https://onlinelibrary.wiley.com/doi/pdf/10.1021/js9601896

Characteristics and Significance of the Amorphous State in Pharmaceutical Systems

Recently, we have demonstrated the potential of amorphous oxide semiconductors (AOSs) for developing flexible thin-film transistors (TFTs). A material exploration of AOSs desired as the channel layer in TFTs is most important for developing high-performance devices. Here, we report our concept of material exploration for AOSs in high-performance flexible and transparent TFTs from the viewpoints of chemical bonding and electronic structure in oxide semiconductors. We find that amorphous In–Ga–Zn–O (a-IGZO) exhibits good carrier transport properties such as reasonably high Hall mobilities (>10 cm2V-1s-1) and a good controllability of carrier concentration from <1015 to 1020 cm-3. In addition, a-IGZO films have better chemical stabilities in ambient atmosphere and at temperatures up to 500 °C. The flexible and transparent TFT fabricated using a-IGZO channel layer at room temperature operated with excellent performances, such as normally-off characteristics, on/off current ratios (~106) and field-effect mobilities (~10 cm2V-1s-1), which are higher by an order of magnitude than those of amorphous Si:H and organics TFTs.

https://iopscience.iop.org/article/10.1143/JJAP.45.4303/pdf

Amorphous Oxide Semiconductors for High-Performance Flexible Thin-Film Transistors

In comparing a material's resistance to distort under mechanical load rather than to alter in volume, Poisson's ratio offers the fundamental metric by which to compare the performance of any material when strained elastically. The numerical limits are set by ½ and -1, between which all stable isotropic materials are found. With new experiments, computational methods and routes to materials synthesis, we assess what Poisson's ratio means in the contemporary understanding of the mechanical characteristics of modern materials. Central to these recent advances, we emphasize the significance of relationships outside the elastic limit between Poisson's ratio and densification, connectivity, ductility and the toughness of solids; and their association with the dynamic properties of the liquids from which they were condensed and into which they melt.

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Poisson's ratio and modern materials

Jets, ie collimated streams of matter, occur from the microscale up to the large-scale structure of the universe Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology They also arise from the last but one topology change of liquid masses bursting into sprays Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects

Physics of liquid jets

Basic characteristics of the liquid-glass transition are reviewed, emphasizing its universality and briefly summarizing the most popular phenomenological models. Discussion is focused on a number of alternative models which one way or the other connect the fast and slow degrees of freedom of viscous liquids. It is shown that all these ``elastic'' models are equivalent in the simplest approximation.

/pdf/colloquium-the-glass-transition-and-elastic-models-of-glass-zkla9ibwsp.pdf

Colloquium : The glass transition and elastic models of glass-forming liquids

Introduction. Fundamentals of the Glassy State. Glass Formation Principles. Glass Microstructure: Phase Separation and Liquid Immiscibility. Glass Compositions and Structures. Composition-Structure-Property Relationship Principles. Density and Molar Volume. Elastic Properties and Microhardness of Glass. The Viscosity of Glass. Thermal Expansion of Glass. Heat Capacity of Glass. Thermal Conductivity and Heat Transfer in Glass. Glass Transition Range Behavior. Permeation, Diffusion and Ionic Conduction in Glass. Dielectric Properties. Electronic Conduction. Chemical Durability. Strength and Toughness. Optical Properties. Fundamentals of Inorganic Glassmaking. Appendix I: Elements of Linear Elasticity. Appendix II: Units and General Data Conversions. Subject Index.

/pdf/fundamentals-of-inorganic-glasses-2hmolvn1fg.pdf

Fundamentals of Inorganic Glasses

This paper reviews the progress that has been made in our understanding of the chemical strengthening of glass by ion exchange over its nearly five decades of history. Lessons learned are briefly discussed; more importantly, those which are yet to be learned are highlighted. It is recognized that, except for detailed compositional effects, the kinetics of ion interdiffusion process and the chemical strengthening technology are reasonably well understood. However, the science of stress generation and its concurrent relaxation is far from being clear despite the elegant analogy to thermal stresses invoked by Cooper. The need to understand plasticity of glass network during accommodation of a larger invading ion is emphasized. In turn, the influence of network topology on its yield strength in shear as well as hydrostatic modes is recognized. For expanded applications under extreme conditions of loading, damage evolution in chemically strengthened glass needs to be studied. Such a study is linked to our understanding of the terms “strength,”“hardness,”“toughness,” and “brittleness” of glass.

Chemical Strengthening of Glass: Lessons Learned and Yet To Be Learned

Glasses strengthen during an ion exchange experiment as a result of the high surface compression that develops from the stuffing of the invading alkali ion into the smaller host alkali ion site and the non-relaxation of this compression. The kinetics are described in terms of a Nernst–Planck interdiffusion coefficient of the exchanging ions in a stack of mixed-alkali glass layers with varying ratios of the alkali. The interdiffusion coefficient is suppressed by compression and enhanced by tension. However, the measured surface compression is usually 2–4 times lower than that calculated using thermal stress analogy incorporating an elastic suppression of the molar volume difference of the as-melted mixed-alkali glasses. A new view of the physics of deformations and failure of stress to continue to buildup is presented in an effort to seek technology improvements. Reduced stresses are ascribed to network yield in two separate modes: yielding of the shape-conserving hydrostatic stress component which prevents elastic expansion of molar volume and yielding of the volume-conserving deviatoric (pure shear) stress which leads to measurable shape change. An anomalous subsurface tension is also explained in this view. By drawing analogy to microindentation, it is concluded that optimum network topology glasses should undergo the least plastic deformation and, hence, develop a higher surface compression.

The physics of chemical strengthening of glass: Room for a new view

High purity chalcogenide glasses incorporating Ge, Sb, Se, As and Te were prepared by vacuum melting of previously distilled 5 N to 6 N pure raw materials from which the surface oxide was also removed in some instances. Glass transition temperatures, Tg, of several chalcogenide glasses prepared by similar processing techniques were determined using differential scanning calorimetry (DSC). An emperical relationship between the glass transition temperature and average coordination number is proposed by modifying the Gibbs-DiMarzio equation for glass transition of a cross-linked polymer as a function of cross-link density. The results for the Tg of three ‘iso-structural’ systems are reported and discussed in light of presumed structural arrangements in these glasses.

Gibbs-DiMarzio equation to describe the glass transition temperature trends in multicomponent chalcogenide glasses

High purity chalcogenide glasses with an average covalent coordination number, 〈 r 〉, in the GeSe binary and GeSbSe ternary systems between 2 and 2.8 were prepared by vacuum melting pre-distilled elements. To understand the effects of 〈 r 〉 on glass-forming capability, properties such as thermal expansion coefficient, molar volume and heat capacity were studied as a function of 〈 r 〉. Prior authors have searched, generally fruitlessly, for extremum behavior either in glassy state properties or in liquid state properties of glass-forming compositions at 〈 r 〉 = 2.4 to support Phillips' constraint theory. The missing link is provided if one examines the configurational changes during glass transition at ordinary cooling rates. The configurational contributions to the heat capacity and thermal expansion, in addition to the molar volume, show distinct minima at 〈 r 〉 = 2.4, suggesting that the structural rearrangements for the 〈 r 〉 = 2.4 liquid in the glass transition region are minimized. If such a liquid possesses minimized accessible structural rearrangements in the supercooled liquid region as well, then it may be concluded that such a liquid would display a poor crystallization tendency. This, then, renders support to Phillips' argument that 〈 r 〉 = 2.4 solid with degrees of freedom equal to the number of constraints marks the ‘best’ glass.

Arun K. Varshneya

Papers

Fundamentals of Inorganic Glasses

Chemical Strengthening of Glass: Lessons Learned and Yet To Be Learned

The physics of chemical strengthening of glass: Room for a new view

Gibbs-DiMarzio equation to describe the glass transition temperature trends in multicomponent chalcogenide glasses

Configurational arrangements in chalcogenide glasses: A new perspective on Phillips' constraint theory