Influence of magnetic doping on magneto-optical properties of semiconductor nanocrystals

TYPESolid State Institute Seminar
Speaker:Mr. Yahel Barak
Affiliation:Department of Chemistry and Solid State Institute, Technionoli
Time:12:30 - 13:30
Location:Solid State Auditorium(Entrance)
Remark:Ph.D.Student of Prof. Efrat Lifshitz

Colloidal nanostructures are known for their tunable optical properties by variation of size, shape, and composition, while
magnetically doped nanostructures endow them with an additional degree of freedom. The confined structures enhance
interaction between photo-generated carriers (electron and hole) and spins of the magnetic impurities, hence, encouraging
unique properties, like giant magnetization and giant g-factor of the carriers. The degree of magnetization depends on the
shape, size, type of impurity, and position concerning the host-carrier distribution function. The carrier-impurity interaction
was mainly investigated using an optically detected magnetic resonance (ODMR) spectroscopy. An ODMR spectrum refers to
a plot of a change in luminescence intensity due to a magnetic resonance perturbation at the excited state. Modulation
dependence ODMR can revile the spin dynamics in the NCs. Theoretical model, using spin Hamiltonian containing Zeeman
interaction, carrier-impurity spin-exchange, and electron-hole exchange interactions, assisted in simulating the ODMR
The first and second projects focused on the magneto-optical properties of Mn
+2 ions embedded in CdSe/CdS nanoplatelets
(NPLs) and nanorods (NRs), positioning a single or a few Mn
+2 ions in the shell regime. The pristine CdSe/CdS structures
mainly show a quasi-type-II band-edge energy alignment between the core and the shell constituents, allowing electron
distribution over the entire structure. So, selective positioning of magnetic impurities in the shell regime permits selective
monitoring of the electron-Mn
+2 spin-exchange interaction. The experimental results showed a major band, with a sextet split
fine structure between the NPLs and a two-band with a different character in the NRs. The third project included the study of
the Cu@CdSe/CdS and CuInS2/(CdS) CQDs. The study focuses on open questions related to the oxidation state of the copper
ions, identification of their local sites and on the influence of the surrounding on the radiative and spin relaxation times. The
fourth project investigates Ni
2+ ions doping into cesium lead halide perovskite with a chemical formula CsPb(Br1-xClx)3. The
study revealed spin-flip processes of both electron and hole with g-phenomenological factors deviating from the electronic
band-edge, indicating their localization or shallow trapping at halide or metal vacancies. Moreover, the study provided rich
information about the recombination processes.
The discussed materials are of particular interest for various future applications such as electro-luminescent display,
photovoltaic cells, and spin-based technologies.

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