Structure of chemically synthesized nanophase GaAs studied by nuclear magnetic resonance and x-ray diffraction

Nanophase GaAs produced by organometallic synthesis was studied by 71Ga, 69Ga, and 75As nuclear magnetic resonance (NMR) as well as x-ray diffraction. The structure of the samples synthesized below 250°C is predominantly amorphous. Raising the temperature of synthesis (or post-synthesis annealing) above 280°C improves significantly the crystallinity as evidenced by the appearance of a sharp bulklike 71Ga (and 69Ga) peak. In addition, a sharp peak shifted up-field also appears. Other NMR features of this up-field shifted peak are very similar to the bulklike peak including quadrupole interactions and spin-lattice and spin-spin relaxations. These results are consistent with the presence of stacking faults in nanocrystalline GaAs

Evolution of the electronic structure with size in II-VI semiconductor nanocrystals

In order to provide a quantitatively accurate description of the band gap variation with sizes in various II-VI semiconductor nanocrystals, we make use of the recently reported tight-binding parametrization of the corresponding bulk systems. Using the same tight-binding scheme and parameters, we calculate the electronic structure of II-VI nanocrystals in real space with sizes ranging between 5 and 80 {\AA} in diameter. A comparison with available experimental results from the literature shows an excellent agreement over the entire range of sizes.Comment: 17 pages, 4 figures, accepted in Phys. Rev.

Excitations in doped quantum dot induced by randomly fluctuating magnetic field: influence of impurity

We explore the excitation profile of a repulsive impurity doped quantum dot under randomly fluctuating magnetic field. We have considered Gaussian impurity centers. The investigation reveals the roles subtly played by the dopant coordinate, dopant strength, and the region of influence of the dopant to modulate the excitation pattern. The rate of transition to the excited states has been invoked to analyze the roles played by the above impurity parameters in influencing the excitation process. Quantum phase space plots are often exploited to support the findings. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2011