Oxide-Metal Interaction Probed by Scanning Tunneling Microscope Manipulation of Cr₂O₇ Clusters on Au(111)

Abstract

Interfacial interaction plays a crucial rule in catalysis over supported catalysts, and the catalyst−support interaction needs to be explored at microscopic scale. Here, we use the scanning tunneling microscope (STM) tip to manipulate Cr 2 O 7 dinuclear clusters on Au(111) and find that the Cr 2 O 7 −Au interaction can be weakened by an electric field in the STM junction, facilitating rotation and translation of the individual clusters at the imaging temperature (78 K). Surface alloying with Cu makes the manipulation of the Cr 2 O 7 clusters hard due to the enhanced Cr 2 O 7 −substrate interaction. Density functional theory calculations reveal that barrier for translation of a Cr 2 O 7 cluster on the surface can be increased by surface alloying, influencing the tip manipulation. Our study demonstrates that the oxide−metal interfacial interaction can be probed by STM tip manipulation of supported oxide clusters, which provides a new method to investigate the interfacial interaction.

Chromium Oxide Thin Films on Pt(111): An STM and DFT Excursion through the Phase Diagram

“…Subsequent experiments explored the growth of CrO x films on Cu(110) and Cu(100). Here, a low-coverage phase was linked to CrO, as only Cr 2+ ions were detected in X-ray photoelectron spectroscopy (XPS), while a high-coverage (√3 × √3) R 30° phase was ascribed to Cr 2 O 3 . , More recently, CrO x growth on Au(111) was investigated by STM, LEED, and XPS. , The detected films were ascribed to a CrO 2 bilayer composed of two Cr–O honeycomb planes linked by upright O bridges. Surprisingly, the configuration could be oxidized to an ordered array of Cr 2 O 7 magic clusters, while vacuum annealing reversed the phase change back to CrO 2 .…”

“…17,18 More recently, CrO x growth on Au(111) was investigated by STM, LEED, and XPS. 19,20 The detected films were ascribed to a CrO 2 bilayer composed of two Cr−O honeycomb planes linked by upright O bridges. Surprisingly, the configuration could be oxidized to an ordered array of Cr 2 O 7 magic clusters, while vacuum annealing reversed the phase change back to CrO 2 .…”