Thermally induced structural modification in the Al/Zr multilayers

TL;DR

This study investigates how increasing temperature affects the microstructure and phase transformations of Al/Zr multilayers, revealing significant changes at 250°C and complete phase transformations near 300°C, with implications for their thermal stability.

Contribution

It provides a detailed analysis of thermally induced microstructural changes in Al/Zr multilayers using multiple characterization techniques, highlighting the evolution of interfacial phases and structural stability.

Findings

Significant structural changes occur at 250°C with asymmetric interlayers.

At around 290-298°C, amorphous Al-Zr alloys transform into crystalline phases.

Multilayer structures persist up to 500°C despite phase transformations.

Abstract

The effect of increasing temperature on the structural stability and interactions of two kinds of Al/Zr (Al(1%wtSi)/Zr and Al(Pure)/Zr) multilayer mirrors are investigated. All Al/Zr multilayers annealed from 200^{\circ}C to 500^{\circ}C, were deposited on Si wafers by using direct-current magnetron sputtering technology. A detailed and consistent picture of the thermally induced changes in the microstructure is obtained using an array of complementary measurements including grazing incidence X-ray reflectance, atomic force microscope, X-ray diffraction and high-resolution transmission electron microscopy. The first significant structural changes of two systems are observed at 250^{\circ}C, characterized by asymmetric interlayers appears at interface. At 290^{\circ}C, the interface consisted of amorphous Al-Zr alloy is transformed to amorphous Al-Zr alloy and cubic ZrAl3 in both systems. By 298^{\circ}C of Al(1%wtSi)/Zr and 295^{\circ}C of Al(Pure)/Zr multilayers, the interfacial phases of Al-Zr alloy transform completely into polycrystalline mixtures of hcp-ZrAl2 and cubic-ZrAl3, which smooth the interface boundary and lower the surface roughness in the multilayers. Up to 500^{\circ}C, the multilayer structure still exists in both systems, and the differences between the asymmetric interlayers are much larger in the multilayers. Finally, we discuss the transformation from symmetric to asymmetric in the annealing process for other systems.