Showing papers on "Fabrication published in 2017"

Water-based and biocompatible 2D crystal inks for all-inkjet-printed heterostructures

Abstract: Exploiting the properties of two-dimensional crystals requires a mass production method able to produce heterostructures of arbitrary complexity on any substrate. Solution processing of graphene allows simple and low-cost techniques such as inkjet printing to be used for device fabrication. However, the available printable formulations are still far from ideal as they are either based on toxic solvents, have low concentration, or require time-consuming and expensive processing. In addition, none is suitable for thin-film heterostructure fabrication due to the re-mixing of different two-dimensional crystals leading to uncontrolled interfaces and poor device performance. Here, we show a general approach to achieve inkjet-printable, water-based, two-dimensional crystal formulations, which also provide optimal film formation for multi-stack fabrication. We show examples of all-inkjet-printed heterostructures, such as large-area arrays of photosensors on plastic and paper and programmable logic memory devices. Finally, in vitro dose-escalation cytotoxicity assays confirm the biocompatibility of the inks, extending their possible use to biomedical applications. Device fabrication can be realized via inkjet printing of water-based 2D crystals.

All-dielectric nanophotonics: the quest for better materials and fabrication techniques

Abstract: All-dielectric nanophotonics is an exciting and rapidly developing area of nano-optics that utilizes the resonant behavior of high-index low-loss dielectric nanoparticles to enhance light–matter interaction at the nanoscale. When experimental implementation of a specific all-dielectric nanostructure is desired, two crucial factors have to be considered: the choice of a high-index material and a fabrication method. The degree to which various effects can be enhanced relies on the dielectric response of the chosen material as well as the fabrication accuracy. Here, we provide an overview of available high-index materials and existing fabrication techniques for the realization of all-dielectric nanostructures. We compare performance of the chosen materials in the visible and IR spectral ranges in terms of scattering efficiencies and Q factors of the magnetic Mie resonance. Methods for all-dielectric nanostructure fabrication are discussed and their advantages and disadvantages are highlighted. We also present an outlook for the search for better materials with higher refractive indices and novel fabrication methods that will enable low-cost manufacturing of optically resonant high-index nanoparticles. We believe that this information will be valuable across the field of nanophotonics and particularly for the design of resonant all-dielectric nanostructures.

Is the energy density a reliable parameter for materials synthesis by selective laser melting

Abstract: The effective fabrication of materials using selective laser melting depends on the process parameters. Here, we analyse the suitability of the energy density to represent the energy transferred to...

One-step volumetric additive manufacturing of complex polymer structures

Abstract: Two limitations of additive manufacturing methods that arise from layer-based fabrication are slow speed and geometric constraints (which include poor surface quality). Both limitations are overcome in the work reported here, introducing a new volumetric additive fabrication paradigm that produces photopolymer structures with complex nonperiodic three-dimensional geometries on a time scale of seconds. We implement this approach using holographic patterning of light fields, demonstrate the fabrication of a variety of structures, and study the properties of the light patterns and photosensitive resins required for this fabrication approach. The results indicate that low-absorbing resins containing ~0.1% photoinitiator, illuminated at modest powers (~10 to 100 mW), may be successfully used to build full structures in ~1 to 10 s.

Room-Temperature Fabricated Amorphous Ga2O3 High-Response-Speed Solar-Blind Photodetector on Rigid and Flexible Substrates

Abstract: A solution to the fabrication of amorphous Ga2O3 solar-blind photodetectors on rigid and flexible substrates at room temperature is reported. A robust improvement in the response speed is achieved by delicately controlling the oxygen flux in the reactive radio frequency magnetron sputtering process. Temporal response measurements show that the detector on quartz has a fast decay time of 19.1 µs and a responsivity of 0.19 A W−1 as well, which are even better than those single crystal Ga2O3 counterparts prepared at high temperatures. X-ray photoelectron spectroscopy and current–voltage tests suggest that the reduced oxygen vacancy concentration and the increased Schottky barrier height jointly contribute to the faster response speed. Amorphous Ga2O3 solar-blind photodetector is further constructed on polyethylene naphthalate substrate. The flexible devices demonstrate similar photoresponse behavior as the rigid ones, and no significant degradation of the device performance is observed in bending states and fatigue tests. The results reveal the importance of finely tuned oxygen processing gas in promoting the device performance and the applicability of room-temperature synthesized amorphous Ga2O3 in fabrication of flexible solar-blind photodetectors.

All-dielectric nanophotonics: the quest for better materials and fabrication techniques

Abstract: All-dielectric nanophotonics is an exciting and rapidly developing area of nanooptics which utilizes the resonant behavior of high-index low-loss dielectric nanoparticles for enhancing light-matter interaction on the nanoscale. When experimental implementation of a specific all-dielectric nanostructure is an issue, two crucial factors have to be in focus: the choice of a high-index material and a fabrication method. The degree to which various effects can be enhanced relies on the dielectric response of the chosen material as well as the fabrication accuracy. Here, we make an overview of available high-index materials and existing fabrication techniques for the realization of all-dielectric nanostructures. We compare performance of the chosen materials in the visible and IR spectral ranges in terms of scattering efficiencies and Q-factors. Various fabrication methods of all-dielectric nanostructures are further discussed, and their advantages and disadvantages are highlighted. We also present an outlook for the search of better materials with higher refractive indices and novel fabrication methods enabling low-cost manufacturing of optically resonant high-index nanoparticles. We hope that our results will be valuable for researches across the whole field of nanophotonics and particularly for the design of all-dielectric nanostructures.

Group‐III Sesquioxides: Growth, Physical Properties and Devices

Abstract: The group-III sesquioxides possess material properties that render them interesting for applications such as high-power rectifiers and transistors, solar-blind UV detectors and inter-sub-band infrared detectors. Technology for growing large, single-crystalline bulk material and for wafer fabrication exists, enabling homoepitaxial growth of thin films with high crystalline quality. The bandgap can be tuned in an energy range from about 4 to 8 eV for the ternary alloys and allows growth of heterostructures with large band offset. Here, past results and recent investigations on the growth, the material properties, contact fabrication and the alloying of group-III sesquioxides are reviewed, and an overview on demonstrator devices is provided.

On the Anisotropic Mechanical Properties of Selective Laser-Melted Stainless Steel.

Abstract: The thorough description of the peculiarities of additively manufactured (AM) structures represents a current challenge for aspiring freeform fabrication methods, such as selective laser melting (SLM). These methods have an immense advantage in the fast fabrication (no special tooling or moulds required) of components, geometrical flexibility in their design, and efficiency when only small quantities are required. However, designs demand precise knowledge of the material properties, which in the case of additively manufactured structures are anisotropic and, under certain circumstances, inhomogeneous in nature. Furthermore, these characteristics are highly dependent on the fabrication settings. In this study, the anisotropic tensile properties of selective laser-melted stainless steel (1.4404, 316L) are investigated: the Young’s modulus ranged from 148 to 227 GPa, the ultimate tensile strength from 512 to 699 MPa, and the breaking elongation ranged, respectively, from 12% to 43%. The results were compared to related studies in order to classify the influence of the fabrication settings. Furthermore, the influence of the chosen raw material was addressed by comparing deviations on the directional dependencies reasoned from differing microstructural developments during manufacture. Stainless steel was found to possess its maximum strength at a 45° layer versus loading offset, which is precisely where AlSi10Mg was previously reported to be at its weakest.

Screen-printing inks for the fabrication of solid oxide fuel cell films: A review

Abstract: Fabrication of solid oxide fuel cell (SOFC) components via a simple and economical technique is critical to lower the overall manufacturing cost of SOFCs. Thus, screen-printing is widely used to fabricate SOFC components having thickness in the range of 10–100 µm. Fabrication of optimized screen-printing inks is highly significant for the production of high quality films with improved performance. The effect of solid, binder, solvent and dispersant on the ink rheological properties and performance of resultant films must be deeply understood for the fabrication of optimized screen-printing inks. These effects can be optimized by measuring the rheological properties of inks such as viscosity, yield stress, thixotropy and viscoelasticity for application at a specific printer setting. Understanding the relationship between the composition and rheology of the inks may enhance the properties and performance of the resultant screen-printed films. Furthermore, these parameters can be correlated to the film properties such as mechanical strength, electrical conductivity and electrochemical properties of the resultant films. The focus of this review paper is to understand the underpinning science of ink rheology and processing conditions of screen-printing inks for the fabrication of high performance SOFC electrodes and/or electrolyte.

Inkjet-Printing: A New Fabrication Technology for Organic Transistors

Abstract: Inkjet-printing is one of the most important fabrication techniques in the field of printed electronics. Its main advantages include the possibility of fabricating, at ambient conditions and by employing a digital layout, a large variety of electronic devices on different types of substrates, including flexible plastic ones. In this paper, the utilization of inkjet-printing as an important fabrication tool for the realization of organic transistors and circuits/sensing systems based on such type of transistors is reviewed. The most important aspects of the fabrication process, including ink formulation, printing deposition, and postprinting treatment, are described in detail. The most significant examples of inkjet-printed organic transistors of different types (field-effect, electrolyte-gated, and electrochemical) are presented and finally an overview of their applications as building blocks of more complex electronic circuits and systems for the detection and quantification of specific measurands is provided.

Design and Fabrication of a Precious Metal-Free Tandem Core–Shell p+n Si/W-Doped BiVO4 Photoanode for Unassisted Water Splitting

Abstract: Tandem photoelectrochemical water splitting cells utilizing crystalline Si and metal oxide photoabsorbers are promising for low-cost solar hydrogen production. This study presents a device design and a scalable fabrication scheme for a tandem heterostructure photoanode: p+n black silicon (Si)/SnO2 interface/W-doped bismuth vanadate (BiVO4)/cobalt phosphate (CoPi) catalyst. The black-Si not only provides a substantial photovoltage of 550 mV, but it also serves as a conductive scaffold to decrease charge transport pathlengths within the W-doped BiVO4 shell. When coupled with cobalt phosphide (CoP) nanoparticles as hydrogen evolution catalysts, the device demonstrates spontaneous water splitting without employing any precious metals, achieving an average solar-to-hydrogen efficiency of 0.45% over the course of an hour at pH 7. This fabrication scheme offers the modularity to optimize individual cell components, e.g., Si nanowire dimensions and metal oxide film thickness, involving steps that are compatible with fabricating monolithic devices. This design is general in nature and can be readily adapted to novel, higher performance semiconducting materials beyond BiVO4 as they become available, which will accelerate the process of device realization.

Highly Crystalline C8-BTBT Thin-Film Transistors by Lateral Homo-Epitaxial Growth on Printed Templates.

Abstract: Highly crystalline thin films of organic semiconductors offer great potential for fundamental material studies as well as for realizing high-performance, low-cost flexible electronics. The fabrication of these films directly on inert substrates is typically done by meniscus-guided coating techniques. The resulting layers show morphological defects that hinder charge transport and induce large device-to-device variability. Here, a double-step method for organic semiconductor layers combining a solution-processed templating layer and a lateral homo-epitaxial growth by a thermal evaporation step is reported. The epitaxial regrowth repairs most of the morphological defects inherent to meniscus-guided coatings. The resulting film is highly crystalline and features a mobility increased by a factor of three and a relative spread in device characteristics improved by almost half an order of magnitude. This method is easily adaptable to other coating techniques and offers a route toward the fabrication of high-performance, large-area electronics based on highly crystalline thin films of organic semiconductors.

Dry-etching-assisted femtosecond laser machining

Abstract: Femtosecond laser machining has been widely used for fabricating arbitrary 2.5 dimensional (2.5D) structures. However, it suffers from the problems of low fabrication efficiency and high surface roughness when processing hard materials. To solve these problems, we propose a dry-etching-assisted femtosecond laser machining (DE-FsLM) approach in this paper. The fabrication efficiency could be significantly improved for the formation of complicated 2.5D structures, as the power required for the laser modification of materials is lower than that required for laser ablation. Furthermore, the surface roughness defined by the root-mean-square improved by an order of magnitude because of the flat interfaces of laser-modified regions and untreated areas as well as accurate control during the dry-etching process. As the dry-etching system is compatible with the IC fabrication process, the DE-FsLM technology shows great potential for application in the device integration processing industry.

Fabrication of Composite Filaments with High Dielectric Permittivity for Fused Deposition 3D Printing.

Abstract: Additive manufacturing of complex structures with spatially varying electromagnetic properties can enable new applications in high-technology sectors such as communications and sensors. This work presents the fabrication method as well as microstructural and dielectric characterization of bespoke composite filaments for fused deposition modeling (FDM) 3D printing of microwave devices with a high relative dielectric permittivity ϵ = 11 in the GHz frequency range. The filament is composed of 32 vol % of ferroelectric barium titanate (BaTiO 3 ) micro-particles in a polymeric acrylonitrile butadiene styrene (ABS) matrix. An ionic organic ester surfactant was added during formulation to enhance the compatibility between the polymer and the BaTiO 3 . To promote reproducible and robust printability of the fabricated filament, and to promote plasticity, dibutyl phthalate was additionally used. The combined effect of 1 wt % surfactant and 5 wt % plasticizer resulted in a uniform, many hundreds of meters, continuous filament of commercial quality capable of many hours of uninterrupted 3D printing. We demonstrate the feasibility of using the high dielectric constant filament for 3D printing through the fabrication of a range of optical devices. The approach herein may be used as a guide for the successful fabrication of many types of composite filament with varying functions for a broad range of applications.

3D-Printed Conical Arrays of TiO2 Electrodes for Enhanced Photoelectrochemical Water Splitting

Abstract: Control over the topography of semiconducting materials can lead to enhanced performances in photoelectrochemical related applications. One means of implementing this is through direct patterning of metal-based substrates, though this is inadequately developed. Conventional techniques for patterned fabrication commonly involve technologically demanding and tedious processes. 3D printing, a form of additive fabrication, enables creation of a 3D object by deposition of successive layers of material via computer control. In this work, the feasibility of fabricating metal-based 3D printed photoelectrodes is explored. Electrodes comprised of conical arrays are fabricated and the performance for photoelectrochemical water splitting is further enhanced by the direct growth of TiO2 nanotubes on this platform. 3D metal printing provides a flexible and versatile approach for the design and fabrication of novel electrode structures.

High-energy, flexible micro-supercapacitors by one-step laser fabrication of a self-generated nanoporous metal/oxide electrode

Abstract: A high-performance and flexible micro-supercapacitor based on a self-generated nanoporous silver layer was fabricated by a one-step laser-induced growth-sintering process of a particle-free organometallic solution. The porous structures self-generated on a polymer film and were freely adjustable by controlling the rate of laser input dose. By changing the patterning mode, the nanoporous electrodes with extremely high surface area and highly conductive current collectors were formed in a single processing domain. Electrodeposition of hetero metal oxides (manganese and iron oxides) as the active materials followed, and a flexible micro-supercapacitor with high volumetric energy density of 16.3 mW h cm−3 and power density of 3.54 W cm−3 was formed. This was achieved through the large surface area and high electrical conductivity of the nanoporous silver layer, and high operating voltage due to the asymmetrical electrode configuration. This method resulted in a faster and more cost-effective manufacturing process than conventional MSCs fabrication. It also achieved the highest volumetric energy density in metal/oxide-based MSCs as a state-of-the-art performance.

Aerosol-Jet-Assisted Thin-Film Growth of CH3NH3PbI3 Perovskites—A Means to Achieve High Quality, Defect-Free Films for Efficient Solar Cells

Abstract: A high level of automation is desirable to facilitate the lab-to-fab process transfer of the emerging perovskite-based solar technology. Here, an automated aerosol-jet printing technique is introduced for precisely controlling the thin-film perovskite growth in a planar heterojunction p–i–n solar cell device structure. The roles of some of the user defined parameters from a computer-aided design file are studied for the reproducible fabrication of pure CH3NH3PbI3 thin films under near ambient conditions. Preliminary power conversion efficiencies up to 15.4% are achieved when such films are incorporated in a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-perovskite-phenyl-C71-butyric acid methyl ester type device format. It is further shown that the deposition of atomized materials in the form of a gaseous mist helps to form a highly uniform and PbI2 residue-free CH3NH3PbI3 film and offers advantages over the conventional two-step solution approach by avoiding the detrimental solid–liquid interface induced perovskite crystallization. Ultimately, by integrating full 3D motion control, the fabrication of perovskite layers directly on a 3D curved surface becomes possible. This work suggests that 3D automation with aerosol-jet printing, once fully optimized, could form a universal platform for the lab-to-fab process transfer of solution-based perovskite photovoltaics and steer development of new design strategies for numerous embedded structural power applications.

Continuous lattice fabrication of ultra-lightweight composite structures

Abstract: This paper introduces continuous lattice fabrication (CLF) – a novel additive manufacturing (AM) technique invented for fiber-reinforced thermoplastic composites – and demonstrates its ability to exploit anisotropic material properties in digitally fabricated structures. In contrast to the layer-by-layer approaches employed in most AM processes, CLF enables the directed orientation of the fibers in all spatial coordinates, that is in the x- , y- , and z- directions. Based on a serial pultrusion and extrusion approach, CLF consolidates commingled yarns in situ and allows for the continuous deposition of high fiber volume fraction (>50%) materials along a programmable trajectory without the use of molds or sacrificial layers by exploiting the high viscosities of fiber-filled polymer melts. The capacity of CLF to produce high-performance structural components is demonstrated in the fabrication of an ultra-lightweight load-bearing lattice structure with outstanding stiffness-to-density and strength-to-density performance (compression modulus of 13.23 MPa and compressive strength of 0.20 MPa at a core density of 9 mg/cm 3 ). This digital fabrication method enables new approaches in load-tailored design, including the possibility to build freeform structures, which have previously been overlooked due to difficulties and limitations in modern fiber composite manufacturing capabilities.

Fabrication of Copper-Rich Cu-Al Alloy Using the Wire-Arc Additive Manufacturing Process

Abstract: An innovative wire-arc additive manufacturing (WAAM) process is used to fabricate Cu-9 at. pct Al on pure copper plates in situ, through separate feeding of pure Cu and Al wires into a molten pool, which is generated by the gas tungsten arc welding (GTAW) process. After overcoming several processing problems, such as opening the deposition molten pool on the extremely high-thermal conductive copper plate and conducting the Al wire into the molten pool with low feed speed, the copper-rich Cu-Al alloy was successfully produced with constant predesigned Al content above the dilution-affected area. Also, in order to homogenize the as-fabricated material and improve the mechanical properties, two further homogenization heat treatments at 1073 K (800 °C) and 1173 K (900 °C) were applied. The material and mechanical properties of as-fabricated and heat-treated samples were compared and analyzed in detail. With increased annealing temperatures, the content of precipitate phases decreased and the samples showed gradual improvements in both strength and ductility with little variation in microstructures. The present research opened a gate for in-situ fabrication of Cu-Al alloy with target chemical composition and full density using the additive manufacturing process.

Large‐Area, All‐Solid, and Flexible Electric Double Layer Capacitors Based on CNT Fiber Electrodes and Polymer Electrolytes

Abstract: This work presents a scalable method to produce robust all-solid electric double layer capacitors (EDLCs), compatible with roll-to-roll processes and structural laminate composite fabrication. It consists in sandwiching and pressing an ionic liquid-based polymer electrolyte membrane between two carbon nanotube (CNT) fiber sheet electrodes at room temperature, and laminating with ordinary plastic film. This fabrication method is demonstrated by assembling large-area devices of up to 100 cm2 with electrodes fabricated in-house, as well as with commercial CNT fiber sheets. Freestanding flexible devices operating at 3.5 V exhibit 28 F g−1 of specific capacitance, 11.4 W h kg−1 of energy density, and 46 kW kg−1 of power density. These values are nearly identical to control samples with pure ionic liquid. The solid EDLCs could be repeatedly bent and folded 180° without degradation of their properties, with a reversible 25% increase in energy density in the bent state. Devices produced using CNT fiber electrodes with a higher degree of orientation and therefore better mechanical properties show similar electrochemical properties combined with composite specific strength and modulus of 39 and 577 MPa SG−1 for a fiber mass fraction of 11 wt%, similar to a structural thermoplastic and with higher specific strength than copper.

Multiscale Simulation Platform Linking Lithium Ion Battery Electrode Fabrication Process with Performance at the Cell Level.

Abstract: A novel multiscale modeling platform is proposed to demonstrate the importance of particle assembly during battery electrode fabrication by showing its effect on battery performance. For the first time, a discretized three-dimensional (3D) electrode resulting from the simulation of its fabrication has been incorporated within a 3D continuum performance model. The study used LiNi0.5Co0.2Mn0.3O2 as active material, and the effect of changes of electrode formulation is explored for three cases, namely 85:15, 90:10, and 95:5 ratios between active material and carbon–binder domains. Coarse-grained molecular dynamics is used to simulate the electrode fabrication. The resulting electrode mesostructure is characterized in terms of active material surface coverage by the carbon–binder domains and porosity. The trends observed are nonintuitive, indicating a high degree of complexity of the system. These structures are subsequently implemented into a 3D continuum model which displays distinct discharge behaviors for...

Three-Dimensional Solid-State Lithium-Ion Batteries Fabricated Via Conformal Vapor-Phase Chemistry

Abstract: Thin film solid state lithium-based batteries (TSSBs) are increasingly attractive for their intrinsic safety due to the use of a nonflammable solid electrolyte, cycling stability, and ability to be easily patterned in small form factors. However, existing methods for fabricating TSSBs are limited to planar geometries, which severely limits areal energy density when the electrodes are kept sufficiently thin to achieve high areal power. In order to circumvent this limitation, we report the first successful fabrication of fully conformal, 3D full cell TSSBs formed in micromachined silicon substrates with aspect ratios up to ~10 using atomic layer deposition (ALD) at low processing temperatures (at or below 250C) to deposit all active battery components. The cells utilize a prelithiated LiV$_2$O$_5$ cathode, a very thin (40 - 100 nm) LiPON-like lithium polyphosphazene (Li$_2$PO$_2$N) solid electrolyte, and a SnN$_x$ conversion anode, along with Ru and TiN current collectors. Planar all-ALD solid state cells deliver 37 {\mu}Ah/cm$^2${\mu}m normalized to the cathode thickness with only 0.02% per-cycle capacity loss for hundreds of cycles. Fabrication of full cells in 3D substrates increases the areal discharge capacity by up to a factor of 9.3x while simultaneously improving the rate performance, which corresponds well to trends identified by finite element simulations of the cathode film. This work shows that the exceptional conformality of ALD, combined with conventional semiconductor fabrication methods, provides an avenue for the successful realization of long-sought 3D TSSBs which provide power performance scaling in regimes inaccessible to planar form factor devices.

Piezoelectric component fabrication using projection-based stereolithography of barium titanate ceramic suspensions

Abstract: Purpose Conventional machining methods for fabricating piezoelectric components such as ultrasound transducer arrays are time-consuming and limited to relatively simple geometries. The purpose of this paper is to develop an additive manufacturing process based on the projection-based stereolithography process for the fabrication of functional piezoelectric devices including ultrasound transducers. Design/methodology/approach To overcome the challenges in fabricating viscous and low-photosensitive piezocomposite slurry, the authors developed a projection-based stereolithography process by integrating slurry tape-casting and a sliding motion design. Both green-part fabrication and post-processing processes were studied. A prototype system based on the new manufacturing process was developed for the fabrication of green-parts with complex shapes and small features. The challenges in the sintering process to achieve desired functionality were also discussed. Findings The presented additive manufacturing process can achieve relatively dense piezoelectric components (approximately 95 per cent). The related property testing results, including X-ray diffraction, scanning electron microscope, dielectric and ferroelectric properties as well as pulse-echo testing, show that the fabricated piezo-components have good potentials to be used in ultrasound transducers and other sensors/actuators. Originality/value A novel bottom-up projection system integrated with tape casting is presented to address the challenges in the piezo-composite fabrication, including small curing depth and viscous ceramic slurry recoating. Compared with other additive manufacturing processes, this method can achieve a thin recoating layer (as small as 10 μm) of piezo-composite slurry and can fabricate green parts using slurries with significantly higher solid loadings. After post processing, the fabricated piezoelectric components become dense and functional.

Efficient fabrication methodology of wide angle black silicon for energy harvesting applications

Abstract: In this paper, we report an easy and relatively cost effective fabrication technique of a wide band omnidirectional antireflective black silicon surface based on silicon nanowires (SiNWs). An effective and economical one step silver electroless catalytic etching method in an aqueous solution of AgNO3 and HF is used for the synthesis of the black silicon surface. The formation mechanism for SiNW arrays is explained in terms of a localized nanoelectrochemical cell. The length and diameter of the nanowires were controllable as we found a commensurate relationship between dimensions and the etching time. Different sample sizes were used to prove the technique's large scale production potential. Wide range near zero reflection is reported in the visible region due to the strong trapping and antireflective properties in addition to a wide angle up to ±60°. Raman scattering measurements confirmed the quantum size effect and phonon scattering in the fabricated structure with different diameters. A black silicon surface based on solid and porous SiNWs shows promising potential for photovoltaic, optoelectronic and energy storage applications.