Growth and structure of aluminum films on (001) silicon carbide

Abstract

The formation and the physical and electronic structure of the interface between Al and SiC films, grown epitaxially on Si(001), are studied using x-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and energy-loss spectra (ELS). Zr M-zeta excitation (hν=151.4 eV) is employed to obtain high surface sensitivity in the Si and Al 2p and valence-band photoemission. The first few monolayers of Al grow as layers, with Al island formation at higher coverage. Al-Si interaction is apparent as a shift of the Al 2p (Si 2p) to higher (lower) binding energy (BE) for θ≤1. A Schottky barrier height of ≊1.4 eV is estimated. At higher θ the Al 2p assumes the BE and shape characteristic of bulk Al, and the Si 2p shows satellite structure to lower BE suggesting both Si bonded to Al and C as well as Si interacting mainly with Al. Annealing (350≤T≤1050 °C) leads to a reduction in Al coverage and reversal of the trends observed during sequential deposition. Before annealing LEED shows only a weak (1×1) pattern. Annealing at successively higher temperatures leads to a sharper (1×1), followed by two-domain (4×1) and two-domain c(8×2) patterns. No clear indication of Al carbide formation is found in Auger electron spectra or in the Al 2p XPS unless the SiC, prior to Al deposition, is first treated at high temperature to generate a C-rich surface.