Trench Deposits Research Articles

Immersed Interface and Diffuse-Domain Approach for Current-Potential Distributions and Electrodeposition Problems

Several numerical approaches are being developed to solve the moving boundary models which predict the morphological evolution of the electrode surface during electrodeposition. Despite these significant research efforts over a broad range of materials, scales, and purposes, the prediction of the shape evolution of the electrodes over time is still a challenging problem. One needs to solve these moving boundary problems, as the potential and current distributions within the cell get affected by the geometry.1-2 In this work, we will demonstrate a recently developed numerical framework based on the diffused domain approach using phase-field models for two classical example, Hull cell and copper deposition in trenches.3 The original model equation was carefully reformulated as a diffuse-domain/immerse domain approach for steady state current-potential distribution problems.4-5 Then the shape change problem is cast as a transient phase-field problem to predict the shape changes of the electrode during electrodeposition. A comparative analysis has also been performed for the efficiency, accuracy, speed, and convergence of the present solutions for the Hull cell with other available numerical and even analytical methods. It can be stated that the present phase-field model is robust and efficient for predicting the shape changes of the electrode over time without oscillations. Acknowledgments This research was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy (DoE) through the Advanced Battery Materials Research Program (Battery500 Consortium) References V. R. Subramanian, and R. E. White, J. Electrochem. Soc, 149(10) C498 (2002).R. Alkire, T. Bergh, and R. L. Sani, J. Electrochem. Soc., 125, 1981 (1978).T. Jang, L. Mishra, S. A. Roberts, A. Subramaniam, M. Uppaluri, M. P. Gururajan, J. Zhang, and V. R. Subramanian, “BattPhase – A convergent, non-oscillatory, efficient algorithm and code for predicting shape changes in lithium metal batteries using phase-field models – 1. Secondary Current Distribution,” ECSarXiv (2022), doi:10.1149/osf.io/k2vu6C. S. Peskin, Acta Numer., 11, 479 (2003).X. Li, J. Lowengrub, A. Ratz and A. Voigt, Commun. Math. Sci., 7, 81 (2009).

Plasma-enhanced atomic layer deposition of SiO2 film using capacitively coupled Ar/O2 plasmas: A computational investigation

Plasma-enhanced atomic layer deposition (PE-ALD) is widely used for dielectric deposition in semiconductor fabrication due to its ability to operate at low temperatures while having high precision control. The PE-ALD process consists of two subcycles: precursor dosing and plasma exposure with gas purging and filling in between. In the PE-ALD of SiO2, a Si-containing precursor is first deposited on the surface, usually in a plasma-free environment. The surface is then exposed to an oxygen-containing plasma during which the residual components of the precursor are removed and the Si oxidized. Various factors affect the outcome of SiO2 PE-ALD, such as exposure times during each step, steric hindrance of the Si precursor, and plasma properties, such as the energy of ions incident onto the film. The results from computational investigations of the first layers of SiO2 PE-ALD at both reactor (cm) and feature (nm) scales are discussed in this paper. The example system uses bis(tertiary-butylamino)silane, SiH2[NH(C4H9)]2 as the silicon precursor during dosing and plasmas operating in Ar/O2 gas mixtures during the oxidation step. Parametric studies were performed for blanket deposition, as well as deposition in trenches and vias while varying power, pressure, plasma exposure time, aspect ratio, and ligand retention in the film. The general trends show that conditions that reduce the fluence of reactive oxygen species typically decrease the O/Si ratio, increase the vacancies in the films, and decrease the order of the film. Conditions that result in higher ion fluxes having higher energies produce the same result due to sputtering. The retention of ligand groups from the precursor significantly decreased growth rates while increasing vacancies and reducing the O/Si ratio.

Provenance evolution during passive- to active-margin transition unraveled from an accretionary complex from the Bangong-Nujiang suture zone: Insights into Early Mesozoic Meso-Tethys subduction and source-area tectonics

The South Qiangtang terrane (SQT), the Tibetan representative of the Cimmerian continent, is bounded in the south by the Bangong-Nujiang suture zone (BNSZ). The BNSZ is geologically manifested by the Mugagangri Group (MG) accretionary complexes developed during northward Meso-Tethyan subduction, whose timing and processes are, however, contentious. Herein, we conducted provenance analysis on the MG trench deposits, via petrography, whole-rock geochemistry and detrital-zircon geochronology. The results reveal a complete picture of provenance evolution during passive- to active-margin transition (from subduction initiation through fringing oceanic-arc, to continental-arc developments) at the SQT margin. In particular, the earliest trench deposits (subunit Trma; ~222 Ma), which contain olistostromes with blocks of oolitic limestone shed from the destructing SQT passive margin, mark the subduction initiation. A second subunit (Trmb; ~210 Ma) has periodically elevated volcanogenic components. Conglomerates of subunit Trmb have abundant basaltic clasts of intra-oceanic arc geochemical affinities, which were likely derived from an intra-oceanic arc fringing the SQT. The youngest subunit (Jmd; ~190 Ma) exhibits enriched ferromagnesian elements and a major youngest detrital-zircon age peak, indicating a continental-arc provenance. Moreover, detrital-zircon age spectra suggest that, at ~210 Ma, the central Qiangtang metamorphic belt became an important source area, and the North Qiangtang terrane (NQT) replaced SQT as the main provenance. This is best explained by that the SQT underthrusted beneath the NQT and was downwarped to form a foreland basin. Our findings confirm that the initial subduction of Meso-Tethys beneath SQT was coeval to other Cimmerian terranes, likely a uniform response to the Paleo-Tethys closure and collision between Eurasia (NQT) and Cimmeria (SQT).

Additives for Superconformal Gold Feature Filling

An overview of the effect of additives on Au electrodeposition from Na3Au(SO3)2 based electrolytes is presented with an emphasis on filling of fully metallized recessed surface features such as trenches and vias. The impact of heavy metal additives Tl+, Pb2+, and Bi3+ is reviewed and accompanied by a brief survey of the effects of Sb3+, Te4+, SeCN−, 3-mercapto-1-propanesulfonic acid (MPS) and polyethyleneimine (PEI) additions. The addition of Tl+, Pb2+, Bi3+ or Sb3+ accelerates the kinetics of Au(SO3)2 3− reduction to Au, as manifest in hysteretic voltammetry and rising chronoamperometric transients, and yields bright specular deposits. Gold deposition with Pb2+ addition exhibits superconformal filling in sub-micrometer trenches while Bi3+ addition induces a more extreme bottom-up filling, but Tl+ and Sb3+ additions yield essentially conformal deposition for the conditions examined. Modest acceleration and hysteresis observed with Te4+ addition reflect roughening due to limited nucleation, 3D growth and delayed coalescence, rather than catalysis, and are associated with conformal feature filling. Unlike the other additives, SeCN−, MPS and PEI inhibit the deposition kinetics. Breakdown of suppression during deposition in micrometer size trenches is biased toward recessed surfaces where the flux of suppressor is constrained, yielding localized deposition and superconformal filling.

Event-dominated transport, provenance, and burial of organic carbon in the Japan Trench

The delivery of organic carbon (OC) to the ocean's deepest trenches in the hadal zone is poorly understood, but may be important for the carbon cycle, contain crucial information on sediment provenance and event-related transport processes, and provide age constraints on stratigraphic sequences in this terminal sink. In this study, we systematically characterize bulk organic matter (OM) and OC signatures (TOC/TN, δ13C, 14C), as well as those from application of serial thermal oxidation (ramped pyrolysis/oxidation) of sediment cores recovered along an entire hadal trench encompassing high stratigraphic resolution records spanning nearly 2000 years of deposition. We analyze two cores from the southern and northern Japan Trench, where submarine canyon systems link shelf with trench. We compare results with previously published data from the central Japan Trench, where canyon systems are absent. Our analyses enable refined dating of the stratigraphic record and indicate that event deposits arise from remobilization of relatively surficial sediment coupled with deeper erosion along turbidity current pathways in the southern and central study site and from canyon flushing events in the northern study site. Furthermore, our findings indicate deposition of predominantly marine OC within hemipelagic background sediment as well as associated with event deposits along the entire trench axis. This implies that canyon systems flanking the Japan Trench do not serve as a short-circuit for injection of terrestrial OC to the hadal zone, and that tropical cyclones are not major agents for sediment and carbon transfer into this trench system. These findings further support previous Japan Trench studies interpreting that event deposits originate from the landward trench slope and are earthquake-triggered. The very low terrestrial OC input into the Japan Trench can be explained by the significant distance between trench and hinterland (>180 km), and the physiography of the canyons that do not connect to coast and river systems. We suggest that detailed analyzes of long sedimentary records are essential to understand OC transfer, deposition and burial in hadal trenches.

Sedimentology and provenance of newly identified Upper Cretaceous trench basin strata, Dênggar, southern Tibet: Implications for development of the Eurasian margin prior to India–Asia collision

AbstractTrench basins preserved along the southern margin of the Lhasa Terrane, Tibet, are sedimentologic records of convergent margin processes preceding Cenozoic India–Asia collision. We present new sedimentologic, petrographic and geochronologic data from the Rongmawa Formation and surrounding strata near Dênggar, Tibet, to determine depositional environment, provenance and age. Depositional ages range from ca. 92 to 87 Ma and lithofacies are consistent with deposition by low‐ and high‐density turbidity currents and suspension settling of pelagic detritus in a deep‐marine, trench basin setting. Sandstone modal analyses and U–Pb geochronology indicate that trench basin detritus in this region was derived from the Lhasa Terrane. We interpret that the Cretaceous subduction trench received detritus from an axial sediment dispersal system that transported sediment from headwaters in the central‐southern Lhasa terrane near Lhasa City directly to the trench and then flowed westwards parallel to the trench. The preservation of trench basin strata deposited during Late Cretaceous time compared with the lack of trench deposits prior to ca. 92 Ma and after ca. 80 Ma suggests the margin experienced a period of significant accretion during this interval. In addition, deposition of trench basin strata occurred during Late Cretaceous adakitic magmatism and high‐temperature metamorphism, which are hypothesized to be explained by subduction of an oceanic ridge or subduction zone retreat and related upper plate extension along the southern margin of the Lhasa terrane. Subduction of an oceanic ridge may provide a mechanism to potentially erode forearc basin strata and promote increased sediment delivery directly to the trench.

Single and Multilayer Atomic Layer Deposition on and into Mesoporous Silicon Layers

Surface functionalization and pore filling of porous layers are essential key aspects for successful application of complex porous matrices. Atomic layer deposition (ALD) in deep macroporous trenches with high aspect ratio using different coating materials was investigated for a wide field of applications, such as energy storage, catalysis, and membrane technology1-3. Experimental data for ALD into mesopores, especially in the low mesoporous range (up to 20 nm) are rare4, 5. ALD on and into mesoporous silicon layers has different functions: 1st Surface passivation (sealing) of the underlying mesoporous structures, such as electrical barrier, diffusion barrier or corrosion protection. In this case complete pore filling is necessary to avoid transport processes through the passivated mesoporous interface. 2nd Pore size reduction (narrowing), i.e. adjustment of pore size for mesoporous membranes or single pores, e.g. for universally applicable, label-free, and nanopore-based sensor systems for the detection of small molecules in the nanofiltration range. Additionally, pore narrowing can be used for fine tuning of porous silicon-based sensors or optical filter properties5. 3rd Surface functionalization, e.g. in biomimetic or bioinspired systems or in fuel cells as catalytic layer.This contribution gives an extensive investigation of single and multi-layer depositions on and into mesoporous silicon layers and analyzes the material distribution and penetration profile of the corresponding atomic compositions.Mesoporous silicon layers were fabricated using highly doped (0.01-0.02 Ωcm) p-type substrates. Electrochemical etching (anodization) was performed in a mixture of 50 m% HF and absolute ethanol in volume ratio 1:1, to generate a 5 µm thick mesoporous layer. A current density of 70 mA/cm2 was used. 48 % porosity was measured by gravimetric technique. Nitrogen adsorption-desorption isotherms were measured in a Belsorp-mini from Rubotherm/Bel GmbH at 77 K using native porous silicon layers. Pore radius (rp) and pore radius distribution were evaluated using Barrett-Joyner-Halenda (BJH) theory. An average pore size radius of 4.68 nm, and pore radius range up to 12 nm were measured. However, surface oxidation will change the layer morphology, especially the pore size, porosity, and specific surface area.The layer deposition process was carried out with different ALD single layers, such as thermal Al2O3, plasma TiO2, thermal HfO2, thermal ZnO, and layer combinations as multilayer ALD, such as plasma Al2O3/TiO2 in an Oxford FlexAl reactor. Typical ALD cycle consists of two half-cycles, sequential precursor and co-reactant doses, which are separated by purge and pump steps, leading to self-limited layer growth6. Co-reactants and oxidizers are typically oxygen sources (H2O or oxygen plasma). When using an oxygen-containing medium, vacuum oxidation occurs, which leads to partial oxidation of the huge inner surface of the mesoporous layer5.Characterization of ultrathin layer deposited in complex 3D mesoporous structures is challenging and demands special analysis methods. In our experiments the penetration depth and depth distributions of atomic compositions for different ALD single and multilayers were measured using secondary neutral mass spectrometry (SNMS). Fig. 1 shows one example of the material distribution for Al2O3 atomic compositions on silicon substrate (Fig. 1a) and on and into mesoporous silicon substrate (Fig. 1b) with the same nominal Al2O3 layer thickness of 96.89 nm, which was measured on the silicon substrate with a Woollan M-2000FTM ellipsometer. The influence of both half-cycles of the ALD process must be considered at the evaluation, both the deposition effect on and into mesoporous silicon layers, and the transformation of the inner pore surface by oxidation. In the mesoporous layer the Al atomic composition profile follows the initial Al atomic profile up to 110 nm and subsequently shows a decreasing tendency up to 225 nm. The O atomic composition shows a decreasing tendency from 125 nm to 225 nm, and a saturation at 3.5 atomic percent. The existence of O in the deeper (>250 nm) mesoporous layers (Fig. 1b) indicates the partial oxidation of the underlying mesoporous layer occurring mainly during the H2O dose half-cycle process sequence. Penetration depths and profiles will be presented for the investigated single ALD layer. Further experimental results show that for multilayer ALD, e.g. with Al2O3/TiO2 layer combination, the first ALD-layer of the multilayer and its specific properties are dominating in the pore filling of the mesoporous layer.

Nanofabrication of 30 nm Au zone plates by e-beam lithography and pulse voltage electroplating for soft x-ray imaging

High resolution Fresnel zone plates for nanoscale 3D imaging of materials by both soft and hard X-ray are growingly needed in broad applications in nanoscience and technology. When the outmost zone-width approaches 30 nm or even below, electro-deposition of gold into narrow trenches replicated by electron beam lithography in resist becomes increasingly difficult. Pulse electroplating instead of conventional direct-current one has been attempted in this work to overcome the problem in the au deposition in narrow trenches. Careful study of the au deposition rate as the function of adjustment parameters including the anodic bias, the pulse frequency and the deposition time has been systematically carried out. The optimized window of the parameters is adopted in the fabrication of 30 nm zone plates with the aspect ratio from 3:1 up to 7:1 and the duty cycle close to 0.5. Imaging of in-house made Siemens stars with 30 nm as the narrowest line-width has been successfully demonstrated in soft X-ray (706 eV). The origin of electroforming of well-structured au zones by pulse electroplating is discussed

Event Stratigraphy in a Hadal Oceanic Trench: The Japan Trench as Sedimentary Archive Recording Recurrent Giant Subduction Zone Earthquakes and Their Role in Organic Carbon Export to the Deep Sea

Hadal trenches are the deepest places on Earth and are important foci for natural carbon sequestration. Much of the sedimentary sequences that accumulate within hadal trenches have been linked to widespread slope sediment remobilisation events, triggered by subduction zone earthquakes. Therefore, hadal trench deposits may provide valuable insights into the hazards posed by large earthquakes and their implications for the carbon cycle. Despite this strong societal relevance, no studies to date have provided the necessary coverage to understand the spatial and temporal variations of earthquake-triggered deposition along a hadal trench axis. We address these issues by integrating high-resolution bathymetry and subbottom profiler data, and sediment cores acquired over the entire hadal trench axis of the Japan Trench. We identify around 40 isolated trench-fill basins along the trench axis of the Japan Trench that document 115 sediment remobilization event deposits. We map the spatio-temporal distribution of the acoustically-transparent event deposit bodies imaged in subbottom profiler data from the trench-fill basins. Using radiocarbon dating, slope failure deposits identified from subbotom profiles and sediment coring were shown to be co-eval with major historic earthquake (e.g., AD2011 Mw9.0–9.1 Tohoku-oki, AD1454 Mw≥8.4 Kyotoku, and AD869 Mw≥8.6 Jogan events). Furthermore, the lower part of the acoustically-imaged stratigraphic succession in isolated basins along the Japan Trench also documents several thick acoustically-transparent bodies that relate to older events. These identifications of event deposits allow quantitative constraints of along-strike variation of sediment volumes redistributed by episodic events along the entire trench axis, revealing that the total volumes of event deposits triggered by different historic large earthquakes are highly variable. We conclude that at least 7 Tg (1012 g) of organic carbon remobilized from surficial slope sediments is exported to the hadal axis of Japan Trench in the last 2,000 years by giant earthquakes. These findings highlight the significance of seismo-tectonic events for the long-term carbon cycle in hadal trenches and societal implications.

Discovery of Middle Jurassic trench deposits in the Bangong-Nujiang suture zone: Implications for the timing of Lhasa-Qiangtang initial collision

The Mesozoic trench deposits in the Bangong-Nujiang suture zone in central Tibet can provide critical information for reconstructing the paleotectonic evolution of the Bangong-Nujiang Ocean and constraining the timing of the Lhasa-Qiangtang initial collision. In this paper, the Gamulong Formation, which is well exposed in the Dong Co area, western Bangong-Nujiang suture, central Tibet, was studied. The sedimentological analysis shows that the Gamulong Formation was deposited in a submarine fan environment. The youngest detrital zircon age and fossils from limestone pebbles within the Gamulong Formation combine to determine a Middle Jurassic age. The pebbles in the conglomerate are dominated by limestones and sandstones, which is consistent with the sandstone petrology showing limestone and sandstone fragments as the main framework components. Detrital zircon U-Pb ages from the sandstones yield age populations of 164–178 Ma, 200–500 Ma, 700–1000 Ma, 1700–2100 Ma and ~2500 Ma. The corresponding zircon εHf(t) values are distributed between −23.5 and +11.1. These zircon features are similar to those from the Qiangtang terrane. Accordingly, the provenance results imply that the Gamulong Formation was recycled from the accretionary complex (Mugagangri Group mélange) in the Bangong-Nujiang suture zone and the forearc basin deposits (Lower-Middle Jurassic Sewa/Shaqiaomu/Jiebuqu formations) in the southern Qiangtang subterrane. The Gamulong Formation is characterized by sedimentary recycling in the trench, likely in response to a tectonic event (possibly the continental collision). Together with the previous studies, this work on the occurrence of the Gamulong Formation indicates that the Lhasa-Qiangtang initial collision could have occurred in Middle Jurassic time (~166 Ma).

Tectonic setting for Tsunemori Formation in the Permian accretionary complex of the Akiyoshi Belt, Southwest Japan

The purpose of this study is to reexamine the age, depositional environment, and tectonic setting of the Tsunemori Formation. This study provides a new tectonic model on the formation of Tsunemori Formation, which is a key formation to understand the Late Permian subduction and accretionary processes in Japan. The sedimentation age of the Tsunemori Formation is late Middle Permian to early Late Permian, based on radiolarians, such as Follicucullus cf. scholasticus Ormiston and Babcock reported in this study. This paper disproves the previous theory of atoll carbonates collapse at the trench for the Akiyoshi Limestone. Most of sedimentary rocks of the Tsunemori Formation is not pervasively sheared, are less deformed compared with sedimentary rocks of the typical accretionary complexes. There is no layer parallel or sub-parallel thrusting in the turbidite sequences of the Tsunemori Formation. Mudstone of turbidite and pebbly mudstone is lack of fissility and scaly cleavages. The styles of deformation, occurrence of reworked fossils, presence of calcarenite and limestone breccia suggest that the Tsunemori Formation was not a part of accretionary wedges, but possibly was fore arc or slope basin deposits. Presence of reworked fossils, calcarenite, limestone breccia suggest that a part of the provenance of Tsunemori Formation are limestone exposed at the arc trench gap, which was moved upward to reach the arc trench gap where the Akiyoshi Limestone provides its fragments and blocks into forearc and/or slope basins. Therefore, Tsunemori Formation is a deposit in the forearc basin and/or slope basin rather than trench deposits.

Upper Cretaceous trench deposits of the Neo-Tethyan subduction zone: Jiachala Formation from Yarlung Zangbo suture zone in Tibet, China

The history of convergence between the India and the Asia plates, and of their subsequent collision which triggered the Himalayan orogeny is recorded in the Yarlung Zangbo suture zone. Exposed along the southern side of the suture, turbidites of the the Jiachala Formation fed largely from the Gangdese arc have long been considered as post-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous. To solve this conundrum, we carried out detailed stratigraphic, sedimentological, paleontological, and provenance analyses in the Gyangze and Sajia areas of southern Tibet, China. The Jiachala Formation consists of submarine fan deposits that lie in fault contact with the Zongzhuo Formation. Sandstone petrography together with U-Pb ages and Hf isotope ratios of detrital zircons indicate provenance from the Gangdese arc and central Lhasa terrane. Well preserved pollen or dinoflagellate cysts microfossils were not found in spite of careful research, and the youngest age obtained from zircon grain was ~ 84 Ma. Based on sedimentary facies, provenance analysis and tectonic position, we suggest that the Jiachala Formation was deposited during the Late Cretaceous (~88–84 Ma) in the trench formed along the southern edge of Asia during subduction of Neo-Tethyan oceanic lithosphere.

Discovery of Upper Cretaceous Neo-Tethyan trench deposits in south Tibet (Luogangcuo Formation)

Sedimentary basins within the Transhimalayan arc-trench system provide paleotectonic and paleogeographic information on the evolution of the late Mesozoic–early Cenozoic Neo-Tethyan subduction zone along the southern Asian margin. This paper presents detailed stratigraphic, sedimentologic, petrographic, detrital-zircon geochronologic and Hf isotopic data from the Luogangcuo Formation exposed as part of the Xiukang Mélange in south Tibet. The Luogangcuo Formation was deposited (ca. 88–81 Ma) in a trench environment on a deep-sea fan fed from the Lhasa block through a submarine canyon. Dominant chert and subordinate sandstone and limestone clasts in conglomerate beds indicate recycling from the Neo-Tethyan subduction complex during repeated episodes of gravitational failure. The interbedded turbiditic sandstones were sourced directly from the Gangdese magmatic arc and central Lhasa terrane. Detrital volumes from the active Asian margin increased markedly at ca. 88 Ma as a result of uplift of central Lhasa, leading to deltaic progradation, filling of the Xigaze forearc basin, and bypassing of sediments funneled via canyons across the subduction complex to reach the Luogangcuo trench basin at abyssal depths.

(Invited) Integration of III/V Hetero-Structures By Selective Area Growth on Si for Nano- and Optoelectronics

The integrated circuit (IC) technology has seen an impressive development over the last decades due to the superior interface properties between Silicon (Si) and Silicon dioxide. The main driving force for the constant improvement in microchip performance was an aggressive reduction in transistor device size. Currently this miniaturization of planar devices has reached physical limits and new device architectures are introduced and investigated such as FinFET, Gate-all-around nanowire devices and TFET. A further boost in device performance is expected from the implementation of new channel materials with higher electron mobilities than Si such as Germanium (Ge) or III/V compound materials. In addition, due to the excellent optoelectronic properties of III/V materials, the monolithic integration of III/V based hetero-structures on Si is a very promising route to clearly enhance Silicon Photonics. In particular the cost-efficient integration of a light source on Si substrate is still missing to fully profit from Silicon Photonics. Selective area growth (SEG) of lattice mismatched materials on patterned Si wafers is a novel integration approach with obvious advantages: Since most III/V candidates of interest have a larger lattice constant than Si, misfit and threading dislocations are formed to release the strain. SEG in very narrow oxide trenches allows for a pronounced defect reduction. The high aspect ratio of the oxide sidewalls leads to an efficient defect trapping in the bottom part of the trench so that the top region has a high crystal quality (aspect ratio trapping (ART)). Because thick metamorphic buffer growth is not required to adjust the lattice constant and to achieve a low defect density, SEG is also very cost-efficient and has a better compatibility with common CMOS integration schemes. The successful application of ART has already been demonstrated for numerous material systems in group IV as well as for III/V compound materials and opens several routes for implementing new device integration concepts. In this presentation we show the monolithic growth of GaAs nano ridges by metal organic vapor phase epitaxy (MOVPE) on 300mm patterned Si wafers. The deposition in narrow trenches ensures a clear reduction in defect density whereas the growth out of the trench is manipulated in such a way, that III/V ridges with increased volume and various shapes can be realized. The huge advantage of these nano ridges is that they provide a free standing lattice constant which can serve as a buffer for different pseudomorphically grown III/V hetero-structures. For example the growth of compressively strained InGaAs/GaAs multi quantum wells (MQWs) on a GaAs ridge offers an interesting approach for the monolithic integration of a laser diode, since the III/V nano ridge can also act as a wave guide. The impact of the chosen MOVPE growth parameters on the observed ridge evolution is discussed in detail based on scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction reciprocal space maps (XRD-RSM). The advantages and potentials of different hetero-structures on patterned wafers are assessed in view of new nano device applications in optoelectronics.

A paleoproterozoic intra-arc basin associated with a juvenile source in the Southern Brasilia Orogen: Application of U–Pb and Hf–Nd isotopic analyses to provenance studies of complex areas

Early Proterozoic sedimentary basins are an important record of crust generation processes and consequently a fundamental key to unraveling Earth's evolution through geological time. Sediments within the basins are typically deformed and metamorphosed by subsequent tectonothermal events, which can obliterate their links to source terranes. Nd-whole-rock and detrital zircon U–Pb and Lu–Hf isotopic analyses are among the most reliable tools to be used in provenance investigations, since zircon is a resilient mineral and the Sm–Nd system is not extensively modified during metamorphism. These methods have been applied to a study of the provenance and tectonic setting of the São Vicente Complex, preserved in a Neoproterozoic passive margin related allochthon within the Southern Brasilia Orogen. The complex consists of siliciclastic and calc-silicate gneisses with mafic and minor ultramafic rocks, which were deformed and metamorphosed during late Neoproterozoic collision between the Paranapanema Block and the São Francisco-Congo plate. Detrital zircons indicate derivation from a juvenile Paleoproterozoic source terrane (peaks of crystallization ages of ca. 2130Ma, 2140Ma and 2170Ma; ɛHft between +0.1 and +6.0; NdTDM=2.31–2.21Ga; ɛNdt=+1.6 to +2.8), with a minor contribution from older continental crust. Interlayered amphibolite rocks, with juvenile signatures (ɛHft=+5.8 to +8.2; NdTDM=2.14 and 2.30Ga; ɛNdt=+2.2 and +3.2), yielded similar ages of 2136±17 and 2143±14Ma, suggesting syn-sedimentary magmatism. Thus, the maximum age of deposition at around 2130Ma represents the best estimate of the depositional age of the complex. The dominance of detrital zircons ages close to the age of deposition, along with syn-sedimentary magmatism, imply a convergent margin basin tectonic environment for the São Vicente Complex, with similarities to fore arc basin and trench deposits. Amphibolite and meta-sedimentary rocks point to important juvenile magmatism around 2.14Ga. Juvenile Rhyacian (ca. 2.1Ga) granite-granodiorite-tonalite orthogneisses with arc-related geochemical signatures (Pouso Alegre Complex) that override the São Vicente Complex, are the probable main source of detritus within the complex. Both basin and source were part of the southern edge of the São Francisco plate during the assembly of West Gondwana, and served as sources for early Neoproterozoic passive margin related basins. The age of intrusive anorogenic A-type Taguar granite indicates that by 1.7Ga the São Vicente Complex was in a stable tectonic environment.

From convergent plate margin to arc–continent collision: Formation of the Kenting Mélange, Southern Taiwan

The Kenting Mélange on the Hengchun Peninsula, Taiwan, formed through tectonic shearing of subduction complex lithologies, probably within the plate boundary subduction channel between the Eurasian and Philippine Sea plates, with further deformation and exhumation in the Pliocene–Pleistocene during arc–continent collision. Field relations reveal a structural gradation from normal stratified turbidite sequence (Mutan Formation) through broken formation to highly sheared Kenting Mélange containing allochthonous polygenic blocks. This gradation is consistent with an increase of average vitrinite reflection values from ~0.72% in the Mutan Formation through ~0.93% in the broken formation to ~0.99% in the mélange, suggesting temperatures of at least 140°C during formation of the Kenting Mélange. Zircons from gabbro in the Kenting Mélange are dated as 25.46±0.18Ma, which together with geochemical data constrains the source to South China Sea oceanic lithosphere. In combination with the field relationships, vitrinite reflectance values, microfossil stratigraphy, and offshore geophysical data from S and SE Taiwan, we propose that the Kenting Mélange initially formed at the subduction plate boundary from off-scraped trench deposits. Minor Plio–Pleistocene microfossils (<5%) occur within the mélange in proximity to slope basin of equivalent age and were likely sheared into the mélange during out-of-sequence thrusting associated with active arc–continent collision, which in the Hengchun Peninsula commenced after 6.5Ma.

Franciscan mélanges: coherent blocks in a low-density, ductile matrix

ABSTRACTThe Franciscan Complex comprises the largely sedimentary basement of the California Coast Ranges. This classic trench deposit has undergone a series of superimposed tectonic events since the end of Jurassic time, involving accretion, high-pressure (HP) recrystallization, buoyancy and wedge-driven exhumation, and transcurrent slip. Processes reflect plate convergence, transpressive-orthogonal subduction, and transpressive–transtensive offset. Besides stratigraphically intact strata, the Franciscan displays widespread mélanges of four main types: diapiric serpentinite intrusions, sedimentary olistostromes, broken formations, and tectonic block-in-matrix units. In the northern Coast Ranges, mélanges are especially prevalent in the Central Belt, but also occur in the Eastern and Coastal belts. Diapirs show upward, buoyant flow relative to wall rocks, but some also appear to have involved wedge-driven thrusting. Many serpentinite diapirs and tectonic mélanges contain exotic metamafic inclusions rimmed by actinolite–chlorite reaction rinds. Olistostromes include gravity slump blocks and conglomeratic lenses; petrologically similar to larger slide blocks, pebble layers document a surficial, sedimentary origin, as does the presence of volcanic arc clasts. Broken formations grade by degrees from intact stratal continuity to disrupted units; they only contain cognate boudins of rocks present in the ductile matrix. Some tectonic mélanges are simply intensely disaggregated broken formations, and include rock types of the stratigraphic host. Other tectonic mélanges carry exotic HP blocks of diverse lithologies, generally reflecting higher pressures than attended recrystallization of the low-density matrix. The four mélange types formed through diverse convergent plate-tectonic processes. Many were subjected to a multi-stage overprint; most are strongly deformed, obscuring original textures and structures. Broken formations are the most common disrupted units, accompanied by lesser amounts of tectonic mélanges, olistostromes, and ductile-matrix diapirs. In aggregate, these units reflect the operation of contrasting processes that attest to plate-tectonic evolution of the Franciscan Complex. Strong deformation accompanied oceanic plate underflow, but also took place during coeval HP metamorphism and surfaceward return of accretionary packets, then transitioned to long-sustained, chiefly dextral slip.

Wafer level high-density trench capacitors by using a two-step trench-filling process

This paper reports on the design, fabrication and electrical characterization of high-density SIS trench capacitors by using a two-step deposition process for fast-filling the deep trenches. LPCVD silicon nitride is employed as the dielectric material to provide high efficiency deposition in the high aspect ratio trenches. The capacitance density in trench capacitors with 25 nm thick Si3N4 is characterized as high as 57.8 nF/mm2, while the breakdown voltage in trench capacitors with 35 nm thick Si3N4 is recorded to be as high as 14.5 V. Furthermore, the capacitances are measured over an applied voltage range from ź5 to 5 V, showing a small voltage-dependence of 1.2 and 0.6 % Vź1 for the 25 and 35 nm thick Si3N4 trench capacitor, respectively. The leakage currents are measured and the current transport mechanisms are analyzed. The ESR and ESL of the capacitors with 25 and 35 nm thick Si3N4 are very small, as low as 35---65 mΩ and 0.2---0.28 pH for 0.04 mm2 electrode surface.

Review of Late Jurassic-early Miocene sedimentation and plate-tectonic evolution of northern California: illuminating example of an accretionary margin

Production of voluminous igneous arc rocks, high-pressure/low-temperature (HP/LT) metamafic rocks, westward relative migration of the Klamath Mountains province, and U–Pb ages of deposition, sediment sources, and spatial locations of Jurassic and younger, detrital zircon-bearing clastic rocks constrain geologic development of the northern California continental edge as follows: (1) At ~175 Ma, transpressive plate underflow began to generate an Andean-type Klamath-Sierran arc along the margin. (2) Oceanic crustal rocks were metamorphosed under HP/LT conditions in an inboard, east-inclined subduction zone from ~170-155 Ma. Except for the Red Ant blueschists, such lithologies remained stored at depth; most HP/LT mafic tectonic blocks returned surfaceward only during mid- and Late Cretaceous time, chiefly entrained in circulating, buoyant Franciscan mud-matrix melange. (3) By ~165 Ma and continuing to ~150-140 Ma, erosion supplied volcanogenic debris to proximal Mariposa-Galice ± Myrtle overlap strata. (4) At ~140, immediately prior to the onset of paired Franciscan and Great Valley Group (GVG) + Hornbrook deposition, the Klamath salient was deformed and displaced ~100–150 km westward relative to the Sierran arc, stranding pre-existing oceanic crust on the south as the Coast Range Ophiolite (CRO). (5) After the end-of-Jurassic seaward step-out of the Farallon-North American convergent plate junction, terrigineous debris began to be deposited in the outboard Franciscan trench and intervening Great Valley forearc. (6) Voluminous sedimentation and accretion of Franciscan Eastern + Central belts and GVG detritus took place during paroxysmal igneous activity and rapid, nearly orthogonal plate convergence at ~125-80 Ma. (7) Sierran arc volcanism-plutonism ceased by ~80 Ma in northern California, signaling a transition to shallow, nearly subhorizontal eastward plate underflow attending Laramide orogeny far to the east. (8) Presently exposed Paleogene-lower Miocene Franciscan Coastal Belt sedimentary strata were deposited in a tectonic realm unaffected by HP/LT subduction. (9) Grenville-age detrital zircons are absent from the post-120 Ma Franciscan section. (10) Judging from petrofacies and zircon U–Pb data, the Franciscan Eastern Belt contains debris derived principally from the Sierra Nevada and Klamath ranges; detritus from the Idaho Batholith as well as Sierra Nevada Batholith may be present in some Central Belt sandstones, whereas clasts from the Idaho Batholith, Challis volcanics, and Cascade Range appear in progressively younger Paleogene-lower Miocene Coastal Belt sediments. (11) Gradual NW dextral offset of the Franciscan trench deposits of as much as ~1,600 km may have occurred relative to the native GVG forearc and basement terranes of the American Southwest.

New interpretation of the Franciscan mélange at San Simeon coast, California: tectonic intrusion into an accretionary prism

Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes.