Showing papers on "Deposition (chemistry) published in 1999"

Electroless metal deposition of electronic components in an enclosable vessel

Abstract: The present invention provides methods of electrolessly depositing metal onto the surfaces of electronic components (22) using an enclosable single vessel (20). The methods of the present invention include contacting the electronic components (22) with an activation solution followed by contacting the electronic components (22) with a metal deposition solution. In a preferred embodiment of the present invention, the oxygen levels in the activation solution and metal deposition solution are controlled in a manner for improved processing results. In another preferred embodiment of the present invention, the activation and metal deposition solutions are used one time without reuse.

Metal-organic atomic-layer deposition of titanium-silicon-nitride films

Abstract: Titanium–silicon–nitride films were grown by metal–organic atomic-layer deposition at 180 °C. When silane was supplied separately in the sequence of a tetrakis(dimethylamido) titanium pulse, silane pulse, and ammonia pulse, the Si content in the deposited films and the deposition thickness per cycle remained almost constant at 18 at. % and 0.22 nm/cycle, even though the silane partial pressure varied from 0.27 to 13.3 Pa. Especially, the Si content dependence is strikingly different from the conventional chemical-vapor deposition. The capacitance–voltage measurement revealed that the Ti–Si–N film prevents the diffusion of Cu up to 800 °C for 60 min. Step coverage was approximately 100% even on the 0.3 μm diam hole with slightly negative slope and 10:1 aspect ratio.

Global Simulation of Atmospheric Mercury Concentrations and Deposition Fluxes. Appendix Q

Abstract: Results from a numerical model of the global emissions, transport, chemistry, and deposition of mercury (Hg) in the atmosphere are presented. Hg (in the form of Hg(0) and Hg(II)) is emitted into the atmosphere from natural and anthropogenic sources (estimated to be 4000 and 2100 Mg yr−1, respectively). It is distributed between gaseous, aqueous and particulate phases. Removal of Hg from the atmosphere occurs via dry deposition and wet deposition, which are calculated by the model to be 3300 and 2800 Mg yr−1, respectively. Deposition on land surfaces accounts for 47% of total global deposition. The simulated Hg ambient surface concentrations and deposition fluxes to the Earth's surface are consistent with available observations. Observed spatial and seasonal trends are reproduced by the model, although larger spatial variations are observed in Hg(0) surface concentrations than are predicted by the model. The calculated atmospheric residence time of Hg is ∼1.7 years. Chemical transformations between Hg(0) and Hg(II) have a strong influence on Hg deposition patterns because Hg(II) is removed faster than Hg(0). Oxidation of Hg(0) to Hg(II) occurs primarily in the gas phase, whereas Hg(II) reduction to Hg(0) occurs solely in the aqueous phase. Our model results indicated that in the absence of the aqueous reactions the atmospheric residence time of Hg is reduced to 1.2 from 1.7 years and the Hg surface concentration is ∼25% lower because of the absence of the Hg(II) reduction pathway. This result suggests that aqueous chemistry is an essential component of the atmospheric cycling of Hg.

Airborne spreading and deposition of de-icing salt - a case study: reprint from the science of the total environment 235, 1999, pp. 161-168

Abstract: In this study it was concluded that between 20 and 63 percent of the de-icing salt applied on the road was transported by air and deposited on the ground 2-40 m from the road. The reason for the higher percentages is suggested to be intense snowfall, which leads to more splash generation and ploughing. Ninety percent or more of the total deposition occurs within 20 m at all transects. For all periods and both localities the deposition was greater on the east side of the road, which reflects the prevailing westerly winds in relation to the de-icing action occasions. (A)

Influences of water and substrate quality for periphyton in a montane stream affected by acid mine drainage

Abstract: St. Kevin Gulch, a headwater stream of the Rocky Mountains of Colorado, receives acid mine drainage that maintains low pH, high concentrations of heavy metals, and high rates of metal hydroxide deposition. An acidtolerant alga, Ulothrix sp., is present below the source of mine drainage in St. Kevin Gulch, but its biomass is limited by the deposition rates of iron hydroxides, which are especially high near the source. An experimental diversion of the mine drainage increased the quality of water and improved the substrate condition through a reduction of deposition rates. During the first year of the experiment, Ulothrix became abundant in this reach. During the second year, pH increased to the point at which aluminum hydroxides precipitated from the stream water onto the streambed; this change inhibited the growth of all periphyton, including Ulothrix. The deposition rate of aluminum hydroxides, however, was less than that of iron hydroxides in stream reaches with high Ulothrix biomass, suggesting that metal hydroxides vary by type in their effect on periphyton.

Deciduous conifers : High N deposition and O3 exposure effects on growth and biomass allocation in ponderosa pine

Abstract: Ponderosa pines (Pinus ponderosa Dougl. ex. Laws) 21 to 60 yr old were used to assess the relative importance of environmental stressors (O3, drought) versus an enhancer (N deposition) on foliar retention, components of aboveground growth, and whole tree biomass allocation. Sites were chosen across a well-described gradient in ozone exposure (40 to 80 ppb per h, 24 h basis, 6 month growing season) and nitrogen deposition (5 to 40 kg ha-1 yr-1) in the San Bernardino Mountains east of Los Angeles, California. A high level of chlorotic mottle indicated high O3 injury at sites closest to the pollution source, despite potential for the mitigating effects of N deposition. At the least polluted site, foliar biomass was evenly distributed across three of the five needle-age classes retained. At the most polluted site, 95% of the foliar biomass was found in the current year's growth. High N deposition and O3 exposure combined to shift biomass allocation in pine to that of a deciduous tree with one overwintering needle age class. Based on whole tree harvests, root biomass was lowest at sites with the highest pollution exposure, confirming previous chamber exposure and field studies. Aboveground growth responses in the high-pollution sites were opposite to those expected for O3 injury. Needle and lateral branch elongation growth, and measures of wood production increased with increasing proximity to the pollution source. An enhancement of these growth attributes suggested that N deposition dominated the ponderosa pine response despite high O3 exposure.

The order of calcium and phosphate ion deposition on chemically treated titanium surfaces soaked in aqueous solution.

Abstract: The mechanism of apatite deposition on chemically treated Ti surfaces still is being studied. In this study, simulated body fluid, calcium aqueous solution, phosphate aqueous solution, and accelerated calcification solution are used as media to investigate the order of calcium and phosphate ion deposition on chemically treated Ti surfaces. The results of inductively coupled plasma spectra, scanning electron microscopy, and energy dispersive X-ray analysis show that calcium deposition is the prerequisite for phosphate ion deposition.

Nitrogen deposition effects on carbon dioxide and methane emissions from temperate peatland soils

Abstract: Northern peatlands are important sources of carbon dioxide and methane emissions to the atmosphere. Increased atmospheric N deposition may have a significant impact on the emission of these greenhouse gases. We studied CO 2 and CH 4 emissions from untreated temperate peat soils from a eutrophic and a mesotrophic fen in a high N deposition area (the Netherlands) and from a mesotrophic fen in a low N deposition area (north-east Poland). In addition, we investigated the effects of N, P and glucose amendments on the emissions of CO 2 and CH 4 from these soils. Nitrogen availability (extractable NH 4 + ) in untreated peat from the high N area was 2.5-7.5 times higher than in the low N area, whereas the pH was 0.9-1.7 units lower. Using 6-week laboratory incubations of peat columns, we found that mean daily CO 2 emission from untreated peat soils from the high N area was lower than that from the low N area. Both linear and multiple regression analysis showed that CO 2 emission was positively related to soil pH (r 2 = 0.64). Additional N supply led to pH reduction and to lower CO 2 emission, especially in the low N peat soils. Thus, increased atmospheric N deposition leads, probably as a result of soil acidification, to lower CO 2 emission. Although glucose amendments resulted in increased CO, and CH 4 emission, we did not find evidence that this was caused by increased mineralization of native peat. Mean daily CH 4 -C emission was about 1-2 orders of magnitude lower than mean daily CO 2 -C emission. In the untreated peat soils from the high N eutrophic site, methane emission was higher than in the high N mesotrophic site and in the low N mesotrophic site. Linear regression analysis showed a positive relation between methane emission and soil fertility variables (r 2 =0.42-0.55), whereas a multiple regression model revealed that methane emission was determined by N-related soil chemistry variables (r 2 = 0.93). Increased nutrient supply initially resulted in higher methane emission from soils of both mesotrophic sites, but there was no effect on the high N eutrophic soil. These results show that increased atmospheric N deposition leads to increased methane emission from low-fertility peat soils. However, the ultimate effect of atmospheric N deposition on trace gas emissions and thereby on global warming is determined by the balance between the ratios of the change in CO 2 -C emission and CH 4 -C emission and the ratio of their global warming potentials (1:21).

Self-assembly ultrathin films based on diazoresins

Abstract: A monolayer ultrathin film of nitro-containing diazoresin (NDR) was fabricated on mica via a self-assembly technique. The adsorption of NDR on mica at different deposition times was monitored by de...

Magnesium Deposition and Dissolution Processes in Ethereal Grignard Salt Solutions Using Simultaneous EQCM‐EIS and In Situ FTIR Spectroscopy

Abstract: Magnesium deposition and dissolution processes in ethereal Grignard salt solutions using tetrahydrofuran as the solvent and Grignard salt which included , , and (R = methyl, ethyl, butyl, or benzyl) are reported. dissolution and deposition in these solutions are basically reversible with an overall mass balance close to zero for complete cycles. In prolonged deposition processes, the mass accumulated per mole of electron transferred was similar to , the equivalent weight of magnesium. However, deposition‐dissolution is not a simple two‐electron process, but involves adsorption‐desorption processes of species such as and/or . These adsorption processes lead the electrodes to devel p high impedance upon storage in these solutions (up to hundreds of thousands of ). However, this passivation is not stable, and breaks down as the electrochemical processes proceed. ©2000 The Electrochemical Society

Opposing effects of elevated CO 2 and N deposition on Lymantria monacha larvae feeding on spruce trees

Abstract: The effects of elevated atmospheric CO2 and increased wet N deposition on leaf quality and insect herbivory were evaluated in nine model ecosystems composed of 7-year-old spruce trees (Picea abies) and three understorey species established on natural forest soil. Each model ecosystem was grown in a simulated montane climate, and was exposed to one of three CO2 concentrations (280, 420, and 560 μl l−1), and to one of three levels of N deposition (0, 30, and 90 kg ha−1 year−1) for 3 years. In the 3rd year of the experiment second to third instars of the nun moth (Lymantria monacha) were allowed to feed directly on current-year needles of top canopy branches of each tree for 12 days. Specific leaf area (SLA), water content, and N concentration decreased in needles exposed to elevated CO2, whereas the concentrations of starch, condensed tannins, and total phenolics increased. Increased N deposition had no significant effect on SLA, and water content, but the concentrations of starch, condensed tannins, and total phenolics decreased, and sugar and N concentrations increased. Despite higher relative consumption rates (RCRs) larvae consumed 33% less N per unit larval biomass and per day at the two high CO2 treatments, compared to those feeding on 280 μl l−1-needles, but they maintained similar N accumulation rates due to increased N utilization efficiencies (NUE). However, over the 12-day experimental period larvae gained less N overall and reached a 35% lower biomass in the two high-CO2 treatments compared to those at 280 μl l−1. The effects of increased N deposition on needle quality and insect performance were generally opposite to those of CO2 enrichment, but were lower in magnitude. We conclude that altered needle quality in response to elevated CO2 will impair the growth and development of L. monacha larvae. Increasing N deposition may mitigate these effects, which could lead to altered insect herbivore distributions depending on regional patterns of N deposition.

Deposition of Diamond-Like Superhard Materials

Abstract: The material property hardness.- Diamond-like materials.- Growth mechanisms.- Nucleation mechanisms.

Resputtering during the growth of pulsed-laser-deposited metallic films in vacuum and in an ambient gas

Abstract: To determine the effective sputter yield during pulsed-laser deposition a method by measuring the deposition rate on tilted substrates is proposed. Under vacuum conditions, sputter yields of up to 0.17 and 0.55 were found at a laser fluence of 4.5 J/cm2 for Fe and Ag, respectively. These strong resputtering effects are induced by the large fraction of energetic ions occurring during deposition. With decreasing laser fluence or increasing Ar gas pressure, the sputter yields are reduced due to a decrease of the kinetic energy of the ions. For the deposition of stoichiometric films, an optimum Ar partial pressure of about 0.04 mbar exists, where the deposition rate is highest and the sputter yield is reduced.

Continuous measurements of CO and H2 deposition velocities onto an andisol: uptake control by soil moisture

Abstract: Carbon monoxide (CO) and hydrogen (H 2 ) net deposition velocities from the atmosphere onto soil and carbon dioxide (CO 2 ) effluxes to the atmosphere have been measured in an andisol field in Tsukuba, Japan by the open-flow chamber method. The deposition velocities of CO and H 2 were closely correlated ( R = 0.87), with a ratio of 1.55, which was attributed to the difference in molecular diffusivities. However, the deposition velocities did not exhibit a direct relationship with the CO 2 efflux. Deposition velocities of CO and H 2 ranged from 0.00 to 0.06 cm s −1 and from 0.00 to 0.10 cm s −1 , respectively, and were closely related to the level of the surface soil moisture (0–5 cm) and were higher in plowed plots than in compacted plots. CO deposition velocity was slightly lower in the daytime due to higher production rates affected by the soil temperature. These findings indicate that microbial CO and H 2 consumption was limited by transport resistance in the soil and that the in situ CO and H 2 uptake rates may be limited by a higher soil moisture level. CO and H 2 deposition was estimated to be restricted to the surface soil (possibly only the top 2–3 cm). CH 4 and CO 2 gas profiles were also related to the variation of the soil moisture level. DOI: 10.1034/j.1600-0889.1999.t01-2-00009.x

Tectono-sedimentary controls on Cretaceous black shale deposition along the opening Equatorial Atlantic Gateway (ODP Leg 159)

Abstract: Abstract The Cretaceous Equatorial Atlantic Gateway between the Central and South Atlantic basins is of interest not only for palaeoceanographic and palaeoclimatic studies, but also because it provided particularly favourable conditions for the accumulation and preservation of organic-rich sediments. Deposition of carbonaceous sediments along the Côte d’Ivoire-Ghana Transform Margin (Ocean Drilling Program Leg 159) was intimately linked to the plate tectonic and palaeoceanographic evolution of this gateway. Notably, the formation of a marginal basement ridge on the southeastern border of the transform margin provided an efficient shelter of the landward Deep Ivorian Basin against erosive and potentially oxidizing currents. Different subsidence histories across the transform margin were responsible for the development of distinct depositional settings on the crest and on both sides of the basement ridge. Whereas the southern, oceanward flank of the basement ridge was characterized by rapid, continuous deepening since the latest Albian-early Cenomanian, marine sedimentation on the northern, landward flank was interrupted by a period of uplift and erosion in the late Albian, and rapid subsidence started after the early Coniacian. Organic-rich sediments occur throughout almost the entire Cretaceous section, but hydrogen-rich marine black shales were exclusively recovered from core sections above an uplift-related unconformity. These black shales formed when separation of Africa and South America was sufficient to allow permanent oceanic midwater exchange after the late Albian. Four periods of black shale accumulation are recorded, some of them are correlated with the global oceanic anoxic events: in the latest Albian-earliest Cenomanian, at the Cenomanian-Turonian boundary, during the middle Coniacian-early Campanian, and in the mid-Maastrichtian. These periods were characterized by increased carbon fluxes to the seafloor, induced by enhanced palaeoproductivity and intensified supply of terrestrial organic matter. Black shale deposition appears to be intimately linked to periods of rising or maximum eustatic sea level and to the expansion of the oxygen minimum zone, as indicated by foraminiferal biofacies. Intervals between black shale units, in contrast, indicate a shrinking oxygen minimum zone and enhanced detrital flux rates, probably related to lowering sea level. Upper Cretaceous detrital limestones with high porosities may provide excellent hydrocarbon reservoirs, although their areal extent appears to be limited. Palaeogene porcellanites, capped by Neogene pelagic marls and clays, extend over a wider area and may provide another target for hydrocarbon exploration.

Electrochemical Nanostructuring of n‐Si(111) Single‐Crystal Faces

Abstract: The local formation and dissolution of low-dimensional phases and small clusters on foreign substrates plays an important role in modern nanotechnology. This paper deals with the current state of nanostructuring of semiconductor surfaces by localized electrochemical metal deposition using in situ scanning tunneling microscopy as a nano-tool. New experimental results of delocalized and localized electrochemical deposition and dissolution of Pb on n-type Si(111) single-crystal surfaces are presented. The influence of surface inhomogeneities on the local metal deposition process is considered.

The initial stages of copper deposition on bare and chemically modified gold electrodes

Abstract: This paper comprises, in the form of an overview, various aspects of the initial stages of electrolytic metal deposition, demonstrated and exemplified by the classical model system, Cu on Au(hkl). Describing underpotential as well as overpotential deposition, some of the parameters governing nucleation and growth are pointed out. The profound effect of substrate orientation is shown and various examples of the influence of organic additives on the deposition process are given. Most recently, metal deposition onto electrodes covered with self-assembled monolayers has received increased attention as a possible model system for metal deposition onto a non-conducting stirface and therefore, preliminary results for Cu deposition on alkanethiol covered Au(111) are presented.

Nitrogen Deposition In and Around an Intensive Agricultural District in Central New York

Abstract: Emissions of NH 3 from intensive agriculture may perturb natural ecosystems by increasing atmospheric N deposition. This study was undertaken to quantify patterns of atmospheric chemistry and N deposition in and around a highly intensive agricultural district and thereby to improve understanding of the fate of NH 3 emissions and possible effects on regional forests. Atmospheric chemistry, wet and bulk deposition, canopy throughfall, and soil and vegetation N status were measured at a suite of sites in and around the agricultural district centered in southern Cayuga County, New York. Concentrations of NH + 4 and acidic gases and particulates were slightly elevated compared with regional background values. Temporal variations in these species were consistent throughout the district and surrounding areas, suggesting wide dispersion. In contrast, NH 3 concentrations were greatly elevated within the district (often >1 μg m -3 ), comparable to values in southeastern Netherlands, but declined to moderate values in outlying areas (0.2 μg m -3 ). Bulk deposition of NH + 4 near large farms (7-8 kg NH 4 -N ha -1 yr -1 ) was over twice as high as the regional background, dedining to levels about 50% above background throughout the district but more than 2 km away from large farms (4-5 kg NH 4 -N ha -1 yr -1 ). These values must be regarded as tentative estimates because of probable high seasonal and annual variation and the limited intervals of sampling in the current study. Also, gaseous deposition of NH 3 to forests in the district probably contributes significantly to total deposition, but its magnitude remains uncertain.