Seminarium Fizyki Ciała Stałego

Thermal decomposition of (Ga,Mn)As, the canonical dilute ferromagnetic semiconductor, leads to the formation of ferromagnetic α-MnAs (of hexagonal crystal structure) nanocrystals (NCs) being incoherent with the surrounding zinc-blende GaAs crystalline matrix. On the other hand, wurtzite (WZ) (Ga,Mn)As, sharing similar symmetry with hexagonal α-MnAs, can be obtained if (Ga,Mn)As is grown as shells of WZ GaAs nanowire cores. We have shown that annealing of the WZ (Ga,Mn)As at 450 °C results in tensely strained MnAs NCs embedded semi-coherently in WZ-GaAs matrix and stabilizes ferromagnetic α-MnAs phase to above 127 °C (bulk α-MnAs TC = 40 °C) [1].I will present structural changes in WZ-(Ga,Mn)As NW shell at high spatial resolution occurring under annealing by employing in-situ scanning transmission electron microscopy (STEM). I will also show how to control the granular GaAs:MnAs system to achieve the desired size and distribution of MnAs NCs by designing the core-shell nanowire system and selecting the appropriate annealing conditions. In this context, I will present the role of the (Ga,Al)As shell and the importance of the anisotropy of the WZ GaAs crystal structure in the process of manganese diffusion and the movement of MnAs NCs in the nanowires.[1] A. Kaleta, S. Kret, K. Gas, B. Kurowska, S. Kryvyi, B. Rutkowski,N.G. Szwacki, M. Sawicki, J. Sadowski, Nano Lett. 19, 7324 (2019)UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :instruction: (pdf file)