Tuning the magnetic properties of cobalt tetraphenylporphyrin films with oxygen exposure
Tuning the magnetic properties of cobalt tetraphenylporphyrin films with oxygen exposure lead image
The development of organic or hybrid organic/inorganic devices requires an understanding of the operating limits where the systems remain stable with key properties unaltered. Exposure to the environment can inflict damage and cause a system to lose its physicochemical characteristics, such as the coupling between a molecular layer and substrate at hybrid interfaces.
Albani et al. investigated the stability of chemical, structural, and magnetic properties of the CoTPP/Fe(001) - p(1×1)O system — a particular molecule/substrate pair that has potential applications for organic electronics — in the presence of molecular oxygen. The system consists of a single molecular layer of CoTPP, a type of metallo tetra-phenyl porphyrin with a cobalt ion in the central core, grown on top of a Fe(001) substrate modified by an ultra-thin oxide layer with a p(1×1)O superstructure.
Previous work by the authors demonstrated that magnetic coupling between the molecules and the substrate can co-exist with a high degree of structural order for this system. The current article explores the effects of oxidation on this coupling with spin-resolved UV photoemission spectroscopy, as well as potential changes to the order of the molecular layer using low-energy electron diffraction.
The results showed that the CoTPP layer’s regular commensurate super-pattern and the magnetic coupling at the interface are preserved up to an oxygen exposure of 100 L (1 L=10−6 Torr·s). After that, however, it disappears along with the diffraction pattern, which suggests a link with the order of the CoTPP layer.
In terms of future research, the authors plan to extend their investigation on the role of the interface modification to other molecule/substrate combinations. Their goal is to better understand the limits of applicability of their growth methods for creating molecular systems with a high degree of structural order and tunable properties.
Source: “Interaction of ultra-thin CoTPP films on Fe(001) with oxygen: Interplay between chemistry, order and magnetism,” by Guglielmo Albani, Alberto Calloni, Madan S. Jagadeesh, Marco Finazzi, Lamberto Duò, Franco Ciccacci, and Gianlorenzo Bussetti, Journal of Applied Physics (2020). The article can be accessed at http://doi.org/10.1063/5.0012422 .
