Controlled ligament coarsening in nanoporous gold by annealing in vacuum versus nitrogen

The structural evolution of nanoporous gold during thermal treatment was studied by annealing samples in vacuum and in flowing nitrogen. As expected, ligament thickness generally increased in both environments. However, ligaments annealed at high temperature in vacuum remained relatively narrow, undergoing much less coarsening than nitrogen-annealed samples, albeit with some ligament agglomeration. When annealed in flowing nitrogen, gold ligaments coarsened significantly at temperatures above 300 degrees C. This discrepancy is attributed to different surface diffusion rates of gold in the two annealing environments. The current results suggest that diffusion on the surfaces of nanoporous gold ligaments proceeds more quickly in nitrogen than in vacuum.