Glasses can be formed by many routes. In some cases, distinct polyamorphic forms are found. The normal mode of glass formation is cooling of a viscous liquid. Liquid behavior during cooling is classified between "strong" and "fragile," and the three canonical characteristics of relaxing liquids are correlated through the fragility. Strong liquids become fragile liquids on compression. In some cases, such conversions occur during cooling by a weak first-order transition. This behavior can be related to the polymorphism in a glass state through a recent simple modification of the van der Waals model for tetrahedrally bonded liquids. The sudden loss of some liquid degrees of freedom through such first-order transitions is suggestive of the polyamorphic transition between native and denatured hydrated proteins, which can be interpreted as single-chain glass-forming polymers plasticized by water and cross-linked by hydrogen bonds. The onset of a sharp change in d dT( is the Debye-Waller factor and T is temperature) in proteins, which is controversially indentified with the glass transition in liquids, is shown to be general for glass formers and observable in computer simulations of strong and fragile ionic liquids, where it proves to be close to the experimental glass transition temperature. The latter may originate in strong anharmonicity in modes ("bosons"), which permits the system to access multiple minima of its configuration space. These modes, the Kauzmann temperature T(K), and the fragility of the liquid, may thus be connected.

https://science.sciencemag.org/content/sci/267/5206/1924.full.pdf

Formation of glasses from liquids and biopolymers.

The MN+1AXN phases: A new class of solids

▪ Abstract Soft lithography, a set of techniques for microfabrication, is based on printing and molding using elastomeric stamps with the patterns of interest in bas-relief. As a technique for fabricating microstructures for biological applications, soft lithography overcomes many of the shortcomings of photolithography. In particular, soft lithography offers the ability to control the molecular structure of surfaces and to pattern the complex molecules relevant to biology, to fabricate channel structures appropriate for microfluidics, and to pattern and manipulate cells. For the relatively large feature sizes used in biology (≥50 μm), production of prototype patterns and structures is convenient, inexpensive, and rapid. Self-assembled monolayers of alkanethiolates on gold are particularly easy to pattern by soft lithography, and they provide exquisite control over surface biochemistry.

/pdf/soft-lithography-in-biology-and-biochemistry-1qiku7qz44.pdf

Soft Lithography in Biology and Biochemistry

This article presents an overview of the essential aspects in the fabrication of silicon and some silicon/germanium nanostructures by metal-assisted chemical etching. First, the basic process and mechanism of metal-assisted chemical etching is introduced. Then, the various influences of the noble metal, the etchant, temperature, illumination, and intrinsic properties of the silicon substrate (e.g., orientation, doping type, doping level) are presented. The anisotropic and the isotropic etching behaviors of silicon under various conditions are presented. Template-based metal-assisted chemical etching methods are introduced, including templates based on nanosphere lithography, anodic aluminum oxide masks, interference lithography, and block-copolymer masks. The metal-assisted chemical etching of other semiconductors is also introduced. A brief introduction to the application of Si nanostructures obtained by metal-assisted chemical etching is given, demonstrating the promising potential applications of metal-assisted chemical etching. Finally, some open questions in the understanding of metal-assisted chemical etching are compiled.

/pdf/metal-assisted-chemical-etching-of-silicon-a-review-2djk1xh2iu.pdf

Metal-Assisted Chemical Etching of Silicon: A Review

The present invention provides stretchable, and optionally printable, semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed. Stretchable semiconductors and electronic circuits of the present invention preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention may be adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.

http://science.sciencemag.org/content/sci/311/5758/208.full.pdf

Stretchable form of single crystal silicon for high performance electronics on rubber substrates

A model is proposed to describe the temperature dependence of the aluminum oxynitride (AlxOyNz) diffusion barrier formation during a silver self-encapsulation process. These barrier layers form in the temperature range of 500–725 °C during anneals of the Ag/Al bilayers on oxidized Si substrates in an ammonia ambient. Experimental results show that temperature has a significant effect on the kinetics of this process. In this investigation, the diffusion of Al atoms through the Ag layers during self-encapsulation process is modeled using an analytical solution to a modified diffusion equation. This model shows that higher anneal temperatures will minimize the retardation effect by i) reducing the chemical affinity between Al and Ag atoms, and ii) allowing more Al atoms to surmount the interfacial energy barrier between the metal layer (Ag) and the newly formed AlxOyNz diffusion barriers. The theoretical predictions on the amount of segregated Al atom correlate well with experimental results from Rutherford backscattering spectrometry. This model in addition confirms the self-passivation characteristics of AlxOyNz diffusion barriers formed by Ag/Al bilayers annealed between 500∼725 °C.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400598297

Kinetics Model for the Self-Encapsulation of Ag/Al Bilayers

Direct observation of microstructural changes in ion-beam modified ceramics

TEM study of buried yttrium silicide formed by ion implantation

We compared the epitaxital regrowth of amorphous silicon which had been implanted with Ne, Ar, or Kr at annealing temperatures below 600°C. The aim was to determine if silicon sputtered on single crystal silicon with an appropriate sputtering gas could grow epitaxially. We showed that this process is not possible because of the high concentration of gas included in sputtered films. We evaluated the maximum concentration of Ne, Ar, and Kr in silicon, above which the amorphous layer does not regrow epitaxially.

The influence of noble gas atoms on the epitaxial growth of implanted and sputtered amorphous silicon

Transmission electron microscopy (TEM) in both cross sectional and plan view is used to study the effect of annealing Ag-Ti bilayers deposited on SiO2/Si substrates in an NH3 ambient. The resulting structure, texture and grain size are investigated. Comparisons are made between films annealed at 400, 500 and 600°C. Silver films show increasingly strong 〈111〉 texture with annealing temperature while exhibiting a bamboo-like grain structure at 600°C. Considerable grain growth with lateral grain sizes of up to 5 times the thickness of the Ag film is observed at 600°C. The grains typically extend through the Ag film thickness. The Ti/SiO2 interface uniformity and the absence of voids at the substrate surface are positive indicators of the role of titanium as a good adhesion promoter. At 600°C, a uniform TiN encapsulation layer is observed on the Ag surface.

James W. Mayer

Papers

Kinetics Model for the Self-Encapsulation of Ag/Al Bilayers

Direct observation of microstructural changes in ion-beam modified ceramics

TEM study of buried yttrium silicide formed by ion implantation

The influence of noble gas atoms on the epitaxial growth of implanted and sputtered amorphous silicon

Tem Observations of AG-TI Bilayers After Thermal Aging Treatment in a Reducing Ambient