Thermal Expansion of β-Sic, Gap and Inp

1995 ◽  
Vol 410 ◽  
Author(s):  
Robert R. Reeber ◽  
Kai Wang
Keyword(s):  
Thermal Expansion ◽  
Indium Phosphide ◽  
Gallium Phosphide ◽  
Electronic Devices ◽  
Epitaxial Films ◽  
Interatomic Potentials ◽  
Harmonic Model ◽  
Melting Points ◽  
Model Calculations ◽  
Semi Empirical

ABSTRACTThermal expansion is important for predicting residual stresses in epitaxial films, composites and electronic devices as well as for providing information relevant to an understanding of interatomic potentials and the equation of state of materials. Model calculations have many assumptions, both inherent and implicit, and have difficulty accurately representing thermal expansion at high temperatures and pressures. We utilize a semi-empirical quasi-harmonic model to evaluate available data for β-silicon carbide, gallium phosphide and indium phosphide. The model allows prediction of the thermal properties of these semiconductors from near 0 K to the vicinity of their melting points. The approach, consisting of a simplified frequency spectrum with several Einstein terms, provides a convenient mathematical method where a minimum of empirical parameters represent the thermal property.

Thermal Expansion Of GaN And Ain

1997 ◽  
Vol 482 ◽  
Author(s):  
Kai Wang ◽  
Robert R. Reeber
Keyword(s):  
Experimental Data ◽  
Residual Stress ◽  
Thermal Expansion ◽  
Lattice Parameter Data ◽  
Equations Of State ◽  
Lattice Parameter ◽  
Epitaxial Films ◽  
Residual Stress Distribution ◽  
Interatomic Potentials ◽  
Semiempirical Models

AbstractThe temperature dependence of the thermal expansion and the bulk modulus are critical for predicting the residual stress distribution in epitaxial films and provides information relevant for interatomic potentials and equations of state. The thermal expansions of aluminum nitride (AIN) and gallium nitride (GaN) are calculated with two models that employ the limited elastic and lattice parameter data. These semiempirical models allow prediction of the thermal expansions to higher temperatures. Calculated results are compared with experimental data.

Lattice Parameters and Thermal Expansion of Important Semiconductors and Their Substrates

2000 ◽  
Vol 622 ◽  
Author(s):  
Robert R. Reeber ◽  
Kai Wang
Keyword(s):  
Thermal Expansion ◽  
Crystal Growth ◽  
First Principles ◽  
Electronic Devices ◽  
Growth Conditions ◽  
Epitaxial Films ◽  
Lattice Parameters ◽  
Device Design ◽  
Properties Of Materials ◽  
Better Than

ABSTRACTThermal expansion and lattice parameters are useful thermophysical properties of materials. A knowledge of their temperature dependence is essential for optimizing device design and crystal growth conditions while minimizing the residual stress in epitaxial films and electronic devices. Currently first principles theory can predict lattice parameters to 0.01%. Information required for device design and thin film crystal growth requires improvements two to three orders of magnitude better than this. Available experimental results from our work and the literature will be reviewed in terms of a high temperature predictive model. Tables of thermal expansion and lattice parameters for AlN, GaN, 6H-SiC, β-SiC, MgO, Al2O3, ZnO and GaAs are provided.

scholarly journals Twisted Fibers Can Have an Adjustable Thermal Expansion

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 456
Author(s):  
Donghua Yue ◽  
Liming Wei
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Carbon Fibers ◽  
Expansion Coefficient ◽  
Twist Angle ◽  
Capacitive Sensor ◽  
Model Calculations ◽  
Thermal Expansion Coefficients ◽  
Geometrical Features ◽  
Expansion Coefficients

In this paper, a device with high accuracy capacitive sensor (with the error of 0.1 micrometer) is constructed to measure the axial thermal expansion coefficent of the twisted carbon fibers and yarns of Kevlar. A theoretical model based on the thermal elasticity and the geometrical features of the twisted structure is also presented to predict the axial expansion coefficient. It is found that the twist angle, diameter and pitch have remarkable influences on the axial thermal expansion coefficients of the twisted carbon fibers and Kevlar strands, and the calculated results are in good agreement with experimental data. We found that, with the increase of the twist angle, the absolute value of the axial thermal expansion coefficient increases. For the Kevlar samples, the expansion coefficient will grow by about 46% when the twist angle increases from 0 to 25 degrees, while the carbon fiber samples will grow by about 72% when the twist angle increases from 0 to 35 degrees. The experimental measurements and the model calculations reveal important properties of the thermal expansion in the twisted structures. Most notably, the expansion of the strand during heating or cooling can be zero when the twist angle is around β = arcsin(αL/αT)^1/2, where β denotes twist angle of the strand and αL, αT are the longitute and the transverse thermal expansion coefficient of the strand, respectively. According to the present experiments and analyses, a method to control the axial thermal expansion coefficient of this new kind of twisted structure is proposed. Moreover, the mechanism of this tunable thermal expansion is discussed. Based on the model, a method that can be used to rectify the thermal expansion properties of the twist structures is established. This may be a new way of fabricating zero expansion composite materials in the future.

scholarly journals A Calculation Model of the General Theory of Interaction Potentials for Stoichiometric Lanthanide Type Crystals: Applications to the Cs2KLnCl6 System

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andres Soto ◽  
Shanavas Shajahan ◽  
Roberto Acevedo
Keyword(s):  
General Theory ◽  
Chemical Elements ◽  
Current Model ◽  
Theoretical Models ◽  
Calculation Model ◽  
Lanthanide Ions ◽  
Interaction Potentials ◽  
Model Calculations ◽  
Advantages And Disadvantages ◽  
Semi Empirical

AbstractThis article aims to develop a generalized model calculation model to be applicable to the general theory of interaction potentials with reference to the stoichiometric elpasolite type crystals. In this study, we have chosen to report both a theoretical model and a calculation strategy to undertake semi empirical calculations of thermodynamic properties, such as reticular energies and heats of formation for the series of systems such as: Cs2KLnCl6. We have also carried out quite a number of calculations for a variety of systems such as: Cs2NaLnF6, Cs2NaLnCl6, Cs2NaLnBr6, Rb2NaLnF6and Cs2KLnF6 in the Fm3m space group since we aim to check the strengths and weaknesses of our model calculations. We have analyzed a substantial number of approximate theoretical models and have carried a formidable amount of computing simulations to estimate the reticular energies and the corresponding heat of formation for these type of crystal using a semi empirical model. We made use of the thermodynamic cycles of Born-Haber so as to get a broad view with reference to the accuracy of our semi empirical theoretical models. The problem itself is quite challenging since we have focused our attention upon trivalent lanthanide ions $$L{n}^{+3}$$Ln+3 in the first inner transition series of the chemical elements: (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). There are a significant amount of outstanding research works published in the literature with reference to structural analysis, one photon spectroscopy, vibrionic intensity model calculations and generalized models to deal with these kind of complex crystals. The calculated energy values associated with these observables seems to be most reasonable, and these follow the expected trends, as may be expected on both theoretical and experimental grounds. Both, the advantages and disadvantages of the current model calculations, have been tested against other previous calculations performed for this type of complex systems. It is of a paramount importance, the results obtained and reported in this article with regards to convergence tests as well as some master equations derived to account for the various contributions to the total energy. The Born-Mayer-Buckingham potential is carefully examined with reference to these lanthanide type crystals Cs2KLnCl6. Finally but not at last, the most likely sources for improvement are carefully discussed in this work. We strongly believe that there is enough room for improvement and have therefore initiated a new research program of activities tackling systems of well-known optical and structural properties.

The Electronic Properties of Epitaxial Calcium Fluoride-Silicon Structures

1985 ◽  
Vol 54 ◽  
Author(s):  
T. P. Smith ◽  
J. M. Phillips ◽  
R. People ◽  
J. M. Gibson ◽  
L. Pfeiffer ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Material Properties ◽  
Calcium Fluoride ◽  
Minority Carrier ◽  
Electronic Devices ◽  
Epitaxial Films ◽  
High Quality ◽  
Silicon Structures

ABSTRACTThe characterization of electronic devices using epitaxial CaF2 on Si is described. In addition, the growth and annealing techniques used to obtain high quality epitaxial films are discussed. In particular, the results of using rapid thermal annealing to improve the epitaxial quality of CaF2 films are presented in detail.The electronic and electrical properties of these structures are very promising. Epitaxial CaF2 films with breakdown fields as high as 3 × 106 V/cm and interface trap densities as low as 7 × 1010cm-2eV-1 have been fabricated. In addition, minority carrier dominated trapping has been observed at the CaF2 /Si interface. Finally, the material properties of these structures, as determined by Rutherford backscattering, channeling, and electron microscopy, are discussed and correlated with their electronic properties.

A comparison between two semi-empirical interatomic potentials

1977 ◽  
Vol 10 (16) ◽  
pp. L589-L592 ◽  
Author(s):  
O Vallee ◽  
P Ranson ◽  
P Combis ◽  
J Chapelle
Keyword(s):  
Interatomic Potentials ◽  
Semi Empirical

scholarly journals The Electronic Structure of Organometallic Complexes Involving f-Electrons, II Magnetic Susceptibility and Crystal Field Splitting of Uranium(IV)-tetracyclopentadienide

1976 ◽  
Vol 31 (1) ◽  
pp. 12-21 ◽  
Author(s):  
H.-D. Amberger ◽  
R. D. Fischer ◽  
B. Kanellakopulos
Keyword(s):  
Magnetic Susceptibility ◽  
Crystal Field ◽  
Organometallic Complexes ◽  
Model Calculations ◽  
First Order ◽  
Energy Part ◽  
Order Of Magnitude ◽  
5F Electrons ◽  
Semi Empirical ◽  
Empirical Approaches

Some significant features of the low-energy part of the crystal field (=CF) splitting pattern of the organometallic 5f2-system (η5-C5H5)4U(IV) can be deduced from the temperature dependence of the magnetic susceptibility which has been measured on polycrystalline samples between 1.1 and 298 K. The results of model calculations performed independently on the basis of three different semi-empirical approaches are compatible with the deductions from the experiments and allow estimates of the sign and order of magnitude of quantities like the CF-splitting parameters B40 and B60 viz. the (averaged) angular overlap parameters eσ and eπ„ and of the valence state ionisation potential of the 5f-electrons. Anticipating a rather weakly perturbed tetrahedral CF, the observed magnetic properties may be satisfactorily simulated if the six lowest-lying first-order CF-states and one common scaling factor are accounted for

Electron-Magnetic, Lattice and Magnon Grüneisen Parameters of Iron and Nickel: Results from Thermal Expansion Measurements and Model Calculations

1998 ◽  
Vol 12 (04) ◽  
pp. 449-470 ◽  
Author(s):  
Goutam Dev Mukherjee ◽  
C. Bansal ◽  
Ashok Chatterjee
Keyword(s):  
Thermal Expansion ◽  
Theoretical Model ◽  
Cell Design ◽  
Model Calculations ◽  
Grüneisen Parameters ◽  
Gruneisen Parameters ◽  
Capacitance Dilatometer

Thermal expansion measurements have been performed on nickel and iron using a three terminal capacitance dilatometer with a new cell design and a theoretical model has been developed to obtain the electron-magnetic, lattice and magnon contributions to thermal expansion and corresponding Grüneisen parameters.

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