Glass-ceramic Thin Films Research Articles

Improving Solar Cell Performance with High-Efficiency Infrared Quantum Cutting in Tb3+−Yb3+ Codoped Silica Hafnia Glass and Glass-Ceramic Thin Films

An efficient quantum cutting mechanism was observed in a system comprising Tb3+−Yb3+ codoped silica hafnia glass and glass-ceramic. Thin films were deposited on silicon substrates using the dip-coating method and photoluminescence dynamics revealed a quantum efficiency of up to 179% at 980 nm. These films can efficiently convert light to lower energy levels and can easily be integrated into silicon-based solar cells, increasing their photoelectric conversion efficiency at a low cost. This was demonstrated through electrical characterization, which revealed a boost in solar cell efficiency when the film was utilized. It was specifically noted that the efficiency of Si solar cells increased by 10.79% and 10.78% when covered with 70SiO2−30HfO2−3Tb3+−12Yb3+ glass and glass ceramic, respectively. Furthermore, an evaluation of the additional external quantum efficiency, derived from this optical system, revealed an improvement ranging from 2.64% to 3.44%. This finding highlights the enhanced light conversion capabilities of the quantum cutting mechanism within the system.

Nonlinear Optical Glass-Ceramic From a New Polar Phase-Transition Organic-Inorganic Hybrid Crystal.

Melt-quenched glasses of organic-inorganic hybrid crystals, i.e., hybrid glasses, have attracted increasing attention as an emerging class of hybrid materials with beneficial processability and formability in the past years. Herein, we present a new hybrid crystal, (Ph3 PEt)3 [Ni(NCS)5 ] (1, Ph3 PEt+ =ethyl(triphenyl)phosphonium), crystallizing in a polar space group P1 and exhibiting thermal-induced reversible crystal-liquid-glass-crystal transitions with relatively low melting temperature of 132 °C, glass-transition temperature of 40 °C, and recrystallization on-set temperature of 78 °C, respectively. Taking advantage of such mild conditions, we fabricated an unprecedented hybrid glass-ceramic thin film, i.e., a thin glass uniformly embedding inner polar micro-crystals, which exhibits a much enhanced intrinsic second-order nonlinear optical effect, being ca. 25.6 and 3.1 times those of poly-crystalline 1 and KH2 PO4 , respectively, without any poling treatments.

Optical properties of [formula omitted] co-doped silica-hafnia glass and glass-ceramic thin film

In this paper, optical properties of Tb3+/Yb3+ co-doped 70SiO2 - 30HfO2 glass and glass-ceramic thin films prepared by dip coating on Si O2 substrate are investigated using transmittance measurements. Such systems are usually used for down-converting the high-frequency sunlight in order to tune the solar spectrum into the bandgap of the semi-conductor based photovoltaic system. The interference modulated transmission spectra τ(λ) of 70SiO2 - 30HfO2- x Tb3+−y Yb3+ (with molar ratio x/y = 1.8/0, 1.8/7.2, 3/12) at normal incidence were recorded in the spectral wavelength region from 250 nm up to 2500 nm. The corresponding optical constants and thicknesses were deduced by analyzing the transmittance spectra using the straightforward method proposed by Swanepoel. The dispersion of the real part of the refractive index and the absorption were then deduced. The results show thatthe increase in the concentration of rare earth ions leads to a slight increase in the refractive index, this is also observed in thickness variation.Furthermore, the energy bandgap has been determined from the absorption coefficient values using the direct transition model proposed by Tauc. The corresponding value is around 3 eV with a slightly higher bandgap for glass films as compared to glass-ceramic films.

Substituted Hydroxyapatite, Glass, and Glass-Ceramic Thin Films Deposited by Nanosecond Pulsed Laser Deposition (PLD) for Biomedical Applications: A Systematic Review

The deposition of thin films of bioactive materials is the most common approach to improve the bone bonding ability of an implant surface. With this purpose, several wet and plasma assisted deposition methods were proposed in the scientific literature. In this review, we considered films obtained by nanosecond Pulsed Laser Deposition (PLD). Since hydroxyapatite (HA) has composition and structure similar to that of the mineral component of the bone, the initial studies focused on the selection of experimental conditions that would allow the deposition of films that retain HA stoichiometry and crystallinity. However, biological apatite was found to be a poorly crystalline and multi-substituted mineral; consequently, the attention of researchers was oriented towards the deposition of substituted HA, glass (BG), and glass-ceramic (BGC) bioactive materials to exploit the biological relevance of foreign ions and crystallinity. In this work, after a description of the nanosecond ablation and film growth of ceramic materials, we reported studies on the mechanism of HA ablation and deposition, evidencing the peculiarities of PLD. The literature concerning the PLD of ion substituted HA, BG, and BGC was then reviewed and the performances of the coatings were discussed. We concluded by describing the advantages, limitations, and perspectives of PLD for biomedical applications.

Synthesis and characterization of hydrophobic glass-ceramic thin film derived from colloidal silica, zirconium(IV) propoxide and methyltrimethoxysilane via sol–gel method

This study focuses on the synthesis and characterization of Zirconium(IV) Propoxide (ZTP), Colloidal Silica (CS), and Methyltrimethoxysilane (MTMS)-derived non-stick hard coatings prepared via the sol–gel method. In the synthetic procedure, two different solutions were prepared separately based on the different hydrolysis rates of the silicon (SolS) and zirconium (SolZ) components. Polydimethoxysilane (PDMS) and Fluoralkylsilane (FAS) were used as hydrophobicity-promoting agents. The solution was applied onto aluminum surface, which was afterward dried and densified at 250 °C. The final solution was characterized by FTIR spectroscopy to determine the Zr–O–Si hetero-bonding and Si–O–Si and Zr–O–Zr homo-bonding. Coatings were analyzed by their hardness, hydrophobicity, and gloss. A homogeneous solution and crack-free hybrid coating was obtained. FTIR results showed that homo- and hetero-bonding between Zr and Si elements were obtained from a precipitation-free solution. Measured contact angles varied between 100° and 112°, and these results were evaluated according to the surface and gel structure.

Optical and Structural Properties of Er3+-doped SiO2-ZrO2 Glass-Ceramic Thin Film

The Er3+-activate dielectric thin film can be applied to produce planar waveguide amplifiers that can be integrated with other active or passive devices on the same chip. However, Er3+ tend to cluster in host material especially in silica when doped at high concentration. This issue can be overcome by introducing Z1O2 as a co-host material in a silica glass matrix by helping to disperse Er3+ homogeneously and consequently enhance the output intensity. In this work, we present a study on 70SiO2-30ZrO2 glass ceramic doped with a various concentration of Er3+ prepared by the sol-gel dip coating technique and each film obtained were annealed at 900°C. Full film densification was achieved for the deposited film, which indicates the hydroxyl group was successfully removed as shown in Raman spectra. Refractive index of the film increase with the increment of rare earth ion and this permit the guiding of light in the film. Red and green emissions of Er3+ were detected upon 514.5 nm excitation. Nevertheless, the presence of higher Er3+ (0.58 mol%) induces concentration quenching phenomena as shown in the PL spectra where there is a decline in green emission peak.

Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

Chalcogenide glass-ceramic with self-organized heterojunctions: application to photovoltaic solar cells

In this work, we present for the first time the concept of chalcogenide glass-ceramic for photovoltaic applications with the GeSe2–Sb2Se3–CuI system. It has been demonstrated that thin films, deposited with the sputtering technique, are amorphous and can be crystallized with appropriate heat treatment. The thin film glass-ceramic behaves as a p-type semiconductor, even if it contains p-type Cu2GeSe3and n-type Sb2Se3. The conductivity of Sb2Se3has been greatly improved by appropriate iodine doping. The first photovoltaic solar cells based on the association of iodine-doped Sb2Se3and the glass-ceramic thin films give a short-circuit current density JSCof 10 mA/cm2and an open-circuit voltage VOCof 255 mV, with a power conversion efficiency of about 0.9%.

Tin-dioxide nanocrystals as Er3+ luminescence sensitizers: Formation of glass-ceramic thin films and their characterization

Silica-tin dioxide thin films doped with Er3+ ions were fabricated and investigated. Different parameters such as heat-treatment temperatures, molar concentrations of SnO2 as well as Er3+ ions concentration were changed in order to obtain the best properties of presented thin films. Using several techniques, thin films were characterized and proved to be crack-free, water-free and smooth after a heat-treatment at 1200 °C. Aiming to application in optics, the transparency of thin films was also evidenced by transmission spectra. Based on the photoluminescence measurements, the mechanism of energy transfer from SnO2 nanocrystals to Er3+ ions was examined and discussed.

GLASSY MATERIALS AND LIGHT: PART 2

In this second part it will be discussed some photonic applications of glassy and glass ceramic thin films which can be used as planar waveguides. Some photonic applications require certain specifications of glass, which can be quantified by studying the nonlinear optical properties of the materials. Therefore, a brief introduction of these phenomena is discussed, as well as the use of femtosecond lasers to manipulate the composition or for the preparation of waveguides into glasses. Finally, the article will address a brief introduction on microstructured optical fibers and commercial application prospects for these devices.

Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

Erbium-Doped Tin-Silicate Sol–Gel-Derived Glass-Ceramic Thin Films: Effect of Environment Segregation on the Er<SUP>3+</SUP> Emission

A new class of glass-ceramic nanocomposite systems with a uniform distribution of SnO2 nanocrystals dispersed within an amorphous silica phase is fabricated in the form of thin films by using sol–gel processing. In this work, experiments with (100-x)SiO2-xSnO2 nanocomposite thin films with (x = 25 and 30 mol%) doped with Er3+ ions (concentrations of 0.5, 1 and 2 mol%) are presented. The focus has been both to determine the effect of rare-earth doping on the growth of SnO2 nanocrystals as well as the distribution of the Er3+ ions within the ceramic structure. Vibrational spectroscopic assessments have proven the glass-ceramic nature of the samples. EXAFS and photoluminescence spectra show that the rare-earth ions exist in both amorphous and crystalline phases. Moreover an energy transfer from SnO2 nanocrystals to erbium ions on excitation at 351 nm is demonstrated.

IR reflectance characterization of glass–ceramic films obtained by high pressure impregnation of SnO 2 nanopowders on float glass

Glass–ceramic thin films of tin dioxide on float glass surfaces were obtained using a method based on high pressures and temperatures below the glass transition temperature. SnO 2 thin films were confirmed using XRD, SEM and XRF techniques. These thin films were identified using IR reflectance due to a shift induced by Sn ion content of about ∼100 cm −1 in the main maximum peak position which is typical of stretching vibration intensities of a ν Si −O–Si bridging bonds, or a ν Si – O − nonbridging bonds.

Investigations of the effects of the growth of SnO 2 nanoparticles on the structural properties of glass–ceramic planar waveguides using Raman and FTIR spectroscopies

(100- x) SiO 2– x SnO 2 ( x from 12 to 60 mol%) glass–ceramic thin films have been prepared by the sol–gel processing method, obtaining high SnO 2 concentrations (up to 60 mol%) for the first time. Using an appropriate thermal process, SnO 2 nanocrystals were nucleated in the glassy silica matrix, providing optical waveguides for x ⩽ 30 mol%. M-line measurements were used to determine the thickness and refractive index of each film. Raman and FTIR spectroscopies, in situ high-temperature XRD and TEM data have been used to identify the initiation of crystallization (at about 900 °C for x ⩽ 30 mol%). Calculations based on the low-wavenumber Raman data yield the sizes of the semi-conductor nanoparticles, which vary from 3.2 to 4.6 nm with heat-treatments varying from 900 °C to 1100 °C for SnO 2 concentrations varying from 12 to 30 mol%. Raman and FTIR data have provided information on the structural evolutions of the matrix which result from the formation and the growth of the SnO 2 nanocrystals.

Fabrication and optical properties of NUV-emitting SiO 2–SrB 4O 7:Eu 2+ glass–ceramic thin films

SiO 2–SrB 4O 7:Eu 2+ glass–ceramic thin films were fabricated for possible application in near ultraviolet (NUV) emitting devices. Nano-sized SrB 4O 7:Eu 2+ powders were prepared by a Pechini-type sol–gel method and a subsequent ball-milling treatment. The powders showed NUV emissions centered at 367 nm, upon irradiation with UV of shorter wavelengths, due to an allowed 4 f 65 d 1 → 4 f 7 electronic transition of Eu 2+ ions. The glass–ceramic thin films were prepared by dip-coating of tetraethylorthosilicate (TEOS) solutions dispersed with the nano-sized SrB 4O 7:Eu 2+ powders and a subsequent heat-treatment. It was found that the glass–ceramic thin films had relatively high thermal stability up to 800 °C in terms of the Eu 2+ emissions. SiO 2 layers surrounding SrB 4O 7:Eu 2+ appeared to be effective for the surface passivation of the phosphor particles.

Doping effect and Zr/Ti control in the ferroelectric Pb(Zr,Ti)O 3–SiO 2 based glass–ceramic thin films derived by sol–gel method

Ferroelectric PbZr x Ti 1− x O 3–SiO 2 based glass–ceramic thin films were fabricated and characterized by sol–gel method. The perovskite-phase PbZr x Ti 1− x O 3 (PZT) crystallites were grown in the films, preferentially along the (1 1 1) direction. Zr/Ti ratio in the PZT crystallites was found to decrease with increasing SiO 2 concentration. The excess Pb addition did not decrease the Zr fraction in the PZT crystallites, whereas B added in the glass enhanced the Zr reduction in the PZT crystallites. The Zr/Ti ratio can be controlled to around the morphotropic phase boundary by using precursors with higher Zr concentration. The PbZr 0.6Ti 0.4O 3–10 mol% SiO 2–0.5 mol% B 2O 3 thin film showed the Zr/Ti ratio about 49/51 and good electric properties. Its dielectric constant and remnant polarization were higher than that of other PZT glass–ceramic films with the same amount of glass addition. The PZT glass–ceramic thin film is a suitable candidate for the integrated ferroelectric and piezoelectric devices.

Self-Mending of Microcracks in Barium Titanate Glass-Ceramic Thin Films with High Dielectric Constant

BaTiO3 glass-ceramic thin films were deposited on silicon substrates by the sol–gel method. The films exhibited a mixed structure of glass phase and BaTiO3 grains tens of nanometers in diameter, and had a high dielectric constant, low leakage current, and dielectric loss. An interesting self-mending phenomenon for microcracks due to the fluidity of the glass phase during the annealing process was observed in the films. The effects of the existence of the self-mended microcracks on electrical properties were evaluated. Our experimental results indicate the potential value of BaTiO3 glass-ceramic thin films for integrated high-dielectric-constant media.

Porous SiO2-BaMgF4:Eu(II) Glass-Ceramic Thin Films and Their Strong Blue Photoluminescence

Oxyfluoride glass-ceramic thin films of nominal 90SiO2⋅10(Ba1−xEu x )MgF4 compositions were prepared by sol–gel method starting from mixtures of metal trifluoroacetates and silicon alkoxide precursor solutions. Films were deposited on silica glass substrates by spin-coating and heating at 750°C. Eu2+ ions were preferentially incorporated into BaMgF4 nanoparticles, which were dispersed in the silica glass matrix. The films exhibited broad-band blue photoluminescence (PL) in response to the ultraviolet light excitation. Addition of N,N-dimethylformamide to starting coating solutions resulted in a porous microstructure of the heat-treated films. Efficient UV excitation was promoted due to the Rayleigh scattering in the porous films; thereby the PL emissions could be strongly enhanced.

Porous Phosphor Thin Films of Oxyfluoride SiO2–BaMgF4: Eu2+ Glass–Ceramics Prepared by Sol–Gel Method

Abstract Eu2+ ions were incorporated into SiO2–BaMgF4 glass–ceramic thin films using a sol–gel method. The addition of N,N-dimethylformamide to a starting solution resulted in a porous microstructure of the film prepared. The films exhibited blue emission peaking at 420 nm by excitation at 290 nm. The emission was effectively enhanced in the porous film owing to scattering absorption of the excitation light.

Sol-Gel Processing and Luminescent Properties of Rare-Earth Oxyfluoride Materials

Luminescent rare-earth oxyfluoride materials were prepared by a sol-gel method using trifluoroacetic acid as a fluorine source. Crystalline (La, Eu)OF powders and thin films were obtained by heating gels at typically 600–800°C. Transparent SiO2-LaOF glass-ceramic thin films were also prepared by mixing the trifluoroacetate sols and silica sols, spin-coating on silica glass substrates and heating at temperatures 600–900°C. Eu3+ ions doped in the oxyfluoride materials exhibited a strong red 5D0 → 7F2 emission (611 nm) by a charge-transfer (O2−-Eu3+) excitation with ultra-violet radiation (265 nm). It was strongly suggested that the Eu3+ activators were preferentially incorporated into the crystalline LaOF phase in the SiO2-LaOF glass-ceramics.