Details

Autor(en) / Beteiligte

• Setvin Martin
• Reticcioli Michele
• Poelzleitner Flora
• Hulva, Jan
• Schmid, Michael
• Boatner, Lynn A
• Franchini Cesare
• Diebold Ulrike

Titel

Polarity compensation mechanisms on the perovskite surface KTaO3(001)

Ist Teil von

• Science (American Association for the Advancement of Science), 2018-02, Vol.359 (6375), p.572-575

Ort / Verlag

Washington: The American Association for the Advancement of Science

Erscheinungsjahr

2018

Quelle

American Association for the Advancement of Science

Beschreibungen/Notizen

• Compensating a polar surfaceAn ionic crystal surface can be electrostatically unstable, and the surface must reconstruct in some way to avoid this “polar catastrophe.” Setvin et al. used scanning probe microscopies and density functional theory to study the changes in the polar surface of the perovskite KTaO3. They observed several structural reconstructions as the surface cleaved in vacuum was heated to higher temperatures. These ranged from surface distortions to the formation of oxygen vacancies to the development of KO and TaO2 stripes. Hydroxylation after exposure to water vapor also stabilized the surface.Science, this issue p. 572The stacking of alternating charged planes in ionic crystals creates a diverging electrostatic energy—a “polar catastrophe”—that must be compensated at the surface. We used scanning probe microscopies and density functional theory to study compensation mechanisms at the perovskite potassium tantalate(KTaO3) (001) surface as increasing degrees of freedom were enabled. The as-cleaved surface in vacuum is frozen in place but immediately responds with an insulator-to-metal transition and possibly ferroelectric lattice distortions. Annealing in vacuum allows the formation of isolated oxygen vacancies, followed by a complete rearrangement of the top layers into an ordered pattern of KO and TaO2 stripes. The optimal solution is found after exposure to water vapor through the formation of a hydroxylated overlayer with ideal geometry and charge.