Rutherford Backscattering Spectrometry Techniques Research Articles

Structure analysis of the Si()--Sb surface by means of CAICISS combined with LEED–AES–RBS techniques

Abstract The composition and atomic arrangement of the Si(1 1 1)- 3 × 3 -Sb surface have been studied by means of co-axial impact collision ion scattering spectroscopy combined with low energy electron diffraction, Auger electron spectroscopy and Rutherford backscattering spectrometry techniques. It is found that the Sb/Si(1 1 1) surface forms the 3 × 3 structure at a coverage of 0.90 ML, which is determined by RBS. The azimuthal angle scan is also found to show prominent focussing peaks at ±12° around the (1 1 2) planes at a polar angle of 13°. It is determined from the azimuthal angle scan that the Si(1 1 1)- 3 × 3 -Sb surface forms the trimer centered at the T4 site and the spacing of Sb–Sb in the trimer is 2.8±0.05 A.

Study of the contaminant transport into granite microfractures using nuclear ion beam techniques

Hydrated bentonite is a very plastic material and it is expected to enter in the rock microfractures at the granite/bentonite boundary of a deep geological high-level waste repository. This process is enhanced by the high swelling pressure of the clay. Since bentonite has a very good sorption capability for many radionuclides, the displacement of the clay might lead to a “clay-mediated” contaminant transport into the rock. The aim of this work is to study the contaminant transport into granite microfractures using nuclear ion beam techniques, and to determine to what extent the clay can favour it. To do so, bentonite previously doped with uranium, cesium and europium was put in contact with the surface of granite sheets. Granite sheets contacted with non-doped bentonite and with radionuclide solutions were also prepared as references. This allowed analysing the differences in the diffusion behaviour of the three systems: clay, radionuclides and clay plus radionuclides. A combination of Rutherford backscattering spectrometry (RBS) and other nuclear ion-beam techniques such as particle-induced X-ray emission (PIXE) and microPIXE was used to study the depth and lateral distribution of clay and contaminants inside granite. It was also tried to evaluate not only the diffusion depth and diffusion coefficients but also the different areas of the granite where the diffusants have a preferential access.

Diffusion of Sn in different purity α-Ti

The diffusion of Sn in the hcp (α) phase of high purity (99.99%) and pure (99.9%) Ti was studied at different temperatures from 873 up to 1100 K. The Rutherford Backscattering Spectrometry (RBS) technique was used to obtain the penetration profiles. The evolution of the diffusion coefficient, D, as a function of temperature follows the prediction of the Arrhenius law. No significant difference between both kinds of Ti samples was observed. Normal diffusion parameters, Q and D 0, close to the self-diffusion ones were obtained.

An experimental method for precise measurements of straggling in energy loss of 1H and 2H ions in composite materials: Application to polymer foils

A new investigation on an experimental procedure to perform precise measurements of straggling in energy loss in polymer foils has been done. The details of the experimental procedures related to the combination of Rutherford backscattering spectrometry and transmission techniques are described and discussed. As an example, energy loss and straggling measurements in the energy range of 1000–3700 keV for protons and deuterons in thin films of Mylar, Makrofol and LR-115 have been performed and are in good agreement with the theoretical predictions of Bohr; while a small discrepancy in regard to Bethe–Livingston theory was observed. The comparisons were made using Bragg’s rule over the investigated energy range.

Raman scattering, photoluminescence and spectroscopic ellipsometry studies on polycrystalline Cd0.96Zn0.04Te thin films

Cd0.96Zn0.04Te thin films are deposited onto well-cleaned glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. Rutherford backscattering spectrometry and X-ray diffraction techniques are used to determine the thickness, composition and crystalline structure and grain size of the films, respectively. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by scanning electron microscopy and atomic force microscopy. The rms roughness of the as-deposited films is 3.7 nm. The Raman spectra of the films show longitudinal- and transverse-optical (LO, TO) modes, which arise from CdTe- and ZnTe-like vibrations. The photoluminescence spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and deeper impurity levels. The pseudodielectric-function spectra, ε(E)=ε1(E)+iε2(E), of the films are measured by spectroscopic ellipsometry at room temperature. The measured dielectric function spectra reveal distinct structures at energies of the E1, E1+Δ1 and E2 critical points.

The influence of oxygen in the photoexpansion of GaGeS glasses

Irreversible photoexpansion and photobleaching effect has been observed in amorphous Ga10Ge25S65 glass when its surface was exposed to light with energy greater than the band gap, 3.52eV. The magnitude of the expansion of GaGeS glasses depends on the exposure conditions. Extended X-ray absorption fine structure (EXAFS) spectroscopy and Rutherford backscattering spectrometry (RBS) have been used to identify the chemical nature of the glass samples before and after illumination. The quantitative analysis of the EXAFS data leads to a two-shell model of 0.5 oxygen atoms at 2.01Å and 3.6 sulfur atoms at a 2.20Å. RBS technique demonstrated that chemical composition of the glass surface after irradiation is oxygen rich. The existence of GeO bonds in the glass after illumination was also confirmed by infrared measurements.

Characterization of Vacuum Evaporated Polycrystalline Cd0.96Zn0.04Te Thin Films by XRD, Raman Scattering and Spectroscopic Ellipsometry

Cd 0.96 Zn 0.04 Te thin films are deposited onto well cleaned glass substrates (Corning 7059) kept at room temperature by vacuum evaporation and the films are annealed at 423 K. Rutherford Backscattering Spectrometry and X-ray diffraction techniques are used to determine the thickness, composition and crystalline structure and grain size of the films respectively. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by Atomic Force Microscopy. The rms roughness of the as-deposited films is 3.7 nm and on annealing the films at 423K, the rms roughness value decreases to 3.4 nm. The Raman spectra of the Cd 0.96 Zn 0.04 Te films are recorded at room temperature to study lattice vibrations and their interactions with other excitations. The intensity of the peak increases and the FWHM decreases on annealing the films. The pseudodielectric-function spectra, e(E) = e 1 (E) + i e 2 (E), of polycrystalline Cd 0.96 Zn 0.04 Te thin films in the 1.3 - 5.5eV photon energy range at room temperature are measured by spectroscopic ellipsometry. The measured dielectric function spectra reveal distinct structures at energies of the E 1 , E 1 +Δ 1 and E 2 critical points are due to interband transitions.

Platinum contamination issues in ferroelectric memories

The contamination risk of processing with platinum electrodes on device performance in ferroelectric memories is assessed in this work. Details of platinum diffusion to the active regions at annealing temperatures of 800 °C are investigated by secondary ion mass spectroscopy, deep level transient spectroscopy, and Rutherford backscattering spectrometry techniques. Cross sectional transmission electron microscopy and local elemental analysis by energy dispersive x-ray spectroscopy were used to examine the precipitation of Pt in defect free silicon as an eventual cause of gate oxide degradation. The impact of platinum contamination on device performance is evaluated under the typical ferroelectric memory processing conditions. Results from leakage current and charge to breakdown measurements of intentionally contaminated diode and metal–oxide–semiconductor (MOS) structures, respectively, are presented. The results show that the degradation depends strongly on device design and configuration. A phosphorus doped polysilicon plug, which has the function of connecting the select transistor to the capacitor module, provides effective gettering regions and prevents the diffusion of Pt atoms to the active regions. Under typical processing conditions, no evident Pt precipitates were observed and up to a concentration level of 4×1014 atoms/cm2, the leakage current of intentionally contaminated diodes does not increase, if the contamination occurs after front-end phosphorus doped poly-Si processing. Results from constant current charge to breakdown show a small number of breakdown events due to redeposition of Pt at the periphery of the MOS structure. The risk of processing with Pt electrodes in ferroelectric memories requires great care. Precautions like sealing the back surface and incorporating phosphorus doped polysilicon as the plug material are necessary to avoid the detrimental effects of Pt.

Differential scattering cross-sections, inelastic energy losses and ion fractions in backscattering of keV He + ions from monolayer metal adsorbates on solid surfaces measured by means of CAICISS

Energy spectra of He atoms and He + ions backscattered at an angle of ∼180° by monolayer metal adsorbates (Ag, Sn, Sb, Pb and Bi) on the Si(1 1 1)- 3 × 3 surfaces and monolayer Si atoms on the graphite surface have been measured by means of the coaxial impact collision ion scattering spectroscopy technique combined with low energy electron diffraction, Auger electron spectroscopy and Rutherford backscattering spectrometry techniques in the energy range from 0.5 to 3.0 keV. It is found from their data analysis that the ratios of the experimental scattering cross-section to the magic formula of the Thomas–Fermi cross-section for different adsorbates deviate from unity: for instance 1.2 for Si, 0.8 for Ag, 1.5 for Sn, 1.2 for Sb, 1.2 for Pb and 1.6 for Bi. It is also found that the average inelastic energy loss for Si increases monotonically with increasing the incident energy, while those for the other adsorbates increase stepwisely at around 1.0 keV and thereafter gradually. Moreover, it is found that the stopping cross-sections at 2 keV and at zero impact parameter obtained in the present study are by an order of magnitude smaller than, but, in their functional dependence on Z 2, very similar to the empirical data of electronic stopping cross-sections by Ziegler. Finally, it is found that the ion fractions for Sn, Sb, Pb and Bi show oscillatory variations with the inverse velocity of primary ions which are explained in terms of the quasi-resonant charge exchange between the He 1s state and the 4d states or 5d states of the adsorbate atoms. On the other hand, it is also found that the ion fraction for Ag decreases very gradually from 1/3 and those for Si are less than 0.05 in the energy range below 3 keV. The latter two results on the inelastic energy losses and the ion fractions are discussed in terms of promotion of the quasi-molecular orbitals and charge exchange between the quasi-molecular orbitals formed during the close collisions of He and adsorbates.

Characterization by RBS of hyper-thin SiO 2 layers on various polymers

In order to investigate the growth mode of plasma-enhanced chemical vapor deposited (PECVD) SiO 2 gas barrier layers on various polymers (namely polyimide, PI; polyethyleneterephthalate, PET; polycarbonate, PC) we use Rutherford backscattering spectroscopy (RBS) in two different ion beam modification (IBM) geometries, with 1 and 1.5 MeV α particles (He 2+ ions). In the case of Kapton ® PI, a polymer which is damaged very little by the incident ion beam, we have followed the evolution of the surface concentration of silicon atoms versus PECVD growth duration: the relationship was found to be perfectly linear over a film thickness range 5⩽ d⩽500 Å. Using grazing incidence, we found a 7 nm thick “interphase” region between the SiO 2 coating and the substrate. However, for the case of the two other polymers (PET and PC), major artifacts were noted during RBS measurements, even under very mild beam conditions (1 nA, 8.0×10 12 ions/cm 2), because of the creation of abundant volatile molecular fragments by the incident particles below the surface of the organic substrate. Scanning electron micrographs confirm the damage caused by these volatile species, as they escape through the sample surface; this greatly limits the use of the RBS technique for most polymers, including PET and PC.

Elaboration of thin chromium silicide layers on P + implanted silicon

The aim of the present work is to investigate the mechanism of growth of chromium silicides versus several parameters. The samples are constituted of a thin chromium layer (≈80 nm) which is deposited under vacuum by electron beam evaporation/condensation onto P + implanted Si(1 0 0) and Si(1 1 1) substrates. Phosphorus ion implantation, with a dose of 5×10 14 or 5×10 15 P + cm −2, is performed at an energy of 40 keV. The samples are thermally annealed at 723–823 K (450–550°C) for various periods of time. The analysis is carried out by means of X-ray diffraction and H + Rutherford backscattering spectrometry (RBS) techniques. The RUMP 3.30 software is used to simulate RBS spectra. It is shown that, after annealing treatment, the CrSi 2 silicide is formed at Cr/Si(1 0 0) and Cr/Si(1 1 1) interfaces. For one temperature and time of annealing, the thickness of the chromium disilicide is lower for the high phosphorus dose (i.e., 5×10 15 P + cm −2) than for the low dose (i.e., 5×10 14P + cm −2). In other words, the presence of phosphorus in silicon substrates delays the formation of the CrSi 2 phase but does not inhibit it. Finally, it is established that the growth of CrSi 2 compound is more rapid on silicon substrates with 〈1 1 1〉 orientation than on the 〈1 0 0〉 orientation, which is not in agreement with the non-implanted specimens case.

Compositional characterisation of Zn-diffused lithium niobate waveguides

Rutherford backscattering (RBS) and secondary-ion mass spectrometry techniques have been used to investigate the two-step process involved during waveguide fabrication in LiNbO3 using Zn-vapour diffusion. Compositional analysis (O, Nb, Li and Zn) in the two steps has been characterised. RBS analysis reveals that the first step, involving a heating of the substrate under a metallic Zn atmosphere, gives rise to a partial exchange between the Nb and Li ions from the crystals and the Zn from the vapour source. The second treatment at higher temperature in an open atmosphere diffuses the Zn deeper into the substrate, thus forming an optical waveguide, while the Nb and Li ions recover their bulk values.

Damage profiles and damage annealing behavior in Al 0.168Ga 0.348In 0.484P/GaAs implanted with 200 keV Zn + ions

Damage profiles and the associated annealing behavior in Al 0.168Ga 0.348In 0.484P/GaAs samples implanted with 200 keV Zn + ions were investigated by using Rutherford backscattering spectrometry and channeling (RBS/C) technique. A computer code was used to extract quantitative damage profiles from the RBS/C spectra. The measured damage profiles are compared with those obtained from TRIM98 computer simulation code, and a good agreement between the measurements and the TRIM98 simulations was observed. The annealing behavior of the damage induced in the AlGaInP/GaAs samples was studied and compared with that induced in GaP bulk crystal substrates under the same implantation and annealing conditions. The result shows that the structure of the radiation damage induced in the quaternary III–V compound, AlGaInP, is more complicated than that in the binary III–V compound, GaP.

Defect formation and annealing behavior of Si implanted by high-energy 166Er ions

Si crystals were implanted at room temperature with 2.0 MeV 166 Er + ion doses of 5×10 12, 1×10 14, 5×10 14, 1×10 15 and 2.5×10 15 ions/ cm 2 . Conventional furnace thermal annealings were carried out in the temperature range from 600°C to 1150°C. The radiation damage and annealing behavior were investigated using the Rutherford backscattering spectrometry and channeling (RBS/C) technique. Doses above 5×10 14 ions/ cm 2 were found to produce amorphous layers. The experimental results show that the annealing behavior of 2.0 MeV Er + implanted into silicon is strongly influenced by the implantation dose and annealing temperature. For the samples with dose of 5×10 14 ions/ cm 2 and more, an abnormal annealing behavior was found and a qualitative explanation has been given. For the sample implanted with dose of 2.5×10 15 ions/ cm 2 , a substantial Er outdiffusion has been investigated. Er outdiffusion increases with annealing temperature, Er depth distribution changes from an initially unimodal Gaussian form to a bimodal distribution with a build up of Er concentration near the surface.

Study of tasin diffusion barrier

Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced high-density memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in 18O2 at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. 18O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV of the nuclear reaction 18O(p,α)15N.

Structural and optical properties of CdS thin films

CdS thin films are deposited onto glass substrates by vacuum evaporation at 373 K and the films are annealed at different temperatures. Rutherford backscattering spectrometry (RBS) and X-ray diffraction techniques are used to determine the thickness, composition, crystalline structure and grain size of the films. The films show a predominant hexagonal phase with small crystallites. The optical band gap of the films are estimated using the optical transmittance measurements. A decrease in the band gap is observed for the annealed films. The Raman peak position of the CdS A 1 (LO) mode did not change much whereas, the full width at half maximum (FWHM) is found to decrease with annealing.

Stress origin and relaxation in epitaxial AlN thin films on SiC

AbstractWe have investigated the epitaxy, surfaces, interfaces, and defects in AlN thin films grown on SiC by pulsed laser deposition. The stress origin, evolution, and relaxation in these films is reported. The crystalline structure and surface morphology of the epitaxially grown AlN thin films on SiC (0001) substrates have been studied using x-ray diffraction (θ–2θ, ω, and Ψ scans) and atomic force microscopy, respectively. The defect analysis has been carried out by using Rutherford backscattering spectrometry and ion channeling technique. The films were grown at various substrate temperatures ranging from room temperature to 1100 °C. X-ray diffraction measurements show highly oriented AlN films when grown at temperatures of 750- 800 °C, and single crystals above 800 °C. The films grown in the temperature range of 950 °C to 1000 °C have been found to be highly strained, whereas the films grown above 1000 °C were found to be cracked along the crystallographic axes. The results of stress as a function of growth temperature, thermal mismatch, growth mode, and buffer layer thickness will be presented, and the implications of these results for wide band gap power electronics will be discussed.

2.0-MeV Er+ implanted in silicon: depth distribution, damage profile and annealing behaviour

Si crystals were implanted with 2.0- MeV Er+ at the doses of 5×1012 ions/cm2, 1×1014 ions/cm2, 5×1014ions/cm2, 1×1015 ions/cm2 and 2.5×1015 ions/cm2. Conventional furnace thermal annealing was carried out in the temperature range from 600 °C to 1150 °C. The depth distribution of Er, associated damage profiles and annealing behavioar were investigated using the Rutherford backscattering spectrometry and channelling (RBS/C) technique. A proper convolution program was used to extract the distribution of Er from the experimental RBS spectrum. The obtained distribution parameters, projected range Rp, projected range straggling ΔRp and skewness SK were compared with those of TRIM96 calculation.The experimental Rp and SK values agree well with the simulated values, while the experimental ΔRp is larger than TRIM 96 simulated value by a factor of 18%. The damage profile of silicon crystal induced by 2.0-MeV Er+ at a dose of 1×1014 ions/cm2 was extracted using the multiple-scattering dechannelling model based on Feldman’s method, which is in a good agreement with the TRIM96 calculation. For the samples with dose of 5×1014 ions/cm2 and more, an abnormal annealing behavioar was found and a qualitative explaination has been given.

Rutherford backscattering analysis of Bi-based superconducting films

The elemental composition, film thickness and concentration depth profiles of precursor and superconducting (Bi, Pb)–Sr–Ca–Cu–O films were studied by the Rutherford backscattering spectrometry (RBS) technique. The precursor films were deposited on MgO single-crystalline substrates with an aerosol atomized ultrasonically from an aqueous nitrate solution. Precursor films, approximately 5–5.5 μm thick, were then annealed in air at temperatures ranging from 835 to 855°C for 10 h. X-Ray diffraction studies revealed mainly the presence of the 2212 phase (for the bulk, T c is approx. 85 K). Films annealed at temperatures T a≥850°C were superconducting, with T c in the range 60–71 K showing a double T c onset at 85 K and 110 K. The RBS study of the Bi depth profile of precursors showed a maximum content of Bi at a depth of approximately 1–2 μm from the film surface. After film annealing, the Bi content was found to be constant from the surface to approximately 1 μm depth, then decreasing in value towards the film–substrate interface.

Radiation damage and annealing behavior of 2.0 MeV 160Er + implanted silicon

Radiation damage and annealing behavior of Si (100) implanted with 2 MeV Er + ions with various doses have been investigated using Rutherford backscattering spectrometry and channelling (RBS/C) technique. The damage profile of silicon substrate induced by 2.0 MeV E +, at a dose of 1×10 14 ions cm −2 was extracted using the multiple-scattering dechannelling model of Feldman, and the result is in good agreement with the TRIM96 calculation. The experimental results show that the annealing behavior of 2.0 MeV Er + implanted into silicon is strongly influenced by the implantation dose and annealing temperature. For the samples with dose of 5×10 14 ions cm −2 and more, an abnormal annealing behavior was found and a qualitative explanation has been given.