Controlling Gold Atom Mobility in Nanocomposite Films Through Zirconia Co-Deposition—An In Situ TEM Investigation

The thermal behavior and dewetting dynamics of nanocomposite thin films composed of gold and zirconia (ZrO₂) have been investigated by <i>in situ</i> heating transmission electron microscopy (upon low electron dose) and molecular dynamics simulations. Gold nanostructured films with branched microstructure, both with and without zirconia, were subjected to thermal stimuli to observe their response. In pure gold films, thermally induced solid-state dewetting initiated at temperatures just above 100°C, causing a gradual retraction of gold clusters. This process progressed slowly until around 800°C, then accelerated significantly, reducing the gold-covered substrate area from 47% to 10% by 1000°C.<br/>The inclusion of zirconia significantly enhanced the thermal stability of the gold films. Indeed, ZrO₂ clusters limited the mobility and diffusivity of gold atoms, raising the temperature threshold for dewetting and reducing its rate, thereby improving the overall thermal resilience of the films. Specifically, gold-zirconia nanocomposite films demonstrated much slower dewetting and greater retention of substrate coverage compared to pure gold films. The MD simulations corroborated these findings, showing that the introduction of zirconia decreased gold atom diffusivity by approximately a factor of three, due primarily to zirconia's high melting point and associated thermal threshold.<br/>These results highlight zirconia as a critical stabilizing agent in nanostructured materials, effectively mitigating gold dewetting at elevated temperatures while preserving the structural integrity of the films. This improved thermal stability opens new opportunities for tailoring the thermal properties of nanocomposite thin films, with potential applications in advanced technologies requiring robust thermal performance.