SKM 2023 – scientific programme

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O: Fachverband Oberflächenphysik

O 68: Poster: Oxide and Insulator Surfaces

O 68.4: Poster

Wednesday, March 29, 2023, 18:00–20:00, P2/EG

Atomic View on the (111) Surface of a Cu2O Single Crystal: Reconstruction, Electronic Properties and Band Bending Effects — Alexander Gloystein, Jack Creed, and •Niklas Nilius — Carl von Ossietzky University, Institute of Physics, D-26111 Oldenburg, Germany

The nature of the (sqrt3xsqrt3)R30° reconstruction of the Cu2O(111) surface has been heavily debated for almost 30 years. This work demonstrates that the nano-pyramidal reconstruction model that was recently developed for Cu2O(111) thin films is valid also for bulk samples. Well-prepared crystals develop a robust (sqrt3xsqrt3)R30° superstructure in electron diffraction, while atomically resolved STM images display extended arrays of trifold symmetric protrusions with 10.5 Å periodicity. Both findings are in perfect agreement with the nano-pyramidal model, in which Cu4O units attach to every third Cu-O six-ring of a Cu-depleted (111) surface. STM conductance spectra reveal the p-type character of the oxide with the valence-band top pinned to the Fermi level. From band-bending effects in the tip electric field, an induced carrier concentration of 6x10^17 cm-3 is determined for the (sqrt3xsqrt3)R30° phase, increasing to 4x10^18 cm-3 on the few (1x1) patches covered with a Cu-poor minority phase. This difference reflects the close interplay between atomic structure, electronic properties and local screening response for a given surface termination.