BSTRACTCompression of nanoporous gold

in situ

under electrochemical control reveals that its flow stress can be enhanced by surface coverage of monolayer oxide. Here we present a study on the monolayer oxide induced changes in flow stress of an nanoporous gold

while the ligament size is varied by more than 2 orders of magnitude. The increase percentage of flow stress (of nanoporous gold and nano-ligaments) induced by surface monolayer oxide is negligible when the ligament size (

L

) exceeds ∼2 µm

increases with decreasing

L

for ∼200 nm  

L

  ∼2 µm

and then saturates at ∼27% for

L 

 ∼200 nm. These results indicate a transition from

bulk-like

to

surface-mediated

deformation behavior of nano-ligaments as

L

decreases from ∼2 µm to ∼200 nm. Our observation at

L 

 ∼200 nm support the notion that the deformation is dominated by the surface-dislocation-nucleation at this scale.