Flat Glass Substrate Research Articles

Formation of two-dimensional diamond-like colloidal crystals using layer-by-layer electrostatic self-assembly.

We report here that a two-dimensional (2D) diamond-like structure of micron-sized colloidal particles can be obtained by layer-by-layer self-assembly. Positively and negatively charged silica particles, 1 μm in diameter, were used in the experiments. On a positively charged, flat glass substrate, the first layer of negatively charged particles was prepared to form a non-close-packed 2D crystal. Then the second and third layers were fabricated using electrostatic adsorption. The positions of adsorbed particles were controllable by tuning the zeta-potential of the particles and the salt concentration of the medium. The FDTD calculations show that the 2D diamond structures of particles with higher refractive index (titania) have an absorption band in the wavelength range corresponding to the photonic band gap of the 3D bulk crystal. We expect these findings to be useful for the fabrication of novel photonic materials.

Oxidation resistance and mechanical properties of AlTiZrHfTa(-N) high entropy films deposited by reactive magnetron sputtering

(AlTiZrHfTa)1−xNx refractory high entropy films (RHEFs) were deposited by direct current magnetron sputtering in various nitrogen ratios (RN2 = N2/(Ar+N2)) on flat glass, silicon and sapphire substrates. The nitrogen-free film is amorphous while the nitrides are single-phased solid solutions with Face-Centered Cubic (FCC) structures. The hardness increases from 6.4 GPa for the nitrogen-free film to 25.3 GPa for the film obtained at RN2 = 20%. A preferred orientation from (111) to (200) occurs when RN2 increases from 5% to 50%. H/E and H3/H2 reports show high values for the film deposited at RN2 = 20% compared to that at 10%. However, this latter has the best compromise in terms of mechanical properties related to a lower residual stress value. The nitrides films obtained with RN2 ≥ 5%, are thermally stable at 800 °C for 3 h under vacuum. Compared to the metallic film they show an improved oxidation resistance. In fact, the Kp constant of the nitride (RN2=20%) is lower (1.22 10−7 g2 cm−4 h−1) than that of the nitrogen-free film (1.77 10−6 g2 cm−4 h−1). The corresponding activation energies (Ea) are respectively calculated at 94.8 KJ. mol−1 and 45.5 KJ.mol−1. After oxidation process, TEM analysis reveal the formation of homogeneous mixed oxide.

Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene.

We report the fabrication of hyperbranched hollow crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene on a concave surface of the spherical glass substrate by sublimation and their practical photomechanical behaviors. The number of units of the branched structure of the hollow crystals composed of this compound is proportional to the substrate curvature of the substrate. Compared with the sublimation process of the same compound on the flat glass substrate, two kinds of the thin film domains are generated separately in the center and around the edge of the spherical glass substrate. Especially under the high relative humidity condition, the boundaries between these thin film domains move gradually around the edge through the center during as long as 6 h of sublimation time so that the hyperbranched hollow crystals are densely produced on the entire surface of the substrate. These hyperbranched hollow crystals can be prepared with the highly ordered molecular packing due to the very slow formation process of the crystalline walls of the hollow structures. Furthermore, the photo-induced bending behaviors in the few- and highly-branched hollow crystals have the practical roles in moving and bending the minute objects according to their characteristics of these branched shapes.

Evaluation of analysis volume in total reflection X‐ray fluorescence analysis

AbstractTotal reflection X‐ray fluorescence (TXRF) is widely used for trace elemental analysis, wherein a thin monochromatic X‐ray beam is typically applied at glancing angles. The actual volume of the sample measured by the instrument (analysis volume) depends on the dimensions of the X‐ray beam and glancing angle, and it is a key feature in sample preparation for TXRF analysis. Herein, the analysis volume, including the analysis region and analysis height, was experimentally evaluated. A thin Au layer approximately 5 nm thick and 1 mm in diameter was prepared at a specific position on a flat glass substrate using a vacuum evaporation device. The position of this Au layer was controlled by manipulating a mask plate with a small hole. Nine samples were prepared at different Au layer positions and analyzed at 8 azimuth angles using a tabletop TXRF instrument. Finally, the Au XRF intensity distribution was visualized on a glass substrate. It was found that the XRF emitted over a diameter of approximately 5 mm was effectively detected using the tabletop TXRF instrument. The analysis height was experimentally evaluated using a thin Au layer deposited on a polyimide film 5 mm in diameter and 5 nm thick. The Au layer height was adjusted by inserting polyimide thin films between the Au layer and the glass substrate. The Au XRF intensity drastically decreased with increasing Au layer height, suggesting that the XRF emitted from the sample is effectively detected at heights of <10 μm by using the described setup.

Effect of roughness small scales on the adhesion of randomly rough surfaces with high fractal dimension

Surface roughness affects several tribological phenomena like adhesion. In this work, JKR-like experimental tests were performed between Polydimethylsiloxane (PDMS) spherical samples and flat glass substrates with different surface roughness properties. Data were interpreted in the light of classical JKR theory. We find that adhesion is destroyed by roughness in agreement with the most common and well-known results in the literature. However, from the analysis of the Power Spectral Density (PSD) of the surfaces, it emerges that the smaller scales of roughness have a greater influence on the surface adhesion energy in the range of the high fractal dimensions (D > 2.5). In this range, for surfaces with the same root mean square (RMS) roughness amplitude hrms , which is mainly affected by large scale roughness, the pull-off force (i.e., the maximum tensile force reached during the retracting phase) is observed reducing by increasing the RMS slope of the surface roughness , that is by changing the roughness content at the small scales. This result agrees with recent theoretical findings and has never been shown experimentally in the literature to the best of our knowledge.

A Solvent-Free, Thermally Curable Low-Temperature Organic Planarization Layer for Thin Film Encapsulation.

Thin film encapsulation (TFE) is an essential component to ensure reliable operation of environmentally susceptible organic light-emitting diode-based display. In order to integrate defect-free TFE on display with complex surface structures, additional planarization layer is imperative to planarize the surface topography. The thickness of conventional planarization layer is as high as tens of µm, but the thickness must be reduced substantially to minimize the light leakage in smaller devices such as micro light-emitting diodes. In this study, a thin-less than 2 µm-planarization is achieved via solvent-free process, initiated chemical vapor deposition (iCVD). By adapting copolymer from two soft, but curable monomers, glycidyl acrylate (GA) and 2-(dimethylamino)ethyl methacrylate, excellent planarization performance is achieved on various nano-grating patterns. With only 1.5 µm-thick iCVD planarization layer, a 600 nm-deep trench polyurethane acrylate pattern is flattened completely. The TFE fabricated on planarized pattern exhibits excellent barrier property as fabricated on flat glass substrate, which strongly suggests that iCVD planarization layer can serve as a promising planarization layer to fabricate TFE on various types of complicated device surfaces.

Impact of Temperature and Etching Methods on Surface Roughness, Topography, and Composition of Glass Micromodels

Fluid flow in porous media is affected by surface characteristics such as roughness and topography. In this work, to simulate the surface of natural porous structures in transparent interconnected media like micromodels, various degrees of roughness have been artificially created on flat glass substrates via different methods of laser ablation, cream etching, combination of laser ablation and cream etching, and hydrofluoric acid (HF) etching. The obtained surfaces by each method were characterized in detail via field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX/EDS), and surface profilometry. The impact of high temperature, as often used during the thermal bonding step in micromodel fabrication, on the surface roughness and topography was also investigated. The results show that laser ablation leads to a homogenous distribution of roughness with an average value of 21.7 μm, not affected by temperature during the bonding step. In contrast, the chemical reaction of HF with the glass surface leads to a vast range of roughness values from 8.4 to 31.3 μm, with a heterogeneous distribution, varying with the exposure time. Applying etching cream on a laser-engraved surface reduces the previously created sharp hillocks as a result of a weak chemical reaction with the surface, resulting in a low roughness value of 5.5 μm. No significant changes were observed in the chemical composition of surfaces etched by the abovementioned methods, even in cases where a chemical reaction occurred on the surface, attributed to the water solubility of the reaction products. The novel findings of this study can be used for better controlling the surface characteristics in the fabrication of transparent porous structures to mimic the natural porous media and study the role of surface roughness and topography on fluid flow behavior.

Study on total reflection performance of films grown by atomic layer deposition relevant to X-ray reflective optics.

For X-ray reflective optics that work based on the concept of total external reflection, coating the reflector surface with high-density film is a common idea to enhance performance. Atomic layer deposition (ALD) has been proven to be a promising way to coat the reflector surface with a large curvature, even the inner surface of an X-ray capillary. In this paper, HfO2 and iridium films were prepared on flat silicon and glass substrates via ALD, and X-ray reflectivity (XRR) was used as a main tool to investigate the effect of film properties on the total reflection performance.

Organic abrasive machining system for optical fabrication with 0.1-mm spatial resolution.

High-precision optics for short-wavelength regions, such as x rays and extreme ultraviolet light, generally require nanometer-level figure accuracy on their surfaces. Such optics are finished via a numerically controlled figure correction process in which the dwelling time of the machining tool on the workpiece is controlled. Due to the limitation of the machined spot size, it is difficult to remove mid-spatial-frequency (1 to 10mm-1) errors on an optical surface. To realize a high-spatial-resolution figure correction process for high-precision optics, we have been developing the organic abrasive machining (OAM) technique, which can generate a 100 µm machined spot using a small elastic rotation tool in a slurry that includes acrylic particles. In this study, an OAM apparatus that can measure the machining load was constructed. The effects of the machining and slurry conditions were investigated and high-spatial-resolution machining on a flat glass substrate was demonstrated. The root-mean-square roughness of the surface after OAM processing was below 0.2nm. Patterns with a minimum line and space size of 100 µm were successfully fabricated.

Synthesis of TiO2 Thin Films Nanoparticles with Different Layers using Simple Sol-Gel Method

In this study, titanium dioxide (TiO2 (are synthesized by sol– gel simple method. Thin films of sol, gel, and sol- gel on relatively flat glass substrates are applied with Spin coating technique with multilayers. The optical and morphological properties (studied using AFM) of TiO2 layers show good properties, with particles diameters less than 4 nm for all prepared samples and have maximum length 62 nm for TiO2 gel thin films of three layers. The results show low roughness values for all films especially for 4 layers sol (8.37nm), which improve the application in dye sensitive solar cell (DSSc) .

Developing Novel Poly(Lactic-Co-Glycolic Acid) (PLGA) Films with Enhanced Adhesion Capacity by Biomimetic Mushroom-Shaped Microstructures

The adhesion strength of biomimetic mushroom-shaped microstructures made of a biocompatible and biodegradable copolymer, PLGA, is experimentally studied. The adhesive microstructures were successfully produced using a two-step molding technique. The adhesive experiments were performed on a flat and smooth glass substrate using different normal preloads and under both dry (in air) and wet (underwater) contact conditions. Regardless of contact conditions, mushroom-shaped microstructures generate much higher adhesion strength compared to a flat smooth reference sample made of the same PLGA material. Furthermore, PLGA mushroom-shaped microstructures exhibited superior adhesion strength using agar substrate as a representative material for biological tissue. Surface texturing indicates a good approach to modify adhesive properties PLGA without additional excipients. The effect of surface texturing is more pronounced under wet contact condition. The concept of using biomimetic adhesive surfaces made of biocompatible and biodegradable polymers is very promising for potential applications in drug delivery, tissue engineering and biomedical field.

Substrate effect on the neuromorphic function of nanoionics-based transistors fabricated using WO3 thin film

This paper reports a systematic study on the device characteristics of neuromorphic transistors fabricated by using RF magnetron sputtered WO3 thin film as a channel layer upon atomically flat Si (100), Si (111) and glass substrates. The synaptic behaviour such as learning and forgetting, which are related to short term memory (STM) and memorizing, related to long term memory (LTM) have been demonstrated based on nanoionics phenomena. The conductance modulation using gate-voltage application conditions controls the synaptic behaviour. The switching period, time between learn and forget, has been optimized with gate voltage of within 3 V for the device fabricated on Si (100) substrate. A systematic investigation of substrate effect on the neuromorphic function of devices fabricated with different substrates reveals that the device fabricated on p-type Si(111) exhibits significantly shorter switching ratio, which makes a possibility to modify the device function by the choice of substrate.

Crystallization behavior of electron-beam-evaporated amorphous silicon films on textured glass substrates by flash lamp annealing

Flash lamp annealing (FLA) is one of the short-duration annealing methods suitable for the crystallization of micrometer-order-thick amorphous silicon (a-Si) films for thin-film polycrystalline silicon (poly-Si) solar cells. The crystallization of electron-beam- (EB-) evaporated a-Si films formed on flat glass substrates by FLA is known to take place through explosive crystallization (EC), by which laterally stretched large crystal grains are formed. In this study, we experimentally investigate the behavior of the FLA-induced crystallization of EB-evaporated a-Si films on glass substrates with intentionally roughed surfaces. When a-Si films on the textured glass substrates receive a FL pulse light consisting of sub-pulses with variable emission frequency, macroscopic stripe patterns with a constant width are observed on the poly-Si surface. This indicates the emergence of EC in EB-evaporated a-Si films also on textured glass substrates, similar to the case of a-Si films on flat substrates. Poly-Si films formed on textured glass substrates have smaller Si crystal grains in the vicinity of the Si/glass interface than the grains near the surface. Moreover, the lateral crystallization velocity of a-Si films on textured glass substrates is smaller compared to that on flat glass substrates. These indicate that the behavior of the EC of EB-evaporated a-Si films is affected by the surface morphology of glass substrates.

Evaluation of 3D-printed molds for fabrication of non-planar microchannels.

Replica obtained from micromolds patterned by simple photolithography has features with uniform heights, and attainable microchannels are thus quasi-two-dimensional. Recent progress in three-dimensional (3D) printing has enabled facile desktop fabrication of molds to replicate microchannels with varying heights. We investigated the replica obtained from four common techniques of 3D printing-fused deposition modeling, selective laser sintering, photo-polymer inkjet printing (PJ), and stereolithography (SL)-for the suitability to form microchannels in terms of the surface roughness inherent to the mechanism of 3D printing. There have been limited quantitative studies that focused on the surface roughness of a 3D-printed mold with different methods of 3D printing. We discussed that the surface roughness of the molds affected (1) transparency of the replica and (2) delamination pressure of poly(dimethylsiloxane) replica bonded to flat glass substrates. Thereafter, we quantified the accuracy of replication from 3D-printed molds by comparing the dimensions of the replicated parts to the designed dimensions and tested the ability to fabricate closely spaced microchannels. This study suggested that molds printed by PJ and SL printers were suitable for replica molding to fabricate microchannels with varying heights. The insight from this study shall be useful to fabricate 3D microchannels with controlled 3D patterns of flows guided by the geometry of the microchannels.

Fabrication and Characterization of CdO Gas Sensor with Tube Shape

The based semiconductor-metal oxide gas 3D-detector of cadmium oxide has been fabricated from cadmium chloride salt upon a glass substrate via the technique of spray pyrolysis with a thickness around (0.5 ± 0.01 μm) utilizing precursors in form of water soluble at a flat glass substrate and a tube hollow design. Three different dimensions were used at temperature 450oC±5, in 0.1 and 0.2 M concentration, and their gas sensing characteristics toward the (CO) and (NO) gases at various concentrations (50, 100, and 500 ppmv) in the air were studied at the room temperature which are related to oil industry. Different inspection distances (0, 1 and 5 m) were carried out. Furthermore, structural and morphology properties were inspected via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results manifested that the composition of the formative oxide CdO is related to the tested oxidation gases sensitivity. And, the installation of hollow design is best from flat to capture the gas molecules.

Structural investigation and optical enhancement characterization of nanostructured Ga-doped @CdO/FTO films for photodiode applications

Abstract In this work, the high quality of CdO film with a different percentage of Ga doping prepared onto optically flat glass substrates using a sol-gel spin coating progression for enhancement of its structural characteristics for various applications. X-ray diffraction results confirm that the prepared films of CdO are amorphous due to the long-range array of deposited crystals. The images of the atomic force microscopy indicated that the surface morphology of the pure and Ga-doped CdO films has high roughness values of 60–80 nm and average particle size 85–100 nm. The optical constants were calculated using the Kramer-Kronig approach. The calculated optical transmission specifies a high transmission exceeding from 77% to 85% through the non-absorbing region depending on the doping concentrations. The results confirm that the measured optical band gap is strongly influenced by doping concentrations of Ga and decreases from 2.35 to 1.72 eV. The calculated optical dispersion and non-linear optical parameters were found to be strongly affected by doping. The terahertz cut-off frequency was set for the pure and Ga-doped CdO films indicating the applicability of the prepared films as terahertz filters.

Fabrication, carrier transport mechanisms and photovoltaic properties of Au/silicon phthalocyanine dichloride/p-Si/Al heterojunction device

This research paper aims to study the carrier transport mechanisms and photovoltaic properties of the SiPcCl2 thin film. To achieve this, Au/silicon phthalocyanine dichloride (SiPcCl2)/p-Si/Al heterojunction device was prepared. The heterojunction microelectronic parameters such as ideality factor, m and reverse current Is were estimated at room temperature and found to be 6.77 and 408 nA respectively. The series resistance Rs of the fabricated device was also calculated. Two mechanisms were deduced in SiPcCl2/p-Si according to the voltage range. The results revealed that the height of effective barrier $$\varphi_{bi}$$ is clearly increased from 0.71 to 0.80 eV. Moreover, the photovoltaic properties of Au/SiPcCl2/p-Si/Al cell were studied under illumination such as the short circuit current, Isc, open circuit voltage, Voc, maximum current IM, maximum voltage, VM, filling factor FF and power conversion efficiency, η were measured to be 0.59 mA, 0.47 V, 0.44 mA, and 0.24 V, 0.40 and 3.7% respectively. The topographical properties of the SiPcCl2 thin film deposited on the flat glass substrate were investigated using atomic force microscope method.

The formation of self-assembled structures of C60 in solution and in the volume of an evaporating drop of a colloidal solution

The results of experiments on the self-aggregation of C60 fullerene molecules both inside a two-component solvent (xylene/tetrahydrofuran) and in the volume of an evaporating drop of C60 colloidal solution on a flat substrate surface are presented. The investigations of C60 solutions using dynamic light scattering, transmission electron microscopy and UV–Vis absorption spectroscopy methods revealed the possibility of synthesis of fractal nanoaggregates with a diameter of up to ~135 nm at low concentrations of C60 in the solutions. The final geometric dimensions of C60 nanoaggregates were determined by the initial concentration of fullerene in the solvent medium. Using the scanning electron microscopy method, we have shown that in an open dissipative system – in the volume of an evaporating droplet of the colloidal solution of fullerene C60 sessile on the surface of a flat glass substrate, large quasispherical nanoaggregates with an average diameter of ~380–800 nm are formed. The physical features and regularities that characterize the processes of self-aggregation of fullerene particles in the volume of a drying drop were determined.

Collagen hydrogel confinement of Amyloid-β (Aβ) accelerates aggregation and reduces cytotoxic effects

Alzheimer's disease (AD) is the most common form of dementia and is associated with the accumulation of amyloid-β (Aβ), a peptide whose aggregation has been associated with neurotoxicity. Drugs targeting Aβ have shown great promise in 2D in vitro models and mouse models, yet preclinical and clinical trials for AD have been highly disappointing. We propose that current in vitro culture systems for discovering and developing AD drugs have significant limitations; specifically, that Aβ aggregation is vastly different in these 2D cultures carried out on flat plastic or glass substrates vs. in a 3D environment, such as brain tissue, where Aβ confinement alters aggregation kinetics and thermodynamics. In this work, we identified attenuation of Aβ cytotoxicity in 3D hydrogel culture compared to 2D cell culture. We investigated Aβ structure and aggregation in solution vs. hydrogel using Transmission Electron Microscopy (TEM), Fluorescence Correlation Spectroscopy (FCS), and Thioflavin T (ThT) assays. Our results reveal that the equilibrium is shifted to stable extended β-sheet (ThT positive) aggregates in hydrogels and away from the relatively unstable/unstructured presumed toxic oligomeric Aβ species in solution. Volume exclusion imparted by hydrogel confinement stabilizes unfolded, presumably toxic species, promoting stable extended β-sheet fibrils. Statement of SignificanceAlzheimer's disease (AD) is a devastating disease and has been studied for over 100 years. Yet, no cure exists and only 5 prescription drugs are FDA-approved to temporarily treat the AD symptoms of declining brain functions related to thinking and memory. Why don't we have more effective treatments to cure AD or relieve AD symptoms? We propose that current culture methods based upon cells cultured on flat, stiff substrates have significant limitations for discovering and developing AD drugs. This study provides strong evidence that AD drugs should be tested in 3D culture systems as a step along the development pathway towards new, more effective drugs to treat AD.

Effect of temperature, humidity and pressure on electric properties of the cells based on PTB7-Th, PC61BM and graphene composite

In this paper, fabrication and characterization of Cu/PTB7-Th (35 mass%)/PC $$_{61}$$ BM (35 mass%)/graphene (30 mass%)/Ag thin-film composite cells are given. First of all, Ag and Cu electrodes were deposited on flat glass substrate by vacuum evaporation with 130- $$\upmu $$ m inter-electrode gap. The PTB7-Th (35 mass%) composite and PC $$_{61}$$ BM (35 mass%) composite in chlorobenzene and graphene (30 mass%) were deposited on the inter-electrode gap by drop-casting technique, and film thickness of 8–12 $$\upmu $$ m was achieved. The dependence of forward and reverse bias resistance of the cells versus temperature in the range of 25–75 $${^{\circ }}$$ C, humidity in the range of 47–90 %RH and pressure in the range of 0–7.7 kN m $$^{-2}$$ was measured. The average temperature resistance coefficients were equal to (− 1.03)% $${^{\circ }}\hbox {C}^{-1}$$ and $$(-\,1.14)\%\ {^{\circ }}\hbox {C}^{-1}$$ for forward and reverse bias resistances, respectively. The reverse and forward bias resistances decreased 1.29 and 1.27 times due to $$\%\mathrm{RH}$$ , and due to pressure, it decreased by 9.0–9.2%. Impedance (Z) of the sample was also measured at different frequencies (100 Hz, 1 kHz, 10 kHz and 100 kHz) which decreased from 1.23 to 1.04 times. The obtained results are explained, firstly, by transfer of charges between donors and acceptors molecules and effect of water molecules on the PTB7-Th (35 mass%):PC $$_{61}$$ BM (35 mass%):graphene composite.