Nesta quarta-feira, dia 01 de junho de 2011, às 13hs, na Sala 03, Heitor Alves de Melo apresentará o trabalho intitulado:  

Electronic Properties of Quantum Dots Containing Many Electrons

H. A. de Melo, J. S. de Sousa e G. A. Farias


ABSTRACT: We calculate the maximum number of electrons that can be stored in a Si spherical quantum dot embedded in dielectric matrices (SiO_{2}/HfO_{2}). The theoretical methods used is based on a simplified version of the method Hartee-Fock, however the self-consistent field is absent in this model, our results were compared and is in agreement with other literature results. The obtained results show that the total energy is always larger for SiO_{2} than for HfO_{2}. Physically, this effect is caused by the fact that SiO_{2} has larger confinement barriers (2 eV) than HfO_{2} (1.0 eV). Smaller barriers favors larger spatial extent of the wavefunctions, decreasing the repulsion energy of the confined electrons. The chemical potential and additional energy was also calculated as function of the number of confined electrons. It was observed that the chemical potential for SiO_{2} is lager than for HfO_{2}. With respect to the additional energy, we observed that is about equal to J, independent of the number of electrons. If one takes into account that the Coulomb blockade phenomena is only observed for additional energies much larger the thermal energy (of the order of 3/2k_{B}T), this phenomena can only be observed for the case where there are only a few electrons confined in the quantum dots.