NATURE OF LUMINESCENT SURFACE-STATES OF SEMICONDUCTOR NANOCRYSTALLITES

We present semiempirical tight-binding and ab initio local density cal culations demonstrating the (meta)stability of self-trapped excitons a t the surface of silicon nanocrystallites; These are obtained for dime r bonds passivated, for instance, by hydrogen atoms or by silicon oxid e. Light emission from these trapped excitons is predicted in the infr ared or in the near visible. We are thus led to the interpretation tha t part of the luminescence is due to such surface states while optical absorption is characteristic of quantum confinement effects. These co nclusions should extend to other semiconductor crystallites.