Equilibrium surface roughness of a strained epitaxial film due to surface diffusion induced by interface misfit dislocations

ABSTRACTThe appearance of misfit dislocations at the interface between a strained layer and its substrate induces a nonuniform chemical potential along the surface of the layer. Under the assumption that the resulting chemical potential gradient will drive coherent mass rearrangement by surface diffusion, a model of evolution of surface shape is considered which leads to estimates of the surface roughness induced by this mechanism.

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Continuum Modeling of Stress-Driven Surface Diffusion in Strained Elastic Materials

MRS Proceedings ◽

10.1557/proc-308-383 ◽

1993 ◽

Vol 308 ◽

Cited By ~ 7

Author(s):

L. B. Freund ◽

G.E. Beltz ◽

F. Jonsdottir

Keyword(s):

Surface Roughness ◽

Surface Diffusion ◽

Elastic Strain ◽

Strain Energy ◽

Chemical Potential ◽

Flat Surface ◽

Elastic Strain Energy ◽

Surface Shape ◽

Misfit Dislocations ◽

Elastic Materials

ABSTRACTThe free energy of a deformable crystal is assumed to consist of elastic strain energy and surface energy, and the chemical potential for surface diffusion at constant temperature is obtained under this assumption. The result is applied in considering the phenomena of instability of a flat surface in a stressed material under fluctuations in surface shape, and the development of surface roughness due to the proximity of misfit dislocations to the free surface of the material.

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Three Dimensional Surface Waviness of an Epitaxial Layer Due to Surface Diffusion Induced by Interface Misfit Dislocations

MRS Proceedings ◽

10.1557/proc-356-45 ◽

1994 ◽

Vol 356 ◽

Cited By ~ 3

Author(s):

F. Jonsdottir

Keyword(s):

Surface Diffusion ◽

Epitaxial Layer ◽

Thermodynamic Equilibrium ◽

Three Dimensional ◽

Misfit Dislocations ◽

Surface Waviness ◽

Mismatch Strain ◽

Equilibrium Surface ◽

Elastic Mismatch ◽

Dimensional Surface

AbstractIt has been observed that, for some strained epitaxial layer systems, the surface of the layer develops roughness or waviness which correlates spatially with the positions of underlying interface misfit dislocations which partially relax the elastic mismatch strain. A model based on redistribution of mass by surface diffusion is analyzed to estimate the waviness of the three dimensional thermodynamic equilibrium surface due to intersecting arrays of interface misfit dislocations.

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Enhanced Surface Diffusion in Low-temperature a-Si:H Processing

MRS Proceedings ◽

10.1557/proc-808-a9.33 ◽

2004 ◽

Vol 808 ◽

Cited By ~ 1

Author(s):

George T. Dalakos ◽

Joel L. Plawsky ◽

Peter D. Persans

Keyword(s):

Surface Roughness ◽

Surface Diffusion ◽

Room Temperature ◽

Cathodic Deposition ◽

Hydrogenated Silicon ◽

Surface Diffusivity ◽

Amorphous Hydrogenated Silicon ◽

Anodic Deposition ◽

Enhanced Surface ◽

Global Parameters

ABSTRACTGlow discharge amorphous hydrogenated silicon (a-Si:H) prepared at near room temperature typically results in an inhomogeneous morphology that is undesirable for a number of thin film applications. The most commonly observed features of this include columnar morphology and surface roughness. This usually results from anodic deposition, where substrates are placed on the grounded electrode. We have discovered that placing substrates on the RF-powered electrode (referred to as cathodic deposition) offers a much wider processing range for homogenous growth than anodic growth. We have also found that the magnitude of the surface roughness and the bulk void fraction of both anodic and cathodic a-Si:H thin films processed at low-temperatures is proportional to ∼D/F, where D is the surface diffusivity and F, the adatom flux, though anodic and cathodic deposition affect these global parameters differently. Surface processes unique to cathodic deposition can enhance adatom surface diffusion, while diffusion during anodic deposition is fixed and cannot attain homogeneous growth at high adatom fluxes. Processing a-Si:H on the cathode, associated with enhanced adatom surface diffusion, allows for homogeneous growth even at high deposition rates that has benefits for a number of applications.

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Investigation of Surface Topography at the End of Running-In Process

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.437.564 ◽

2013 ◽

Vol 437 ◽

pp. 564-567

Author(s):

Geng Pei Zhang ◽

Xiao Jun Liu ◽

Wen Long Lu ◽

Xiang Qian Jiang

Keyword(s):

Surface Roughness ◽

Surface Topography ◽

Surface Profile ◽

Wear Process ◽

Equilibrium Surface ◽

Important Stage ◽

Before And After ◽

3D Information

Running-in process is an important stage of whole wear process. The irrelevance of surface roughness before and after running-in puzzled the running-in research. However, this conclusion was based on surface roughness derived from the 2D surface profile which does not contain 3D information, and was therefore not complete. In this paper, running-in experiments were conducted to investigate the issue. The results showed that there is no equilibrium surface topography similar with equilibrium roughness at the end of running-in process.

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MBE growth of compound semiconductors: Part II. Applications of the stochastic model

Journal of Materials Research ◽

10.1557/jmr.1992.1235 ◽

1992 ◽

Vol 7 (5) ◽

pp. 1235-1242 ◽

Cited By ~ 9

Author(s):

R. Venkatasubramanian

Keyword(s):

Growth Rate ◽

Surface Roughness ◽

Phase Separation ◽

Stochastic Model ◽

Diffusion Process ◽

Surface Diffusion ◽

Growth Front ◽

Mbe Growth ◽

Temperature Range ◽

Kinetics Of

In this part of the work (Part II), two typical applications of the stochastic model to the MBE growth kinetic studies are presented. The applications are the MBE growth kinetics of a hypothetical compound semiconductor, ab, and diamond cubic alloy, ax. In this study, the effect of the surface diffusion process on the MBE growth kinetics is analyzed. In the case of the compound, ab, the results of the present stochastic model are compared with that of a Monte Carlo simulation study in the temperature range of 600–850 K. The results of the two studies agree qualitatively. Higher substrate temperatures result in higher growth rate and growth front smoothness due to higher surface diffusion. Beyond 800 K, the growth rate and the growth front smoothness become independent of temperature because of the saturation of the interlayer diffusion process. In the case of the alloy studies, the kinetics of a hypothetical diamond cubic alloy in which the thermodynamics favors phase separation, is studied in the temperature range of 573–898 K. Below 648 K, due to negligible surface diffusion, there is no clustering of the alloy, but the surface roughness is very large. In the intermediate temperature range of 573–798 K, with increasing temperature, the surface diffusion increases, resulting in more clustering and less surface roughness. Above 798 K, due to very high surface diffusion, complete phase separation of the alloy and a smooth surface result.

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A Kinetic Model for the Strain Relaxation in Heteroepitaxial Thin Film Systems

MRS Proceedings ◽

10.1557/proc-673-p5.11 ◽

2001 ◽

Vol 673 ◽

Author(s):

Y.W. Zhang ◽

T.C. Wang ◽

S.J. Chua

Keyword(s):

Thin Film ◽

Surface Roughness ◽

Kinetic Model ◽

Strain Relaxation ◽

Experimental Results ◽

Threading Dislocation ◽

Threading Dislocations ◽

Misfit Dislocations ◽

Dislocation Reduction ◽

Wide Range

ABSTRACTA kinetic model is presented to simulate the strain relaxation in the GexSi1−x/Si(100) systems. In the model, the nucleation, propagation and annihilation of threading dislocations, the interaction between threading dislocations and misfit dislocations, and surface roughness are taken into account. The model reproduces a wide range of experimental results. The implications of its predictions on the threading dislocation reduction during the growth processes of the heteoepitaxial thin film systems are discussed.

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High Quality in.Ga1−xas Heterostructures Grown on GaAs With Movpe

MRS Proceedings ◽

10.1557/proc-510-101 ◽

1998 ◽

Vol 510 ◽

Cited By ~ 1

Author(s):

M.T. Bulsara ◽

E.A. Fitzgerald

Keyword(s):

Surface Roughness ◽

Phase Separation ◽

Threading Dislocation ◽

Misfit Dislocations ◽

Cross Sectional ◽

Plan View ◽

Force Microscopy ◽

Optimum Growth Temperature ◽

Transmission Electron ◽

Metal Organic

AbstractInxGa1−xAs structures with compositionally graded buffers were grown by metal-organic vapor phase epitaxy (MOVPE) on GaAs substrates and characterized with plan-view and cross-sectional transmission electron microscopy (PV-TEM and X-TEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The results show that surface roughness experiences a maximum at growth temperatures where phase separation occurs in InxGa1−xAs. The strain energy due misfit dislocations in the graded buffer indirectly influences phase separation. At growth temperatures above and below this temperature, the surface roughness is decreased significantly; however, only growth temperatures above this regime ensure nearly complete relaxed graded buffers with the most uniform composition caps. With the optimum growth temperature for grading InxGa1−xAs determined to be 700°C, it was possible to produce In0.33Ga0.67As diode structures on GaAs with threading dislocation densities < 8.5 × 106/cm2

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