Increasing Formation Temperature Research Articles

Formation temperature of microcrystalline dolomite in oil-rich black shale: Implications for hydrocarbon accumulation in a volcanic-lacustrine rift basin

Lacustrine microcrystalline dolostones in the ancient records have been commonly interpreted as of an evaporitic origin, on the basis of their numerous occurrences in modern evaporative shallow lakes. This interpretation obscures the forming mechanisms of dolostones formed in a deep lacustrine setting, where dolostones interbedded with shale become a focus of hydrocarbon source rocks in recent years. In this study, an alternative non-evaporitic origin of dolomite is interpreted for a Permian lacustrine laminated dolostone. The dolostones are thinly intercalated with tuffaceous shales and composed mainly of volumetrically abundant, low-ordered, subhedral to euhedral, microcrystalline dolomites with a variable amount of pyroclastics. Evidence for evaporation (e.g., the presence of halite, gypsum and shrinkage cracks) and typical methanogenic microfossils is absent. Instead, our dolostones are unevenly and locally distributed as thin beds or lenses and intercalated with tuffaceous shale and have a formation temperature ranging from 31.4 to 73.8 °C, as estimated from dolomite clumped oxygen? isotope thermometry. In addition, the dolostones have a87Sr/86Sr ratio similar to that of the mantle (0.705154 on average) and extremely negative δ18O (−2.9‰ to −24‰) and positive δ13C (5.1‰–10.8‰) values. A lateral trend of increasing formation temperature of the dolostone toward the volcanic center correlates with the trends of: 1) an increasing amount of pyroclastics, euhedral dolomite crystals, Fe, and TOC, and an increasingly positive δEu value, and 2) decreasing values of 87Sr/86Sr and δ18O. The correlation suggests that a local temperature increase and frequent elemental (Fe and Mg) cycling between the conditions of dolomite supersaturation and undersaturation, which are controlled by episodic volcanic-hydrothermal activities are the causes for dolomite nucleation and growth, resulting in the formation of massive dolostone during deposition and shallow burial. The process also affected organic matter accumulation and local transformation to immature or early mature hydrocarbon during deposition and early burial. The results establish a volcanism-controlled temperature range for primary dolomite nucleation and growth, as well as hydrocarbon generation in a deep lake environment during the period of deposition and early burial, and provide insights on shale oil exploration in petroliferous rift basins.

The Effects of Temperature and Fluoroethylene Carbonate Concentration on the Formation of the Graphite SEI and Its Impact on the Full-Cell Performance

Extending the cycle-life of state-of-the-art lithium-ion batteries (LiBs) is, amongst other aspects, predicated on optimizing the properties of the solid electrolyte interphase (SEI), such as its stability and resistance.[1] It is formed at the negative electrode during the first cycles by electrolyte decomposition and acts as a passivating layer between the electrode surface and the electrolyte.[2,3] Since the SEI formation is accompanied by an irreversible loss of cyclable lithium, its stability during cycling is crucial for improving the charge/discharge efficiency of LiBs. Furthermore, the arising resistance associated with the SEI formation, predominantly depending on the SEI thickness, its chemical composition, and its lithium-ion conductivity, all impact the rate performance of the anode.[4] Two of the most crucial factors impacting SEI formation are temperature and electrolyte composition (i.e., using electrolyte additives).[5] Additives are added to the electrolyte to inhibit the predominant reduction of other electrolyte constituents and thereby form an SEI with improved stability during cycling.[1,6,7] One of the most prominent additives for LiBs is fluoroethylene carbonate (FEC), which is preferentially reduced compared to common carbonate solvents (e.g., ethylene carbonate, ethyl methyl carbonate) due to its higher reduction potential.[7] In this study, we investigated the influence of the formation temperature between 10 and 60 °C, as well as the concentration of FEC (2 and 20 %wt in EC:EMC 3:7 wt/wt with 1 M LiPF6, Gotion, USA) on the characteristics of a synthetic graphite (SMG-A5, Resonac, Japan) anode, both in SMG/Li half-cells and in Ni-rich NCM/SMG full cells.We quantified the first-cycle irreversible capacity loss (ICL) in SMG/Li half cells with a lithium reference electrode after two 0.1 C formation cycles and compared the FEC containing electrolytes to the baseline- (LP-57) and an LP-572 (1 M LiPF6 in EC:EMC 3:7 wt/wt + 2 %wt vinylene carbonate (VC), Gotion, USA) electrolyte. Employing electrochemical impedance spectroscopy in an SMG/Li half-cell setup with a µ-reference electrode and a free-standing graphite electrode,[8,9] we could further quantify the intercalation resistance (R Int, representing the sum of the charge-transfer and the SEI resistance) after an identical formation protocol at 40 % SOC. Both quantities, the ICL and R Int, increase with increasing formation temperature and higher FEC content.The impact of an increasing R Int on the rate performance was tested in Ni-rich NCM/SMG full cells with a lithium reference electrode, revealing a decreased rate capability and higher susceptibility for lithium plating for cells that were formed at higher temperatures and contained 20 %wt FEC. Additionally, the cycling stability of Ni-rich NCM/SMG full cells at 25 °C was assessed in coin cells. Despite an increased ICL and R Int after formation, cells that were formed at elevated temperatures and contained 20 %wt FEC showed enhanced cycling stability compared to those that were formed at a lower temperature and contained less FEC.Finally, on-line electrochemical mass spectrometry (OEMS) was employed to quantify the evolved gases during the formation of a Ni-rich NCM/SMG full cell containing either of the FEC-containing electrolytes at different temperatures. In accordance with an increased ICL and R Int, a higher formation temperature, as well as a higher FEC content, gave rise to a more pronounced gas evolution during formation.

Numerical simulation and thermo-hydro-mechanical coupling model of in situ mining of low-mature organic-rich shale by convection heating

The in situ efficient exploitation of low-mature organic-rich shale resources is critical for alleviating the current oil shortage. Convection heating is the most critical and feasible method for in situ retortion of shale. In this study, a thermo-hydro-mechanical coupling mathematical model for in situ exploitation of shale by convection heating is developed. The dynamic distribution of the temperature, seepage, and stress fields during the in situ heat injection of shale and the coupling effect between multiple physical fields are studied. When the operation time increases from 1 to 2.5 years, the temperature of most shale formations between heat injection and production wells increases significantly (from less than 400 to 500 °C), which is a period of significant production of shale oil and pyrolysis gas. The fluid pore pressure gradually decreases from the peak point of the heat injection well to the surrounding. Compared with shale formation, bedrock permeability is poor, pore pressure increases slowly, and a lag phenomenon exists. The pore pressure difference between bedrock and shale is minimal by 1 year. When the heat injection time is 2.5 years, the permeability coefficient of shale formation in the area from the heat injection well to the production wells increases nearly 100 times the initial permeability coefficient. With increasing formation temperature, the vertical stress gradually evolves from compressive stress to tensile stress. Meanwhile, the action area of tensile stress expands outward with time with the heat injection well as the center. In general, increasing tensile stress enlarges the pore volume. It extends the fracture width, creating favorable conditions for the injection of high-temperature fluids and the production of oil and gas. Cited as: Zhao, J., Wang, L., Liu, S., Kang, Z., Yang, D., Zhao, Y. Numerical simulation and thermo-hydro-mechanical coupling model of in situ mining of low-mature organic-rich shale by convection heating. Advances in Geo-Energy Research, 2022, 6(6): 502-514. https://doi.org/10.46690/ager.2022.06.07

Microfabrics, in-situ trace element and sulfur isotope compositions of pyrite from the Jinjiwo copper deposit in Chengmenshan orefield, northern Yangtze Block: Syngenetic stratabound mineralization and hydrothermal remobilization

The Jinjiwo copper deposit is located in the Jiurui ore district of the Middle-Lower Yangtze Metallogenic Belt. The deposit has stratiform orebodies hosted by Late Carboniferous carbonate units. Pyrite is the dominant metallic mineral in the ores. Here we report on an integrated study on the microfabrics, Raman spectroscopy, in-situ LA-(MC-)ICP-MS trace element and sulfur isotope of pyrite, with a view to understand the geochemical variation, genesis of copper mineralization and ore-forming process. Textural observations suggested four types of pyrite corresponding to three metallogenic episodes: syngenetic sedimentation (PyI), metamorphism or deformation (PyII), and skarn-hydrothermal mineralization including the late skarn stage (PyIII) and hydrothermal stage (PyIV). Raman spectra of pyrite reveal subtle differences in band position and widths (FWHM) and display the increasing formation temperature of from PyI, through PyIV and PyIII, to PyII. Colloform and laminated pyrite (PyI) share similarities in behavior of pairs of elements and have low Co/Ni ratios, and the former contains the highest concentrations of Bi, Cu, Pb, Zn, Ag, Au, Mn that suggest rapid precipitation from highly saturated fluids. PyII shows high Co, Ni and As concentrations and Co/Ni ratios of 0.03 to 6.19. PyIII and PyIV have greatly varying Co/Ni ratios of 1.07 to 29 and typically low Au concentrations, suggesting a hydrothermal source. PyIII is rich in Co and Se, but is depleted in As, Cu, Pb, Zn, Ag, and Au in comparison with PyIV. There are two kinds of sulfur: one is that δ34S values are near zero, suggesting that the pyrite sulfur in the ores was derived from a mixed source in deep crust, and the other is that δ34S values are less than −39.1‰, indicating the sedimentary pyrite sulfur was originated from bacterial sulfate reduction. The combined textural and compositional data of pyrite suggest that the formation of the Jinjiwo copper deposit might have recorded the submarine exhalation sedimentation and the Mesozoic tectonic transition-deformation and hydrothermal overprint.

In the Trenches of the Solar–Stellar Connection. I. Ultraviolet and X-Ray Flux–Flux Correlations across the Activity Cycles of the Sun and Alpha Centauri AB

Abstract This study focuses on high-energy proxies of stellar magnetic activity over long-term starspot cycles of three low-activity Sun-like stars: α Centauri A (HD 128620: G2 V), α Cen B (HD 128621: K1 V), and the Sun itself. Data sets include: daily solar ultraviolet irradiance spectra and X-ray fluxes from the Solar Radiation and Climate Experiment, during recent sunspot Cycles 23 and 24; Interface Region Imaging Spectrograph long-slit stigmatic imaging of solar Mg ii h (2803 Å) and k (2796 Å) in quiet and active regions; and Hubble Space Telescope Imaging Spectrograph ultraviolet, and Chandra X-ray, campaigns on α Cen AB. Established stellar “flux–flux” relations, for example X-rays (T ∼ 1 MK) versus Mg ii (T ∼ 8000 K), showed increasing power-law slopes with increasing formation temperature, but these give way on the Sun to bent power laws, and surprising inversions in the activity hierarchy: Si iii is more “active” (steeper power laws) than N v, despite the latter’s four times higher formation temperature. The Sun’s flux–flux behavior, nevertheless, remarkably parallels its low-activity solar twin α Cen A. In contrast, the cooler, somewhat more active, K dwarf companion displays correlations more in line with the previous stellar paradigm. The new flux–flux relations offer a way to vet numerical spectral simulations and proxy-based irradiance models, and extrapolate solar global activity indices into regimes below or above the grasp of contemporary records, or to exoplanet hosts at the low end of the Sun-like activity ladder.

Decomposition prevention through thermal sensitivity of hydrate formations around wellbore

The traditional drilling engineering research on wellbore stability of hydrate formation neglects the interactions between heat transfer and mass transfer, a new multi-field coupling model is established to study the effects, and this model considers hydrate kinetic decomposition rate in different salinities, two-phase flows and heat transfer in pores. The calculation results show most of engineering parameters affects hydrate decomposition through high thermal sensitivity of hydrate formations: The direction and value of seepage will change the temperature field and the position of hydrate dissociation front. High bottomhole pressure will bring in the radial seepage, increasing formation temperature and exacerbating hydrate decomposition. The latent heat of hydrate dissociation reduces temperature growth in the entire formation, inhibits the decomposition front advancement and decreases the decomposition rate. Reducing the bottomhole temperature can get an incremental margin for wellbore stability. High salinity in drilling fluid will provide negative impact under high bottomhole pressure and high permeability. These results show the protection of hydrate formations should avoid increasing the density of drilling fluid and focus on cooling drilling fluid and reducing drilling time.

Analytical solution for three-dimensional radial heat transfer in a cold-region tunnel

The study of the temperature field of cold-region tunnels is fundamental for preventing frost heave. At present, considerable knowledge has been obtained by numerical simulation and physical experimentation. In this paper a computational model for three-dimensional radial heat transfer was established according to some reasonable assumptions, and the complex boundary conditions inside the tunnel surface including axial coordinate z and time t were obtained based on the analysis of the field temperature monitoring data. The z and t terms in the boundary were split to simplify the problem. Laplace and Fourier integral transformation methods were combined to solve this problem, and the Den Iseger method was adopted to solve the Laplace inverse transformation. Yuximolegai tunnel was introduced to study its temperature distribution. The freezing length in z direction is reduced from 143 m to 70 m and the maximum radial freezing depth at the entrance is also shortened from 4.7 m to 2.4 m due to 5 cm insulation layer, which reveals that the effect of 5 cm insulation layer was remarkable. Considering the efficiency of insulation layer, it needs to be combined with other measures to prevent frost damage of surrounding rock. The analysis of convective heat transfer coefficient, formation temperature, and thickness of the insulation layer was performed to obtain their influence on the lining temperature. The results show that the influence of the convection heat transfer coefficient is small. The effect of the insulation layer improves with increasing formation temperature and worsens as the thickness of the insulation layer increases. These achievements can enrich the research of temperature fields of tunnels in cold regions and are significant for guiding tunnel design in cold regions.

Pore scale characteristics of gas flow in shale matrix determined by the regularized lattice Boltzmann method

The flow mechanism of natural gas in the shale matrix is closely related to the high efficient development of shale gas reservoirs. However, the flow characteristic of shale gas in nanometer pores is scale dependent, and is also affected by the formation condition, adsorption layer, residual water saturation and detailed pore structure. In this study, a lattice Boltzmann model with a regularization procedure was applied to simulate shale gas flow in a 2D porous medium, and the effects of slippage, adsorption layer, residual water saturation and surface area on the apparent permeability were discussed. Simulation results indicate that the apparent permeability decreases with the increasing formation pressure, and increases with the increasing formation temperature and characteristic pore size. The adsorption layer and residual water affect the apparent permeability by changing the effective pore space for gas flow. And the effect is more obvious under the large Knudsen number conditions. When the porosity of the porous media is constant, the apparent permeability decreases with the increasing surface area, and the large surface area would even offset the positive effect of slippage on the apparent permeability.

An aspect of bitumen emulsification by steam condensation: Effect of formation temperature and bitumen content

ABSTRACTThe experiments to form emulsions of bitumen including fine droplets of condensate water were carried out for an average formation temperature range; Tf = 38–69°C and bitumen content; CB = 29–82%. It was observed that the water retention capacity or stability of the emulsions after mild agitation was significantly affected by formation temperature and content of the bitumen. The particle size of water droplets in emulsion decreased with increasing formation temperature. However, bitumen emulsions showed similar shear thinning non-Newtonian behavior in spite of the formation temperature, since water droplets in the emulsions changed under shear flow to smaller size similar to ones formed at the higher formation temperature.

Alteration mineralogy, lithochemistry and stable isotope geochemistry of the Murgul (Artvin, NE Turkey) volcanic hosted massive sulfide deposit: Implications for the alteration age and ore forming fluids

The Murgul (Artvin, NE Turkey) massive sulfide deposit is hosted dominantly by Late Cretaceous calc-alkaline to transitional felsic volcanics. The footwall rocks are represented by dacitic flows and pyroclastics, whereas the hanging wall rocks consist of epiclastic rocks, chemical exhalative rocks, gypsum-bearing vitric tuff, purple vitric tuff and dacitic flows. Multi-element variation diagrams of the hanging wall and footwall rocks exhibit similar patterns with considerable enrichment in K, Rb and Ba and depletion in Nb, Sr, Ti and P. The chondrite-normalized rare earth element (REEs) patterns of all the rocks are characterized by pronounced positive/negative Eu anomalies as a result of different degrees of hydrothermal alteration and the semi-protected effects of plagioclase fractionation.Mineralogical results suggest illite, illite/smectite+chlorite±kaolinite and chlorite in the footwall rocks and illite±smectite±kaolinite and chlorite±illite in the hanging wall rocks. Overall, the alteration pattern is represented by silica, sericite, chlorite and chlorite–carbonate–epidote–sericite and quartz/albite zones. Increments of Ishikawa alteration indexes, resulting from gains in K2O and losses in Na2O and the chlorite–carbonate–pyrite index towards to the center of the stringer zone, indicate the inner parts of the alteration zones. Calculations of the changes in the chemical mass imply a general volume increase in the footwall rocks. Abnormal volume increases are explained by silica and iron enrichments and a total depletion of alkalis in silica zone. Relative K increments are linked to the sericitization of plagioclase and glass shards and the formation of illite/smectite in the sericite zone. In addition, Fe enrichment is always met by pyrite formation accompanied by quartz and chlorite. Illite is favored over chlorite, smectite and kaolinite in the central part of the ore body due to the increase in the (Al+K)/(Na+Ca) ratio. Although the REEs were enriched in the silicification zone, light REEs show depletion in the silicification zone and enrichment in the other zones in contrast to the heavy REEs' behavior. Hydrothermal alteration within the hanging wall rocks, apart from the gypsum-bearing vitric tuffs, is primarily controlled by chloritization with proportional Fe and Mg enrichments and sericitization.The δ18O and δD values of clay minerals systematically change with increasing formation temperature from 6.6 to 8.7‰ and −42 to −50‰ for illites, and 8.6 and −52‰ for chlorite, respectively. The O- and H-stable isotopic data imply that hydrothermal-alteration processes occurred at 253–332°C for illites and 136°C for chlorite with a temperature decrease outward from the center of the deposit. The positive δ34S values (20.3 to 20.4‰) for gypsum suggest contributions from seawater sulfate reduced by Fe-oxide/-hydroxide phases within altered volcanic units. Thus, the hydrothermal alteration possibly formed via a dissolution–precipitation mechanism that operated under acidic conditions. The K–Ar dating (73–62Ma) of the illites indicates an illitization process from the Maastrichtian to Early Danian period.

Laboratory Experimental Research on Promoting Aquathermolysis of Heavy Oil with the NaNO<sub>2</sub>/NH<sub>4</sub>Cl Exothermic System

Concerning the fact that the in-situ aquathermolysis reaction of heavy oil is affected by the limit of formation temperature, a simulated experiment is made by means of thermochemistry on promoting the aquathermolysis reaction of heavy oil through increasing formation temperature via in-situ heat generation. The results show that after the injection of 5mL concentration of 5mol/L NaNO2/NH4Cl exothermic system to the reaction kettle, the reactor temperature rises from 200°C to over 240°C, increasing the pressure almost by 0.4MPa. After the reaction, the viscosity reduction ratio of the heavy oil decreases by about 40%, with saturated hydrocarbons and aromatic content increased significantly, but resin and asphaltene content significantly obviously lowered, which proves that thermochemincal heat generation can promote the aquathermolysis reaction of heavy oils. The analysis also shows that the field injection process through the thermochemical system is feasible, that the exothermic reaction speed and the thermal peak position are controllable and that no formation damage is done. Besides, it also proves the feasibility of promoting the aquathermolysis viscosity reduction of heavy oil through increasing temperature by thermochemical heat generation. In specific application, an in-depth analysis of the factors that affect the thermochemical temperature increase should be made and the relevant parameters of the operation should be optimized.

Formation of Porous Aluminum Solidified by Chemical Reaction of Pure Aluminum Powder and Pure Water

Porous materials have attracted attention because they exhibit a wide range of useful properties. They are mainly manufactured using either a precursor or a melting method. However, the processes involved are complicated because of the need for a primary extrusion step and the addition of a pore-forming agent. Also, because of the large amount of energy required for the sintering step, these methods represent a large environmental burden. To solve this problem, the present study focused on the formation of solidified porous aluminum by a reaction between pure aluminum powder and pure water, without the need for sintering. The effect of the formation temperature was investigated by measuring the amount of hydrogen released during the reaction, and the density and microstructure of the final materials. X-ray diffraction measurements and compression tests were also carried out. The results of the microstructural observations and X-ray diffraction measurements indicated that, during the reaction, a bayerite layer was formed on the surface of the powder particles. With increasing temperature, the reaction was found to start more quickly and more hydrogen was released. Furthermore, from the compression tests, the initial maximum stress, the plateau stress and the absorbed energy decreased with increasing formation temperature. The results of the present study indicated that it was possible to form highly porous aluminum using the proposed method.

Key Factors for Depressurization-Induced Gas Production from Oceanic Methane Hydrates

Oceanic methane hydrate (MH) deposits have been found at high saturations within reservoir-quality sands in the Eastern Nankai Trough and the Gulf of Mexico. This study investigates the key factors for the success of depressurization-induced gas production from such oceanic MH deposits. A numerical simulator (MH21-HYDRES: MH21 Hydrate Reservoir Simulator) was used to study the performance of gas production from MH deposits. We calculated the hydrate dissociation behavior and gas/water production performance during depressurization for a hypothetical MH well. Simulation runs were conducted under various initial reservoir conditions of MH saturation, temperature, and absolute permeability. A productivity function (PF) was introduced as an indicator of gas productivity, which is a function of gas production rate, water production rate, and discount rate. The simulations showed that recovery factors over 36% and maximum gas production rates over 450 000 Sm3/d were expected for the most suitable conditions of a class 3 deposit (i.e., an isolated MH deposit that is not in contact with any hydrate-free zone of mobile fluids). However, gas productivity was affected by formation temperature and initial effective permeability. The values of PF increased with increasing formation temperature when the initial permeability of the deposit was higher than a threshold value (the threshold permeability); however, it decreased for the deposit below the threshold permeability. The threshold permeability was estimated to be between 1 and 10 mD in the class 3 deposit. These results suggest that key factors for the success of depressurization-induced gas production from oceanic MH are as follows: (1) The initial effective permeability of the MH deposit is higher than the threshold value, and (2) the temperature of the MH deposit is as high as possible.

Crystal chemistry of aegirine as an indicator of P-T conditions

AbstractOne metamorphic and four magmatic aegirines, together with two end-member aegirines synthesized at atmospheric pressure and different temperatures, were investigated by single-crystal X-ray diffraction. The limited compositional differences allow the polyhedral volumes to be almost constant in all the aegirines investigated( VM1 ≈ 11.0 Å3; VM2 ≈ 26.3 Å3; VT ≈ 2.21 Å3). However, differences in polyhedral distortions are responsible for the cell-volume variations, reflected mainly in the change of a and β cell parameters. Cell volume is only partly related to the composition of these aegirines: with increasing formation temperature, an increase in the unit-cell volume of ~1.2 Å3 is observed, while a significant contraction of the cell volume occurs during high-pressure formation. As the difference in cell volume between the two synthetic aegirines is ascribed to the different conditions of synthesis temperature, the same interpretation could be adopted for the differences observed in natural aegirines.

Temperature-Responsive Formation of Colloidal Nanoparticles from Poly(N-isopropylacrylamide) Grafted with Single-Stranded DNA

The thermal properties and temperature-responsive nanoparticle formation of poly(N-isopropylacrylamide) grafted with single-stranded DNA (PNIPAAm-g-DNA) were investigated. Copolymerization between nonamer single-stranded DNA with a vinyl group at its 5' terminus (DNA macromonomer) and NIPAAm was carried out so that the DNA macromonomer unit content should be less than 1 mol %. The turbidimetry and differential scanning calorimetry of the copolymer showed that the transition temperature increased and the enthalpy change of the phase transition decreased with increasing DNA macromonomer content in the copolymers, indicating that the DNA macromonomer behaves as a hydrophilic part in the copolymer and that the hydrophilicity is greater than that of sodium styrenesulfonate. Above the phase transition temperature, the copolymers formed colloidal nanoparticles with a dehydrated PNIPAAm core surrounded by DNA. When the formation of particles was conducted at higher temperatures, the dehydration of the copolymers proceeded such that the hydrodynamic radius (Rh) of the particles decreased. From the results of light scattering measurements, we calculated the surface area of particles occupied by one DNA (S(DNA)). The S(DNA) value decreased with increasing formation temperature, indicating that the DNA density on the particle surface increases with increasing formation temperature. The increase in the DNA density was also confirmed from the zeta-potential measurement of the particle. When MgCl2 was added to the copolymer solutions, the anionic charge of DNA was neutralized by Mg2+ so that Rh and the molecular weight of the particles increased with the increasing MgCl2 concentration. The turbidimetric detection of a target DNA was successfully demonstrated by utilizing the stability decrease of the colloidal particle upon hybridization on the particle surface.

Nickel, Platinum and Zirconium Germanosilicide Contacts to Ultra-shallow, P+N Junctions Formed by Selective SiGe Technology for CMOS Technology Nodes Beyond 70nm

AbstractSelective SiGe source/drain technology based on selective deposition of in-situ doped SiGe alloys in recessed source/drain regions can provide junctions with low sheet and contact resistance as well as abrupt doping profiles. This paper examines properties of Ni, Pt and Zr germanosilicides on heavily boron doped SiGe junctions. Our results show that all three metals can form low resistivity germanosilicides on heavily boron doped SiGe alloys. The stability of Ni germanosilicide was found to be limited to about 400°C on undoped SiGe. On heavily boron doped SiGe thermal stability was found to be significantly better possibly due to boron strain compensation. Our findings indicate that on undoped SiGe, thermal stability of Ni germanosilicide could be much enhanced by using a thin Pt interlayer. According to X-ray diffraction analysis, with increasing formation temperature, both Ni and Pt germanosilicides moved toward Ni and Pt monosilicides with signs of excess Ge appearing outside the contact. Analysis of the Pt germanosilicide layers is suggestive of a Ge rich SiGe layer under the germanosilicide. Boron diffusion into Pt and Ni germanosilicides was not observed. On the other hand, a distinct boron peak was observed in Zr germanosilicide suggestive of a stable Zr-B compound. Ultra-shallow junctions with excellent reverse bias behavior were formed using both Ni and Zr germanosilicides.

Coronal Hole Properties Observed with Sumer

We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained on both sides of the boundary of polar coronal holes as well as at other locations along the limb. We compare line intensities, shifts and widths in coronal holes with values obtained in the quiet Sun. We find that with increasing formation temperature, spectral lines show an increasingly stronger blueshift in coronal holes relative to the quiet Sun at an equal heliospheric angle. The width of the lines is generally larger (by a few km/s) inside the coronal hole. Intensity measurements show the presence of the coronal hole in Ne VIII lines as well as in Fe xII, with evidence for a slightly enhanced emission in polar coronal holes for lines formed below 105 K.