application coordinator

• Applicant: Professor Dr. Dietrich R. T. Zahn
• Subject Area: Microsystems
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 82921420

The discovery of tunneling magnetoresistance (TMR) and giant magnetoresistance (GMR) in metallic spin valves has led to a revolution of magnetic memory. The storage capacities of today’s modern hard drives increased at a rate unthinkable just ten years ago. Simultaneously, organic materials have come to the forefront of electronic devices and circuitry, since they are cheap to produce, flexible, and diverse in their applications. The combination of both, spintronics and organic electronics, is likely to lead to new generations of spin based devices, which may open a broad range of exciting and still unknown application fields and products in organic spintronics. Our research group initiative aims at the ultimate down-scaled nanostructured device integrating the spintronic functionality of single molecules. We will try to switch the spin transfer through magnetic molecules by changing the alignment of the molecular spins. This ambitious approach towards molecular spintronics combines two interdisciplinary research fields, organic electronics and molecular magnetism. Our endeavors are meant to stimulate fruitful exchange between otherwise disjunct communities, which we hope will help to discover a variety of fundamental phenomena and major physical effects as well as to unravel long-standing scientific problems and discrepancies. The great potential of molecular materials for spintronic applications resides in their weak spin-orbit coupling and hyperfine interactions. These lead to spin-coherence times much longer than in conventional metals and semiconductors, making them perfect building blocks for tunneling barriers or transport layers in spin-based hybrid devices. In addition, the molecules can be easily functionalized, which allows their controlled deposition on inorganic substrates as well as versatile engineering of their electronic and magnetic properties. This project aims at the fundamental understanding and the first experimental demonstration of spin electronic devices based on magnetic molecules. Our activities include: • Tailoring and fundamental characterization of magnetic molecules: Magnetic molecules for implementation into devices will be synthesized and fundamentally investigated by theoretical methods and experimental scanning probe techniques as well as optical and magnetic measurements of bulk materials. Already at this stage we will take into account basic compatibility aspects concerning device processing. • Fabrication, characterization, and optimization of molecular thin films and interfaces: New deposition techniques to create suitable molecular films need to be developed for a variety of molecules. The structure, morphology, and molecular orientation of the layers will be characterized and optimized. The experimental results will be complemented by theoretical predictions for properties of molecules on surfaces. For device integration, the molecular layers need to obey certain boundary conditions, such as long-term stability, process compatibility and the ability to integrate with electrode materials. Continuous feed-back from basic characterization and technology projects allows targeted and efficient synthesis of appropriate molecules and molecular films for device integration. • Device demonstration and on-chip integration: Rolled-up nanotechnology will be used to create a vertically stacked spin valve. We will also realize a laterally stacked three-terminal device for large scale integration purposes. These activities will be accompanied by theoretical investigations of electronic transport. Based on the strong links formed between the partners and the experience gained from the successful joint work during the first funding period, we have been able to realize the first prototypical devices using nonmagnetic electrodes. We will now refine the first two objectives addressed by our Research Unit to ensure the successful accomplishment of the third, i.e., the fabrication of prototypical devices with ferromagnetic electrodes. This Research Unit has access to various high-end and complementary characterization methods, ranging from static and dynamic magnetic characterization to local probe methods as well as (magneto-)optical and electron spectroscopies. This unique combination of methods is exploited to study fundamental properties of single molecules as well as synthesized molecular films. Electrical measurements, new technological concepts, and sophisticated processing facilities provide quick feedback to improve and optimize molecule synthesis and molecular film deposition procedures. During the first funding period new methods with lateral resolution in the nanometer range (tip enhanced Raman spectroscopy (TERS), photoemission microscopy, and current sensing atomic force microscopy in magnetic field) and micrometer range (micro-magneto-optical Kerr effect spectroscopy) were developed in our Research Unit and will be applied in the second funding period to study the optical, electronic, and electrical properties of the devices and the magnetic properties of the ferromagnetic electrodes, respectively. For the device fabrication, in addition to the conventional UV-lithography combined with semiconductor processing and roll-up processing already employed during the first funding period, we will have access to nanoimprint technology. Our goals require close collaboration of experts from physics, chemistry, materials science, and electrical engineering, who are available within the Free State of Saxony. The partners in the consortium are based at the four Saxonian universities (Technische Universität Chemnitz, Technische Universität Dresden, Universität Leipzig, and Technische Universität Bergakademie Freiberg) and the Leibniz-Institut für Festkörper- und Werkstoff-Forschung (IFW) Dresden. The sub-projects in this Research Unit are tailored to systematically address the whole research and development chain from molecule synthesis and molecular film deposition via fundamental characterization and theoretical understanding to device demonstration and integration. Moreover, this Research Unit particularly emphasizes the promotion of young researchers not only in the form of Ph.D. students but also of many young project leaders.

• DFG Programme: Research Units
• Subproject of: FOR 1154: Towards Molecular Spintronics