Glass Substrates For Applications Research Articles

State-of-the-Art Materials Used in MEMS Micromirror Arrays for Photonic Applications

This work provides an overview on micromirror arrays based on different material systems such as dielectrics, element silicon, compound semiconductors, metals, and novel 2D materials. The goal is to work out the particular strength of each material system to enable optimum performance for various applications. In particular, this review is intended to draw attention to the fact that MEMS micro-mirrors can be successful in many other material systems besides silicon. In particular, the review is intended to draw attention to two material systems that have so far been used less for MEMS micromirror arrays, that have been less researched, and of which fewer applications have been reported to date: metallic heterostructures and 2D materials. However, the main focus is on metallic MEMS micromirror arrays on glass substrates for applications like personalized light steering in buildings via active windows, energy management, active laser safety goggles, interference microscopy, and endoscopy. Finally, the different micromirror arrays are compared with respect to fabrication challenges, switching speed, number of mirrors, mirror dimensions, array sizes, miniaturization potential for individual mirrors, reliability, lifetime, and hinge methodology.

Effect of different thermo-treatment at relatively low temperatures on the properties of indium‑tin-oxide thin films

Pulsed DC magnetron sputtering was used to deposit indium‑tin-oxide (ITO) thin films on glass substrates for application in photovoltaic devices as the final window layer. The evolution of crystal phase, morphology, resistivity and transmittance of the ITO films under different thermal annealing procedure (in-situ annealing versus post-annealing) at relatively low temperatures (up to 300°C) were studied. Fully crystalline ITO films with low sheet resistance of 24Ω/□ and high average transmittance (exclude glass substrate) of 90.10% with a Haacke's figure of merit 1.47×10−2Ω−1 were obtained by in-situ annealing at 200°C. In comparison, the minimum temperature observed to fully crystalize the ITO thin films with competitive crystallinity, electrical and optical properties by post-annealing was 250°C. The corresponding post-annealed 300nm thick films showed sheet resistance of 49Ω/□ and average transmittance (exclude glass substrate) as high as 91.93% with a Haacke's figure of merit 0.882×10−2Ω−1. The surface morphology of the as-deposited ITO films remained homogeneous after post-annealing whereas large particles (up to 100nm) were observed on the surface of the films deposited by in-situ annealing. The results indicated that different thermal treatment procedures at lower temperatures produce significant effect on the electrical, optical and other physical properties of the ITO thin films which are critical for the window layer in photovoltaics.

Improving the gas barrier and mechanical properties of a-SiO x films synthesized at low temperature by using high energy and hydrogen flow rate control

Silicon-oxide thin films were deposited on polyethylene-terephthalate (PET) and glass substrates for applications in transparent barrier packaging and replacement display cover glasses by using plasma-enhanced chemical vapor deposition (PECVD). The bias conditions and the input power in the radio-frequency plasma were changed to optimize the gas barrier and the mechanical properties of the silicon-oxide thin film. We made an advanced plasma source for large-area PECVD (370 × 470 mm2 size). The dissociation of the octamethylycyclodisiloxane (OMCTS) precursor was controlled by using the plasma processing parameters. The gas barrier and the mechanical properties of the a-SiOx film were improved by controlling the plasma process parameters. The gas barrier and the mechanical properties of the coatings were examined using a Permatran (MOCON) system and a pencil hardness measurement. The chemical structure properties of the coatings were examined by using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The properties of the a-SiOx thin films were improved by the dissociation of OMCTS obtained by using various appropriate plasma processing parameters.

Fabrication of Light-Scattering Multiscale Textures by Nanoimprinting for the Application to Thin-Film Silicon Solar Cells

In this study, nanoimprint processing was used to realize various multiscale textures on glass substrates for application in thin-film photovoltaic devices. The multiscale textures are formed by a combination of large and small features, which proofed to be beneficial for light trapping in silicon thin-film solar cells. Two approaches for the fabrication of multiscale textures are presented in this study. In the first approach, the multiscale texture is realized at the lacquer/transparent conductive oxide (TCO) interface, and in the second approach, the multiscale texture is realized at the TCO/Si interface. Various types of multiscale textures were fabricated and tested in microcrystalline thin-film silicon solar cells in p-i-n configuration to identify the optimal texture for the light management. It was found that the best light-scattering multiscale texture was realized using an imprint-textured glass substrate, which contains large craters, in combination with HF-etched TCO (ZnO:Al), which contains small features, on top of the imprint. With this structure (of the second approach), the short-circuit current density of the solar cell devices was improved by 0.6 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> using multiscale textures realized by nanoimprint processing.

Structural and optical properties of electron-beam-evaporated ZnSe 1−x Te x Ternary compounds with various Te contents

ZnSe1−xTex films with different tellurium (Te) contents were deposited by using an electron beam (EB) evaporation technique onto glass substrates for applications to optoelectronic devices. The structural and the optical properties of the ZnSe1−xTex films were studied in the present work. The host material ZnSe1−xTex, were prepared by using the physical vapor deposition method of the electron beam evaporation technique (PVD: EBE) under a pressure of 1 × 10−5 mbar. The X-ray diffractogram indicated that these alloy films had cubic structure with a strong preferential orientation of the crystallites along the (1 1 1) direction. The optical properties showed that the band gap (Eg) values varied from 2.73 to 2.41 eV as the tellurium content varied from 0.2 to 0.8. Thus the material properties can be altered and excellently controlled by controlling the system composition x.

Hybrid structure of graphene sheets/ZnO nanorods for enhancing electron field emission properties

A hybrid structure of graphene sheets (GSs)/ZnO nanorods (ZNRs) is developed on glass substrates for applications in field emission (FE) cathodes. ZNRs are grown on glass substrates by a combination of sputtering and hydrothermal processes. Graphene films are synthesized on the Cu foils by the thermal chemical vapor deposition technique, and are transferred onto the ZNRs with various cycles (one, two, and three times) to form GS/ZNR hybrids with different morphology. FESEM, XRD, and Raman spectroscopy are used to analyze the surface morphology, crystallinity, and chemical composition, respectively. It is found that the FE properties of all GS/ZNR cathodes possess a lower turn-on electric field and higher current density than pristine ZNR cathode owing to the presence of the GS. The GSs/ZNRs with two transferred cycle exhibit the lowest turn-on electric field (3.7V/μm, 1μA/cm2) and highest enhancement factor β (8723). These superior properties indicate that the GS/ZNR hybrids are promising field cathodes in FE applications.

Bilayer Structure of ZnO Nanorod/Nanodiamond Film Based Ultraviolet Photodetectors

A novel bilayer structure of ZnO nanorods (ZNRs)/nanodiamond films (NDFs) is developed on glass substrates for applications in ultraviolet (UV) photodetectors (PDs). NDFs are first grown by microwave plasma chemical vapor deposition, and are then deposited with a ZnO seed layer and Au interdigitated electrodes through a combination of sputtering and photolithography to form a metal-semiconductor-metal (MSM) structure. Finally, the ZNRs are hydrothermally synthesized at 90°C for 3 h. FESEM, Raman, XRD and PL spectroscopy are respectively used to analyze the surface morphology, crystallinity and optical properties. These analyzes indicate that the bilayer structure of the ZNRs/NDFs exhibits good crystallinity to enhance the ZNR based PDs. The photoresponse (Iphoto/Idark) behavior of the ZNR/NDF PD exhibits a much higher photoresponse (594.6) than those exhibited by the NDF PD (1.2) and ZNR PD (217.1) at 5 V bias under 365 nm wavelength illumination.

Evolution of microstructure and electrical conductivity of electroless copper deposits on a glass substrate

This paper describes the evolution of the microstructure and conductivity of electroless copper deposition on a glass substrate for applications in electronics manufacture. The glass was activated using a (3-aminopropyl)trimethoxysilane pre-treatment followed by a Pd/Sn catalyst. Surface morphology of the deposited copper films was characterized using a dual beam focused ion beam field emission scanning electron microscope, and together with atomic force microscopy, showed clearly that the roughness and grain size tended to increase with the plating time. Film thickness measurements showed a high initial deposition rate, which slowed to a constant level as the thickness increased above 100nm. This corresponded with the resistivity of the films which decreased rapidly as the thickness increased from 20 to 100nm, but then remained largely stable at a level approximately twice that of bulk copper.

Fabrication and Characterization of Erbium-Doped Fluoropolymer Patterns via UV-Nanoimprint Lithography for Use in Planar Optical Amplifiers

The Er-doped precursor solutions were first prepared using 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as a fluoromonomer, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol diacrylate as a cross-linking agent, poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate) as a binding polymer, Darocure 4265 as radical photoinitiator and erbium(III) trifluoromethane sulfonate as an erbium source with various weight ratios. The crosslinked, patterned and erbium-doped fluoropolymer films were fabricated by UV-nanoimprint lithography on glass substrates for application as planar optical amplifiers. The fluoropolymer films acting as a host material for the Er ions showed excellent transmission properties—more than 80% over the visible and near-infrared regions—a high thermal decomposition temperature greater than 350°C and the ability to support a high Er concentration—up to 10 wt% based on the polymer matrix. These results were good enough for the films to be used in planar optical amplifier applications.

Gravure Printing of Conductive Inks on Glass Substrates for Applications in Printed Electronics

In graphics, gravure printing is the preferred method for printing high quality, fine dimension graphics using high-speed roll-to-roll or sheet fed presses. Gravure printing typically employs flexible and compressible substrates such as various papers and polymer films. In electronics, glass substrates are a common, if not preferred, substrate in many applications, particularly displays and photovoltaics. In combining printing with glass substrates, challenges exist in adapting contact-based printing methods such as gravure to the mechanical properties of the more rigid substrates. In this work, sheet-fed gravure printing has been successfully used to print silver-based conductive inks on glass substrates. Various features were designed and printed to evaluate conductive layers in terms of their printability and electrical performance. The independent variables include gravure cell dimensions, trace orientation with respect to printing direction and ink type. Results from this work provide an insight into the science of gravure printing on glass by correlating the independent variables to printed feature quality and electrical performance.

Characterization of Defects and Stress in Polycrystalline Silicon Thin Films on Glass Substrates by Raman Microscopy

Raman microscopy was applied to characterize polycrystalline silicon (poly‐Si) on glass substrates for application as thin‐film transistors (TFTs) integrated on electronic display panels. This study examines the crystallographic defects and stress in poly‐Si films grown by industrial techniques: solid phase crystallization and excimer laser crystallization (ELC). To distinguish the effects of defects and stress on the optical‐phonon mode of the Si–Si bond, a semiempirical analysis was performed. The analysis was compared with defect images obtained through electron microscopy and atomic force microscopy. It was found that the Raman intensity for the ELC film is remarkably enhanced by the hillocks and ridges located around grain boundaries, which indicates that Raman spectra mainly reflect the situation around grain boundaries. A combination of the hydrogenation of films and the observation of the Si‐hydrogen local‐vibration mode is useful to support the analysis on the defects. Raman microscopy is also effective for detecting the plasma‐induced damage suffered during device processing and characterizing the performance of Si layer in TFTs.

Spectral Response and Photoelectrochemical Properties of Cd1–xZnxSe Films

Cd1–xZnxSe films with different zinc contents are deposited by an electron beam evaporation technique onto glass substrates for applications in solid-state photovoltaic devices. The structural, optical and photoelectrochemical (PEC) properties of Cd1–xZnxSe films are studied. The host material Cd1–xZnxSe is prepared by the physical vapor deposition method of electron beam evaporation technique (PVD: EBE) under a pressure of 1 × 10−5 mbar. The x-ray diffractogram indicates that these alloy films are polycrystalline in nature, hexagonal structure with strong preferential orientation of the crystallites along (002) direction. The optical properties shows that the band gap Eg varies from 2.08 to 2.84 eV as zinc content varies from 0.2 to 0.8. A PEC cell of the configuration n-Cd1–xZnxSe/Na2S-S-NaOH is fabricated and the dynamic current-voltage characteristics in the dark atmosphere have been examined at room temperature. It has been found that both Voc and Isc decrease with the photoelectrode composition x. Efficiency η and fill factor (FF) also show similar variations. The material properties would be altered and excellently controlled by controlling the system composition x.

Effect of Oxygen Concentration on Characteristics of Ba(Zr0.1Ti0.9)O3 Thin Films Deposited on Indium Tin Oxide/Glass Substrates

In this study, the perovskite Ba(Zr0.1Ti0.9)O3 (BZ1T9) ferroelectric thin films deposited on indium tin oxide (ITO)/glass substrates for applications in system-on-panel (SOP) devices are produced and investigated. The optimal sputtering conditions of as-deposited BZ1T9 thin films are an rf power of 160 W, a chamber pressure of 10 mTorr, a substrate temperature of 580 °C, and an oxygen concentration of 40%. The effect of oxygen concentration on the physical and electrical characteristics of BZ1T9 thin films is determined. For different oxygen concentrations, the thickness and deposition rate are calculated by scanning electron microscopy (SEM). From polarization versus electrical field curves, the 2Pr value and coercive field of BZ1T9 thin films are determined to be 7 µC/cm2 and 250 kV/cm, respectively. In addition, the maximum dielectric constant, leakage current density, and transmittance within the ultraviolet–visible (UV–vis) spectrum are investigated.

Thin Film Actinometers for Transient Absorption Spectroscopy: Applications to Dye-Sensitized Solar Cells

The chromophores Ru(bpy)3(PF6)2 and Os(bpy)3(PF6)2 were immobilized within poly(methyl methacrylate) (PMMA) thin films on glass substrates for applications as actinometers for nanosecond flash photolysis. Transient absorption difference spectra of M(bpy)3(PF6)2 (M = Ru, Os), at ambient temperature and in an argon atmosphere, were the same when imbedded in PMMA films as in solution, within experimental error. Linear ranges of ΔA versus 532 nm pulsed laser energy where these actinometers were applicable were identified, up to 25 mJ/(cm2 pulse) for Ru(bpy)32+/PMMA and up to 5 mJ/(cm2 pulse) for Os(bpy)32+/PMMA. Laser energy measurements were used to estimate the difference between the excited- and ground-state extinction coefficients at 450 nm for Os(bpy)32+, Δε450nm, which is −7300 M-1 cm-1. The Ru(bpy)32+/PMMA actinometer was useful from 300 to ∼550 nm, while the Os(bpy)32+/PMMA actinometer extends the sensitivity to ∼700 nm. An application of these actinometers for dye-sensitized solar cells is described, wherein the quantum yield for electron injection from Ru(dcbH2)(bpy)22+*, where dcbH2 is 4,4‘-(CO2H)2-2,2‘-bipyridine, into mesoporous nanocrystalline (anatase) TiO2 thin films was quantified as a function of ionic strength.

Large-grained polycrystalline Si films obtained by selective nucleation and solid phase epitaxy

We investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since the use of glass substrates constrains process temperatures, our chosen approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created for both P-doped, B-doped and undoped, 100 nm thick amorphous silicon films, by masked implantation of In or Ni islands, followed by annealing at temperatures below 600°C. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns. The maximum achievable grain size depends on the product of the SPE rate and the incubation time for the spontaneous nucleation. We have studied the dependence of the SPE rate and the incubation time on the type of metal (In and Ni) inducing the nucleation and on the electronic dopant (e.g. P and B) concentration in the 10 19–10 21 cm −3 range.

Ni-Induced Selective Nucleation and Solid Phase Epitaxy of Large-Grained Poly-Si on Glass

AbstractWe investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since use of glass substrates constrains process temperatures, our approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created on undoped, 75 nm thick, amorphous silicon films, by masked implantation of Ni islands, followed by annealing at temperatures below 600 °. At this temperature, the Ni precipitates into NiSi2 particles that catalyze the transition from the amorphous to the crystalline Si phase. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns in one hour. We have studied the dependence of the crystallization rate on the Ni-implanted dose in the seed, in the 5×1015/cm3 - 1016/cm3range. The large grained polycrystalline Si films were then used as a substrate for molecular beam epitaxy (MBE) depositions of 1 [.proportional]m thick Si layers. Transmission electron microscopy (TEM) analysis showed a strong correlation between the substrate morphology and the deposited layer. The layer presented a large grain morphology, with sizes of about 4 [.proportional]m.