Guided acoustic waves of an adlayer deposited on a superlattice

We show that the degree of localization of guided acoustic modes associated with an adlayer can be increased if the substrate is a superlattice instea d of being a homogeneous medium. This is due to the existence of minigaps, and also of two types of polarization for the minibands, which may prohibit the propagation of these modes into the superlattice. As a consequence.. t he experimental observation of the pseudo-guided modes induced by the adlay er can become possible, or at least facilitated. To demonstrate theoretical ly this new idea, we study the localized and resonant modes of an adlayer d eposited on a superlattice which are obtained as well-defined peaks of the total and local density of states, calculated by means of a Green's functio n method. (C) 2001 Elsevier Science Ltd. All rights reserved.