Accueil du site > Vie du laboratoire > Congrès / Colloques / Conférences > Optical Properties of Individual Nanowires and Quantum Dots in High Magnetic Field, Septembre 2014 > Programme du workshop > (Cd,Mn)Te quantum dots in core-shell nanowires


(Cd,Mn)Te quantum dots in core-shell nanowires

A. Artiolia, P. Rueda-Fonsecaa,b, T. Cremelb, E. Bellet-Amalricb, M. Den Hertoga, C. Bougerola, Y. Genuista, J.-F. Mottea, F. Donatinia, R. Andréa, K. Khengb, J. Bleuseb, E. Robinb, S. Tatarenkoa, D. Ferranda*, and J. Ciberta

aUniv. Grenoble Alpes, Inst. NEEL, Grenoble, & CNRS, Inst. NEEL, F-38000 Grenoble, France
bUniv. Grenoble Alpes, INAC, Grenoble, & CEA, INAC, F 38054 Grenoble, France

Confinement effects are known to enhance the stability of magnetic polarons and this was demonstrated on magnetic polarons formed around excitons in Stranski-Krastanov quantum dots and in nanocristallites [2]. A second parameter to control is the magnetic anisotropy, which is essentially due to the built-in strain. And finally, it is important to turn to polarons formed not around excitons with a finite lifetime, but around a confined carrier or even several confined carriers. In order to control these various parameters, the most flexible structure is a quantum dot inserted in a core-shell nanowire : the size and shape and the Mn density are determined by the growth conditions, and a proper choice of the shell allows tailoring the strain in the dot and achieving electrical doping. Then the challenge is to measure the characteristics of the quantum dot and the properties of the magnetic polaron on the same single quantum dot.

ZnTe-(Zn,Mg)Te core-shell nanowires have been grown by molecular beam epitaxy [2,3], with a (Cd,Mn)Te quantum dot. Such nanowires were transferred individually onto home-made, 50-nm thick, Si3N4-based membranes using the nano-manipulator of a ZEISS Cross Beam NVision 40. This allows us to perform, on the same nanowire, a wide range of experiments including electron microscopy, energy-dispersive X-ray spectroscopy (EDX), cathodoluminescence and magneto-optical spectroscopy. Fig. 1 is an example of such combined studies, with the scanning electron microscopy images, the identification of the quantum dot by the Cd and Zn EDX maps, and the giant Zeeman effect observed in photoluminescence which confirms the presence of Mn in the dot. This confirms the relevance of such nanostructures for quantitative studies of fully controlled ultimate magnetic objects. Funded by French ANR.

1. R. Beaulac et al., Science 325, 973 (2009).

2. P. Rueda et al., Nano Lett. 14, 1877 (2014).

3. A. Artioli et al., Appl. Phys. Lett. 103, 222106 (2013).