Effects of nano-silicon layer thickness

on surface acoustic wave velocities

 

A. Doghmane*, I. Hadjoub, Z. Hadjoub

Laboratoire des Semi-Conducteurs, Département de Physique, Faculté des Sciences, Université Badji-Mokhtar, B.P 12,

Annaba, DZ-23000, Algeria.

* Corresponding author. E-mail: a_doghmane@yahoo.fr

Received: 30 September 2006; revised version accepted: 05 March 2008

 

Abstract

     The properties of nanosilicon layers are receiving a great deal of interest as a result of their potential nanotechnological applications. In this context, we investigated two types of nano-layers (315- and 915-atom systems) when deposited on SiO2 and Si substrates. We first deduced surface acoustic wave velocities, then determined the acoustic responses from which Rayleigh wave velocities were deduced, for both types of agglomerations. Finally, the influence of varying layer thickness on wave velocities was put into evidence. The results, thus obtained, showed two opposite dispersive behaviors. In loading effect, the SAW velocity decreases initially from the value of that of the substrate, then saturates when it approaches that of the nano-Si layers, i.e; (VR)n-315 = 4367 m/s and (VR)n-915 = 4275 m/s. The inverse behavior, an initial increase followed by a saturation region, was obtained for the stiffening effect with SiO2 substrates. Moreover, we noticed some anomalous behaviors consisting of a small plateau in the increasing region of the stiffening effect and of some valleys in loading effect which were attributed to differences in densities and wave velocities.

 

Keywords: Nano-Silicon; Thickness;Surface acoustic waves; Velocity dispersion; stiffening effect; loading effect.

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