Structure and Chemical Characterization at the Atomic Level of Reactions in Al/CuO Multilayers

Abstract

Sputter-deposited Al/CuO multilayers exhibit fast combustion reactions in which an exothermic chemical reaction wave—controlled by the migration of oxygen atoms from the oxide matrix toward the aluminum layers through interfacial layers—moves throughout the multilayer at subsonic rates (meters per second to tens of meters per second). We directly observed the structural and chemical evolution of Al/CuO/Al multilayers upon heating to 700 °C using high-magnification transmission electron microscopy (TEM) and scanning TEM, providing simultaneous sub-nanometrer imaging resolution and detailed chemical analysis. Interestingly, as deposited, the trilayer is characterized by two distinct interfacial layers: 4.1 ± 0.2 nm thick amorphous alumina and a 15 ± 5 nm thick mixture of AlOx and CuxAlyOz, at the bottom interface and top interface, respectively. Upon heating, we accurately characterized the evolving nature and structure of these interfaces, which are rapidly replaced by the reaction terminal oxide (Al2O3). ...