The Al x Ga1−x As/GaAs heterostructure system is potentially useful material for high‐speed digital, high‐frequency microwave, and electro‐optic device applications Even though the basic Al x Ga1−x As/GaAs heterostructure concepts are understood at this time, some practical device parameters in this system have been hampered by a lack of definite knowledge of many material parameters Recently, Blakemore has presented numerical and graphical information about many of the physical and electronic properties of GaAs [J S Blakemore, J Appl Phys 5 3, R123 (1982)] The purpose of this review is (i) to obtain and clarify all the various material parameters of Al x Ga1−x As alloy from a systematic point of view, and (ii) to present key properties of the material parameters for a variety of research works and device applications A complete set of material parameters are considered in this review for GaAs, AlAs, and Al x Ga1−x As alloys The model used is based on an interpolation scheme and, therefore, necessitates known values of the parameters for the related binaries (GaAs and AlAs) The material parameters and properties considered in the present review can be classified into sixteen groups: (1) lattice constant and crystal density, (2) melting point, (3) thermal expansion coefficient, (4) lattice dynamic properties, (5) lattice thermal properties, (6) electronic‐band structure, (7) external perturbation effects on the band‐gap energy, (8) effective mass, (9) deformation potential, (10) static and high‐frequency dielectric constants, (11) magnetic susceptibility, (12) piezoelectric constant, (13) Frohlich coupling parameter, (14) electron transport properties, (15) optical properties, and (16) photoelastic properties Of particular interest is the deviation of material parameters from linearity with respect to the AlAs mole fraction x Some material parameters, such as lattice constant, crystal density, thermal expansion coefficient, dielectric constant, and elastic constant, obey Vegard’s rule well Other parameters, eg, electronic‐band energy, lattice vibration (phonon) energy, Debye temperature, and impurity ionization energy, exhibit quadratic dependence upon the AlAs mole fraction However, some kinds of the material parameters, eg, lattice thermal conductivity, exhibit very strong nonlinearity with respect to x, which arises from the effects of alloy disorder It is found that the present model provides generally acceptable parameters in good agreement with the existing experimental data A detailed discussion is also given of the acceptability of such interpolated parameters from an aspect of solid‐state physics Key properties of the material parameters for use in research work and a variety of Al x Ga1−x As/GaAs device applications are also discussed in detail

GaAs, AlAs, and AlxGa1−xAs: Material parameters for use in research and device applications

Structure, thermodynamics, and electronic properties are predicted for a new low energy phase of carbon which contains planar sheets equally occupied by sp2 and sp carbon atoms. The isolated planar sheets have the same planar symmetry as do the layers in graphite (p6m) and can be formally viewed as resulting from the replacement of one‐third of the carbon–carbon bonds in graphite by –C 3/4 C– linkages. This material, called graphyne, is predicted to have a crystalline state formation energy of 12.4 kcal/mol carbon, which appears to be much lower than for any carbon phase which contains acetylenic groups as a major structural component. Based on the major structural reorganization required for graphitization and the observed high temperature stability of known model compounds, high temperature stability is predicted for graphyne. While graphyne will have similar mechanical properties as graphite, it is predicted to be a large bandgap semiconductor (Eg=1.2 eV) rather than a metal or semimetal. Based on this...

Structure‐property predictions for new planar forms of carbon: Layered phases containing sp2 and sp atoms

Kinetic of crystallization from the melt and chain folding in polyethylene fractions revisited: theory and experiment

Summary: Isoconversional kinetic analysis involves evaluating a dependence of the effective activation energy on conversion or temperature and using this dependence for making kinetic predictions and for exploring the mechanisms of thermally stimulated processes. The paper discusses major results obtained by the authors in the area of the isoconversional analysis of polymer kinetics over the past decade. It provides a brief introduction to isoconversional methods and surveys the impact made by isoconversional analysis in several application areas that include kinetic predictions, thermal degradation, crosslinking (curing), glass transition, and glass and melt crystallization. It is concluded that isoconversional analysis has been used broadly and fruitfully because it presents a fortunate compromise between the single-step Arrhenius kinetic treatments and the prevalent occurrence of processes whose kinetics are multi-step and/or non-Arrhenius.

An isoconversional method applies the Arrhenius equation to a narrow temperature region, ΔT related to a given extent of conversion.

Isoconversional Kinetic Analysis of Thermally Stimulated Processes in Polymers

A microscopic model for impurity uptake at a sharp crystal‐liquid interface during alloy solidification is presented in terms of the bulk properties of the liquid and solid phases. The results for stepwise growth and continuous growth at the same interface velocity differ quantitatively but exhibit the same qualitative features. A transition from equilibrium segregation to complete solute trapping occurs as the velocity surpasses the diffusive speed of solute in the liquid. The location of the transition varies little with equilibrium segregation coefficient, and a kinetic limit to solute trapping is found to be quite unlikely. Comparison is made with other models; critical differences are pointed out. Coupled with a growth velocity equation and with macroscopic heat‐ and solute‐diffusion equations, the model forms a complete description of one‐dimensional crystal growth. The steady‐state solution to this system is indicated for the case of a planar interface. The results are applied to describe regrowth from laser‐induced melting. Preliminary comparison with experiment is made. The steady‐state solution for thermal and impurity transport is suggested for use whenever detailed computer calculations are unavailable or are unnecessarily involved.

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Model for solute redistribution during rapid solidification

Treatise on solid state chemistry

One of the primary aims of materials science and engineering is to relate the macroscopic properties of solids to their structure. The structure includes both the electronic and the atomic structure.

Solid State Chemistry

Crystalline and noncrystalline solids

of Volume 1.- 1 Chemical Bonds in Solids.- 1. Why Solids Are Different from Molecules.- 1.1. Quantum Theory of Chemical Bonds.- 1.2. The Five Solid Types.- 1.3. Bonds and/or Bands?.- 2. Crystal Structures and Cohesive Energies of the Elements.- 2.1. Valence Groupings.- 2.2. Shell Effects.- 2.3. Transition Series.- 3. Binary Compounds and Alloys.- 3.1. Minerals.- 3.2. Semiconductors.- 3.3. Intermetallic Solutions.- 4. Chemical Bonding and Physical Properties.- 4.1. Classical Polarizabilities.- 4.2. Dispersion.- 4.3. Covalent and Ionic Energies.- 4.4. Chemical Trends in Physical Properties.- 5. Summary.- References.- 2 Energy Bands.- 1. Introduction.- 1.1. Historical Remarks.- 1.2. The Independent-Electron Approximation.- 2. Energy Bands in General.- 3. The Classical Descriptions of Energy Bands in Periodic Systems.- 3.1. Introduction.- 3.2. Two Classical Limits-Tight Binding and Nearly Free Electron.- 3.3. Tight Binding Theory.- 3.4. Wannier Functions.- 3.5. Nearly-Free-Electron Theory.- 3.6. Pseudopotentials.- 3.7. The Cellular Method.- 3.8. Orthogonalized Plane Wave, Augmented Plane Wave, and Related Methods.- 4. Approximations, Interpolations, Perturbations.- 4.1. Introduction.- 4.2. Moment Methods.- 4.3. Nearly-Free-Electron Perturbation Theory.- 4.4. The k * p Method.- 4.5. Small-k Expansions for KKR Theory.- 5. Some Relevant Experiments.- 5.1. Introduction.- 5.2. Soft X-Ray Emission and Absorption.- 5.3. Optical Spectroscopy.- 5.4. Fermi Surface Analysis.- 6. Typical Band Structures.- 6.1. Introduction.- 6.2. Simple Metals.- 6.3. Alkali Halides.- 6.4. Group IV Semiconductors.- 6.5. The III-V and II-VI Semiconductors.- 6.6. Silicon Dioxide.- 6.7. Transition Metals.- 6.8. Transition Metal Compounds.- 7. Disordered Solids.- 7.1. Introduction.- 7.2. Definition of Problems.- 7.3. The Density of States in an Alloy.- 7.4. The Anderson Problem.- 7.5. Topological Disorder.- 7.6. Applications.- 8. Conclusion.- Acknowledgments.- References.- 3 Factors Controlling the Formation and Structure of Phases.- 1. Introduction.- 2. Practical Prediction of Phase Stability.- 2.1. Metals: Use of Thermodynamic Data.- 2.2. Valence Compounds: Use of Crystal Chemical Knowledge.- 3. General Structural Consequences of Bonding Types.- 3.1. Ionic Crystals.- 3.2. Compounds with Saturated Covalent Bonds.- 3.3. Metallic Phases.- 3.4. A Priori Separation of Structure Types.- 4. Atomic Size and Structural Constraint.- 5. Factors Influencing the Stability of Crystal Structures.- 5.1. Electrochemical Factor.- 5.2. Geometric Effects.- 5.3. Energy Band Effects.- 5.4. Environmental Factors.- 6. Distortions of Crystal Structures.- 6.1. Distortions Arising from Cation-Cation Bonds.- 6.2. Jahn-Teller Distortions.- 6.3. Spin-Orbit Coupling Distortions.- 6.4. Magnetic Exchange Energies.- 6.5. Mechanical Instability.- 7. Epilogue.- Appendix-Structure Diagrams.- Acknowledgments.- References.- 4 Structure and Composition in Relation to Properties.- 1. Magnetic Behavior.- 1.1. Introduction.- 1.2. The 3d Transition Elements.- 1.3. Rare Earth Metals.- 1.4. Role of Local Atomic Environment Regarding Development of Atomic Moments and Long-Range Order.- 1.5. Directional Ordering and Magnetic Anisotropy.- 1.6. Magnetic Oxides.- 1.7. Magnetic Semiconductors.- 1.8. Linear and Two-Dimensional Magnetic Behavior.- 1.9. Amorphous Magnetic Materials.- 1.10. Summary.- 2. Superconducting Behavior.- 2.1. Introduction.- 2.2. The Cr3Si (?-W) and Transition Metal Nitride and Carbide Phases. Electron Concentration and Lattice Instability.- 2.3. Role of Stoichiometry and Atomic Order.- 2.4. Metastable Superconducting Phases.- 2.5. Paramagnetic Impurities in Superconductors.- 2.6. Ternary Superconducting Chalcogenides.- 2.7. Superconductivity of Degenerate Semiconductors.- 2.8. Summary.- 3. Dielectric Materials.- 3.1. Ferroelectrics.- 3.2. Piezoelectrics.- 3.3. Nonlinear Optical Materials.- 3.4. Electrooptic and Pyroelectric Materials.- 3.5. Summary.- 4. Mechanical Behavior.- 4.1. Introduction.- 4.2. Elastic Behavior.- 4.3. Plastic Behavior.- 4.4. Summary.- Acknowledgments.- References.- 5 Introduction to Chemical and Structural Defects in Crystalline Solids.- 1. Introduction.- 2. Point Defects.- 3. Dislocations.- 4. Planar Defects.- 5. Volumetric Defects.- Acknowledgments.- References.- 6 Defect Equilibria in Solids.- 1. Introduction.- 1.1. Native Defects.- 1.2. Law of Mass Action and Point Defects.- 1.3. Electronic Defects.- 1.4. Energetics of Defect Formation.- 2. Native Defects.- 2.1. Defect Equilibria in Elemental Crystals.- 2.2. Defect Equilibria in Binary Compounds.- 2.3. Nonstoichiometry-Equilibria with External Phases.- 2.4. Ionization of Defects.- 2.5. Relationship between Mass Action Law and Statistical Thermodynamics.- 2.6. Defect Interactions.- 3. Multicomponent Systems.- 3.1. Equilibria Involving Foreign Atoms.- 3.2. Multicomponent Compounds.- 4. Extended Defects.- Acknowledgment.- References.- 7 Characterization of Solids-Chemical Composition.- 1. Introduction.- 2. Current Capability for Determination of Chemical Composition.- 2.1. Introduction.- 2.2. General Over iew.- 2.3. Analytical Techniques: Present Status.- 2.4. Precision and Sensitivity of Analytical Techniques.- 3. Application of Current Techniques to Characterization of Materials.- 3.1. Characterization of Major Phase.- 3.2. Characterization of Minor Phases and Impurities.- 3.3. Characterization of Surfaces.- 4. Utilization of Existing Techniques.- 4.1. Literature Examples.- 4.2. Factors Determining Use.- Acknowledgments.- References.- 8 Structural Characterization of Solids.- 1. Introduction.- 2. Structural Characterization by Optical Techniques.- 2.1. Morphology.- 2.2. Bulk Optical Properties.- 2.3. Scattering Studies.- 2.4. Surface Characterization.- 2.5. Particle Size and Shape.- 3. Structural Characterization by X-Ray Diffraction.- 3.1. X-Ray Powder Methods.- 3.2. Single-Crystal X-Ray Methods.- 3.3. Temperature and Pressure Experiments.- 3.4. X-Ray Topography and Interferometry.- 4. Electron Methods for Materials Characterization.- 4.1. Electron Microscopy.- 4.2. Electron Diffraction.- 4.3. Scanning Electron Microscopy.- 5. Neutron Scattering from Solids.- 5.1. Neutron Sources.- 5.2. Interactions with Matter.- 5.3. Structure Analysis with Neutrons.- 5.4. Magnetic Structure Analysis.- 5.5. Lattice and Spin Dynamics.- 6. Spectroscopy and Local Symmetry.- 6.1. Absorption Spectra in the Visible Range.- 6.2. Infrared Absorption Spectroscopy.- 6.3. Raman Spectra.- 6.4. Soft X-Ray Spectra.- 6.5. Electron Spin Resonance.- 6.6. Nuclear Magnetic Resonance.- 6.7. Mossbauer Effect.- 6.8. Electron Spectroscopy.- 6.9. Acoustic Spectroscopy.- 7. Physical Properties as Characterization Tools.- 7.1. Introduction.- 7.2. Some Crystal Physical Generalizations.- 7.3. Dielectric Measurements.- 7.4. Electrical Characterization of Solids.- 7.5. Magnetic Measurements.- 7.6. Calorimetric Measurements.- Acknowledgment.- References.

Norman Bruce Hannay

Papers

Treatise on solid state chemistry

Solid State Chemistry

Crystalline and noncrystalline solids

The Chemical Structure of Solids