Surface Reconstruction and Strain Relief in Si1−x-Gex Films on Si(100)

1992 ◽  
Vol 280 ◽  
Author(s):  
Qiuming Yu ◽  
Paulette Clancy
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Molecular Dynamics ◽  
Surface Reconstruction ◽  
Experimental Studies ◽  
Equilibrium Structure ◽  
Strain Relief ◽  
Theoretical Predictions ◽  
Weber Potential

ABSTRACTThe equilibrium structure of a variety of Si1−xGex/Si heterostructures have been simulated by Molecular Dynamics, modeled by the Stillinger-Weber potential, to investigate the effect of strain on the surfaces of SiGe thin Alms. It was found that the strain in SiGe/Si(100) thin films was relaxed by the segregation of Ge to the surface. Rebonding of sub-surface atoms into dimers in the presence of a vacancy or cluster of vacancies above them was observed in the ensuing surface reconstruction. For SiGe/Si, the amount of “re-bonded missing dimers” in the top two layers increased with increasing Ge composition. But for Ge/Si(100), a V-shaped twinning defect was observed in the Ge thin film. To further investigate the effect of strain on surface reconstruction, bulk Si and Ge structures were also studied. For bulk Si, several rebonded missing dimers were found at the surface, while for bulk Ge(100), the surface showed a typical 2×1 reconstruction. All these findings corroborate recent experimental studies and theoretical predictions.

scholarly journals Molecular Dynamics Study of Solid Thin-Film Thermal Conductivity

2000 ◽  
Vol 122 (3) ◽  
pp. 536-543 ◽  
Author(s):  
J. R. Lukes ◽  
D. Y. Li ◽  
X.-G. Liang ◽  
C.-L. Tien
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Plane ◽  
Computational Technique ◽  
Lennard Jones ◽  
Theoretical Predictions ◽  
Solid Thin Films ◽  
Phase Data

This study uses the molecular dynamics computational technique to investigate the thermal conductivity of solid thin films in the direction perpendicular to the film plane. In order to establish a benchmark reference, the computations are based on the widely used Lennard-Jones argon model due to its agreement with experimental liquid-phase data, its physically meaningful parameters, and its simple two-body form. Thermal conductivity increases with film thickness, as expected from thin-film experimental data and theoretical predictions. The calculated values are roughly 30 percent higher than anticipated. Varying the boundary conditions, heat flux, and lateral dimensions of the films causes no observable change in the thermal conductivity values. The present study also delineates the conditions necessary for meaningful thermal conductivity calculations and offers recommendations for efficient simulations. This work shows that molecular dynamics, applied under the correct conditions, is a viable tool for calculating the thermal conductivity of solid thin films. More generally, it demonstrates the potential of molecular dynamics for ascertaining microscale thermophysical properties in complex structures. [S0022-1481(00)02303-3]

The Study on Young's Modulus of Multilayered Cu/Ni Multilayered Nano Thin Films by Molecular Dynamics Simulation

2014 ◽  
Vol 513-517 ◽  
pp. 113-116
Author(s):  
Jen Ching Huang ◽  
Fu Jen Cheng ◽  
Chun Song Yang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Strain Rate ◽  
Young’S Modulus ◽  
Potential Function ◽  
Dynamics Simulation ◽  
System Temperature ◽  
Simulation Results

The Youngs modulus of multilayered nanothin films is an important property. This paper focused to investigate the Youngs Modulus of Multilayered Ni/Cu Multilayered nanoThin Films under different condition by Molecular Dynamics Simulation. The NVT ensemble and COMPASS potential function were employed in the simulation. The multilayered nanothin film contained the Ni and Cu thin films in sequence. From simulation results, it is found that the Youngs modulus of Cu/Ni multilayered nanothin film is different at different lattice orientations, temperatures and strain rate. After experiments, it can be found that the Youngs modulus of multilayered nanothin film in the plane (100) is highest. As thickness of the thin film and system temperature rises, Youngs modulus of multilayered nanothin film is reduced instead. And, the strain rate increases, the Youngs modulus of Cu/Ni multilayered nanothin film will also increase.

Reactive Phase Formation in Thin Films: Evolution of Grain Structure

1995 ◽  
Vol 403 ◽  
Author(s):  
K. Barmak ◽  
C. Michaelsent ◽  
J. Rickman ◽  
M. Dahmstt
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Formation ◽  
Experimental Studies ◽  
Grain Structure ◽  
Structure Evolution ◽  
Future Research ◽  
Polycrystalline Materials ◽  
Product Phase ◽  
Nucleation Kinetics

AbstractIt is a well known fact that the properties and performance of polycrystalline materials, including polycrystalline thin films, are strongly affected by the grain structure. Therefore, in treating reactive phase formation in these films, it is (or it will inevitably be) necessary to quantify the grain structure of reactant and product phases and its evolution during the course of the reaction. Theoretical models and the conventional view of thin film reactions, however, have been largely extensions, to small and finite dimensions, of theories and descriptions developed for bulk diffusion couples. These models and descriptions primarily focus on the growth stage and to a much lesser extent on the nucleation stage. Consequently, these models and descriptions are not able to treat the development of product phase grain structure. Recent calorimetric investigations of several thin film systems demonstrate the importance of nucleation kinetics (and hence nucleation barriers) in product phase formation and provide quantitative measures of the thermodynamics and kinetics of formation of the product phases, thereby allowing some degree of comparison with reaction models. Furthermore, microstructural investigations of thin-film reactions demonstrate the non-planarity of the growth front and highlight the role of reactant-phase grain boundaries. In this paper, a summary of these experimental studies and recent theoretical treatments, which combine nucleation and growth in an integrated manner, is presented, with particular emphasis on the Nb/Al system. These experiments and models lead to a new view of reactive phase formation and grain structure evolution as one in which the latter is an integral part of the former. Based on this view, directions for future research are discussed.

Deposition energy dependence in cluster-assembled thin film densities

2005 ◽  
Vol 908 ◽  
Author(s):  
Kristoffer Meinander ◽  
Tina Clauss ◽  
Kai Nordlund
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Energy Dependence ◽  
Computer Simulations ◽  
Cluster Atom ◽  
Cu Nanoclusters ◽  
Deposition Energy

AbstractMechanical properties of thin films grown by nanocluster deposition are highly dependent on the energy at which the clusters are deposited. Using molecular dynamics computer simulations we have quantitatively studied variations in the properties of copper thin films grown by deposition of Cu nanoclusters, at energies ranging from 5 meV to 10 eV per cluster atom, on a Cu (100) substrate.

Molecular Dynamics Simulation on the Out-of Plane Thermal Conductivity of Single-Crystal Carbon Thin Films

2009 ◽  
Vol 60-61 ◽  
pp. 430-434 ◽  
Author(s):  
Xing Li Zhang ◽  
Zhao Wei Sun ◽  
Guo Qiang Wu
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Potential Energy ◽  
Film Thickness ◽  
Single Crystal ◽  
Diamond Crystal ◽  
Dynamics Simulation ◽  
Crystal Direction

In this article, we select corresponding Tersoff potential energy to build potential energy model and investigate the thermal conductivities of single-crystal carbon thin-film. The equilibrium molecular dynamics (EMD) method is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (001), and the non-equilibrium molecular dynamics (NEMD) is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (111). The results of calculations demonstrate that the nanometer thin film thermal conductivity of diamond crystal is remarkably lower than the corresponding bulk experimental data and increase with increasing the film thickness, and the nanometer thin film thermal conductivity of diamond crystal relates to film thickness linearly in the simulative range. The nanometer thin film thermal conductivity also demonstrates certain regularity with the change of temperature. This work shows that molecular dynamics, applied under the correct conditions, is a viable tool for calculating the thermal conductivity of nanometer thin films.

Thin Film In-Plane Silicon Thermal Conductivity Dependence on Molecular Dynamics Surface Boundary Conditions

2004 ◽  
Author(s):  
Carlos J. Gomes ◽  
Marcela Madrid ◽  
Cristina H. Amon
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Boundary Conditions ◽  
Mean Free Path ◽  
Surface Boundary ◽  
Repulsive Potential ◽  
Surface Boundary Conditions ◽  
Weber Potential

The in-plane thermal conductivity of thin silicon films is predicted using equilibrium molecular dynamics, the Stillinger-Weber potential and the Green-Kubo relationship. Film thicknesses range from 2 to 200 nm. Periodic boundary conditions are used in the directions parallel to the thin film surfaces. Two different strategies are evaluated to treat the atoms on the surfaces perpendicular to the thin film direction: adding four layers of atoms kept frozen at their crystallographic positions, or restraining the atoms near the surfaces with a repulsive potential. We show that when the thin-film thickness is smaller than the phonon mean free path, the predictions of the in-plane thermal conductivity at 1000K differ significantly depending on the potential applied to the atoms near the surfaces. In this limit, the experimentally observed trend of decreasing thermal conductivity with decreasing film thickness is predicted when the surface atoms are subject to a repulsive potential in addition to the Stillinger-Weber potential, but not when they are limited by frozen atoms.

Applying NiTi Shape-Memory Thin Films to Thermomechanical Data Storage Technology

2004 ◽  
Vol 855 ◽  
Author(s):  
Wendy C. Crone ◽  
Gordon A. Shaw
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Shape Memory ◽  
Data Storage ◽  
Martensite Phase ◽  
Magnetic Data ◽  
Thermomechanical Cycling ◽  
Storage Technology ◽  
Storage Media ◽  
Theoretical Predictions

ABSTRACTAs the data storage density in cutting edge microelectronic devices continues to increase, the superparamagnetic effect poses a problem for magnetic data storage media. One strategy for overcoming this obstacle is the use of thermomechanical data storage technology. In this approach, data is written by a nanoscale mechanical probe as an indentation on a surface, read by a transducer built into the probe, and then erased by the application of heat. An example of such a device is the IBM millipede, which uses a polymer thin film as the data storage medium. It is also possible, however, to use other kinds of media for thermomechanical data storage, and in the following work, we explore the possibility of using thin film Ni-Ti shape memory alloy (SMA). Previous work has shown that nanometer-scale indentations made in martensite phase Ni-Ti SMA thin films recover substantially upon heating. Issues such as repeated thermomechanical cycling of indentations, indent proximity, and film thickness impact the practicability of this technique. While there are still problems to be solved, the experimental evidence and theoretical predictions show SMA thin films are an appropriate medium for thermomechanical data storage.

Self-assembly of donor–acceptor semiconducting polymers in solution thin films: a molecular dynamics simulation study

2017 ◽  
Vol 5 (37) ◽  
pp. 9602-9610 ◽  
Author(s):  
Makoto Yoneya ◽  
Satoshi Matsuoka ◽  
Jun’ya Tsutsumi ◽  
Tatsuo Hasegawa
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Simulation Study ◽  
Self Assembly ◽  
Semiconducting Polymers ◽  
Dynamics Simulation ◽  
Polymer Thin Film ◽  
Donor Acceptor

The direction of π-stacking in a polymer thin film is crucially important in applications of semiconducting polymers.

Molecular Dynamics Simulation of Aluminium Thin Film Surface Activated Bonding

2011 ◽  
Vol 486 ◽  
pp. 127-130
Author(s):  
Chao Cheng Chang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Molecular Dynamics ◽  
Surface Roughness ◽  
Bonding Strength ◽  
Film Surface ◽  
Dynamics Simulation ◽  
Thin Film Surface ◽  
Common Neighbour ◽  
Eam Potential

This study used molecular dynamics simulations with an embedded-atom method (EAM) potential to investigate the effect of surface roughness on the surface activated bonding (SAB) of aluminium thin films. The simulations started with the bonding process and followed by the tensile test for estimating bonding strength. By averaging the atomic stresses over the entire system, the stress-time curves for the bonded films under a tensile condition were predicted. Moreover, the evolution of the crystal structure in the local atomic order was examined by the common neighbour analysis. The simulated results show that the decrease in the surface roughness of thin film improves the bonding strength. The observed recrystallization processes inside the bonded thin films also reveal that the plastic deformation of the aluminium surface due to atomic attracting force compensates surface roughness.

Molecular Dynamics Simulation of Epitaxial Growth

MRS Bulletin ◽  
1988 ◽  
Vol 13 (11) ◽  
pp. 23-28 ◽  
Author(s):  
Ivan K. Schuller
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Epitaxial Growth ◽  
Film Growth ◽  
Relaxation Times ◽  
Experimental Studies ◽  
Thin Film Growth ◽  
Dynamics Simulation ◽  
Unknown Parameters ◽  
Model Calculations

The growth of thin films has been instrumental in the study of many areas of material science, physics, metallurgy, and chemistry and is an important ingredient in the development of many devices. Although experimental studies have been extensively pursued for many years, theoretical studies have only been performed using model calculations which rely on a number of unknown parameters a priori. Only recently have attempts been made to understand thin film growth using realtime numerical simulation. The main reason for the recent increase of such studies is the development of computers capable of tackling a problem of the magnitude required to understand thin film growth. The phenomena present in thin film growth occur for systems containing many particles (e.g., columnar growth) and long relaxation times, which strain the capabilities presently available in modern supercomputers. Further increases in computational power might bring a number of important problems within reach and improve our understanding of thin film growth at the microscopic level.I will present a number of epitaxial growth studies we have performed using molecular dynamics (MD) techniques. I will show that a number of properties predicted by these calculations are in good agreement with experimental observations. These include the microcrystalline and epitaxial growth of metal films, the growth of amorphous films in mixtures of metals, and the vapor phase growth of silicon. Finally, I will outline several important studies yet to be implemented.

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