield and differential angular sputtering yield of bismuth due to 50 keV argon ion irradiation

The dependences of the total sputtering yield of Bi and the differential angular distribution of these sputtered Bi atoms on the fluence of 50keV Ar+ ions at normal incidence have been experimentally measured. Polycrystalline Bi targets were used for these purposes. The collector technique and accurate current integration methods were adopted for the determination of angular distributions of sputtered Bi atoms. The ion fluence was varied from 1.9×1019 to 3.1×1020ions/cm2. The sputtered atoms were collected on high purity aluminum foils under ultra-high vacuum (∼5×10−9Torr). The collector foils were subsequently analyzed using heavy ion Rutherford backscattering spectroscopy. The shape of the angular distribution of sputtered atoms was found not to change significantly with the fluence, but the sputtering yield increased significantly from 2.2±0.2 to 9.6±0.6atoms/ion over the fluence range studied.

Ion channeling in CuInSe2 single crystals

CuInSe2 single crystals are studied by the Rutherford Backscattering of 2MeV helium ions involving axial channeling along the 〈221〉 direction of the chalcopyrite lattice. Experimental values of the critical angle and normalized minimum yield are measured and compared with theory. The concentration of point defects separately in the Cu, In, and Se sublattices, determined from the comparison of experimental and theoretical minimum yields, are estimated as 4.7×1020, 1.0×1020, and 5.7×1020cm−3, respectively.

Energy resolution measurement and application of the F series ORTEC SSB detector in TOF-ERDA spectrometry

In the Elastic Recoil Detection Analysis (ERDA) and Heavy Ion Rutherford Backscattering Spectrometry (HIRBS), silicon surface barrier (SSB) detectors as well as other types of Si charged particle detectors are conventionally used for measuring ion energy due to their simplicity and ease of use. Energy resolution of such detectors is a limiting factor for both, mass and depth resolution in the experiment. In the present work we have studied performance of the commercially available F series ORTEC SSB detector designed in particular for heavy ion spectroscopy (BF-023-300-60). Detector energy and mass resolution were measured for a wide range of ion masses (7Li, 16O, 28Si, 35Cl and 81Br) and energies (2–20MeV). Obtained results were compared with the already published data for a standard A series ORTEC SSB detector (BA-017-100-100) and gas ionization chambers. Possible application of the F series SSB detector in time-of-flight ERDA (TOF-ERDA) spectrometer was discussed.

Solid-state field-assisted silver diffusion in (TeO2)0.6(WO3)0.25(La2O3)0.05(Na2O)0.1 glass

Silver-doped layers have been produced in (TeO2)0.6(WO3)0.25(La2O3)0.05(Na2O)0.1 (TWLN) glass by solid-state field-assisted diffusion. The silver concentration profile in the glass has been determined by secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). The Matano-Boltzmann method applied to thermally activated diffusion indicates that the silver diffusion coefficient in the glass is a weak function of silver concentration. We carried out modeling of silver concentration profiles in the doped layer of the TWLN glass after solid-state field-assisted diffusion. Good agreement of the theoretical fit and experimental data suggests that the model chosen can be used to describe solid-state field-assisted diffusion of silver ions in TWLN glasses. Using RBS data, we have quantitatively estimated the surface density of silver atoms after field-assisted diffusion. Combining SIMS and RBS, we were able to assess the absolute silver concentration depth profile. Our results demonstrate that field-assisted diffusion, a simple and effective procedure for doping optical glasses, can be used to produce planar waveguide structures based on the tellurite glass studied here.

Structure and tribological characteristics of steel under melting by plasma flow and simultaneous Mo and W alloying

New findings of studies of the structural, tribological, and physicomechanical characteristics of structural steel 40Kh treated by plasma flow under melting accompanied by either tungsten or molybdenum alloying are presented. Rutherford back-scattering of ions, scanning electron microscopy (with microanalysis), X-ray fluorescent spectral analysis, X-ray phase analysis, wear-resistance tests, measurement of the coefficient of friction, and transmitting electron microscopy with diffraction are the basic research methods. It is found experimentally that a thin layer 5 μm thick saturated with nitrogen and an alloying element (Mo or W) with regularly arranged crystallites arises on the steel 40Kh surface. The crystallites in this layer have a needle- and ribbon-shaped structure. A deeper layer located about 40 μm thick consists of micro- and nanosized grains. Friction and wear studies of the plasma-flow treated (melt) samples show the steel wear resistance to increase 2–2.5 times and the coefficient of friction to decrease from 0.4–0.5 to 0.10–0.15 compared to the untreated samples.

Accurate Current Integration for Heavy Ion Rutherford Backscattering at University of North Texas

ABSTRACTAn experimental set up has been designed to suppress electron currents generated during energetic ion irradiation to obtain accurate current integration for Heavy Ion Rutherford Backscattering Spectroscopy (HIRBS) measurements of heavy element concentrations and target depth profiles. A combination of an electron trap to suppress any electrons ejected from beam collimators and slits, and a biased aluminum mesh to suppress any secondary electrons ejected from the target was used. Two samples that produce cleanly interpreted spectra have been used as targets to check the accuracy of the system for 3.0 and 4.5 MeV O+2 projectile ions. Details of the experimental set up and data are presented.

Swift heavy ion-induced interface mixing in a Si–Nb thin film system

In this work, we report the study of swift heavy ion-induced mixing at the interface of an a-Si/Nb/ a-Si (a-Si=amorphous silicon) thin film system at different fluences using two different characterization techniques: secondary ion mass spectroscopy and Rutherford backscattering spectrometry. The depth profiles of the samples of this system showed significant changes in the interface region when irradiated by 120 MeV Au ions. The fluence range was varied from 1×1013 to 1×1014 ions/cm2. Significant interface mixing has been observed in this range and was found to increase linearly with the increase in the ion fluence. Atomic force microscopy of the samples was also performed to confirm that there is no significant contribution of surface roughness. Mixing has been quantified in terms of mixing rate (k). This high energy-induced mixing effect has been explained in the framework of the thermal spike model which verifies the hypothesis of melt-phase diffusion across the interface.