Defect Reduction by Thermal Cyclic Growth in GaAs Grown on Si by Movpe

1993 ◽  
Vol 325 ◽  
Author(s):  
W. KÜrner ◽  
R. Dieter ◽  
K. Zieger ◽  
F. Goroncy ◽  
A. DÖrnen ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Dislocation Density ◽  
Lattice Mismatch ◽  
Gaas Layer ◽  
Defect Reduction ◽  
Thermal Expansion Coefficients ◽  
Related Defect ◽  
Expansion Coefficients ◽  
The Difference

AbstractThe growth of GaAs epilayers on Si should combine the advantages of both materials. The lattice mismatch and the difference in thermal expansion coefficients, however, result in the yet unsolved problems of high dislocation density and thermal stress in the GaAs layer. Recently, considerable improvements have been achieved by a ‘thermal cyclic growth’ (TCG) process. In this study we focus on the reduction of high defect concentration and dislocation density. The improvement of the epilayer quality is verified by DLTS, PL and DCXD. Results of TEM and DLTS measurements lead to the identification of a dislocation related defect.

Thermal Expansion Coefficients and Thermal Stresses in an Aligned Short Fiber Composite With Application to a Short Carbon Fiber/Aluminum

1985 ◽  
Vol 52 (4) ◽  
pp. 806-810 ◽  
Author(s):  
Y. Takao ◽  
M. Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Carbon Fiber ◽  
Thermal Stresses ◽  
Short Fiber ◽  
Short Carbon Fiber ◽  
Thermal Expansion Coefficients ◽  
Equivalent Inclusion Method ◽  
Expansion Coefficients ◽  
Short Carbon

A formulation to compute the effective thermal expansion coefficients (αc) of an anisotropic short fiber-reinforced composite and the thermal stress (σ) induced in and around the fiber is developed. The formulation is based on the Eshelby’s equivalent inclusion method. Main emphasis is placed on short Carbon fiber/Aluminum. The thermal stress due to a uniform temperature rise ΔT is computed at points just outside the fiber. The effects of various parameters on αc and σ are also investigated.

Athermal Motion of Grain Boundaries, Twins and Triple Junctions in Zn

2004 ◽  
Vol 467-470 ◽  
pp. 801-806 ◽  
Author(s):  
Vera G. Sursaeva
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Triple Junction ◽  
Triple Junctions ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
The Difference ◽  
The Individual ◽  
Individual Grains

When a bicrystal or polycrystal are subjected to a change in temperature, the individual responses of the two adjoining crystals may differ in a manner, which tends to produce a dilatational mismatch along grain boundaries. If compatibility is to be retained along the interface, an additional set of stresses must then be generated in order to conserve this compatibility. ‘Compatibility stresses’ will also be generated whenever a polycrystal is heated or cooled and the thermal expansion coefficients of the individual grains are different due to thermal expansion anisotropy. In such cases adjacent grains will attempt to change dimensions and develop mismatches by amounts controlled by the parameter Δa*ΔΤ, where Δa is the difference between the thermal expansion coefficients in the appropriate directions, and ΔΤ is the temperature change. These ‘compatibility stresses’ may be relieves if grain boundary motion, triple junction migration and grain growth are possible. These ‘compatibility stresses’ may play important role in the kinetic behavior of the microstructure ranging from influencing the behavior of lattice dislocations near the grain boundaries to promoting grain boundary and triple junction dragging or moving. The motion of the ‘special’ grain boundaries, triple junctions with ‘special’ grain boundaries and twins under the influence of internal mechanical stresses is the main subject of this paper.

Thermal Stress in a Coated Short Fiber Composite

1987 ◽  
Vol 109 (1) ◽  
pp. 59-63 ◽  
Author(s):  
Hiroshi Hatta ◽  
Minoru Taya
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Stress Field ◽  
Thermal Stresses ◽  
Fiber Composite ◽  
Short Fiber ◽  
Critical Parameters ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Short Fiber Composite

When a coated short fiber composite is subject to temperature change, thermal stresses in and around the coated fibers are induced due to the mismatch of thermal expansion coefficients of the constituents. The problem of the above thermal stresses in a coated short fiber composite is solved by using the Eshelby’s equivalent inclusion method under the assumption of thin coating. A parametric study is then conducted to examine the effect of thermo-mechanical properties of the coating on the stress field in an and around a coated short fiber. It is found in this study that critical parameters influencing the thermal stress field are the thermal expansion coefficients of the fiber and coating.

Study of the Ti-Mn-Al-Si-O-S Complex Inclusions Inducing Intragranular Acicular Ferrite

2012 ◽  
Vol 535-537 ◽  
pp. 620-627 ◽  
Author(s):  
Chengwei Yang ◽  
Min Jiang ◽  
Xinhua Wang ◽  
Tie Ou
Keyword(s):  
Thermal Expansion ◽  
Confocal Laser ◽  
Complex Inclusion ◽  
Inclusion Formation ◽  
The Core ◽  
Thermal Expansion Coefficients ◽  
Intragranular Acicular Ferrite ◽  
Expansion Coefficients ◽  
The Difference ◽  
Confocal Laser Microscope

High temperature confocal laser microscope, FE-SEM-EDS and EPMA were utilized to study the Ti-Mn-Al-Si-O-S complex inclusion inducing IAF in Ti deoxidized steel. FactStage was also used to calculate the thermodynamics of inclusion formation. It was demonstrated that when the cooling rate is fixed to 5°C/s, IAF can be induced by complex inclusions which act as the core of IAF at 609°C. Microstructure of the complex inclusions is complicated. These inclusions are consisted of the TiOx-MnO core which is surrounded by MnO-Al2O3-SiO2 complex inclusions and small amount of MnS. The reason that Ti-Mn-Al-Si-O-S complex inclusions can induce IAF is that a Mn-depleted zone is formed by the core TiOx-MnO and the MnS around it. Meanwhile, the difference between MnO-Al2O3-SiO2 and austenite thermal expansion coefficients is tremendous is another principle element for the IAF formation.

Thermal Stress Analysis of a Bi-Material Layered Structure

2010 ◽  
Vol 450 ◽  
pp. 161-164 ◽  
Author(s):  
Shiuh Chuan Her ◽  
Chin Hsien Lin ◽  
Shun Wen Yeh
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Dissimilar Materials ◽  
Beam Theory ◽  
Layered Systems ◽  
Thermal Expansion Coefficients ◽  
Parametric Studies ◽  
Expansion Coefficients ◽  
Good Agreement

Thermal stress induced by the mismatch of the thermal expansion coefficients between dissimilar materials becomes an important issue in many bi-layered systems, such as composites and micro-electronic devices. It is useful to provide a simple and efficient analytical model, so that the stress level in the layers can be accurately estimated. Basing on the Bernoulli beam theory, a simple but accurate analytical formulation is proposed to evaluate the thermal stresses in a bi-material beam. The analytical results are compared with finite element results. Good agreement demonstrates that the proposed approach is able to provide an efficient way for the calculation of the thermal stresses. It is shown that thermal stresses are linear proportion to the ratio of thermal expansion coefficients between the two materials. Parametric studies reveal that thermal stresses in each layer are decreasing with the increase of thickness, and are increasing with the increase of Young’s modulus ratio between the two materials.

Thermodynamics of Epitaxial Ferroelectric Films.

1995 ◽  
Vol 401 ◽  
Author(s):  
S. B. Desu ◽  
V. P. Dudkevich ◽  
P. V. Dudkevich ◽  
I. N. Zakharchenko ◽  
G. L. Kushlyan
Keyword(s):  
Thermal Expansion ◽  
Phase Transitions ◽  
Misfit Dislocations ◽  
Ferroelectric Films ◽  
Growth Stresses ◽  
Substrate Interaction ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
The Difference ◽  
Film Substrate

AbstractThe problem of phase transitions and physical properties of the BaTiO3-type films on the (001) single-crystal substrates of the cubic syngony was solved in the limits of the Landau- Devonshire thermodynamics. The thermoelastic film-substrate interaction caused by the difference between thermal expansion coefficients was strictly taken into consideration. The model was based on the following assumptions: 1) the film is closely conjugated with the substrate; 2) the film is sufficiently “thick”to find itself unstrained at the growth temperature Ts, ( growth stresses were compensated by misfit dislocations ), and 3) the film is sufficiently “thin, and the stresses arising at the temperatures T>Ts may be considered to be uniform.

A Study on Metal-Ceramic Thermal Expansion Compatibility

2014 ◽  
Vol 216 ◽  
pp. 85-90
Author(s):  
Marian Miculescu ◽  
Mihai Branzei ◽  
Florin Miculescu ◽  
Daniela Meghea ◽  
Marin Bane
Keyword(s):  
Thermal Expansion ◽  
Bonding Strength ◽  
Linear Thermal Expansion ◽  
Metal Bonding ◽  
Thermal Expansion Coefficients ◽  
Metal Ceramic ◽  
Thermal Compatibility ◽  
Expansion Coefficients ◽  
The Difference ◽  
Dental Applications

Push rod method for determining linear thermal expansion using vertical differential dilatometer was used in the study of the thermal compatibility of metal-ceramic systems for dental applications. The purpose of this study consisted in evaluating the effectiveness of dental coating by determining the ceramic metal bonding strength of metal-ceramic couples (Ni-Cr and Co-Cr alloy coated with dental ceramic) and correlation with the difference of linear thermal expansion coefficients of metals and ceramics.

Thermal Expansion of GaN at Low Temperatures - a Comparison of Bulk and Homo- and Heteroepitaxial Layers

1999 ◽  
Vol 595 ◽  
Author(s):  
Verena Kirchner ◽  
Heidrun Heinke ◽  
Sven Einfeldt ◽  
Detlef Hommel ◽  
Jaroslaw Z. Domagala ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Low Temperatures ◽  
Lattice Mismatch ◽  
Thermal Strain ◽  
Chemical Vapor ◽  
Thermally Induced ◽  
Thermal Expansion Coefficients ◽  
Bulk Gan ◽  
Expansion Coefficients ◽  
Heteroepitaxial Layers

AbstractThe thermal expansion of different GaN samples is studied by high-resolution Xray diffraction within the temperature range of 10 to 600 K. GaN bulk crystals, a homoepitaxial layer and different heteroepitaxial layers grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were investigated. Below 100 K the thermal expansion coefficients (TEC) were found to be nearly zero which has to be taken into account when estimating the thermal strain of GaN layers in optical experiments commonly performed at low temperatures. The homoepitaxial layer and the underlying GaN substrate with a lattice mismatch of –6×10−4 showed identical thermal expansion. The comparison between the temperature behavior of lattice parameters of heteroepitaxial layers and bulk GaN points to a superposition of thermally induced biaxial strain and compressive hydrostatic strain.

Intrinsic and Thermal Stress in Gallium Nitride Epitaxial Films

1996 ◽  
Vol 449 ◽  
Author(s):  
J. W. Ager ◽  
T. Suski ◽  
S. Ruvimov ◽  
J. Krueger ◽  
G. Conti ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Thermal Expansion ◽  
Thermal Stress ◽  
Growth Temperature ◽  
Room Temperature ◽  
Intrinsic Stress ◽  
Experimental Methodology ◽  
Thermal Expansion Coefficients ◽  
Si Doped ◽  
Expansion Coefficients

ABSTRACTStrain in GaN epitaxial layers at room temperature is measured with three complementary methods: Raman spectroscopy (via shifts of phonon frequencies), low temperature photoluminescence (via shifts of band-edge luminescence), and X-ray diffraction (via shifts in lattice spacings). GaN films grown on the c-plane of sapphire tend to be in compression. Increasing the Si-dopant concentration (up to 1019 cm−3) is observed to add compressive strain to the layer. Axially resolved measurements obtained by micro-Raman in 4 μm thick Si-doped films reveal strain relaxation toward the sample surface at Si concentrations above 1018 cm−3. Mg- and Si-doped GaN films on SiC substrates are found to be in tension. An experimental methodology is presented that separates two contributions to the room temperature residual stress in GaN epilayers: (1) the thermal stress due to differences in the thermal expansion coefficients of the epilayer and substrate and (2) the intrinsic stress, which is influenced by the growth conditions. We measure stress as a function of temperature up to 325 C, about one-third of the growth temperature, by monitoring the frequency of the E2 phonon mode by Raman spectroscopy. A high-quality bulk single crystal of GaN is used as a strain-free standard. Over this temperature range, most layers behave elastically; the observed stress trends are well-fit by a thermal expansion model using previous reported values of the thermal expansion coefficients of GaN and the substrates. The intrinsic stress states at the growth temperature for films grown on sapphire and SiC are predicted to be tensile and compressive, respectively, in agreement with the a-plane lattice coefficient mismatch.

Thermal Expansion Behavior of ZnSe and ZnS0.03Se0.97 Epilayers on GaAs at Temperatures in the Range, 25°C - 250°C

1994 ◽  
Vol 340 ◽  
Author(s):  
J. R. Kim ◽  
R. M. Park ◽  
K. S. Jones
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Thermal Expansion Behavior ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Lattice Matched

ABSTRACTThe thermal expansion behavior of ZnSe and ZnS0.03Se0.97 epilayers grown on GaAs has been investigated using high resolution X-ray diffraction at temperatures between room temperature and the growth temperature. The lattice parameters perpendicular and parallel to the surface were measured with the Bond's method. The lattice mismatch for a partially relaxed ZnSe layer was Δa(⊥)/a =2300 ppm and Δa(‖)/a = 2600 ppm at room temperature(R.T.) and Δa (⊥)/a =3600 ppm and Δa(‖)/a =2400 ppm at 250°C. For ZnS0.03Se0.97 which is almost lattice matched at R.T. to GaAs, Δa(⊥)/a =200 ppm, Δa(⊥)/a =20ppmatR.T. and Δa(⊥)/a =1400ppm, Δa(⊥)/a =50ppm at 250°C. The relaxed lattice constants were evaluated and the thermal expansion coefficients of relaxed ZnSe layers were found to vary from 7.8*10−6/°C at room temperature to 12.2*10−6/°C at 250°C and for ZnS0.03Se0.97 layers the variation was from 7.5*10−6/°C at R.T. to 11.7*10−6/°C at 250°C.

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