### 3.3.3 Summary to: 3.3 Nucleation and Growth

| Deposition of a thin layer must start with a "clean" substrate surface on which the first atomic / molecular layer of the film must nucleate. |  |
| There are many possible interactions between the substrate and "first" incoming atoms. |
|  | As the interaction energy goes up we move from "some" absorption to physisorption (secondary bonds are formed) to chemisorption (full bonding) |
|  | The sticking coefficient is a measure of the likelihood to find an incoming atom in the thin film forming. |
|  | Immobilization by some bonding is more likely at defects (= more partners). The initial stage of nucleation is thus very defect sensitive. |
| Simple surface steps qualify as efficient "defects" for nucleation. |  |
|  | Small deviations from perfect orientation provide large step densities. Nucleation therefore can be very sensitive to the precise {hkl} of the surface |
|  | Intersections of (screw) dislocation lines with the surface also provide steps. |
|  | This may cause grain boundaries and other defects in the growing layer. |
|  | Scanning probe microscopy gives the experimental background |
| There is always a nucleation barrier that has to be overcome for the first B-clusters" to form on A |  |
|  | the three involved interface energies, all expressed in the "wetting angle", plus possibly some strain are the decisive inputs for the resulting growth mode. Frank - van der Merve: Smooth layer-by-layer growth Vollmer - Weber: Island growth Stranski - Krastanov: Layer plus island growth |
Exercise 3.3-1
All Questions to 3.3

© H. Föll (Semiconductor Technology - Script)