We report on a unique delaminating morphology involved a transition from straight-sided to telephone cord buckles in SiAlNx films sputtered on 6-mm thick glass substrates. It is found that the straight-sided buckle tip propagates forward with an almost uniform speed. Usually, the straight-sided buckle is unstable, and it can evolve into the telephone cord buckle gradually accompanying with the enlargement of the buckle width. The structural characteristics and dynamical behaviors of the unique delaminating morphology have been investigated in detail. The physical mechanism of the transition behavior is analyzed based on the stability diagram of unilateral buckling patterns. (C) 2013 Elsevier B. V. All rights reserved.