Self-assembly of small structures
Small structures are formed by applying to a substrate a structural material and a layer of a sacrificial material having a lower surface energy than the structural material, to form an intermediate product. The substrate is then heated to a temperature at which the sacrificial material evaporates or sublimes and the structural material is mobilized. The sacrificial material is permitted to evaporate or sublime, an area of the substrate covered by the sacrificial material to diminish, and the structural material to agglomerate on the remaining sacrificial material to form a structure.
1. A method of forming sub-micrometer structures, comprising:
applying to a substrate a structural material and a layer of a sacrificial material;
maintaining the substrate at a temperature at which the sacrificial material evaporates or sublimes and the structural material is mobilized; and
permitting the sacrificial material to progressively evaporate or sublime, thereby diminishing a remaining area of the substrate covered by the sacrificial material; and
permitting the structural material from parts of the area where the sacrificial material has evaporated or sublimed to agglomerate on the remaining sacrificial material to form a said structure.
2. The method of claim 1 , wherein the sacrificial material has a lower surface energy than the structural material.
3. The method of claim 1 , further comprising continuing the agglomeration until the sacrificial material covering said area of the substrate disappears, leaving a structure comprising said structural material on said substrate.
4. The method of claim 1 , wherein said applying comprises applying one or more discrete portions of said sacrificial material centered on intended locations of said structures.
5. The method of claim 1 , wherein said applying comprises applying a continuous layer of said structural material.
6. The method of claim 1 , comprising applying said layer of said sacrificial material on said substrate, and applying said layer of said structural material on said sacrificial material, and wherein permitting the sacrificial material to evaporate or sublime comprises permitting the sacrificial material to evaporate or sublime at edges of the layers of said structural and sacrificial materials.
7. The method of claim 6 , further comprising applying a layer of a third material on said sacrificial material and applying said layer of structural material on said third material.
8. The method of claim 6 , wherein said layer of said structural material is a discontinuous monolayer comprising discrete instances of said structural material, and wherein permitting the sacrificial material to evaporate or sublime comprises permitting the sacrificial material to evaporate or sublime at gaps in the layer of said structural material to form additional said edges.
9. The method of claim 1 , wherein said sacrificial material is selected from the group consisting of antimony, arsenic, bismuth, cadmium, lead, silver, tellurium, zinc, CdTe, and Bi 2 Te 3 .
10. The method of claim 1 , wherein said structure comprises an alloy of said structural material and said sacrificial material.