Heavy Ion Rutherford Backscattering Spectrometry 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.

Heavy Ion RBS Characterization of Multilayer Coatings Deposited on Glass Through the Sol-Gel Technique

Multilayer reflecting thin films of the systems TiO2-SiO2 and ZrO2-SiO2 were deposited on glass surface using the sol-gel technique. A 12C beam was utilized in RBS analysis to investigate the inner structure of these multilayer stacks. No evidence for defects or diffusion between the layers were found. Optical Spectroscopy showed wavelength selectivity in the reflection of an 8-layer TiO2-SiO2 sample.

Heavy-ion RBS characterization of multilayer TiNx-SiO2-Si structures

Multilayer structures consisting of TiNx-SiO2-Si layers operating as MOS devices were constructed and tested for their electrical properties. RBS measurements were performed for the characterization of the structure of the devices. The results show a correlation between the structure found by RBS and the electrical performance of the devices.

L-shell X-ray production cross sections in metal oxide thin films due to 12C, 16O and 28Si ion beams at MeV SIMS energies

Successful co-implementation of different heavy ion beam nuclear analytical techniques such as heavy ion PIXE, ERDA, MeV SIMS and RBS hinges on the availability of accurate databases of fundamental ion beam-matter interaction parameters. We report on measurements carried out to determine L-shell X-ray production cross sections in 101Ru and 181Ta due to 12C, 16O and 28Si projectile ions in the 0.2 MeV/u–1.0 MeV/u energy range. Experimental data is compared to calculations by one of the most widely implemented X-ray ionisation theories in PIXE analyses – the ECPSSR theory in its modified United Atom (UA) version. Results show fairly good agreement between experiment and theory for the 181Ta target atoms, with the level of agreement improving as the Zion/Ztarget ratio decreases and as beam energy increases. For 101Ru target atoms theoretical predictions tend to underestimate experimental data and the discrepancies increase with projectile mass and decreasing energy. The contribution of projectile electron capture (EC) to the measured X-ray production cross sections is also considered in the data analysis and discussion.

Tails

Monte Carlo simulation software applied to ion beam analysis use the main scattering event (MSE) approximation. This approximation consist in generating ion trajectories in different directions, making the detection rate independent of the cross-section dependence on the scattering angle, therefore speeding up calculations by a factor 104–106. The event generated bear a probability weight proportional to the cross-section, so in the case of Rutherford backscattering spectrometry (RBS), events generated with a small scattering angle bear a very large weight, sometimes producing few events with a very large amplitude in the spectrum. They are avoided by setting a cut-off angle, but the signal they represent is in fact an actual contribution to the background signal. Here, it is shown that experimental spectra that include a significant contribution from several wide-angle scattering, such as tails or background signal in heavy ion RBS can be reproduced by a combination of two simulations: one featuring at least one wide-angle scattering, simulated accurately within the MSE approximation, and a background signal part, corresponding to trajectories featuring a series of small-angle scattering, simulated without the MSE approximation; this second simulation is achieved in a few minutes by increasing the detector size and mean free path by large factors, typically 100 each. The events included from the two parts of the simulation are discriminated by the minimum angle of the MSE.

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.

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.

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.

Heavy ion Rutherford backscattering spectrometry (HIRBS) study of barium diffusion in borosilicate glass

Diffusion of barium in borosilicate glasses containing sodium and calcium has been studied using heavy ion Rutherford backscattering spectrometry (HIRBS) using 30MeV 19F beam. A thin layer (25μg/cm2) of BaCl2 was vacuum evaporated on the polished surface of the glass samples which were then annealed at different temperatures (573–723K) and subsequently subjected to HIRBS measurements. It was observed that introduction of 10mole% of calcium in place of sodium results in increase in the activation energy of diffusion of barium by about 30%. This indicates that alkaline earth ions retard the diffusion process in borosilicate glass. The results corroborate the data obtained on diffusion of sodium by radiotracer method. The results have been explained in terms of the increasing rigidity of the glass network with introduction of alkaline earth ions.

Time-of-flight telescope for heavy-ion RBS

This paper describes a time-of-flight (TOF) spectrometer for Heavy-Ion Rutherford Backscattering Spectrometry (HI-RBS) recently installed at IMEC for thin film analysis. The TOF telescope allows the use of ion beams heavier than He, with advantages in terms of depth and mass resolution and sensitivity compared to conventional RBS based on planar Si detectors.The start timing-signal is produced by the secondary electrons emitted from a thin C foil when traversed by a backscattered ion; the electrons are deflected in an electrostatic mirror towards a Micro-channel plate (MCP) assembly which provides a fast timing response. The stop signal is obtained directly from a second MCP assembly perpendicular to the ion trajectory.The setup was tested with a variety of incident beams. An energy resolution as good as 10, 14, 17 and 25keV was achieved for 4He, 12C, 16O and 35Cl beams respectively. The associated depth resolution improves up to a factor of three, compared to conventional RBS.The different contributions to the energy resolution in the near-surface region are theoretically evaluated. The main limiting factors in the low and high energy range are the tandem effect and the telescope time resolution (550ps), respectively. In order to reduce the tandem effect, a new design of the first timing gate, with the C foil at ground potential, is currently under development.

Surface Stoichiometry and Structural Properties of Copper‐Containing Sol–Gel SiO2 Films

AbstractSummary: A study of the surface stoichiometry and structural properties of composite, copper‐containing, silica thin films (Cu:SiO2) is presented. The films are prepared on glass substrates by a sol–gel route. The coatings deposited by a dipping process are thermally treated under oxidative and subsequently reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure, the nanoparticle formation, the copper diffusion, and the chemical composition of the surface are investigated using X‐ray diffraction (XRD), UV‐vis spectroscopy, heavy ion rutherford backscattering spectroscopy (HIRBS), and X‐ray photoelectron spectroscopy (XPS) as analytical methods.HIRBS spectrum, showing the Cu distribution of samples studied: a) as prepared, b) after heating under oxidative, and c) after heating under reductive conditions, using 12C3+ ions at 10 MeV.imageHIRBS spectrum, showing the Cu distribution of samples studied: a) as prepared, b) after heating under oxidative, and c) after heating under reductive conditions, using 12C3+ ions at 10 MeV.

Sb diffusion in α-Fe

The effect of the magnetic ordering on the diffusion of Sb in α-Fe was investigated. Measurements were made in an extended temperature range: (673–1073 K), using the ion beam techniques Rutherford backscattering spectrometry (RBS) and heavy ion RBS (HIRBS) in superposed ranges of temperature. By expanding the temperature range with respect to the previous works, the Arrhenius plot shows the variation of the slope at the Curie temperature and a soft-up curvature in the ferromagnetic region. The curvature observed is well fitted by the model developed by Ruch et al. The parameter that takes into account the influence of the magnetic order in the vacancy mobility during the Sb diffusion process is quite similar to that observed in Fe self-diffusion; then, no magnetic interaction between the impurity and the matrix is postulated.

NRBS, RBS, TEM and SAED characterisation of sol–gel PZT films

TEM-SAED investigations were performed on PZT films, to elucidate the role of pyrolysis conditions on orientation selection. For short pyrolysis, occurrence of the metastable fluorite and the interfacial PtxPb template layer are the factors inducing the (111) PZT orientation. For advanced pyrolysis, the TiO2 interfacial layer could be responsible for (100) PZT strong orientation. To further investigate the stoichiometry of PZT and interfacial layers, we performed heavy ion RBS and NRBS measurements. Only a substoichiometric TiO2−x layer is found for the short pyrolized film whereas two Ti and O rich layers were observed for advanced pyrolysis. The thicker oxygen rich TiO2−x bottom layer, observed by TEM and NRBS analysis, could lead to 〈100〉 texture, observed for oxidizing conditions at the interface during pyrolysis.

Study of cesium diffusion in borosilicate glass by heavy ion Rutherford backscattering spectrometry

Abstract Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering spectrometry (HIRBS) technique using 30 MeV 19F beam. Analysis of glass samples annealed at different temperatures for 12 h duration has been used to determine the activation energy of diffusion of cesium in borosilicate glass, which is considered as one of the suitable matrices for vitrification of the high level radioactive waste. Diffusion coefficients show Arrhenius behaviour in the temperature range 473–673 K. The activation energy for diffusion is found to be 22.2 ± 3.6 kJ/mol.

Diffusion of Ta in α-Ti

The diffusion of Ta in the hcp (α) phase of high-purity Ti (99.99%) was studied at different temperatures from 911 K up to 1123 K. The Rutherford Backscattering Spectrometry (RBS) and Heavy Ion RBS (HIRBS) techniques were used to obtain the penetration profiles. The evolution of the diffusion coefficient, D, as a function of temperature follows prediction of the Arrhenius law. The activation energy of the diffusion process is (318±7)kJ/mol, similar to that corresponding to self-diffusion in α-Ti. On the other hand, the measured values of D are systematically lower than those corresponding to self-diffusion by a factor of approximately 5. This reduction could be explained by taking into account the mass difference between Ta and Ti. An increase of the diffusion coefficient was measured when the diffusion proceeds on a less pure Ti (99.9%) matrix. This increment is higher at lower temperatures.

RBS and HIRBS studies of nanostructured AgSiO 2 sol–gel thin coatings

In the present work, composite AgSiO 2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol–gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by atomic force microscopy and Rutherford backscattering spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4 He + ions were used for all samples, and low energy 16 O and 12 C ions in selected ones (heavy ion RBS, HIRBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia coli is examined by antibacterial drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol–gel thin coatings.

Interfacial Diffusion Studies of Hf and Zr into Si from Thermally Annealed Hf and Zr Silicates

AbstractHf and Zr incorporation from thermally annealed high-κ gate dielectric thin films (4-5 nm) candidates HfSixOy and ZrSixOy into Si are presented. The dielectric films were subjected either to rapid thermal annealing (RTA) or standard furnace annealing in an N2 atmosphere. After annealing, the films were removed by chemical etching prior to depth profiling using both time of flight secondary ion mass spectroscopy (ToF-SIMS), and Heavy Ion Rutherford Backscattering Spectrometry (HI-RBS) combined with UV-ozone oxidation/etching cycles. As-deposited and annealed films were studied using monochromatic X-ray Photoelectron Spectroscopy (XPS), and high resolution TEM. A Zr incorporation depth after annealing of up to 20 nm into the Si substrate was observed. Depth profiling shows that, although most of the remnant Zr after annealing/etching is located at or near the surface of the Si substrate, incorporation into the substrate is also present. No significant Hf diffusion into Si was observed for either RTP or furnace-annealed films

Diffusion of tin in α-iron

The effect of the magnetic ordering on the diffusion of Sn was investigated; for this purpose, the measurements were made in an extended temperature range (1163–673 K), using several techniques like serial sectioning, heavy ion Rutherford backscattering spectrometry (HIRBS) and Rutherford backscattering spectrometry (RBS) in superposed ranges of temperature. By spanning the temperature range with respect to the previous works, the Arrhenius plot was extended over 10 decades; then the variation of the slope at the Curie temperature and a soft-up curvature in the ferromagnetic region is now clear. The curvature observed is well fitted by the model developed by Ruch et al. ( J. Phys. Chem. Solids, 1976, 37, 649). The parameter that takes into account the influence of the magnetic order in the vacancy mobility during the Sn diffusion process is quite similar to that observed in Fe self-diffusion; then, no magnetic interaction between the impurity and the matrix is postulated.

Comparative concentration analysis of Cr and Co in FeSi 2 films performed by ERDA and RBS

Thin films of β-FeSi 2 doped by Co or Cr were grown on Si substrates by molecular beam epitaxy (MBE) using three separately controlled evaporation sources. The dopant concentration was measured concurrently by heavy-ion ERDA with 129Xe ions of 140–250 MeV, by heavy-ion RBS with 15 MeV 14N and by standard RBS with 1.4 MeV 4He ions. Among these techniques, the TOF–ERDA was most powerful in providing a high mass resolution and a low detection limit for Co and Cr (≈0.1 at.%) . Because of the complete overlap of the dopant signals with the Fe signal the standard RBS spectra were evaluated by relying on the differences between the scattering cross-sections from the dopant atoms and Fe. This approach proved to be applicable as far as the dopants had a constant depth profile with sufficiently high concentration. For Cr concentrations exceeding the miscibility limit the RBS results deviate significantly from those of ERDA due to increasing dopant depth inhomogeneities.

Lead diffusion in α-Zr

Pb diffusion in α-Zr matrix between 823 and 1123 K was measured using heavy ion Rutherford backscattering spectrometry (HIRBS) technique. A deviation from the Arrhenius law was observed, with two different regions. At low temperatures the activation energy Q is close to the expected value for a substitutional diffuser but the pre-exponential factor D0 is higher than expected. Close to the phase transition temperature the opposite occurs, with a low Q value. This behavior is similar to the one observed for Hf and self-diffusion in α-Zr.