Morphological and mechanical properties study of [WO 3/W] n nanoscale multilayers

Abstract

Microstructure, morphology and hardness of W, WO 3 single layers and WO 3/W multilayers with various period thicknesses have been studied. Films have been deposited via RF sputtering at a working pressure of 0.5 Pa and with a power density of 1.18 W/cm 2. W layers are crystallised. WO 3 single layers were investigated with various oxygen partial pressure ( P O 2 =10–30%). The roughness increases with P O 2 . This phenomenon is ascribed to active resputtering of the deposited layer by oxygen ions. For a P O 2 =10%, the layer possesses a stoichiometric composition WO 3, an amorphous structure and a homogeneous surface morphology. P O 2 =10% was chosen to performed WO 3/W multilayers, in order to elaborate amorphous/crystallised multilayers and to study their mechanical properties. Several period thicknesses ( Λ) have been investigated and X-ray reflectivity patterns reveal a multilayered structure even for the lowest Λ of 2 nm. Nevertheless, no effects of the period thickness on the hardness were observed which is in disagreement with Hall Petch and Lehoczky theories.