A Study of the Spinodal Decomposition of Ag-Cu Alloy Films Using In Situ Transmission Electron Microscopy

Abstract

We performed in situ transmission electron microscopy (TEM) investigations to understand spinodal decomposition in Ag-Cu alloy thin films. The decomposition of a homogeneous nanocrystalline morphology into a heterogeneous two-phase structure when annealed in situ from room temperature to 400 °C was investigated with different imaging modes in the TEM. These studies reveal phase transformation proceeds in stages: between 180 – 200 °C, onset of phase separation via spinodal decomposition is observed. Then, prominent phase separation occurs between 200 – 250 °C with minimal grain growth. Next, between 250 – 300 °C, grain growth primarily occurs via coalescence, with no apparent phase separation. From 300 – 350 °C, we observe significant phase separation and Ostwald Ripening. Finally, between 350 – 400 °C, further coarsening occurs via coalescence. STEM-HAADF mode reveals the onset of phase separation from domains as small as 5 nm and these results are also supported by electron diffraction and compositional mapping.

Keywords: In Situ Transmission Electron Microscopy, Phase Transformations, Spinodal Decomposition, Alloy Thin Films.