Depth Profile Measurements Research Articles

XPS depth profile of plasma-activated surface of beech wood (Fagus sylvatica) and its impact on polyvinyl acetate tensile shear bond strength

High surface selectivity of atmospheric pressure plasma treatment was demonstrated experimentally by XPS depth profile measurement of plasma-activated beech wood. Wood surface activated by diffuse coplanar surface barrier discharge was sequentially sputtered by Ar+ ion beam followed by immediate XPS analysis of freshly uncovered surface. According to the assessment, less than 330 nm of sputtered material was sufficient for complete removal of all plasma-formed functional groups. For the sake of practical implications of minimal vertical extent of plasma-mediated changes, the character of tensile shear bond strength improvement of polyvinyl acetate adhesive was examined with respect to its specific mass. A constant additive character of plasma activation to the bond strength was observed within the examined range of adhesive-specific mass.

Chronological change of electrical resistance in GeCu2Te3 amorphous film induced by surface oxidation

Unusual chronological electrical resistance change behavior was investigated for amorphous GeCu2Te3 phase change material. More than a 1 order decrease of electrical resistance was observed in the air even at room temperature. The resistance of the amorphous film gradually increased with increasing temperature and then showed a drop upon crystallization. Such unusual behavior was attributed to the oxidation of the amorphous GeCu2Te3 film. From the compositional depth profile measurement, the GeCu2Te3 film without any capping layer was oxidized in air at room temperature and the formed oxide was mainly composed of germanium oxide. Consequently, a highly-conductive Cu-rich layer was formed in the vicinity of the surface of the film, which reduced the total resistance of the film. The present results could provide insight into the chronological change of electrical resistance in amorphous chalcogenide materials, indicating that not only relaxation of the amorphous, but also a large atomic diffusion contributes to the chronological resistance change.

Lithium diffusion in polyether ether ketone and polyimide stimulated by in situ electron irradiation and studied by the neutron depth profiling method

Diffusion of lithium from a LiCl aqueous solution into polyether ether ketone (PEEK) and polyimide (PI) assisted by in situ irradiation with 6.5 MeV electrons was studied by the neutron depth profiling method. The number of the Li atoms was found to be roughly proportional to the diffusion time. Regardless of the diffusion time, the measured depth profiles in PEEK exhibit a nearly exponential form, indicating achievement of a steady-state phase of a diffusion–reaction process specified in the text. The form of the profiles in PI is more complex and it depends strongly on the diffusion time. For the longer diffusion time, the profile consists of near-surface bell-shaped part due to Fickian-like diffusion and deeper exponential part.

Low-temperature lithium diffusion in simulated high-level boroaluminosilicate nuclear waste glasses

Ion exchange is recognized as an integral, if underrepresented, mechanism influencing glass corrosion. However, due to the formation of various alteration layers in the presence of water during the corrosion process, it is difficult to conclusively deconvolute the mechanisms of ion exchange from other simultaneously occurring processes. In this work, an inert non-aqueous solution was used as an alkali source material to isolate ion exchange and study the solid-state diffusion of lithium. Specifically, the experiments involved contacting simulated nuclear waste glass coupons, the 6-oxide CJ6 and the 26-oxide SON68, with a non-aqueous solution of 6LiCl dissolved in dimethyl sulfoxide at 90°C for various time periods. The depth profiles of major elements in the glass coupons were measured using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Lithium interdiffusion coefficients, DLi, were then calculated based on the measured depth profiles. The results indicate that the penetration of 6Li is faster in the simplified CJ6 (D6Li≈4.0–8.0×10−21m2/s) compared to the more complex SON68 (D6Li≈2.0–4.0×10−21m2/s). These values are roughly an order of magnitude greater than measured water diffusion in glasses at similar temperatures. Additionally, sodium ions present in the glass were observed to participate in ion exchange reactions with lithium from the solution. Implications of the diffusion coefficients obtained in the absence of alteration layers to the long-term performance of nuclear waste glasses in a geological repository system are also discussed.

Self-organization of mesoscopic silver wires by electrochemical deposition.

Long, straight mesoscale silver wires have been fabricated from AgNO3 electrolyte via electrodeposition without the help of templates, additives, and surfactants. Although the wire growth speed is very fast due to growth under non-equilibrium conditions, the wire morphology is regular and uniform in diameter. Structural studies reveal that the wires are single-crystalline, with the [112] direction as the growth direction. A possible growth mechanism is suggested. Auger depth profile measurements show that the wires are stable against oxidation under ambient conditions. This unique system provides a convenient way for the study of self-organization in electrochemical environments as well as for the fabrication of highly-ordered, single-crystalline metal nanowires.

Determination of the thickness distribution of a graphene layer grown on a 2″ SiC wafer by means of Auger electron spectroscopy depth profiling

Auger electron spectroscopy (AES) depth profiling was applied for determination of the thickness of a macroscopic size graphene sheet grown on 2in. 6H-SiC (0001) by sublimation epitaxy. The measured depth profile deviated from the expected exponential form showing the presence of an additional, buffer layer. The measured depth profile was compared to the simulated one which allowed the derivation of the thicknesses of the graphene and buffer layers and the Si concentration of buffer layer. It has been shown that the graphene-like buffer layer contains about 30% unsaturated Si. The depth profiling was carried out in several points (diameter 50μm), which permitted the constructing of a thickness distribution characterizing the uniformity of the graphene sheet.

Dynamic measurements of Li depth profiles in a Li‐ion battery system under charging condition by means of ERD and RBS techniques

Depth profiles of Li in a Li‐ion battery system of Au/LiCoO2/LATP/Pt (LATP:Li1+X+YAlYTi2−YGeXP3−XO12) have been in situ measured at several stages of charging by means of the elastic recoil detection (ERD) and Rutherford backscattering (RBS) techniques with 9 MeV O4+ ion beam. The thicknesses of LiCoO2 and Au are estimated from the RBS spectrum for the as‐received specimen to be 190 and 27 nm, respectively. From the ERD spectrum, it is also found that there exists impurity hydrogen of ~5% in LiCoO2. Moreover, it is found from the ERD data analysis after the first charging of 0.48 × 1016 e/cm2 to Au electrode that the fractional concentration of Li in LiCoO2 at the interface with Au electrode steeply decreases to 0.8, recovers with depth toward the interface with LATP and attains at 1.3 above the original value. With increasing the amount of charge supplied, the slope in the Li composition from Au electrode to LATP increases gradually. The data on the charging is concluded to include the irradiation effects due to the incident O ions, since the data on a non‐irradiated part of the specimen obtained after finish of the charging shows that Li is almost completely reduced from LiCoO2. The dynamics of Li composition in LiCoO2 as a function of charging supplied is discussed in connection with hydrogen impurity and irradiation effect of the incident O ions. Copyright © 2014 John Wiley & Sons, Ltd.

Influence of Layer Removal Methods in Residual Stress Profiling of a Shot Peened Steel Using X-Ray Diffraction

For X-Ray Diffraction Measurement of Depth Profiles of Residual Stress, Step-Wise Removal of Materials has to be Done to Expose the Underneath Layers to the X-Rays. this Paper Investigates the Influence of Layer Removal Methods, Including Electro-Polishing in Two Different Electrolytes and Chemical Etching, on the Accuracy of Residual Stress Measurement. Measurements on Two Shot-Peened Steels Revealed Large Discrepancy in Subsurface Distributions of Residual Stress Obtained with the Respective Methods. Especially, the Chemical Etching Yielded much Lower Subsurface Compressive Stresses than the Electro-Polishing Using a so Called AII Electrolyte. the Difference was Explained by the Influence of the Different Layer Removal Methods on the Microscopic Roughness.

Electrochemical Growth of Surface Oxides on Nickel. Part 3: Formation of β-NiOOH in Relation to the Polarization Potential, Polarization Time, and Temperature

Electro-oxidation of Ni(poly) in 0.5 M aqueous KOH solution is examined at various polarization potentials (Ep), polarization times (tp), and temperatures (T) in the 0.7 ≤ Ep ≤ 1.2 V versus RHE, 60 ≤ tp ≤ 10,800 s, and 288 ≤ T ≤ 318 K ranges. The oxide chemical composition is determined using X-ray photoelectron spectroscopy (XPS) and its thickness using XPS depth profiling. XPS measurements demonstrate that such formed oxide layers are multilayer in nature and contain both β-Ni(OH)2 and NiO, with β-Ni(OH)2 being the predominant, outermost species and NiO forming a thin layer sandwiches between metallic Ni and β-Ni(OH)2. An increase of Ep, tp, and/or T results in an increase of the oxide thickness. XPS depth profiling measurements reveal that the thickness (d) of the β-Ni(OH)2 plus NiO layers is in the 2 ≤ d ≤ 11 nm range, depending on Ep, tp, and T. The electrochemical formation of β-Ni(OH)2 plus NiO follows an inverse-logarithmic growth kinetic law with the escape of metal cation from the metal into the oxide at the inner metal/oxide interface being the rate-determining step. The oxide growth is treated mathematically using the Mott–Cabrera oxide growth theory.

Quantitative Analysis of Hemodynamics in Bruised Skin Using Photothermal Depth Profiling

Pulsed photothermal radiometry (PPTR) allows noninvasive measurement of laser-induced temperature depth profiles, providing useful information on depth distribution of specific absorbers in optically scattering biological tissues. In the present study, PPTR profiling is combined with numerical modeling of light transport in human skin to analyze hemoglobin dynamics in traumatic bruises. Specifically, the influence of regularization degree, applied in iterative reconstruction of temperature depth profiles from PPTR signals measured in bruised volunteers, is studied. The results show that selection between two plausible reconstruction results does not significantly affect the assessed values of key bruise evolution parameters, i.e., hemoglobin mass diffusion and characteristic decomposition time.

TEM and XPS studies on CdS/CIGS interfaces

Copper indium gallium selenide (CIGS) was deposited by metallic precursors sputtering and subsequently submitted to a selenization process. The upper CdS layers were deposited by chemical bath deposition (CBD) technique. The CdS/CIGS interfaces were investigated by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). As checked by XPS analysis, the CIGS surface exhibited a hydroxide-terminated CdSe layer when treated with Cd Partial Electrolyte solution (Cd PE). Its thickness was roughly estimated to several nanometers. A 100nm thick CdS layer was deposited onto CIGS surface. The TEM images revealed a clear and sharp interface between CdS and CIGS. XPS analysis showed a CIGS surface covered by a pinhole free and homogeneous CdS layer. XPS depth profile measurement of the CdS/CIGS interface did not evidence elemental inter-diffusion between the CIGS and CdS layers, in very good agreement with TEM observations.

Analysis technique for ultra shallow junction using medium energy ion scattering time‐of‐flight elastic recoil detection analysis

An analysis technique for an ultra shallow junction in shrunk semiconductor devices was developed using medium energy ion scattering (MEIS) time‐of‐flight (TOF) elastic recoil detection analysis (ERDA). The energy of the recoiled and forward‐scattered ions was analyzed using a toroidal electrostatic analyzer with an energy resolution of less than 0.4 keV in MEIS‐ERDA. TOF was used for a mass separation in MEIS‐ERDA with high energy resolution, because an energy resolution of conventional ERDA with an absorber foil was degraded by the energy loss straggling on the foil. The probe beam of 100‐keV N+ was chopped by a function generator for the TOF measurement. Three standard samples of 2‐keV B+ implanted Si with doses of 0.5, 1.0, and 1.5 × 1016/cm2 were measured using MEIS‐TOF‐ERDA. The measured depth profile of the B+ implanted Si sample with a dose of 0.5 × 1016/cm2 was in good agreement with the simulated profile. The projected range and its straggling of 2‐keV B+ implantation into a Si substrate measured using MEIS‐TOF‐ERDA were 6.3 and 6.1 nm, respectively. The results indicated that an ultra shallow junction fabricated by low energy and light ion implantation can be analyzed using developed MEIS‐TOF‐ERDA. Copyright © 2014 John Wiley & Sons, Ltd.

Organic carbon inventories in natural and restored Ecuadorian mangrove forests.

Mangroves can capture and store organic carbon and their protection and therefore their restoration is a component of climate change mitigation. However, there are few empirical measurements of long-term carbon storage in mangroves or of how storage varies across environmental gradients. The context dependency of this process combined with geographically limited field sampling has made it difficult to generalize regional and global rates of mangrove carbon sequestration. This has in turn hampered the inclusion of sequestration by mangroves in carbon cycle models and in carbon offset markets. The purpose of this study was to estimate the relative carbon capture and storage potential in natural and restored mangrove forests. We measured depth profiles of soil organic carbon content in 72 cores collected from six sites (three natural, two restored, and one afforested) surrounding Muisne, Ecuador. Samples up to 1 m deep were analyzed for organic matter content using loss-on-ignition and values were converted to organic carbon content using an accepted ratio of 1.72 (g/g). Results suggest that average soil carbon storage is 0.055 ± 0.002 g cm−3 (11.3 ± 0.8% carbon content by dry mass, mean ± 1 SE) up to 1 m deep in natural sites, and 0.058 ± 0.002 g cm−3 (8.0 ± 0.3%) in restored sites. These estimates are concordant with published global averages. Evidence of equivalent carbon stocks in restored and afforested mangrove patches emphasizes the carbon sink potential for reestablished mangrove systems. We found no relationship between sediment carbon storage and aboveground biomass, forest structure, or within-patch location. Our results demonstrate the long-term carbon storage potential of natural mangroves, high effectiveness of mangrove restoration and afforestation, a lack of predictability in carbon storage strictly based on aboveground parameters, and the need to establish standardized protocol for quantifying mangrove sediment carbon stocks.

Influence of microscale turbulence on the phytoplankton of a temperate coastal embayment, Western Australia

We investigated the influence of microscale turbulence on the large phytoplankton of a coastal embayment in south-western Australia. Microstructure, physical and fluorometric depth-profiling field measurements and water sampling for nutrient, chlorophyll-a analyses and counting of the large size fraction of phytoplankton (microphytoplankton) were conducted in late-winter and late-spring of 2012. In both seasons we observed dominance of diatoms, low numbers of dinoflagellates, low nutrient concentrations, nitrogen limitation, clear waters and high turbulence intensities. In late-winter, total nitrogen, chlorophyll-a and diatom cell concentrations were higher than in late-spring, but dinoflagellates abundance did not change substantially. This indicated that the chain-forming diatom life-forms that dominated (Leptocylindrus, Chaetoceros and Skeletonema) were able to utilize the increased pulses of nitrogen in late-winter. The prevailing turbulence intensities observed, associated with the wind speed, were such that the Batchelor scale was smaller than the length of the diatom chains (100–300 μm), implying that these diatoms could experience microscale nutrient gradients. By contrast, the Kolmogorov velocity scales overwhelmed the motility abilities of the dinoflagellates observed, which in turn gain only little benefit from self propulsion at high turbulence. It is suggested that, nutrient storage allows diatoms surviving calm periods of low nutrient availability and formation of siliceous cell chains provide diatoms an advantage in accessing nutrients in turbulent coastal ecosystems.

Synergistic Effect of Triple Ion Beams on Radiation Damage in CLAM Steel

The synergistic effect of triple ion beams is investigated by simultaneous and sequential irradiations of gold, hydrogen and helium ions on the low activation martensitic steel (CLAM) developed in China. The depth profile measurements of the positron annihilation Doppler broadening S parameter are carried out as a function of slow-positron beam energy to examine the produced radiation damage. The synergistic effect of displacement damage and hydrogen and helium on the formation of radiation damage is clearly observed. In the preset case, this effect suppresses the radiation damage in the CLAM steel due to the helium and/or hydrogen filling of vacancy clusters.

In situ nuclear reaction analysis of D retention in undamaged and self-damaged tungsten under atomic D exposure

In situ deuterium depth profile measurements by nuclear reaction analysis (NRA) were performed on undamaged and neutron-like damaged W during D atom exposure at several sample temperatures. Damaged W was produced by high energy W-ion irradiation. In situ results of D retention after exposure termination are in good agreement with ex situ measurements for damaged W. In contrast, in situ NRA during D exposure on undamaged W showed significantly higher D retention than ex situ NRA measurement. It is also shown that this increased retention is lower at the location non-irradiated by the probing 3He beam. These observations indicate that the D retention is influenced by secondary damage produced by the probing 3He beam, however the dynamic retention could also partially contribute to the observed retention increase.

Surface-conductivity enhancement of PMMA by keV-energy metal-ion implantation

An experiment has been proposed to measure the neutron electric dipole moment (nEDM) with high precision at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source. One of the requirements of this experiment is the development of PMMA (Lucite) material with a sufficiently conductive surface to permit its use as a high-voltage electrode while immersed in liquid He. At the ORNL Multicharged Ion Research Facility, an R&D activity is under way to achieve suitable surface conductivity in poly-methyl methacrylate (PMMA) using metal ion implantation. The metal implantation is performed using an electron-cyclotron-resonance (ECR) ion source and a recently developed beam line deceleration module that is capable of providing high flux beams for implantation at energies as low as a few tens of eV. The latter is essential for reaching implantation fluences exceeding 1×1016cm−2, where typical percolation thresholds in polymers have been reported. In this contribution, we report results on initial implantation of Lucite by Ti and W beams with keV energies to average fluences in the range 0.5–6.2×1016cm−2. Initial measurements of surface-resistivity changes are reported as function of implantation fluence, energy, and sample temperature. We also report X-ray photoelectron spectroscopy (XPS) surface and depth profiling measurements of the ion implanted samples, to identify possible correlations between the near surface and depth resolved implanted W concentrations and the measured surface resistivities.

Ultra Thin SiN<sub>X</sub> on a-Si <i>In Situ</i> Hot-Wire CVD by Decomposing NH<sub>3</sub> Gas

The fabrication of ultra thin silicon nitride (SiNX) layer (< 2 nm) on amorphous silicon (a-Si) in-situ hot-wire CVD by decomposing ammonia (NH3) gas is reported. Approximately 1.5 nm thin SiNX is formed by nitridation of 40 nm thick a-Si for 10 min at substrate temperature of 250 °C. The amorphous phase of SiNX formed on a-Si and a-Si layer deposited on c-Si wafer is identified by Raman spectroscopy. The formation of ultra thin SiNX by nitridation of a-Si at 250 °C is confirmed by X-ray photoelectron spectroscopy (XPS) depth profile measurement of SiNX/a-Si structured film. The report indicates that the HWCVD method can be used for fabricating superlattice structures consisting of ultra thin SiNX layers (< 2 nm).

Diffusion of silver and iodine into polymers assisted by in situ electron irradiation

Diffusion of silver and iodine from aqueous solution into three synthetic polymers, HDPE, PI, and PEEK was studied. The samples, fully immersed in the respective chemical solution, were irradiated with 6.5MeV electrons at room temperature to fluencies from 1.0 to 5.0×1015cm−2. Concentration depth profiles of the diffused Ag and I atoms were determined by the RBS method. The content of the silver and iodine atoms was found to be a monotonously increasing function of the diffusion time, but it does not follow dependence expected for pure Fickian diffusion. The measured depth profiles exhibit a nearly exponential form and differ significantly from what is expected for the Fickian diffusion. Moreover, on silver depth profiles, two components are observed corresponding to particles with different mobilities. The anomalies are attributed to radiation defects created by electron irradiation, which are supposed to act as effective trapping centers for the diffusing particles. The depth profiles were simulated by a simple reaction-diffusion model and the parameters controlling the diffusion process were estimated. The diffusion coefficients under electron irradiation for both silver and iodine are higher by orders of magnitude than those reported for the common diffusion of metals in polymers.

Compositions and Magnetic Properties of CoO/Co/Ge(111) Films

On the top of Co/Ge(111) films, cobalt oxides are prepared by evaporating Co atoms in an oxygen atmosphere. Depth profiling measurements show a layered structure of a pure Co layer covered by a CoO overlayer. As the CoO thickness increases, the Auger intensity ratio of O KL2L2 and Co L3M45M45 Auger signals increases until reaching a saturated value which shows a CoO layer with a concentration ratio of Co and O close to 1:1. After introduction of CoO overlayers on Co/Ge(111), hysteresis occurs in the longitudinal configuration and CoO/Co/Ge(111) exhibits in-plane anisotropy. A slight reduction of the Kerr intensity occurs due to the oxidation of cobalt at the CoO/Co interface while an enhanced coercive force is observed owing to the imperfection introduced by oxygen to impede the magnetization reversal. Under conditions of cooling in a magnetic field, exchange bias field increases as the sample temperature decreases resulting from the formation of an antiferromagnetic/ferromagnetic interface.