Metal Deposition Research Articles

Chemical reactions as a means of installing adlayers on electron transport layers

Adlayers are often placed at metal-on-organic interfaces as a common strategy to alleviate damage during metal deposition by thermal evaporation. Methods of chemically installing adlayers have been recently demonstrated on organic semiconductors that address these interfacial issues while providing many secondary benefits. Chemical installation has yet to be attempted at the cathode-electron transport layer (ETL) interface within organic light-emitting devices (OLEDs), offering a powerful option to optimize electron injection, improve surface wetting, and reduce metal penetration. Here, a reaction between TPBi (2,2′,2′’-(1,2,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) and propylene oxide results in a controllable 1–3 nm thick layer of propylene oxide as shown by high-resolution X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The reactive addition of the adlayer at temperatures below 40℃ does not affect the morphology of the thin film and reaches a high degree of coverage within 3 h. Integration of this layer into a phosphorescent OLED does not introduce any significant negative impact on device function. This result opens up the possibility of introducing further specific functionality into the adlayer to engineer OLED performance.

Trace metals in coastal marine sediments: Natural and anthropogenic sources, correlation matrices, and proxy potentials

Rapidly spreading industrialization since the 19th century has led to a drastic increase in trace metal deposition in coastal sediments. Provided that these trace metals have remained relatively immobile after deposition, their sedimentary enrichments can serve as records of local–regional pollution histories. Factors controlling this proxy potential include trace metal geochemistry (carrier-, and host phase affinity), and depositional environmental factors (redox variability, particulate shuttling, organic matter loading, bathymetry). Yet, the relative importance and interactions between these controls are still poorly understood, hampering the reliable use of trace metal-based environmental proxies. By summarizing nine site-specific correlation matrices of 16 metal (loid) s (Pb, Cd, Cu, Zn, Sb, Sn, Ni, As, Tl, V, Mo, U, Re, Fe, Mn, Al), total organic C, and S contents in short sediment cores into a single meta-matrix, we test a novel approach for quickly detecting common and contrasting trace metal enrichment patterns across different study locations. Our meta-matrix shows two trace metal groups, within which positive correlations of e.g., Pb, Cd, Zn, Cu, Sb suggest a primary “anthropogenically sourced” (group I) control, whereas known “redox-sensitive” (group II) trace metals (Mo, U, Re) are characterized by fewer positive correlations. However, some group I metals (Cd, Zn, Cu, Sb) also covary with group II metals, inferring that redox variability may obscure primary anthropogenic signals; Sb even shows advantages over Mo and U under oxic conditions. As a more robust pollution indicator we identified Pb; yet for reconstructing historical Pb atmospheric pollution signals (1970s Pb peak), it is crucial to consider the distance from shore. In near-shore environments, local (fluvial) pollution signals may overprint large-scale (atmospheric) signals. Our findings demonstrate that combining site-specific sedimentary correlation and distribution patterns with a meta-matrix considerably aids the understanding of trace metal sequestration in different coastal sedimentary environments, which thereby improves trace metal proxy reliability.

Contact Resistance Engineering in WS2-Based FET with MoS2 Under-Contact Interlayer: A Statistical Approach.

One of the primary factors hindering the development of 2D material-based devices is the difficulty of overcoming fabrication processes, which pose a challenge in achieving low-resistance contacts. Widely used metal deposition methods lead to unfavorable Fermi level pinning effect (FLP), which prevents control over the Schottky barrier height at the metal/2D material junction. We propose to harness the FLP effect to lower contact resistance in field-effect transistors (FETs) by using an additional 2D interlayer at the conducting channel and metallic contact interface (under-contact interlayer). To do so, we developed a new approach using the gold-assisted transfer method, which enables the fabrication of heterostructures consisting of TMDs monolayers with complex shapes, prepatterned using e-beam lithography, with lateral dimensions even down to 100 nm. We designed and demonstrated tungsten disulfide (WS2) monolayer-based devices in which the molybdenum disulfide (MoS2) monolayer is placed only in the contact area of the FET, creating an Au/MoS2/WS2 junction, which effectively reduces contact resistance by over 60% and improves the Ion/Ioff ratio 10 times in comparison to WS2-based devices without MoS2 under-contact interlayer. The enhancement in the device operation arises from the FLP effect occurring only at the interface between the metal and the first layer of the MoS2/WS2 heterostructure. This results in favorable band alignment, which enhances the current flow through the junction. To ensure the reproducibility of our devices, we systematically analyzed 160 FET devices fabricated with under-contact interlayer and without it. Statistical analysis shows a consistent improvement in the operation of the device and reveals the impact of contact resistance on key FET performance indicators.

Fate of heavy metals in ecosystems of dam reservoirs: Transport, distribution and significance of the origin of organic matter

In this article, a multivariate analysis of the parameters determining the transport and fate of selected heavy metals in the water - bottom sediment interface was carried out. The studies were carried out in the summer season of 2019 at Nielisz Reservoir (southeastern Poland, Lublin Voivodeship).Finally, a previously unknown factor related to the quality of organic matter was identified. Autochthonous organic matter was shown to promote the accumulation of the studied heavy metals. To date, the significance of the origin of organic matter in the context of the transport and fate of heavy metals in retention reservoirs has rarely been reported in the scientific literature. More than that, this factor was not considered an important component in the process of heavy metal deposition in bottom sediments. However, it turns out that not only the quantity of organic matter, but also its quality plays an important role in the circulation of heavy metals in retention reservoir ecosystems. It was found that autochthonous organic matter promotes the accumulation of the studied heavy metals. It can be assumed that, in a sense, it plays the role of a catenary ("hub") controlling the fate of heavy metals in the water-sediment system. It has also been conjectured that, in a sense, OMS may reflect the potential for heavy metal assimilation by aquatic vascular plants (mainly of the C3 group). Plants with a photosynthetic pathway similar to the C3 group generally have a much lower enrichment in the 13C isotope (δ13C from −38‰ to −22‰). In our case, the lowest δ13C-TOCS value was −24.05‰, and the average for the whole reservoir was −21.53‰. In addition, it was observed that quantitative changes in the isotopic composition of total organic carbon δ13C-TOCS, corresponded with changes in the content of the heavy metals studied in entrapped sediments.

Laser metal deposition of Al 7075: Effects of TiC nanoparticles

High-density defects in additively manufactured components cause poor mechanical properties and premature failure. The present paper aims in minimizing defects in laser metal deposition (LMD) of high-strength aluminium alloy 7075. The effects of different TiC nanoparticle contents on the defects (crack and porosity), microstructural (grain size and morphology) and mechanical (tensile strength and hardness) properties were investigated systematically. The sizes and densities of cracks and surface porosities were reduced by increasing TiC nanoparticle content. The grain areas were reduced and ultimate tensile strength increased by increasing the TiC nanoparticle content. The present results clearly prove that the TiC content plays a substantial role in tailoring microstructure and improving the reliability and mechanical properties of LMD Al alloy 7075.

Printable, stretchable metal-vapor-desorption layers for high-fidelity patterning in soft, freeform electronics

High-fidelity patterning of thin metal films on arbitrary soft substrates promises integrated circuits and devices that can significantly augment the morphological functionalities of freeform electronics. However, existing patterning methods that decisively rely on prefabricated rigid masks are severely incompatible with myriad surfaces. Here, we report printable, stretchable metal-vapor-desorption layers (s-MVDLs) that can enable high-fidelity patterning of thin metal films on freeform polymeric surfaces. The printed rubbery matrix with highly mobile chains effectively repels various metal vapors from the surface and inhibits their condensation, thereby allowing selective metal deposition. The s-MVDLs are printed by direct ink writing techniques, enabling customizable and scalable thin metal patterns ranging from the micrometer to millimeter scale with high fidelity. Furthermore, the superior stretchability and mechanical robustness of the s-MVDLs allow highly compliant deformation along the substrates, enabling the construction of unconventional circuits and devices on multi-curvature, non-developable, and stretchable surfaces.

Cu–Polymetallic Deposit Exploration under Thick Cover in Gucheng–Yaxi Area Using Audio-Magnetotelluric and Spread-Spectrum-Induced Polarization

Successful geophysical exploration projects in the Gucheng–Yaxi area located in Gaochun District, Jiangsu Province, China, have been limited partly due to the complex geological conditions of the area and high artificial noise in data acquired using electrical and electromagnetic methods. In this study, we deployed the new anti-interference spread-spectrum-induced polarization method (SSIP) and the audio-magnetotelluric (AMT) method to detect a copper–polymetallic deposit in the area. Two-dimensional inversion results in the Gucheng–Yaxi area revealed a high chargeability anomalous zone on the SSIP profile that coincided with a zone of moderate resistivity located between two resistor bodies on the AMT profile. A follow-up 1200 m drill hole was established at this high-chargeability, moderate-resistivity zone which encountered polymetallic (copper, lead, zinc, gold, and silver) mineralization at a depth of ≥400 m. Drill hole data analysis showed that mineralization occurred interspaced in the marble rock mass at varying depths. Furthermore, several low-resistivity, weak-chargeability sections were revealed and attributed to Cretaceous sediments and faults. These faults are thought to have played a critical role in the polymetallic mineralization genesis. In summary, this study demonstrated the successful of application of SSIP and AMT in detecting a metallic deposit in an area with high artificial noise. Hence, the geophysical prospection potential of the Gucheng–Yaxi area is great.

Development of Modified TiO2 for Photocatalytic Hydrogen Production

AbstractTiO2 has advantages such as excellent photocatalytic performance, high chemical stability, low price, and not easy to produce secondary pollution. Therefore, the photocatalytic hydrogen production over TiO2 catalyst was an effective way to achieve hydrogen production from solar energy with low energy consumption and low cost. However, the TiO2 catalyst responds only to UV light due to its wide forbidden band, and the electrons and holes were prone to recombination, resulting in the decrease in photocatalytic activity and quantum efficiency. In recent years, researchers have conducted a series of modifications on TiO2 to improve its visible light response, reduce the rate of carrier recombination, and thereby enhance the efficiency of photocatalytic hydrogen production. This paper reviews several main modification methods of TiO2 including morphology regulation, ion doping, semiconductor recombination, noble metal deposition, dye sensitization and their research progress in the field of photocatalytic hydrogen production. Finally, the modification of TiO2 photocatalyst in the future was predicted.

In-situ X-ray imaging of the breakup dynamics of current-carrying molten metal jets during arc discharge

The flow dynamics of current-carrying molten metal jet breakup during arc discharge serves as mass and heat sources in wire-arc-based metal deposition processes, thereby optimizing the resultant product quality. However, the spatiotemporal flow interaction between the molten metal jet and the surrounding arc plasma remains unclear. Here, using in-situ synchrotron X-ray imaging, we simultaneously track surface deformation and internal flow in molten aluminum jets during argon arc discharge. We reveal that modulating the magnitude and path of the arc discharge current can accelerate the jet velocity by 200–300% beyond its initial injection speed, thereby facilitating significant jet elongation. Our results provide consistent evidence that the jet flow dynamics are predominantly governed by the interaction between the arc discharge current and its coaxial self-induced magnetic field. This study establishes a framework at the intersection of fluid dynamics and electromagnetism, contributing to optimized control and precision in wire-arc-based applications.

High-temperature planar asymmetric ceramic membranes: Effect of the Pt amount and dispersion on the H2 separation performance

This work investigates for the first time the effect of Pt catalyst amount and dispersion on hydrogen permeation performances of BaCe0.65Zr0.20Y0.15O3−δ–Gd0.2Ce0.8O2−δ (BCZY–GDC) composite planar Cer-Cer membranes with asymmetrical architecture, aiming to maximize the ratio between the permeated hydrogen and the metal content. To boost the hydrogen separation reactions, Pt must be deposited on both the dense and porous sides of the membrane. Moreover, the complex architecture of the porous layer can be used to disperse Pt particles providing a good interaction with the membrane. To fulfil this aim BCZY-GDC membranes composed of a 20 μm thick active dense layer and a 600 μm thick, porous support were produced by tape casting and impregnated with different amounts of platinum. Hydrogen permeation properties were thoroughly investigated examining the composition of the feed and the sweep gasses, temperature, stream humidification, catalyst amount and nature of the dispersion media. The effect of Pt-catalysed hydrogen permeation and water splitting reaction at the permeate side was investigated and discussed. It was found that using an optimal amount of Pt solution to activate the porous side of the membranes is paramount to increase hydrogen permeation in the whole operating temperature range while keeping low the amount of noble metal catalyst. Moreover, the selection of a proper solvent with good interaction with the membrane allows the obtainment of smaller Pt nanoparticles resulting in higher permeation. The best performances in terms of hydrogen permeation (0.74 and 1.29 mL min−1 cm−2 at 750 °C using a feed stream with respectively 50 % and 80 % of H2 in He) were obtained using an acetone-based solution for depositing 1.5 mg cm−2 of Pt at the porous side. This work suggests that the metal deposition plays a non-trivial role in the hydrogen separation process and should be fully evaluated to increase the final performance while cutting down the cost of the Pt catalyst and therefore, of the final device.

Surface dependence of electronic growth of Cu(111) on MoS2

Scanning tunneling microscopy shows that copper deposited at room temperature onto a freshly exfoliated MoS2 surface forms Cu(111) clusters with periodic preferred heights of 5, 8, and 11 atomic layers. These height intervals correlate with Fermi nesting regions along the necks of the bulk Cu Fermi surface, indicating a connection between physical and electronic structures. Density functional theory calculations of freestanding Cu(111) films support this as well, predicting a lower density of states at the Fermi level for these preferred heights. This is consistent with other noble metals deposited on MoS2 that exhibit electronic growth, in which the metal films self-assemble as nanostructures minimizing quantum electronic energies. Here, we have discovered that it is critical for the metal deposition to begin on a clean MoS2 surface. If copper is deposited onto an already Cu coated surface, even if the original film displays electronic growth, the resulting Cu film lacks quantization. Instead, the preferred heights of the Cu clusters simply increase linearly with the amount of Cu deposited upon the surface. We believe this is due to different bonding conditions during the initial stages of growth. Newly deposited copper would bond strongly to the already present copper clusters, rather than the weak bonding, which exists to the van der Waals terminated surface of MoS2. The stronger bonding with previously deposited clusters hinders additional Cu atoms from reaching their lowest quantum energy state. The interface characteristics of the van der Waals surface enable surface engineering of self-assembled structures to achieve different applications.

Laser metal deposition of thin-walled parts of Al0.8CrFe2Ni2 high-entropy alloy: Process window, microstructure, wear resistance and mechanical anisotropy

In this paper, an exponential regression model is employed to analyze the sensitivity of the geometrical characteristics of single track, building efficiency and powder efficiency to the process parameters for the Al0.8CrFe2Ni2 high entropy alloy (HEA) fabricated by laser metal deposition (LMD). Based on the exponential regression model and sensitivity analysis, an effective process window is obtained to deposit a multilayer thin-walled structure. The Al0.8CrFe2Ni2 HEA consists of the (Fe, Cr, Ni)-rich faced centered cubic (FCC) phase and (Al, Ni)-rich B2 phase. An anisotropic mechanical property along the building direction and scanning direction is discovered due to the different strengthening mechanisms and fracture modes. Dislocation strengthening dominates in the building direction, while the high yield strength in the scanning direction is the result of dislocation, grain boundaries and precipitation strengthening. Compared to 400 °C, the Al0.8CrFe2Ni2 HEA has a lower wear rate at 25 °C owing to the self-lubricating protection provided by the completed oxide glaze layer. The findings provide guidelines for improving the anisotropic mechanical properties of thin-walled parts of LMD-deposited HEAs.

Surface Functionalization of 3D-Printed Scaffolds with Seed-Assisted Hydrothermally Grown ZnO Nanoarrays for Bone Tissue Engineering.

Bioactive metal-based nanostructures, particularly zinc oxide (ZnO), are promising materials for bone tissue engineering. However, integrating them into 3D-printed polymers using traditional blending methods reduces the cell performance. Alternative surface deposition techniques often require extreme conditions that are unsuitable for polymers. To address these issues, we propose a metal-assisted hydrothermal synthesis method to modify 3D printed polycaprolactone (PCL) scaffolds with ZnO nanoparticles (NPs), facilitating the growth of ZnO nanoarrays (NAs) at a low-temperature (55 °C). Physicochemical characterizations revealed that the ZnO NPs form both physical and chemical bonds with the PCL surface; chemical bonding occurs between the carboxylate groups of PCL and Zn(OH)2 during seed deposition and hydrothermal synthesis. The ZnO NPs and NAs grown for a longer time (18 h) on the surface of PCL scaffolds exhibit significant proliferation and early differentiation of osteoblast-like cells. The proposed method is suitable for the surface modification of thermally degradable polymers, opening up new possibilities for the deposition of diverse metals.

Trends in mercury, lead and cadmium concentrations in 27 European streams and rivers: 2000–2020

Temporal trends for concentrations of mercury (Hg), lead (Pb) and cadmium (Cd) were evaluated from year 2000–2020 in 20 (Hg), 23 (Pb) and 11 (Cd) watercourses in remote forest catchments in Europe. Decreasing trends were observed in 15% (Hg), 39% (Pb) and 45% (Cd) of the watercourses during the period of evaluation. Decreasing trends were mainly observed between 2000 and 2005 for Hg and between 2000 and 2015 for Pb and Cd. For the last five years of the studied time period (2015–2020), more watercourses showed significant increasing, rather than decreasing Hg, Pb and Cd trends. This was interpreted as a legacy effect of metals still retained in catchment soils. The overall negative trends during the earlier part of the study period were likely driven by declining deposition of metals over Europe, especially for Pb and Cd. Other changes related to metal transport and chemistry may have contributed to the observed trends as well, including recovery from acidification and the ongoing browning of surface waters at northern latitudes. Here we found that organic carbon could explain the seasonal variation in Hg and Pb, but was not related the interannual trends. This study highlights the need for long-term monitoring and robust statistical methods that can detect multidirectional, long-term change in water chemistry.

Design and destructive testing of high-value hook fabricated by laser metal deposition

Laser metal deposition (LMD) provides an emerging opportunity for the economic fabrication of high-value components at low production volume. Despite the technical and commercial opportunities associated with LMD, there exist potential failure-modes that differ from those typical of traditional manufacture; concurrently, LMD is typically applied to high-value components associated with a high consequence of failure. This report contributes to the emerging literature on LMD component design and failure analysis by documenting the design and destructive testing of a high-value tensile loaded hook component, including numerical structural simulation, manufacture characterisation, microstructural analysis and instrumented destructive testing. This systematic design contributes to the understanding of LMD design for structural integrity and supports the application of LMD as a robust commercial additive technology.

Comprehensive study of microstructural evolution and strengthening mechanism of high-performance pure copper prepared by blue laser metal deposition (B-LMD)

The high absorption of the copper to the blue laser provides an alternative method to circumvent the laser reflection of laser metal deposition (LMD) of pure copper. In this work, blue laser metal deposition (B-LMD) was used to prepare pure copper parts. The B-LMD pure copper tracks fabricated using the optimum processing parameter have well bonding with the substrate, consisting of fine equiaxed grains with an average size of 2.8 μm, and exhibit the highest microhardness of 133.21 HV0.2. The pure copper deposit fabricated by the optimum processing parameter exhibited the highest relative density (97.9 % ± 0.2 %) and microhardness (103.05 ± 4.37 HV0.2). Additionally, the microstructure of the B-LMD pure copper deposit is showing a bimodal grain structure with columnar grains at the melt pool boundary and fine equiaxed grains at the center. The B-LMD pure copper deposit exhibits excellent mechanical properties, with an ultimate tensile strength of 244 ± 9 MPa, yield strength of 158 ± 6 MPa, and a fracture elongation of 14.7 ± 0.8 %. The superior mechanical properties are primarily attributed to grain refinement strengthening and dislocation strengthening. The high performance of B-LMD pure copper demonstrate the potential of the blue laser as an effective alternative energy source for fabricating high-performance pure copper components.

The time evolution of electrical and thermodynamic characteristics of surface dielectric barrier discharge caused by dielectric degradation

Abstract The degradation of the dielectric layer is a common issue in dielectric barrier discharge (DBD). The performance of DBD devices may suffer from instability due to potential corrosion of the dielectric layer caused by discharge, which could even result in structural failure. To gain a comprehensive understanding of the degradation of DBD devices during discharge, the evolution of the performance of DBD devices with various dielectric materials over time is studied. Periodic patterns are found to form on the dielectric surface along the edge of the high-voltage electrode. The electrical data, emission spectra, and surface morphologies of DBD devices with three different dielectric materials, namely ceramics, glass, and PCB, are obtained during an eight-hour discharge. The electrical and thermodynamic characteristics of DBD devices with the three dielectric materials are found to initially decrease by about 20~40%. Subsequently, they remain stable in devices with ceramics and PCB dielectric layers but increase in devices with glass dielectric layers until the end. Surface morphologies reveal that periodic patterns consisting of metal accumulations, etching pits, and metal depositions form on the surfaces of ceramics, glass, and PCBs, respectively. Some organic compounds vaporize from the surface of PCBs. The deposition, etching, and vaporization could be reasons for changes in the electrical and thermodynamic characteristics. It shows that degradation occurs not only in organic dielectrics like polymers but also in inorganic dielectrics such as ceramics and glass. To enhance stability and prevent potential failures and overestimations, electrical and optical measurements could be utilized as diagnostic methods in applications involving DBD devices.


Antimicrobial activity of the LTA zeolite modified by zinc species

Metal species supported on zeolites have proven efficient synergistic mechanisms against microorganisms, reducing the overall toxicity. Likewise, the deposition of metals by ultrasound is a method that has drawn attention due to its efficiency, low cost, and environmental friendliness. Hence, the antimicrobial properties of Zinc (Zn) species supported on LTA zeolite (NaA) via a sono-assisted method were explored in this study. Zeolite A modified with Zn species by ion exchange or sono-assisted precipitation of active Zn species (Zn(OH)2, ZnO, and ZnO2) was evaluated in a screening experiment by agar diffusion and micro broth assays. Finding that at a concentration of 30 mg/mL, drying the ZnO2@NaA material activated a mechanism that inhibited the growth of E. faecalis by 100 % while eliminating the drying step, an inverse effect was produced, now inhibiting the growth of E. coli. This sample also presented promising properties as an antimycotic agent inhibiting the growth of C. albicans by 90 % at a concentration of 1 mg/mL. In addition, a viability analysis was performed on fibroblasts, demonstrating a potential toxicity reduction.This ZnO2@NaA material holds promise as an antibacterial and antifungal agent. Presenting a novel sono-assisted methodology for tuning the selectivity of inhibition mechanisms for peroxide-containing species in zeolites. This selected zinc-containing zeolitic material (ZnO2@NaA) was then characterized by UV–Vis, FTIR, Raman spectroscopy SEM, XRD, and ζ-potential, evidencing the presence of ZnO2 nanoparticles. This study opens perspectives for developing new antimicrobial Zn-containing zeolitic materials through a sono-assisted methodology for increasing selectivity in the inhibition mechanisms.

Phytotoxic responses of acrocarpous moss Campylopus schmidii as bioindicators in copper and cadmium contaminated environments: A comprehensive assessment

Mosses play a vital role in environmental research as reliable biomonitoring tools. This study aims to understand the accumulation and distribution patterns of Cu and Cd in the acrocarpous moss [Campylopus schmidii (Müll. Hal.) A. Jaeger] (C.schmidii). In controlled in vitro experiments, C.schmidii cultures were exposed to varying concentrations of copper (Cu) and cadmium (Cd) stress (0, 10, 25, 50 μmol/L) in aquatic media. The study systematically evaluated the moss's response, including observing appearance features, oxidative traits, and accumulation characteristics. Scanning electron microscopy with energy-dispersive X-ray spectroscopy analyses were employed. They aimed to characterize and determine the distribution of metal particles in different parts of the mosses under high concentration treatments (50 μmol/L Cd, 50 μmol/L Cu, 50 μmol/L Cu and Cd). Results indicated that C.schmidii exhibited greater tolerance to Cu compared to Cd, as evidenced by significantly higher soluble protein content and lipid peroxidation with increasing concentrations. However, Cd stress induced severe damage, including widespread chlorosis, reduced chlorophyll content, and surface fragmentation. Both Cu and Cd were found to stimulate antioxidant levels by increasing the activity of hydrogen peroxide and peroxidase, thus reducing the accumulation of free radicals in C.schmidii. Additionally, the results revealed differential metal distribution. Higher Cu (2.23%) and lower Cd (0.54%) accumulation were observed at the bottom of gametophores, with Cd content 180.46% higher than Cu at the top. This study provides valuable insights into the potential application of acrocarpous mosses for biomonitoring and phytoremediation. It suggests specific strategies for metal deposition and absorption, such as utilizing upper, younger parts for Cd absorption and lower parts for Cu remediation in soil.

High Temperature and FORC Investigations of Semiconducting/Ferromagnetic Nanocomposites

In the frame of this work the temperature-dependency of the magnetization of various composite systems consisting of porous silicon (PSi) and silicon nanotubes (SiNTs) with embedded Ni, Co, NiCo, FePt, and Fe3O4 structures is discussed. The temperature is varied between 80 and 1273 K which allows to determine the Curie Temperature of the composites which is higher than for the corresponding bulk materials. High temperatures result in an alteration of the chemical sample-composition. Depending on the temperature specific metal-silicide formation occurs usually beginning around 600 K. This leads to modified magnetic behavior of the composites which can be observed by repeated measurements. Magnetic cross-talk between metal deposits can be controlled by the morphology of the porous silicon (distance between the pores) or silicon nanotubes (wall thickness) and also by the distribution and size of the deposits within the pores. To get a clear knowledge about the magnetic interactions single hysteresis curves are not sufficient and thus first order reversal curves (FORC) are performed.The employed PSi is produced by anodization of a highly n-doped silicon wafer. The structures offer an average pore-diameter of 50 nm and a mean distance between the pores of 50 nm which ensures a clear separation of the pores, a crucial point to achieve the appropriate magnetic properties. The SiNTs are produced by ZnO seed deposition on a silicon wafer, growing of the ZnO nanowire arrays (NWA), followed by Si deposition and finally etching off the ZnO. Ni and Co are deposited electrochemically in using for Ni formation a Watts electrolyte, consisting of NiCl2, NiSO4 and H3BO3 and for Co deposition a CoSO4 solution is utilized. A further approach is to grow Co particles inside the pores/tubes in using a CoCl2 6H2O and NaBH4 solution. Fe3O4 are synthesized by high temperature decomposition in the presence of an organic precursor (1). The synthesized particles are infiltrated into the pores/tubes with the help of a magnet beneath the samples. FePt nanocrystals are formed within the SiNTs and PSi by a multistep process, using a solution containing Citric acid, H2PtCl6 6H2O, and Fe(NO3)3 9H2O.Considering Ni loaded porous silicon samples, the magnetic response is recorded in dependence on the temperature to figure out the Curie temperature (TC) of the composite system which is determined from hysteresis curves measured at various temperatures between 80 and 950 K in field steps of 50 K. TC is determined at 700 K, which is about 70 K higher than for bulk Ni. Co loaded porous silicon has been measured up to 1200 K which was still too low to determine TC. TC of bulk magnetite is at 858 K. The investigated porous silicon sample with 8 nm Fe3O4 NPs infiltrated into the pores shows TC around 900 K, 42 K higher than for the bulk material. In the case of FePt loading, the system with PSi as template shows a lower TC compared to SiNTs. The investigations show that the TC of the investigated nanostructured composite systems is always higher than for the according bulk materials. FORC diagrams are used to detremine magnetostatic interactions between the metal deposits. Magnetic coupling is present for Ni, Co and NiCo deposits, wheras in the case of FePt NP loading no magnetic cross-talk between the particles is observed.(1) L. Gutierrez, R. Costo, C. Grüttner, F. Westphal, N. Gehrke, D. Heinke, A. Fornata, Q.A. Pankhurst, C, Johansson, S. Veintemillas-Verdaguer, M.P. Morales,Dalton Transactions, 44, 2943, (2015).