Electronic structure of α-Al2O3 in the bulk and on the surface

Abstract

Using a full-potential method of attaching plane waves, the electronic structure of Al 2 O 3 is calculated in a corundum structure in the bulk and on the surface (0001). It is shown that the calculations consistently reproduce the properties with respect to the experiment. The effect of surface relaxation on the structure of subsurface states is discussed.

The nature of electron states in AlN and α-Al2O3

“…The O 2p electrons have a band width of about 7.1 eV, larger than that (6.4 eV) of N 2p, as shown in table 1. Those results agree well with the former theoretical calculations for α-Al 2 O 3 [8,[11][12][13] and for AlN [32][33][34]. Before discussing band gaps it is important to realize that calculations based on the density-functional theory (DFT) underestimate band gaps typically by 30% for the systems considered here [35].…”

“…Experiments show that α-Al 2 O 3 is a wide-gap insulator with a direct energy gap of about 8.3 eV at [8,9], larger than that of AlN (6.3 eV) [10]. Many theoretical calculations have been performed for α-Al 2 O 3 [8,[11][12][13][14][15][16]. The O-Al bonds in the compound exhibit highly ionic nature [13,17].…”

“…The valence band (VB) is well separated into two parts, with the lower part consisting of O 2s states and the upper part being dominated by O 2p states. The lower part of the conduction band (CB) is in general believed to be dominated by Al 3s states [8,[11][12][13][14][15][16][17].…”

Theoretical investigations of 3d-metal adsorption on the α-AL2O3 (0001) surface

“…1. By analogy with [24], to describe the (0001) surface, an 18-layer film with two surfaces consisting of 12 aluminum and 6 oxygen layers was used. In computations, seven atomic layers on each surface side were optimized, and the atoms of other layers were fixed with interlayer distances typical of the bulk material.…”

Adhesion at the interfaces between BCC metals and α-Al2O3

“…We note that the details of the calculation of the sur face electronic structure of aluminum oxide and anal ysis of its measurements compared to the bulk material were presented in [30]. Although the approximation used for the exchange-correlation functional, as well as the LDA, does not underestimate the width of the band gap of aluminum oxide, our calculations, as well as previous investigations, make it possible to hope that this circumstance only slightly affects the physical picture of phenomena studied in this work.…”