Some Computer Simulations of Semiconductor Thin Film Growth and Strain Relaxation in a Unified Atomistic and Kinetic Model

1995 ◽  
Vol 408 ◽  
Author(s):  
A. Madhukar ◽  
W. Yu ◽  
R. Viswanathan ◽  
P. Chen
Keyword(s):  
Kinetic Model ◽  
Defect Formation ◽  
Kinetic Monte Carlo ◽  
Strain Relaxation ◽  
High Energy ◽  
Fixed Number ◽  
Dislocation Nucleation ◽  
Relative Significance ◽  
Stepped Surfaces ◽  
Kinetic Processes

AbstractAn overview is provided of an evolving atomistic and kinetic model of semiconductor growth that unifies the main features of strain relaxation in low and high lattice misfit heteroepitaxy. The model reveals a kinetic pathway for dislocation formation during growth with little or no energy cost at low misfits, thus providing a way out of the longstanding dilemma of too high dislocation nucleation energies predicted by classical theories of the equilibrium behaviour of a fixed number of particles at low misfits. The essential kinetic processes underlying the model are identified on the basis of comparison of the predictions of kinetic Monte-Carlo simulations of growth with real-time or in-situ data obtained in such experiments as reflection high-energy electron diffraction (RHEED) and scanning probe microscopy (SPM). Relative significance of these atomistic kinetic processes is shown to naturally lead to strain relaxation via defect initiation at low misfits while maintaining smooth surface morphology or at high misfits change to 3-dimensional morphology while initially maintaining coherence. The potential role of steps in providing sources for defect formation is examined through molecular dynamics simulations of Ge overlayers on Si (001) stepped surfaces.

scholarly journals Dislocation Loop Generation Differences between Thin Films and Bulk in EFDA Pure Iron under Self-Ion Irradiation at 20 MeV

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2000
Author(s):  
Marcelo Roldán ◽  
Fernando José Sánchez ◽  
Pilar Fernández ◽  
Christophe J. Ortiz ◽  
Adrián Gómez-Herrero ◽  
...  
Keyword(s):  
Thin Films ◽  
Computational Models ◽  
Defect Formation ◽  
Ion Irradiation ◽  
Damage Zone ◽  
High Energy ◽  
Model Material ◽  
Dislocation Nucleation ◽  
Dislocation Loops ◽  
Experimental Conditions

In the present investigation, high-energy self-ion irradiation experiments (20 MeV Fe+4) were performed on two types of pure Fe samples to evaluate the formation of dislocation loops as a function of material volume. The choice of model material, namely EFDA pure Fe, was made to emulate experiments simulated with computational models that study defect evolution. The experimental conditions were an ion fluence of 4.25 and 8.5 × 1015 ions/cm2 and an irradiation temperature of 350 and 450 °C, respectively. First, the ions pass through the samples, which are thin films of less than 100 nm. With this procedure, the formation of the accumulated damage zone, which is the peak where the ions stop, and the injection of interstitials are prevented. As a result, the effect of two free surfaces on defect formation can be studied. In the second type of experiments, the same irradiations were performed on bulk samples to compare the creation of defects in the first 100 nm depth with the microstructure found in the whole thickness of the thin films. Apparent differences were found between the thin foil irradiation and the first 100 nm in bulk specimens in terms of dislocation loops, even with a similar primary knock-on atom (PKA) spectrum. In thin films, the most loops identified in all four experimental conditions were b ±a0<100>{200} type with sizes of hundreds of nm depending on the experimental conditions, similarly to bulk samples where practically no defects were detected. These important results would help validate computational simulations about the evolution of defects in alpha iron thin films irradiated with energetic ions at large doses, which would predict the dislocation nucleation and growth.

In-Situ Measurements of Islanding and Strain Relaxation of Ge/Si(111)

1996 ◽  
Vol 441 ◽  
Author(s):  
P. W. Deelman ◽  
L. J. Schowalter ◽  
T. Thundat
Keyword(s):  
Initial Rate ◽  
Strain Relaxation ◽  
Misfit Strain ◽  
High Energy ◽  
Lattice Parameter ◽  
Dislocation Nucleation ◽  
Island Growth ◽  
Aspect Ratios ◽  
Surface Lattice ◽  
Increasing Temperature

AbstractWe have measured strain relaxation and islanding in Ge films grown by molecular beam epitaxy on Si(111) at substrate temperatures between 450°C and 700°C in real time with reflection high energy electron diffraction (RHEED). At 450°C, we observe an oscillation of the surface lattice parameter for the first three bilayers (BL), followed by a sharp 2D–3D growth mode transition, when transmission diffraction features appear in RHEED. The surface lattice parameter then begins to relax at an initial rate of about 0.5%/BL. The mechanisms of island growth and strain relaxation change with growth temperature. At 500°C the surface lattice parameter begins to relax after only 1BL; at 550°C relaxation begins immediately. However, 3D spots do not appear until after 3.5BL at either temperature. The initial rate of strain relaxation decreases with increasing temperature until, at 700°C (when 3D spots never appear), it is only 0.04%/BL. This behavior may be explained by a temperature-dependent roughness length scale, as well as by differences in dislocation nucleation at low and high temperatures. At low temperature, atomic force microscope images show the development of small (1000Å), faceted islands with aspect ratios (height/width) on the order of 0.07. The formation of well-defined facets is inhibited at higher temperatures. At 700°C, islands grow very large (lμm) from the outset, with aspect ratios less than 0.015. These islands cannot thicken much, because dislocations can glide in easily at their edges. The islands grow laterally quickly, and the strain in the “new” islands is not substantially less than that in the “old.” At 700°C, 28% of the Ge/Si misfit strain may be relieved by diffusion.

Model-based analysis of coupled equilibrium-kinetic processes: indirect kinetic studies of thermodynamic parameters using the dynamic data

The Analyst ◽  
2015 ◽  
Vol 140 (9) ◽  
pp. 3121-3135
Author(s):  
Fereshteh Emami ◽  
Marcel Maeder ◽  
Hamid Abdollahi
Keyword(s):  
Kinetic Model ◽  
Thermodynamic Parameters ◽  
Kinetic Models ◽  
Kinetic Studies ◽  
Dynamic Data ◽  
Model Based ◽  
Kinetic Processes ◽  
Model Based Analysis

Schematic of intertwined equilibrium-kinetic model at time = 0,1,2…T when both equilibrium and kinetic models are solved explicitly.

scholarly journals Self-adaptive strain-relaxation optimization for high-energy lithium storage material through crumpling of graphene

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Yunlong Zhao ◽  
Jiangang Feng ◽  
Xue Liu ◽  
Fengchao Wang ◽  
Lifen Wang ◽  
...  
Keyword(s):  
Strain Relaxation ◽  
High Energy ◽  
Storage Material ◽  
Lithium Storage ◽  
Self Adaptive

Atomistic Modeling of Point and Extended Defects in Crystalline Materials

1998 ◽  
Vol 532 ◽  
Author(s):  
Martin Jaraiz ◽  
Lourdes Pelaz ◽  
Emiliano Rubio ◽  
Juan Barbolla ◽  
George H. Gilmer ◽  
...  
Keyword(s):  
Defect Formation ◽  
Kinetic Monte Carlo ◽  
Object Oriented ◽  
Deep Submicron ◽  
Object Oriented Programming ◽  
Extended Defects ◽  
Crystalline Materials ◽  
Monte Carlo Simulation Technique ◽  
Definition Of ◽  
Reaction Equations

ABSTRACTAtomistic process modeling, a kinetic Monte Carlo simulation technique, has the interest of being both conceptually simple and extremely powerful. Instead of reaction equations it is based on the definition of the interactions between individual atoms and defects. Those interactions can be derived either directly from molecular dynamics or first principles calculations, or from experiments. The limit to its use is set by the size dimensions it can handle, but the level of performance achieved by even workstations and PC's, together with the design of efficient simulation schemes, has revealed it as a good candidate for building the next generation of process simulators, as an extension of existing continuum modeling codes into the deep submicron size regime. Over the last few years it has provided a unique insight into the atomistic mechanisms of defect formation and dopant diffusion during ion implantation and annealing in silicon. Object-oriented programming can be very helpful in cutting software development time, but care has to be taken not to degrade performance in the critical inner calculation loops. We discuss these techniques and results with the help of a fast object-oriented atomistic simulator recently developed.

Evolution of Ion Beam Synthesized Au Nanoclusters in SiO2 under Ion Irradiation

2000 ◽  
Vol 647 ◽  
Author(s):  
Bernd Schmidt ◽  
Karl-Heinz Heinig ◽  
Arndt Mücklich
Keyword(s):  
Size Distribution ◽  
Ostwald Ripening ◽  
Ion Irradiation ◽  
Kinetic Monte Carlo ◽  
Ion Beam ◽  
Thick Layer ◽  
High Energy ◽  
Au Nanoclusters ◽  
Post Irradiation ◽  
Mean Size

AbstractThe evolution of the mean size and the size distribution of Au nanoclusters (NCs) under high-energy ion irradiation has been studied. Au NCs were synthesized in a 480 nm thick SiO2 layer by 330 keV Au+ implantation and subsequent annealing at T = 1000 °C for 1h in dry O2. XTEM images show a 70 nm thick layer of Au NCs, being centered at the projected ion range Rp(330keV) = 100 nm, having a mean NC size of 5 nm at Rp, and resembling the broad Lifshiz-Slyozov-Wagner (LSW) size distribution of diffusion controlled Ostwald ripening. Post-irradiation of the Au NCs by 4.5 MeV gold ions was used in order to tailor their size and size distribution. The high-energy Au+ irradiations were performed at 190...210 °C with a fluence of (0.5...1.0)×1016 cm-2. By the post-irradiation no gold was deposited into the SiO2 layer, the Au+ ions come to rest in the (001)Si substrate at Rp(4.5MeV) = 1 [.proportional]m. XTEM images of the post-irradiated Au NCs show a strong decrease of their mean size as well as the width of their size distribution. The observed NC evolution under ion irradiation agrees with recent theoretical predictions and kinetic Monte-Carlo simulations.

A Model for Lattice-Mismatched Epitaxy: A Continuum View

1992 ◽  
Vol 280 ◽  
Author(s):  
B. G. Orr ◽  
C. W. Snyder
Keyword(s):  
Surface Diffusion ◽  
Strain Relaxation ◽  
Relaxation Mechanism ◽  
High Energy ◽  
Growth Mode ◽  
Scanning Tunneling ◽  
Physical Factors ◽  
Diffusion Kinetics ◽  
Tunneling Microscopy ◽  
Lattice Mismatched Epitaxy

To date, primarily only idealized equilibrium models for the growth mode and strain relaxation of elastically strained overlayers have been proposed. Here we present a general continuum model for lattice-mismatched epitaxy. As molecular beam epitaxy is inherently a nonequilibrium growth process, surface diffusion kinetics is incorporated in the model. Additionally, a new strain relaxation mechanism in a dislocation-free film is considered. Experimental support for our view is obtained from measurements made by reflection high energy electron diffraction, scanning tunneling microscopy, and transmission electron microscopy on the growth of InGaAs on GaAs(100). These results demonstrate the strong effects which strain, surface diffusion kinetics, and surface energy have on growth mode. From analytical and numerical analysis in 1 + 1 dimensions, the interrelationship of such physical factors is revealed. Our improved understanding enables control over the growth behavior of strained-layer superlattices and heterostructures.

Lattice constant variation in GaN:Si layers grown by HVPE

2002 ◽  
Vol 743 ◽  
Author(s):  
A. Usikov ◽  
O. V. Kovalenkov ◽  
M. M. Mastro ◽  
D. V. Tsvetkov ◽  
A. I. Pechnikov ◽  
...  
Keyword(s):  
Defect Formation ◽  
Strain Relaxation ◽  
Growth Conditions ◽  
Optical And Electrical Properties ◽  
X Ray Diffraction ◽  
Proper Selection ◽  
X Ray ◽  
Lattice Constants ◽  
Si Doping ◽  
Selection Of

ABSTRACTThe structural, optical, and electrical properties of HVPE-grown GaN-on-sapphire templates were studied. The c and a lattice constants of the GaN layers were measured by x-ray diffraction. It was observed that the c and a lattice constants vary non-monotonically with Si-doping. The proper selection of Si-doping level and growth conditions resulted in controllable strain relaxation, and thus, influenced defect formation in GaN-on-sapphire templates. It was also observed that HVPE homoepitaxial GaN layers grown on the templates have better crystal quality and surface morphology than the initial templates.

scholarly journals Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate

MRS Advances ◽  
2016 ◽  
Vol 1 (17) ◽  
pp. 1203-1208 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
High Temperature ◽  
Oxygen Diffusion ◽  
Density Functional ◽  
Defect Formation ◽  
Kinetic Monte Carlo ◽  
Interstitial Oxygen ◽  
Temperature Oxidation ◽  
Electron Volt ◽  
Formation Energies

ABSTRACTYtterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such applications, the transport of oxygen and water vapor through these coatings to the ceramic substrate is undesirable if high temperature oxidation is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated and interstitial oxygen diffusion in Ytterbium disilicate. Oxygen vacancy and interstitial site energies, vacancy and interstitial formation energies, and migration barrier energies were computed using Density Functional Theory. We have found that, in the case of vacancy-mediated diffusion, many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small. In the case of interstitial diffusion, migration barrier energies are typically around one electron volt, but the interstitial defect formation energies are positive, with the result that the disilicate is unlikely to exhibit experience significant oxygen permeability except at very high temperature.

Sign in / Sign up

Export Citation Format

Share Document