We report formation of self-organized nanodiamond ring structures due to dynamical heterogeneity in super undercooled carbon

created by nanosecond laser melting of amorphous carbon layers. We envisage that diamond tetrahedra self-organize and lead to formation of string and ring structures on which nanodiamonds nucleate and grow. Denser ring structures are formed in Q-carbon due to higher undercooling and enhanced diamond nucleation. The average size is larger under heterogeneous nucleation compared to homogeneous nucleation due to lower critical size and free energy

allowing more time for growth. With nanosecond laser melting

growth velocities range 5–10 ms

−1

and even higher for Q-carbon.