Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO 3 : The Effect of Surface Orientation

• Published in: Advanced materials interfaces Vol. 10; no. 2
• Main Authors: Kler, Joe, Börgers, Jacqueline M., De Souza, Roger A.
• Format: Journal Article
• Language: English
• Published: 01.01.2023
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.202201434

Abstract 18 O 2 / 16 O 2 exchange experiments on terminated (100), (110), and (111) oriented samples of single‐crystal SrTiO 3 are used to study the effect of surface orientation on the oxygen surface exchange coefficient and the surface space‐charge potential Φ 0 . Isotope exchanges are carried out at temperatures 922 < T /K < 1073 at an oxygen activity a O 2  = 0.2 in dry conditions ( a H 2 O < 10 −7.7 ); isotope profiles are measured subsequently by secondary ion mass spectrometry. Isothermal values are found to vary by less than one order of magnitude, with . All data are consistent with a change in the activation enthalpy of surface exchange from 3.0 eV at high temperatures to 1.8 eV at lower temperatures. The transition is attributed to a change from a charge‐transfer mechanism at high temperatures to a mechanism involving surface OH species. The transition temperature depends on the surface orientation, T tr (111) ≈ T tr (110) > T tr (100). Values of Φ 0 obtained varied between 0.50 V and 0.37 V, with isothermal values obeying Φ 0 (111) ≈ Φ 0 (110) < Φ 0 (100). Φ 0 data is analysed to obtain the OH − surface coverage for the low‐temperature regime. Similarities between the behavior of Φ 0 and that of are highlighted.