NOVEL COARSENING OF Pb NANOSTRUCTURES ON Si(111) 7 X 7
In order to study a possible means of controlling the growth of an epitaxically grown, self-assembled nanostructure, Pb/Si(111) was analyzed. An atomically clean Si(111) 7 X 7 crystal was prepared under Ultra High Vacuum (UHV) conditions followed by Pb deposition. The islands were monitored over time with a Scanning Tunneling Microscope (STM) to see how they coarsen (the process of smaller islands disappearing and larger islands growing even larger) and determine the applicability of the classical theory of Ostwald ripening. STM Images of the resulting Pb islands were taken as they evolved in time. Height measurements indicated that initially, the majority of islands (25 out of 33) were 4 or 5 layer islands, but by the end of the experiment 68 minutes later, the majority (18 out of 24 islands) were 7 or 9 layer islands. Additional measurements of the area indicate that the total area of all the islands was reduced by 10%, but the total coverage increased by ~40%, presumably coming from the wetting layer. Measurements of island area and height over time indicated that an increase in height was accompanied by a sudden (within 2-3 minutes) increase in volume and decrease in area. Interestingly, some islands grew by adding a ring of higher height around the edge before fi lling in the center. These rings, on average, would fi ll in less than 5 minutes. Generally, the islands started with a random shape, and gradually became more like a regular hexagon over time. These observations are very unusual because they do not fi t the classical expectations based on Ostwald ripening and they show the role of Quantum Size Effects upon the coarsening process.
- Research Organization:
- DOESC (USDOE Office of Science (SC) (United States))
- Sponsoring Organization:
- USDOE Office of Science (SC)
- OSTI ID:
- 1052048
- Journal Information:
- Journal of Undergraduate Research, Vol. 7
- Country of Publication:
- United States
- Language:
- English
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