Epitaxial Island Growth and the Stranski-Krastanow Transition

2001 ◽  
Vol 696 ◽  
Author(s):  
A.G. Cullis ◽  
D.J. Norris ◽  
T. Walther ◽  
M.A. Migliorato ◽  
M. Hopkinson
Keyword(s):  
Surface Layer ◽  
Driving Force ◽  
Strain Energy ◽  
Atomistic Simulations ◽  
Wetting Layer ◽  
Island Growth ◽  
Critical Wetting ◽  
Elemental Segregation ◽  
Good Agreement ◽  
The Way

AbstractThe way in which the Stranski-Krastanow epitaxial islanding transition can be controlled by strain due to elemental segregation within the initially-formed flat ‘wetting’ layer is examined in detail. Experimentally measured critical ‘wetting’ layer thicknesses for the InxGa1−xAs/GaAs system (x = 0.25 - 1) are demonstrated to show good agreement with values calculated using a segregation model. The strain energy associated with the segregated surface layer is determined for the complete range of deposited In concentrations using atomistic simulations. The segregation-mediated driving force for the Stranski-Krastanow transition is considered to be important also for all other epitaxial systems exhibiting the transition.

Effects of Minimizing the Driving Force for Epitaxy in the Ge/Si(001) System

1993 ◽  
Vol 312 ◽  
Author(s):  
P. O. Hansson ◽  
E. Bauser ◽  
M. Albrecht ◽  
H. P. Strunk
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Interfacial Energy ◽  
Driving Force ◽  
Strain Energy ◽  
Driving Forces ◽  
Two Dimensional ◽  
Island Growth ◽  
Dimensional Growth ◽  
A New Technique

AbstractA new technique for Ge/Si heteroepitaxy from the solution, referred to as interfacial energy epitaxy, produces Ge layers with atomically abrupt interfaces to Si and permits monolayer-controlled growth at temperatures up to 937°C. The initial driving force for epitaxy comes from interfacial energy differences between Ge, Si, and the solvent or growth mediator, whose surface free energy has to be smaller than that of Ge. A superheating of the growth solution partly out-balances this driving force, which allows us to minimize the total driving force for epitaxy. Two-dimensional growth results. Subsequent faceting and pseudomorphic island growth manifest additional driving forces for epitaxy, which may be due to interfacial- and strain energy gain.

The Behaviour of Multiple Loops in Torsion

1988 ◽  
Vol 15 (3) ◽  
pp. 149-156 ◽  
Author(s):  
R. A. Cavina ◽  
N. E. Waters
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Vertical Axis ◽  
Experimental Measurements ◽  
Complementary Strain ◽  
Radial Axis ◽  
Strain Energy Method ◽  
Good Agreement

The angular stiffness of a multiple looped span, subject to rotation about a vertical axis (torsion) and also to rotation about a horizontal or radial axis (mesio-distal tilt), have been derived using the complementary (strain) energy method. Experimental measurements on enlarged models were in good agreement with the values calculated from the theoretical relationships obtained. The variations in angular stiffness resulting from changes in the loop height, width, and position of clinical sized loops are discussed.

Crack Driving Force in Anisotropic Media due to Non-Elastic Deformation

2004 ◽  
Vol 261-263 ◽  
pp. 75-80
Author(s):  
G.H. Nie ◽  
H. Xu
Keyword(s):  
Elastic Deformation ◽  
Driving Force ◽  
Strain Energy ◽  
Elastic Stress ◽  
Complex Function ◽  
Crack Driving Force ◽  
Special Cases ◽  
Degree Of Anisotropy ◽  
Minimum Strain Energy ◽  
Orthotropic Media

In this paper elastic stress field in an elliptic inhomogeneity embedded in orthotropic media due to non-elastic deformation is determined by the complex function method and the principle of minimum strain energy. Two complex parameters are expressed in a general form, which covers all characterizations of the degree of anisotropy for any ideal orthotropic elastic body. The stress acting on the long side of ellipse can be considered as a crack driving force and applied in failure and fatigue analysis of composites. For some special cases, the resulting solutions will reduce to the known results.

scholarly journals From 'Politics in Command' to 'Economics in Command': A Discourse Analysis of China's Transformation

2005 ◽  
Vol 18 ◽  
pp. 65-87
Author(s):  
Li Xing
Keyword(s):  
Discourse Analysis ◽  
Communist Party ◽  
Driving Force ◽  
Chinese Communist Party ◽  
Discourse Theory ◽  
Political Arena ◽  
Chinese Revolution ◽  
Political Project ◽  
The Way

This article proposes a framework for understanding the way the Chinese Revolution emerged, developed and achieved power (1921-49), then further consolidated in the period of socialist 'uninterrupted revolution' (1949-77) and was finally abandoned by the post-Mao regime (1977 to the present). This analysis is based on a perspective of discourse theories framed in historically new forms of political, social and ideological relations. In other words, it attempts to conceptualize the transformation of China and the Chinese Communist Party by analysing the role of ideological discourses (arguments and interpretations) and the cognitive elements (beliefs, goals, desires, expertise, knowledge) as the driving-force behind societal transformations. The discourse theory applied here – logocentrism and econocentrism – also serves both as a political arena of struggle to confer legitimacy on a specific socio-political project and as a distinctive cog ni tive and evaluative framework for understanding societal transformations. The conceptualization of the paper is informed by the work of David Apter and Tony Saich on discourse theory.

Atomistic Simulations: The Driving Force Behind Modern Thermodynamic Research

2021 ◽  
pp. 569-581
Author(s):  
René Spencer Chatwell ◽  
Robin Fingerhut ◽  
Gabriela Guevara-Carrion ◽  
Matthias Heinen ◽  
Timon Hitz ◽  
...  
Keyword(s):  
Driving Force ◽  
Atomistic Simulations

scholarly journals Atomistic Simulations of Surface Relaxations in Ni, Al, and Their Ordered Alloys

1986 ◽  
Vol 82 ◽  
Author(s):  
S. P. Chen ◽  
A. F. Voter ◽  
D. J. Srolovitz
Keyword(s):  
Surface Layer ◽  
Atomistic Simulations ◽  
Atomic Diameter ◽  
Ordered Alloys ◽  
Pure Metals

ABSTRACTWe have performed a series of simulations to examine the atomistic nature of surface relaxations in pure metals and ordered alloys. The surface relaxations (∆dn, n+1) are shown to be oscillatory and to decay rapidly into the bulk. The period and form of the oscillation may be determined by simple geometrical arguments. The oscillation wavelength is always of the order of an atomic diameter. In pure metals, the surface layer of atoms always displaces inward. However, in the ordered alloys the larger atom may displace outward. On planes composed of more than one atom types, rippling occurs.

Finite Element Modeling of Grain Aspect Ratio and Strain Energy Density in a Textured Copper Thin Film

1996 ◽  
Vol 436 ◽  
Author(s):  
R. P. Vinci ◽  
J. C. Bravman
Keyword(s):  
Finite Element ◽  
Energy Density ◽  
Aspect Ratio ◽  
Finite Element Modeling ◽  
Strain Energy Density ◽  
Driving Force ◽  
Strain Energy ◽  
Interface Energy ◽  
Element Modeling ◽  
Grain Aspect Ratio

AbstractWe have modeled the effects of grain aspect ratio on strain energy density in (100)-oriented grains in a (111)-textured Cu film on a Si substrate. Minimization of surface energy, interface energy, and strain energy density (SED) drives preferential growth of grains of certain crystallographic orientations in thin films. Under conditions in which the SED driving force exceeds the surface- and interface-energy driving forces, Cu films develop abnormally large (100) oriented grains during annealing. In the elastic regime the SED differences between the (100) grains and the film average arise from elastic anisotropy. Previous analyses indicate that several factors (e.g. elimination of grain boundaries during grain growth) may alter the magnitude of the SED driving force. We demonstrate, using finite element modeling of a single columnar (100) grain in a (111) film, that changes in grain aspect ratio can significantly affect the SED driving force. A minimum SED driving force is found for (100) Cu grains with diameters on the order of the film thickness. In the absence of other stagnation mechanisms, such behavior could cause small grains to grow abnormally and then stagnate while large grains continue to grow. This would lead to a bimodal grain size distribution in the (100) grains preferred by the SED minimization.

scholarly journals Professor Leslie Rowsell Moore 1912–2003

2004 ◽  
Vol 23 (1) ◽  
pp. 1-2 ◽  
Author(s):  
Edwin Spinner ◽  
Bernard Owens ◽  
Patricia Lunn
Keyword(s):  
Driving Force ◽  
Geological Society ◽  
Breathing Space ◽  
Market Town ◽  
Working Groups ◽  
The University ◽  
The Way

Abstract. Professor Leslie Moore, a former Sorby Professor and Head of the Department of Geology in the University of Sheffield, died on the 13 November 2003 at the age of 91 years. He was the driving force in the establishment of the Micropalaeontological Society.In 1968, during a period when the Geological Society, London was trying to co-ordinate the activities of all Specialist Working Groups in Britain, Leslie Moore was approached by the President of the Society with the request to assess the potential for establishing a Group to cater for the needs of micropalaeontologists. He consulted widely on the issue, not only within the micropalaeontological community but also with industry and other interested societies, only to find no over-whelming enthusiasm for the proposal. He was, however, impressed by the commitment within all branches of the science for the need for a greater degree of organization and identity and proposed the establishment of an autonomous body to meet those needs. It also provided the necessary ‘breathing space’ for the significance of the Geological Society proposals to be considered in full. The British Micropalaeontological Group was born in 1970 and Leslie Moore served as its first Chairman. During his tenure it became obvious that the way forward was to formalize the structure and, in due course, it emerged as the British Micropalaeontological Society.Leslie was born on June 23, 1912, the son of a miner in the Somerset Coalfield and he grew up in the small mining and market town of Midsomer . . .

On Modeling and Simulation of Innovative Ship Rescue System

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Ilias Zilakos ◽  
Michael Toulios
Keyword(s):  
Strain Energy ◽  
Structural Response ◽  
Dry Land ◽  
Strain Energy Density Function ◽  
Material Evaluation ◽  
Element Simulation ◽  
Rescue System ◽  
Funded Project ◽  
Elasticity Tensors ◽  
Good Agreement

Inflatable devices that provide reserve buoyancy to damaged ships, preventing capsizing and/or sinking, along with lifting wreckages from the seabed, were studied within the framework of the European funded project “SuSy” (Surfacing System for Ship Recovery). Part of the work involved material evaluation and testing as well as simulations of the structural response. This paper first describes an orthotropic hyperelastic constitutive model for a candidate material also used in the fabrication of prototype inflatable devices. A strain energy density function is proposed that is further used to derive the stress and elasticity tensors required for the numerical implementation of the model in the user-defined subroutine (UMAT) of abaqus/standard. The second part of the paper presents the finite element simulation of the latter stages of inflation of two salvage devices inside an actual double bottom structure. The numerical results are in good agreement with tests conducted in dry land and under water, with the structure raised following the inflation of the devices. The evolving stress state in both the devices and the double bottom structure under increased contact interaction leads to useful conclusions for future use in the development of this salvage system.

Micro-Mechanical Model for Thermo-Oxidative Aging of Elastomers

2018 ◽  
Author(s):  
Hamid Mohammadi ◽  
Roozbeh Dargazany
Keyword(s):  
Mechanical Model ◽  
Strain Energy ◽  
Aging Process ◽  
Polymer Chains ◽  
Constitutive Behavior ◽  
Network Decomposition ◽  
Oxidative Aging ◽  
The One ◽  
Micro Sphere ◽  
Good Agreement

In this study, a micro-mechanical model for constitutive behavior of elastomers subjected to thermo-oxidative aging is proposed. The model is based on the network decomposition concept and lies within the framework of continuum mechanics. It is assumed that the aging process leads to the formation of a new network with tighter chains. Accordingly, the strain energy of the system is constituted of two independent sources, the energy of the original soft network and the one of the reformed network. These strain energies were computed by integration of entropic energy of polymer chains in each direction of a micro-sphere. The model demonstrates good agreement with different experimental data on relaxation and intermittent tests.

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