Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 37: Metal Oxide Surfaces II: Structure, Epitaxy and Growth

O 37.6: Vortrag

Dienstag, 2. April 2019, 15:15–15:30, H16

Ab-initio studies of the (110) surface terminations of rutile VO2 — •Jakub Planer, Florian Mittendorfer, and Josef Redinger — Vienna University of Technology, 1040 Vienna, Austria

Vanadium dioxide is a promising candidate for fast electronic or optical switching. These applications are based on a metal-insulator transition at 340 K, where the structure changes from a monoclinic to a rutile phase. Yet this transition is sensitive to the presence of strain or defects, such as oxygen vacancies. We present results for the bulk and surface properties of the VO2 phases under varying oxygen partial pressure, and compare our results to recent experimental findings. The calculations were performed with the Vienna Ab initio Simulation Package (VASP). We find that standard GGA functionals (PBE) offer an appropriate description of the structural properties of the rutile phase and monoclinic phase, but more advanced functionals such as meta-GGA approaches (SCAN) have to be employed to capture surface energies well. The stability of various surface terminations for the rutile (110) surfaces will be discussed in relation to experimental findings. For PBE we find a slightly oxidized tetrahedral termination under UHV conditions (µ = -1.88 eV). Using PBE+U (U = 2 eV) a buckled (110) termination is obtained from simulated annealing calculations. At last, we will present the results of an enlarged search for relevant surface terminations applying a state-of-the-art meta-GGA SCAN(+U) functional together with a first-principles genetic algorithm as implemented in the USPEX package.