AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS1+MC-WeA

Paper SS1+MC-WeA8
First-Principles Calculations on Al@sub 2@O@sub 3@/TiC Growth and Interface

Wednesday, October 4, 2000, 4:20 pm, Room 208

Session: Oxide Surfaces, Interfaces and Defects
Presenter: C. Ruberto, Chalmers University of Technology and Göteborg University, Sweden
Authors: C. Ruberto, Chalmers University of Technology and Göteborg University, Sweden
B.I. Lundqvist, Chalmers University of Technology and Göteborg University, Sweden
Correspondent: Click to Email
First-principles calculations based on density-functional theory are performed to understand the first steps in the growth of alumina on TiC(111). The alumina/TiC interface is theoretically very interesting, being an example of interface between an oxide, ionic and insulating, ceramic and a covalent transition-metal ceramic with metallic and ionic character. The TiC(111) facet is furthermore a highly active and polar surface. Technologically, the interface is of high importance in wear-resistant cutting tools used in industrial high-speed applications. Different phases of alumina (mainly the @alpha@ and @kappa@ phases) are used as chemically-inactive coatings on cemented-carbide tools. These coatings are grown on TiC(111), TiN(111), or Ti(C,N)(111) through chemical-vapor deposition (CVD). It is known that the coating quality and phase content are determined by the nucleation on the substrate surface. For example, a region of @gamma@ alumina is sometimes observed between TiC and @kappa@ alumina. This work is the first step towards establishing a fundamental understanding of the interfacial structure and of the growth of alumina on TiC(111). This is done in several steps. We investigate the adsorption energies of the different atomic species present in the CVD reactor on the TiC(111) surface. The energetics for the different atomic configurations of an aluminum layer at 2/3 coverage on TiC(111)-O are studied and the observed structural stability is understood on the basis of bonding character. The influence of thermal lattice expansion is discussed. The stability and bonding character of a layer of stoichiometric Al@sub 2@O@sub 3@ in different structural configurations on TiC(111)-O are then examined. Finally, the structure and stability of all different atomic terminations of the @kappa@-Al@sub 2@O@sub 3@(001) and (00-1) surfaces, the preferred CVD growth direction, are presented and discussed.