ICS84

Invited
Controlling spin properties in colloidal nanocrystals

Efrat Lifshitz 1 Yahel Barak 1 Joanna Dehnel 1 Rotem Strassberg 1 Savas Delikanli 2,3 Alyssa Kostadinov 1 Pedro Ludwig Hernandez-Martinez 2 Manoj Sharma 2,3 Volkan Hilmi Demir 2,3
1Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa, Israel
2Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences and School of Materials Science and Engineering, Nanyang Technological University, Singapore
3Department of Electrical and Electronics Engineering, Department of Physics and UNAM – Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Turkey

The control of individual spins in semiconductor nanocrystals is an emerging scientific field which undoubtedly play an important role in the development of new spin-based technologies. Generation of individual spins via incorporation of magnetic ions into colloidal nanocrystals became a hot topic in recent years. These diluted magnetic semiconductor (DMS) nanocrystals are subject to a size confinement on photo-generated carriers, which markedly enhances the mutual carrier-dopant spin-exchange interaction, consequently leading to a pronounced modification of the host`s optical and magneto-optical properties.

Here we described the synthesis and characterization of DMS nanocrystals based on colloidal nanoplatelets, rods or spherical host semiconductor matrices, embedded with extremely low concentration of Mn+2 or Cu+ ions. This work includes host nanocrystals with a core/shell design (one semiconductor covered by another semiconductor) with dopant ions positioned either in the core or in the shell, using the layer-by-layer deposition. Thus, the work here discusses the influence of internal design on the magneto-optical properties of DMS colloidal nanocrystals. The research involved the use of magneto-photoluminescence (MPL) and optically detected magnetic resonance (ODMR) spectroscopy. The MPL spectra recorded at various temperatures and strength of magnetic field revealed the generation of giant magnetization (~ 30 Tesla) and g-factor ( ~ -4) of the exciton upon doping. The ODMR spectra of those samples designated a resonance line with a distinguished sextet related to the hyperfine interaction between the photo-generated electron and the surrounding nuclear spins of the dopants. The ODMR explored, for the first time, a control of nuclear spins on the magneto-optical properties of DMS nanocrystals. Furthermore, a time resolved ODMR experiment also revealed a shortening of the spin coherence time with respect to estimations, due to the hyperfine interaction. The carrier-nuclear spin may occur either directly, or mediated via the carrier-dopant electron spin (the sp-d interaction).









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