1. The inverse H-P effect could be explained by the strain contributions
from GBs and grain interior. The larger grain size results
in large portion of strain in grain interior, producing higher hardness
under ultra shallow indentation. The H-P relation does not
hold even the crystal size is above the conventional transition
size. Our observation indicates the GB absorption and GB sliding
comes to play an important role in the ultra shallow contact, few
generated dislocations can be easily absorbed by GBs.