The outstanding mechanical, chemical and tribological properties of tetrahedral amorphous carbon (ta-C) films have attracted much attention. For a wide variety of applications, a great effort should be focused on the nanoscale structure control. In the present work, we have adopted a novel technique for nanoscale manipulation of ta-C films; incorporating nano Ni dots at the interface between the ta-C film and the substrate. For Ni dot pretreatment, the Ni thin film was deposited and annealed prior to the ta-C films deposition. TEM and Raman spectrum analysis shows that the nano Ni dots at the interface between the film and the substrate results in nanoscale graphitic phase embedded in hard ta-C matrix. Mechanical and electrical properties were strongly dependent on the changes of the Ni-induced second phase. The reduction of mechanical properties and electrical resistivity with increasing the size of Ni dots could be understood in view of the local increase of sp(2) bonds in hard ta-C matrix. (C) 2003 Elsevier B.V. All rights reserved.