Surface Structure of V₂O₃(0001): A Combined I/V-LEED and STM Study

Abstract

Using I/V-LEED and scanning tunneling microscopy, we have investigated the surface structure of ∼100 Å thick V 2 O 3 (0001) films on Au(111). Both methods clearly show that the surface is terminated by a layer of vanadyl groups. I/V-LEED quantitative structure determination applied to differently prepared films always leads to a Pendry Rfactor for the VO termination close to 0.11 while the R-factor for a reconstructed O 3 termination is always larger than 0.2 and increases with increasing data set size. These results are at variance with a recent publication by Window et al. [Phys. Rev. Lett. 2015, 114, 216101] in which the authors propose that the V 2 O 3 (0001) surface is terminated by a reconstructed O 3 structure. Surface oxidation experiments also contradict the conclusions of Window et al. since oxidation leads to a previously identified structure with a (√3 × √3) R30°LEED pattern which is not expected for oxidation of an O3-terminated surface. In the course of the I/V-LEED calculations the individual Debye temperatures of the surface atoms were determined as part of the structural optimization procedure. We show that this approach is superior to the kinematical analysis of temperature-dependent LEED measurements.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique

“…The V ¼ O stretching mode has an energy of ∼1040 cm −1 as determined with HREELS and IRAS [25][26][27][28][29], with the energy varying somewhat between different samples. STM and IV-LEED have independently verified the presence of these groups at the surface [30,31].…”

“…Previously published STM data show that missing vanadyl groups are common defects on the V 2 O 3 ð0001Þ surface. Sometimes also not well-characterized protrusions are seen [31]. The mode at 1008 cm −1 may be related to vanadyl groups near to such defects and the mode at 759 cm −1 is probably also related to surface defects since bulk modes are not expected at this energy [33,34].…”

“…Gold has the highest midinfrared reflectivity among all metals, which has two advantages: due to the low IR absorption cross section (and the high thermal conductivity) the sample warming up during the experiments will be small and the IR absorption of the oxide layer will be high due to the increased IR intensity at the surface [32]. The V 2 O 3 ð0001Þ film was prepared on clean Au(111) following a previously reported recipe [27,28,31].…”

LEED I/V determination of the structure of a MoO3 monolayer on Au(111): Testing the performance of the CMA-ES evolutionary strategy algorithm, differential evolution, a genetic algorithm and tensor LEED based structural optimization

“…The I/V curve computations for the individuals of the population were performed in parallel on a multi-processor system which reduced the computation time (but not the overall computational effort) significantly. Genetic algorithms have been employed before for LEED structural optimization [17][18][19][20], like differential evolution [21], and CMA-ES [22,23] . The methods are derivative-free robust search methods, not very sensitive to discontinuities and noise.…”

Carbon Dioxide Adsorption on V2O3(0001)

“…This was questioned some years ago by studies which reported that the surface should be terminated by a quasi-hexagonal oxygen layer [18][19][20]. A later I/V-LEED (LEED = low energy electron diffraction; I/V-LEED = LEED intensity analysis) study could show that the initial picture of a vanadyl terminated surface is probably correct [21,22] and therefore we will use the term 'vanadyl terminated' throughout this text. The vanadyl terminated V 2 O 3 (0001) surface can be reduced by electron bombardment such that the oxygen atoms of the vanadyl Abstract The adsorption of carbon dioxide on epitaxially grown V 2 O 3 layers on Au(111) has been studied with thermal desorption and infrared absorption spectroscopy.…”