The argon (Ar) ion bombardment is used in the deposition of a thick multilayer tetrahedral amorphous carbon (ta-C) films. The bonding structure and surface morphology of the ta-C films are modified when the films are bombarded by Ar ion with different energy. Visible Raman spectroscopy and X-ray photoelectron spectroscopy is used to study the modification respectively. The results show that surface layer is etched, the bonding structure of the films is totally modified, and some sp(3) bonds convert to sp(2) bonds in the surface layer of the films. The sp(2) cluster of the bulk increases with the increment of Ar ion energy. Hence, a soft top layer on the films is formed and the stress of the bulk is released. The RMS of roughness and etching pits on the surface of films were increased with the increment of the bombarding energy of Ar ion, which can increase the adhesion between layers. These are very important to deposit thick ta-C film. The surface morphology is tested by AFM. The RMS roughness of thick ta-C film is about 0.54 nm. Using visible Raman spectroscopy, the sp(3) fraction of as-deposited ta-C film with 1 mu m thickness is estimated to be about 70%. (C) 2012 Elsevier B.V. All rights reserved.