Formation of nanoporous Au by dealloying Au Cu thin films in HNO3

AuCu thin films were dealloyed in concentrated HNO3 solution at temperatures of 5-35 degrees C. X-ray diffraction and scanning electron microscopy analysis showed that interior grain regions undergo partial Cu dissolution before being assimilated into a ligament/ void network that was initiated at grain boundaries. The compressive stress generated by removal of the smaller Cu atom yielded an activation energy for ligament growth of 25.4 +/- 2.37 kJ mol(-1), which is less than half that reported for AgAu alloys. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.