Stability of Artificial Multilayers
This paper is a tutorial overview of the factors that affect the stability of artificial multilayers. First, the basic thermodynamics of solutions will be briefly reviewed. Next, the stability of multilayers with continuous structure will be considered. In these multilayers the structure is the same throughout the film and the layering corresponds to a modulation of the composition. Examples are the face-centered cubic films with a  texture studied first by Hilliard and co-workers at Northwestern, and amorphous metal or amorphous semiconductor films. Depending on the thermodynamics of the system, the composition modulation can either disappear or sharpen by diffusion. For short modulation repeat lengths, this process must be analyzed with the Cahn-Hilliard theory for the free energy of inhomogeneous systems, which takes into account the contributions from composition gradients. The effect of elastic strain, first formulated by Cahn, needs to be taken into account as well. For large amplitude modulations, the diffusion equations may also become non-linear.
KeywordsFree Energy Fault Line Repeat Length Composition Profile Total Free Energy
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