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Hefei Research Institute Makes Progress in Spin Transmission Research of Organic Semiconductors
[ Instrument Network Instrument R & D ] Recently, researchers at the High Magnetic Field Science Center of the Hefei Institute of Material Science of the Chinese Academy of Sciences have made new progress in the spin current detection of polymer semiconductors and the study of their thin film structure-spin transport properties. Published online by ACS Applied Materials & Interfaces, a journal of the American Chemical Society.
Organic semiconductor materials have weak spin-orbit coupling and ultra-fine interactions and can be used as promising spin-polarized transmission media. Therefore, it is of great significance to find new organic spin electronic materials and explore their spin-polarized transmission processes and mechanisms. . Previous studies in this area mostly used organic spin valve devices to measure electron transport with spin polarization, but there were problems such as conductance mismatch at the ferromagnetic / semiconductor interface, which seriously restricted the quantitative deepening of the spin transfer characteristics of organic semiconductors. the study. In recent years, spin-pumped excitation and detection of pure spin currents (without accompanying net charge currents) have gradually become a powerful means to explore the intrinsic spin transport properties of semiconductor materials because they can overcome the problem of interface conductance mismatch.
Zhang Fapei's group from the High Magnetic Field Center collaborated with researcher Tong Wei to study the spin-polarized transmission of a new polymer semiconductor PBDTTT-CT using ferromagnetic resonance (FMR) spin pumping technology combined with inverse spin Hall effect (ISHE) measurement. characteristic. By designing a sample holder suitable for low-noise voltage measurement, they detected a clear ISHE signal in the NiFe / polymer / Pt sandwich structure. By measuring the change in ISHE voltage with the thickness of the PBDTTT layer, they observed pure spin in the PBDTTT layer. Streaming and long spin relaxation time.
Surprisingly, for the first time, researchers have used semiconductor / insulator polymer blend films as spin-polarized transmission media, and they can still measure in blend films formed from low-level PBDTTT and insulated polystyrene (PS). Strong ISHE voltage signal, and found that the spin diffusion length and carrier mobility of the blended films are significantly improved compared to "pure" PBDTTT films. Through comprehensive film microstructure measurement, they found that the PBDTTT backbone chain bundles formed interconnected nanofilament networks in the insulated PS matrix, forming a fast charge conduction path through the film, which could explain the higher charge and spin of the blended film. Transmission capacity. In addition, it was found that the spin diffusion length of PBDTTT has a weak temperature dependence, which is consistent with the spin relaxation mechanism based on spin-orbit coupling.
These results clearly show that the structure characteristics of organic semiconductor films, such as molecular orientation and stacking mode, and film morphology, have a critical effect on their spin transport properties. This work is of great significance for understanding the microscopic processes and mechanisms of spin-polarized transport of organic semiconductors, and provides a new way to find low-cost, high-performance organic spin electronic materials.
The research was supported by the National Natural Science Foundation of China and key national R & D projects.