Nanostructuring of tetrahedral carbon films by carbon ion implantation

Abstract

The formation of nanostructures in the matrix of tetrahedral amorphous carbon (ta-C) films induced by ion beam implantation at high doses has been studied by high-resolution transmission electron microscopy, transmission electron diffraction and Raman spectroscopy. The ta-C films were deposited by a filtered cathodic vacuum arc and subsequently implanted by carbon ion beams extracted from a metal vapor vacuum arc ion source. The carbon ions were implanted to doses ranging from 3×10 13 to 3×10 17 ions/cm 2. In accord with the thickness of ta-C films and ion ranges (39–75 nm) required the ion energy was determined to be within a range of 25–50 keV. The analysis of Raman spectra indicates that originally abundant sp 3 carbon atomic bonding of ta-C is gradually converted to a graphitic phase during the course of ion bombardment. The local order, growth and clustering the sp 2 bonded carbon atoms in the ta-C films by ion implantation is also indicated by Raman spectroscopy. However, the analysis of implanted amorphous carbon films on an atomic scale shows the formation of structure with the higher degree of order. The graphitic basal planes are formed preferably along the ion tracks. The results are discussed in the context of previously reported studies of implanted ta-C films and glassy carbon. This article shows a critical damage level of 0.24 displacements per atom when the onset of the transformation occurs and demonstrates that the initially amorphous phase with short ordered sp 3 bonding configuration can be nanostructured to the higher degree of an ordered structure using proper ion energies and doses.