Crystalline Target Research Articles

Determination of recombination radius in Si for binary collision approximation codes

Displacement damage caused by ions or neutrons in microelectronic devices can have significant effect on the performance of these devices. Therefore, it is important to predict not only the displacement damage profile, but also its magnitude precisely. Analytical methods and binary collision approximation codes working with amorphous targets use the concept of displacement energy, the energy that a lattice atom has to receive to create a permanent replacement. It was found that this “displacement energy” is direction dependent; it can range from 12 to 32eV in silicon. Obviously, this model fails in BCA codes that work with crystalline targets, such as Marlowe. Marlowe does not use displacement energy; instead, it uses lattice binding energy only and then pairs the interstitial atoms with vacancies. Then based on the configuration of the Frenkel pairs it classifies them as close, near, or distant pairs, and considers the distant pairs the permanent replacements. Unfortunately, this separation is an ad hoc assumption, and the results do not agree with molecular dynamics calculations. After irradiation, there is a prompt recombination of interstitials and vacancies if they are nearby, within a recombination radius. In order to implement this recombination radius in Marlowe, we used the comparison of MD and Marlowe calculation in a range of ion energies in single crystal silicon target. The calculations showed that a single recombination radius of ∼7.4Å in Marlowe for a range of ion energies gives an excellent agreement with MD.

Sedimentation in marine impact craters — Insight from the Ritland impact structure

This paper is intended to compare the sedimentary processes active in the Ritland impact structure with the processes discussed from Gardnos, Kärdla, Lockne and Chesapeake Bay marine impact structures. Sedimentary processes, e.g., rock avalanches, slides and slumps, debris and density flows, turbidity and suspension deposition, occur approximately in the same stratigraphical order in all these craters, resulting in comparable crater-infills. The thickness and compositional variations can be explained by differences in crater size, target lithology and water depth. Rock avalanches dominate in crystalline target impact sites with shallow water depth, as observed in the Ritland and Gardnos craters. Impact into deeper water, e.g., Lockne, does not reveal large-scale gravity-driven collapses of the transient sea floor cavity. Crystalline target sites with shallow water depth and thin sedimentary cover, as in the Ritland and Gardnos impact sites, resulted in elevated rim formations, reducing resurge energy, and yielded comparable reduced debris flow events. Impact into thick, stratified sedimentary targets resulted in relatively weaker rim formation in Kärdla. The related brim developments in the Lockne and Chesapeake Bay impact structures can be reflected in multiple events of large-scale debris flows. Resurge turbidites are observed in the Kärdla and Lockne crater infilling successions. Turbidites in the Ritland and Gardnos are dominantly originated through later slope-failure and reworking of the impact-generated debris. Suspension-dominated late post-impact sedimentation within all the craters is largely controlled by their regional geological settings.

Homoepitaxial growth of ZnO films with reduced impurity concentrations by helicon-wave-excited-plasma sputtering epitaxy using a crystalline ZnO target prepared by hydrothermal technique

Homoepitaxial growth of reduced donor concentration ZnO films exhibiting atomically smooth surface is demonstrated by helicon-wave-excited-plasma sputtering epitaxy. Using a crystalline ZnO target prepared by hydrothermal method, concentrations of B, C, Cr, Li, and Si in the films underran the detection limits of secondary-ion-mass spectrometry. Consequently, low temperature photoluminescence spectra were dominated by sharp emission peaks originating from the recombination of excitons bound to a neutral Al donor, of which concentration was 2 × 1016 cm−3. Nonradiative lifetime dominated the recombination process above 50 K, which is most likely due to the presence of lifetime killers such as Ni and Fe.

Ultra-thin engraved 3D taper structure in a crystalline material using FIB

Focused ion beam milling has been applied to fabricate an ultra-thin taper structure on crystalline indium phosphide to realize a multi-wavelength vertical cavity photonic device. The appropriate FIB scanning procedures and operating parameters were used to control the target material re-deposition and to minimize the surface roughness of the milled area. The sputtering yield of crystalline indium phosphide target was determined by investigating the relationship between milling depth and ion dose. By applying the optimal experimentally obtained yield and related dose range, we have fabricated an ultra-thin taper structure whose etch depths are precisely and progressively tapered from 25nm to 55nm, with a horizontal slope of about 1:13,000. The optical characterization of this tapered device confirms the expected multi-wavelength behavior of our device and shows that the optical losses induced by the FIB milling process are negligible.

Self-assembled 1,2-bis[4-(4-(10-decyloxy)phenylazo)]benzoylhydrazine dimer and its hydrogen-bonded complexes

We report the synthesis and investigation of a new self-assembled benzoylhydrazine-based compound, namely 1,2-bis[4-(4-(10-decyloxy)phenylazo)]benzoylhydrazine and their hydrogen-bonded complexes with different carboxylic acid derivatives, of which some exhibit liquid crystalline properties and some are non-mesogens. The conversion of the non-liquid crystalline target compound that is free from carboxylic acid to liquid crystalline complexes containing various carboxylic acids can probably be rationalised through the breaking of intermolecular hydrogen bonding within the supramolecular assembly by carboxylic acid dopants. The enhancement of liquid crystalline properties of benzoylhydrazine compounds with respect to various carboxylic dopants is documented. Other salient features can be exemplified by the formation of discotic columnar phase as shown by the azo-linkage containing 4-(4′-(10-decyloxy)phenylazo)benzoic acid-doped complex.

The effects of meteorite impacts on the availability of bioessential elements for endolithic organisms

Abstract– Meteorite impacts, one of the most ubiquitous processes in the solar system, have the ability to destroy as well as create habitats for life. The impact process can increase the translucency and porosity of the target substrate, as well as mobilize biologically relevant elements within the substrate. For endolithic organisms, this process has important implications, especially in extreme environments where they are forced to seek refuge in the interior of rocks. Here, we show that unshocked target rocks and rocks that have experienced pressures up to about 80 GPa from the Haughton impact structure, Devon Island, Canada, possess a small, but discernible change in bulk chemistry within the major oxide analysis. However, changes in the distribution of elements did occur with increasing shock level for both the sedimentary and crystalline target. Both the crystalline and sedimentary target rocks contain significant amounts of glasses at higher shock levels (up to about 95% by volume), which would improve the availability of these elements to potential microbial endoliths as glasses are more easily dissolved by organic acids. The implication that impact events do not impoverish their capacity to serve as a “substrate” through volatilization is important with respect to analogous impact structures on Mars. After the deleterious effects of the direct meteorite impact, any microorganisms on Mars would have benefited from the input of heat, the mobilization of a possible frozen groundwater system, as well as increased translucency, porosity, and trace nutrient availability of the target substrate.

Seismic properties of the Voisey’s Bay massive sulfide deposit: Insights into approaches to seismic imaging

Seismic methods offer significant potential advantages for minerals exploration over more traditional geophysical techniques because of the comparatively high resolution of seismic imaging. This is particularly true as minerals exploration is required to explore deeper to find resources. However, adaptation of seismic imaging techniques to the complex crystalline targets common in the mining environment requires a thorough understanding of the physical properties of the specific combination of ore and host rocks under consideration to choose an appropriate imaging technique. Analysis of the sulfide ores and associated host rocks from the Voisey’s Bay nickel-copper-cobalt deposit indicates that in the pyrrohotite-pentlandite-rich but pyrite-poor assemblage at Voisey’s Bay, seismic velocities are significantly lower ([Formula: see text]) than either the felsic or mafic host rocks ([Formula: see text] and [Formula: see text]). This observation is in contrast with pyrite-rich massive sulfide ores that have velocities that are significantly higher than typical host rocks. The large velocity contrast between the Voisey’s Bay ores and their host rocks makes them good targets for tomographic imaging. However, due to the trade-off between the low velocities and high densities of the Voisey’s Bay sulfides, acoustic impedance contrasts can be quite modest making them less attractive for seismic reflection imaging. Detailed analysis of two different mineralized zones at Voisey’s Bay further demonstrated that, depending on the limiting signal-to-noise ratio, the choice of an effective seismic imaging technique is not universal across a mineral deposit and may be affected by subtle variations in sulfide mineralogy and by the structural/magmatic setting. Our analysis clearly indicated that knowledge of physical properties and geologic setting is critical to the choice of which seismic technique to apply in a given exploration setting.

Independence of interrupted coarsening on initial system order: ion-beam nanopatterning of amorphous versus crystalline silicon targets

Interrupted coarsening (IC) has recently been identified as an important feature for the dynamics of the typical length-scale in pattern-forming systems on surfaces. In practice, it can be beneficial to improve pattern ordering since it combines a certain degree of defect suppression with a limited increase in the typical pattern wavelength. However, little is known about its robustness with respect to changes in the preparation of the initial system for cases with potential applications. Working in the context of nano-scale pattern formation by ion-beam sputtering (IBS), we prove that IC properties do not depend on sample preparation. Specifically, interface dynamics under IBS is quantitatively compared on virgin amorphous and crystalline silicon surfaces, using 1 keV Ar+ ions at normal incidence where nanodot pattern formation is triggered by concurrent co-deposition of Fe atoms during processing. Atomic force microscopy shows that dot patterns with similar spatial order and dynamics are obtained in both cases, underscoring the key dynamical role of the amorphous surface layer produced by irradiation. Both systems have been quantitatively described by an effective interface equation. We employ a new procedure based on the linear growth of the initial surface correlations to accurately estimate the equation coefficients. Such a method improves the predictive power of the interface equation with respect to previous studies and leads to a better description of the experimental pattern and its dynamical features.

Monitoring the formation of inorganic fullerene-like MoS2 nanostructures by laser ablation in liquid environments

Laser ablation of solid targets in liquid media is emerging as a simple, clean and reproducible way to generate a large number of intriguing nanometric structures with peculiar properties. In this work we present some results on the formation of MoS2 fullerene-like nanoparticles (10–15nm diameter) obtained by the ablation of crystalline targets in water. Such a top–down approach can be considered greener than standard sulphidization reactions and represents an intriguing single step procedure. The generation of the MoS2 nanostructures is in competition with that of oxide clusters and strongly depends on the oxidative environment created by the plasma plume. The size, shape and crystalline phase of the obtained nanoparticles are studied by microscopy while X-Ray Photoelectron Spectroscopy is used to investigate the chemical state of produced nanostructures and to propose mechanisms for their growth.

The Mean Projected Range and Range Straggling of Er Ions Implanted in 6h Silicon Carbide

Due to the need to reduce electronic device sizes, it is very important to consider the depth distribution of ions implanted into a crystalline target. The mean projected ranges and range straggling for energetic 200-500 keV Er ions implanted in 6H-SiC were measured by means of Rutherford backscattering followed by spectrum analysis. The measured values are compared with Monte Carlo code (SRIM2010) calculations. It has been found that the measured values of the mean projected range RP are good agreement with the SRIM calculated values; for the range straggling ΔRp, the difference between the experiment data and the calculated results is much higher than that of Rp.

Petrography of the impact breccias of the Enkingen (SUBO 18) drill core, southern Ries crater, Germany: New estimate of impact melt volume

A new drill core (SUBO 18) that intersects a continuous sequence of impact breccias has been obtained at the town of Enkingen at the southern edge of the Ries inner crater. Detailed petrographic analysis of this core provides important new information regarding the nature and origin of within-crater suevite, which is not only relevant for the understanding of the formation of the Ries impact structure but has strong implications for impact breccia deposition in general. In the Enkingen core, below 21 m of crater sediment, ∼90 m of impact breccia have been sampled. Most of this material is what in the past has been referred to as suevite—defined as groundmass of clastic material entraining cogenetic melt fragments and target rock clasts. Only the bottommost 10 m of core are melt-dominated impact breccia. Any relatively thick melt rock intersection along this core is revealed to be composed of individual centimeter- to decimeter-sized melt bodies best described as agglomerate due to its close resemblance to volcaniclastics of that type. Detailed macro-, meso-, and microscopic petrographic analysis has established that the SUBO 18 impact breccias cannot be divided into distinct units. The groundmass is extensively altered to phyllosilicate (smectite or chlorite) or carbonate minerals. Results of a detailed scanning electron microscopic investigation of the groundmasses of samples from all parts of this sequence emphatically support the traditional definition of suevite, irrespective of scale. Modal analysis at macroscopic to submicroscopic scales has shown that the overall, average melt content of Enkingen suevite is on the order of 48 vol%. This exceeds by far previous estimates and brings the Ries crater melt volume in line with values traditionally suggested from crater and melt volume scaling for similar-sized impact structures in crystalline and mixed targets.

Study of the lateral distribution of neodymium ions implanted in silicon

Due to the need to reduce electronic device sizes, it is very important to consider the depth and lateral distribution of ions implanted into a crystalline target. This paper reports that Nd ions with energies of 200 keV to 500 keV and dose of 5×1015 ions/cm2 are implanted into Si single crystals at room temperature under the angles of 0°, 30°, and 45°, respectively. The lateral spreads of 200keV–500keV Nd ions implanted in Si sample are measured by Rutherford backscattering technique. The results show that the measured values are in good agreement with those obtained from the prediction of SRIM2010 codes.

Problems of technological use of coherent Bremsstrahlung beams

To determine the possibility of technological use of coherent Bremsstrahlung beams the photonuclear transmutation doping of silicon by aluminum upon γ-quantum irradiation from the aligned single-crystal target was studied. An increase in aluminum concentration by approximately ten times was obtained upon γ-radiation of silicon from the crystalline target aligned by the crystallographic axis 〈111〉 along the direction of the electron beam with the energy of 1200 MeV. The orientation effect of an increase in the yield of γ-radiation from silicon and tungsten crystals in the range of energies of accelerated electrons of 300–1200 MeV was examined. This result is essential for the estimation of a possible minimum energy of electrons at which the use of the orientation effect is reasonable.

Effects of shock-induced incongruent melting within Earth’s crust: the case of biotite melting

Terra Nova, 23, 225–231, 2011 Biotite is an abundant hydrous silicate in the Earth’s crust and plays a critical role in the formation of felsic magmas via incongruent melting. Although biotite incongruent melting reactions have been described for various contact and regional metamorphic environments, the effects of impact-induced melting of biotite remain poorly understood. Our observations from the 40-km-wide Araguainha impact structure indicate that biotite can undergo incongruent melting during impact processes, producing aluminous melts that can accumulate as pockets or fracture networks in crystalline target rocks. We observed that as much as 9% of the crystalline target at Araguainha is a crystallization product after biotite breakdown. Given the relatively low shock pressures recorded in the Araguainha central uplift (20–25 GPa), our results imply that impacts in the size of Araguainha or larger are capable of generating substantial volumes of incongruent aluminous melts in crystalline crust underlying large (>40 km diameter) impact structures.

The Range Distribution of Er Ions Implanted in Silicon Crystal

Due to the need to reduce electronic device sizes, it is very important to consider the depth distribution of ions implanted into a crystalline target. The mean projected ranges and range straggling for energetic 150 – 500 keV Er ions implanted in single crystal silicon (c-Si) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The measured results are compared with other experimental data for amorphous Si (a-Si) and Monte Carlo code (SRIM2006) predictions. Our results show that, although the experimental values for range and range straggling exceed the SRIM calculations, they are nevertheless consistent with trends that have been previously observed for a-Si.

The Range Distribution of Nd Ions Implanted in Silicon Crystal

Due to the need to reduce electronic device sizes, it is very important to consider the depth distribution of ions implanted into a crystalline target. The mean projected ranges and range straggling for energetic 200 – 500 keV Nd ions implanted in single crystal silicon (c-Si) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The measured results are compared with Monte Carlo code (SRIM2006) predictions. Our results show that the measured values of the mean projected range are good agreement with the SRIM calculated values; for the range straggling , the difference between the experiment data and the calculated results is much higher than that of .

Multiproxy analysis of a new terrestrial and a marine Cretaceous–Paleogene (K–Pg) boundary site from New Zealand

An integrated study of palynology, Mössbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K–Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K–Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K–Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mössbauer spectroscopy shows an anomaly of Fe-containing particles in both K–Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic 187Os/ 188Os values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mössbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods.

CHARGE AND MASS CHANGING CROSS-SECTIONS OF 158A GeV Pb PROJECTILES ON Al, Cu, Bi, AND Pb TARGETS: FRAGMENTATION PROCESSES

We report here on total and partial charge changing cross-sections of 158A GeV lead projectiles on Al , Cu , Pb and Bi stationary targets using CR-39 detectors. Present results are compared with relevant published results. Deep discussion of nuclear fragmentation processes is provided. Stacks of CR-39 Track Detectors with above-mentioned targets were exposed to 158 A GeV 207 Pb projectiles at the CERN-SPS beam facility at normal incidence with a fluence of about 1500 ions/cm 2. Lengths of etched cones on one face of the CR-39 detectors before and after the target were measured for each stack. These measurements were used for determination of total and partial charge changing cross-sections of 158 A GeV Pb 82+ projectiles on these targets in the charge region 63 < Z < 82. The charge resolution (σZ) achieved in the present experiment is ~0.18e. Mass changing cross-sections are derived from the measured charge changing cross-sections using hyper-geometric relationship. A new method is proposed for separate measurements of electromagnetic and nuclear parts of fragmentation cross-sections using ion channeling and blocking conditions of projectiles in crystalline targets.

A predictive model for the electronic stopping force for molecular dynamic simulation (I)

We have examined a predictive model for the electronic stopping force ( dE/dx) e to be used in the classical molecular dynamic (MD) simulation. The essential term ( dE/dx) proton of ( dE/dx) e is based on the Lindhard–Winther theory, while the effective charge follows the Brandt–Kitagawa model. The ( dE/dx) proton term is expressed by the electron local density ρ( r) defined by the Muffin-tin model and the Hartree–Fock–Slater approximation. This model had been proposed to explain the impact-parameter dependence of ( dE/dx) e for channeling ions passing through a semiconductor. Here the energy dependence of the averaged 〈 dE/dx〉 e after thin-film transmission was examined, where the electron–phonon interaction can be ignored in the computation. The present work uses a nitrogen ( 14N) beam passing through a diamond with energies from 10 to 100 keV, which is fully included in the region. Because of the channeling components in the crystalline target, the calculated data 〈 dE/dx〉 e was 10% smaller than that of measured values in an amorphous target. The exponent of the energy dependence of 〈 dE/dx〉 e (∝ E 0.473) was a little gentler than that assumed in conventional models as ( dE/dx) e (∝ E 0.5). We have confirmed that this predictive model without a free parameter will be useful in a new system, even for a MD simulation that will take into account the electron–phonon interaction for a non-metallic target.

Fabrication of p‐Type Li‐Doped ZnO Films by RF Magnetron Sputtering

The p‐type Li‐doped ZnO films are successfully deposited on a glass substrate by RF magnetron sputtering at room temperature. The pure, crystalline sputtering target of LiXZn1−XO1−X/2 with X in the range of 0–0.003 is fabricated using the powder synthesized by the thermal decomposition of a metal–nitrate–tartrate gel complex at 400°–800°C. The complex is prepared by dissolving nitrates of zinc and lithium in an aqueous solution with nitric and tartaric acids. The resulting compacts, which can be densified at 1400°C, exhibit a decreasing trend of electrical resistivity with increasing Li content. For the composition with 0.2 mol% Li, the p‐type Li‐doped ZnO film has an electrical resistivity of 1.3 Ω·cm, Hall mobility of 0.77 cm2·(V·s)−1, carrier concentration of 6.67 × 1018 cm−3, and high optical transmittance in the visible region.