Dielectric properties of semiconductor clusters

The static electric polarizability alpha of Si-N, GaNAsM and GeNTeM clusters in a molecular beam, with nozzle temperatures ranging from 38 to 300 K; were investigated from their deflections in an inhomogeneous electric field. A striking size dependence is observed for small GaNAsM and Si-N clusters. Specifically. for GaNAsM clusters with up to 15 atoms, the polarizability oscillates strongly between low values for even numbers of atoms N + M and high values for odd numbers of atoms N + M. This behavior of alpha as a function of size can be understood by a widening of the band gap and additional occurrence of defect-like electronic states. The temperature dependence of the polarizability of most GeNTeM clusters indicates the importance of vibronic (ionic) contributions to alpha. This may be related to the ferroelectric behavior of bulk GeTe.