Submonolayer coverages of V-oxide on Rh(111) condense during catalytic methanol oxidation into a pattern of macroscopic stripes or islands. Under reaction conditions, a phase separation occurs within the VO x islands that has been studied in a pressure range of 10–6–10–4 mbar with photoemission electron microscopy (PEEM), low-energy electron microscopy (LEEM), microspot-low-energy electron diffraction (μLEED), and microspot-X-ray photoelectron spectroscopy (μXPS). An oxidized outer ring with a (√7 × √7)­R19.1° structure coexists with an inner (12 × 12) Moiré-type boundary layer and a reduced core exhibiting a (√3 × √3)­R30° Moiré type pattern. The dependence of the substructure on the reaction conditions, on V coverage, and on island size was investigated. With μXPS, the V coverages of the different phases in the VO x islands were determined.

Organic electrochemical transistors (OECTs) can be distinguished from conventional organic thin film transistors (OTFTs) by the use of an electrolyte in their gate stack. This results in a unique set of device properties, most notably, mixed ionic and electronic transport. Modeling of these devices has mainly been realized using MOSFET-like equations (often called the ‘Bernards model’) and extensions, which use a circuit diagram to include the different parasitics and capacitances involved [1]. While these models provide qualitative agreements with OECT devices, their quantitative agreement may not be sufficient for realizing circuit simulations. Physically, the discrepancy between the model and the devices are likely to stem from the assumption that the electrolyte behaves as a parallel plate capacitor, as in a conventional MOSFET. Recently, another model based on thermodynamics has been proposed that treats the OECT as a thermodynamic binary system with entropic mixing as the driving force for device operation [2]. Here we explore these different models and then show how they can be used to understand circuit behavior of OECTs. The authors thank the ANR and the Bundesministerium für Bildung und Forschung (BMBF) for funding of the BAYOEN project under contract ANR-21-FAI1-0006-01 and 01IS21089. [1] J Rivnay et al Organic electrochemical transistors. Nature Reviews Materials, 3(2):1–14, 2018 [2] M. Cucchi et al ‘Thermodynamics of Organic Electrochemical Transistors’, accessed on researchsquare.com, https://doi.org/10.21203/rs.3.rs-1143463/v1 Figure 1