Thesis presented December 14, 2006
Abstract: Inserting magnetic impurities into semiconductor bulk materials leads to a ferromagnetic behavior. On the other hand, quantum dots confine carrier in all the space directions, allowing their individual control. This work deals with the insertion of a single magnetic impurity into a single II-VI semiconductor quantum dot. A straight-forward study of this interaction is performed with simple experimental set-ups.: a single spin can be detected and controlled with only optical means. This makes this system a candidate for a quantum-bit.
Molecular Beam Epitaxy sample growth first presented. Manganese segregation along the growth is used to reduce, and still control, Mn density to a very low value. Optical micro spectroscopy experiments assess this method. Then, a fine study of the interaction between the impurity and carrier in the quantum dot is achieved. Experimental spectra are analyzed with the help of a simple medialization of the wave function of the carriers confined in the dot. Quantitative values of this interaction are shown, including the effect of the impurity position in the dot and its confined-induced reduction.
Finally, some possibilities to control this interaction are presented: its modification with the adding of carriers into the dot, and its increase with a better hole confinement.
Keywords: semiconductors, diluted magnetic semiconductors, quantum dots, wave function, molecular beam epitaxy
On-line thesis.