Surfaces, Interfaces, and Changing Shapes in Multilayered Films
Surfaces, Interfaces, and Changing Shapes in Multilayered Films
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DOI：
10.1557/s0883769400051538
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发表时间：
1999-02
期刊：
影响因子：
5
通讯作者：
D. Josell;F. Spaepen
中科院分区：
文献类型：
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作者：
D. Josell;F. Spaepen
通常认为，与内部和外部界面相关的毛细力影响液体-蒸汽表面的形状和液体对固体的润湿。人们不太理解的是，同样的现象学通常同样适用于固-固或固-汽界面。控制毛细现象的基本量是与单位面积界面有关的过剩自由能。这种过剩自由能的微观起源通常直观上很容易理解：自由表面的原子有“丢失的键”;晶界含有“空穴”，因此没有最佳的电子密度;非相干界面含有位错，这会消耗应变能;固液界面附近的液体有序化导致熵降低，因此自由能增加。在下文中，我们将说明这个基本量如何决定越来越复杂的物体的形状：球体、线、薄膜以及由液体或固体组成的多层膜。这里不考虑晶体的各向异性;假设所有的界面和表面都是各向同性的。考虑半径为R的球形液滴与表面自由能γ的平衡表明，液滴内部的压力高于外部。这个差别由著名的拉普拉斯方程给出：这个结果可以通过在半径的无限小变化期间对内部和外部压力所做的功与创建新表面的功相等来获得。
It is generally recognized that the capillary forces associated with internal and external interfaces affect both the shapes of liquid-vapor surfaces and wetting of a solid by a liquid. It is less commonly understood that the same phenomenology often applies equally well to solid-solid or solid-vapor interfaces. The fundamental quantity governing capillary phenomena is the excess free energy associated with a unit area of interface. The microscopic origin of this excess free energy is often intuitively simple to understand: the atoms at a free surface have “missing bonds”; a grain boundary contains “holes” and hence does not have the optimal electronic density; an incoherent interface contains dislocations that cost strain energy; and the ordering of a liquid near a solid-liquid interface causes a lowering of the entropy and hence an increase in the free energy. In what follows we shall show how this fundamental quantity determines the shape of increasingly complex bodies: spheres, wires, thin films, and multilayers composed of liquids or solids. Crystal anisotropy is not considered here; all interfaces and surfaces are assumed isotropic. Consideration of the equilibrium of a spherical drop of radius R with surface free energy γ shows that pressure inside the droplet is higher than outside. The difference is given by the well-known Laplace equation: This result can be obtained by equating work done against internal and external pressure during an infinitesimal change of radius with the work of creating a new surface.