We report room temperature delamination of chemically vapor deposited diamond films on a Si substrate due to 1.5 MeVHe+ion bombardment. The delamination of films has been studied by scanning electron microscopy. The threshold fluence at which the delamination takes place has been determinedin situby monitoring the hydrogen signal with the help of elastic recoil detection analysis. Micro Raman measurements show the presence of residual stress (1.19 GPa) in the as-prepared films and its relaxation at the peripheri of the delaminated regions. It is proposed that enhancement of the residual stress duringHe+ion bombardment leads to stress saturation conditions which result in the delamination of the brittle diamond films from the film/substrate interface. These findings lead to the possibility of creating ion-beam induced channels in diamond films for device isolation by suitable choice of film/substrate combination. ©1998 American Institute of Physics.