Effect of annealing atmosphere on the thermal coarsening of nanoporous gold films

SEM images of the NPG films annealed at different atmospheres for 2 h. (a-c) Annealed at 200, 300, and 400 °C in O2, respectively; (d-f) annealed at 300, 400, and 500 °C in Ar, respectively; (g-i) annealed at 400, 500, and 600 °C in CO, respectively. All SEM images have the same scale bar.