Influence of O content on exothermic and self-propagating characteristics of Ti/SiOx multilayer films

In this paper, the influence of O content on the exothermic and self-propagating characteristics of Ti/SiOx films is reported. 2 μm-thick multilayer films with various atomic ratios and bilayer thicknesses are prepared using a tertiary-source magnetron sputtering system with DC/RF multifunction cathodes. DC, DC, and RF modes are used for depositing Ti, Si, and SiO2 films, respectively, where cosputtering of Si and SiO2 is conducted to control O content in SiOx film layers. Threshold powers for exothermic reaction estimated by electric spark and laser irradiation depend on the Ti to Si ratio and bilayer thickness, whereas reaction propagation speed and maximum temperature mainly depend on the bilayer thickness and the Ti to Si ratio, respectively. The three characteristics are influenced by O content. The heat of reaction also shows both bilayer thickness and Ti to Si ratio effects, and it decreases with increasing O content. In the Ti/Si films, the exothermic reaction propagates completely into the films, whereas in the Ti/SiOx films, self-propagation of the exothermic reaction becomes difficult with increasing O content. The cause of the influence of O content on reaction propagation characteristics is discussed from the viewpoint of a change of heat balance with increasing O content in the Ti/SiOx films.