Structural, electronic, and energetic properties of SiC [111] Zr B2 [0001] heterojunctions: A first-principles density functional theory study

First-principles density functional theory was used to determine the structural properties and thermodynamic stability of strained heterojunctions between cubic SiC and hexagonal Zr B2 films grown on Si(100) platforms. The SiC films were generated experimentally via single source depositions of the Si H3 CC Si H3 compound on Zr B2 Si (100) hybrid substrates. In this study, a fixed stoichiometry (Si6 C6 Zr6 B12) supercell was used to calculate the equilibrium atomic and electronic structure of six plausible bonding arrangements at the SiC Zr B2 interface, involving tetrahedrally coordinated C or Si centers bonded with either Zr or B atoms. The relative stability of the resultant structures is examined as a function of the Si and Zr chemical potentials. We find that the lowest energy configuration comprises of Si centers bonded to one C and three Zr atoms and exhibits the smallest bond strains with "bulklike" interatomic distances. This lowest energy structure is also consistent with cross-section transmission electron microscopy measurements of the near-interface region of SiC(111) films grown on Zr B2 (0001) buffered Si(111). A detailed analysis of the electronic structure indicates that delocalized "sheetlike" metallic bonding stabilizes this structure between covalent SiC and semimetallic Zr B2. Assuming no intermixing at the interface, this lowest energy model suggests that the SiC overlayers grown on ZrB2 are C terminated. However, calculations on isolated SiC slabs predict that Si termination is preferred, in accord with experimental observations for SiC grown on various substrates.