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Characterization of Thin Organic and Polymeric Films by Spectroscopic Methods
Published online by Cambridge University Press: 29 November 2013
Extract
Much of the anisotropic mechanical and thermal behavior exhibited by materials can be attributed to anisotropic orientation at the molecular level. In self-supporting thin films (5–10 microns) and those (0.01–1.0 microns) deposited on solid substrates, the role of molecular orientation is even more important since it will critically determine their two-dimensional behavior and their structural integrity as well. These two aspects are extremely important because if thin organic and polymeric films are to be competitive with existing materials for such diverse applications1 as chemical sensors and integrated optics, they must be mechanically robust and, ideally, defect free. These stringent constraints dictate that sophisticated characterization techniques, which can interrogate at the molecular level, be developed or refined so as to have the sensitivity to address these critical issues.
The development of nondestructive techniques for studying thin organic films has certainly lagged behind those developed for metallic and semiconductor films. Unfortunately, many of these same techniques cannot be simply applied to organic films because they are “invasive” and often alter the structure of the system they were designed to probe. This is especially so in organic and polymer films, and this awareness within the materials science community has led to the adaptation of many photon intensive techniques to the study of thin films. A number of these will be discussed in later sections with their relative merit put in perspective.
Certainly the origins of anisotropic structure in bulk materials are manyfold, but the spatial constraints in 2-D can lead to even more complex causes of orientation. In thin films on substrates the role of the surface is important in determining the ordering and orientation of the individual molecular segments which come into intimate contact with it. The extent of this orientation and order is still somewhat controversial but there is general agreement that it probably differs depending on the nature of the substrate.
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- Copyright © Materials Research Society 1987
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