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This paper introduces novel possibilities of using recently developed high-power lasers for high-speed surface periodic structuring/patterning of the ceramic substrates for the subsequent thermal spray coating deposition, which may be difficult to pattern using conventional methods. Yttria-stabilized zirconia (YSZ) was selected as model ceramic for both substrates and coating. Three different types of patterns were produced by three different laser technologies: dimples with nominal depth of 15 and 30 µm (pulsed nanosecond laser), grids with nominal depth of 15 and 30 µm (continuous wave laser), and pillars with nominal depth 30 µm (ultrashort pulsed femtosecond laser). All surface patterns were thoroughly periodical and their surface roughness ranged from Sa = 4.5 to 10.3 µm, significantly surpassing conventional grit-blasting. Pulsed and continuous wave lasers showed very high process rates (up to 54.5 mm2/s and 323.6 mm2/s, respectively) and tendency to develop network of shallow surface cracks. Ultrashort pulsed laser technology was slower (process rate 1.65 mm2/s) but the surface was crack-free with desirable miniature anchoring points. Plasma spraying was carried out with powder, solution, and suspension feedstocks providing an experimental matrix demonstrating potential benefits and risks of each pattern-feedstock combination. Not all combinations led to successful coating deposition, but results show that microstructure of the coating may be deliberately controlled by laser texturing, in particular periodic substrate pattern led to periodic coating microstructure in the case of suspension spraying. Also adhesion/cohesion of the coating to the substrate may be in many cases significantly improved by laser patterning of the substrate. The highest coating adhesion/cohesion strength (26.2 ± 4.8 MPa) was achieved for the coating deposited from solution on pillar patterns. Finally, a possibility to combine the high-speed and advanced surface morphology produced by continuous wave and femtosecond lasers, respectively, and direct patterning of plasma sprayed coating were also demonstrated. [ABSTRACT FROM AUTHOR]

Herein, we focus on the performance optimization of inclined sidewall (IS) type ultraviolet (UV) light-emitting diodes (LEDs) with either nanopatterned sapphire substrates (NPSSs) or photonic crystals (PCs). The simulation results demonstrate the introduction of substrate patterning plays a crucial role in unlocking the potential of IS type UV LEDs by reducing the generation of high mode resonance within the device. The use of NPSSs design performs exceptionally well in extracting transverse-magnetic (TM) polarized light due to its superior alignment with the inclination design. As a result, the total light extraction efficiencies (LEEs) are significantly improved, increasing from 36.0 to 57.3%. [ABSTRACT FROM AUTHOR]

Patterned functionalization can, on the one hand, open the band gap of graphene and, on the other hand, program demanding designs on graphene. The functionalization technique is essential for graphene‐based nanoarchitectures. A new and highly efficient method was applied to obtain patterned functionalization on graphene by mild fluorination with spatially arranged AgF arrays on the structured substrate. Scanning Raman spectroscopy (SRS) and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy (SEM‐EDS) were used to characterize the functionalized materials. For the first time, chemical patterning on the bottom side of graphene was realized. The chemical nature of the patterned functionalization was determined to be the ditopic scenario with fluorine atoms occupying the bottom side and moieties, such as oxygen‐containing groups or hydrogen atoms, binding on the top side, which provides information about the mechanism of the fluorination process. Our strategy can be conceptually extended to pattern other functionalities by using other reactants. Bottom‐side patterned functionalization enables utilization of the top side of a material, thereby opening up the possibilities for applications in graphene‐based devices. [ABSTRACT FROM AUTHOR]

Ordered arrays of vertically aligned semiconductor nanowires are regarded as promising candidates for the realization of all-dielectric metamaterials, artificial electromagnetic materials, whose properties can be engineered to enable new functions and enhanced device performances with respect to naturally existing materials. In this review we account for the recent progresses in substrate nanopatterning methods, strategies and approaches that overall constitute the preliminary step towards the bottom-up growth of arrays of vertically aligned semiconductor nanowires with a controlled location, size and morphology of each nanowire. While we focus specifically on III-V semiconductor nanowires, several concepts, mechanisms and conclusions reported in the manuscript can be invoked and are valid also for different nanowire materials.

Plasma sprayed W-based coatings have the potential application as joining interlayers for the plasma-facing components of future fusion reactors. Particularly in the form of tungsten-steel functionally graded materials (FGMs), they would reduce the stress concentration between the W-based plasma-facing armor and steel-based construction. For mechanical integrity, good adhesion is essential. For this, conventional grit blasting treatment of the substrate may not be sufficient. Therefore, alternative treatments capable of reaching significantly higher roughness without damaging the substrate are sought. In this study, the effects of laser texturing on the adhesion of plasma sprayed W and W-steel FGMs on W and steel substrates are investigated. A variety of surface profiles were achieved by controlled laser ablation in several types of patterns. Their geometric features were systematically varied and measured, and the extent of their filling by the coating material was evaluated. On the most promising patterns, coating adhesion tests were performed in shear loading mode and the best performing patterns were identified. Significant improvement over grit-blasted surface was obtained on patterned surfaces with a high effective contact area, promoting mechanical interlocking. On steel substrates, generally higher adhesion was observed, surpassing already the coating cohesive strength; this is attributed to a combination of mechanical interlocking and metallurgical bonding. [ABSTRACT FROM AUTHOR]

It is well-known that the performance of thin film organic electronic devices critically depends on the active layer microstructure. Since processing conditions heavily influence the microstructure, identifying optimal fabrication conditions is a crucial step towards the development of high-performance devices. Current state-of-the-art approaches remain predominantly trial-and-error, which are time and resource intensive. In this work, we integrate a morphology evolution framework (based on a phase-field model) with a heuristic optimization scheme to systematically identify promising processing conditions. We show how annealing time and substrate patterning can be simultaneously tuned to achieve a variety of tailored microstructures. The appropriate choice of cost functional is critical to achieving meaningful results. The methodology presented here provides a scalable and extensible approach towards the rational design of tailored microstructures with enhanced functionalities. [ABSTRACT FROM AUTHOR]

Hall measurement of an electrodeposited Cu2O film is rendered difficult as the bilayer structure of semiconductor on top of a conductive substrate obviates the measurement. Here, we propose the use of a patterned Au on glass substrate in line/space configuration for the Hall measurement of electrodeposited Cu2O. A continuous, (111) oriented Cu2O film was electrodeposited on 8 μm/2 μm Au‐line/space on glass substrate and Hall measurement was performed. The room temperature Hall measurement of the Cu2O film on the patterned substrate indicates p‐type conduction with a hole concentration of 2.2 × 1017 cm−3 and mobility of 4.7 × 10−3 cm2 V−1 s−1. Additionally, the temperature dependent resistivity exhibits a negative slope that is characteristic of a semiconductor. Therefore, the measured electrical characteristics can be attributed to the electrodeposited Cu2O semiconductor film rather than the conductive substrate. This method can be applied for the Hall measurement of any other electrodeposited semiconductor by optimizing the line/space geometry of the conductive substrate. [ABSTRACT FROM AUTHOR]

We report preliminary results on InGaP/InGaAs/Ge photovoltaic cells for concentrated terrestrial applications, monolithically integrated on engineered Si(001) substrates. Cells deposited on planar Ge/Si(001) epilayers, grown by plasma-enhanced chemical vapor deposition, provide good efficiency and spectral response, despite the small thickness of the Ge epilayers and a threading dislocation density as large as 107/cm2. The presence of microcracks generated by the thermal misfit is compensated by a dense collection grid that avoids insulated areas. In order to avoid the excessive shadowing introduced by the use of a dense grid, the crack density needs to be lowered. Here, we show that deep patterning of the Si substrate in blocks can be an option, provided that a continuous Ge layer is formed at the top, and it is suitably planarized before the metalorganic chemical vapor deposition. The crack density is effectively decreased, despite that the efficiency is also lowered with respect to unpatterned devices. The reasons of this efficiency reduction are discussed, and a strategy for improvement is proposed and explored. Full morphological analysis of the coalesced Ge blocks is reported, and the final devices are tested under concentrated AM1.5D spectrum. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ultrafast evolutions model of a femtosecond laser act on GaN is established. • The transient nonlinear evolutions of GaN are simulated. • The laser ablation morphology of the GaN film is predicted. Lateral epitaxial growth is an effective method to reduce dislocations in Gallium Nitride (GaN) films. Compared to heteroepitaxy, the homoepitaxial growth films have lower stress. However, its application is limited due to the complex processes and high cost. In recent years, femtosecond laser technology has been applied in wide bandgap semiconductor processing increasingly due to its high instantaneous power density and excellent photon absorption rate. In the homoepitaxial growth of GaN, the femtosecond laser technology used for processing in-situ patterns is an effective method to reduce dislocations. Moreover, the laser equipment is relatively simple and compact, easy to be integrated into an in-situ growth cavity. However, there is still a lack of research on the mechanism of ultrafast laser processing of pattern windows on GaN substrates. In our study, the model of the transient nonlinear evolutions of femtosecond laser acting on GaN is established to solve partial differential equations with coefficients of the GaN film and the laser. The optical and electrical properties, such as the laser intensity and reflectivity, can be obtained. In addition, the ablation morphology of GaN can be predicted. The results show that under the action of the femtosecond laser with a power intensity of 0.6 J/cm2 and a wavelength of 1030 nm, numerous free electrons are generated on the GaN surface, and the reflectivity increases to 0.94. The electron temperature rises to 9750 K and then decreases. While the lattice temperature rises slowly, reaching 2060 K around 4 ps, which is in equilibrium with the electron temperature. The ablation pit on the thin film surface has a radius of 1 μm and a depth of 0.2 μm. The simulation results are consistent with the current theoretical and experimental results, which are helpful in further revealing the transient nonlinear mechanism of ultrafast laser acting on GaN. Under our simulation conditions, the femtosecond laser technology can be applied to process the sub-micron-sized patterns, which provides a more theoretical basis for preparing the GaN in-situ growth patterns. [ABSTRACT FROM AUTHOR]

Integration of solvothermal reaction products into complex thin-layer architectures is frequently achieved by combinations of layer transfer and subtractive lithography, whereas direct additive substrate patterning with solvothermal reaction products has remained challenging. We report reactive additive capillary stamping under solvothermal conditions as a parallel contact-lithographic access to patterns of solvothermal reaction products in thin-layer configurations. To this end, corresponding precursor inks are infiltrated into mechanically robust mesoporous aerogel stamps derived from double-network hydrogels. The stamp is then brought into contact with a substrate to be patterned under solvothermal reaction conditions inside an autoclave. The precursor ink forms liquid bridges between the topographic surface pattern of the stamp and the substrate. Evaporation-driven enrichment of the precursors in these liquid bridges, along with their liquid-bridge-guided conversion into the solvothermal reaction products, yields large-area submicron patterns of the solvothermal reaction products replicating the stamp topography. For example, we prepared thin hybrid films, which contained ordered monolayers of superparamagnetic submicron nickel ferrite dots prepared by solvothermal capillary stamping surrounded by nickel electrodeposited in a second orthogonal substrate functionalization step. The submicron nickel ferrite dots acted as a magnetic hardener, halving the remanence of the ferromagnetic nickel layer. In this way, thin-layer electromechanical systems, transformers, and positioning systems may be customized.

Abstract: Solvent-based thin-film deposition constitutes a popular class of fabrication strategies for manufacturing organic electronic devices like organic solar cells. All such solvent-based techniques usually involve preparing dilute blends of electron-donor and electron-acceptor materials dissolved in a volatile solvent. After some form of coating onto a substrate to form a thin film, the solvent evaporates. An initially homogeneous mixture separates into electron-acceptor rich and electron-donor rich regions as the solvent evaporates. Depending on the specifics of the blend, processing conditions, and substrate characteristics different morphologies are typically formed. Experimental evidence consistently confirms that the resultant morphology critically affects device performance. A computational framework that can predict morphology evolution can significantly augment experimental analysis. Such a framework will also allow high throughput analysis of the large phase space of processing parameters, thus yielding considerable insight into the process–structure–property relationships governing organic solar cell behavior. In this paper, we formulate a computational framework to predict evolution of morphology during solvent-based fabrication of organic thin films. This is accomplished by developing a phase field-based model of evaporation-induced and substrate-induced phase-separation in ternary systems. This formulation allows most of the important physical phenomena affecting morphology evolution during fabrication to be naturally incorporated. We discuss the various numerical and computational challenges associated with a three dimensional, finite-element based, massively parallel implementation of this framework. This formulation allows, for the first time, to model three-dimensional nanomorphology evolution over large time spans on device scale domains. We illustrate this framework by investigating and quantifying the effect of various process and system variables on morphology evolution. We explore ways to control the morphology evolution by investigating different evaporation rates, blend ratios and interaction parameters between components. [Copyright &y& Elsevier]

Abstract: The heteroepitaxy of semiconductor pairs with a small lattice mismatch is a process of tremendous interest in materials science and technology. The principal mechanism of strain relief in these interfaces is the formation of three dimensional islands either directly on a bare substrate (Volmer–Weber growth mode) or following the formation of an initially flat wetting layer (Stranski–Krastanov growth mode). The elemental and strain inhomogeneities associated with these three dimensional islands may result into a confinement potential for electrons and/or holes, as in a standard quantum well. At variance with a standard quantum well, the confinement in these nanostructures (often referred to as ‘quantum dots’ (QDs)) occurs in all three spatial dimensions and over length scales comparable with the relevant De Broglie wavelength. This strong confinement may give rise to a discrete spectrum of charge carrier energy levels, as in an artificial atom. On the other hand the spectra of these nanostructures may be tuned with their physical and chemical properties, providing an enabling opportunity to design novel optical and electronic components. Epitaxial nanostructures are proposed as the building blocks of a variety of innovative applications, which may represent step-change solutions to many challenges in the fields of photonics and electronics, such as e.g. new possibilities to integrate versatile lasers and transistors in Information and Communication Technologies and to replace MOSFET devices with miniature components capable of sustaining the race to miniaturization of integrated circuits. Examples of possible applications include lasers, optical detectors, white-light sources, single-photon and entangled-pair sources, single electron transistors, quantum cellular automata, quantum bits, etc. To harness these properties and bring these functionalities to fruition, the ability to manufacture individual QDs may be not enough. Rather, the next critical issue is to gain control over the location of nanostructures with respect to each other and their surroundings, both on a surface and in a three dimensional architecture. The exploration of this issue is essential to engineer nanostructure density, mutual interactions (hybridization of electron energy levels, charge interactions, spin interactions, etc.) and the interface with the external circuitry (electrodes, gates, wires, etc.). Moreover in some applications the principal feature is the layout of a huge number of QDs with respect to each other''s nearest neighbours (as e.g. in a laser), whereas in other applications it is the precise location of a possibly smaller number of QDs within a complex architecture (as e.g. in an SET or QCA platform). An ample variety of natural (bottom–up, parallel) and artificial (typically integrated top–down and bottom–up, sequential and/or parallel) methods have been reported to yield some extent of control over nanostructure positioning. This review aims at highlighting some of the most relevant concepts developed over recent years. While a significant number of reviews on different aspects of the synthesis and characterization of individual nanostructures are found in the literature, the complexity of the issues mentioned above has never been addressed within a dedicated framework so far. [Copyright &y& Elsevier]

It is demonstrated that, besides classical nanocolumnar arrays, the oblique angle geometry induces the growth of singular structures in the nanoscale when using wisely designed patterned substrates. Well-ordered array of crosses, cylindrical nanorods or hole structures arranged in square or hexagonal regular geometries are reported as examples, among others. The fundamental framework connecting substrate topography and film growth at oblique angles is presented, allowing the use of substrate patterning as a feasible thin film nanostructuring technique. A systematic analysis of the growth of TiO 2 thin films on 4 different lithographic patterned substrates in 4 different scale lengths is also presented. A first conclusion is the existence of a height-based selective growth in the initial stages of the deposition, by which the film preferentially develops on top of the tallest substrate features. This behavior is maintained until the film reaches a critical thickness, the so-called Oblivion Thickness, above which the film topography becomes gradually independent of the substrate features. A general formula relating the spatial features of the pattern, the coarsening exponent and the Oblivion Thickness has been deduced. [Display omitted] • Thin film nanostructuring by substrate patterning at oblique angle is demonstrated. • A height-based selective growth principle is deduced for the first stages of growth. • A relation between growth modes, pattern wavelengths and growth exponent is found. • The growth on 16 different patterned substrates corroborates the theory. • Films made of well-ordered arrays of nanorods with thickness up to ~1 μm are shown. [ABSTRACT FROM AUTHOR]

A new method is proposed and developed to measure adhesive forces by use of the force-distance curve of a micro cantilever with an extremely small amount of testing material such as adhesive proteins. The contact area should be well-controlled at a reasonable value. Even though the area is desired to be as small as possible, a contact region of several micrometers by several micrometers is adopted in order to avoid obtaining meaningless measured values and uncertainty in the contact areas. An AFM cantilever is used after having been modified with a micro glass bead to enlarge the contact area for adhesion. A glass plate with micro-scale circular patterns is fabricated from a glass wafer by micro-machining processes in order to control precisely the contact area in adhesion tests. In the proposed method the adhesive materials are directly applied to the bead attached at the AFM cantilever before it is applied on the top area of the truncated cone on the fabricated glass plate. The developed method is applied to measure the adhesive forces of Cell-Tak® (which is a commercial extracted mussel adhesive) and recombinant Mgfp-5 (which is a recombinant mussel adhesive protein) and the statistical credibility of the measured adhesive force data is enormously improved as a result. [ABSTRACT FROM AUTHOR]

We report a new method for the natural reduction of threading dislocations in GaAs on Si by growing on patterned Si substrates. We also explore other effects of patterning on dislocation formation during growth: stress relief near the mesa edges at high aspect ratios, and limited dislocation nucleation and propagation. Prior to growth, the Si substrates were processed to produce a plurality of mesas varying in width (5-170 μm) and geometry (circular, rectangular, and square mesas). After growth of the GaAs, the material was characterized with cathodoluminescence (CL) and secondary electron microscopy. For a GaAs growth temperature of 570° C and a thickness of 10 μm, the GaAs grown on the 40μ-wide Si mesas show a factor of 1.6 increase in luminescence intensity over the luminescence intensity from the unpatterned control area. Also, the emission wavelength from the smaller mesas is shifted to shorter wavelengths as compared to GaAs/GaAs and the unpatterned control area. The emission wavelength and CL intensity varies across the mesas; for 40 μm wide mesas, the emission wavelength is fairly constant across the mesa and the CL intensity decreases near the edges, whereas for larger mesas the emission wavelength decreases and the CL intensity increases at the mesa edges. For the 40 μm wide mesas, the integrated CL intensity is equal to that of a control GaAs/GaAs grown with the same doping level. No cracks were observed in the GaAs grown on the Si mesas, even though the thickness of the GaAs was 10 μ,m. [ABSTRACT FROM AUTHOR]

Ordered arrays of vertically aligned semiconductor nanowires are regarded as promising candidates for the realization of all-dielectric metamaterials, artificial electromagnetic materials, whose properties can be engineered to enable new functions and enhanced device performances with respect to naturally existing materials. In this review we account for the recent progresses in substrate nanopatterning methods, strategies and approaches that overall constitute the preliminary step towards the bottom-up growth of arrays of vertically aligned semiconductor nanowires with a controlled location, size and morphology of each nanowire. While we focus specifically on III-V semiconductor nanowires, several concepts, mechanisms and conclusions reported in the manuscript can be invoked and are valid also for different nanowire materials. [ABSTRACT FROM AUTHOR]

Frontispiz: Spatially Resolved Bottom-Side Fluorination of Graphene by Two-Dimensional Substrate Patterning Keywords: ditopic functionalization; fluorination; graphene; substrate patterning EN ditopic functionalization fluorination graphene substrate patterning 1 1 1 04/11/20 20200420 NES 200420 B Graphen b In der Zuschrift auf S. 6766 demonstrieren A. Hirsch et al. die beidseitige Funktionalisierung von Graphen mit F-Atomen an der Unterseite und O-haltigen Gruppen oder H-Atomen an der Oberseite. Ditopic functionalization, fluorination, graphene, substrate patterning. [Extracted from the article]

Supercapacitors combine the advantages of electrochemical storage technologies such as high energy density batteries and high power density capacitors. At 5-10 W h kg -1 , the energy densities of current supercapacitors are still significantly lower than the energy densities of lead acid (20-35 W h kg -1 ), Ni-metal hydride (40-100 W h kg -1 ), and Li-ion (120-170 W h kg -1 ) batteries. Recently, graphene-based supercapacitors have shown an energy density of 40-80 W h kg -1 . However, their performance is mainly limited because of the reversible agglomeration and restacking of individual graphene layers caused by π-π interactions. The restacking of graphene layers leads to significant decrease of ion-accessible surface area and the low capacitance of graphene-based supercapacitors. Here, we introduce a microstructure substrate-based method to produce a fully delaminated and stable interconnected graphene structure using flash reduction of graphene oxide in a few seconds. With this structure, we achieve the highest amount of volumetric capacitance obtained so far by any type of a pure carbon-based material. The affordable and scalable production method is capable of producing electrodes with an energy density of 0.37 W h cm -3 and a power density of 416.6 W cm -3 . This electrode maintained more than 91% of its initial capacitance after 5000 cycles. Moreover, combining with ionic liquid, this solvent-free graphene electrode material is highly promising for on-chip electronics, micro-supercapacitors, as well as high-power applications.

Defect-free mismatched heterostructures on Si substrates are produced by an innovative strategy. The strain relaxation is engineered to occur elastically rather than plastically by combining suitable substrate patterning and vertical crystal growth with compositional grading. Its validity is proven both experimentally and theoretically for the pivotal case of SiGe/Si(001)., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The move from dimensional to functional scaling in microelectronics has led to renewed interest toward integration of Ge on Si. In this work, simulation-driven experiments leading to high-quality suspended Ge films on Si pillars are reported. Starting from an array of micrometric Ge crystals, the film is obtained by exploiting their temperature-driven coalescence across nanometric gaps. The merging process is simulated by means of a suitable surface-diffusion model within a phase-field approach. The successful comparison between experimental and simulated data demonstrates that the morphological evolution is driven purely by the lowering of surface-curvature gradients. This allows for fine control over the final morphology to be attained. At fixed annealing time and temperature, perfectly merged films are obtained from Ge crystals grown at low temperature (450 °C), whereas some void regions still persist for crystals grown at higher temperature (500 °C) due to their different initial morphology. The latter condition, however, looks very promising for possible applications. Indeed, scanning tunneling electron microscopy and high-resolution transmission electron microscopy analyses show that, at least during the first stages of merging, the developing film is free from threading dislocations. The present findings, thus, introduce a promising path to integrate Ge layers on Si with a low dislocation density.

The brain is the most intricate, energetically active, and plastic organ in the body. These features extend to its cellular elements, the neurons and glia. Understanding neurons, or nerve cells, at the cellular and molecular levels is the cornerstone of modern neuroscience. The complexities of neuron structure and function require unusual methods of culture to determine how aberrations in or between cells give rise to brain dysfunction and disease. Here we review the methods that have emerged over the past century for culturing neurons in vitro, from the landmark finding by Harrison (1910) - that neurons can be cultured outside the body - to studies utilizing culture vessels, micro-islands, Campenot and brain slice chambers, and microfluidic technologies. We conclude with future prospects for neuronal culture and considerations for advancement. We anticipate that continued innovation in culture methods will enhance design capabilities for temporal control of media and reagents (chemotemporal control) within sub-cellular environments of three-dimensional fluidic spaces (microfluidic devices) and materials (e.g., hydrogels). They will enable new insights into the complexities of neuronal development and pathology.