Influence of electron irradiation on hydrothermally grown zinc oxide single crystals

The resistivity of hydrothermally grown ZnO single crystals increased from similar to 10(3) Omega cm to similar to 10(6) Omega cm after 1.8 MeV electron irradiation with a fluence of similar to 10(16) cm(-2), and to similar to 10(9) Omega cm as the fluence increased to similar to 10(18) cm(-2). Defects in samples were studied by thermally stimulated current (TSC) spectroscopy and positron lifetime spectroscopy (PLS). After the electron irradiation with a fluence of 10(18) cm(-2), the normalized TSC signal increased by a factor of similar to 100. A Zn vacancy was also introduced by the electron irradiation, though with a concentration lower than expected. After annealing in air at 400 degrees C, the resistivity and the deep traps concentrations recovered to the levels of the as-grown sample, and the Zn vacancy was removed.

Exact result for the Green's function of a two-dimensional interacting electron gas with spin-orbit interaction in a perpendicular magnetic field

An exact property is established for the Green's function of a uniform two-dimensional interacting electron gas in a perpendicular magnetic field with spin-orbit interaction. It is shown that the spin-diagonal Green's function is exactly diagonal in the Landau level index even in the presence of electron-electron interactions. For the Green's function with different spin indexes, only that with adjacent Landau level indexes is non-zero. This exact result should be helpful in calculating the Green's function approximately.

Effect of electron-electron scattering on spin dephasing in a high-mobility low-density two-dimensional electron gas

By utilizing time-resolved Kerr rotation techniques, we have investigated the spin dynamics of a high-mobility low density two-dimensional electron gas in a GaAs/Al0.35Ga0.65As heterostructure in the dependence on temperature from 1.5 to 30 K. It is found that the spin relaxation/dephasing time under a magnetic field of 0.5 T exhibits a maximum of 3.12 ns around 14 K, which is superimposed on an increasing background with rising temperature. The appearance of the maximum is ascribed to that at the temperature where the crossover from the degenerate to the nondegenerate regime takes place, electron-electron Coulomb scattering becomes strongest, and thus inhomogeneous precession broadening due to the D'yakonov-Perel' mechanism becomes weakest. These results agree with the recent theoretical predictions [J. Zhou et al., Phys. Rev. B 15, 045305 (2007)], which verify the importance of electron-electron Coulomb scattering to electron spin relaxation/dephasing.

Organic light emitting diodes using magnesium doped organic acceptor as electron injection layer and silver as cathode

Organic light emitting diodes employing magnesium doped electron acceptor 3, 4, 9, 10 perylenetetracarboxylic dianhydride (Mg: PTCDA) as electron injection layer and silver as cathode were demonstrated. As compared to Mg: Ag cathode, the combination of the Mg: PTCDA layer and silver provided enhanced electron injection into tris (8-quinolinolato) aluminium. The device with 1: 2 Mg: PTCDA and Ag showed an increase of about 12% in the maximum current efficiency, mainly due to the improved hole-electron balance, and an increase of about 28% in the maximum power efficiency, as compared to the control device using Mg: Ag cathode. The properties of Mg: PTCDA composites were studied as well.

Controllable electron g-factors in HgMnTe quantum spheres

The electronic structure and Lande electron g-factors of manganese-doped HgTe quantum spheres are investigated, in the framework of the eight-band effective-mass model and the mean-field approximation. It is found that the electronic structure evolves continuously from the zero-gap configuration to an open-gap configuration with decreasing radius. The size dependence of electron g-factors is calculated with different Mn-doped effective concentration, magnetic field, and temperature values, respectively. It is found that the variations of electron g-factors are quite different for small and large quantum spheres, due to the strong exchange-induced interaction and spin-orbit coupling in the narrow-gap DMS nanocrystals. The electron g-factors are zero at a critical point of spherical radius R-c; however, by modulating the nanocrystal size their absolute values can be turned to be even 400 times larger than those in undoped cases. Copyright (c) EPLA, 2008.