Deposition Conditions Research Articles

Comparative analysis of structural characteristics and thermal insulation properties of ZrO2 thin films deposited via chemical and physical vapor phase processes

ZrO2 is a flagship material for the development of efficient thermal barrier coatings not only for aerospace applications but also on steel molds for plastic injection, especially to produce high quality miniaturized parts of low environmental impacts. In the present study, ZrO2 thin films of thicknesses ranging between 4 and 40 μm were deposited on steel substrates by two key gas phase technologies, magnetron sputtering (PVD) and direct liquid injection metal organic CVD (DLI-MOCVD). The film morphology, structure and chemical composition were comparatively investigated and correlated to their heat transfer properties. All films were nearly stoichiometric and presented a columnar structure mainly formed of the monoclinic crystalline phase. The magnetron sputtering coatings were denser and smoother than the CVD ones, for which highly porous tree-like microstructures were observed without degradation of their mechanical properties. All films exhibited efficient thermal insulation properties, the thickest 40 µm magnetron sputtering coating displaying the most significant reduction in heat transfer. The CVD films provided the highest thermal gradient decrease across their thickness, probably thanks to their higher porosity associated to a multi-angle tree-like columnar structure, both acting as scattering zones of phonons involved in heat flow diffusion. By controlling the local deposition conditions influencing the nucleation and growth mechanisms, the film porous microstructure can thus be tuned to optimize the coating thermal properties.

CuxS films as photoelectrodes for visible-light water splitting

Copper sulfides are appealing semiconductors for optoelectronics applications requiring visible-light activity, such as solar water splitting, due to their relatively low band gaps and earth-abundance. This study investigates the effect of deposition conditions, including substrate temperature and background gas pressure, on the characteristics and photoelectrochemical performance of copper sulfide (CuxS) films grown by pulsed laser deposition (PLD) on Si (100) substrates. The results reveal that varying the deposition parameters influences the crystalline phases, morphology, and optoelectronic properties of the films. For deposition at room temperature, the films exhibited covellite CuS phase, while elevated deposition temperatures (250 °C and 500 °C) led to the formation of Cu1.8S and Cu2S phases, resulting in narrowing of the band gap, with the increased temperature also enhancing the film crystallinity and surface roughness. As a result of the changes in film morphology and crystal structure, photocurrent density magnitudes increased with higher deposition temperatures, reaching 0.747 mA/cm2 at −0.8 V for films deposited at 500 °C under vacuum, at least an order of magnitude higher than reported in comparable previous studies of the photoelectrochemical performance of CuxS. Background gas pressure only slightly affected the photocurrent density, with changes in photoactivity also correlating with changes in film roughness and band gap. The results demonstrate the good visible-light activity and behavior of CuxS as a stand-alone photoelectrode material, with tunability based on the fabrication conditions, suggesting their potential use in photoelectrochemical and other solar energy conversion applications.

Characteristics and Control Factors of a High-Quality Deeply Buried Calcareous Sandstone Reservoir, the Fourth Member of the Upper Xujiahe Formation in the Western Sichuan Basin, China

A special type of sandstone in which carbonate rock fragments (CRFs) dominate the composition developed in the Upper Triassic Xujiahe Formation’s fourth member (Xu4) in the western Sichuan Basin, known as calcareous sandstone. Calcareous sandstones are widely distributed in the western Sichuan and is the main production target of tight sandstone gas in the Sichuan Basin. In this study, thin sections, porosity–permeability testing, scanning electron microscopy, and X-ray diffraction are applied to examine the characteristics and control factors for high-quality reservoirs in the calcareous sandstones, with a view to providing guidance for natural gas exploration and development in calcareous sandstones. The results show that the calcareous sandstone belongs to litharenite, with an average framework grain composition of 30% quartz, 1% feldspar, and 69% rock fragments, while the Xu4 sandstone has a high quartz content (average content of 71%). Primary intergranular pores are the main storage space, and the reservoir quality is quite poor. Under the influence of different parent rock properties of sandstones, there are obvious differences in the composition of framework grains between the calcareous sandstone and the ordinary Xu4 sandstone, which in turn affects the reservoir storage space, diagenesis, and reservoir quality. High-energy depositional conditions, low content of late cements, and the development of fractures are the main controlling factors for the formation of high-quality reservoirs in Xu 4 calcareous sandstones.

Effect of gadolinia–stabilized zirconia nanoparticles manufactured from Mist CVD on the mechanical properties of ceramics sintered by SPS

Zirconia is an engineering ceramic material with excellent comprehensive properties. However, it suffers from the inherent disadvantage of low fracture toughness. To improve its fracture toughness, Gd2O3 is an effective stabilizer. In the present study, Gd2O3–ZrO2 composite powders were synthesized using the Mist CVD method. Following synthesis, these powders were pressed through spark plasma sintering. The crystallinity of the Gd2O3–ZrO2 powders improved as the deposition temperature increased from 600°C to 900°C. The tetragonality (c/2a) of the Gd–TZP composites increased from 0.99941 to 1.01571 as the Gd2O3 content increased from 2 mol% to 4 mol%, but it decreased when the content reached 5 mol%. The Gd2O3–ZrO2 nanoparticles produced via the Mist CVD approach presented a unique hollow spherical structure. Under moist chemical vapor deposition (CVD) conditions with 4 mol% Gd2O3 at 1400°C, the Gd–TZP composites exhibited fracture toughness and hardness values of approximately 12.03 ± 0.15 MPa·m1/2 and 12.16 ± 0.17 GPa, respectively.

Phosphorus doped hydrogenated silicon oxycarbide: Film formation, properties and its application on silicon heterojunction solar cell

An ultrathin phosphorus doped hydrogenated microcrystalline silicon oxycarbide (n-μc-SiCO:H) layer deposited by plasma enhanced chemical vapor deposition (PECVD) method can be used as a window layer for silicon heterojunction solar cells. The optical and electrical properties of n-μc-SiCO:H films were controlled by PECVD deposition conditions. The interplay effects of H2, CO2 and PH3 to SiH4 gas ratio on the chemical composition, material structure and properties of n-μc-SiCO:H film were systematically determined. O, H, C and P atoms were observed to incorporate into the silicon network of n-μc-SiCO:H layer, while most of the atoms bond directly to Si atoms. Incorporation of oxygen and carbon atoms into n-μc-SiCO:H film, confirmed by XPS as formation of Si-O and Si-C bonds, enlarged the optical absorption band gap (Eg) value. Both film crystallinity and phosphorus concentration in n-μc-SiCO:H layer were observed to be controlled by the H2, CO2 and PH3 to SiH4 gas ratio. The electric performance of HJT solar cell was depended on the optical and electrical properties of n-μc-SiCO:H layer. An average efficiency (across ∼ 120 cells) of 26.32 % was achieved in cells with optimized deposition parameters for the n-μc-SiCO:H layer. The reaction gas ratio was also the dominant factor in determining the number and size of nanoscale Si crystallites embedded in the n-μc-SiCO:H layer. The conductivity of n-μc-SiCO:H layer was determined by the activated phosphorus concentration but independent of the total phosphorus concentration. It was also found that large concentrations of small Si crystallites of size less than 3 nm improved film conductivity.

Two-episode mineralization in the Haerdaban Pb–Zn deposit, NW China: Insights from sulfide trace elements, in situ S–Pb isotopes, and Rb–Sr geochronology

The Haerdaban Pb–Zn deposit, located in the eastern West Tianshan Orogen, hosts stratiform and vein-type mineralization within Precambrian carbonate rocks. However, there has been limited research on the distinctions and relationships between these two mineralization styles. In this study, we compared trace element distributions, fluid conditions, material sources, and mineralization ages between stratiform and vein-type mineralization and reconstructed a detailed genetic model. Two episodes and four stages of mineralization were identified, including five generations of pyrite and two generations of sphalerite. The sedimentary exhalative episode represents stratiform mineralization including Stage I pyrite–pyrrhotite layers (Py-1, Py-2a, Py-2b, and Py-3) and Stage II sphalerite–galena layers (Sph-1). The magmatic–hydrothermal episode represents vein-type mineralization including Stage III pyrite–quartz–calcite veins (Py-4) and Stage IV sphalerite–galena–quartz–calcite veins (Sph-2). LA–ICP–MS analysis of Se–Co–Ni–As–Ag–Sb–Bi contents in pyrite suggests that Py-1 to Py-3 formed under relatively low temperatures (280 ± 8 °C) and high ƒO2 sedimentary conditions. Py-4 formed under relatively high temperatures (339 ± 18 °C) and low ƒO2 hydrothermal conditions. Variations in Fe–Mn–In–Ga–Ge–Cd–Cu contents in sphalerite indicate that Sph-1 formed under relatively low temperature (211 ± 7 °C), intermediate ƒS2 (logƒS2 = −11.1 ± 0.5), and moderate pH sedimentary exhalative conditions. Sph-2 formed under relatively high temperature (292 ± 5 °C), high ƒS2 (logƒS2 = −7.4 ± 0.2), and low pH hydrothermal conditions. In situ analysis of sulfide S–Pb suggests that ore-forming materials for stratiform mineralization were primarily derived from marine sediments, while those for vein-type mineralization primarily originated from magmatic sources. Sph-1 from stratiform mineralization yielded an Rb–Sr isochron age of 719 ± 16 Ma, while Sph-2 from vein-type mineralization exhibited an Rb–Sr isochron age of 380.3 ± 7.7 Ma. Random Forest classification of trace elements in pyrite and sphalerite predicted that stratiform mineralization is of sedimentary genesis, whereas vein-type mineralization is of magmatic–hydrothermal genesis. Based on our results, we identified a two-episode mineralization history for the Haerdaban Pb–Zn deposit: Neoproterozoic syngenetic sedimentary exhalative mineralization overprinted by Devonian epigenetic magmatic–hydrothermal mineralization. The results of this study highlight the importance of considering multiple geological events in ore-forming processes and will facilitate the exploration of similar deposits in the West Tianshan Orogen.

Soil cover on complex glacial terrain and challenges for large-scale soil mapping using the World Reference Base (WRB) classification system

In conditions of complex glacial topography, large-scale soil mapping (1:10 000) according to the World reference base for soil resources (WRB) 2022 classification faces significant challenges. High diversity of reference soil groups (RSG) and qualifiers can be found in a small area, and this diversity is not related to the influence of a single but rather to a set of soil-forming factors. As a part of the study, the classification of soils on postglacial landscape was conducted using the WRB 2022 classification system. The analysis was focused on examining relationships between RSG and qualifiers, and also with type of geological deposits, location on the terrain, human activities (drainage of agricultural land, soil tillage and erosion). Survey showed that, in a relatively small area, soil cover consisted of WRB RSG such as Luvisols, Retisols, Regosols, Stagnosols, Gleysols Phaeozems, Planosols, Podzols, Histosols and Anthrosols, with the respective sets of qualifiers. Soils corresponding to the Anthrosol RSG were formed during the construction of a drainage system by burying the former soil with deeper material and later by translocation of colluvium by soil erosion. In the complex glacial topography, the distribution of RSG and their qualifiers is specific, which poses a number of challenges for soil mapping. The study confirmed the possibility of WRB classification for large-scale mapping of agricultural soils on postglacial landscape at the RSG level. The use of qualifiers for definition of mapping units in similar conditions of complex terrain and geological deposits (when mapping on a scale of 1:10 000) is possible only by increasing sampling density.

Evolution of a confined gravelly river to a braided-meandering river in the Late Cretaceous Khasi group, southern Shillong plateau, NE India

This paper intends to unravel the depositional condition of the Basal Conglomerate/Jadukata Formation and the Lower Mahadek Formation in southern Shillong Plateau, NE India deposited during the Late Cretaceous period. The studied succession is entirely siliciclastics in composition and was built up on the Precambrian basement rocks. State-of-art facies analysis and palaeocurrent evidence helped us to reconstruct the palaeogeography and palaeoenvironment. The facies tracts reveal that frequent hyperconcentrated mass flow deposits dominated the proximal part of the river channels. Gradually, the river evolved to a sandy braided and finally mud-dominated, meandering system. The river channel changed its pattern through onlapping and progressive elimination of the accommodation space created by the tectonic subsidence/upliftment. Major shifts in palaeocurrent direction at different stages of the river evolution confirm the role of tectonics on the river channel evolution. QFL detrital modes of the sandstones reflecting lithic wacke composition and the recycled orogeny corroborate the interpretation. Rapid lateral and vertical facies transition suggests a pull-apart type basin due to ongoing rifting. Geochemical analyses also show signatures of the overlapping tectonic conditions supporting the pull-apart basin model.

Mind your tyres: The ecotoxicological impact of urban sediments on an aquatic organism

The presence of tyre and road wear particles (TRWP) in the environment is an underestimated threat due to their potential impact on ecosystems and human health. However, their mode of action and potential impacts on aquatic ecosystems remain largely unknown. In the present study, we adopted a sediment exposure scenario to investigate the influence of sediment coming from an urban runoff sedimentation basin on the life cycle of Chironomus riparius. Targeted broad-spectrum chemical analysis helped to characterise the urban sediments and confirmed the significant contribution of contaminants from traffic (e.g. tyre wear contribution, Polycyclic Aromatic Hydrocarbons [PAHs], metals, tyre rubber additives). First-stage chironomid larvae were subjected to increasing concentrations of urban whole sediment. The results showed that exposure to this urban sediment influenced all measured endpoints. In vivo quantification of ROS showed that larvae exposed to the lowest concentration of contaminated sediment exhibited increased fluorescence. The contaminated sediment conditions increased mortality by almost 30 %, but this effect was surprisingly not concentration-dependent. Fertility decreased significantly and concentration-dependently. The results of the Mean Emergence Time (EmT50) and larval size showed an optimality curve. Furthermore, as a consequence of the effects on fitness, the Population Growth Rate (PGR) exhibited a significant decrease, which was concentration-dependent. Therefore, after a single generation, PGR calculation can be adopted as a sensitive tool to monitor pollution caused by complex matrices, i.e. composed of several contaminants. Our research highlights the importance of effective management of road runoff and underlines the need for further investigation to better understand the toxicity of TRWPs.

Photocatalytic removal of organic dyes mediated by p-NiO/p-CuO isotype heterojunctions under sunlight illumination

Building heterojunctions between different semiconductors is one of the most typical approaches to separating photo-induced electrons and holes in order to enhance photocatalytic efficiency. In this study, NiO, CuO, and NiO–CuO nanocomposites thin films are obtained under the same deposition conditions by a simple spray pyrolysis technique. The structural, morphological, and optical properties of the deposited thin films were investigated using different techniques such as XRD, Raman, SEM, EDX, PL, and UV–visible spectroscopy. XRD and Raman analysis revealed that NiO, CuO, and NiO–CuO have crystalline cubic, monoclinic, and mixed phases, respectively. EDX analysis confirmed the chemical composition, and SEM images reveal different morphologies depending on the Ni:Cu molar ratio. The photodegradation of MB dye in the presence of the thin films was examined under sunlight. Compared with individual metal oxides, NiO–CuO nanocomposites are better as photocatalysts. Optical measurements were able to connect these enhanced photocatalytic activities to the synergistic effects of combining NiO and CuO, which promoted the creation of defects and highly reactive species on surfaces and an effective separation of photogenerated charges. The benefits of p-p isotype heterojunctions for dye photodegradation that this study has illustrated provide a novel perspective on metal oxydes-based nanocomposites for the development of efficient and novel photocatalysts.

Deep tectonics and oil and gas prospectives of the kura depression according to geophysical data

According to the sedimentary features, the transfer of the upper, middle and lower case segments of the Kura depression is marked by oil-scientists and researchers. Structure-tectonic signs of these segments are significantly different, and are characterized by favorable conditions for the emergence, migration and gene- ration of hydrocarbons. Emigrate oil and gas products in basins created potential fields in favorable anticlinal structures, oil and gas collectors. Kur-Cabrırrı is the main oil-gas complex plieli-gas complex pliocene sediments in the Lower Kura depression in the Key-Caucasian Mmmatic basin in the Zevabadi Magmathic basin. It is of great importance in terms of monitoring the history of paleostructural development of these complexes, starting the mass generation of oil and gas, to investigate their migration directions, formation and maintenance of oil and gas fields. The official article was dedicated to the results of the complex in recent years in recent years, according to the results of regional geophysical intelligence work carried out by Azerbaijan and foreign companies. Based on a comprehensive analysis of geophysical information on regional profiles, the tectonic structure of Mesozoic-Cenozoic deposits was clarified, the conditions of sedimentation in the basins were assessed, changes in thickness were traced, and new explanations of the geological development of the territory were provided. At the same time, the boundaries of the Mugan monocline with the Jalilabad depression and the Karaja-Gyzylagad uplift zone have been clarified.

Effect of Sulfuric Acid Immersion on Electrical Insulation and Surface Composition of Amorphous Carbon Films

Sulfuric acid is a concern for contacts within electronic devices, and the application of amorphous carbon films as thin electrical insulating coatings for small coils requires full investigation of its effects. Five types of amorphous carbon films were fabricated on Si substrates under different deposition conditions using vacuum coating systems. Based on their optical constants (ISO 23216:2021(E)), the films were classified into three types: hydrogenated amorphous carbon (a-C:H), polymer-like carbon (PLC), and graphite-like carbon (GLC). The structure, surface composition, and electrical insulation properties of the films were evaluated before and after immersion in sulfuric acid. Although the PLC and a-C:H showed progression of surface oxidation due to sulfuric acid immersion, none showed obvious changes in their structure or DC dielectric breakdown field strength due to sulfuric acid immersion, proving their stability. Furthermore, the PLC and a-C:H, which had a relatively low extinction coefficient, exhibited excellent insulation properties. Our results suggest that amorphous carbon films can be useful as thin insulating films for small coils that may come in contact with sulfuric acid. Our study offers a valuable tool for general users in the industry to facilitate selection of electrical insulating amorphous carbon films based on optical constants, such as extinction coefficients.

Optimizing Electrodeposition of Polyaniline on Various Woven Steel Mesh Sizes for Enhanced Supercapacitor Performance.

The development of efficient supercapacitors hinges on the innovation of superior electrodes, which are pivotal in augmenting their energy storage capabilities. Supercapacitors, recognized for their high-power density and extended cycle life, play a crucial role as sustainable solutions in addressing energy storage challenges. A fundamental aspect of supercapacitor functionality involves the electrode material, which works in concert with other key components such as the current collector, separator, and electrolyte. This study focuses on evaluating the impact of the current collector material on the performance of symmetric supercapacitors. We investigated the electropolymerization of polyaniline on woven steel mesh current collectors of varying mesh sizes, ranging from 20 to 200 mesh per inch, using assorted deposition conditions. The electrochemically modified woven steel meshes were utilized to construct symmetric supercapacitors. The electrochemical performance of the assembled supercapacitors, configured in a two-electrode system, was investigated using a variety of electrochemical techniques to better understand the kinetics of electrolyte ion migration. Notably, the 20-mesh size, characterized by the fewest pores per inch, demonstrated superior performance with an optimum capacitance of 4730 mF/cm2, an energy density of 317.8 μWh/cm2, and a power density of 400 μW/cm2 at a current density of 1 mA/cm2.

Engineering Thin Films of Silicon Phthalocyanines for Organic Thin Film Transistors

Metal phthalocyanines (MPc) show great promise as semiconductors due to their exceptional optoelectronic properties, high thermal and photochemical stability, and ability to be easily synthesized and functionalized for specific applications. The metal/metalloid ion in the center of the MPc ring can significantly influence the electronic, optical, and magnetic properties of the compound, as well as its solubility and stability. The majority of MPc, such as copper phthalocyanine (CuPc) are used as hole-transport materials (p-type) in organic electronics. Silicon phthalocyanines (R2-SiPc) are emerging semiconductors which predominantly moves electrons and have led to high performance n-type organic thin-film transistors (OTFTs). Their low synthetic complexity paired with their versatile axial group facilitates the finetuning of their chemical properties, solution properties and processing characteristics without significantly affecting their frontier orbital levels or their absorption properties. The crystal engineering and film forming characteristics of R2-SiPc semiconductors can be tuned through appropriate axial group functionalization, therefore facilitating their integration into both OTFTs and OPVs by solution processing or vapor deposition.Our group has developed families of R2-SiPc and integrated them into OTFTs with an emphasis on thin film processing and engineering of the interfaces for improved device performance. We have established structure property relationships of the final device performance as a function of 1) R2-SiPc axial groups and peripheral groups, 2) surface chemistry and composition and 3) thin film deposition conditions. I will also be discussing our recent work using advanced film characterization such as polarized Raman microscopy and synchrotron based scanning transmission x-ray microscopy to evaluate the resulting films and optimize the OTFT performance. Figure 1

Low Contact Resistance on Monolayer MoS2 Field-Effect Transistors Achieved by CMOS-Compatible Metal Contacts.

Contact engineering on monolayer layer (ML) semiconducting transition metal dichalcogenides (TMDs) is considered the most challenging problem toward using these materials as a transistor channel in future advanced technology nodes. The typically observed strong Fermi-level pinning induced in part by the reaction of the source/drain contact metal and the ML TMD frequently results in a large Schottky barrier height, which limits the electrical performance of ML TMD field-effect transistors (FETs). However, at a microscopic level, little is known about how interface defects or reaction sites impact the electrical performance of ML TMD FETs. In this work, we have performed statistically meaningful electrical measurements on at least 120 FETs combined with careful surface analysis to unveil contact resistance dependence on interface chemistry. In particular, we achieved a low contact resistance for ML MoS2 FETs with ultrahigh-vacuum (UHV, 3 × 10-11 mbar) deposited Ni contacts, ∼500 Ω·μm, which is 5 times lower than the contact resistance achieved when deposited under high-vacuum (HV, 3 × 10-6 mbar) conditions. These electrical results strongly correlate with our surface analysis observations. X-ray photoelectron spectroscopy (XPS) revealed significant bonding species between Ni and MoS2 under UHV conditions compared to that under HV. We also studied the Bi/MoS2 interface under UHV and HV deposition conditions. Different from the case of Ni, we do not observe a difference in contact resistance or interface chemistry between contacts deposited under UHV and HV. Finally, this article also explores the thermal stability and reliability of the two contact metals employed here.

Berthierine/Chamosite ooids and associated phases in Devonian deposits of the Parnaíba Basin, Brazil: Genesis and diagenetic evolution

The Parnaíba Basin Devonian deposits comprise ironstones and organic-rich sediments deposited in an epeiric sea margin under greenhouse conditions, enhanced weathering, reduction of oceanic circulation, and black shale deposition. This study aims to contribute to the understanding of the interrelation between depositional and shallow diagenetic processes of the Devonian units of the Parnaíba Basin, specifically regarding the genesis of iron minerals that constitute the ooidal ironstones of the Itaim and Pimenteiras formations. These units comprise bioturbated heterolites, ooidal ironstones, intraclastic conglomerates, and shales, deposited in a deltaic to neritic, storm-dominated platform. This research investigates drill cores from two wells in the southern part of the Parnaiba Basin, focusing on depositional and diagenetic processes. The proposed model suggests deposition of sediments originally rich in organic matter, under low siliciclastic input, and initially anoxic, transgressive conditions. Under these conditions, ferroan precursor clays were deposited, alternating with periods of reworking by storm currents, generating concentric ooids of berthierine. Bioturbation processes resulted in the concentration of previously formed berthierine ooids during intervals of low sedimentation rates. Eodiagenetic microcrystalline siderite formed along the redox boundary between oxic/bioturbated and anoxic zones. Chamosite formed by partial transformation of berthierine, upon incipient mesodiagenetic evolution of the ooidal ironstones. This study contributes to the understanding of depositional and diagenetic conditions in the Devonian section of the Parnaíba Basin, and of similar deposits, offering insights into the formation and development of berthierine ooids under the influence of sea level fluctuations, oxic/anoxic conditions, sedimentation rate, and bioturbation in sedimentary environments, providing key insights into the paleoenvironmental conditions along the northern Gondwana margin during this period.

Raman Spectroscopy as an Effective Tool for Assessment of Structural Quality and Polymorphism of Gallium Oxide (Ga2O3) Thin Films.

Raman spectroscopy, a versatile and nondestructive technique, was employed to develop a methodology for gallium oxide (Ga2O3) phase detection and identification. This methodology combines experimental results with a comprehensive literature survey. The established Raman approach offers a powerful tool for nondestructively assessing phase purity and detecting secondary phases in Ga2O3 thin films. X-ray diffraction was used for comparison, highlighting the complementary information that these techniques may provide for Ga2O3 characterization. Few case studies are included to demonstrate the usefulness of the proposed spectroscopic approach, namely the impact of deposition conditions such as metal-organic vapor-phase epitaxy and pulsed electron deposition (PED), and extrinsic elements provided during growth (Sn in the case of PED) on Ga2O3 polymorphism. In conclusion, it is shown that Raman spectroscopy offers a quick, reliable, and nondestructive high-resolution approach for Ga2O3 thin film characterization, especially concerning phase detection and crystalline quality.

Analysis of the sediment deposition characteristics in the Three Gorges Reservoir and its influence factors

Affected by climatic factors and human activities, the conditions of the sediment deposition of the Three Gorges Reservoir (TGR) in the upper Yangtze River have undergone significant changes, the understandings of the sedimentation in TGR and its factors remain unclear. In this paper, the regime for sediment deposition in TGR from 2003 to 2017 is analyzed based on field data, its influence factors are discussed, and the empirical formulas governing the relationships are presented. The results show that the sedimentation pattern of the TGR is discontinuous and that the perennial inundated area is the key sedimentation area, while the reaches of Xiangxizhen, Wushan, Fengjie, Wanxian, Huanghuacheng, Lanzhuba, and Tunaozi are the main deposition reaches in the reservoir, with the same characteristics of wider cross-sections. Sediment deposition in the TGR is affected by the incoming water and sediment, the operation rule of the reservoir, and by the characteristics of different reaches. Compared with the factors influencing the total sediment trapping ratio of the reservoir, local reach conditions are also the main factors influencing the sediment trapping ratio of the reaches due to the difference of sediment carrying capacity between wider reach and narrow reach. The sediment trapping ratios for reservoir scale and reach scale can be good indicators that reflect sedimentation in the TGR; the calculated sediment trapping ratios agree well with field observations. With the continuous construction and operation of the main and tributary reservoirs in the upper Yangtze River, the existing sedimentation regime of the TGR will persist for many years.

Formation condition for concave-bank deposition in the meanders of the Middle Yangtze River and its application

In what kind of meanders concave-bank deposition (CBD) can occur remains an open question. This study investigated the characteristics and major influencing factors of CBD in the meanders of the Middle Yangtze River (MYR), and proposed a formation condition for CBD. Concave-bank deposition occurred in 10 of 23 meanders in the MYR, including two types: counter point bar (CPB) and concave-bank bench (CBB). CPB occurred in both mildly-curved and sharp bends, while CBB only occurred in sharp bends. Hydrodynamic conditions and sediment supply are two major factors controlling the formation of CBD. The incoming sediment load remained in an amount of 0.68 × 108 t/y at Jianli and 0.77 × 108 t/y at Luoshan after Three Gorges Project operation, therefore, CBD development was not limited by a lack of sediment and instead is mainly dependent on the hydrodynamic conditions in the MYR. Flow separation zones were observed in the typical CBD-type bends of the MYR, which indicated that CBD was the result of flow separation or recirculation. An adverse longitudinal water surface gradient is the necessary condition for the formation of concave-bank flow separation. Therefore, a formation condition for CBD was proposed based on this assumption, which considered the combined effects of channel resistance, riverbed slope, channel widening, and curvature. CBD happens when the channel widening and curvature terms are greater than the channel resistance and longitudinal channel slope terms. The proposed condition was verified based on the data of the 23 bends in the MYR and 26 bends in 12 other rivers. The results indicated that more than 85% of the bends were correctly identified. Therefore, the proposed formation condition provided considerably high accuracy.

Geochemical fingerprints of Dongpu Depression crude oils in Bohai Bay Basin, northern China: Insights from biomarkers and isotopic compositions of selected alkylnaphthalenes and alkylphenanthrenes

The Dongpu Depression is a rift lake in the Bohai Bay Basin of eastern China, where abundant oil and gas resources were discovered. Previous geochemical investigations of Dongpu Depression oils have revealed a notable lack of data regarding the isotopic compositions of individual polycyclic aromatic hydrocarbons (PAHs) from the discovered Cenozoic crude oils. Using gas chromatography-mass spectrometry (GC–MS) and gas chromatography-isotope ratio mass spectrometry (GC-IRMS), a novel approach combining molecular parameters and stable carbon isotope compositions of individual PAH was applied to study the depositional environment conditions, the different source inputs, the maturation stage and to identify the potential family of five crude oils selected from Dongpu Depression.A decrease of Ga/C30H together with low Pr/Ph ratios and changes in isotopic compositions indicate that the five Dongpu Depression oils were derived from OM deposited in an anoxic saline environment with a stratified water column where mixing of saline water and freshwater occurred. The low isoprenoid, tricyclic and tetracyclic terpane ratios in combination with the δ13C values of 1,6-DMN, 1,2,5-TMN, 1,3,6,7-TeMN, 9-MP and 1-MP attest that their sources have a mixed origin with high aquatic organism (planktonic) input and a lower land plant (C3 plant) contribution. The δ13C values of phenanthrene between −30.0 ‰ and −20.0 ‰ indicate that the studied Dongpu Depression oils belong to a single family generated from the peak to the late oil generation stage (Rc-TNR-2 between 0.85 and 1.15 %). A correlation with various basins indicates that oil samples featured by δ13C values of Phen between −30.0 ‰ and −20.0 ‰ correspond to crude oils derived from mixing of aquatic and high plant contributions with different degrees of mixtures, which have not yet reached their cracking stage (Rc < 2.0 %). Crude oils from the Carboniferous and Mesozoic-Cenozoic Tarim rocks, Australian petroleum systems, Termit Basin, Bongor Basin, Fushan Depression and the studied Dongpu Depression oils belong to that group of oils. Crude oils characterized by lighter phenanthrene isotopic compositions (δ13C values of Phen < −30.0 ‰) are mainly derived from marine/aquatic input and have already entered the cracking window (Rc > 2.0 %). This group of oils is represented in this study by the Cambrian-Ordovician Tarim Basin oil samples. The research shows the importance of the aromatic isotopic compositions in petroleum system characterization and could be used as a reference for a practical exploration campaign of petroleum.