Experimental evaluation of the role of oxygen on the growth of MgOx nano-sculpted thin films synthesized by reactive magnetron sputtering combined with glancing angle deposition

Abstract

In this work, we have studied the influence of oxygen on the chemistry and morphology of nano-sculpted MgOx thin films prepared by magnetron sputtering in glancing angle configuration. First, we have studied the poisoning mechanism of the Mg target by² combining target voltage and deposition rate measurements with chemical analysis of the deposited films by X-ray Photoelectron Spectroscopy. The results reveal a strong metal-to-compound transition at very low oxygen flows, namely < 5% of O2 in the gas mixture. This transition is accompanied by a dramatic decrease of the deposition rate (by 95%) and by the synthesis of fully oxidized films. Then, for thee gaseous mixtures corresponding to the metallic conditions as well as to the edges of the metal-to-compound transition, namely 0%, 2.5% and 5% of O2 in the gas mixture, nano-sculpted films have been grown. From SEM images, it appears that even a slight amount of O2 in the gas mixture strongly affects the morphological features of the films by reducing the width of the tilted columns (by 50% for 2.5% of O2) as well as the intercolumnar space (by 85% for 2.5% of O2). This has been understood by considering the growth mechanism of thin films in reactive conditions and the Structural Zone Model associated with these conditions.