The bonding configuration and structural evolution of Si and Ge incorporated amorphous carbon (a-C:Si-x and a-C:Ge-x) films were studied. The incorporation of Si and Ge to amorphous carbon (a-C) has the advantageous effect of promoting sp(3) hybridized bond formation due to smaller energy difference between s and p orbital in Si and Ge than C. The C 1s NEXAFS spectra of Si or Ge incorporated a-C films, the formation of Si (or Ge)-C bond is observed, i.e., the fort-nation of a-SiC or a-GeC networks by the incorporation of Si (or Ge) in sp(2) hybridized site and bonding with carbon atoms to generate sp(3) hybridization. The important role of the incorporated Si and Ge in modifying the bonding configuration of a-C is revealed by using UV Raman spectroscopy to open up the ring structure of sp(2) hybridized bonded C atoms and formation of sp(3) hybridized bond with high efficiency. (c) 2005 Elsevier B.V. All rights reserved.