Flat Glass Substrate Research Articles

Scattering, Diffraction, and Geometric Light Trapping in Thin Film Amorphous Silicon Solar Cells on Plastic Substrates

ABSTRACTIn this study we compare light trapping in hydrogenated amorphous silicon (a-Si:H) solar cells deposited directly onto polycarbonate (PC) at low temperature (< 130°C). To that end, we embossed PC substrates with 400 nm and 10 μm square based pyramids to induce light trapping based on diffraction and on geometric effects. As a comparison, we deposited a-Si:H cells on flat glass substrates and on Asahi U-type TCO glass. The cells on PC generate current densities comparable (slightly higher) than cells on Asahi TCO glass, but suffer from a slightly lower Voc, resulting in cells with an initial efficiency of 6.8% and 7.4% on sub-micron pyramid and micro-pyramid structured PC substrates respectively, compared to 7.6% for cells on Asahi. This shows great potential for a-Si:H cells deposited directly onto cheap plastics.

SOLARC® Anti-Reflective Coating Material for High Transfer Efficiency Application Process

ABSTRACTIt has been demonstrated in literature that chemical liquid deposition (CLD) processes such as dip coating, spray coating, roll coating, spin coating, curtain coating, meniscus coating etc. can be successfully used to deposit anti-reflective coatings on glass substrates. In comparison to physical vapor deposition (PVD), a CLD process generally is cost efficient because of lower capital requirements to set up coating manufacturing lines. Within the realm of CLD processes only some application techniques are suitable for high speed continuous manufacturing processes to deposit coatings on large area glass substrates. Significant differences in transfer efficiencies of these high speed application processes are readily apparent when material utilization per unit area of glass are compared. Roll coat process among all the high speed CLD processes stands out for its high material transfer efficiency due to direct contact printing on flat glass substrates. Honeywell Electronic Materials expanded its line of SOLARC® anti-reflective coating materials to include a new coating formulation SOLARC® RPV, which is customized for roll coating application. This paper highlights the advantages of using SOLARC® RPV in roll coat process and the performance attributes of SOLARC® anti-reflective coatings. Durability characteristics of these anti-reflective coatings in accelerated aging tests designed to simulate harsh field conditions will also be discussed.

Collagen fibril diameter and alignment promote the quiescent keratocyte phenotype

In this study, we investigated how matrix nanotopography affects corneal fibroblast phenotype and matrix synthesis. To this end, corneal fibroblasts isolated from bovine corneas were grown on collagen nanofiber scaffolds of different diameters and alignment--30 nm aligned fibrils (30A), 300 nm or larger aligned fibrils (300A), and 30 nm nonaligned fibrils (30NA) in comparison with collagen coated flat glass substrates (FC). Cell morphology was visualized using confocal microscopy. Quantitative PCR was used to measure expression levels of six target genes: the corneal crystallin-transketolase (TKT), the myofibroblast marker-α-smooth muscle actin (SMA), and four matrix proteins-collagen 1 (COL1), collagen 3 (COL3), fibronectin (FN), and biglycan. It was found that SMA expression was down-regulated and TKT expression was increased on all three collagen nanofiber substrates, compared with the FC control substrates. However, COL3 and biglycan expression was also significantly increased on 300A, compared with the FC substrates. Thus matrix nanotopography down-regulates the fibrotic phenotype, promotes formation of the quiescent keratocyte phenotype, and influences matrix synthesis. These results have significant implications for the engineering of corneal replacements and for promoting regenerative healing of the cornea after disease and/or injury.

The syntheses of thin layers of organosilica by the co-condensation of tetraethoxysilane and phenyltriethoxysilane in the presence of cationic surfactant

Thin layers (with the thickness of several tens of nanometers) of silica-surfactant hybrids were deposited on flat glass substrate from aqueous methanol solution of tetraethoxysilane, phenyltriethoxysilane, alkyltrimethylammonium chloride, and ammonia by the reaction at room temperature. Multilayered films were deposited on flat substrates by repeating the film preparation procedure. Due to the reproducible syntheses, the films are possible candidates as scaffold of sensor and photonic coatings. A hexagonal platy core–shell particle with a hydrotalcite core and organosilica shell was also synthesized by the reaction of hydrotalcite with aqueous methanol solution containing tetraethoxysilane, hexadecyltrimethylammonium chloride, and ammonia. A hollow hexagonal platy particle was obtained by removing the hydrotalcite from the core–shell particle by acidic leaching. The organosilica-coated particles may affect the anion exchange selectivity of hydrotalcite, and the organosilica hollow particle is possible candidate as a new class of carried due to the unique platy particle shape.

Development of a Physically Bent Cylindroid Mirror for Beam Focusing for a Pulsed Neutron Reflectometer

To gain in intensity and realize a grazing-incidence small-angle scattering (GISAS) measurement on a pulsed neutron reflectometer, we are now developing focusing devices using a cylindrically bent supermirror coated on a flat float glass substrate. They have been characterized at pulsed neutron sources, and we successfully focused neutron beam into about 1mm width in either vertical or horizontal direction using the bent mirror with the focal distance of about 4 m.

3.4-Inch Quarter High Definition Flexible Active Matrix Organic Light Emitting Display with Oxide Thin Film Transistor

In this paper, we report a 3.4-in. flexible active matrix organic light emitting display (AMOLED) display with remarkably high definition (quarter high definition: QHD) in which oxide thin film transistors (TFTs) are used. We have developed a transfer technology in which a TFT array formed on a glass substrate is separated from the substrate by physical force and then attached to a flexible plastic substrate. Unlike a normal process in which a TFT array is directly fabricated on a thin plastic substrate, our transfer technology permits a high integration of high performance TFTs, such as low-temperature polycrystalline silicon TFTs (LTPS TFTs) and oxide TFTs, on a plastic substrate, because a flat, rigid, and thermally-stable glass substrate can be used in the TFT fabrication process in our transfer technology. As a result, this technology realized an oxide TFT array for an AMOLED on a plastic substrate. Furthermore, in order to achieve a high-definition AMOLED, color filters were incorporated in the TFT array and a white organic light-emitting diode (OLED) was combined. One of the features of this device is that the whole body of the device can be bent freely because a source driver and a gate driver can be integrated on the substrate due to the high mobility of an oxide TFT. This feature means “true” flexibility.

Effects of Surface Free Energy on Orientational Assembly of Hexaazatrinaphtalene-Based Discotic Mesogen in Sandwich-Type Structure

The molecular stacking of a hexaazatrinaphtalene-based discogen sandwiched between two flat glass substrates has been studied. The surface free energy of the substrates was found to significantly influence the way the discotic molecules anchor on the surface. The surface free energy of the substrates was changed by means of O2 plasma buffing. The discotic molecules tend to anchor with their disc-face toward the substrates with high surface free energy, and the other molecules stack on to form the homeotropically aligned columnar phase. A decrease in the surface free energy of the substrate leads to the discotic columns tilting away from the normal to the substrate.

Bidimensional codes recorded on an oxide glass surface using a continuous wave CO2 laser

Surface heat treatment in glasses and ceramics, using CO2 lasers, has attracted the attention of several researchers around the world due to its impact in technological applications, such as lab-on-a-chip devices, diffraction gratings and microlenses. Microlens fabrication on a glass surface has been studied mainly due to its importance in optical devices (fiber coupling, CCD signal enhancement, etc). The goal of this work is to present a systematic study of the conditions for microlens fabrications, along with the viability of using microlens arrays, recorded on the glass surface, as bidimensional codes for product identification. This would allow the production of codes without any residues (like the fine powder generated by laser ablation) and resistance to an aggressive environment, such as sterilization processes. The microlens arrays were fabricated using a continuous wave CO2 laser, focused on the surface of flat commercial soda-lime silicate glass substrates. The fabrication conditions were studied based on laser power, heating time and microlens profiles. A He–Ne laser was used as a light source in a qualitative experiment to test the viability of using the microlenses as bidimensional codes.

Surface Plasmon Resonance on the Sapphire Single Crystal Substrates with 3D Nano-Textured Surface

Surface plasmon resonance (SPR) bio-sensors comprise an attenuated total reflection (ATR) system known as the Kretschmann geometry. The sensing surface comprises flat Au thin films deposited on a high index flat glass substrate (LAL-10, n = 1.72). This paper describes the effects of the 3D nano-textured Au thin films on the sensing properties are discussed. The nano-textured Au thin films were fabricated by the deposition of the uniform Au thin films on the (0001) vicinal sapphire substrates. The vicinal substrates comprise periodic atomic step lines and terraces. The step height is chiefly half lattice spacing of the sapphire (0.22 nm). The terrace width is governed by the off-cut angles. The stepped surface structure were reconstructed by the annealing at 900 to 1400oC (1 to 3 h) in air. The annealed stepped surfaces comprised stepped heights of 5 to 12 nm with the terrace width of 2.7 to 140 nm for the off-cut angles at 5 degrees. The laser diodes (635 nm) were used for the optical light source. It is found that the detection limit of the SPR bio-sensors using the flat Au thin films on the (0001) sapphire substrates is 1.6 ng/ml for the tumor marker (AFP, α-fetoprotein) by antibody/antigen reaction, which is almost the same to the performance of the flat Au thin films on the conventional high index glass substrates as expected by the simulation Winspal 2. The SPR sensitivities using the nano-textured Au thin films with the step height of 12 nm and the terrace width of 140 nm were one order of magnitude smaller than those of Au thin films on the flat (0001) sapphire, 20 ng/ml, probably due to the scattering of the surface plasmon and/or evanescent wave. However, well-designed nano-textured Au thin films will enhance the SPR sensitivity. The sapphire substrates could integrate optical devices and will provide novel optical-bio MEMS.

XPS Studies on Light-Yellow Glass Prepared by Sol-Gel Dip-Coating

Light-yellow glass was prepared by coating silver film on the flat glass substrate surface with sol-gel dip-coating process. The chemical composition and the valence state of elements on the surface of silver thin film deposited on glass substrate were studied by X-ray photoelectron spectroscopy. Results show that: elements of Na, Mg, Ca exist in the form of their respective stable state, such as Na2O, MgO, CaO, when heat treated at 500°C for 0.5h; but Si is unstable, and exhibit stoichiometrical disturbances. Results of chemical composition and their content by weight percent of silver thin film surface reveal that minute of quantity silver on the glass surface can lead to the glass with light-yellow color. The transmission of light for the light-yellow glass, deep-yellow glass and the flat glass substrate was also analyzed by spectrophotometer, and the results indicate that the light-yellow glass is capable of absorbing UV rays heavily.

Adhesion of Oil to Kaolinite in Water

Uniform coats of kaolinite particles on a flat glass substrate were prepared to be sufficiently smooth and thin to allow reliable measurement of contact angles of captive crude oil drops in a range of salt solutions, without any particle removal. The contact angle hysteresis was used to infer the extent of oil adhesion via rupture of the intervening water film and anchoring of charged groups to kaolinite. For sodium chloride solutions, adhesion decreases monotonically with pH and/or salinity, with strong adhesion only manifested under acidic conditions with salinity at most 0.1 M. Calcium chloride solutions at pH around 6 switch from strong adhesion in the range 0.001-0.01 M to weak adhesion at higher concentrations. For all mixtures of sodium and calcium chlorides investigated, a total ionic strength above 0.1 M guarantees a weak adhesion of oil to kaolinite. Results are qualitatively consistent with theoretical expectations of electrostatic interactions, with H(+) and Ca(2+) being potential-determining ions for both interfaces.

Photoelectrocatalytic Wastewater Treatment Using TiO2/ITO Bilayers Prepared on Optical Fibers by Pulsed Laser Deposition

Advanced oxidation processes (AOPs), on the basis of photoelectrochemical reactions, constitute a good alternative for treating wastewaters contaminated with refractory organic compounds such as dyes. For this purpose, different approaches have been explored to develop novel photoanodes that can be efficiently used in these systems. In this context, this study deals with a comparison of indium tin oxide (ITO) thin films deposited at room temperature by pulsed laser deposition on flat glass and on silica optical fiber (SiO2 core, 600 µm diameter) substrates. Characterization data reveal that nanostructured ITO thin films with resistivity values from 4.4×10-2 to 5.6×10-4 Ω·cm were obtained. To build the photoanode, the ITO thin films were coated with a TiO2 layer deposited by using the electrophoretic method. The prepared TiO2/ITO bilayers on optical fibers showed a better photocatalytic performance than those deposited on flat glass substrates according to TOC and color removal measurements from dye contaminated water samples. These results suggest that the deposited materials exhibit suitable properties for their application in photoelectrocatalytic devices that, employing optical fiber as support and light transmitter, can be efficiently used for the elimination of organic contaminants in industrial wastewaters.

Adhesion Performance of Polymer Nanofibres Under Shear Loading

Geckos have extraordinary wall-climbing ability because of the millions of hairs with micro/nano fibrillar structures on their feet. Mimicking gecko's feet is of scientific and engineering importance for development of physical adhesion materials and devices. The design of gecko-inspired physical adhesives seems to be geometry dominated. In this study, Finite Element Method (FEM) has been used to analyse the vertical peel-off force of polyporpylene (PP) nanofibres having different fibre dimensions, inclining angels and contact areas on a flat glass substrate. It has been found that the main parameters affecting the frictional adhesion are fibre diameter and fibre aspect ratio, the inclining angle between the fibre and the substrate surface, and the intimate contact areas. Our analysis has shown that PP nanofibres with a diameter of less than 200nm can generate less peel-off force than fibres of larger diameters, indicating more stable adhesion with the glass substrate for thinner fibres. A bent fibre with more intimate contact area can bear more shear force than a straight fibre with less contact area. Also, under the same shear loading, fibres with an inclining angle of less than 30° provide a low peel off force.

Fabrication of aligned ultra-thin transparent conductive films of single-walled carbon nanotubes by a compression/sliding method

We demonstrate a novel, simple and scalable method for the fabrication of aligned ultra-thin transparent conductive films of single-walled carbon nanotubes (SWNTs). Pressing and sliding a thin liquid film of surfactant-stabilized SWNTs or SWNT–polymer complex ink between two parallel flat glass substrates provided a high order of directional alignment of nanotubes in the plane of the substrate along the sliding direction. The films showed high optical transmittances in the range of 95–98% at 550 nm and corresponding electrical resistances of 700–800 Ω □−1.

Orientational Packing of a Confined Discotic Mesogen in the Columnar Phase

The stacking of discotic molecules (hexakis(alkoxy)diquinoxalino[2,3-a:2′,3′-c]phenazines) in the columnar phase sandwiched between two flat glass substrates has been studied. The surface free energy of the substrates, measured by means of sessile drop technique, is found to have significant influence on the way that the discotic molecules anchor on the surface, and a steady thermal state of the system is crucial for a homogenous orientation of the discotic columns. On a surface of high free energy, the discotic molecules anchor with their disc-face toward the surface. A decrease in the surface free energy of the substrate causes the discotic columns to tilt away from the normal of the substrate.

Chemoenzymatic synthesis of amylose-grafted poly(vinyl alcohol)

In this study, we synthesized an amylose-grafted poly(vinyl alcohol) (PVA) (4) by a chemoenzymatic method. First, synthesis of an amine-functionalized PVA (2) was carried out by reduction of an azide-functionalized PVA (1) using NaBH4. Then, introduction of maltoheptaose to 2 was performed by reductive amination using NaBH3CN to produce a maltoheptaose-grafted PVA (3). Finally, a phosphorylase-catalyzed enzymatic polymerization of α-D-glucose 1-phosphate from the maltoheptaose-chains in 3 was carried out to obtain 4. A film of 4 was prepared by drying its aqueous solution spread on a flat quartz glass substrate. An iodine-doped film was prepared by soaking the film of 4 in KI/I2ethanol solution. UV-Vis analysis indicated that iodine was retained in this film even after it was left standing for 24 h. This is probably because the iodide ion was within the cavities of the amylose graft chains in this film.

Controlled Flats on Spherical Polymer Colloids

Colloidal particles with heterogeneous surfaces offer rich possibilities for controlled self-assembly. We have developed a method for preparing micrometer-sized polystyrene spheres with circular flat spots of controlled radius and location. The flats are created by settling the particles onto a flat glass substrate and then raising the temperature above the glass-transition temperature of the polymer for a controlled time (t). The polymer particle spreads on the glass such that the radius of the flat grows with time. We present a scaling theory for the hydrodynamics of the flattening process, finding that the radius of the flat grows as t(1/3). The model is in good agreement with our experimental observations of the flat radius versus spreading time as well as with previous studies in the literature for sintering polymer spheres.

Influence of groove depth and surface profile on fluorescence enhancement by grating-coupled surface plasmon resonance

The fluorescence intensity of a sample placed on a metal grating pattern is enhanced due to excitation by the electric field of the grating-coupled surface plasmon resonance (GC-SPR). The dependence of the enhancement on groove depth and surface profile was studied with the aim of improving the sensitivity of fluorescence detection. The enhancement was found to depend on the groove depth, with intensity most enhanced on grating substrate of about 20 nm depth, which produced an intensity about 30 times greater than that on a flat borosilicate glass substrate. Rigorous coupled wave analysis calculation showed that the shape of the groove influenced GC-SPR, suggesting that controlling not only the depth but also the shape of the grating surface profile can be an important factor in improving the sensitivity of detection by fluorescence microscopy.

Dependence of the Quality of Adhesion between Poly(dimethylsiloxane) and Glass Surfaces on the Conditions of Treatment with Oxygen Plasma

Treatment with oxygen-containing plasma is an essential step for the fabrication of devices containing components of polydimethylsiloxane (PDMS). Such oxidative treatment chemically modifies the surface of PDMS allowing it to permanently adhere to glass, quartz, PDMS and other silica-based substrates. Overexposure of PDMS to oxidative gas plasma, however, compromises its adhesiveness. Therefore, regulation of the duration and the conditions of the plasma treatment is crucial for achieving sufficient surface activation without overoxidation. Using a semiquantitative ternary approach, we evaluated the quality of adhesion ( QA) between flat PDMS and glass substrates pretreated with oxygen plasma under a range of different conditions. The quality of adhesion manifested good correlation trends with the surface properties of the pretreated PDMS. Examination of the QA dependence on the treatment duration and on the pressure and the RF power of the plasma revealed a range of oxidative conditions that allowed for permanent adhesion with quantitative yields.

A slip sensor for biorobotic applications using a hot wire anemometry approach

We report on a novel slip microsensor that uses a strategy similar to the one employed in hot wire anemometry. The device includes a miniaturized probe kept at constant temperature by a dedicated control. The sensor fires a signal whenever it detects an increase in the convective heat transfer associated with the occurrence of mechanical slip. The sensor is microfabricated by patterning multi-layer electrodes on a flat glass substrate. The operating principle, fabrication procedures, and control strategy for the device are described in detail. A simple experimental setup was used to test the effectiveness of the proposed device. Tests were performed on bars of four commonly used materials with varying thermal properties. Also, the slip speed was varied and its effect on the performance of the sensor was evaluated. The results show that, with careful choice of the operational parameters, slip can be detected with a response time comparable to that of human skin receptors. The performance of the device can be further improved when used in conjunction with a separate pressure sensor and by improving the accuracy of the electrical resistance readings.