Thin films of TM-X-N (TM stands for early transition metal and X=Si, Al, etc.) are used as protective coatings. The most investigated among the tertiary composite systems is Ti-Si-N. The system Ti-Ge-N has been chosen to extend the knowledge about the formation of nanocomposite films. Ti-Ge-N thin films were deposited by reactive magnetron sputtering on Si and WC-CO Substrates at T-s=240 degrees C, from confocal Ti and Ge targets in mixed Ar/N-2 atmosphere. The nitrogen partial pressure and the power on the Ti target were kept constant, while the power on the Ge target was varied in order to obtain various Ge concentrations in the films. No presence of Ge-N bonds was detected, while Xray photoelectron spectroscopy measurements revealed the presence of Ti-Ge bonds. Transmission Electron Microscopy investigations have shown important changes induced by Ge addition in the morphology and structure of Ti-Ge-N films. Electron Energy-Loss Spectrometry study revealed a significant increase of Ge content at the grain boundaries. The segregation of Ge atoms to the TiN crystallite surface appears to be responsible for limitation of crystal growth and formation of a TiGe,. amorphous phase. (c) 2005 Elsevier B.V. All rights reserved.