Strain Effects in Heteroepitaxial Growth: Island and Dot Formation Kinetics

1996 ◽  
Vol 441 ◽  
Author(s):  
D. R. M. Williams ◽  
L. M. Sander
Keyword(s):  
Lattice Mismatch ◽  
Unit Length ◽  
Surface Strain ◽  
Dimensional Model ◽  
Heteroepitaxial Growth ◽  
Computer Simulation Study ◽  
Island Size ◽  
Strain Effects ◽  
One Dimensional ◽  
Formation Kinetics

AbstractIn many situations where islands and quantum dots are formed on a growing surface strain effects are believed to play an important role. Here we present some preliminary results from a computer simulation study of a one-dimensional model system. Our system consists of an A material upon which grows a B material with a different lattice constant. We only consider the case where less than one monolayer of B has grown on the surface. At any given time the surface consists of a series of “islands” of B bounded by up and downsteps. Dispersed between these islands are mobile B atoms. In general, because of the lattice mismatch between A and B the mobile B atoms are repelled from the islands. This repulsion has an effect on the island size distribution and more particularly on the number of islands per unit length. Here we show that for a moderate repulsion there is a large effect on the number of islands per unit length. However, as the repulsion is increased the effect grows only gradually.

THIN FILM ELECTRON INTERFEROMETRY

1991 ◽  
Vol 05 (21) ◽  
pp. 1387-1405 ◽  
Author(s):  
Y. R. WANG ◽  
J. A. KUBBY ◽  
W. J. GREENE
Keyword(s):  
Thin Film ◽  
Electron Transport ◽  
Standing Wave ◽  
Structural Integrity ◽  
Sample Surface ◽  
Wave Spectra ◽  
Dimensional Model ◽  
Heteroepitaxial Growth ◽  
One Dimensional ◽  
Buried Interfaces

Electron transport through thin overlayers of tin grown on a silicon substrate, and stacking-fault contrast in topographic and conductivity images of Si (111) – 7 × 7 are investigated. Resonances that depend on structural integrity of the overlayer are observed in the conductivity images, and are interpreted as consequences of electron standing-wave formation within the overlayer. The experimental spectra are analyzed using a one-dimensional model which has scattering potentials located at the sample surface and at the overlayer-substrate interface. The agreement between experiment and theory demonstrates that electron-standing wave spectra, in conjunction with bias-dependent topographic and conductivity images, are useful for probing details of buried interfaces formed by surface reconstruction and in heteroepitaxial growth.

Growth and Characterization of Ge/Si (112) Islands

2001 ◽  
Vol 7 (S2) ◽  
pp. 564-565
Author(s):  
M. Floyd ◽  
David J. Smith ◽  
Y. Zhang ◽  
J. Drucker ◽  
S. Tari ◽  
...  
Keyword(s):  
Lattice Mismatch ◽  
Preliminary Investigation ◽  
Growth Conditions ◽  
Effusion Cell ◽  
Heteroepitaxial Growth ◽  
Island Growth ◽  
Island Size ◽  
Knudsen Effusion ◽  
Device Applications

The spontaneous formation of so-called self-assembled quantum dots (SAQDs) during heteroepitaxial growth has attracted much recent interest because of potential device applications. Much attention has been directed towards the Ge/Si(001) system, in particular to characterize the island shape and size distributions as a function of growth conditions, i.e., Ge coverage and substrate temperature. Due to the lattice mismatch, a layer-to-island transition occurs at coverages greater than about 3 monolayers, and thereafter small, coherent hut clusters and larger coherent and incoherent dome clusters are observed. Interdiffusion of Si into the Ge islands as a strain-relief mechanism also occurs. Strategies for achieving better control of island size, shape, composition and separation continue to be sought. in this paper, we report a preliminary investigation of island growth in the alternative Ge/Si(l12) system.The Ge/Si(112) samples were grown by molecular beam epitaxy using a Riber 2300 system equipped with a Ge Knudsen effusion cell.

Modelling Techniques in Applied Glaciology: Numerical Modelling of Avalanches

1983 ◽  
Vol 4 ◽  
pp. 297-297
Author(s):  
G. Brugnot
Keyword(s):  
Finite Difference Method ◽  
Transverse Velocity ◽  
Longitudinal Velocity ◽  
Momentum Conservation ◽  
Dimensional Model ◽  
One Dimensional ◽  
Modelling Techniques ◽  
Reference Grid ◽  
The One ◽  
Near Future

We consider the paper by Brugnot and Pochat (1981), which describes a one-dimensional model applied to a snow avalanche. The main advance made here is the introduction of the second dimension in the runout zone. Indeed, in the channelled course, we still use the one-dimensional model, but, when the avalanche spreads before stopping, we apply a (x, y) grid on the ground and six equations have to be solved: (1) for the avalanche body, one equation for continuity and two equations for momentum conservation, and (2) at the front, one equation for continuity and two equations for momentum conservation. We suppose the front to be a mobile jump, with longitudinal velocity varying more rapidly than transverse velocity.We solve these equations by a finite difference method. This involves many topological problems, due to the actual position of the front, which is defined by its intersection with the reference grid (SI, YJ). In the near future our two directions of research will be testing the code on actual avalanches and improving it by trying to make it cheaper without impairing its accuracy.

Effect Of Phosphorus On Ge/Si(001) Island Formation

2002 ◽  
Vol 737 ◽  
Author(s):  
Theodore I. Kamins ◽  
Gilberto Medeiros-Ribeiro ◽  
Douglas A. A. Ohlberg ◽  
R. Stanley Williams
Keyword(s):  
Deposition Rate ◽  
Strain Energy ◽  
Competitive Adsorption ◽  
Lattice Mismatch ◽  
Three Dimensional ◽  
Deposition Process ◽  
Thin Layers ◽  
Island Size ◽  
Partial Pressures ◽  
Intermediate Size

ABSTRACTWhen Ge is deposited epitaxially on Si, the strain energy from the lattice mismatch causes the Ge in layers thicker than about four monolayers to form distinctive, three-dimensional islands. The shape of the islands is determined by the energies of the surface facets, facet edges, and interfaces. When phosphorus is added during the deposition, the surface energies change, modifying the island shapes and sizes, as well as the deposition process. When phosphine is introduced to the germane/hydrogen ambient during Ge deposition, the deposition rate decreases because of competitive adsorption. The steady-state deposition rate is not reached for thin layers. The deposited, doped layers contain three different island shapes, as do undoped layers; however, the island size for each shape is smaller for the doped layers than for the corresponding undoped layers. The intermediate-size islands are the most significant; the intermediate-size doped islands are of the same family as the undoped, multifaceted “dome” structures, but are considerably smaller. The largest doped islands appear to be related to the defective “superdomes” discussed for undoped islands. The distribution between the different island shapes depends on the phosphine partial pressure. At higher partial pressures, the smaller structures are absent. Phosphorus appears to act as a mild surfactant, suppressing small islands.

Tilting transitions in a one-dimensional model lipid monolayer

1992 ◽  
Vol 25 (10) ◽  
pp. 2889-2896 ◽  
Author(s):  
R D Gianotti ◽  
M J Grimson ◽  
M Silbert
Keyword(s):  
Lipid Monolayer ◽  
Dimensional Model ◽  
One Dimensional
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