Tailoring and Exploring Rare-Earth-Sulfides thin films with enhanced Magneto-Optical properties (TERESMO)

• Applicants: Dr. Jörg Debus; Professorin Dr. Anjana Devi
• Subject Area: Synthesis and Properties of Functional Materials ; Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258179787

The recent technical innovations in nanotechnology are mainly based on tuning the material properties. Engineering materials at the nanoscale is of utmost interest both for academic and industrial sectors. Understanding and controlling the material features at the nanometer scale lead to new and yet unexplored phenomena. With the emergence of new materials, such as 2D sulfides, there is growing interest to study their fundamental properties with the vision of employing them for future applications. Among the sulfides, the rare earth sulfides (RES) are of remarkable interest; they have barely been studied from the fundamental as well as application point of view. A fascinating topic is the optical control of their magnetic state for fast magneto-optical applications; however, their respective properties are largely unexplored. Up to now, the RES materials do not exhibit the same degree of maturity like other oxides or other metal sulfides. Most importantly there is no reliable synthetic recipe to grow these materials of high quality on a large scale. Although chemical-vapor deposition (CVD) and atomic-layer deposition (ALD) gain a lot of attention for processing metal sulfides, the synthetization of RES films is limited due to the lack of suitable RE precursors. This project will thus aim both at developing new CVD and ALD processes for EuS, Nd2S3, Er2S3, and SmS employing new precursors as well as at elaborating their magneto-opto-elastic features including the optical creation of collective ferromagnetic states (CFS) with giant magnetic moments. The drawbacks associated with RE precursors which are as-of-now limited in their physico-chemical properties will be addressed and improved by a rational approach on the ligand design. The CVD and ALD grown RES layers will then thoroughly be investigated on their crystallographic structure, composition and morphology. The layer thickness will be scaled down to nanometers, ultimately reaching 2D RES films. The layer thickness variation as well as the type of precursor are setscrews for the magneto-optical and magneto-elastic characteristics of the RES. In this respect, resonant laser spectroscopy will reveal their radiative and non-radiative interband transitions, their coupling to an external magnetic field and to the lattice as well as magnon-phonon interactions. The optical generation of CFS will further be studied in dependence on the crystallographic and magnetic structure of the RES thin films as well as on specific resonant laser excitations. The time-resolved formation and stability of the CFS are finally addressed by pump&probe Faraday rotation experiments. The newly developed RES films with tailored functional properties combined with the advanced resonant spectroscopy will provide a comprehensive insight into the potential of RES films for opto-electronic and magneto-optical applications.

• DFG Programme: Research Grants