Size distribution and dot shape of self-assembled quantum dots induced by ion sputtering

The variation of the size distribution and dot shape of the GaSb quantum dots (QDs) induced by ion sputtering with sputtering time was investigated by high-resolution atomic force microscopy (AFM). The results showed that the range of the size distribution firstly becomes broad with the sputtering time below 150 s; after this time, it starts to decrease and then keep quite constant at a long time. Meanwhile, the GaSb QDs undergo a shape transition from partly dome to cone, and finally develops into complete dome structure. These transitions can be explained by the change in chemical potential, as suggested by Ross et al. (Phys. Rev. Lett. 80 (1998) 984).