In polarizable materials, electronic charge carriers interact with the surrounding ions, leading to quasiparticle behavior. The resulting polarons play a central role in many materials properties including electrical transport, interaction with light, surface reactivity, and magnetoresistance, and polarons are typically investigated indirectly through these macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM) is used to directly image polarons in Fe ₂ O ₃ at the single quasiparticle limit. A combination of Kelvin probe force microscopy (KPFM) and kinetic Monte Carlo (KMC) simulations shows that the mobility of electron polarons can be markedly increased by Ti doping. Density functional theory (DFT) calculations indicate that a transition from polaronic to metastable free-carrier states can play a key role in migration of electron polarons. In contrast, hole polarons are significantly less mobile, and their hopping is hampered further by trapping centers.

Electroreduction experiments on metal oxides are well established for investigating the nature of the material change in memresistive devices, whose basic working principle is an electrically-induced reduction. While numerous research studies on this topic have been conducted, the influence of extended defects such as dislocations has not been addressed in detail hitherto. Here, we show by employing thermal microscopy to detect local Joule heating effects in the first stage of electroreduction of SrTiO₃ that the current is channelled along extended defects such as dislocations which were introduced mechanically by scratching or sawing. After prolonged degradation, the matrix of the crystal is also electroreduced and the influence of the initially present dislocations diminished. At this stage, a hotspot at the anode develops due to stoichiometry polarisation leading not only to the gliding of existing dislocations, but also to the evolution of new dislocations. Such a formation is caused by electrical and thermal stress showing dislocations may play a significant role in resistive switching effects.

Controlling the work function of transition metal oxides is of key importance with regard to future energy production and storage. As the majority of applications involve the use of heterostructures, the most suitable characterization technique is Kelvin probe force microscopy (KPFM), which provides excellent energetic and lateral resolution. In this paper, we demonstrate precise characterization of the work function using the example of artificially formed crystalline titanium monoxide (TiO) nanowires on strontium titanate (SrTiO₃) surfaces, providing a sharp atomic interface. The measured value of 3.31(21) eV is the first experimental work function evidence for a cubic TiO phase, where significant variations among the different crystallographic facets were also observed. Despite the remarkable height of the TiO nanowires, KPFM was implemented to achieve a high lateral resolution of 15 nm, which is close to the topographical limit. In this study, we also show the unique possibility of obtaining work function and conductivity maps on the same area by combining noncontact and contact modes of atomic force microscopy (AFM). As most of the real applications require ambient operating conditions, we have additionally checked the impact of air venting on the work function of the TiO/SrTiO₃(100) heterostructure, proving that surface reoxidation occurs and results in a work function increase of 0.9 eV and 0.6 eV for SrTiO₃ and TiO, respectively. Additionally, the influence of adsorbed surface species was estimated to contribute 0.4 eV and 0.2 eV to the work function of both structures. The presented method employing KPFM and local conductivity AFM for the characterization of the work function of transition metal oxides may help in understanding the impact of reduction and oxidation on electronic properties, which is of high importance in the development of effective sensing and catalytic devices.

Local-conductivity atomic force microscopy with atomic resolution reveals that the surface conductivity of slightly reduced transition metal oxides such as TiO₂ and SrTiO₃ is confined to conductance paths on the nanoscale.

Hematite is a common iron oxide found in nature, and the α‐Fe₂O₃(0001) plane is prevalent on the nanomaterial utilized in photo‐ and electrocatalytic applications. The atomic‐scale structure of the surface remains controversial despite decades of study, partly because it depends on sample history as well as the preparation conditions. Here, a comprehensive study is performed using an arsenal of surface techniques (non‐contact atomic force microscopy, scanning tunneling microscopy, low‐energy electron diffraction, and X‐ray photoemission spectroscopy) complemented by analyses of the near surface region by high‐resolution transmission electron microscopy and electron energy loss spectroscopy. The results show that the so‐called “bi‐phase” termination forms even under highly oxidizing conditions; a (1 × 1) surface is only observed in the presence of impurities. Furthermore, it is shown that the biphase is actually a continuous layer distorted due to a mismatch with the subsurface layers, and thus not the proposed mixture of FeO(111) and α‐Fe₂O₃(0001) phases. Overall, the results show how combining surface and cross‐sectional imaging provides a full view that can be essential for understanding the role of the near‐surface region on oxide surface properties.