Synthesis and characterization of Ti-Si-C-N films

Abstract

This study represents one of the first attempts to deposit multicomponent (more than three components) thin films by magnetron sputtering of multiphase composite targets (three phases or even more). Films of Ti-Si-C-N were synthesized through dc magnetron sputtering of xTiC+yTi3SiC2+zA composite targets (A was TiSi2, SiC, or a mixture of these phases) in an argon atmosphere or in a gaseous mixture of argon and nitrogen. The as-deposited films were characterized using Auger electron spectroscopy, X-ray diffraction, transmission electron microscopy using selected area electron diffraction and high-resolution techniques, and microhardness. It was shown that the substrate temperature and the nitrogen concentration in the reactive gas had a strong influence on the structure and the composition of the as-deposited films. The films deposited from the Si-poor targets were either polycrystalline or contained a mixture of nanocrystalline and amorphous phases. An amorphous phase formed as individual grains rather than as intergrain amorphous layers. All films deposited from the Si-rich target were amorphous in nature. Particular attention has been paid to the atomic structure of grains and grain boundaries in the crystalline films. Polycrystalline grains contained a high density of dislocations and exhibited a curved appearance of the lattice fringes that is probably due to the presence of the long-range stress fields. The measurements of the lattice parameters using the selected area electron diffraction pattern (SA EDP) method indicated, with a high probability, that the polycrystalline grains consist of clusters of atoms with varying compositions. The grain boundaries in the nanocrystalline Ti-Si-C-N films had both ordered and disordered regions, although some regions close to the interface exhibited neither a fully crystalline nor a homogeneously amorphous structure. The atomic structure of an interface was shown to depend on the orientation relationship between adjacent grains. The atomic planes were perfectly matched when the two grains were oriented close to the [110]fcc1//[110]fcc2 zone axis. However, the interface dislocations were frequently observed at or near the grain boundary when [110]fcc1//[001]fcc2. The contribution of compressive stress as determined by an increase in the fcc lattice parameter is also discussed.