Molecular-Scale Mlcroporous Superlattices

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Abstract
We have been interested in fabricating structures which can have dimensions on the scale of molecules (˜10 Å). By producing lithographic structures on the molecular-scale length, we obtain a new class of materials with unusual chemical properties. The materials contain pores which have been shown to restrict the mobility and adsorption of molecules. This restriction is the basis of size- and shape-selective chemistry which is used in many modern separation and catalytic processes. Features in our materials are significantly smaller than the smallest nano-structures produced with electron beam lithography. To date 20–50 Å features have been produced with electron beam lithography which uses ionization from beam-solid interactions to drive radiation chemistry in a resist layer. These dimensions are near fundamental limits which come from beam-solid interactions and the response of the resist system. Further limitations occur when the nanostructural pattern must be transferred from the resist layer into a useful metal or semiconductor structure. Methods have not been devised to fully exploit the accuracy with which resist patterns can be defined, and the smallest useful transferred structures have dimensions of ˜80–100 Å. To produce the smallest of all lithographic structures, we use a new method for pattern generation. Instead of using radiation chemistry to define a pattern, we use the organization of layers in deposited superlattices.

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