Generator Of Spin-current And Spread Of The Energy Gap In Quantum-dot

As we know, the properties of nanostructure material are very different from these in macroscopic level, because of the size effects. The discrete energy levels in the nanostructure which can influence the electronic transport and optical properties. In this thesis, we report some result on the growth of the pure spin current and the spread of the energy gap in nanostructure.Recently, considerable attention is being paid to the blue-shift of the nanostructure. We study the electronic energy spectra and confinement energies by solving the Schrodinger equation accurately, using two simple model of one-dimensional, under this model. We analyse the band gap blue shift of nanostructure by calculating the confinement energies in nanostructure and discussing the size-confinement energies and potential-confinement energies characteristic curve. The results suggest that the QDs with small size have a higher electron energy at the bottom of the conduction band and lower electron energy at the top of the valence band. So the confinement energies increased abrupt as the size of nano-particle decreased. Meanwhile, the confinement energies which are calculated by the effective mass approximation referred in many literatures are very different from the result we calculate by Schrodinger, when the particle size is small. Moreover, we also find that band gap blue shift depends on the potential in the particle. The confinement energies decreased as the potential increased.Meanwhile, in order to get a generator of spin current, we propose a three terminals spin device, which composed of a ferromagnetic metal lead (source), a semiconductor lead (collector) and a paramagnetic control electrode. Each of the terminals has a bias voltage. For proper tunnel rates and other parameters, the pure spin current can be obtained in one of the terminal, by modulating the controlling voltage.