Anomalous Depth Profiles Research Articles

Activation of gas bubble emissions indicated by the upward decreasing Lead-210 activity at a submarine mud volcano (TY1) offshore southwestern Taiwan

A submarine mud volcano (MV) known as TY1 is one of the largest conical structures found offshore southwestern Taiwan. Active gas bubble emissions at the flat crest of the mud volcano disperse sediment particles into the water column. Changes in the mud volcanism of TY1 were revealed by radiograph and grain size analysis of the sediment cores. 210Pb geochronology was applied to the near-seafloor sediments to reveal the detailed mud volcanism from the deposition rate. In a 58-cm long sediment core taken from the northern margin of the crest, known as TY1-N.170, the size and frequency of the mud clasts decrease upward. The clasts are smaller than 8mm above a sediment depth of 34cm below the sea floor (cmbsf). Sediments between 0 and 19 cmbsf are massive, and particles larger than 2mm are absent. An enrichment of coarse, silt-sized particles in the massive sediment unit and the restricted distribution of the unit suggest that the massive unit was generated by re-deposition of sediment particles that were dispersed into the water column by gas bubble emission. These characteristics suggest that during the last mud volcanism of TY1, there was a decrease in mud eruption energy, and gas bubble emission became the main activity. In core TY1-S.440, taken from the southern slope, a massive sediment unit enriched with coarse, silt-sized particles, is intercalated between mud breccia structures. This suggests repeated mud breccia flows caused by TY1. The excess 210Pb activity present in the massive sediment unit of TY1-N.170 suggests activation of gas bubble emission. In the massive unit, a decrease in excess 210Pb activity appears upward toward the seafloor. The highest value is 3.1dpm/g at 19.8cmbsf (26.4g/cm2 in cumulative mass); values lower than 1.0dpm/g are distributed 2.8–6.8 cmbsf (3.6–8.8g/cm2). The upwardly decreasing trend is opposite that of the reference core from which a reasonable areal sedimentation rate was obtained using a constant-flux constant-sedimentation model. The anomalous depth profile at the massive unit indicates an increasing rate of sediment deposition, which originated from the activation of gas bubble emission.

Interfacial Binding of Divalent Cations to Calixarene-Based Langmuir Monolayers

The interactions of Langmuir monolayers produced through the self-assembly of an amphiphilic p-carboxycalix[4]arene (1) with a series of divalent, fourth-period transition metals, at the air-water interface, were investigated. Changes in the interfacial behavior of 1 in response to the presence of CuCl2, CoCl2, MnCl2, and NiCl2 were studied by means of Langmuir compression isotherms and Brewster angle microscopy (BAM). The measurements revealed that the self-assembly properties of 1 are significantly affected by Cu(2+) ions. The interactions of 1-based monolayers with Co(2+) and Cu(2+) ions were further investigated by means of synchrotron radiation-based X-ray reflectivity (XRR), X-ray near-total-reflection fluorescence (XNTRF), and grazing incidence X-ray diffraction (GIXD). XNTRF and XRR analyses revealed that the monolayer of 1 binds more strongly to Cu(2+) than Co(2+) ions. In the presence of relatively high concentrations of Cu(2+) ions in the subphase (1.4 × 10(-3) M), XNTRF exhibited anomalous depth profile behavior and GIXD measurements showed considerably strong diffuse scattering. Both measurements suggest the formation of Cu(2+) clusters contiguous to the monolayer of 1.

High-fluence implantation of iron into polyimide

Polyimide–Kapton (PI) foils were implanted with 40 keV Fe + ions to a fluence of 0.25×10 17, 0.75×10 17 and 1.25×10 17 cm −2 at ion current density of 4, 8 and 12 μA cm −2. The structure and composition of the modified PI were studied using Rutherford backscattering spectroscopy (RBS), proton-induced X-ray emission (PIXE) and transmission electron microscopy (TEM). A carbonaceous layer filled with up to 25 at.% of agglomerated metal particles is formed under the sample surface. Anomalous depth profiles of the implanted metal atoms, consisting of a strong near-surface peak and two weaker ones under the implanted layer, are observed. Possible mechanisms of the metal redistribution after implantation are discussed. The depth profiles of the implanted metals are not influenced by increasing ion current density. Under thermal annealing at 300 °C for 120 min, slow inward diffusion of Fe atoms is observed with diffusion coefficient 0.5–1×10 −16 cm 2 s −1.

Anomalous depth distribution of Fe and Co atoms in polyimide implanted to high fluence

Polyimide foils were implanted with 40 keV Fe + and Co + ions to the fluences of 2.5×10 16–1.25×10 17 cm −2 at ion current densities of 4, 8 and 12 μA/cm 2. Structural and composition alterations of the implanted polymer are studied using transmission electron microscopy and Rutherford back-scattering methods. Ion implantation results in formation of the near-surface carbonaceous layer filled up to 25 at.% of the embedded metal. Anomalous depth profiles of the metals, consisting of a strong near-surface peak and two weaker ones beyond the implanted layer, are observed. Possible mechanisms of the metal redistribution are discussed.

Anomalous depth profile of implanted fluorine ions in SiO 2/Si

Fluorine ions have been implanted into SiO 2/Si with an energy of 30 keV at doses of 0.5 and 1 × 10 17 ions/cm 2. Depth profiles of fluorine have been studied by X-ray photoelectron spectroscopy (XPS) for both as-implanted and annealed samples. It was found that depth profiles of fluorine in SiO 2/Si did not agree with the predicted Gaussian profiles and showed an enhancement of fluorine concentration in SiO 2 region for as-implanted samples. It is thought that anomalous depth profiles may be due to rather high diffusion coefficient in Si than that in SiO 2 as a result of fluorine implantation. After annealing at 700 ∘C for 30 min, fluorine concentrations considerably decreased in Si region compared with in SiO 2 region. It could be considered that the oxide layers prevent the fluorine diffusion and the fluorine is trapped at around the SiO 2/Si interface.

Anomalous depth profiles and diffusional behavior of noble gases implanted into photoresist films

In the present work are reported results of thermal diffusion of Kr implanted into AZ1350 positive photoresist films and Xe implanted into “waycoat” negative photoresist films. Kr and Xe ions were implanted at 80 K and the depth profiles determined “in situ” by using the Rutherford backscattering technique in a 80–273 K temperature range. The extracted Kr diffusion coefficients follow a linear Arrhenius plot over the studied temperature range with a characteristic activation energy of E b = 100 meV. The Xe diffusion into the “waycoat” photoresist develops in a very narrow temperature range (210–230 K) which only allows determination of the diffusion coefficient at 230 K. Comparison between the present and previous published results show that Kr and Xe display very similar diffusional characteristics when implanted in the AZ1350 photoresist. On the other side, the diffusion into the “waycoat” photoresist seems to be much faster than in the AZ1350 film.

Doping of ion implanted polyethylene with metallocarborane

Polyethylene samples implanted with 150 keV F + ions to the doses from 5 × 10 13−1 × 10 15cm −2 were exposed to 0.05 M water solution of metallocarborane [(C 2B 9H 11) 2Co]Cs at temperatures of 24, 50 and 85°C, and the diffusion and incorporation of elements in the sample surface layer were studied using Rutherford back-scattering and neutron depth profiling techniques. The amount of incorporated B and Cs atoms was found to be an increasing function of the temperature for all implanted doses. The indiffusion and incorporation of the [(C 2B 9H 11) 2Co] − anion and the Cs + cation proceed separately and the final B Cs ratio is well below metallocarborane stoichiometry in most cases. The total amount of incorporated Cs and B atoms and their depth profiles depend on the implanted dose in very complicated manner. For lower implanted doses anomalous depth profiles of B and Cs, roughly following calculated profiles of electronic energy loss of F + ions are observed.

Formation of light-hydrocarbon anomalies in oceanic waters

Anomalous depth profiles of hydrocarbon tracers of thermogenic origin have been reported at various marine locations, including Ragay Gulf, the Philippines. Until now the origin of such profiles remained unexplained. We present a quantitative numerical model in which the bottom-water anomalies are interpreted as transient states of the hydrocarbon plume intermittently seeping from the ocean floor and mixing with the stratified water. An anomalous midwater plume forms because of different mixing regimes in the water column. For typical values of the vertical and horizontal mixing coefficients in the ocean, the anomalies may persist for periods up to ∼1 yr.

Anomalous depth profiles of light ions and noble gases implanted into polymers

We report on a depth profile study of 6Li and noble gases implanted into the AZ111 photoresist. The measured profiles of 6Li confirm previous data for light ions (B and F) showing that above a threshold implantation energy part of the implanted ions redistribute according to the TRIM calculated ionization profile. The noble gases Ar, Kr and Xe have shown noticeable diffusion after room temperature implantation. Two regimes of diffusional behaviour were observed corresponding to the damaged and non-damaged regions of the polymer. The diffusion in the damaged region strongly depends on fluence showing a behaviour similar to that of resistivity in ion irradiated polymers.

Wear Properties and Surface Structure of Ion Implanted Glassy Carbon

ABSTRACTWear properties of Li+, K+, C+, Cl+, and Ti+ implanted glassy carbons (GC) have been studied by wear tests using silicon carbide abrasive paper. It has been found that ion implantation is effective for improving wear resistance of GC. The measurements of Raman spectra revealed formation of an amorphous structure on the surface. Anomalous depth profiles with flat concentration distribution of Li and K atoms were observed by a secondary ion mass spectroscopy (SIMS). In conclusion. the formation of an amorphous structure seems to explain the improvement in wear resistance.

Effects of heat treatments of GaAs on the near-surface distribution of EL2 defects

A cluster model is proposed for the midgap state EL2 in GaAs based on a defect reaction similar to that of the thermal donor formation in silicon. Anomalous depth profiles of the EL2 defects in bulk GaAs created by heat treatment have been quantitatively explained, assuming that the EL2 defect is a four point defect cluster. Possible candidates of the point defects are discussed.

A nuclear microprobe analysis of laser treated aluminium implanted with antimony

Laser processing of materials, being a rapid melt quenching process, quite often produces a surface which is far from being ideally smooth for ion beam analysis. We have used a 50 μm × 50 μm microbeam of 3.05 MeV He + (obtained from the Harwell nuclear microprobe) to overcome such problems during the RBS analysis of laser treated aluminium implanted with Sb (30 keV, 1.7 × 10 17 Sb + ions/cm 2). Laser treatment was done in air with single pulses (7 ns fwhm, peak energy density 2–5.7 J/cm 2) obtained from a Nd: glass laser operating in a TEM 00 mode. Scanning electron microscopy on the laser treated area shows a very smooth central region surrounded by an annular ring with coarseness gradually increasing radially outwards till the melt threshold is reached. A radial RBS scan with the microbeam reveals distinctly different Sb depth profiles for coarse and smooth regions. The coarse regions extending up to an absorbed energy density of 0.2 J/cm 2, show flat Sb concentration profiles up to depths ∼3.5 μm (uper limit determined by RBS with 4.8 MeV He + using the BARC Van de Graaf accelerator). Such anomalous depth profiles are shown to be incompatible with liquid phase diffusion and are interpreted as a consequence of convective effects. The smooth regions at higher absorbed power do not show such convective effects. The Sb profiles become broader with considerable Sb depletion near the surface. A detailed liquid phase diffusion analysis incorporating melt front motion and segregation effects has been performed. Effective distribution coefficient = 1 (as compared to the equilibrium value of ∼7), diffusion coefficient ∼5 × 10 3 cm 2/s and evaporation loss ⪅15% are parameters obtained. The use of a nuclear microprobe is shown to be indispensable for analysis of laser treated materials exhibiting a wide range of surface coarseness.

Radiation enhanced diffusion of bromine in sodium chloride crystal

Abstract It is shown that the diffusion of the bromine impurities into a NaCl single crystal is enhanced by MeV He+ ion bombardment and that this enhancement is due to the ionization-induced vacancies. The diffused bromine impurities show anomalous depth profile and this is discussed in terms of the concentration-dependent diffusivity.