Trench Direction Research Articles

The Effect of Laser Ablation Pulse Width and Feed Speed on Necrosis and Surface Damage of Cortical Bone

Bone cutting is of importance in orthopaedic surgery but is also challenging due to its nature of brittleness—where severe mechanical and thermal damages can be introduced easily in conventional machining. Laser machining is a new technology that can allow for complex cut geometries whilst minimising surface defects i.e., smearing, which occur in mechanical methods. However, comparative studies on the influence of lasers with different pulse characteristics on necrotic damage and surface integrity have not been reported yet. This paper for the first time investigates the effects of laser type on the necrotic damage and surface integrity in fresh bovine cortical bone after ex-situ laser machining. Three lasers of different pulse widths, i.e., picosecond, nanosecond and continuous wave lasers have been investigated with different feed speeds tested to study the machining efficiency. The cutting temperature, and geometrical outputs have been measured to investigate the thermal influence on the cooling behaviour of the bone samples while high-speed imaging was used to compare the material removal mechanisms between a pulsed and continuous wave laser. Furthermore, an in-depth histological analysis of the subsurface has revealed that the nanosecond laser caused the largest necrotic depth, owing to the high pulse frequency limiting the dissipation of heat. It has also been observed that surface cracks positioned perpendicular to the trench direction were produced after machining by the picosecond laser, indicative of the photomechanical effect induced by plasma explosions. Therefore, the choice of laser type (i.e., in terms of its pulse width and frequency) needs to be critically considered for appropriate application during laser osteotomy with minimum damage and improved healing.

Crystal-orientation-dependent flatband voltage of non-polar GaN MOS interfaces investigated using trench sidewall capacitors

We systematically characterized gallium nitride (GaN) metal-oxide semiconductor interfaces formed on trench sidewalls, paying particular attention to eliminating the parasitic capacitance caused by the trench bottom. The flatband voltage (Vfb) was found to be clearly higher on the m-face trench than on the a-face trench, and an interface state density of ∼1 × 1011 cm−2 eV−1 near the conduction band edge was achieved, irrespective of the trench direction. For trench sidewalls treated with a tetramethyl ammonium hydroxide (TMAH) solution, variation in Vfb among the trench direction was suppressed, reflecting that microscopic m-faces were generated after the TMAH treatment, irrespective of the direction of the trench. Therefore, the origin of the Vfb variation was attributed to the GaN crystal face dependence of fixed charge density at SiO2/GaN interfaces.

Lineament Assessment of Aynak Copper mine using Remote Sensing approach

This research developed a new approach to extract the lineaments using Landsat, QuickBird and ALOS PALSAR satellite remotely sensed data in Aynak copper mine which is located in Kabul tectonic block and the Tethyan Copper Belt of Afghanistan. Lineaments and trench directions are not relatively studied in the study area which will bring obstacles in exploration and extraction of the mine. This research aims to extract the lineaments for studying the better trench direction in the study area. Lineaments such as faults and joints are extremely important structures that not only show the surface structure but also give us important knowledge about the subsurface of the earth. Afghanistan is a part of the Alpine-Himalayan orogenic belt which suffers from high tectonic movements in some areas, especially north-eastern and central parts which leads to the occurrence of different lineaments and unconformities. Lineaments can be surveyed and mapped using field geological survey or using satellite remotely sensed data. Satellite remote sensing data costs less and takes less time compare to field geological survey for lineament extraction. This research used Landsat 8 natural color with 2, 3, 4 band composition, QuickBird 1m resolution, and ALOS PALSAR 12.5 m satellite imagery to detect and map the lineaments in the Aynak copper mine area in Afghanistan. Geomatica software was used for lineament extraction using the Manual technique. Then the rose diagrams of the lineaments were plotted using Polar Plots extension of ArcGIS. Next, the rose diagrams derived from the two mentioned lineament extraction techniques were compared and evaluated. Global Mapper software was used for the extraction of lineaments using Visual technique and to map the rivers and ridges in the Aynak area of interest for validation of the results. Finally, the best orientation for trenches in Aynak copper mine was derived. This study found that faults and joints in the study area have a NE-SW trend and directions. This study will contribute to a better understanding of the trench direction and mineral exploration in Aynak copper mine.

Experimentally deformed lawsonite at high pressure and high temperature: Implication for low velocity layers in subduction zones

Lawsonite is considered to be one of the most likely hydrous minerals to explain the persistence of seismic low-velocity layers (LVLs) atop subducted slabs to depths of 100–250 km due mainly to the fact that it can persist to these depths, in contrast to other hydrous minerals such as antigorite. However, as it is highly anisotropic and subjected to intense deformation during subduction, further constrains on the development of lawsonite crystal preferred orientation (CPO) at high pressure and temperature are required in order to evaluate its role in slowing seismic waves. We have deformed lawsonite aggregates at 5 GPa and 500–800 °C corresponding to 150 km depth and covering temperatures for both cold and hot subduction zones. In this study, we report a new lawsonite CPO pattern resulting from dislocation creep deformation that has not been previously observed. The [100] axes concentrate into the shear direction and the [010] axes are normal to the shear plane, respectively (we refer to this as “type-1” CPO). Such CPO is consistent with our transmission electron microscope (TEM) observations identifying (010)[100] as a dominant dislocation slip-system. The seismic properties resulting from this CPO show the fast P-wave direction to be parallel to the shear direction, and the slow P-wave direction and maximum S-wave anisotropy normal to the shear plane. We performed calculation of omphacite-lawsonite aggregates using our experimental data and varied both the lawsonite contents and the slab dipping angle. Our results show that a reasonable amount of lawsonite can explain Vs reduction in the LVLs, but cannot explain the Vp reduction. However, the presence of lawsonite would induce a rotation of the fast S-wave polarization toward the trench direction as the S-wave anisotropy increases or decreases according to the lawsonite proportion, its CPO strength and the slab dipping angle. We believe that our calculation can now be used for investigation of lawsonite effect in various subductions zones.

Fluid Distribution in the Central Andes Subduction Zone Imaged With Magnetotellurics

AbstractWe present a model of the electrical resistivity structure of the lithosphere in the Central Andes between 20° and 24°S from 3‐D inversion of 56 long‐period magnetotelluric sites. Our model shows a complex resistivity structure with significant variability parallel and perpendicular to the trench direction. The continental forearc is characterized mainly by high electrical resistivity (>1,000 Ωm), suggesting overall low volumes of fluids. However, low resistivity zones (LRZs, <5 Ωm) were found in the continental forearc below areas where major trench‐parallel faults systems intersect NW‐SE transverse faults. Forearc LRZs indicate circulation and accumulation of fluids in highly permeable fault zones. The continental crust along the arc shows three distinctive resistivity domains, which coincide with segmentation in the distribution of volcanoes. The northern domain (20°–20.5°S) is characterized by resistivities >1,000 Ωm and the absence of active volcanism, suggesting the presence of a low‐permeability block in the continental crust. The central domain (20.5°–23°S) exhibits a number of LRZs at varying depths, indicating different levels of a magmatic plumbing system. The southern domain (23°–24°S) is characterized by resistivities >1,000 Ωm, suggesting the absence of large magma reservoirs below the volcanic chain at crustal depths. Magma reservoirs located below the base of the crust or in the backarc may fed active volcanism in the southern domain. In the subcontinental mantle, the model exhibits LRZs in the forearc mantle wedge and above clusters of intermediate‐depth seismicity, likely related to fluids produced by serpentinization of the mantle and eclogitization of the slab, respectively.

Manipulation of dipolar magnetism in low-dimensional iron oxide nanoparticle assemblies.

The manipulation of magnetic states in nanoparticle supercrystals promises new pathways to design nanocrystalline magnetic materials and devices. Trench-patterned silicon substrates were used as templates to guide the self-assembly of iron oxide nanoparticles. Grazing incidence small angle X-ray scattering shows that the nanoparticles form a long-range ordered structure along the trench direction while in the direction perpendicular to the trenches, no coherent structure is observable. Electron holography provides evidence of an ordered magnetic state of nanoparticle moments in the remanent state after the application of a saturation magnetic field parallel to the trenches. However, a disordered magnetic state was observed in a perpendicular geometry. Hysteresis loops indicate that the nanoparticle moments form a superferromagnetic state for the geometry parallel to the trenches. Memory effect investigations reveal that the disordered magnetic state corresponds to a collective superspin glass state in the perpendicular geometry, while the superferromagnetic state in the parallel geometry suppresses the superspin glass state.

Orthogonally Aligned Block Copolymer Line Patterns on Minimal Topographic Patterns.

We demonstrate the generation of block copolymer (BCP) line patterns oriented orthogonal to a very small (minimal) topographic trench pattern over arbitrarily large areas using solvent-vapor annealing. Increasing the thickness of BCP films induced an orthogonal alignment of the BCP cylindrical microdomains, where full orthogonal alignment of the cylindrical microdomains with respect to the trench direction was obtained at a film thickness corresponding to 1.70 L0. A capillary flow of the solvent across the trenches was a critical factor in the alignment of the cylindrical microdomains. Grazing incidence small-angle X-ray scattering was used to determine the orientation function of the microdomains, with a value of 0.997 being found reflecting a nearly perfect orientation. This approach to produce orthogonally aligned BCP line patterns could be extended to the nanomanufacturing and fabrication of hierarchical nanostructures.

Strong impact of slight trench direction misalignment from on deep trench filling epitaxy for SiC super-junction devices

A trench filling epitaxial growth technique using hot-wall chemical vapor deposition with HCl gas has been developed for SiC super-junction (SJ) device fabrication. 2–6 kV class SJ devices require p/n column structures with depths of over 10 µm. However, rapid trench closure before the trench backfilling process is complete makes these structures difficult to realize. Stripe trenches that were intentionally inclined within ±2° on a surface plane towards the direction were formed on an off-angled wafer, and the effects of trench direction misalignment from the off-direction were investigated. Slight trench direction misalignment was found to affect the tilt angle of the mesa top epi-layer strongly. Tilted growth on the mesa top reduced the filling rate at the trench bottom and caused void formation. When a wafer with high orientation-flat accuracy relative to the direction was used, 25-µm-deep trench backfilling was successfully demonstrated.

GaAs on Si epitaxy by aspect ratio trapping: Analysis and reduction of defects propagating along the trench direction

The Aspect Ratio Trapping technique has been extensively evaluated for improving the quality of III-V heteroepitaxial films grown on Si, due to the potential for terminating defects at the sidewalls of SiO2 patterned trenches that enclose the growth region. However, defects propagating along the trench direction cannot be effectively confined with this technique. We studied the effect of the trench bottom geometry on the density of defects of GaAs fins, grown by metal-organic chemical vapor deposition on 300 mm Si (001) wafers inside narrow (<90 nm wide) trenches. Plan view and cross sectional Scanning Electron Microscopy and Transmission Electron Microscopy, together with High Resolution X-Ray Diffraction, were used to evaluate the crystal quality of GaAs. The prevalent defects that reach the top surface of GaAs fins are {111} twin planes propagating along the trench direction. The lowest density of twin planes, ∼8 × 108 cm−2, was achieved on “V” shaped bottom trenches, where GaAs nucleation occurs only on {111} Si planes, minimizing the interfacial energy and preventing the formation of antiphase boundaries.

Reliability Improvement and Optimization of Trench Orientation of 4H-SiC Trench-Gate Oxide

Reliability of gate oxide for trench-gate MOSFET was improved by deposited oxide film with uniform thickness and high-temperature annealing after trench etching. Optimum wafer orientation and trench direction for the trench gate was investigated, and the gate oxide on (11-20) plane of carbon face exhibited the longest lifetime. Influences by the roughness of sidewall and the radius of trench corner are discussed.

Block Copolymer Morphology Formation on Topographically Complex Surfaces: A Self-Consistent Field Theoretical Study

A self-consistent field theoretic study is performed to study morphological development of lamellae-forming diblock copolymers on substrates with a well-defined roughness, modeled as trenches of varying depth and width engraved into the substrates. There are three possible lamellar orientations observed: horizontal lamellae, vertical lamellae that are parallel to the trench direction, and vertical lamellae that are perpendicular to the trench direction. Which of these three morphologies formed depends upon the trench width and surface affinity; however, trench depth has a relatively insignificant effect on the morphological development. Therefore, tuning trench width, but not trench depth, should allow for a reduction of the morphological defect density in directed self-assembly of lamellar morphology of diblock copolymers.

Strain evolution during the growth of epitaxial Ge layers between narrow oxide trenches

We have grown the high quality and compressively strained Ge epilayers on a Si substrate with 40-nm width SiO2 trench patterns at a growth temperature of 600°C. Based on (224) reciprocal space mapping measurements of Ge samples with a different thickness, the residual in-plane strain value along the trench direction decreased from −0.74% to −0.42% with increasing thickness of the Ge layer from 150 nm to 180 nm. In addition, the compressive strain along the trench direction (ε1¯10) was larger than that in the direction perpendicular to the trench (ε110) regardless of the thickness. For example, when Ge was overgrown on a SiO2 trench, the ε1¯10 and ε110 values were −0.42% and ~0%, respectively. We conclude that the asymmetric strain relaxation behavior of Ge is related to the SiO2 trench patterns, which prevent the dislocations from gliding. Defects such as a microtwin and/or stacking fault were generated during the coalescence of Ge films having different lattice constants in each Ge layer arising from the different relaxation values. A local strain in Ge, with a high spatial resolution of 2.5nm, was measured along the two directions by means of a nanobeam electron diffraction method, thus confirming asymmetric strain relaxation and the results are in good agreement with reciprocal space mapping results.

Tsunami source of the 2011 Tohoku earthquake detected by an ocean-bottom magnetometer

Tsunami-induced magnetic signals resulting from the 11 March 2011 Tohoku earthquake (M 9.0) were identified from an examination of the record of an ocean-bottom electromagnetometer emplaced 50 km east of the Japan Trench. The impulsive variation of the vertical magnetic field component directly indicates the tsunami wave height and arrival time at the station. The impulsive variation of the horizontal magnetic components indicates east–southeast as the tsunami-propagation direction. These data indicate that the tsunami source was located along the Japan Trench at approximately 39.0°N latitude, which is about 100 km northeast from the main rupture area. Joint analysis of the observed magnetic variations and offshore sea-level data supports this source location and indicates that the tsunami origin time was about 1 min after the earthquake origin time. In addition, the magnetic field variation and the sea level change indicate that the source area was elongated in the trench direction and had a narrow width.

Selective epitaxial growth of compressively strained Ge layers on Si in 40-nm trench arrays

We investigated the growth of the epitaxial Ge layers in a 40nm wide SiO2 trench array on Si by ultra-high vacuum chemical vapor deposition. If the thickness of Ge was less than the height of the SiO2 trenches, the Ge layers grew epitaxially by a selective epitaxial growth process without any detectable surface modification, which is due to the high interfacial energy between the SiO2 mask and Ge. We calculated the critical strain required to modify the Ge surface via 3-dimensional island transition (the minimum strain) as a function of the trench width. Considering the energies involved in the transition, we found that uniformly shaped Ge layers along the trenches were energetically more favorable than those with surface undulations as the width of the trench decreased. The strained Ge epilayers relaxed their energy by forming the defects, such as dislocations at the Ge/Si interfaces and stacking faults. From the strain analyses, the residual strains for parallel and perpendicular to the trench direction in the Ge layers were −0.72% and −0.22%, respectively.

Fluidic aligned, dense SWNTs arrays as potential die adhesive and thermal interface material

PurposeThe purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single‐walled carbon nanotubes (SWNTs) between a chip and its substrate acting as a kind of thermal interface material by virtue of better mechanical and thermal properties.Design/methodology/approachTwo silicon chips, with shallow trenches about 2 μm deep on the surface, were pressed together face to face with the trench direction perpendicular to each other. SWNT aqueous solution was driven into the gap between the two chips by capillary force. Later, the sample was baked to remove the moisture completely.FindingsSWNTs beams were found to be assembled in the gap and have their two ends bonding with the interface of the two chips, respectively. The shear strength of the two chips was measured, and the thermal conductivity of the stacked chip‐SWNTs‐chip was tested using a laser flash method. In result, shear strength up to about 100 kPa, and an average thermal conductivity of 19.3 W·m−1·K−1 were demonstrated.Originality/valueThe paper proposes an approach to grown dense SWNT array bridging a chip and its substrate, and these SWNTs have potential capability to provide mechanical strength and higher thermal conductance instead of commercial thermal interface materials.

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes

In order to reproduce slow earthquakes with short duration such as very low frequency events (VLFs) migrating along the trench direction as swarms, we apply a 3-D subduction plate boundary model based on the slowness law of rate- and state-dependent friction, introducing close-set numerous small asperities (rate-weakening regions) at a depth of 30 km under high pore pressure condition, in addition to a large asperity. Our simulation indicates that swarms of slip events occur repeatedly at the small asperities, and these events are similar to the observed slow earthquake group, especially to VLF, on the basis of the relation between characteristic duration and seismic moment. No slip events occur there without the small asperities, which mean that the close-set numerous small asperities may be one of the necessary conditions for generating the short-duration slow earthquakes such as VLFs. In the preseismic stage of the megathrust earthquakes that occur at the large asperity, the swarms of VLFs have higher migration speeds and higher moment release rate as well as shorter recurrence interval. Thus, monitoring the migration of slow earthquakes may be useful in imaging the preseismic slip of megathrust earthquakes.

Fabrication of crack‐free thick AlN film on a‐plane sapphire by low‐pressure HVPE

AbstractThe periodic trench patterning of sapphire substrates is useful for the growth of crack‐free AlN thick films. However, the in‐plane epitaxial relationship between AlN and a‐plane sapphire depends on the initial growth temperature. Therefore, two trench directions, the <0001>a‐plane sapphire and <1‐100>a‐plane sapphire directions are investigated in this study. We investigated the control of in‐plane epitaxial relationship between AlN and a‐plane sapphire by low‐pressure HVPE and the effect of the trench direction of AlN, which results in two different in‐plane epitaxial relationships on a‐plane sapphire (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Mimicking nanoribbon behavior using a graphene layer on SiC

We propose a natural way to create quantum-confined regions in graphene in a system that allows large-scale device integration. We show, using first-principles calculations, that a single graphene layer on a trenched region of $[000\bar{1}]$ $SiC$ mimics i)the energy bands around the Fermi level and ii) the magnetic properties of free-standing graphene nanoribbons. Depending on the trench direction, either zigzag or armchair nanoribbons are mimicked. This behavior occurs because a single graphene layer over a $SiC$ surface loses the graphene-like properties, which are restored solely over the trenches, providing in this way a confined strip region.

Growth of Metal Nanowhiskers on Patterned Substrate by High Temperature Glancing Angle Deposition

In this study, we carry out high temperature glancing angle deposition (HT-GLAD) of Fe and Al on a heated substrate with trench patterns. When vapor is incident perpendicular to the trench direction, nanowhiskers grow only on the surface exposed to the vapor and not inside the trenches. When vapor is incident at a deposition angle larger than 80° on the sidewall of the trench and not on the substrate surface, nanowhiskers grow only on the sidewall because the condition of deposition at a high temperature and a large deposition angle is satisfied only for the sidewall. Thus, we succeed in the selective growth of nanowhiskers by controlling the geometrical deposition conditions. Further, we also discuss the effect of the local deposition geometry on the growth process. Geometrically selective growth by HT-GLAD is expected to be useful for growing nanowhiskers on nano- and microstructured substrates.

Systematic variation in anisotropy beneath the mantle wedge in the Java–Sumatra subduction system from shear-wave splitting

The tectonic context of south-east Asia is dominated by subduction. One such major convergent boundary is the Java-Sunda trench, where the Australian–Indian plates are being subducted beneath the Eurasian plate. We measure shear-wave splitting in local and teleseismic data from 12 broadband stations across Sumatra and Java to study the anisotropic characteristics of this subduction system, which can provide important constraints on dynamical processes involved. Splitting in S -waves from local earthquakes between 75 and 300 km deep show roughly trench parallel fast directions, and with time-lags 0.1–1.3 s (92% ≤ 0.6 s). Splitting from deeper local events and SKS, however, shows larger time-lags (0.8–2.0 s) and significant variation in fast direction. In order to infer patterns of deformation in the slab we apply a hybrid modelling scheme. We raytrace through an isotropic subduction zone velocity model, obtaining event to station raypaths in the upper mantle. We then apply appropriately rotated olivine elastic constants to various parts of the subduction zone, and predict the shear-wave splitting accrued along the raypath. Finally, we perform grid searches for orientation of deformation, and attempt to minimise the misfit between predicted and observed shear-wave splitting. Splitting from the shallow local events is best explained by anisotropy confined to a 40 km over-riding plate with horizontal, trench parallel deformation. However, in order to explain the larger lag times from SKS and deeper events, we must consider an additional region of seismic anisotropy in or around the slab. The slab geometry in the model is constrained by seismicity and regional tomography models, and many SKS raypaths travel large distances within the slab. Models placing anisotropy in the slab produce smaller misfits than those with anisotropy outside for most stations. There is a strong indication that inferred flow directions are different for sub-Sumatran stations than for sub-Javanese, with >60 ° change over ∼ 375 km. The former appear aligned with the subduction plate motion, whereas the latter are closer to perpendicular, parallel to the trench direction. There are significant differences between the slab being subducted beneath Sumatra, and that beneath Java: age of seafloor, maximum depth of seismicity, relative strength of the bulk sound and shear-wave velocity anomaly and location of volcanic front all vary along the trench. We speculate, therefore, that the anisotropy may be a fossilised signature rather than due to contemporary dynamics.