Ab initiomolecular dynamics simulations of properties of a-Al2O3 /vacuum and a-ZrO2 /vacuum vs a-Al2O3∕Ge(100)(2×1) and a-ZrO2∕Ge(100)(2×1) interfaces

The local atomic structural properties of a-Al(2)O(3), a-ZrO(2) vacuum/oxide surfaces, and a-Al(2)O(3)Ge(100)(2x1), a-ZrO(2)Ge(100)(2x1) oxide/semiconductor interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic a-Al(2)O(3) and a-ZrO(2) bulk samples were generated using a hybrid classical-DFT MD approach. The interfaces were formed by annealing at 700 and 1100 K with subsequent cooling and relaxation. The a-Al(2)O(3) and a-ZrO(2) vacuum/oxide interfaces have strong oxygen enrichment. The a-Al(2)O(3)Ge interface demonstrates strong chemical selectivity with interface bonding exclusively through Al-O-Ge bonds. The a-ZrO(2)Ge interface has roughly equal number of Zr-O-Ge and O-Zr-Ge bonds. The a-Al(2)O(3)Ge junction creates a much more polar interface, greater deformation in Ge substrate and interface intermixing than a-ZrO(2)Ge consistent with experimental measurements. The differences in semiconductor deformation are consistent with the differences in the relative bulk moduli and angular distribution functions of the two oxides.