Annealing of gold nanolayers sputtered on polyimide and polyetheretherketone

• Surface morphology of annealed polymer substrates was examined by AFM.
• Growth of Au nanolayers deposited by sputtering method on substrates was studied.
• Changes of UV–Vis absorption spectra of Au nanolayers were observed.
• Annealing of Au nanolayers was performed, structural changes were studied.

Annealing of thin Au films sputtered on polyimide (PI) and polyetheretherketone (PEEK) polymer substrates was carried out to study influence of substrate on surface morphology transformation and possible “dewetting”, which was observed in the past on glass substrates. Thermal stability of substrates was studied by differential scanning calorimetry, PI substrate was found to be stable up to 400 °C, PEEK undergoes crystallization at circa 170 °C and melts at circa 320 °C. Therefore, annealing temperatures of 200 °C and 300 °C were chosen for PEEK and PI respectively. Surface morphology of the samples was studied by atomic force microscopy. Annealing of the PEEK substrate leads to significant changes of its surface structure, a rugged structure is formed. A sufficiently thin Au layer is then broken into islands, thicker layers however cover the substrate structure. Annealing of Au layers on PI substrate leads to formation of coarser Au nanoislands with narrower size distribution, but the layer remains continuous. The UV–Vis absorption spectra show a rise of surface plasmon resonance peak after annealing, which documents the formation of uniform nanostructure. The peak is most evident at the thinnest Au layers. The results suggest the PI is an interesting substrate capable of supporting very thin metal films and preventing their dewetting during annealing.