Electronic structure, Schottky barrier, and optical spectra of the SiC/TiC {111} interface

Sergey Rashkeev, Walter R L Lambrecht, Benjamin Segall

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Abstract

A first-principles total energy and electronic structure study of 3C-SiC/TiC {111} interfaces was carried out using the full-potential linear-muffin-tin orbital method. Three distinct plausible structural models were identified and investigated including the relaxation of the most important structural degrees of freedom. All three models considered have a threefold symmetry axis and have a mutual boundary layer of carbon. They were found to be stable with respect to small rigid body translations parallel to the interface which would destroy the threefold symmetry. One of the models (B) is a twinned version of the other (A) while the third model (C) differs from A by a rigid body translation parallel to the interface. The A and C models contain a common carbon sublattice in both the zinc blende structure of the SiC and rocksalt structure of the TiC. While in model A the Ti's are on top of the Si atoms nearest to interface, they are in a hollow site between the Si atoms in both the B and C models. Model A is found to be metastable with a significantly higher energy than B and C. This is explained in terms of the occurrence of compressed Ti-Si nearest neighbor distances in the ideal structure. The expansion of the later disrupts the interfacial Ti-C bonding. Our calculations find very nearly equal energies for the relaxed B and C models. This indicates that the occurrence of twinned (untwinned) structures on flat (stepped) surfaces as has been observed by electron microscopy is probably not due to a thermodynamic preference but rather to kinetic factors such as step-flow growth. All three structures have interface states in the band gap of SiC which are localized within two lattice planes from the interface and which pin the Fermi level. The nonbonding character of these interface states leads to nearly equal Schottky barriers for all three models. The optical dielectric functions for our interface models were calculated and show signatures of these interface states which should be detectable in the infrared range because of their strong anisotropy with respect to the interface plane.

Original languageEnglish
Pages (from-to)16472-16486
Number of pages15
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume55
Issue number24
Publication statusPublished - 15 Jun 1997
Externally publishedYes

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ASJC Scopus subject areas

  • Condensed Matter Physics

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