Wafer Substrates Research Articles

Experiment and analysis of the effect of BCB sealing ring flatness on BCB cap transfer packaging

This paper presents the effect of BCB sealing ring flatness on BCB bonding for wafer-scale BCB cap transfer packaging. BCB sealing ring has shown partial bonding or full bonding depending on its flatness. It is found that the principal cause of the partial bonding is due to non-flat BCB sealing ring caused by multilayer BCB coating process. As a solution, BCB dry etching has been proposed to improve the flatness of the BCB sealing ring for full BCB bonding. Besides, partial bonding of BCB ring has been analyzed through FEM modeling of BCB cap with a non-flat sealing ring. The FEM model consists of Si carrier wafer, BCB cap, and Si target substrate. Unique load is applying pressure on top of Si carrier wafer like wafer-scale bonding. The role of applying pressure is to get BCB sealing ring to be contacted and expand bondable area with target Si substrate. As BCB sealing ring is bonded through BCB polymerization by holding the pressure for 1 h at 250 °C, mechanical properties of virgin BCB sealing ring has been changed during bonding. Thus, it has been chosen as variable for parametric analysis. Also, BCB cap dimension has been used as another parameter for the parametric analysis.

High Temperature Oxidation Behavior of Cr-Al-Si-N Nanocomposite Films Deposited by Filtered Arc Ion Plating Technique.

High temperature oxidation behavior of nanocomposite films is very important characteristics for application of machining and cutting tools. Quaternary Cr-Al-Si-N nanocomposite films with various compositions were deposited onto WC-Co and Si wafer substrates using a filtered arc ion plating technique. The composition of the films were controlled by different combinations of CrAl₂ and Cr₄Si composite target power in a reactive gas mixture of high purity Ar and N₂ during depositions. The instrumental analyses revealed that the synthesized Cr-Al-Si-N films with Si content of 2.78 at.% were nanocomposites consisting of nano-sized crystallites (3-7 nm in dia.) and a thin layer of amorphous Si₃N₄ phases. The nanohardness of the Cr-Al-Si-N films exhibited the maximum values of ~42 GPa at a Si content of ~2.78 at.% due to the microstructural change to nanocomposite as well as solid-solution hardening. The Cr-Al-Si-N film shows superior result of oxidation resistance at 1050 °C for 30 min in air. Based on the XRD and GDOES analyses on the oxidized films, it could be revealed that the enrichment of Al (17.94 at.%) and Cr (26.24 at.%) elements in the film leads to form an Al₂O₃ and Cr₂O₃ layer on the Cr-Al-Si-N film surface. Therefore, in this study, the microstructural changes on the mechanical properties and oxidation behavior with various compositions in the Cr-Al-Si-N nanocomposite films were discussed and correlated with the deposition parameters.

A new test specimen for the determination of the field of view of small‐area X‐ray photoelectron spectrometers

Small‐area/spot photoelectron spectroscopy (SAXPS) is a powerful tool for the investigation of small surface features like microstructures of electronic devices, sensors or other functional surfaces, and so forth. For evaluating the quality of such microstructures, it is often crucial to know whether a small signal in a spectrum is an unwanted contamination of the field of view (FoV), defined by the instrument settings, or it originated from outside. To address this issue, the d80/20 parameter of a line scan across a chemical edge is often used. However, the typical d80/20 parameter does not give information on contributions from the long tails of the X‐ray beam intensity distribution or the electron‐optical system as defined by apertures. In the VAMAS TWA2 A22 project “Applying planar, patterned, multi‐metallic samples to assess the impact of analysis area in surface‐chemical analysis,” new test specimen was developed and tested. The here presented testing material consists of a silicon wafer substrate with an Au‐film and embedded Cr circular and square spots with decreasing dimensions from 200 μm down to 5 μm. The spot sizes are traceable to the length unit due to size measurements with a metrological SEM. For the evaluation of the FoV, we determined the Au4f intensities measured with the center of the FoV aligned with the center of the spot and normalized to the Au4f intensity determined on the Au‐film. With this test specimen, it was possible to characterize, as an example, the FoV of a Kratos AXIS Ultra DLD XPS instrument.

HARDNESS OF HYBRID PVD-PECVD W-C:H COATINGS VS. SUBSTRATE TYPE

The effects of substrate on the measurement of hardness (and indentation modulus) - penetration depth profiles were investigated on hybrid PVD-PECVD W-C:H coatings made with the additions of C2H2 or CH4 using High Power Impulse Magnetron Sputtering (HiPIMS) method. The substrates involved 100Cr6 bearing steel, Al2024 aluminum alloy and (111) Si wafer. Although no clear influence of the substrate type on hardness and indentation modulus of the coatings at different acetylene and hydrogen additions was observed, when both measured properties were combined in HITEIT ratio, significant shift of HIT/EIT ratio dependencies obtained on Al alloy vs. steel and Si wafer substrates occurred. Thus, the effect of substrate type on the measurementlevaluation was confirmed.

Effects of lattice mismatches in In2O3/substrate structures on the structural, morphological and electrical properties of In2O3 films

Indium oxide thin films were deposited by ultrasonic spray technique on ITO coated glass and single crystalline Si (400) substrates at 400 °C. Lattice mismatch effect on the crystalline structure, surface morphology and electrical properties of these samples is then studied. X-ray diffraction (XRD) and Raman spectroscopy patterns suggest that the films deposited on ITO coated glass substrate are polycrystalline in nature having a cubic crystal structure with a preferred grain orientation along the (222) plane. However, films deposited on Si wafer substrate, exhibit randomly oriented growth. The crystallite size varies from 18 to 66.5 nm. AFM topographical images revealed that the In2O3/ITO films follow 2D or layer-by-layer-growth. But in the case of In2O3/Si films, 3D or island growth becomes dominant. The In2O3/ITO films is found to exhibit a higher value of conductivity (σ = 5 × 102 Ω−1 cm−1) than the In2O3/Si films, and the low value of the RMS roughness (9.83 nm).

Dynamic Absorption Enhancement and Equivalent Resonant Circuit Modeling of Tunable Graphene-Metal Hybrid Antenna.

Plasmonic antennas are attractive optical components of the optoelectronic devices, operating in the far-infrared regime for sensing and imaging applications. However, low optical absorption hinders its potential applications, and their performance is limited due to fixed resonance frequency. In this article, a novel gate tunable graphene-metal hybrid plasmonic antenna with stacking configuration is proposed and investigated to achieve tunable performance over a broad range of frequencies with enhanced absorption characteristics. The hybrid graphene-metal antenna geometry is built up with a hexagon radiator that is supported by the Al2O3 insulator layer and graphene reflector. This stacked structure is deposited in the high resistive Si wafer substrate, and the hexagon radiator itself is a sandwich structure, which is composed of gold hexagon structure and two multilayer graphene stacks. The proposed antenna characteristics i.e., tunability of frequency, the efficiency corresponding to characteristics modes, and the tuning of absorption spectra, are evaluated by full-wave numerical simulations. Besides, the unity absorption peak that was realized through the proposed geometry is sensitive to the incident angle of TM-polarized incidence waves, which can flexibly shift the maxima of the absorption peak from 30 THz to 34 THz. Finally, an equivalent resonant circuit model for the investigated antenna based on the simulations results is designed to validate the antenna performance. Parametric analysis of the proposed antenna is carried out through altering the geometric parameters and graphene parameters in the Computer Simulation Technology (CST) studio. This clearly shows that the proposed antenna has a resonance frequency at 33 THz when the graphene sheet Fermi energy is increased to 0.3 eV by applying electrostatic gate voltage. The good agreement of the simulation and equivalent circuit model results makes the graphene-metal antenna suitable for the realization of far-infrared sensing and imaging device containing graphene antenna with enhanced performance.

Material and Si-based diode analyses of sputtered ZnTe thin films

Structural, optical, and electrical properties ZnTe thin films grown by magnetron sputtering technique were studied by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and electrical conductivity measurements. Structural analyses showed that ZnTe thin films grown on soda–lime glass substrates have a cubic crystalline structure. This crystalline nature of the films was also discussed in terms of Raman active modes. From atomic force microscopy images, the smooth and dense surface profile was observed. The conductivity of the film at room temperature was measured as 2.45 × 10−4 (Ω cm)−1 and the temperature dependency of conductivity showed Arrhenius behavior. The dark conductivity profile was modeled by thermionic emission mechanism and activation energies were extracted. In addition, the conductivity values indicated an increasing behavior with illumination intensity applied between 20 and 115 mW/cm2. The heterojunction diode was generated by sputtering ZnTe film on n-Si wafer substrate and the rectification behavior was evaluated to determine the main diode parameters.

Unprecedentedly Low CO2 Transport through Vertically Aligned, Conical Silicon Nanotube Membranes.

Nanotube membranes could show significantly enhanced permeance and selectivity for gas separations. Up until now, studies have primarily focused on applying carbon nanotubes to membranes to achieve ultrafast mass transport. Here, we report the first preparation of silicon nanotube (SiNT) membranes via a template-assisted method and investigate the gas transport behavior through these SiNT membranes using single- and mixed-gas permeation experiments. The SiNT membranes consist of conical cylinder-shaped nanotubes vertically aligned on a porous silicon wafer substrate. The diameter of the SiNT pore mouths are 10 and 30 nm, and the average inner diameter of the tube body is 80 nm. Interestingly, among the gases tested, we found an unprecedentedly low CO2 permeance through the SiNT membranes in single-gas permeation experiments, exceeding the theoretical Knudsen selectivity toward small gases/CO2 separation. This behavior was caused by the reduction of CO2 permeability through the blocking effect of CO2 adsorbed in the narrow pore channels of the SiNT cone regions, indicating that CO2 molecules have a high affinity to the native silicon oxide layer (∼2 nm) that is formed on the inner walls of SiNTs. SiNT membranes also exhibited enhanced gas permeance and water flux as compared to classic theoretical models and, as such, may prove useful as a new type of nanotube material for use in membrane applications.

Droplet spreading nanoimprinting method for micro-/nano-fabrication

This paper proposes an innovative nanoimprinting method that features imprinting a single droplet of resist and spreading it from center to edge to fully cover a full wafer substrate. Important advantages of this type of nanoimprinting include avoiding air bubble trapping, forming conformal mold/substrate contact, minimizing residual layer thickness, and saving the amount of resist being used. It also makes the demolding process much easier and more successful. To realize this nanoimprinting method, an imprinting tool is designed, constructed, and experimentally tested, and three key components are developed. First of all, a soft mold is integrated into a dovetailed metal ring so that it can be fixed at its edge and deformed by external force. Secondly, two independent loading mechanism are installed so that a soft mold can be initially deformed to form a point contact with a substrate and then followed by imprinting process. Finally, an elastomer cushion pad with a pre-designed convex surface profile is used to convert the loading force into a specific distributed contact pressure which can drive the resist flow. Nanoimprinting experiments have been carried out for pattering micro-scaled and nano-scaled structures on 4″ glass wafers. Excellent imprinting results are observed. The potentials and future perspectives of the proposed nanoimprint system will be addressed.

Ultra-high resolution and broadband chip-scale speckle enhanced Fourier-transform spectrometer.

Recent advancements in silicon photonics are enabling the development of chip-scale photonics devices for sensing and signal processing applications, among which on-chip spectrometers are of particular interest for precision wavelength monitoring and related applications. Most chip-scale spectrometers suffer from a resolution-bandwidth trade-off, thus limiting the uses of the device. Here we report on a novel passive, chip-scale, hybrid speckle-enhanced Fourier transform device that exhibits a two order-of-magnitude improvement in finesse (bandwidth/resolution) over the state-of-the art chip-scale speckle and Fourier transform spectrometers. In our proof-of-principle device, we demonstrate a spectral resolution of 140 MHz with 12-nm bandwidth for a finesse of 104 that can operate over a range of 1500-1600 nm. This chip-scale spectrometer structure implements a typical spatial heterodyne discrete Fourier transform interferometer network that is enhanced by speckle generated from the wafer substrate. This latter effect, which is extremely simple to invoke, superimposes the high wavelength resolution intrinsic to speckle generated from a strongly guiding waveguide with a more broadband but lower resolution discrete Fourier transform modality of the overarching waveguide structure. This hybrid approach signifies a new pathway for realizing chip-scale spectrometers capable of ultra-high resolution and broadband performance.

Surface-Grafted Hyperbranched Polyglycerol Coating: Varying Extents of Fouling Resistance across a Range of Proteins and Cells.

Hyperbranched polyglycerol (HPG) was previously investigated as a nonfouling hydrophilic grafted layer on biomaterial surfaces, analogous to the well-known poly(ethylene oxide) (PEO), but the range of adsorbing cells and proteins tested was limited and at times the assays used were not the most sensitive. Thus, the questions arise whether HPG-grafted layers can indeed efficiently resist adsorption of a wider range of adsorbing biological entities, and how would different biological entities interact with such a coating. An HPG coating of 25 nm thickness was grafted onto a spin-coated and plasma-treated polystyrene (PS) layer on a silicon wafer substrate; this provided a well-suited system for surface analyses by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM), which verified the presence of a uniform, smooth grafted HPG layer. Adsorption of bovine serum albumin, lysozyme, fibrinogen, and endothelial cell growth medium 2 (EGM2) was reduced by >90%, with the adsorbed amounts close to the detection limit of XPS but still detectable by ToF-SIMS using principal component analysis. With human serum, however, the reduction in adsorption was slightly less pronounced. Smooth muscle cells (SMCs) and fibroblasts were virtually unable to attach onto the grafted HPG layer, with >99% reductions at 6 h compared with plasma-treated PS; the few attached cells remaining rounded and unable to spread. Their attachment might have resulted from coating defects. Testing with full blood showed that unlike for the control surface (plasma-treated PS), platelets did not adhere to the HPG surface, but there was attachment of some cells that stained CD11b positive and likely are neutrophils. Cells of the fungal organism Candida albicans were also able to attach onto the HPG surface to a limited extent, but in contrast to the control surface, the attached cells on HPG did not form hyphal extensions and thus seem to be compromised in their ability to invade and to form biofilms. Our data suggest that "low-fouling" is a better term than nonfouling for a grafted HPG layer as the resistance to adsorption is not uniform across a range of proteins and cells. It is also important in future work to study whether the cells that do attach can still exert their normal functions; our observation of the absence of hyphal extensions for C. albicans suggests that this may not be so. Hence, the potential utility of a grafted HPG layer may be not just a function of adsorbed amounts but also of the functionality of adsorbed proteins and cells.

High-Throughput Stamping of Hybrid Functional Surfaces.

Hydrophobic-hydrophilic hybrid surfaces, sometimes termed biphilic surfaces, have shown potential to enhance condensation and boiling heat transfer, anti-icing, and fog harvesting performance. However, state of art techniques to develop these surfaces have limited substrate selection, poor scalability, and lengthy and costly fabrication methods. Here, we develop a simple, scalable, and rapid stamping technique for hybrid surfaces with spatially controlled wettability. To enable stamping, rationally designed and prefabricated polydimethylsiloxane (PDMS) stamps, which are reusable and independent of the substrate and functional coating, were used. To demonstrate the stamping technique, we used silicon wafer, copper, and aluminum substrates functionalized with a variety of hydrophobic chemistries including heptadecafluorodecyltrimethoxy-silane, octafluorocyclobutane, and slippery omniphobic covalently attached liquids. Condensation experiments and microgoniometric characterization demonstrated that the stamped surfaces have global hydrophobicity or superhydrophobicity with localized hydrophilicity (spots) enabled by local removal of the functional coating during stamping. Stamped surfaces with superhydrophobic backgrounds and hydrophilic spots demonstrated stable coalescence induced droplet jumping. Compared to conventional techniques, our stamping method has comparable prototyping cost with reduced manufacturing time scale and cost. Our work not only presents design guidelines for the development of scalable hybrid surfaces for the study of phase change phenomena, it develops a scalable and rapid stamping protocol for the cost-effective manufacture of next-generation hybrid wettability surfaces.

Transport Coefficients of Ammonia Gas in Thermoplastic Polymers and Nanocomposites Used for Microelectronic Substrates Containers

Polymeric plastic boxes (named Front Opening Unified Pods (FOUP)) were widely used in semiconductor manufacture to maintain the cleanliness of processed wafer substrates in a controlled mini-environment. Polymeric materials, however, are able to sorb airborne molecular contaminants (AMCs) and subsequently to outgas the sorbed AMCs backward to FOUP’s atmosphere, causing the transfer of AMCs to sensitive stored substrates, named cross-contamination. As a type of AMCs, the NH3 cross-contamination could cause a severe yield loss to integrated circuits (crystals (haze), resist-development defects (T-topping) or metallic corrosion). Experiments were carried out to establish the NH3 sorption and desorption kinetics in polyetherimide (PEI), Entegris Barrier Material (EBM)), and EBM/carbon nanotubes (EBMCNT) at NH3 concentration of 800-ppbv, 21°C, and relative humidity of 40%. The transport coefficients i.e. solubility and diffusivity (DNH3 and SNH3) were then determined. The study on NH3 provides an additional guideline to choose the best raw materials for FOUP formulation in taking into account the potential cross-contamination of AMCs. Numerical simulation model based on obtained solubility and diffusivity values was conducted to demonstrate NH3 concentration profiles in FOUP walls during contamination and FOUP decontamination, which are inaccessible by conventional experiments.

A high-performance near-infrared photodetector based on π-SnS phase

This study presents a novel high-performance, non-toxic and low-cost near-infrared (NIR) photodetector based on a new cubic crystal structure (π-SnS) grown onto silicon wafer substrate by cost-effective and simple chemical bath deposition. The photodetector exhibits excellent photoresponse characteristics under NIR (750 nm) light illumination; sensitivity (3768), detectivity 1.35x1010 Jones, rise time (0.18 s) and decay time (0.16 s) at −5 V bias voltage. Moreover, the photodetector shows excellent reproducibility and stability characteristics. The as-fabricated SnS photodetector is a promising optoelectronic device efficient over NIR range.

Single-Crystal Integrated Photoanodes Based on 4H-SiC Nanohole Arrays for Boosting Photoelectrochemical Water Splitting Activity.

Photoelectrochemical (PEC) splitting of water into H2 and O2 by direct use of sunlight is an ideal strategy for the production of clean and renewable energy, which fundamentally relies on the exploration of advanced photoanodes with high performance. In the present work, we report that single-crystal integrated photoanodes, that is, 4H-SiC nanohole arrays (active materials) and SiC wafer substrate (current collector), are established into a totally single-crystal configuration without interfaces, which was based on a two-step electrochemical etching process. The as-fabricated SiC photoanode showed a rather low onset potential of -0.016 V vs reversible hydrogen electrode (RHE) and a high photocurrent density of 3.20 mA/cm2 vs RHE 1.23 V, which were both superior to those of all reported SiC ones. Furthermore, such a rationally designed photoanode exhibited a fast photoresponse, wide photoresponse wavelength range, and long-term stability, representing its overall excellent PEC performance.

Nb-doped TiO2 coatings developed by high power impulse magnetron sputtering-chemical vapor deposition hybrid deposition process

Novel methods for the deposition of thin functional coatings, such as hybrid physical vapor deposition-chemical vapor deposition (CVD) technologies, have the potential to become an important means of overcoming the limitations of current processes, such as low deposition rates, associated with some sputtering processes, or limited material/precursor choices, associated with CVD processes. This work explores the potential of addressing these issues through the development of a hybrid system, which combines the latest magnetron sputtering technology, high power impulse magnetron sputtering (HiPIMS), with plasma enhanced chemical vapor deposition (PECVD) technology. This system seeks to overcome the limitations of each technique and provide a new, flexible deposition tool for functional films, such as transparent conductive oxides. In this system, the plasma generated by the magnetron provides a source of electrons to drive the CVD precursor decomposition and reaction chemistry in the PECVD process. Consequently, only one power supply is required. Thus, niobium-doped titania coatings were deposited on glass and Si wafer substrates by this hybrid HiPIMS-CVD technique. The TiO2 coatings were deposited by CVD from a titanium (IV) tetraisopropoxide precursor via the vapor drawn method. The HiPIMS process provided not only the source of the Nb metal dopant to the functional films but also sustained the low temperature CVD process by supplying energetic plasma particles. Furthermore, since HiPIMS deposition rates are very sensitive to magnetic field strength and the degree of unbalance, by using a magnetron with variable magnetic field strength, it was possible to adjust the dopant content of the film without adjusting the power applied to the magnetron target. The effect of processing parameters (pulse frequency, peak powers, precursor flow rates, operating pressure, etc.) on generating a stable HiPIMS discharge across the process envelope has been studied. The composition and microstructure of the deposited coatings have been investigated, in respect to variable process parameters, such as substrate temperature and operating pressure.

Estimation of the performance limits of a concentrator solar cell coupled with a micro heat sink based on a finite element simulation

Concentrated photovoltaic (CPV) technology makes use of cheap optical elements to amplify the irradiance and focus it on small-sized solar cells enabling the extraction of higher amounts of electricity. However, increasing the solar concentration raises the temperature of the PV cell which can deter its performance and can also cause its failure. To combat this issue both active and passive cooling mechanisms are utilized for different types of CPV systems. In this study, we determine the limits of passive cooling systems and establish when an active cooling system is needed based on the recommended operating temperature of the solar cell. We investigate the temperature characteristics of the solar cells bonded to three different substrate materials under different solar concentrations. Results showed that cell temperature is linearly dependent on the concentration ratio and ambient temperature independent of the substrate material. Further, the integration of a micro-finned heatsink results in higher heat dissipation by 25.32%, 23.13%, and 22.24% in comparison with a flat plate heatsink for Direct Bonded Copper (DBC), Insulated Metal Substrate (IMS), and Silicon Wafer (Si wafer) substrates respectively. The low thermal resistance of the IMS substrate compared to the DBC and the Si wafer substrates result in the best thermal performance in terms of maintaining the cell temperature < 80 °C and allowing a wider range of high concentration ratio.

Deposition of SiOx thin films using hexamethyldisiloxane in atmospheric pressure plasma enhanced chemical vapor deposition

The atmospheric pressure plasma enhanced chemical vapor deposition method was used to study the enhancement of the particle growth and thin layer deposition. For this purpose, an atmospheric pressure plasma jet was used to deposit silicon oxide compounds on a (100)-silicon wafer substrate. In this parametric study, hexamethyldisiloxane (HMDSO) was dissociated under different plasma jet parameters. It was found that by varying the working gas, the treatment time and jet parameters, such as nozzle-to-substrate distance and input energy, it is possible to influence the particles size and the morphology of the thin film. The choice of the working gas plays a major role in the formation of nanoparticles and the surface texture. This study was focused on the particles growth and how the growth can be controlled by tuning the parameters mentioned. Particles size of up to 100 nm was achieved under optimized conditions.

The assessment of a method for measurements and lead quantification in air particulate matter using total reflection X-ray fluorescence spectrometers

This paper presents the assessment of a direct method to measure and analyse Pb in air particulate matter (PM) collected on polytetrafluoroethylene (PTFE) filtering membranes prepared by the SMART STORE® procedure. The suitability of grazing incidence X-ray fluorescence technique is verified on a set of continuous and conformal thin film samples created by atomic layer deposition. Different scans changing the angles of incidence are performed and the fluorescence intensity of thin films on PTFE substrate compared with that obtained by similar thin films deposited on Si wafer substrates. The effects of sample preparation, constraints, and limitations of the experimental setup are discussed. The results obtained by three commercial total reflection X-ray fluorescence spectrometers, equipped with Mo or Rh X-ray tubes, are compared. Reference samples with different Pb content are used to define the best measurement conditions, corresponding to the maximum fluorescence intensity. The precision is evaluated in terms of relative standard deviation of the net intensity, taking into account the homogeneity of the PM samples and hardware contributions to the errors. The calibration curves are built on the basis of mono- and multi-elemental Pb loaded PTFE reference samples. The analytical parameters, namely linear calibration and determination range, limits of detection, and quantification, are determined.

In Situ Formation of Nanoporous Silicon on a Silicon Wafer via the Magnesiothermic Reduction Reaction (MRR) of Diatomaceous Earth.

Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a single crystalline silicon wafer via the magnesiothermic reduction reaction is reported. The formed porous coating of 6 µm overall thickness contains silicon as the majority phase along with minor traces of Mg, as evident from SEM-EDS and the Focused Ion Beam (FIB) analysis. Raman peaks of silicon at 519 cm−1 and 925 cm−1 were found in both the film and wafer substrate, and significant intensity variation was observed, consistent with the SEM observation of the directly formed silicon nanoflake layer. Microstructural analysis of the flakes reveals the presence of pores and cavities partially retained from the precursor diatomite powder. A considerable reduction in surface reflectivity was observed for the silicon nanoflakes, from 45% for silicon wafer to below 15%. The results open possibilities for producing nanostructured silicon with a vast range of functionalities.