ИСТИНА

Typical structural defects are studied theoretically in the course of O Al  O atomic depositions on the basic Si(110) surface. The defects are determined by analyses of the band gap states and projected densities of the s- and p-states after the deposition aimed to form a Si(110)/SiOX/AlOY/-Al2O3 slab. The extent of Si(110) passivation after each deposition step is studied by scanning the band structure calculated using Density Functional Theory with periodic boundary conditions. Our modeling reproduces most features of the use of any organic ligand as Al precursor along O2 plasma assisted atomic layer deposition (PA ALD) when the organic ligands are completely oxidized so that their participation can be neglected in the deposition as already shown experimentally. The passivated oxide Al2O3/Si layer is relatively thin, but nevertheless exceeds 10 Å, so that any computational hints to accelerate the growing of the interface instead of the numerous steps of successive O/Al/O/Al/… depositions could be useful. It is why we have used the merging procedure with Al16O30 (joined via two opposite sides which differ by the locations and numbers of O atoms) or Al16O24 fragments which led to a passivation in most of the cases. More precisely, the final oxidation step after O/Al/O/Al/… depositions corresponds to the junction of a slab of -Al2O3 fragment deposited over Si(110), whose super cell (SC) parameters have been selected to lead to the minimum mismatch. Different examples of either non-satisfactory or accurate junction of the oxidized Si(110) slab and -Al2O3 fragment are discussed aiming to develop a route for understanding the dominant defect types at the interface. A list of formed typical defects at the Si(110)/SiOX/AlOY/-Al2O3 boundary is presented and characterized by the projected density of states and respective band structure around the band gap. We distinguished two types of possible drawbacks produced by joining the Si support and the oxide fragment. First, at small number of Al atoms (NAl = 4) per SC deposited on the oxidized Si slab, the oxide can attach the essential part of Al atoms thus redistributing them in favor of the oxide. The second negative effect of the proposed junction is related to the transformation of the OAl2 and OAl3 groups of the Al2O3 oxide layer. The defective states of the OAl2 groups could be previewed regarding three- or four-coordinated O atoms in the Al2O3 bulk, but the reasons of such transformation of OAl3 groups are less understood and could be assigned tentatively to a geometry distortion. The majority of the slab cases prepared by the junction possess by reasonable gap width that shows on the possibility of such approach in the modeling.