Surface Structure of ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$ Revisited

In a recent paper [A. J. Window et al., Phys. Rev. Lett. 107, 016105 (2011)], it was proposed that ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$ is terminated by the so-called ${\mathrm{O}}_3$ termination, a reconstruction with a terminating distorted hexagonal oxygen layer. We show that the surface is terminated by vanadyl ($\mathrm{V}═\mathrm{O}$) groups instead. This conclusion is based on quantitative low-energy electron diffraction combined with scanning tunneling microscopy, fast atom scattering, and density functional theory employing the Heyd-Scuseria-Ernzerhof functional. New insights into the subsurface sensitivity of ion beam triangulation show that results previously interpreted in favor of the ${\mathrm{O}}_3$ termination are reconcilable with vanadyl termination as well.

Figure 1

Structural model (V gray and O red) of surface terminations predicted by DFT.

Figure 2

Experimentally observed surface phases as a function of the preparation conditions.

Figure 3

Calculated $I\text{−}V$ LEED curves (green and red) and experimental data (black) for the eight symmetry inequivalent beams.

Figure 4

Atomically resolved STM images of the ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$ surface. (a) Slightly reduced layer; (b) slightly overoxidized layer. $10\times 10{\mathrm{nm}}^2$, 2 V, and 0.1 nA.

Figure 5

Intensity of specularly reflected 2 keV He atoms (black curve) from Au(111) and a ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$ thin film as a function of the azimuthal angle as well as simulations for the vanadyl (blue curve) and ${\mathrm{O}}_3$ termination (red curve) of ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$.

Figure 6

Surface energy $\gamma$ as a function of the chemical potential $\mathrm{\Delta }{\mu }_{\mathrm{O}}$ for different terminations of the ${\mathrm{V}}_2{\mathrm{O}}_3(0001)$ surface. At the bottom, the chemical potential scale is transformed into ${\mathrm{O}}_2$ pressure scales (mbar) for different temperatures. The stability ranges of the bulk phases are indicated by the horizontal black arrows.