Surface Stress Effects On The Critical Thickness Of Thin Film Superlattices

1997 ◽  
Vol 505 ◽  
Author(s):  
R. C. Cammarata ◽  
K. Sieradzki
Keyword(s):  
Thin Film ◽  
Solid Surface ◽  
Surface Stress ◽  
Critical Thickness ◽  
Unit Area ◽  
Solid Surfaces ◽  
Stress Effects ◽  
Surface Stresses ◽  
Solid Phases ◽  
Reversible Work

ABSTRACTSurface stress represents the reversible work per unit area to elastically stretch a solid surface, and can be associated with interfaces between two solid phases as well as free solid surfaces. The effects of surface stresses on the critical thickness for epitaxy in thin film superlattices is given.

Surface Stress Effects on Thin Film Growth

1993 ◽  
Vol 317 ◽  
Author(s):  
R.C. Cammarata
Keyword(s):  
Thin Film ◽  
Surface Stress ◽  
Critical Thickness ◽  
Film Growth ◽  
Thin Film Growth ◽  
Stress Generation ◽  
Intrinsic Stress ◽  
Surface And Interface ◽  
Stress Effects

ABSTRACTA review of surface and interface stresses relevant to thin film growth is presented. It is shown that surface stress effects that are generally ignored in the analysis of epitaxy can have an influence on the critical thickness for epitaxy, especially at larger Misfits. A discussion of intrinsic stress generation from surface stress is also presented.

Linear Stability of Thin Liquid Film on Solid Surface Under Effect of Apolar and Polar Forces

2012 ◽  
Author(s):  
El–Harbawi M. ◽  
Mustapha S. ◽  
Idris A. ◽  
Jameel A.T. ◽  
T.G. Chuah
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
Free Energy ◽  
Solid Surface ◽  
Unit Area ◽  
Excess Free Energy ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Acid Base ◽  
Navier Stokes Equation

Tenaga lebihan bebas Gibb per unit luas (ΔG) bagi suatu saput nipis yang tulen, tanpa cas pada satu sokongan hanya diterbitkan daripada interaksi antara molekul apolar (Lifshitz - van der Waals) dan polar (acid-bes). Interaksi polar dapat dinyatakan secara berasingan sebagai tekanan penghidratan, interaksi hidrofobik dan intekrasi asid-bes. Jumlah tenaga lebihan bebas Gibb per unit luas (ΔG) bagi satu saput nipis pada satu lapisan bergantung kepada ketebalan saput, dan angkali penyebaran apolar dan polar untuk sistem tersebut. Saput dimodelkan sebagai cecair Newtonian 2-dimensi dengan ketumpatan tetap, ρ, dan kelikatan, μ, mengalir di atas satu permukaan mengufuk. Ketebalan purata saput cecair, h0, dianggapkan cukup nipis supaya kesan graviti boleh diabaikan dan melambung atas oleh gas pasif dan menyambung secara lateral hingga infiniti (Model dua-dimensi). Daya badan yang disebut dalam persamaan Navier-Stokes adalah diubahsuaikan oleh kandungan interaksi antara molekul lebihan (daya apolar dan polar) antara saput bendalir dan permukaan pepejal bergantung kepada daya-daya apolar dan polar. Persamaan Navier-Stokes telah diubahsuai dengan keadaan sempadan berkaitan diselesaikan bawah kaedah pendekatan gelombong panjang untuk memperolehi persamaan perkembangan tak-linear bagi saput antara permukaan. Daya apolar dan polar telah didapati memainkan peranan pencirian atas saput nipis dan kesan utama pada sifat tenaga lebihan bebas, kadar penubuhan, kadar penubuhan maksimum, gelombong neutral, nombor gelombang yang dominan, jarak gelombong dominan dan masa memecah. Oleh demikian, teori linear adalah kurang sesuai untuk menyatakan kestabilan pencirian selaput. Kata kunci: Daya apolar, daya polar, kestabilan linear, kadar pertumbuhan, masa memecah The total excess free energy per unit area (ΔG) of a pure, uncharged thin film on a support is solely derived from the apolar (Lifshitz - van der Waals) and polar (acid-base) intermolecular interactions. Polar interactions are variously described as the hydration pressure, hydrophobic interaction and acid base interaction. The total free excess energy (per unit area) of a thin film on a substrate depends on the film thickness, and the apolar and polar spreading coefficients for the system. The film is modelled as a two-dimensional Newtonian liquid of constant density, ρ and viscosity, μ, flowing on a horizontal plane. The liquid film of mean thickness, h0, is assumed to be thin enough to neglect the gravity effect and bounded above by a passive gas and laterally extends to infinity (two-dimensional model). The body force term in the Navier-Stokes equation is modified by the inclusion of excess intermolecular interactions (apolar and polar forces) between fluid film and the solid surface owing to apolar and polar forces. The modified Navier-Stokes equation with associated boundary conditions is solved under long wave approximation method to obtain a nonlinear equation of evolution of the film interface. The apolar and polar forces were found to play the dominant role in characteristic of thin films and the main effect on the behavior of the excess free energy, growth rate, maximum growth rate, neutral wave, dominant wavenumber, dominant wavelength and rupture time. Hence, the linear theory is inadequate to describe the stability characteristics of films. Key words: Apolar force, polar force, linear stability, growth rate, rupture time

Effects and measurement of internal surface stresses in materials with ultrafine microstructures

1991 ◽  
Vol 6 (5) ◽  
pp. 888-890 ◽  
Author(s):  
R.C. Cammarata ◽  
R.K. Eby
Keyword(s):  
Experimental Data ◽  
Surface Stress ◽  
Lattice Spacing ◽  
Internal Surface ◽  
Crystalline Materials ◽  
Fine Grained ◽  
Stress Effects ◽  
Surface Stresses ◽  
Lamella Thickness ◽  
Order Of Magnitude

Variations in lattice parameters for materials that form very thin lamellae are analyzed using a thermodynamic model that incorporates surface stress effects. It is predicted that lattice spacing variations should be proportional to the reciprocal of the lamella thickness, in agreement with experimental data for polyethylene, n-paraffins, and a copolymer of tetrafluoroethylene and hexafluoropropylene. The model is then used to calculate the surface stress associated with lamella interfaces in these crystalline materials. The calculated surface stress has the same order of magnitude as a surface tension, but is negative. The model is extended so that surface stresses associated with grain boundaries can be measured in very fine-grained metals and ceramics.

Surface Stress Effects On Fracture

1995 ◽  
Vol 409 ◽  
Author(s):  
R.C. Cammarata ◽  
K. Sieradzki
Keyword(s):  
Brittle Fracture ◽  
Surface Stress ◽  
Fracture Criterion ◽  
Crack Tip ◽  
Dislocation Emission ◽  
Simple Analysis ◽  
Stress Effects ◽  
Surface Stresses ◽  
Self Similar ◽  
Brittle Fracture Criterion

AbstractThe effects of surface stress on fracture are reviewed. Calculations by Thomson et al. seem to suggest that surface stresses do not affect cleavage fracture when the crack propagates in a self similar manner even though the surface stress can lead to large stresses near the crack tip. However, surface stresses may have an important effect on dislocation emission near the crack tip. A simple analysis is offered to show how these effects may be incorporated into a modified Rice ductile-brittle fracture criterion by adding a term to the unstable stacking energy that takes into account the energy to form an incipient ledge.

Transient Temperature During the Vaporization of Liquid on a Pulsed Laser-Heated Solid Surface

1996 ◽  
Vol 118 (3) ◽  
pp. 702-708 ◽  
Author(s):  
H. K. Park ◽  
X. Zhang ◽  
C. P. Grigoropoulos ◽  
C. C. Poon ◽  
A. C. Tam
Keyword(s):  
Thin Film ◽  
Solid Surface ◽  
Elevated Temperatures ◽  
Bubble Nucleation ◽  
Transient Temperature ◽  
Specular Reflectance ◽  
Transient Temperature Field ◽  
Excimer Laser Pulse ◽  
Nanosecond Time Resolution ◽  
Laser Heated

The thermodynamics of the rapid vaporization of a liquid on a solid surface heated by an excimer laser pulse is studied experimentally. The transient temperature field is measured by monitoring the photothermal reflectance of an embedded thin film in nanosecond time resolution. The transient reflectivity is calibrated by considering a temperature gradient across the sample based on the static measurements of the thin film optical properties at elevated temperatures. The dynamics of bubble nucleation, growth, and collapse is detected by probing the optical specular reflectance. The metastability behavior of the liquid and the criterion for the onset of liquid–vapor phase transition in nanosecond time scale are obtained quantitatively for the first time.

A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

2002 ◽  
Vol 124 (4) ◽  
pp. 811-814 ◽  
Author(s):  
Chaohui Zhang ◽  
Jianbin Luo ◽  
Shizhu Wen
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Solid Surface ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Thin Film Lubrication ◽  
Lubrication Film ◽  
Viscosity Modification ◽  
Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

scholarly journals The Effects of Surfactant on the Evolution of a Thin Film under a Moving Liquid Drop

2020 ◽  
Vol 5 (1) ◽  
pp. 75-85
Author(s):  
Kartika Yulianti ◽  
Agus Yodi Gunawan ◽  
Edy Soewono
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Solid Surface ◽  
Surfactant Concentration ◽  
Liquid Drop ◽  
Nonlinear Partial Differential Equations ◽  
Normal Pressure ◽  
Lubrication Approximation ◽  
Moving Liquid

The effect of surfactant on the thickness of a thin film bounded by a solid surface and a moving liquid drop was investigated. We proposed a model so that parameters from the liquid drop can be stated in a parameter that acts as normal pressure to the thin film. Using the lubrication approximation, the model was reduced to a set of nonlinear partial differential equations in terms of the film thickness and surfactant concentration. Since we were interested in the role of the surfactant in lifting up the drop, we assumed that the density of the drop is higher than the density of the thin film. Numerically, the results show that the presence of the surfactant tends to delay the decrease of the film thickness insignificantly. However, when the surfactant was added into the system, it tends to significantly increase the film thickness for a certain range value of the normal pressure.

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