Reactive multilayer systems represent an innovative approach for potential usage in chip joining applications. As there are several factors governing the energy release rate and the stored chemical energy, the impact of the morphology and the microstructure on the reaction behavior is of great interest. In the current work, 3D reactive microstructures with nanoscale Al/Ni multilayers were produced by alternating deposition of pure Ni and Al films onto nanostructured Si substrates by magnetron sputtering. In order to elucidate the influence of this 3D morphology on the phase transformation process, the microstructure and the morphology of this system were characterized and compared with a flat reactive multilayer system on a flat Si wafer. The characterization of both systems was carried out before and after a rapid thermal annealing treatment by using scanning and transmission electron microscopy of the cross sections, selected area diffraction analysis, and differential scanning calorimetry. The bent shape of multilayers caused by the complex topography of silicon needles of the nanostructured substrate was found to favor the atomic diffusion at the early stage of phase transformation and the formation of two intermetallic phases Al_0.42Ni_0.58 and AlNi₃, unlike the flat multilayers that formed a single phase AlNi after reaction.

Reactive multilayer systems are nanostructures of great interest for various technological applications because of their high energy release rate during the self‐propagating reaction of their components. Therefore, many efforts are aimed at controlling the propagation velocity of these reactions. Herein, reactive multilayer systems of Al/Ni in the shape of free‐standing foils with a wavelike surface morphology prepared by using sacrificial substrates with well‐aligned waves are presented and the propagation of the reaction along different directions of the reproduced waves is analyzed. During the ignition test, the propagation front is recorded with a high‐speed camera, and the maximum temperature is measured using a pyrometer. The propagation of the reaction is favored in the direction of the waves, which points out the influence of the anisotropy generated by this morphology and how it affects the propagation dynamics and the resulting microstructure. Furthermore, compared to their counterparts fabricated on flat substrates, these reactive multilayers with wavelike morphology exhibit a remarkable reduction in the propagation velocity of the reaction of about 50%, without significantly affecting the maximum temperature registered during the reaction.

The chemical energy released as heat during the exothermic reaction of reactive multilayer systems has shown potential applications in various technological areas, e.g., in joining applications. However, controlling the heat release rate and the propagation velocity of the reaction is required to enhance their performance in most of these applications. Herein, a method to control the propagation velocity and heat release rate of the system is presented. The sputtering of Al/Ni multilayers on substrates with periodic 2D surface structures promotes the formation of growth defects into the system. This modification in the morphology locally influences the reaction characteristics. Tailoring the number of 2D structures in the substrate enables the control of the velocity and maximum temperature of the propagation front. The morphology of the produced reactive multilayers is investigated before and after reaction using scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. In addition, the enthalpy of the system is obtained through calorimetric analysis. The self‐sustained and self‐propagating reaction of the systems is monitored by a high‐speed camera and a high‐speed pyrometer, thus revealing the propagation velocity and the temperatures with time resolution in the microsecond regime.

Reactive multilayers comprising alternating nanoscale layers of Al and Ni exhibit potential across various applications, including localized heating for welding and joining. Control over reaction properties is pivotal for emerging applications, such as chemical time delays or neutralization of biological or chemical weapons. In this research, insights are offered into the intricate interplay between substrate thickness, surface roughness, and the behavior of Al/Ni reactive multilayers, opening avenues for tailored applications in various domains. To observe this interplay, silica with various thicknesses from 0.4 to 1.6 μm is deposited on polished single‐crystalline Si and rough poly‐Si base substrates. Additionally, to analyze the impact of varying silica thickness along the sample length on reaction behavior, silica in steplike shape is fabricated. Subsequently, Al/Ni multilayers with 5 μm total thickness and 20 or 50 nm bilayer periodicities are deposited. Reaction velocity and temperature are monitored with a high‐speed camera and pyrometer. In the results, it is indicated that silica thickness significantly affects self‐propagation in multilayers. The reaction is not self‐sustained for silica layers ≤ 0.4 μm, depending on bilayer periodicity and substrate roughness. The velocity increases or decreases based on the direction of reaction propagation, whether it moves upward or downward, in relation to the thickness of silica.

Surface structuring methods are crucial in semiconductor manufacturing, as they enable the creation of intricate structures on the semiconductor surface, influencing the material's electrical, mechanical, and chemical properties. Herein, one such structuring method known as reactive ion etching to create black Si structures on silicon substrates is employed. After thermal oxidation, their influence on the reaction of Al/Ni nanoscale multilayers is studied. It reveals distinct reactive behaviors without corresponding differences in energy release during differential scanning calorimetry measurements. Higher oxidized black Si structure densities result in elevated temperatures and faster reaction propagation, showing fewer defects and reduced layer connections in cross‐sectional analyses. The properties of the reactive multilayers (RML) on high structure density show the same performance as a reaction on flat thermal SiO₂, causing delamination when exceeding 23 structures per μm². Conversely, lower structure density ensures attachment of RML to the substrate due to an increased number of defects, acting as predetermined breaking points for the AlNi alloy. By establishing the adhesion between the reacted multilayer and the substrate, surface structuring could lead to a potential increase in bond strength when using RML for bonding.

Free‐standing Ni/Al multilayer films with a planar morphology, a bilayer thickness of 20 nm, and an average composition of Ni₅₀Al₅₀ (at%) deposited by direct current magnetron sputtering are investigated by nanocalorimetry and conventional calorimetry. Both the novel fast differential scanning calorimeter (FDSC) Flash DSC 2+ from Mettler–Toledo (MT) and conventional calorimeter MT DSC 3 are used to cover a range of heating rates from 0.1 to 10⁴ K s⁻¹. A quantitative kinetic study of the interdiffusion and phase reaction sequence is performed via a Kissinger analysis covering five orders of magnitude of heating rates. Using the calorimetric data, the derived apparent activation energies suggest monotonic reaction kinetics over the entire range of heating rates applied. To correct the thermal lag at the highest heating rates with the FDSC for nonadhered free‐standing films, a new methodology for its correction is used. Overall, this work extends the application of commercial FDSC to nonadhered films.