  The interplay between the formation of neutron skin and alpha cluster at the
dilute surface of neutron-rich nuclei is one of the interesting subjects in the
study of neutron-rich nuclei and nuclear clustering. A theoretical model has
predicted that the growth of neutron skin will prevent the alpha clustering at
the nuclear surface. Quite recently, this theoretical perspective; the
suppression of alpha clustering by the neutron-skin formation was first
confirmed experimentally in Sn isotopes as the reduction of the (p, p alpha)
reaction cross-section. Motivated by the novel discovery, in this work, we have
investigated the relationship between the neutron-skin thickness and alpha
clustering in C isotopes. Based on the analysis by the antisymmetrized
molecular dynamics, we show that the alpha spectroscopic factor at nuclear
exterior decreases in neutron-rich C isotopes, and the clustering suppression
looks correlated with the growth of the neutron-skin thickness.
