Interpreting the Presence of an Additional Oxide Layer in Analysis of Metal Oxides–Metal Interfaces in Atom Probe Tomography

Abstract

Atom Probe Tomography (APT) analysis of specimens embedded with metal oxide/metal leads to nonintuitive observations of a very thin layer of oxide at the interface due to oxygen migration under the influence of electric field in metal oxides. Detailed analyses of the FeO/Fe and ZrO 2 /ZrO interfaces are presented, explaining observation of the interfacial oxide layer with APT. These findings are relevant to the observation made for APT analysis of devices such as resistive switching, solar cells, oxides grown on metal/ alloy during oxidation and corrosion wherein metal oxide is in interface with metallic layers. Because the APT technique is based on the application of an electric field on the oxide/ metal interface, oxygen ions are driven toward the metal electrode and leads to a reaction with the metal and the formation of the additional interfacial oxide layer. Atomistic simulation performed on the FeO/Fe layer subjected to electric field confirms finding of oxygen migration from the oxide layer toward the oxide/metal interface.

Atomic-Scale Insights into Morphological, Structural, and Compositional Evolution of CoOOH during Oxygen Evolution Reaction

“…The bowl-shaped anhydrous oxide layer, with a maximum thickness of ∼10 nm in the center and a minimum thickness of 3–4 nm at the shank (Figure f,g), is most likely the result of the evolving morphology and the associated evaporation sequence of multiple flat-layered APT specimens, which was reported as an evaporation artifact in previous work . Also, the existence or thickness of the anhydrous layer might be questionable since APT analysis of the metal oxide/metal interface leads to the formation of a mono- or bilayer of “artificial” oxide at the interface. , This is associated with evaporation artifacts induced by either oxygen migration or the combination of Co with oxygen species in the hydrous oxide layer during evaporation from low-electric-field hydrous oxide to the high electric field Co matrix. , To examine this, we plotted atom maps of all oxygen-containing molecular ions (Figure S6). Co 2 O is distributed only at the interface between the hydrous oxide and Co.…”

“…44 Also, the existence or thickness of the anhydrous layer might be questionable since APT analysis of the metal oxide/metal interface leads to the formation of a mono-or bilayer of "artificial" oxide at the interface. 44,45 This is associated with evaporation artifacts induced by either oxygen migration 46 or the combination of Co with oxygen species in the hydrous oxide layer during evaporation from low-electric-field hydrous oxide to the high electric field Co matrix. 44,45 To examine this, we plotted atom maps of all oxygen-containing molecular ions (Figure S6).…”

Atom Probe Tomography for Catalysis Applications: A Review

“…Due to a heterogeneous field of evaporation, the analysis of interfacial regions leads to trajectory aberrations, local magnifications and reconstruction artifacts [143]. Furthermore, it is quite common to observe a thin layer of oxide at the metal/metal-oxide interface due to field-induced oxygen migration: oxygen reacts with the metal and forms an additional interfacial oxide layer [144]. Correlative approaches are thus required to improve the compositional and spatial resolution of such samples [145].…”

Research progress on layered metal oxide electrocatalysts for an efficient oxygen evolution reaction

“…Layered metal oxides represent a distinctive category of solid materials characterized by pronounced anisotropy across their basal and edge planes, thereby conferring upon them unexpected chemical and physical attributes. 37,38 Moreover, LMOs present a capacity for undergoing low-temperature chemical transformations devoid of compromising the integrity of covalent bonds within the layers. 39 These metal oxides may assume a morphology comprising a few or single layers crafted through specific methodologies, or they may show as stacks of electrically neutral metal oxide layers.…”