Vitreous Films Research Articles

Dy3+ and Tb3+ co-doped boro-phosphate sol–gel vitreous thin films

A new glass with the molar composition 20B2O3-60P2O5-10ZnO-5Dy2O3-5Tb2O3 was obtained by sol–gel method and deposited on silicate glass substrates by spin-coating, at different rotation speeds and number of layers. XRD proved the vitreous state of the thin films. FTIR spectroscopy revealed the borate, meta-phosphate and mixed boro-phosphate networks in the samples. SEM, combined with AFM, demonstrated the advantages of higher deposition speeds on the higher uniformity and lower roughness of the thin films. The proposed composition of the films was proved by EDS investigations, which identified all elements in the desired proportions. Absorption bands and luminescence emissions specific to Dy3+ and Tb3+ ions are identified. These multi-component films can be used for magneto-optical devices, laser mirrors and luminescent applications.

Electron exchange between neutral and ionized impurity iron centers in vitreous arsenic selenide

Impurity iron atoms in vitreous arsenic-selenide As2Se3 films modified by iron form one-electron donor centers with an ionization energy of 0.24 (3) eV (the energy is counted from the conduction-band bottom). The Fermi level is shifted with an increase in the iron concentration from the mid-gap to the donorlevel position of iron due to the filling of one-electron states of the acceptor type lying below the Fermi level. At an iron concentration of ≥3 at %, the electron-exchange process is observed between neutral and ionized iron centers resulting in a change both in the electron density and in the tensor of the electric-field gradient at iron-atom nuclei with increasing temperature above 350 K.

Giant Faraday Rotation through Ultrasmall Fe0n Clusters in Superparamagnetic FeO-SiO2 Vitreous Films.

Magnetooptical (MO) glasses and, in particular, Faraday rotators are becoming key components in lasers and optical information processing, light switching, coding, filtering, and sensing. The common design of such Faraday rotator materials follows a simple path: high Faraday rotation is achieved by maximizing the concentration of paramagnetic ion species in a given matrix material. However, this approach has reached its limits in terms of MO performance; hence, glass‐based materials can presently not be used efficiently in thin film MO applications. Here, a novel strategy which overcomes this limitation is demonstrated. Using vitreous films of xFeO·(100 − x)SiO2, unusually large Faraday rotation has been obtained, beating the performance of any other glassy material by up to two orders of magnitude. It is shown that this is due to the incorporation of small, ferromagnetic clusters of atomic iron which are generated in line during laser deposition and rapid condensation of the thin film, generating superparamagnetism. The size of these clusters underbids the present record of metallic Fe incorporation and experimental verification in glass matrices.

Origin of the electrical activity of iron atoms in vitreous arsenic selenide

Iron atoms in vitreous arsenic selenide films form single electron donor centers, while the Fermi level shifts from the middle of the band gap to the bottom of the conduction band with an increase in the iron concentration due to the filling of single electron states of the acceptor type located below the Fermi level.

Vitreous films of Ga6Ge17S43 composition as a biochip substrate

Adhesion of protein materials with fluorescent stains to the film of Ga6Ge17S43 composition fabricated by the pulsed laser deposition was investigated. Resistance of the protein markers deposited onto the film to a washing in buffer isotonic solution was established. The obtained results provide the possibility to use these films for the development of protein biochips.

Second harmonic generation in N-doped H : SiO2 films by poling under x-ray irradiation

Second harmonic generation was observed in N-doped H : SiO2 films after poling under x-ray irradiation from a synchrotron at room temperature. The measurements of the photocurrent confirmed that the vitreous films have been poled. The magnitude of the induced second-order nonlinear coefficients measured from the Maker fringe is in the order of 0.001 pm V−1. This provides direct evidence that poling under x-ray irradiation is achievable at room temperature in amorphous materials.

Two-dimensional silica: Crystalline and vitreous

Two-dimensional SiO2 films may be grown on metal single crystal surfaces. It is possible to grow crystalline and vitreous (glassy) films and study their structural, vibrational, and electronic properties. In particular, the structures of a crystalline and a vitreous film may be imaged with atomic resolution side by side which opens avenues to study long standing problems of real space imaging of a crystal to glass transition.

SiO 2–K 2O–MgO vitreous films doped with erbium and silver nanoparticles for optical applications

The search of new glass compositions for films produced with high optical transparency throughout the visible spectrum from 0.5 μm to the near infrared region is important for optical integrated applications. In this work, we present the preparation of SiO 2–K 2O–MgO vitreous sol–gel films on SiO 2 substrates co-doped with Er 3+ and Ag nanoparticles. The silver quantum dots were synthesized in continuous media ( ex situ) by chemical reduction and isolation from media by anchoring chemical solution-compatible modifiers (aminosilanes) on their surfaces; then, they were successfully integrated into the glass matrix. We present the study of the preparation process and characterization of sol–gel matrices doped with Ag 0 nanoparticles and Er 3+, analyzing the role of synthesis parameters and optical properties, and comparing them with other wave-guide compositions, such as PLZT and SiO 2–B 2O 3.

Determination of the quantitative composition of As-Se and Ge-Se glasses and films by X-ray fluorescence analysis

A method of standards has been proposed for determining the quantitative contents of germanium, arsenic, and selenium in vitreous samples and films of the As1 − xSex and Ge1 − xSex compositions with the use of X-ray fluorescence analysis. The application of this technique makes it possible to determine the quantitative composition of As1 − xSex and Ge1 − xSex glasses and films with an accuracy of ±0.001 with respect to the parameter x.

Features of formation of germanium silicate glasses during oxidation of nanostructured films of germanium-doped polycrystalline silicon

Nanostructured films of polycrystalline silicon obtained by joint pyrolysis of monosilane (SiH4) and monogermane (GeH4) were oxidized in a medium of dry and wet oxygen. As a result of their oxidation, vitreous films of complex oxides of germanium and silicon, germanium silicate glass (GSG), is formed. It is established that the presence of germanium in the composition of nanostructured films of polycrystalline silicon (NSF PCS) increases their reaction ability with respect to oxidation. Using the methods of IR spectroscopy, XPE spectroscopy, Auger spectroscopy, and thermal analysis, the composition and phase transformation of vitreous oxides formed in the course of oxidation of NSF PCS are investigated. It is shown that the composition and phase transformation of the films of vitreous silicon and germanium oxides depend on the germanium content in the NSF PCS and conditions of their oxidation.

Influence of irradiation on the local environment of chalcogen atoms in vitreous films of the As-S, As-Se, and As-S-Se systems

The results of the experimental study of the photoinduced changes in the optical properties of vitreous films in the As-S, As-Se, and As-S-Se systems are reported. With the use of the data obtained from the 129Te(129I) Mossbauer emission spectra, the revealed changes in the optical properties are explained by the transformation of the glass structure under radiation.

Materials for optical information recording on the base of subnanostructured chalcogenide films

X-ray structural researches of chalcogenide vitreous semiconductor films are carried out. It is shown that optical information records in such films are accompanied also by their molecular structural modification. New functional property of molecular films using direct optical record of deep optic phase relief are shown.

Photoinduced bleaching in Ga-Ge-S(Se) vitreous films

Vitreous films in the Ga-Ge-S(Se) system are prepared through pulsed laser deposition and investigated. An analysis of the data of Raman and energy-dispersive X-ray spectroscopy demonstrates that the composition and structure of the films are similar to those of the monolithic glass. Exposure of the films to radiation with an energy higher than the band gap leads to bleaching of sulfur-based films due to the local oxidation of the films as judged from the data of infrared, Raman, and energy-dispersive X-ray spectroscopy. The replacement of sulfur by selenium in the composition of the films results in the opposite effect: irradiation of the films brings about the photoinduced darkening. Examination of the samples with the use of a scanning electron microscope does not reveal a substantial change in the morphology of the films under irradiation. The observed effect is used to write a copy of the diffraction grating with a resolution of 1200 grooves/mm.

SiO2‐CaO Vitreous Films Deposited onto Ti6Al4V Substrates

AbstractA sol‐gel dipping method has been utilised to deposit SiO2‐CaO films onto Ti6Al4V alloy substrates. These layers were prepared by the dip‐coating technique from a series of precursor solutions with different concentrations of glassy xSiO2‐(1 − x)CaO (x = 0.8 mol) diluted with absolute ethanol. The characterisation of the films by a variety of techniques reveals differences in the textural properties and in the films’ thicknesses depending on the sol concentration in the precursor solution. Concentrated precursor solutions yield porous layers with a higher thickness and surface roughness than those obtained from the dilute ones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The effect of ultrafast low-temperature doping of vitreous As-Se films with copper, silver, gold, and chromium (The Khan effect)

The effect of ultrafast doping of chalcogenide vitreous As-Se, Ge-Se, and other films with Cu, Ag, Au, Cr, and other metals previously discovered in metal/chalcogenide vitreous film heterostructures at 250–350 K is analyzed.

Electrochemical microsensor for the detection of Na+ ions

Abstract Thin vitreous films were elaborated by microelectronic techniques (vacuum evaporation, r.f. sputtering) and structural and electrical properties were characterized respectively by X-ray diffractometry and complex impedance spectroscopy measurements. Morphology and composition of thin films were examined by scanning electron microscopy with energy dispersive spectroscopic microprobe. Based on these thin films, Na + -selective microsensors were built up with a sodium aluminosilicate glass as the sensitive membrane and thin film of borophosphate as the ionic bridge acting as an interfacial layer providing an ionic and electronic exchange between the collector and the sensitive membrane. Electrochemical behaviour and sensitivity results regarding the microsensor were investigated. Microsensors exhibit near-Nerstian response in the Na + -concentration range of 10 −1 –10 −4 mol/l with a detection limit close to 5 × 10 −4 M and good reproducibility.

Thin films of chalcogenide glass as sensitive membranes for the detection of mercuric ions in solution

Thin vitreous films elaborated by microelectronic techniques can be used to build up sensitive microsystems in order to detect ionic species (Hg 2+) in aqueous solution. Characteristics of sensing systems based on thin films of chalcogenide glasses are presented. The microsensors exhibit quasi-Nernstian potentiometric response over five orders of magnitude with a limit of detection below 10 −6 mol 1 −1. In the presence of interfering heavy-metal ions (PB 2+, CD 2+) the sensing systems are very selective, since low selectivity coefficients are obtained versus those ionic species.

Cryo imaging using an energy-filtering TEM (EFTEM): Optimum use of phase-contrast transfer function (PCTF)

Lack of contrast is one of the numerous problems arising from imaging of vitrified biological macromolecules in a TEM. This is due to the similar density of biological material and of vitreous ice and to the high background of inelastic scattering in the ice which is about four times that of carbon.Consequently in a CTEM images have to be recorded 1-3 μm underfocus to maximise phase contrast which in the same sense decreases the reliability of density information.Elastic filtering using an (EFTEM) allows closer to focus imaging still achieving considerable contrast. For 3D reconstruction of molecular densities the largest source of error is likely to arise from contributions of the PCTF. Thus, such images have to be corrected for the PCTF, which is much morereliably done for elastically filtered images close to focus.Thin vitreous ice films containing the virus particles were prepared on holey carbon grids and examined with cryo EM procedures. Images of frozen-hydrated cucumber mosaic virus (CCMV) particles ( Ø of roughly 25 nm) were recorded in Elastic Brightfield mode using the Zeiss EM 912 OMEGA with integrated imaging spectrometer and Koehler Illumination. Magnification was 50.000x, HT 120 kV, energy width 7 eV, total dose 800 electrons /nm2.

Photoinduced instabilities in chalcogenide glasses for optical recording media

Abstract The peculiarities of the mechanism of optical information recording in vitreous semiconductor films undergoing photoinduced instabilities, caused by a structural transformation at distances exceeding medium-range order, have been studied. Formation of a dissipative structure in the behaviour of the parameters and its period dependence on the power density of the exciting illumination, composition and structural defectiveness are considered.

SiO2-Sm2O3 vitreous films via the sol-gel method

SiO2-Sm2O3 vitreous films 120 nm thick were obtained via the sol-gel method. Infrared, energy-dispersive analysis of X-rays, spectroscopic ellipsometry and absorption spectroscopy showed a total inclusion of samarium in the silica matrix, which remains amorphous up to 1000 °C. The inclusion of the samarium ion increases the porosity. The optical properties of films were investigated by spectro-ellipsometry, and the parameters obtained were compared with those obtained by other techniques.