DIELECTRIC-PROPERTIES OF SEMICONDUCTOR CLUSTERS

The static electric polarizability alpha of Si-N, GaNAsM and GeNTeM cl usters in a molecular beam, with nozzle temperatures ranging from 38 t o 300 K; were investigated from their deflections in an inhomogeneous electric field. A striking size dependence is observed for small GaNAs M and Si-N clusters. Specifically. for GaNAsM clusters with up to 15 a toms, the polarizability oscillates strongly between low values for ev en 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 el ectronic states. The temperature dependence of the polarizability of m ost GeNTeM clusters indicates the importance of vibronic (ionic) contr ibutions to alpha. This may be related to the ferroelectric behavior o f bulk GeTe.