Glassy Thin Films Research Articles

The factors affecting the thickness of sol-gel derived silica coatings prepared by dipping

A partially hydrolysed solution of tetraethoxysilane was used to prepare thin glassy films on glass microscope slides by dipping. The thickness of these films after heat treatment to 500 °C was determined as a function of the withdrawal speed and the properties of the coating solution, such as viscosity, density and surface tension. The results were fitted to available theories of dip coating and acceptable agreement was obtained for coating solution viscosities below around 8 mPas and withdrawal speeds in the range 5 to 15 cm/min. In addition, the thickness of selected coatings were obtained at a range of heat treatment temperatures. Differences in the thickness of coatings prepared after different maturing times of the solution are also discussed.

Precipitation of Krypton in an Amorphous Ti-Cr Alloyc.

AbstractResults of a TEM investigation of the microstructural changes produced by the room temperature implantation of energetic Kr+ ions into a glassy Ti-Cr thin film are reported. As in other metals, the Kr precipitates as solid crystallites. The precipitation of crystalline Kr is accompanied by ultrafine crystallization of the metal host around each Kr crystal. With increasing fluence, the Kr precipitates grow to a critical size at which they melt, and the adjacent fine metal crystals disappear. A new TEM imaging technique is described briefly which utilizes the small angle electron scattering fine structure and which in principle is capable of revealing all fine particles simultaneously.

Thermoelectric power of Manganin

Manganin wires have been used as reference leads in measuring the thermopowers of evaporated thin glassy metal films. The thermopower of manganin which was calibrated against Pb in the temperature range 1.5K to 300K is reported.

Influence of the intergranular microstructure of substituted nitrides on high temperature strength

The relationships between the intergranular structure of substituted silicon nitrides and their high temperature strength have been considered. It has been shown that four types of intergranular structure can be distinguished. These structures depend on the nature and amount of additives. Analytical electron microscopy (X-ray microanalysis, microdiffraction and electron-induced processes) enables a precise characterization of these structures. If an extended glassy phase always appears to be detrimental, it has been shown that a thin glassy film may improve the high temperature strength and the cutting life of sialon tools and may at least be a fair compromise to obtain dense and homogeneous hot-pressed silicon nitrides.

Silicon-compatible integrable infrared-light sources

Novel silicon-compatible integrable infrared-light emitters are discussed. Emission occurs above a threshold current in the conducting state of glassy chalcogenide thin films at an energy near half bandgap. The emission may occur in a very wide range of glassy materials.

In situ electrodeposition for the determination of lead and cadmium in sea water

Electrodeposition techniques for the direct determination of lead and cadmium in sea water at the natural pH and in the presence of dissolved oxygen are examined. Anodic stripping voltammetry, at either the hanging mercury drop electrode or glassy carbon thin film electrode, is suitable for the determination of labile lead and cadmium. The presence of dissolved oxygen increases the height of the lead wave with a shift to more negative potentials. A more versatile technique is in situ deposition of labile metals on a mercury-coated graphite tube electrode. The mercury film, deposited in the laboratory, is stable on the dried tubes which are used later for field electrodeposition. The deposited metals are determined by electrothermal atomic absorption spectrometry.

ChemInform Abstract: THE MICROSTRUCTURE AND DISTRIBUTION OF IMPURITIES IN HOT‐PRESSED AND SINTERED SILICON NITRIDES

AbstractZwei heiß‐gepreßte (HS 130 und NC 132) und zwei gesinterte Sinitride (mit Zusätzen von MgO + Al2O3 bzw. Y2O3 + Al2O3) werden untersucht.

The Microstructure and Distribution of Impurities in Hot‐Pressed and Sintered Silicon Nitrides

Two hot‐pressed (HS 130 and NC 132) and two sintered silicon nitrides (with MgO·Al2O3 and Y2O3 additives) were examined in detail by X‐ray diffraction, emission spectroscopy, medium‐and high‐resolution electron microscopy, and X‐ray microanalysis. The overall morphologies of the four materials are quite comparable. Very thin (10 to 20 Å) intergranular glassy films were detected in all the materials at almost all grain and interphase boundaries. The composition of these glasses was determined by X‐ray microanalysis using a 200‐Å electron probe and the softening temperature was estimated from available phase diagrams. The results are in good agreement with the known softening temperatures for the four silicon nitrides, thereby confirming the central role played by glassy phases in determining the high‐temperature mechanical properties of these materials.

Coatings formed at the interface of glass and plumbite-treated cotton

Novel thin glassy films formed by heating plumbite-treated cotton in contact with a silicate material were examined by X-ray diffraction, optical microscopy, electron transmission and electron scanning microscopy, electron spectroscopy for chemical analysis, energy-dispersive analysis by X-rays, thermogravimetric analysis, differential thermal analysis, X-ray fluorescence and atomic absorption. The films were formed by an unusual mechanism which was dubbed “element migration”.

Vibrational spectra of glassy water aggregates and thin films

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On the mechanism of formation of amorphous condensates from the vapour phase (I). General theory

The thermodynamic and kinetic conditions for the vapour condensation of non-crystalline thin films are formulated within the framework of the classical nucleation theory. The conditions for the predominant formation of crystalline or amorphous thin films are given and the acting supersaturation and the activity of the substrate are taken into account. Generalized criteria for the formation of amorphous (liquid or glassy) thin films are given and a temperature diagram is established which enables the concrete determination of the limits within which amorphous condensates are to be expected. It is thus possible to give the theoretical background of a technically and experimentally interesting process; the applications of the obtained results to the existing experimental data are also given in some detail. Further problems of the vapour condensation and stability of amorphous thin films, especially some effects of secondary crystallization will be discussed in more detail in Parts II and III of this series of papers, which report on experimental investigations of the formation of amorphous condensates.

Infrared and Raman spectra of group I nitrate aggregates in carbon dioxide matrixes and glassy thin films

Infrared and Raman spectra of group I nitrate aggregates in carbon dioxide matrixes and glassy thin films

A new type of switching and memory effect in semiconductor-dielectric thin film junction

A rapid switching from a highly conductive to a highly resistive state with a certain threshold voltage V th has been observed in a glassy semiconductor-dielectric thin film (e.g. SnO 2SbSI) heterostructure junction. The highly resistive state has a nonvolatile memory action in the whole forward biased region, and the memory can be easily erased by applying a small reverse bias voltage V r. Typical values of performance are: V th = 2.2 V, I th = 2.3 mA, V r = 0.4 V, I r = 0.4 mA (in the ON state), and switching ON and OFF time are less than 5 μs. The OFF state is quite stable and no noticeable change in the characteristics is observed in more than one week storage test. The phenomena are repeatable and reproducible. A tentative model for the explanation of the phenomena is discussed. Some typical combinations of junction materials are described.

Thin films of glass and their application to biomedical sensors

Thin films of glass are attractive as a means for protecting integrated circuits for use in biological systems and are especially suitable for use with biomedical sensors. They offer advantages over polymer films since they can be deposited in thin, uniform layers and can be photoengraved using conventional techniques. This paper first reviews the requirements for film quality in using thin glassy films in these applications and then reviews the techniques available for film deposition. One technique which has been found especially suitable for biomedical work is described in detail, and the characterization of the resulting films is discussed.

Crystallization of polycarbonate from the glassy state. part II. Thin films melted and quenched

Abstract The crystallization of glassy amorphous thin polycarbonate films quenched from the melt has been followed. Structures similar to those observed during the crystallization of films containing small amount of adsorbed solvent are formed. However, crystallization, at the same temperatures, is much slower and more irregular. Preannealing of the samples below Tg affects the crystallization process, increasing the nucleation rate. Annealing above Tg does not destroy all order gained by annealing below Tg.

Crystallization of polycarbonate from the glassy state. part I. Thin films cast from solution

Abstract The morphology of glassy amorphous thin polycarbonate film cast from solution is affected by thermal treatments. Annealing above 80° C and below Tg results in an increase in the size of the ordered regions, nodules, up to several hundred Angstroms. The crystallization process from the glass, taking place at 145° C, is divided into three major steps. At first the nodules merge into patches which aggregate to form lamellar planar structures. In some cases the planar structures are well-formed single crystals. Following this, spherulitic arms develop from the planar structures as centers. These arms at first consist of aggregates of large nodules which recrystallize to form lamellae; the final morphology is spherulitic in nature. The effect of film thickness and of several substrates on the morphology has been observed. Applying stress at room temperature to the crystalline film results in a breaking up of the lamellae into small blocks.

Mass spectrometric studies of laser-induced vaporization. I. Selenium

The laser - mass spectrometer has been used to study the vaporization of the hexagonal and α-monoclinic forms of crystalline selenium as well as glassy and vapor-grown thin films of amorphous selenium. The pentamer molecular ion, Se 5 +, dominates the ionic species in the vapor emanating from all forms of selenium and Se 5 is the second most important species in the vapor. The dimer, Se 2, is the major neutral species in the vapor and presumably is formed as a fragmentation product. The pentamer molecular species is postulated to be a ring structure.