Conventional Glass Substrates Research Articles

Colorless Polyamide–Imide Films with Enhanced Thermal and Dimensional Stability and Their Application in Flexible OLED Devices

In this study, we intend to solve the problem of the low glass transition temperature (Tg) and the high coefficient of thermal expansion (CTE) that colorless polyimide (PI) films always exhibit. First, we copolymerized 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine (TFDB) with 4,4′-(hexafluoroisopropene) diphthalic anhydride (6FDA) and p-phthaloyl chloride (TPC) and obtained a series of transparent and colorless films (PAI-10). These PAI films showed a high Tg of 346–362 °C and a low CTE of 25.2–62.9 ppm/K, which were better than those of PI6FDA-TFDB. Subsequently, three rigid diamines, p-phenylenediamine (p-PDA), 5-amino-2-(4-aminophenyl)benzoxazole (DAPBO) and 5-amino-2-(4-aminophenyl)benzimidazole (DAPBI), were used to replace 10% of the TFDB (PAI-9P-5, PAI-9O-5, and PAI-9I-5, respectively) to investigate the effect of the rigid structure on the thermal and optical properties. The results showed that rigid structures can greatly improve the thermal properties but impair transparency to some extent. Among these, PAI-9O-5 possessed the best performance with T430 of 81.9%, Tg of 364 °C, and CTE of 19.8 ppm/K. Furthermore, we fabricated an organic light-emitting diode (OLED) with PAI-9O-5 as the substrate. The flexible and bendable OLED@PAI-9O-5 showed typical green emission at 520 nm, a turn-on voltage of 2.9 V, a luminance of 1000 cd/m2 at 5 V, a current efficiency (CE) of 2.53 cd/A, and an external quantum efficiency (EQE) of 0.81%, which were comparable to those of devices fabricated on conventional glass substrates.

Synthesis and Characterization of the Ternary Nitride Semiconductor Zn2VN3: Theoretical Prediction, Combinatorial Screening, and Epitaxial Stabilization

Computationally guided high-throughput synthesis is used to explore the Zn-V-N phase space, resulting in the synthesis of a novel ternary nitride Zn$_2$VN$_3$. Following a combinatorial PVD screening, we isolate the phase and synthesize polycrystalline Zn$_2$VN$_3$ thin films with wurtzite structure on conventional borosilicate glass substrates. In addition, we demonstrate that cation-disordered, but phase-pure (002)-textured, Zn$_2$VN$_3$ thin films can be grown using epitaxial stabilization on {\alpha}-Al2O3 (0001) substrates at remarkably low growth temperatures well below 200 {\deg}C. The structural properties and phase composition of the Zn$_2$VN$_3$ films are studied in detail using XRD and (S)TEM techniques. The composition as well as chemical state of the constituent elements are studied using RBS/ERDA as well as XPS/HAXPES methods. These analyses reveal a stoichiometric material with no oxygen contamination, besides a thin surface oxide. We find that Zn$_2$VN$_3$ is a weakly-doped p-type semiconductor demonstrating broadband room-temperature photoluminescence spanning the range between 2 eV and 3 eV. In addition, the electronic properties can be tuned over a wide range via isostructural alloying on the cation site, making this a promising material for optoelectronic applications.

Silicon substrate significantly alters dipole-dipole resolution in coherent microscope

Considering a coherent microscopy setup, influences of the substrate below the sample in the imaging performances are studied, with a focus on high refractive index substrate such as silicon. Analytical expression of 3D full-wave vectorial point spread function, i.e. the dyadic Green's function is derived for the optical setup together with the substrate. Numerical analysis are performed in order to understand and compare magnification, depth of field, and resolution when using silicon substrate versus the conventional glass substrate or usually modelled condition of no substrate. Novel insights are generated about the scope of resolution improvement due to near field effect of the silicon substrate. Importantly, we show that the expected resolution varies greatly with the position of the sources and the substrate interface relative to the focal plane. Both better and worse resolution as compared to glass substrate may be expected with small changes in their positions. Therefore, our studies show that deriving a single indicative number of expected resolution is neither possible nor judicious for the case of silicon substrate.

Enhanced thermal stability and monodomain growth in a 3D soft photonic crystal aided by graphene substrate

We report the growth of monodomain blue phase liquid crystal and its thermal stability on reduced graphene oxide-grown quartz substrates using optical reflection microscopy and spectroscopy. Optical textural images show that the graphene substrate enhances the thermal range of the blue phase by a factor of four compared to conventional ITO-coated glass substrate. The phase is stabilized down to sub-ambient temperatures (from 60 °C to 18 °C) with the blue phase domains remaining undistorted at ambient conditions for more than three months. Also, the graphene substrate aids the monodomain formation with the average BP platelet size being nearly two orders of magnitude larger compared to the ITO / bare quartz substrates. The enhanced thermal stability and single-crystal-like growth of the blue phase are due to the improved wettability and non-covalent π-π interaction between graphene layers and liquid crystal molecules, as confirmed from the contact angle and Raman spectroscopic measurements respectively. Thus, the room temperature stable, graphene layer-stabilized-blue phase is an ideal candidate for high-performance photonic applications.

Comparative Study of Characteristics of Dye Sensitized Solar Cells Fabricated Using Substrates Coated with Fluorine Doped Tin Oxide and Titanium

Dye-sensitized solar cells (DSSCs) have attracted many researchers because it has potential to supplement and compete with other solar cell technologies like Silicon (Si) and Cadmium Telluride (CdTe). The fabrication of DSSCs requires a photo electrode and a counter electrode of transparent and conducting nature. The commercial DSSCs uses electrodes of fluorine doped tin oxide (FTO) glass substrates. These electrodes are expensive and hence, possible alternative materials that are cheaper and that would provide better performance under similar environmental condition should be explored. In this paper, titanium (Ti)-coated glass substrates were prepared and then used to prepare electrodes for fabricating DSSCs. Similarly, DSSCs were fabricated using electrodes of conventional FTO-coated glass substrates. Performance characteristics like cell efficiency (η%), fill-factor (FF), short circuit current density (JSC) and open circuit voltage (VOC) of both fabricated DSSCs were obtained using their respective J-V characteristic curves under similar illumination of 100 mW/cm2 and with comparable transmittance under the visible transmission spectrum of 300-850 nm. The obtained results showed that DSSCs prepared using electrodes of FTO coated glass substrates have 1.557 times better cell efficiency and 2.172 times better fill factor than that of DSSCs fabricated using electrodes of Ti-coated glass substrates.

A portable standalone wireless electric cell-substrate impedance sensing (ECIS) system for assessing dynamic behavior of mammalian cells

In this study, we have developed a wireless, portable, standalone, and simple electric cell-substrate impedance sensing (ECIS) system to analyze in-depth functional aspects of cellular functions on the surface of a co-planar metal electrode coated on conventional glass substrate using a low-cost circuitry and correlated it with an equivalent electrical circuit (EEC) model. Low-cost circuitry was used for studying the dynamic behavior of the mouse myoblast cells (C2C12) in a culture chamber. Further, the developed ECIS system was connected with 8-bit Arduino UNO microcontroller board for establishing a compact sized measuring unit, which can be placed inside a CO2 incubator to provide proper environmental condition for the biological cells during the entire measuring time. Integrating ZigBee RF module with the 8-bit Arduino UNO microcontroller board provides a wireless communication network. Theoretical calculation of the lumped-elemental electrical parameters associated with cell-electrolyte interface and metal-electrolyte interface was calculated. The calculation was performed by fitting the experimental impedance data to EEC model using least mean square method to determine the dynamic and vital functions of the mammalian cells such as proliferation (in real-time) with a change in intrinsic electrical parameters associated at any particular time point. Impedance measurements and the lumped-elemental electrical parameter were correlated with the respective microscopic images. The developed ECIS system was found to enable measuring of the extent of cellular proliferation over time. The compactness of the developed ECIS system integrated with the ZigBee RF module and the 8-bit Arduino UNO microcontroller board facilitates its utilization even when placed in the CO2 incubator for a prolonged time.

Bi@Bi4Ti3O12/TiO2 films on glass with photocatalytic and self‐cleaning performance

AbstractA stable and translucent Bi@Bi4Ti3O12/TiO2 film was fabricated on conventional glass substrates for the first time. The film exhibited a good photocatalytic performance and efficient self‐cleaning capability against organic dyes under full spectral irradiation and visible light irradiation. Bi4Ti3O12/TiO2 film was first prepared on a glass substrate with colloidal silica as a high temperature binder, followed by implantation of nanoscale Bi in it by an in‐situ partially reduction of Bi4Ti3O12 to generate Bi@Bi4Ti3O12/TiO2 films. The improved photocatalytic ability is probably attributed to the surface plasmon resonance of Bi atom as well as the enhanced electron transfer efficiency and synergistic effect of Bi4Ti3O12 and TiO2. According to trapping experiments, hydroxyl radicals (OH) were active species in the photocatalytic degradation of dyes under full spectral light irradiation and possible photocatalytic mechanism was proposed. The film prepared in this work may well have potential practical applications in many aspects, such as cleansing treatments for high building external decorative panels and also systematic characterization of the film suggests that the in‐situ reduction is an effective and simple way to produce nanoscale Bi@Bi4Ti3O12.

Near-field spectrum retrieving through non-degenerate coupling emission

Abstract We present a scheme to retrieve the initial spectrum of probe molecules in the near field. This is achieved by replacing conventional glass substrates with a hybrid mode photonics chip to create rich and persistent mode distributions and by observing the far-field scattering pattern. The manner of coupling from near field to far field is confirmed by the calculated dependence of the coupled emission signal on the unique material properties. By using an optimization algorithm to retrieve the intensity ratio of near-field optical signals in each frequency band gradually without the need for complicated instruments and time-consuming acquisition processes, our method can achieve broadband non-distortion spectral analysis in an enhanced optical antenna by selecting substrate parameters.

Synthesis of a chalcopyrite material, based on CuIn1−xGaXSe2(X = 0.3 y 0.5), for application as semiconductor layer, deposited by a low-cost technique

The current work reports the synthesis and characterization of a photovoltaic material based on the CuIn1−xGaXSe2(X = 0.3 y 0.5) system, making use of the doctor blade method. For this purpose, homogeneous inks were obtained and worked under previous stoichiometry arrangement. The deposition process of thin films, were made in a heating plate on conventional glass substrates, previously washed and treated for this purpose. Once the layers of Cu, In, and Ga were deposited by chemical bath, a thermal treatment was performed at 550 °C for 30 min in a conditioned oven, in which the selenization process was performed. The obtained films were characterized by X-ray diffraction, Raman spectroscopy, solid-state impedance spectroscopy, UV spectroscopy and scanning electron microscopy techniques. The identification of the main crystalline phase could be corroborated, as well as the conductive and optoelectronic behavior of the solids in accordance with reported in literature. Simultaneously, it was checked that the method used allows obtaining layers of an optimum thickness, in order to be used as an absorbent layer in the design of solar devices.

Controlling the extremely preferred orientation texturing of sol–gel derived ZnO thin films with sol and heat treatment parameters

In this article, material and process variables of sol–gel method are considered to investigate the texturing growth model of ZnO thin film in order to achieve ordinary, highly, and extremely preferred ZnO thin films. All the samples were fabricated by deposition of newly developed sol on conventional glass substrate via spin coating method and were further heat treated at various patterns. In sol variable, increasing the molar ratio of triethylamine to Zn increases preferred orientation along c-axis without using special heat treatment pattern. Various heat treatment parameters including drying and calcination are studied. The results demonstrate that drying at 300 °C is essential for achieving highly preferred ZnO thin film. In addition, calcination time, temperature, and repetition leads to more preferred sample to some extent. Furthermore, increasing the drying time at 300 °C causes significant increase of c-axis orientation and extremely preferential growth. In general, selection of an appropriate heat treatment pattern together with an accurate sol composition is necessary to achieve extremely preferred ZnO thin film with less energy conservation without using any special substrate. This is noteworthy that all the ZnO thin films are highly transparent in visible region and their band gap was around 3.3 eV.

P‐69: Light Absorbing Dye‐Doped Siloxane Based Optical Filter Film for Image and IR Sensors

As a demand for thin & flexible optical sensors has increased, conventional glass substrates based optical filters needs to be replaced by flexible film based optical filters. In this paper, light absorbing dye‐doped siloxane based optical film filters are introduced for replacing conventional glass based optical filters. Light absorbing dye‐doped siloxane hybrid optical film filters have good light filtering ability in diverse wavelength ranges with high transmittance in desired wavelengths, showing high thermal and optical stability.

Ultrathin, lightweight and flexible organic light-emitting devices with a high light outcoupling efficiency

Abstract High-efficiency, flexible organic light-emitting diodes (OLEDs) are of interest for display and lighting applications. However, they often suffer from inefficient light extraction, and many outcoupling schemes are incompatible with flexible OLEDs. Here, we demonstrate a corrugated, ultrathin (10 μm), light-weight (20 g/m2), and flexible OLED on a polychloro-p-xylylene (parylene) substrate. A visible-wavelength-scale random corrugation pattern is imprinted on both surfaces of the parylene substrate that efficiently outcouples trapped substrate, waveguide and surface plasmon modes. A green phosphorescent OLED fabricated on a corrugated parylene substrate (CP-OLED) has an external quantum efficiency of 28 ± 2% compared with 21 ± 1% for devices on a conventional flat glass substrate. The CP-OLED shows a Lambertian intensity profile whose spectra are unchanged at different viewing angles. The very thin and flexible substrates offer a solution for foldable displays over very small radii for use in mobile devices and medical applications.

Transparent energy-saving glass with high resistance to solar heat

We design and fabricate a planar energy-saving glass with high transmission of visible light and a high resistance to infrared solar heat. The proposed glass is designed by combining a photonic crystal structure made of alternating low- and high-index dielectrics and a dielectric/metal/dielectric multilayers deposited on conventional glass substrates. After delicate optimizations, a high weight-averaged transmission of infrared solar energy (17%) and low transmission of ultraviolet light (14%) is obtained while retaining over 83% transmission of visible light. As a result, we achieve a high energy-saving efficiency of 83%, which is about 30% higher than that of uncoated glass. The proposed nanofabrication-free energy-saving design is expected to have promising applications in reducing energy consumption of buildings, cars, etc.

Ion-flux characteristics during low-temperature (300 °C) deposition of thermochromic VO2 films using controlled reactive HiPIMS

The ion-flux characteristics at a substrate position and the corresponding discharge characteristics were investigated during controlled low-temperature (300 °C) reactive high-power impulse magnetron sputtering (HiPIMS) depositions of thermochromic VO2 films onto conventional soda-lime glass substrates without any substrate bias voltage and without any interlayer. It was shown that the phase composition of the films correlates with the (V+ + V2+) ion fraction and the (V+ + V2+):() ion ratio in the total ion flux onto the substrate. Setting the amount of oxygen in the gas mixture allowed us to control not only the phase composition of the films but also their crystallinity. It was found that an appropriate composition of the total ion flux and high ion energies (up to 50 eV relative to ground potential) support the crystallization of the thermochromic phase in the VO2 films. We achieved a high modulation of the transmittance at 2500 nm (between 51% and 8%) and of the electrical resistivity (changed 350 times) for a 88 nm thick VO2 film.

Growth of graphene/Ag nanowire/graphene sandwich films for transparent touch-sensitive electrodes

Abstract In this paper, a novel graphene/Ag nanowires/graphene (G/Ag NWs/G) sandwich film was directly grown on a conventional glass substrate by use of a technique of low temperature (600 °C) plasma-enhanced chemical vapor deposition (PECVD) combined with solvothermal and modified Hummers methods. The as-grown G/Ag NWs/G/glass sandwich film is uniform, smooth, touchable, transparent and conductive with an optical transmission 77.6% and a low sheet resistance ∼10.8 Ω/sq. The top graphene layer exhibits an effective role for improving the touchable and antioxidant properties of Ag NWs, while the bottom graphene layer enhances the binding stability of Ag NWs with substrate. The sheets resistance of G/Ag NWs/G/glass film exposed to the air for 72 h at 95 °C increases from 10.8Ω/sq to 14.6Ω/sq. These indicate a great promising in replacing the expensive and fragile indium tin oxide (ITO) glass and ITO film for touchable transparent electrode applications.

Tailoring far-infrared surface plasmon polaritons of a single-layer graphene using plasmon-phonon hybridization in graphene-LiF heterostructures

Being one-atom thick and tunable simultaneously, graphene plays the revolutionizing role in many areas. The focus of this paper is to investigate the modal characteristics of surface waves in structures with graphene in the far-infrared (far-IR) region. We discuss the effects exerted by substrate permittivity on propagation and localization characteristics of surface-plasmon-polaritons (SPPs) in single-layer graphene and theoretically investigate characteristics of the hybridized surface-phonon-plasmon-polaritons (SPPPs) in graphene/LiF/glass heterostructures. First, it is shown how high permittivity of substrate may improve characteristics of graphene SPPs. Next, the possibility of optimization for surface-phonon-polaritons (SPhPs) in waveguides based on LiF, a polar dielectric with a wide polaritonic gap (Reststrahlen band) and a wide range of permittivity variation, is demonstrated. Combining graphene and LiF in one heterostructure allows to keep the advantages of both, yielding tunable hybridized SPPPs which can be either forwardly or backwardly propagating. Owing to high permittivity of LiF below the gap, an almost 3.2-fold enhancement in the figure of merit (FoM), ratio of normalized propagation length to localization length of the modes, can be obtained for SPPPs at 5–9 THz, as compared with SPPs of graphene on conventional glass substrate. The enhancement is efficiently tunable by varying the chemical potential of graphene. SPPPs with characteristics which strongly differ inside and around the polaritonic gap are found.

Improved performance of thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering: Prediction and experimental verification

The paper deals with thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering on conventional soda-lime glass substrates without any substrate bias and without any interlayer. Thermochromic VO2 layers were deposited using reactive high-power impulse magnetron sputtering with a pulsed O2 flow control at a substrate surface temperature of 300 °C. Antireflection SiO2 layers were deposited using mid-frequency bipolar dual magnetron sputtering onto the top of VO2 layers at a surface temperature below 35 °C in order to improve the optical and mechanical performance. We focus on the dependence of the luminous transmittance (Tlum) and the modulation of the solar transmittance (ΔTsol) on the SiO2 layer thickness. The measured dependencies are in good agreement with those predicted using properties of pure VO2 layers measured by spectroscopic ellipsometry. Two different VO2 layer thicknesses (30 and 88 nm) have been used to demonstrate the tradeoff between Tlum and ΔTsol. We show an improvement due to the SiO2 overlayer of up to 16% (from 40.3% to 56.3%) for Tlum measured at 25 °C and up to 2.6% (from 7.7% to 10.3%) for ΔTsol. The results are important for the design and low-temperature fabrication of high-performance durable thermochromic VO2-based coatings for smart window applications.

A plastic holographic waveguide combiner for light‐weight and highly‐transparent augmented reality glasses

AbstractThere is a high demand for light‐weight, stylishly designed augmented reality (AR) glasses with natural see‐through capabilities for the wide‐spread distribution of novel wearable device to general consumers. We have successfully developed a unique production process of a holographic waveguide combiner that enables us to laminate holographic optical elements (HOEs) onto a plastic substrate with optical grade quality. The plastic substrate waveguide combiner has a number of advantages over conventional glass substrate combiners; the plastic substrate makes AR glasses lighter in weight and unbreakable. With the lamination process of HOEs, we can apply them to a various designs to satisfy general customers' wide range of preferences for the style. We also potentially made it possible for the holographic waveguide combiner to be produced in larger volumes at lower costs by using our novel roll‐to‐roll hologram recording and laminating process. In this paper, we present our approach of the plastic substrate HOE production process for AR glasses.

Organic light-emitting diode lighting with high out-coupling and reliability: Application of transparent amorphous ZnO–SiO2 semiconductor thick film

Abstract We report that combination of high refractive index scattering layer made of glass and very thick amorphous ZnO-SiO2 (a-ZSO) semiconductor film is a route for obtaining both high out-coupling and reliability. a-ZSO is a promising material for electron injection/transport layer (EIL/ETL) in OLEDs; it has exceptionally small work function of ∼3.5 eV and high electron mobility of ∼1cm2/(Vs) (conductivity = 3.4 × 10−4 Scm−1), and can form ohmic contact with ITO. Thus, very thick a-ZSO film is applicable for EIL/ETL with no increase in turn-on voltage. Furthermore, a-ZSO has high transparency in the visible light region and a good index matching with the high index scattering layer, which is the most critical criterion to keep high out-coupling efficiency. Consequently, we succeeded in fabricating very stable and efficient OLED using 245 nm thick a-ZSO with the scattering layer which indicates ∼1.7 times higher out-coupling efficiency and smaller leakage current than the OLED with conventional glass substrate and a-ZSO thin film. This technology will be efficient for practical OLED lighting, and the durability against short circuit is also expected to improve.

Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO2 films with semiconductor-to-metal transition

Reactive high-power impulse magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputtered vanadium target was used for low-temperature (300 °C) deposition of VO2 films with a pronounced semiconductor-to-metal transition onto conventional soda-lime glass substrates without any substrate bias voltage and without any interlayer. The depositions were performed using an unbalanced magnetron with a planar target of 50.8 mm diameter in argon–oxygen gas mixtures at the argon pressure of 1 Pa. The deposition-averaged target power density was close to 13 W cm−2 at a fixed duty cycle of 1% with a peak target power density up to 5 kW cm−2 during voltage pulses ranged from 40 µs to 100 µs. A high modulation of the transmittance at 2500 nm (between 51% and 8% at the film thickness of 88 nm) and the electrical resistivity (changed 350 times) at the transition temperature of 56–57 °C was achieved for the VO2 films synthesized using 50 µs voltage pulses when the crystallization of the thermochromic VO2(M1) phase was supported by the high-energy (up to 50 eV relative to ground potential) ions. Principles of this effective low-temperature deposition technique with a high application potential are presented.