Nanomagnetism and spintronics : fabrication, materials, characterization and applications
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Resume : The development of novel approaches for the creation of nanoobject arrays with precise positional control on large areas at low cost is crucial for e. In this contribution, we present a bottom-up approach for the positioning of quantum dots QDs in nanohole arrays using DNA origami as transport vehicle. The use of self-assembly techniques for nanohole array creation, DNA origami formation and their directed ordering on the surface makes this approach straight-forward for wafer-scale surface patterning with nanoscale resolution.
We investigate the adsorption of these DNA origamis on surfaces prepatterned by nanosphere lithography. Nanohole arrays, i. The material system presented here can be understood as a model. Our approach is promising for many applications as it is flexible in choice of QD material, the number of QDs per origami and per nanohole, nanohole periodicity and diameter and thin film and substrate material. Resume : Colloidal quantum dots CQDs have recently emerged as favorable light-emitting materials, which also show great potential as optical gain media due to their remarkable optical properties.
Optical gain, as expressed through amplified spontaneous emission ASE has been reported from close-packed, solid-state films of CdSe nanocrystal QDs by optical pumping, followed by a number of reports that have focused on the details of the role of different multi-exciton states to optical gain. Howerver, achieving practical QD lasing at room temperature under continuous optically pumped is still a challenge due to non-radiation Auger processes.
Resume : Natural and man-made information processing systems differ greatly. Evolution has resulted in living systems that utilize whatever physical properties are exploitable to enhance the fitness for survival. Nature thereby exploits the emergent properties and massive parallelism of highly interconnected networks of locally active components. Man-made computers, however, are based on circuits of functional units, following rigid design rules.
Hence, in conventional computational paradigms, potentially exploitable physical processes to solve a problem, are left out. Here, we use evolution-in-materio, which mimics Darwinian evolution by manipulating physical systems using computer-controlled evolution, to take full advantage of the computational power of nanomaterials. We have experimentally demonstrated that a designless network of gold nanoparticles — acting as single-electron transistors at low temperature — exhibits strongly non-linear behavior, which can be evolved into computational functionality.
We have realized two-input-one-output Boolean logic gates and a half-bit adder in this system . The viability of our approach is underlined by simulations based on both physical  and neural-network models . Recent experimental results show that the above principle is generic, and can be demonstrated in other material systems as well, also at much higher temperatures. The present challenge is to realize more advanced functionality, preferably at higher temperature. We propose reservoir computing as a suitable framework, where not only nonlinearity but also fading memory is a crucial ingredient.
References:  S. Bose, C. Lawrence, Z. Liu, K. Makarenko, R. Broersma and W. Broersma, J. Mikhal, C. Lawrence and W. Greff, R. Lawrence, W. Resume : In this work, the interfacial self-assembly of several energetic nanocrystals were selected to study the interfacial self-assembly, including the reaction kinetics and mechanism.
By induction of solvent and thermal treatment, large energetic crystals with regular morphology, uniform size, smooth surface and few defects can be obtained via thermal-metastable self-assembly in a particle level. Effects of different experimental parameters, including reaction temperature, grain size of nanocrystals, solvent system and additional surfactant adopted were investigated for the self-assembly process.
The detailed investigation of the appearance and crystal structure of the assembled products were conducted by scanning electron microscopy, optical polarized microscopy, atomic force microscopy, particle size distribution and coherence strength analyses. X-ray diffraction combined with Fourier-transform infrared and Raman spectra were used to determine the polymorphic transition behaviors.
Besides, the impact sensitivity and thermal properties of as-prepared crystals were also studied to evaluate their performances compared with the high-quality crystals after careful recrystallization. Characterization results indicate that energetic crystals after such thermal-metastable assembly exhibit well-defined morphology, narrow size distribution, integrated crystal structure and high compactness, with apparent improvement in impact safety.
The assembly kinetic was presented as followed the Avrami equation. The possible mechanism was proposed based on the observation of the intermediate state crystals, which is a typical three-step process including surface solvent induction originated from surface solvation or slight dissolution, particle agglomeration and interfacial crystal growth.
Resume : Transparent conducting electrodes have attracted substantial attentions as an essential component of various optoelectronic devices. Recently, the grid-structured metal mesh electrodes are considered as highly efficient transparent electrodes that possess high optical transmittance while maintaining sufficient electrical conductivity and are suitable for flexible conductors with isotropic electrical conductivity. Here, we report a simple and effective approach for the fabrication of highly transparent Ag nano-mesh prepared by all water-based solution process.
The Ag mesh electrodes were formed by combination of colloidal gold nanoparticles deposition and silver enhancement. The optical and electrical properties of the Ag mesh can be finely tuned by varying condition of gold nanoparticle deposition and silver enhancement. The smallest feature size of the obtained metal mesh patterns is about nm with a thickness of nm. Through this study, not only fabrication of high performance metal mesh but also low cost fabrication without any hazardous wastes is succeeded.
Resume : We examine strategies for directing self-assembly in nanostructured soft materials to create single crystals and bespoke textures. Our work elucidates physical processes that are relevant for such directed self-assembly, in part by leveraging in situ scattering tools, with an overall goal of exploiting fundamental understanding to create useful materials or devices. In particular, we consider the use of magnetic fields and confinement effects for directed self-assembly of soft mesophases of block copolymers and discotic liquid crystals.
The ability to produce highly ordered functional materials over macroscopic length scales is demonstrated. We explore the role of alignment and connectivity in creating materials with highly anisotropic ion transport, and in creating highly selective nanofiltration membranes with uniformly aligned nanopores produced by molecular self-assembly. Application of orthogonal fields, and field processing across sequential phase transitions enables a novel realization of macroscopic single crystals of self-assembled mesophases with precisely specified texture.
Recent progress on low field sub-1 T alignment and the associated potential to develop bespoke textures in block copolymers using local field screening are presented. Resume : Block Copolymers BCPs are attracting wide interest for advanced lithographic applications due to their ability to self-assemble into well-ordered nanometric size structures. One of the key points useful for the practical implementation BCP in nanolithography is the increase of the lateral ordering of the nano-domains.
To this goal, several methods have been proposed so far, involving the use of chemically patterned substrates, soft and hard graphoepitaxy. After the thermal annealing performed in a rapid thermal processing RTP machine at high temperature Ta between oC we obtained a sensible increase of the lateral ordering? Furthermore, under particular annealing conditions, the formation of dewetted features composed by parallel lamellae propagating for several micrometers was obtained.
Doerk, Kevin G. Rapid Ordering in? Wet Brush? ACS Nano , 11, ? Resume : Block copolymer BCP thin films have been widely studied thru the last few decades. This interest is connected with pursuance of microphase separation that enables BCPs to create various periodic nanostructures. However, without additional effort, spontaneously-formed morphologies are ordered only on the short length-scales and display no long-range order critical in many practical applications. It is a complex combinatorial process, where sweeping laser line induces thermal gradients in the substrate, which combined with simultaneous soft shearing above, yields well-ordered BCP morphologies.
In its first implementations, the utility of the SS-LZA method for macroscopic alignment has been limited thin layers of thermal conductors deposited on substrates with poor heat dissipation properties such as glass or quartz . Here, we present a new approach, which allows us to align BCP thin films on conventional substrates, such as regular silicon wafers broadly used by researchers and industry. We believe that overcoming that technical difficulty could contribute to the broader use of the method.
Resume : Bottom-up self-assembly fabrication processes allow for the fabrication of various functional nanostructures, e. These plasmonic materials, manufactured using gyroid terpolymer films as templates, are engineered to exhibit interesting optical properties including a depressed plasma frequency and linear dichroism. However, these optical properties can only be observed in nanostructured samples with long-range order.
A convenient way to generate long-range order in block copolymer templates is to direct the polymer self-assembly in films by using lithographically patterned substrates. However, directed self-assembly DSA has been mostly shown for simple morphologies like spheres, cylinder or lamellae, whereas there are only very few examples of DSA of three-dimensional network structures like the gyroid.
In this work, we are exploring the DSA of gyroid terpolymer films on patterned substrates in combination with well-controlled solvent vapor annealing experiments. The effects of the polymer film thickness, trench dimensions and annealing conditions on the alignment and degree of order of the gyroid structures are analyzed based on an atomic force microscopy characterization of the polymer films on various substrate patterns.
Resume : Sequential infiltration synthesis SIS provides a successful route to grow inorganic materials into polymeric films through the penetration of of gaseous precursors into the polymer, both in order to enhance the functional properties of the polymer creating an organic-inorganic hybrid material, and to fabricate inorganic nanostructures when infiltrating in patterned polymer films or in self-assembled block copolymers BCP.
In particular we investigate in detail the effects of the guiding structure that drives the block copolymer self-assembly process on the final morphology of the Al2O3 nanostructures. Finally Al2O3 pillars are used as hard mask to perform a pattern transfer into the underlying substrate and form high aspect ratio Si structures.
Resume : The field of process nano- engineering increasingly embraces new emerging fabrication methods. Besides relying on established techniques using charged particle lithography electrons and ions and thin film processing, we constantly explore new methods that are not harmful to sensitive functional material required for nanosystems, such as 2D systems or organic molecules. Three of such enabling methods are nanostenciling , thermal scanning probe lithography t-SPL and nanoparticle capillary assembly .
Here, I will focus mainly on t-SPL. Our current research in this field focuses on improved 3D capabilities  using the t-SPL. Further, we explore the extremely reduced spatio-temporal control nm-microsecond of heat generation to induce phase changes in functional material systems. A second material we are exploring is silk, which is biocompatible and can switch water-solubility when exposed to heat .
These emerging methods do not use radiation, plasma and harsh etch chemistry, and thus can be applied to sensitive materials. In future, we may combine them into a comprehensive nano-toolbox allowing for hybrid mix-and-match fabrication also combined with conventional lithography. Vazquez-Mena et al. Microelectronic Engineering  V. Flauraud et al. Nature Nanotechnology  Y. Lisunova et al. Microelectronic Engineering  S. Zimmermann et al. ACS Appl. Interfaces  S. MNE , Braga, Portugal.
Namely, has been used to monitor in real-time the formation of self-assembled monolayers highly organized in which the molecules arrange themselves into packed 2D crystals and fully covering the surface[1,2]. Several high resolution STM images about self-assembly molecular systems formation have been reported revealing the parameters which are involved in the monolayers formation whether they are physical parameters e. Recently, the STM has been used to build molecular systems with multicomponents, e. This work reviews the methodology which is involved in the development of these systems revealing details on how to use the STM to monitor their fabrication.
References:  Q. Ferreira, A. Moura, M. Faustino, L. Oliveira, A. Figueiredo, J. Bioucas, Q. Ferreira, L. Delfino, Q. Ferreira, Recent Advances in bottom-up self-assembled supramolecular structures builded by STM, Materials, , accepted. Resume : Nanoparticles have a wide range of potential applications in catalysis, sensorics or electrochemistry . For these applications it is often necessary to immobilize the particles and the assembly of nanoparticles into porous networks, called gels, is a promising approach to fulfill this need.
The interesting properties of nanoparticles such as high surface to volume ratio as well as the unique nanoscopic optical properties can be retained throughout the gelation process. Additionally the gelation can even introduce new properties exclusive to the gel which neither exist in the nanoparticle nor the bulk material as our group showed earlier .
While gelation is an advantageous way for particle assembly up to now the mechanical stability of nanoparticle gels is mostly unsatisfactory. We see the use of silica networks — one of the longest known gel materials — as reinforcement for the nanoparticle gel as an approach to circumvent this problem. We show a novel approach to combine semiconductor nanoparticles and silica into one material all while retaining the initial properties of the particles. Nanocrystalline Semiconductors: Synthesis, Properties, and Perspectives.
Chemistry of Materials. The composite nanofibers were characterized by infrared spectroscopy, scanning electron microscopy and electrochemical measurements. Enzyme activity was preserved and the obtained biosensor enabled successful detection of EE2 by amperometry. In addition, the developed enzymatic biosensor showed good reproducibility with relative standard deviation RSD equal to 4. The results suggest the developed biosensor as a reliable and viable alternative for the analytical determination of EE2 in real sample and environmental analysis.
After annealing the superlattices, spherically shaped Ge nanocrystals with well controlled size and spatial distribution have been formed as confirmed by transmission electron microscopy. Thus, the material system allows the controlled formation of Ge nanocrystals in an amorphous ZrO2-based high-k matrix material. The size and size distribution of the nanocrystals depends strongly on the Ge-TaZrOx composite layer thickness.
The size of the nanocrystals formed from 3 nm and 6 nm thick composite layers corresponds to the layer thickness. Composite layers of 9 nm and 12 nm thickness form two fractions of nanocrystals with different sizes. The size control is thus less suitable for composite layers larger than 6 nm. An additional SiO2 layer underneath the composite layer leads to the formation of larger and better separated Ge nanocrystals. The influence of the matrix material on the formation of the nanocrystals is discussed in detail. Resume : This talk will present the method of self-aligning gas phase electrodeposition and will address applications such as nano interconnects, vias or gas sensors.
Recently, new trends have emerged in the area of interconnects and vias for semiconductor components. The semiconductor industry is now looking for ways to integrate new non-copper-based materials such as ruthenium or new self-aligned technologies into existing production processes.
In contrary to conventional metallization, ruthenium has a better conductivity in the nano range than copper or aluminium. Another interesting feature is the possibility of electrically connecting arbitrary points on the chip. The method of gas phase electrodeposition for self-aligned growth and the fabrication of metallic nanobridges has been reported . In addition, metal electrodes growing vertically upwards were also produced with the gas phase electrodeposition  for photovoltaic applications. The concept becomes particularly interesting when one considers the upcoming idea of nanoscale interlayer vias ILV.
These are necessary if connections between individual thin chips will be enabled in the next chip generation, so that the computing power can be processed massively in parallel. In addition to the general technological trends for optimizing computing power and upstream production processes, the aspects of materials management and environmental compatibility are becoming increasingly important. Processes with the highest possible material yield are of particular interest. In recent years, gas phase electrodeposition has established itself as a very material-saving method.
It enables the locally produced nanomaterial to be selectively captured on the substrate by selective transport in photoresist openings. This achieves a high material yield, which means that expensive materials such as ruthenium or gold, are used economically and efficiently. References  Fang, J. Note: The presentation shows recent research results which will be published in the second half of Resume : One promising solution to increase the solar cells efficiency consists in developing down-converter layers compatible with the silicon industry which absorb UV photons and convert them into IR ones.
To achieve such a goal, rare earth ions doped silicon nitride-based thin films have been deposited by reactive magnetron co-sputtering. This nitride host matrix allows a high RE ions incorporation while avoiding the clustering effect observed in silicon oxide matrices. Moreover, it has been used as an efficient antireflective layer contributing also to a better efficiency of the Si solar cells. Two different co-doping with RE ions have been chosen i. Tb3 -Yb3 and Ce3 -Yb3. The first step of this work is focused on achieving an intense emission of Tb3 or Ce3 ions by optimizing the deposition parameters.
In the case of Tb3 ions, the goal is to enhance the coupling between sensitizers and Tb3 ion activator, whereas in the case of Ce3 ions, the optimized 4f-5d transitions allow achieving a direct efficient excitation of the RE ions. A comparison between the excitation efficiency of each co-doped system will be presented.blotnisurlens.tk
Nanomagnetism and Spintronics: Fabrication, Materials, Characterization and Applications
The excitation mechanisms of Tb3 and Yb3 ions will be discussed. At last, simulations have been performed to find, with help of Bragg mirror, the best density of UV photons trapped in DC layer for a better quantum cutting effect. The additional efficiency has been then calculated.
Resume : Si nanocrystals Si NCs with narrow size distributions and mean sizes of 2 to 5 nm are studied to investigate P- and B-doping of ultra-small Si nanostructures. We explain this observation by i the significantly increased substitutional formation energy, which incorporates a vast majority of dopant atoms on interstitial lattice sites rather than on Si-lattice sites and ii by a significantly increased dopant ionization energy compared to dopants in bulk-Si due to quantum and dielectric confinement effects . Hence, thermal energy at room temperature is not sufficient for dopant ionization in Si NCs.
Hiller, J. Gutsch, M. Zacharias, K. Nomoto, D. Zacharias, M. Wahl, W. Bock, A. Brodyanski, M. Kopnarski, K. Nomoto, J. Valenta, D. Nomoto, M. Bock, T. Chlouba, F. Zacharias, D. Kopnarski, Beilstein J. Resume : Si-based nanoscale devices that exhibit quantum functionalities in their operational characteristics offer new prospects for developments in quantum technologies with areas of application including quantum computing and communications, quantum sensing and metrology.
We have developed considerable experience in design, fabrication and measurement of quantum devices in which ion implantation has been a central part of the fabrication protocol. We have demonstrated single donor addressability, spin initialisation and single shot readout for Si devices implanted with one or a few 31P donors.
Experiments on devices formed in isotopically-pure 28Si epilayers have shown nuclear spin coherence times for 31P donor qubits in excess of 30 s [1,2]. The challenge for the next generation of devices is to develop fabrication and measurement protocols that allow scale-up to small ensembles of coupled qubits. The recently proposed flip-flop qubit architecture offers the prospect of being able to couple donor qubits over relatively large distances of a few hundred nanometres and with donor placement tolerances that are compatible with ion implantation limitations .
To meet the challenge of building devices based on this architecture we have upgraded our deterministic ion implantation method to operate at room temperature. This has required considerable redesign of the on-chip ion impact detection electrode arrangement and development of a device layout that allows for multiple independently targetable construction sites on the one chip to be processed in parallel. Our progress towards meeting this goal will be presented in this talk. At the other implantation fluence extreme we have made devices with nanoscale ring structures that are degenerately doped with either As donors or B acceptors and we have observed novel magneto-transport characteristics at temperatures below the superconducting transition of the aluminium contacts.
We will present details of the characteristics of these devices and our understanding of the magneto-transport features. Pla, K. Tan, J. Dehollain, W. Lim, J. Morton, D. Jamieson, A. Dzurak and A. Morello, A single-atom electron spin qubit in silicon, Nature , Muhonen , J. Dehollain, A. Laucht, F. Hudson, R. Kalra, T. Sekiguchi, K. Itoh, D.
Jamieson, J. McCallum, A. Morello, Storing quantum information for 30 seconds in a nanoelectronic device, Nat. Tosi, F.
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Mohiyaddin, V. Schmitt, S. Tenberg, R. Rahman, G. Klimeck and A. Morello, Silicon quantum processor with robust long-distance qubit couplings, Nature Comm. Resume : Semiconducting nanowires NWs hold promises for functional nanoscale devices . Although several applications have been demonstrated in the areas of electronics, photonics and sensing, the doping of NWs remains challenging.
Ion implantation is a standard doping method in top-down semiconductor industry, which offers precise control over the areal dose and depth profile as well as allows for the doping of all elements of the periodic table even beyond their equilibrium solid solubility . Yet its major disadvantage is the concurrent material damage. A subsequent annealing process is commonly used for the healing of implant damage and the electrical activation of dopants.
This step, however, might lead to the out-diffusion of dopants and eventually the degradation of NWs because of the low thermal stability caused by the large surface—area-to-volume ratio. The approach lies on the implantation of either shallow-level dopants, such as B and P, or deep-level dopants like Se followed by millisecond flash lamp annealing.
In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual NWs at different depth along the NW core. Interfaces , a Corresponding author: y. Resume : Since few years transistors improvement reached a milestone : innovations in the field of architectures and materials are needed to pursue the downscaling. According to ITRS, Gate-all-Around transistors on vertical nanowires are the most promising candidate for the sub-5nm node.
Our aim is to combine the benefits of this architecture with the introduction of a high-mobility channel, namely GaAs, leading to low power, higher performance devices. Here we will present: - Top-Down approach to pattern high-density arrays of vertical GaAs nanowires on Si with controlled dimensions and localization.
Resume : A simple and efficient bottom-up technology for precisely controlling the amount of dopant atoms tethered on silicon substrates is presented. Polystyrene and poly- methyl methacrylate polymers with narrow molecular weight distribution and end-terminated with a P-containing moiety were synthesized with different molar mass.
Nanomagnetism And Spintronics: Fabrication, Materials, Characterization And Applications
The polymers were spin coated and subsequently end-grafted onto nondeglazed silicon substrates. Polymeric material was removed by O2 plasma hashing without affecting the tethered P-containing moieties on the surface. Repeated cycles of polymer grafting followed by plasma hashing led to a cumulative increase, at constant steps, in the dose of P atoms grafted to the silicon surface. P injection in the silicon substrate was promoted and precisely controlled by high- temperature thermal treatments.
Sheet resistance and Hall demonstrated effective doping of silicon substrate and were used to determine the effective activation of the injected P impurities. Resume : I will present emerging strategies for constructing three-dimensional nanostructures whose shapes and symmetries go beyond those of the bulk equilibrium diblock copolymer phase diagram. Photo-thermal methods are used to control block copolymer ordering; ordered layers can be stacked to yield new lattice symmetries.
This multi-layered strategy can also be performed in a responsive mode, where each self-assembled layer templates the ones that follow. Finally, I describe how blending allows the self-assembling film morphology itself to be responsive to underlying guide patterns. Taken together, these new motifs represent a toolbox for constructing 3D nanostructures with symmetries and complexity beyond conventional self-assembled morphologies.
Resume : The helium ion microscope HIM is a charged particle microscope employing helium ions for probing the sample. In the low dose regime, the HIM operates as microscope, high doses enable material modification and sputtering. Compared to conventional focussed ion beams FIB using metal ions like gallium, the HIM offers a very small focal spot size down to 0.
In this talk, I will present examples of imaging and local milling of two-dimensional nanostructures with helium ion microscopy. In particular, carbon nanomembranes CNMs and graphene will be discussed.
CNMs are made by a combination of molecular self-assembly, radiation-induced cross-linking and the detachment of the cross-linked monolayer from its substrate. I will demonstrate that the HIM is particularly well suited for imaging such insulating membranes due to its efficient charge compensation tool. Effects of sample charging, imaging of multilayers and imaging artefacts for CNMs as a model system will be discussed.
Furthermore, it will be shown that the focused helium ion beam of the HIM can be utilized to create nanopores in insulating as well as conducting membranes. In CNMs, pore diameters were realized down to 1. An analysis of the nanopore growth behaviour allows determination of the profile of the helium ion beam.
Resume : The dewetting process of ultra-thin homopolymeric films has been widely studied in the past years for its potential technological application in coatings for corrosion protection or functional surfaces In this perspective, the possibility to associate the nano-scale pattern typical of the self-assembly SA of Block Copolymer BCP films to the micro-scale dewetting allows to conceive a new class of materials with improved capabilities and potential application in fields like biological sensing or photonics.
In this work the effect of the dewetting process on the SA characteristics i. The dewetting of BCP films with thickness between 2 nm and 15 nm was found to be strongly different when induced on Random Copolymers RCP systems with different thickness. In particular we considered RCPs having grafting thickness between 2 and 10 nm. When BCP dewets on thin RCPs the ordering of the nanometric cylinders considerably increases, far exceeding the correlation length values obtained in thick continuous BCP films.
As a result, circular micrometric droplets composed by a single and defectless grain are generated and randomly distributed on the substrate. The control over the position of the droplets was achieved resorting to large-scale chemical patterns obtained by laser lithography and plasma etching. By properly adjusting the periodicity of the chemical pattern and the substrate wettability it was possible to tune and select the shape of the dewetted droplets in terms of maximum thickness, contact angle and diameter, thus creating highly ordered hierarchical patterns at nanometric scale.
Resume : The self-assembly of block copolymers BCPs into ordered nanostructures is a highly attractive bottom-up technique for the creation of arrays of regular nanofeatures on large surface areas. Applying BCP lithography on pre-patterned surfaces makes this technique even more versatile as the directed self-assembly allows for more complex and hierarchical nanopatterns. The combination of these two self-assembly techniques will be shown to allow for the creation of ordered hierarchical nanostructures, while maintaining the advantages of low-cost, large-area surface nanopatterning.
Applying SEM, AFM, surface energy investigations and TEM, we present the creation of either arrays of hierarchical nanopores or hierarchical concentric nanorings by steering the BCP-surface interactions during self-assembly. The hierarchical nanopores consist of sub nm nanopores site-selectively formed inside arrays of nm-diameter nanohole arrays in different material thin films. Tuning the self-assembly process can be used to generate concentric polymer nanorings inside the circular nanoholes. These tunable hierarchical nanostructures are suitable for advanced lithographical surface patterning or can act as templates for nanoobject positioning.
Resume : Synthesis. Different types of nanowires NWs were obtained by template synthesis technique using different polymer matrixes. Metals were deposited using galvanic technique. Cu and Ag were deposited in pure state, while for Fe, Co and Ni different types of deposition were used for obtaining pure, alloys and layered NWs. Samples of Cu and Ag NWs were used as substrates for deposition of probes in mass-spectrometer.
Such structures could be effectively used for desorption and emission of biological molecules-due to small radius of curvature. The dependences of emission intensity on laser intensity and surface density of NWs were investigated. The last one was found to be non-linear- due to saturation effect. Microscopy and X-ray analysis. Mossbauer spectra of Fe NWs: it was found that spectra depend on pores diameter. For thick NWs the spectra were the same as for bulk material.
For thin NWs the intensity ratio of sextet was different from due to orientation and presence of defects Magnetic measurements were carried out - all samples are ferromagnetic. Work was supported by the FASO agr. Resume : Bottom-up grown silicon nanowires are targeted to be applied as nanoscale transducers or building blocks for advanced sensors and devices exploiting their electrical, mechanical and optical properties. Hence, controlled and well-ordered synthesis of silicon nanowires as well as the elucidation of the relevant growth mechanisms is highly relevant and in the focus of research already since the last two decades.
So far, well-controlled epitaxial bottom-up synthesis of silicon nanowires by the vapor-liquid-solid synthesis using nanoscale metal catalysts was only realizable on pristine silicon crystal surfaces requiring native oxide removal, e. The basic idea is here that aluminum will disintegrate first the native silicon oxide by forming Al-O compounds while simultaneously forming an AlAu2 liquid alloy droplet that precipitates the Si nanowire in epitaxial relation with the silicon substrate. The crystallinity of the silicon nanowires as well as the catalyst composition were examined by scanning electron and high resolution transmission electron microscopy.
The nanowires are single-crystalline and grow in direction similarly to Au- and Al-catalyzed silicon nanowires as reported elsewhere. By utilizing this growth strategy, well-ordered silicon nanowire arrangements were created on silicon and substrates. Notably these nanowires show also a high degree of perpendicular branching and self-welding. This might enable new strategies for the assembly of unique nanostructured materials and 3D nanowire electronic systems. Resume : The bottom-up synthesis of crystalline silicon nanowires SiNWs by using a variety of metal catalysts Au, Ag and Pt was extensively studied during the past decades.
Here, SiNWs were frequently discussed as nanoscale building blocks for various applications, ranging from electronics to sensing and even to photonics. However, silicon contamination by the metal catalyst is an omnipresent issue because already minute concentrations of metal atoms in silicon can degrade the electronic and optical properties by the generation of deep trap states.
Hence, alternative synthesis methods are required but must be established. The process is expected to be triggered by reactive-oxide as per the so-called oxide-assisted growth mechanism, which was proposed elsewhere. Silicon nanoparticles are consistently embedded in the nanowire tip and already present during the SiNW nucleation. We show that plain KOH treatment of silicon can be utilized to generate reliably these trigger points in dependence on the KOH concentration and Si substrate crystal orientation. Consequently, local KOH substrate pre-treatment allowed to confine the nanowire growth to these areas only.
Resume : Among many different types of nanostructures, magnetic nanoparticles are probably the most widely used one. For many applications, thermal stability of magnetic nanoparticles, is very important subject. This is especially crucial when they are considered to be applied in magnetic hyperthermia treatment, for example. It was observed that thermal evolution is influenced by the fabrication process. Conducted studies show that doping of different 3d element prevents the oxidation process of ferrite nanoparticles what, therefore, gives new possibilities of their application.
The range of restriction depends on the element and its amount. Resume : The unrecognized segregation of metallic ferromagnetic nanocrystals in dilute ferromagnetic semiconductors DFS is an important issue which, if not recognized, can lead to misleading conclusions. Ga,Mn As — a canonical DFS material is an excellent model system to study the intentionally induced phase segregation of magnetic, Mn-rich nanocrystals inside the GaAs semiconductor matrix.
Even moderate thermal annealing — C causes decomposition of Ga,Mn As solid solution into ensemble of MnAs nano-inclusions randomly dispersed in the GaAs lattice. Dimensions of such MnAs nanocrystals NCs depend on the annealing procedure details and are in the range of 5 — 50 nm. NCs can occur either in hexagonal phase, typical for MnAs bulk larger nanocrystals , or in the cubic phase imposed by the surrounding zinc-blende matrix smaller nanocrystals.
Moreover nanowire geometry allows for controlling the distribution of nanocrystals both in radial and axial direction. In parallel to the samples annealed directly after the MBE growth we have also performed in-situ annealing experiments in the transmission electron microscope, enabling recognition of the beginnings of the MnAs phase segregation process.
Resume : Magnetic nanoparticles NPs are a well-known and attractive class of materials, with applications in different fields, going from catalysis to biomedical applications. Here, we show the preparation of different colloidal bi-magnetic core-shell systems, followed by a cation exchange CE procedure to focus on the role of the host NPs crystal structure.
To achieve this goal, we performed in-depth morphological, structural, spatially resolved chemical and magnetic behavior analyses of the initial and cation-exchanged NPs. In turn, this gave rise to dramatic effects in terms of magnetic behavior of the final NPs. Resume : Nanocomposites are considered the most propulsion materials with extraordinary potential for functional applications in top-level domains from the biomedical, optoelectronic to the aerospace industry. This paper present the main steps for ex-situ synthesis and characterization of nanocomposite materials based on a PMMA matrix and an inorganic oxide Y2O3 at different concentrations in the matrix and in the presence of solvent associated with the matrix.
The SEM images of the Y2O3 nanoparticles tend to form aggregates, but by proposed method for embedding in the PMMA matrix it has been found a good dispersion, with the formation of small agglomerates depending on the Y2O3 particle content. The FTIR spectra for all samples confirm bands below cm-1 characteristic metal-oxygen Y-O , but also the absorption bands characteristic of the polymer matrix.
X-ray diffraction analysis XRD show the phase types, diffraction patterns and the average crystallites dimension ranging between nm. Compared to nanoparticles, the XRD of nanocomposites does not reveal any structural change. Following the obtained results were created premises for applications of the nanocomposite materials in the aerospace and other related fields. Resume : Conversion of mechanical energy into electrical energy and vice versa in piezoelectric materials have a wide range of applications in energy harvester, sensors, and actuators. Antiparallel stacking sequence in semiconducting transition metal dichalcogenides TMDs bulk crystal makes it centrosymmetric thus nonpiezoelectric.
Contrary, piezoelectricity in mono or odd layers arises from broken inversion symmetry in many two-dimensional 2D TMDs can be utilized for efficient exfoliation processes. Owing to distinctive physical properties and emerging applications, 2D tungsten disulfide WS2 has become one of the most extensively studied TMDs in the recent years. Here we demonstrate an experimental process to improve exfoliation efficiency of WS2 using an external electric field. We successfully able to thin down and enhance the exfoliation efficiency by exploiting the intrinsic piezoelectric nature of WS2.
The nanosheets produced in the liquid phase by our developed method are relatively small in size and free from any apparent defects. The developed approach can lead to new possibilities of large-scale production of non-centrosymmetry 2D layered materials for the applications in electronics, optoelectronics, and energy harvesting devices. Resume : A self-oil cleaning surface in-air and underwater was presented on hygroscopic fabrics having the high aspect-ratio AR nano-hairy patterns. The nanopatterns with a wide range of ARs, defined as the ratio of the height over the width, were formed on the cellulose fabric by selective plasma etching with the different gas flow rate and treatment duration.
Pristine fabrics show low adhesion for low viscous crude oil, but very high for high viscous Bunker C oil in water.
However, the nanostructured cellulose fabrics with high AR of more than 1. Performed by a cross-sectional analysis under cryo condition, it was found that unlike the oil residues strongly adhered on the pristine, an oil residue on nanostructured cellulose fibers were found to have high wetting angle and low adhesional contact on water film coated nanostructures. Self-oil cleaning test was also performed in-air, revealing that the continuous flow of water droplets lift oil up and easily cleaned the oil-contaminated surface with nano-hary.
As worked in-air and underwater, the hygroscopic sieve with the self-oil cleaning surface showed the high efficiency and robust in oil recovery capacity from oil-water mixture over time. Resume : TiO2 has three naturally occurring polymorphs, i. The synthesis of pure brookite is generally much more difficult than that of pure anatase or rutile. Our group investigated conditions of Mg2TiO4 preparation and hydrothermal conversion to brookite. Kozawa et al. Machida et al. Size and shape of particles affect material properties.
Here, we intend to control the size and shape of brookite nanopowders. Brookite TiO2 powders were synthesized by the hydrothermal conversion method using Mg2TiO4 as a precursor. This precursor powders and HCl aq. Microstructure, particle size, and specific surface area were evaluated. Additional ball-milling effect was also studied. Resume : Surface-enhanced Raman scattering SERS provides dramatically intensified Raman signals for the molecules near metal nanostructures.
However, the surface of the metal nanostructure is prone to contamination by adhesive proteins for most biological samples, which restricts the use of SERS. The aim of this study is to design SERS-active microgels with molecular selectivity and signal reproducibility by embedding highly-concentrated gold nanoparticles in the matrix of hydrogel microspheres. With a capillary microfluidic device, water-in-oil-in-water double-emulsion drops were prepared, of which water core contains gold nanoparticles and hydrogel precursors.
To concentrate gold nanoparticles, water was pumped out through the oil shell by imposing positive osmotic pressure. The concentration of nanoparticles increases in a factor of in the absence of aggregation. Finally, microgels containing highly-concentrated gold nanoparticles were suspended in water after polymerizing hydrogel precursors and rupturing the oil shell. As the homogeneous hydrogel matrix allows diffusion of molecules smaller than mesh size, gold nanoparticles were free from protein contamination.
At the same time, microgels also provided high reproducibility of Raman intensity as nanogap-forming gold nanoparticles were evenly embedded in the whole volume of microgels. Therefore, the microgels are useful for direct detection of small molecules dissolved in complex biological fluids such as blood and urine. This is close to room temperature and around working temperature of many electronic devices. Thus, it is possible to modulate the transition by some energy transfer by external electric, magnetic or optical means.
This transition is often recognized for the change of several orders of magnitude of the conductance and the optical absorption. Consequently, VO2 can be used for electric, optical or electromagnetic switches. Other applications can exploit the optical properties within this transition region to control and tune the refractive index between its insulating and metallic states. Additionally, electron beam evaporation is attractive as a large area, cost-effective and low temperature method of deposition.
Peak frequencies, full-width half-maxima, binding energies and oxidation states from the PL, Raman and XPS experiments are reported and analyzed for all the phases encountered in the VO2 thin films. Resume : Electromigration is one of the main reason for failure of conducting paths i. A high electron flux passing through interconnects lead to displacement of the conducting material at atomic scale. Voids and hillocks form at the cathodic and anodic sides, respectively. Temperature plays a crucial role in the mass transport leading to device failure.
A new hot topic on developing 2. The current study focuses on a systematic investigation of base vias materials such as Al and Cu. Statistic measurements obtained on predefined 2D wires are used as background for development of new materials. The crystallographic particularities of the conducting paths are analyzed and the initial phase of the electromigration mechanism is described as depending on the grain boundary stress induced evolution.
The blocking effect of anodic oxide growth has been studied on void formation and pinning on the conductor surface. A combinatorial approach is used for fabrication of Al-Cu thin film alloys by sputtering co-deposition. A wide compositional range is screened and electromigration resistance is assessed along the compositional gradient. The effect of surface oxide on the conductor performance at high current densities is compositionally studied. Additionally, the effect of temperature is studied on the mass transport and the best Al-Cu vias alloys are identified.
Radiative cooling based upon optimising thermal emissivity of a surface in the atmospheric transparent region of the electromagnetic spectrum is one such technology which has great potential. One method for increasing the emissivity of a device is to out-couple surface phonon polaritons SPhPs , which exist in polar dielectric materials such as SiO2, via means of diffraction from a surface periodic structure.