Elementary Surface Chemistry during CuO/Al Nanolaminate-Thermite Synthesis: Copper and Oxygen Deposition on Aluminum (111) Surfaces

Abstract

The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species.

Engineering of Al/CuO Reactive Multilayer Thin Films for Tunable Initiation and Actuation

“…Previsous detailed theoretical investigation in [26] suggested that CuO is partially reduced in the vicinity of the interface and a pre-mixed layer with a thickness of several nm exists between the Al and CuO layers.…”

A perfect wetting of Mg monolayer on Ag(111) under atomic scale investigation: First principles calculations, scanning tunneling microscopy, and Auger spectroscopy

“…In the context of all-integrated stacked layers and extreme miniaturization of devices, control of interfaces in Microelectronics has become a major scientific and technological challenge in past decades 1,2 . To achieve nanoscale-controlled layer, new technological approaches for asdeposited atomically-controlled layers must be developed [3][4][5] and that cannot be fully exploited without a fundamental knowledge of interfacial effects and atomic organization such as surface dynamics, bonding, ordering, and intermixing of the atoms [6][7][8][9][10][11][12][13][14] . Recent efforts have been provided to develop new technological processes to design controlled stacked layers directly integrated, as for instance Atomic Layer Deposition and Oxidation method (ALDO) 3 through a careful control of surface reaction at each step of the process [15][16][17][18][19] .…”

Reactive Structural Materials: Preparation and Characterization

“…It has been recognized, however, that poorly defined phases exist at the interfaces between the reactive components deposited on top of each other by sputtering. To avoid uncontrollable formation of the intermediate reaction products, additional layers were formed between the reactive components by atomic layer deposition . Such layers, although still serving as diffusion barriers, can be better controlled, leading to a more predictable behavior of the RM system.…”