Spin-Relaxation Mechanisms in Doped Rubrene Thin-Film Crystals

• Applicant: Dr. Hans Kleemann
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495141293

Electronic devices that exploit the spin degree of freedom (spintronics) are expected to revolutionize the field of microelectronics. As fast spin relaxation mechanisms in conventional semiconductor materials, e.g., strong spin-orbit coupling, impede this development, researchers explore new classes of materials for spintronics. Organic semiconductors are among these materials and exceptional spin lifetimes of >10µs have been demonstrated for bulk single crystals. However, a general understanding of the underlying spin relaxation mechanisms and the connection to charge carrier transport is still missing and the effect of temperature, charge carrier, and defect density on the spin lifetime cannot be predicted.This project aims to analyze the spin-transport in electrically doped rubrene thin-film crystals in vertical device structures and unravel the relation between charge carrier and spin transport in this material system. Due to the high degree of crystallinity and the control of the charge carrier concentration through doping, these thin-film crystals are an ideal model system to investigate the spin and charge transport properties at the transition point between band- and hopping-like transport. Using electrically detected electron-spin-resonance spectroscopy, the time constants of spin-relaxation will be investigated as a function of temperature, charge carrier density, type of dopant, and dopant density. Based on the temperature dependence of the charge carrier mobility, the spin diffusion length will be determined to propose ideal configurations for future spin-valve devices.

• DFG Programme: Research Grants