TAN-Cu nanocomposite films, were deposited by reactive co-sputtering on Si and tool steel substrates. The films were then annealed using RTA (Rapid Thermal Annealing) at 400 degrees C for 2, 4, 8 min respectively to induce the nucleation and growth of Cu particles in the TaN matrix and on the film surface. SSPM (Scanning Surface Potential Microscopy) and SEM (Scanning Electron Microscopy) were applied to examine the Cu nano-particles that emerged on the surface of TaN-Cu thin films. Pin-on-Disk tribometer was used to study the effect of annealing on the films' tribological properties. The results reveal that annealing by RTA can cause Cu nano-particles to emerge on the TaN surface. Consequently, hardness and friction coefficients will change depending on annealing conditions, Cu content, and/or Cu particle emergence. (c) 2007 Elsevier B.V. All rights reserved.