Local Structure and Properties of Oxide Surfaces: Scanning Probe Analyses of Ceramics

Abstract

Scanning probe microscopies, especially scanning tunneling microscopy, were first directed to metal and semiconductor surfaces. Early challenges associated with the low conductivity and ionicity of oxides slowed application to even semiconducting ceramics. Recently, some of these obstacles have been overcome, and probe microscopies have been used to determine the atomic structures, as well as local properties, of many oxide surfaces and interfaces. Approaches to quantifying both tunneling spectroscopy and tunneling images of oxides are presented. Oxide surfaces accommodate nonstoichiometry via reconstruction or surface stabilization of substoichiometric phases. Effects of self-segregation and of impurity segregation on local properties of surfaces are observed directly. Three examples of local properties at interfaces are presented: contact potential at nanoscale metal cluster-oxide interfaces, local electrostatic fields at grain boundaries, and current flow in complex superconducting microstructures.

Controlling oxide surface dipole and reactivity with intrinsic nonstoichiometric epitaxial reconstructions

“…We expect that surface effects are especially important for oxides since their surface compositions and structures can be significantly changed depending on the environmental conditions to which they are exposed or in which they are prepared 12,[20][21][22][23][24][25][26] . In particular, the surface atomic geometry can be very different from that of the bulk-like surface due to reconstruction, even though the crystallographic orientation of the surface is unchanged.…”

Local Optical Properties, Electron Densities, and London Dispersion Energies of Atomically Structured Grain Boundaries

“…The 5 grain boundary [ Fig. 1(a)] consists of structural units with a short periodicity along the interface plane [7][8][9][10][11]. The n13 GB [ Fig.…”

Oxygen vacancy formation in the SrTiO3 Σ5 [001] twist grain boundary from first‐principles

“…22 Meyer & DeSouza also noted that a negative GB core charge cannot be reconciled with the fact that tilt GBs act as barriers for oxygen diffusion. 23,24 Indeed, while SrTiO 3 tilt GBs have been extensively studied from both the theoretical [25][26][27][28][29] and experimental realms, [30][31][32][33][34] key controversies regarding the segregation of defects and the implications for space charge remain. [11][12][13][14][35][36][37] The properties of twist grain boundaries are even less understood.…”

“…Indeed, while SrTiO 3 tilt GBs have been extensively studied from both the theoretical and experimental realms, key controversies regarding the segregation of defects and the implications for space charge remain . The properties of twist grain boundaries are even less understood.…”