Oswald ripening and shape transitions of self-assembled PbSe quantum dots on PbTe (111) during annealing

The thermal stability of faceted self-assembled PbSe quantum dots during an nealing is investigated. With increasing annealing time, the dot density is found to decrease rapidly with a simultaneous increase of the average isla nd volumes. In addition, a shape transition from pyramidal islands to trunc ated pyramids is observed for islands exceeding a critical height of 160 An gstrom. The evolution of island volumes and densities is consistent with Os wald ripening by interface-reaction-limited mass transfer. This is a clear indication that the as-grown islands do not represent an equilibrium struct ure and that their narrow size dispersion is a purely kinetic effect. (C) 2 000 American Institute of Physics. [S0003-6951(00)02045-3].