Alkaline Earth Boro-aluminosilicate Glass Research Articles

Structural Aspects of Ambient-Temperature Densification of Highly Crack-Resistant Borosilicate and Aluminoborosilicate Glasses: Two Case Studies Examined by Solid-State NMR.

The structural aspects of ambient-temperature densification via pressurization at 25 GPa were studied by solid-state NMR for two case studies: An alkaline earth boroaluminosilicate glass with the composition 6CaO-3SrO-1BaO-10Al2O3-10B2O3-70SiO2 (labeled SAB) and a sodium magnesium borosilicate glass with the composition 10Na2O-10MgO-20B2O3-60SiO2 (labeled MNBS). For SAB glass, cold pressurization results in significant increases in the average coordination numbers of both boron and aluminum, in line with previous results found in hot-compressed alkali aluminoborosilicate glasses. In addition, 27Al/11B dipolar recoupling experiments reveal a significant decrease in the 11B/27Al dipolar interaction strength upon pressurization, suggesting that the higher-coordinated boron and aluminum species experience weaker magnetic interactions. While this is an expected consequence of the longer internuclear distances involving higher coordination states, the magnitude of the effect also is consistent with a decrease of average B-O-Al internuclear connectivity. By conjecture, a decreased B-O-Al connectivity may present a mechanism of plastic flow inhibiting crack initiation in aluminoborosilicate glasses. In the case of the MNBS glass, no change in the average boron coordination number was observed within experimental error; however, densification increases the extent of B-O-Si connectivity at the expense of small ring structures with dominant B-O-B connectivity. With regard to boron coordination, the data obtained for both case studies differ from those previously found in a series of alkali borosilicate glasses, which had shown an unexpected decrease in N4 upon increased pressure. The results of the present study highlight the importance of changes of medium-range order regarding densification.

Intrinsic properties of multi-component glass surfaces exposed to aqueous hydrofluoric (HF) and/or hydrochloric (HCl) acid-based treatments

Acids have been used to treat glass surfaces to achieve functional advantage for years. Despite how common these types of treatments are, it is surprisingly rare to find detailed studies that examine the potentially subtle changes to glass surface properties arising from different types of chemical exposures immediately following treatment. Here, we report on the intrinsic surface properties of an alkaline-earth boroaluminosilicate glass immediately following exposure to either (1) aqueous solutions of hydrofluoric acid (HF) with varied concentrations, or (2) mixtures of HF with hydrochloric acid (HCl) in variable concentration/component ratio(s). Surface properties investigated include surface free energy, zeta potential, shallow surface composition profiles using time of flight – secondary ion mass spectroscopy and nanoscale topography via atomic force microscopy. Activation energy calculations were used to investigate the energetics of dissolution as functions of treatment chemistry, where values of approximately ∼25–35 kJ/mol were observed across most of the ranges studied. Results suggest that the properties at the topmost surface of the treated glasses are highly dependent on the type and strength of formulation used, even when the same amount of glass is dissolved. In some cases, observed trends in the data appear to be directly related to perceived shifts in the dominant reaction mechanisms between the etchant and glass that are dictated by treatment chemistry.

Inscription of surface waveguides in glass by femtosecond laser writing for enhanced evanescent wave overlap

Near-surface optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass (Eagle2000), by femtosecond laser direct writing, using two distinct approaches. First, the capability of directly inscribing optical waveguides close to the surface was tested, and then, compared to the adoption of post writing wet etching to bring to the surface waveguides inscribed at greater depths. Laser ablation was found to limit the minimum surface to core center distance to 6.5 µm in the first method, with anisotropic wet etching limiting the latter to 3 µm without any surface deformation; smaller separations can be achieved at the cost of the planar surface topography. Furthermore, the waveguide’s cross-section was seen to vary for laser inscription nearing the surface, observations that were also corroborated by its distinct guiding characteristics when compared to the adoption of post writing wet etching. The spectral analysis (in the 500–1700 nm range) also evidenced an increase in insertion loss for longer wavelengths and smaller surface to core center separations, caused, most likely, by coupling loss due to the interaction between the propagating mode and the surface. Different lengths of waveguide exposed to the surface were also tested, revealing that scattering loss due to surface roughness is not an issue at the centimeter scale.

Mass Producible Low-Loss Broadband Optical Waveguides in Eagle2000 by Femtosecond Laser Writing

Optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass, by femtosecond laser direct writing, with varying pulse energy and scan velocity. A spectral characterization, from 500 nm to 1700 nm, was made in order to determine their losses and understand its dependence on the processing parameters. Three major loss mechanisms were identified. At longer wavelengths, loss is mainly due to weak coupling. On the other hand, the behavior at shorter wavelengths is governed by propagation loss due to Rayleigh scattering, which was shown to be practically eliminated ( $\cdot$ cm $^{-1} {\cdot }\,\,\mu \text{m}^{4}$ ) at higher scan velocities. Bulk absorption was also found to have an influence in the propagation losses at higher wavelengths. The combination of intermediate pulse energies (between 125–250 nJ) and high scan velocities (above 6 cm/s) allowed the fabrication of optical waveguides offering low losses across the entire range of wavelengths tested, facilitating applications that require larger wavelength working bands. Furthermore, since optimal fabrication conditions are achieved at higher scanning velocities, mass production with reduced fabrication times can be achieved.

Jig-free laser welding of Eagle XG glasses by using a picosecond pulsed laser

We have performed the jig-free laser welding on the alkaline earth boro-aluminosilicate glass (Eagle XG, Corning), which is commonly used in the display devices, by using a picosecond pulsed laser. Two sheets of Eagle XG glasses with 0.5 mm thickness each were placed one on top of the other. Due to the jig-free laser welding, there was a very thin air gap between the two glasses, and the experiment proceeded by line scanning. The welding performance was evaluated by observing the optical images from the top view and the bottom view and comparing the line images. We could bond the two glass surfaces on the laser spot, and achieve the successful welding of such glasses in the scanning speeds from 10 mm/s to 50 mm/s with the laser irradiance from 50 TW/cm2(500 J/cm2) to 83 TW/cm2 (830 J/cm2). We demonstrated the feasibility of jig-free laser welding on the Eagle XG glass with the welding strength up to 50 MPa.

Surface characteristics of alkaline earth boro-aluminosilicate glass following single picosecond laser pulse exposure at different focal positions

We investigated the surface characteristics of alkaline earth boro-aluminosilicate glass (EAGLE XG, Coring), which is used in display applications, irradiated by a high power picosecond (ps, 10−12 s) pulsed laser beam while varying the position of focal position in and out of the top and bottom surfaces of the glass and the irradiation fluence of laser beam. Upon the single shot exposure of a 10 ps pulsed laser at the wavelength of 1064 nm, we found that laser processing of this type of glass is possible only near the surfaces above the certain threshold fluence high enough to cause enough multiphoton absorption. The processing threshold values were found to be 11 ± 2 and 7.1 ± 1.4 J/cm2 for 3.0 and 5.0 μJ excitation pulse energies corresponding to the intensities of 3.3 × 1012 and 5.5 × 1012 W/cm2, respectively. The morphological changes on the surfaces due to a single shot laser processing occurred until the focal position moved away from the surfaces about 10 μm outside of the glass at 3.0 μJ of pulse energy, which is longer than Rayleigh length. The distance that focal position moved inside of the glass to provide enough nonlinear absorption for laser processing on the surface increased several times compared to the cases of focal position moved outside. The distance also increased with increasing the pulse energy to 5.0 μJ. It was also found that the top surface was processed mainly by ablation with no significant melting at this fluence range and the bottom surfaces suffered considerable thermal damage such as melting and resolidification while no processing occurred deep inside of the glass further away from both the top and the bottom surfaces as the focal position moved from the top to the bottom surfaces. We expect that most of absorption occurs near the surface when the focal position is near the top surface while more absorption occurs inside of glass before the laser beam reaches the bottom surface when the focal position is near the bottom surface. Our single shot exposure results inspire some important insights on application of laser processing by ps pulses on glass type materials.

Proton irradiation induced changes in glass and polyethylene terephthalate substrates for photovoltaic solar cells

An alkaline earth boro-aluminosilicate glass (Eagle XG), a soda-lime glass, and a light-weight polyethylene-terephthalate (PET) foil, used as typical substrates for photovoltaics, were treated by an energetic proton beam (3 MeV, dose 106–107 Gy) corresponding to approx. 30 years of operation at low Earth orbit. Properties of the irradiated substrates were characterized by atomic force microscopy, optical absorption, optical diffuse reflectance, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and terahertz (THz) spectroscopy. Minimal changes of optical and morphological properties are detected on the bare Eagle XG glass, whereas the bare PET foil exhibits pronounced increase in optical absorption, generation of photoluminescence, as well as mechanical bending. On the other hand, the identical substrates coated with Indium-tin-oxide (ITO), which is a typical material for transparent electrodes in photovoltaics, exhibit significantly higher resistance to the modifications by protons while ITO structural and electronic properties remain unchanged. The experimental results are discussed considering a potential application of these materials for missions in space.

Femtosecond laser direct-writing of waveguide Bragg gratings in a quasi cumulative heating regime

Waveguide Bragg gratings (WBGs) were directly inscribed into Alkaline Earth Boro-Aluminosilicate glass samples in a single process step at high fabrication speeds. We utilized a 5.1 MHz femtosecond oscillator to exploit high repetition rate heat accumulation effects. The pulse energy was modulated using a Pockels cell in order to fabricate waveguides that contain a periodic array of nano-structures inside their core. We have demonstrated, for the first time, that the transient build-up of heat accumulation within the sample can lead to the formation of a permanent nano-void. This effect can be exploited to fabricate WBGs at high speeds.

Stimulated Emission in Highly (0001)-Oriented ZnO Films Grown by Atomic Layer Deposition on the Amorphous Glass Substrates

Highly oriented zinc oxide (ZnO) films accompanied by stimulated emission have been fabricated on amorphous alkaline earth boro-aluminosilicate glass substrates by atomic layer deposition (ALD). By introducing a buffer layer which was deposited at a high temperature of and followed by postdeposition rapid thermal annealing at , ZnO films with the (0001) preferred orientation could be grown by ALD upon the buffer layer at a low temperature of . Photoluminescence exhibited a dominant near-band-edge spontaneous emission at 380 nm and a negligible defect-related band. Optically pumped stimulated emission around 395 nm with a threshold intensity of was observed at room temperature, which is ascribed to the good optical and crystal quality of the ZnO films grown by the ALD technique on the amorphous glass substrates.

Incorporation of water into glasses and its influence on the diffusion of cations, including the creation of diffusion barriers

When heated to elevated temperatures, many glasses take up water from moisture-containing environments. This leads not only to changes in local water concentrations, but also to non-uniform structural changes within the glass. These structural changes impact many structure-sensitive properties, including the diffusivity of ions. Experimental data for the uptake of water by a Type I silica glass, Infrasil 302, and by an alkaline-earth boroaluminosilicate glass, Corning Code 1737, are discussed as well as the influence of the incorporation of water into these glasses on the diffusion of sodium. Furthermore, the modification of glass near the surface by the uptake of water, leading in the case of the alkaline-earth boroaluminosilicate glass to the creation of a very effective barrier layer against the diffusion of sodium, is addressed.

Radiation-Induced Surface Conductivity in an Alkaline-Earth Boroaluminosilicate Glass Measured with Elevated-Temperature Scanning Probe Microscopy

A 50 mW 325 nm He:Cd laser was used to irradiate the fracture surface of a commercial alkaline-earth boroaluminosilicate display glass (Corning Code 1737) held at temperatures above 800 K. After this treatment, the surface of the glass was found to be conductive for several hours in a temperature range between room temperature and 850 K. The conductivity shows an activation energy of 0.18 eV. Scanning tunneling spectroscopy measurements indicate that the glass surface is semiconducting with a bandgap of ∼4.4 eV. It is possible to form topographical images of the surface of the glass using the electron tunneling current; the observed topography corresponds to that acquired using atomic force imaging from the same area.

Effect of water incorporation on the diffusion of sodium in an alkaline-earth boroaluminosilicate glass

Tracer diffusion coefficients of sodium ions diffusing in an alkaline-earth boroaluminosilicate glass (Corning Code 1737 glass) were measured by using Na-22 as a radioactive tracer. It was found that the presence of a significant amount of water vapor in the atmosphere surrounding a diffusion sample during diffusion annealing reduces considerably the mobility of sodium in the near-surface region of the glass. This partial immobilization of Na is attributed to an interaction between water dissolved into the glass and diffusing sodium ions.

Sodium tracer diffusion in an alkaline-earth boroaluminosilicate glass

Sodium tracer diffusion coefficients, D ∗ Na , have been measured in an alkaline-earth boroaluminosilicate glass in the temperature range 500–800°C by using the radioactive isotope Na-22. It was found that the activation energy of the sodium tracer diffusion changes near the strain point (666°C). Therefore, two Arrhenius-type functions are needed to describe the temperature dependence of D ∗ Na in this temperature range. Below 664°C, D ∗ Na =10 (−2.21±0.07) exp (−(129.9±1.2 kJ/mol)/RT) cm 2/ s and above 664 ∘C, D ∗ Na =10 (−0.23±0.15) exp (−(165.5±3.0 kJ/mol)/RT) cm 2/ s .

Effect of RCA cleaning on the surface chemistry of glass and polysilicon films as studied by ToF-SIMS and XPS

The surface chemistry of an alkaline-earth boroaluminosilicate glass is changed by contact with chemical solutions. The present study shows that RCA cleaning creates a silica-rich surface on the glass. This altered surface can be removed by hydrofluoric acid etching. During the RCA cleaning process, glass components can be transferred to a polysilicon film placed in the same alkaline solution. The acidic solution in turn removes most of the contamination from the polysilicon. © 1998 John Wiley & Sons, Ltd.

Alumina barrier layers on LCD glass

Abstract Effective diffusion coefficients, D e , for the movement of sodium from an LCD glass into a sputtered alumina barrier layer have been determined. Secondary ion mass spectrometry analysis was used to measure sodium concentrations in 100 nm thick alumina films on soda lime glass at 520°C and for similar films on alkaline earth boroaluminosilicate glass at 650°C. Calculated values of D e are compared with extrapolated values of the diffusion coefficient, D , for sodium in polycrystalline alumina. The agreement is inconsistent. This is explained in terms of the countercurrent of hydrogen ions needed to maintain charge neutrality when a sodium ion moves out of the glass into the alumina film.