Microprobe Secondary Ion Mass Spectrometry Research Articles

Tissue specific localization of pectin-Ca²⁺ cross-linkages and pectin methyl-esterification during fruit ripening in tomato (Solanum lycopersicum).

Fruit ripening is one of the developmental processes accompanying seed development. The tomato is a well-known model for studying fruit ripening and development, and the disassembly of primary cell walls and the middle lamella, such as through pectin de-methylesterified by pectin methylesterase (PE) and depolymerization by polygalacturonase (PG), is generally accepted to be one of the major changes that occur during ripening. Although many reports of the changes in pectin during tomato fruit ripening are focused on the relation to softening of the pericarp or the Blossom-end rot by calcium (Ca2+) deficiency disorder, the changes in pectin structure and localization in each tissues during tomato fruit ripening is not well known. In this study, to elucidate the tissue-specific role of pectin during fruit development and ripening, we examined gene expression, the enzymatic activities involved in pectin synthesis and depolymerisation in fruit using biochemical and immunohistochemical analyses, and uronic acids and calcium (Ca)-bound pectin were determined by secondary ion-microprobe mass spectrometry. These results show that changes in pectin properties during fruit development and ripening have tissue-specific patterns. In particular, differential control of pectin methyl-esterification occurs in each tissue. Variations in the cell walls of the pericarp are quite different from that of locular tissues. The Ca-binding pectin and hairy pectin in skin cell layers are important for intercellular and tissue–tissue adhesion. Maintenance of the globular form and softening of tomato fruit may be regulated by the arrangement of pectin structures in each tissue.

Effects of Antimony Doping in Polycrystalline CdTe Thin-Film Solar Cells

The effects of antimony (Sb) doping of the CdTe layer in the CdTe solar cells were investigated using Sb-doped CdTe powders as source materials for CdTe deposition by the close-spaced sublimation (CSS) method. Conversion efficiency increased with increasing Sb concentration below 1×1018 cm-3, mainly owing to the improvement of the fill factor. Secondary ion microprobe mass spectrometry (SIMS) depth profile revealed that the Sb impurities at a concentration of approximately 1×1016 cm-3 were incorporated into the CdTe layer when using the Sb-doped CdTe source of 1×1018 cm-3. The observation of surface morphology showed that the grain sizes were improved by Sb addition. Therefore, the improved performance upon Sb addition to CdTe solar cells was probably due to the improvements in crystallinity, such as increased grain size.

Structural Analysis on Iron-Based Superconductor Pr1111 System with Oxygen Deficiency and Flourine Substitution

We have performed structural analyses on iron-based superconductors, PrFeAsO$_{1-y}$ and PrFeAsO$_{1-x}$F$_x$, systematically, by means of Rietveld method on neutron powder diffraction data. The shifts of iron ion valence from +2, $\delta$, are accurately determined from the occupancies of O and O$_{1-x}$F$_x$ sites obtained by the Rietveld analysis and F-concentration obtained by secondary ion-microprobe mass spectrometry. $T_\textrm{c}$-$\delta$ curve of PrFeAsO$_{1-y}$ is different from the curve of PrFeAsO$_{1-x}$F$_x$, indicating that $\delta$ is not a principal parameter for $T_\textrm{c}$ in so-called 1111 system. Structural parameters of the FeAs layers, for example, As-Fe-As bond angle and As-height from Fe layer, are different between both systems with similar $\delta$-values. Their parent compounds are also found to have different structural parameters, possibly due to the different synthetic conditions. These results suggest that the difference of structural parameters of FeAs layer is the origin of the discrepancy of $T_\textrm{c}$-$\delta$ curves of both systems and the $T_\textrm{c}$-value in the 1111 system is sensitive to the structural parameters. It may be attribute to an energy balance of the conducting bands contributing to the superconductivity.

NH3 Plasma Interface Modification for Silicon Surface Passivation at Very Low Temperature

The effect of passivation layers (SiOX, SiNX, etc.) using plasma-enhanced chemical vapor deposition (PECVD) for crystalline silicon solar cells showed high surface recombination with decreasing of deposition temperature (<300 °C). The surface of Czochralski (Cz) monocrystalline silicon (c-Si) wafer was exposed to an NH3 plasma before the low-temperature deposition of silicon nitride (SiNX) layer or amorphous silicon (a-Si:H) layer in a system respectively. The effect of NH3 plasma treatment for the interface was observed by microwave photoconductance decay (µ-PCD), quasi-steady-state photoconductance (QSSPC), Fourier transform infrared spectroscopy (FT-IR), secondary ion-microprobe mass spectrometry (SIMS), and X-ray photoemission spectroscopy (XPS). The effective lifetime (τeff) with NH3 plasma treatment exceeded τeff without the treatment. Even in the case of very low deposition temperature (100 °C), τeff is improved dramatically (about 38 times). This NH3 plasma treatment effect was caused by hydrogenation and carbon cleaning from the SIMS measurement. It was found that SiNX films with excellent surface passivation properties can be deposited at 100 °C.

Metal–Organic Vapor Phase Epitaxy of GaN and InGaN Using Triethylamine with Ammonia as a Nitrogen Source

Metal–organic vapor phase epitaxy (MOVPE) of GaN and InGaN was investigated using a combination of triethylamine (TEA) and ammonia (NH3) as the nitrogen source. The reaction of TEA and NH3 in the gas phase was verified by quadrupole mass spectrometry. By using this nitrogen source, a GaN epitaxial layer was grown at 600 °C with a peak photoluminescence at 375 nm. An InxGa1-xN (x=0.6) eptaxial layer was also grown at 600 °C. The indium to gallium concentration ratio was verified by secondary ion-microprobe mass spectrometry (SIMS) and X-ray diffraction. It is confirmed that this is an effective nitride source for the efficient growth of GaN and InGaN.

Determination of the spatial distribution of trace elements in stainless steel by imaging microprobe secondary ion mass spectrometry

Imaging microprobe secondary ion mass spectrometry (SIMS) using a liquid metal ion source (LMIS) has been used to determine the spatial distribution of metal ions in stainless steel. This scanning ion microprobe is used to achieve high resolution chemical maps of the surface of a sample. For conductive samples such as stainless steel, the practical spatial resolution approaches 0.2 μm and the sensitivity varies with the ion of interest. We have obtained important information relating to the distribution of surface contaminants, segregation, and corrosion phenomena of the elements in these alloys. In this report we hope to demonstrate the usefulness of this important new technique by describing its capabilities and by reviewing data obtained from two separate studies involving stainless steel. Significant findings obtained in these mapping experiments were: • . Stainless steel 316 tubing, which had been found previously to be catalytically active, showed remarkable differences between the used and unused samples. Sodium, potassium, and hydrocarbons were found to exist in agglomerations (islands) in the unused tubing, but were very well distributed in the used tubing. • . A used stainless steel impeller was found to be inhomogeneous with respect to iron and chromium. The surface was entirely covered by chlorine, which is believed to be responsible for the corrosion. Water and elevated levels of chloride ion were found inside numerous scratches or fissures covering the surface. The unused stainless steel showed no signs of streaks or segregated metal regions, and was free from fissures.

Characterization of organic monolayers on individual microparticles using microprobe mass spectrometry

Polycyclic organic matter (POM) represents a class of compounds of environmental significance. Many of these compounds have been shown to exhibit mutagenic characteristics. POM is formed during the combustion of fossil fuels such as coal. Emitted particulate matter such as coal flyash contains surface associated POM that undergoes chemical transformations due to photolysis and exposure to gaseous pollutants. Past studies of these compounds on flyash have relied on wet chemical techniques in which POM is extracted from large quantities of flyash and then analyzed by chromatography. This technique is hindered by several problems such as the extensive heterogeneity in flyash composition. Individual flyash particles of different composition will influence POM adsorption and reactivity. Studies of the different types of particles by the wet techniques require that the particles be physically separated (density, size, magnetic properties). Microprobe secondary ion mass spectrometry (SIMS) is a technique that can potentially overcome these obstacles by permitting the in situ analysis of POM on single particle surfaces.

Secondary neutral mass spectrometry using a gallium ion probe

AbstractAn electron beam pos‐ionization cell has been fitted to the input optics of the quadrupole mass spectrometer of a gallium microprobe secondary ion mass spectrometry (SIMS) instrument. The use of gallium as the primary beam for secondary neutral mass spectrometry (SNMS) has been evaluated. Although much higher probe currents are required for SNMS than for SIMS, no problems have been encountered from gallium retained in the sample. Examples of quantitative analysis of insulating samples and of depth profiles are given.

Lead and sulfur isotope microstratigraphy in galena crystals from mississippi valley-type deposits

The development of an analytical procedure for lead and sulfur isotope analysis by secondary ion microprobe mass spectrometry allowed us to provide in situ isotopic microanalyses of galena crystals.We performed analyses across the growth zones of two crystals of galena from Mississippi Valley-type ore deposits, with a spatial resolution of 50 mu m and a spacing of 250 mu m. These analyses show frequent variations for both lead and sulfur isotope compositions which occurred during the time of the crystal growth. We can demonstrate that, for both elements, these variations involved changes in the sources of the brines which formed the ore deposits. The comparison of lead and sulfur isotope behavior suggests that for the Picher deposit lead and sulfur originated from common sources, whereas for the Buick mine deposit lead and sulfur had separate sources.The two galenas exhibit rapid and frequent changes in isotopic composition; this suggests numerous and discontinuous inputs of lead and sulfur to the ore deposits. This model agrees well with a physical model for Mississippi Valley-type deposits proposed by Cathles and Smith (1983). The isotopically different sources were probably different sedimentary layers and perhaps basement rocks in the same basin, whose formation waters were channeled in preferred water conduits to the ore deposit location during the subsidence of the basin, allowing mixing between the different sources to occur during the brines' travel.