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

Abstract

A first-principles total energy and electronic structure study of 3C-SiC/TiC ͕111͖ 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 latter 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 ͑untwinned͒ structures on flat ͑stepped͒ 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.

Defect states at organic–inorganic interfaces: Insight from first principles calculations for pentaerythritol tetranitrate on MgO surface

“…The second method, which we used here, is more straightforward and is based on the analysis of the site projected partial density of states. This approach was applied for the determination of the Schottky barriers at metal-semiconductor heterojunctions [87] and it closely resembles a procedure often used in experiments. The scheme utilizes the simple fact that in the ""bulk regions"" of the structure, the separation of relevant ""valence"" energies (e.g., the Fermi energy of the metal and the valence-band maximum of the semiconductor) from core levels are the same as in the bulk.…”

“…The scheme utilizes the simple fact that in the ""bulk regions"" of the structure, the separation of relevant ""valence"" energies (e.g., the Fermi energy of the metal and the valence-band maximum of the semiconductor) from core levels are the same as in the bulk. Thus, by using that energy difference along with the position of the core level in the structure E c (n) (where n is the layer number), which essentially follows that of the average electrostatic potential in the structure, one obtains the position of the valence band energy relative to a common reference energy in the entire structure [87].…”

Ohmic contacts on silicon carbide: The first monolayer and its electronic effect

“…84,85 The p-type SBH is calculated from the difference between the Fermi level ͑E F ͒ of interface supercell and the valenceband top of bulk SiC region, 86,87 which can be obtained by supercell calculations based on the DFT. It should be noted FIG.…”

Investigation on nanotube-metal contacts under different contact types

“…In the calculation, the work functions of CNT, Ti and TiC are taken as 4.5 eV [15], 3.9 eV [16] and 4.6 eV [17,18], respectively. A suitable gate voltage was applied to make the contact be in the On state when calculating the I-V characteristics and contact resistance.…”