  We report the observation of carrier mediated decrease in the stiffness of
crystalline (c)-Si(100) under nanoindentation. The apparent elastic modulii of
heavily dopes (1E21 cm-3) p- and n-type c-Si are observed to be lower by 5.-7.5
percent that the estimated value for intrinsic (1E14 cm-3) c-Si. The deviation
observed with respect to elastic modulus remarkably matches with the estimated
value while considering the electronic elastic strain effect on carrier
concentration as an influence of negative pressure coefficient of band gap for
Si. The value is predominantly higher than the reported value of a decrease of
1-3 percent in stiffness as an effect of impurity in c-Si.
