Characterization of ion-implanted silicion by Rutherford backscattering spectrometry and ellipsometry

It is demonstrated that the information obtained by Rutherford backscattering spectrometry and channeling technique can substantially help in the construction of a realistic optical model for the ellipsometry of ion-implanted silicon. In the case of fully amorphous ion-bombarded layers, the ellipsometry is a fast, non-destructive and contactless method to estimate the thickness of these films. For buried and partially disordered layers a qualitative interpretation of different trajectories in the - plance can be given on the basis of channeling measurements.     

Quantification of Auger depth profiles by means of Rutherford backscattering spectrometry

Conclusion Due to their complementary character, AES and RBS can give a very rich set of information when they are combined for profiling thin films. The interpretation of data is easier and more accurate when a same simulated structure is fitted successively to the RBS and AES data.

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Quantifizierung von Auger-Tiefenprofilen mit Hilfe der Rutherford-Rückstreu-Spektrometrie

     

Graphical analysis of Rutherford backscattering spectra

A graphical method was developed to relate data from Rutherford backscattering spectrometry to sample characteristics, such as thickness and concentration profiles. The method was then applied to analyze these characteristics of a gold film.     

Bromine enrichment in the near-surface region of Br-doped NaCl single crystals diagnosed by Rutherford backscattering spectrometry

Bromine released from sea-salt aerosols and seawater ice is known for its high chemical reactivity. Previous studies have suggested that its availability to the gas-phase could be enhanced by segregation processes increasing Br concentration on the aerosol surface as compared to the bulk. However, little is known about the composition within the near-surface region, that is, the outermost approximately 100 monolayers. We used Rutherford backscattering spectrometry (RBS) to measure Br concentration profiles to a depth of about 750 nm of Br-doped NaCl single crystals to characterize the thermodynamics and kinetics of Br segregation to the near-surface region in moist air. These experiments were carried out on cleavage planes of melt-grown and of annealed solution-grown crystals at room temperature and relative humidities (RH) too low for formation of a stable liquid phase. Segregation of Br was below the detection limit on melt-grown crystals with Br/Cl = 0.01. In the case of annealed solution-grown crystals with Br/Cl = 0.002, average segregations of (0.24 +/- 0.11) x 10(15) and (0.42 +/- 0.12) x 10(15) Br atoms cm-2 were observed at 50% and 65% RH, respectively. No segregation was found at 20% RH. The observed Br segregation can be explained by the formation of an adsorbed liquid layer (depending on crystal surface properties and relative humidity) and preferential, diffusion-limited dissolution of Br into this layer according to the partition coefficient of Br between aqueous and solid NaCl. The thickness of the adsorbed liquid layer, which depends on crystal surface geometry and on relative humidity, can be estimated to range from 4 to at most 59 nm on the basis of measured Br concentrations and partition coefficients. Applying this concept of partitioning to natural sea salt suggests a Br/Cl molar ratio of up to 0.2 in adsorbed surface water of crystallized natural aerosol particles compared to about 0.0015 in seawater. This would have a major impact on heterogeneous reactions on sea-salt particles under dry conditions such as in the freeze-dried Arctic boundary layer.     

Thermal oxidation of silicon studied by high resolution Rutherford backscattering

Rutherford backscattering provides a simple experimental technique for investigating the thermal oxidation of silicon containing heavy impurity species. The technique provides both mass and depth analysis of para-surface layers. Using conventional apparatus, typical depth resolution is 250Å N. This paper describes a simple method of improving the resolution to ～25 Å. The method is then illustrated with data on the analysis of thin (<300Å) layers of thermally oxidised silicon containing ion-implanted impurities. The effect of the type and dose of implanted ions on oxidation rate has been measured. The re-distribution of implanted ions during thermal oxidation is also investigated.     

Nanometric resolution in glow discharge optical emission spectroscopy and Rutherford backscattering spectrometry depth profiling of metal (Cr,Al) nitride multilayers

In this work, we address the capability of glow discharge optical emission spectroscopy (GDOES) for fast and accurate depth profiling of multilayer nitride coatings down to the nanometer range. This is shown by resolving the particular case of CrN/AlN structures with individual thickness ranging from hundreds to few nanometers. In order to discriminate and identify artefacts in the GDOES depth profile due to the sputtering process, the layered structures were verified by Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM). The interfaces in the GDOES profiles for CrN/AlN structures are sharper than the ones measured for similar metal multilayers due to the lower sputtering rate of the nitrides. However, as a consequence of the crater shape, there is a linear degradation of the depth resolution with depth (approximately 40 nm/μm), saturating at a value of approximately half the thickness of the thinner layer. This limit is imposed by the simultaneous sputtering of consecutive layers. The ultimate GDOES depth resolution at the near surface region was estimated to be of 4–6 nm.     

Trace element determination in tomato puree using particle induced X-ray emission and Rutherford backscattering

Particle induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) were used to determine the concentrations of trace elements in samples of 12 tomato puree brands sold in the Mexican market. While RBS offered information about the main elements present in the matrix, PIXE gave results on trace elements. As a whole, data for 17 elements (C, N, O, Na, Mg, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, and Zn) were obtained. To evaluate the results, a comparison with brands from USA, Japan, Colombia, and Chile was carried out, using tomato purees produced following the domestic technology recipe. Additionally, the results were considered in the light of the Codex Alimentarius and the Mexican standard. It was found that all of the brands fall within the limits established by these standards, being of the same order of magnitude as the foreign brands. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thin film characterisation using backscattering spectrometry

The use of proton resonance backscattering spectrometry for the estimation of carbon as thin films formed on a target material is discussed. Conventional He backscattering experiments were also carried out on TiVN films formed on beryllium backing but the determination of stoichiometry of these films were difficult using conventional software for depth resolution.     

Magnetic antidot arrays on alumina nanoporous membranes: Rutherford backscattering and magnetic characterization

Highly ordered antidot arrays of permalloy have been prepared by sputtering onto different nanoporous alumina membranes (NAMs) and characterized by Rutherford backscattering spectrometry (RBS), SEM and Vibrating sample magnetometry (VSM). RBS spectrometry combined with SEM image analysis provides information on the in‐depth composition and porosity of the different magnetic antidot nanostructures. The coercivity increases in the antidot nanostructures as compared with that of its parent continuous film. The saturation magnetization values of the antidot nanostructures are observed to increase with increasing pore size. Our results suggest an enhanced magnetization at the Fe₂₀Ni₈₀/Al₂O₃ interface. Copyright © 2011 John Wiley & Sons, Ltd.     

Rutherford backscattering for measuring corrosion layers on glasses for long-term storage of radioactive waste

Summary The method considered safest for isolation of nuclear waste is vitrification (solidification in a glass or glassceramic matrix) with long-term storage in stable geological repositories. Borosilicate glasses are candidates for this purpose on a world-wide scale. Though it is very unlikely that water will ever have access to these repositories, the leaching (corrosion in aqueous solutions) of glasses is studied. Rutherford backscattering of beams of charged particles (e.g. He-ions of 2–3 MeV energy) is shown to be a versatile technique to study surface layers and to obtain information on their thickness and composition. The method is non-destructive and can be applied to layers with thicknesses in the range of about 0.1 to 2 m. Results for nuclear waste glasses leached in H₂O or in quinary salt solution (Q-brine) with and without presence of material from the metal container are presented. Presence of steel is shown to greatly enhance leaching rates by preventing glass components to become saturated in the leachant.

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Rutherford-Rückstreuung zur Messung von Korrosionsschich ten an Gläsern zur Langzeitlagerung radioaktiver Abfälle

Zusammenfassung Die Verglasung nuklearer radioaktiver Abfälle (Verfestigung in einer Glasoder Glaskeramikmatrix) mit Langzeitlagerung in stabilen geologischen Lagerstätten wird als sicherste Methode zur Isolation der Abfälle betrachtet. Borosilicatgläser sind weltweit Hauptkandidaten für diesen Zweck. Obzwar es sehr unwahrscheinlich ist, daß Wasser jemals Zugang zu diesen Lagerstätten haben wird, werden Auslaugprozesse (Korrosion in wäßrigen Lösungen) der Gläser untersucht. Die Rutherford-Rückstreuung geladener Teilchenstrahlen (z.B. He von 2–3 Me V Energie) wird als vielseitige Methode zur Untersuchung von Oberflächenschichten vorgestellt, die Information liefert über Schichtdicke und Schichtzusammensetzung. Die Methode ist zerstörungsfrei und kann für Schichten im Dickenbereich von ca. 0,1–2 m benutzt werden. Ergebnisse werden beschrieben für Gläser für nukleare Abfälle, die in H₂O oder in quinärer Salzlösung (Q-brine) allein oder in Gegenwart von Proben der vorgesehenen metallischen Behältermaterialien ausgelaugt wurden. Es wird gezeigt, daß in Gegenwart von Stahl die Auslaugraten wesentlich erhöht werden, da eine Sättigung von Glaskomponenten in der Auslauglösung verhindert wird.

     

Sorption and diffusion of gases in a polyimide

Sorption and diffusion of gases (CO₂, N₂, and He) in a polyimide (PI2080) film were measured by using an apparatus which gives the sorption rate curves from the initial state to the equilibrium state. Nonlinear isotherms observed for CO₂ sorption were interpreted successfully in terms of the dual-mode model for sorption in glassy polymers. Linear isotherms observed for N₂ and He seemed to obey Henry's law. Two diffusion coefficients (D_I and D_E) were obtained using the short-time method and the long-time method for a Fickian diffusion model, together with the equilibrium solubility (C_e) from each experiment. The initial sorption rate curves agreed with the calculated curves using D_I, however near sorption equilibrium the curves are in accord with the calculated curves using D_E. These observations suggest that some relaxation process is superimposed on the diffusion process. The non-Fickian transport data were correlated successfully with a model that combines time-dependent diffusion and the Fickian model.     

Characterization of the superficial region of solids using the Rutherford backscattering method with charged particles

In the first part of this work, we show the basic principle of the Rutherford backscattering method and follow the possibilities and performance allowed. We also discuss how to choose the best experimental configuration to provide most significant spectrum in the case of glass surface analysis.     

Characterization of tantalum pentoxide films with backscattering spectrometry

The backscattering performance of 2 MeV He⁺ and N⁺ beams was studied using Ta₂O₅ targets as test targets. To allow ready comparison, the scattering geometry, projectile energy, and detection system were kept identical for both beams. Tantalum oxide films with thicknesses of 200 Å to 4000 Å were examined. For thickness determinations, beam straggling was found to be the major limiting factor. For thickness measurements below 1000 Å the N⁺ beam is best suited for larger thicknesses; the He⁺ beam is superior. For stoichiometric determinations both beams provide equally accurated and precise data.     

Sorption and diffusion of water vapor in polyimide films

Sorption and diffusion of water vapor are investigated gravimetrically for polyimide films. The activity dependence of the solubility and diffusion coefficients, S and D, respectively, is classified under four types: (1) constant S and D type, (2) dual-mode sorption and transport type, (3) dual-mode type followed by a deviation due to a plasticization effect at high vapor activity, and (4) constant S and D type followed by a deviation due to water cluster formation at high activity. For the dual-mode type, the Henry's law component is much larger than the Langmuir component except at low activity, and therefore deviation in behavior from the first type is small. S is larger for polyimides with higher content of polar groups such as carbonyl, carboxyl, and sulfonyl. D is larger for polyimides with a higher fraction of free space, with some exceptions. The polyimide from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and dimethyl-3,7-diaminodibenzothiophene-5, 5-dioxide belongs to the third type and displays both large S and large D. The polyimide from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 4,4′-oxydianiline belongs to the fourth type, and has the largest D but rather small S because of the hydrophobic C(CF₃)₂ groups. © 1992 John Wiley & Sons, Inc.     

NMR studies of water in polyimide films

Commercial polyimide films containing up to ～ 3 wt % water have been studied by proton, deuteron, and oxygen-17 nuclear magnetic resonance (NMR). Comparisons between NMR results and previous dielectric relaxation (DR) results for a variety of Kapton films show that there is a one-to-one correspondence between specific dielectric loss peaks and features of the ²H or ¹⁷O NMR spectra. It is concluded that water molecules, which interact only weakly with the polymer, reside in the polyimide matrix in two configurations, randomly oriented single molecules and chains of water molecules oriented perpendicular to the plane of the film. The correspondence between NMR and DR observed in water in Kapton extends to water in Upilex and to methanol and acetic acid in Kapton. © 1995 John Wiley & Sons, Inc.     

Curing studies of a polyimide precursor

Complexes between diphenylcarbamido-dicarboxybenzene and 1-methyl-2-pyrrolidinone, 1/4 and 1/2 M, are obtained by reacting pyromellitic dianhydride with aniline in the solvent 1-methyl-2-pyrrolidinone. Decomplexation and imidization of this diamic acid are studied by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectrometry, polarizing microscopy, and gas chromatography/mass spectrometry. Side reactions competing with the imide formation are discussed. The presence of solvent is found to markedly influence imidization.     

Temperature effect on solvent diffusion in rigid and semirigid polyimide films

The diffusion of NMP (n-methyl-pyrrolidinone) solvent in a semirigid rod-like PMDA-ODA (pyromellitic dianhydride-4,4′-oxydianiline) film coated on silicon is found to be case I diffusion at temperatures ranging from 30 to 90°C by the use of a bending beam technique. The diffusion constant increases for the 7.4 μm PMDA-ODA film (which was cured at 300°C) from 3.3 to 318 × 10^?11 cm²/s as the diffusion temperature increases from 30 to 90°C. The corresponding hygroscopic stress in the direction parallel to the film decreases with the increase of temperature, possibly due to the softening of the film at elevated temperatures. The diffusion mechanism, however, changes from case II to case I in a rigid rod-like PMDA-PDA (pyromellitic dianhydride-p-phenylenediamine) film when the diffusion temperature increases. The change in the diffusion mechanism occurs at a higher temperature for thinner films, presumably due to higher ordering and/or orientation in the films. The activation energy for NMP diffusion in the PMDA-ODA films markedly decreases from 93 to 59 kJ/mole as the film thickness increases from 2.2 μm to 11.3 μm. This may also be attributed to decreased ordering in thicker films. © 1994 John Wiley & Sons, Inc.     

A study of solvent diffusion in thin polyimide films using laser interferometry

Using laser interferometry, we have determined in situ the thickness increase with time of thin supported polyimide films (4–8 μm in initial thickness) immersed in n-methyl-2-pyrrolidone (NMP) as a function of NMP temperature (22–120°C). Similar experiments were also performed in dimethyl sulfoxide (DMSO) at 22°C with polyimide films of 4.1 μm in thickness. For NMP, the equilibrium fractional thickness increase (about 20%) is independent of initial polyimide thickness and temperature. The time scale for reaching equilibrium sharply decreases with temperature from 2–3 days at 22°C to 30–60 min at 120°C. Compared with NMP, the rate of DMSO sorption is considerably faster, reaching equilibrium swelling of about 28% in about 5 h at 22°C. To describe the transport process, we applied a phenomenological model proposed by Astarita and Sarti¹ but reformulated in polymer fixed frame to enable straightforward comparison with the thickness data. Our analysis indicated that the transport of NMP is best described as anomalous, that is, intermediate between diffusion controlled and case II transport. The effective diffusion coefficient D_eff and the front velocity U₀ at 22°C were found to be 3–6 × 10^?12 cm²/s and 8 × 10^?9 cm/s, respectively. Our front velocity is in good accord with the value of 6 × 10^?9 cm/s obtained for a similar polyimide based on gravimetric measurements.² Both D_eff and U₀ show an activation energy of ～56 kJ/mol. For DMSO, however, the transport is clearly case II. The front velocity at 22°C was found to be about 6 × 10^?8 cm/s, which is about four times that obtained by Rutherford back-scattering spectrometry.³     

Thermal studies of hypervalent iodine reagents

The use of unconventional synthesis methods in the formation of CaO·2Al₂O₃ (CA₂) is justified because it reduces the formation temperature of the compound. CA₂ is formed by classical method at temperatures above 1,400 °C. The polymeric precursor method allows a significant temperature decrease in CA₂ synthesis reaching temperatures of 1,000 °C. This paper deals with CA₂ synthesis by “citrate” method which is often presented as Pechini method, starting from a mixture of citric acid, ethylene glycol and calcium, and aluminum nitrates. A method based on the formation of a polymeric precursor was also used, starting from a mixture of acrylic acid and nitrates of calcium and aluminum. The results showed a net difference in favor of samples obtained from acrylic acid, which by annealing at 800 °C for 1 h, contain pure CA₂. The samples obtained from citric acid, after annealing at 800 °C are amorphous. After annealing at 900 °C in all samples CA₂ is single phase.