| AVS 64th International Symposium & Exhibition | |
| Surface Science Division | Wednesday Sessions |
| Session SS-WeM |
| Session: | Deposition and Growth at Surfaces |
| Presenter: | Shirley Chiang, University of California Davis |
| Authors: | B.H. Stenger, University of California Davis A.L. Dorsett, University of California Davis J.H. Miller, University of California Davis E.M. Russell, University of California Davis C.A. Gabris, University of California Davis S. Chiang, University of California Davis |
| Correspondent: | Click to Email |
The growth of Au on Ge(110) was observed with low energy electron microscopy (LEEM). The objectives of this study were to control the growth of low-dimensional nanostructures and understand the temperature induced motion of islands. Ge(110) was dosed with 0.5-5 ML of Au and heated to 850°C. During deposition, liquid eutectic alloy islands formed on the surface and grew to ~1-2 µm in width and ~2-5 µm in length, elongated along the [1,-1,0] direction due to an anisotropy in the dissolution rate of the substrate. Low energy electron diffraction (LEED) showed a transition from a (4x5) phase to a (2x1) phase immediately preceding island growth. A temperature gradient of 0.017°C/µm across the surface induced a Ge concentration gradient in the islands and diffusion of Ge through the islands from high to low temperature. Dissolution of Ge at the undersaturated high temperature end of the island and crystallization of Ge at the supersaturated low temperature end resulted in movement of the islands toward higher temperature. Smaller islands, unable to overcome pinning effects, remained stationary, while larger islands moved with velocities of 0.1-1.0 µm/s. Island velocities are consistent with a model of diffusion limited motion. Upon collision islands merged, increasing in size up to ~60 µm in width and ~100 µm in length. The direction of movement was restricted to the [1,-1,0] direction by the same dissolution anisotropy that causes island elongation during the growth process, with the exception of very large islands for which the direction was determined only by the temperature gradient. Optical microscopy confirmed that the largest islands moved from the cooler edges of the sample toward the hotter center of the sample. As the temperature decreased, the island behavior was also studied and revealed rapid island contractions as Ge crystallizes out from the islands, leaving a visible outline of the original extent of the island.