No abstract

A comprehensive study of the photoluminescence dynamics in newly developed CdSe/ZnS quantum dots with alloyed core/shell interfaces is presented. Time-correlated single photon counting is used to measure the decay of exciton luminescence from both the ensemble and individual quantum dots. For decreasing emission wavelength (i.e., for smaller dots), the ensemble data reveal increasing total decay rates with greater variation. This systematic change is expected for emitters with stronger quantum confinement and more influenced by the surface/interface trap states. In experiments performed on single quantum dots, the photoluminescence trajectories exhibit two-state blinking behavior. The distributions of the "off"-state probability density are described by an average power-law exponent of 1.5 6 0.2, while the average decay rate of emission from the threshold-discriminated "on"-states is estimated to be 0.035 6 0.004 ns À1 . We suggest that in core/shell quantum dots with a large bandgap offset, the compositionally graded energy profile at the interface may not be smooth enough to suppress nonradiative Auger recombination and prevent blinking.

We report ferromagnetic resonance (FMR) studies of epitaxial MnO∕GaMnAs bilayers. The FMR data have revealed a distinct unidirectional anisotropy about the [11¯0] axis, which we attribute to exchange biasing of ferromagnetic GaMnAs by the adjacent antiferromagnetic MnO layer. The observed unidirectional anisotropy is surprisingly robust with respect to temperature and changing magnetic field.

Articles you may be interested inInvestigation of superlattices based on ferromagnetic semiconductor GaMnAs by planar Hall effect J. Appl. Phys. 111, 07D310 (2012); 10.1063/1.3678436 Magnetic anisotropy in (Ga,Mn)As grown on vicinal GaAs: Effects of the orientation of microwave magnetic field J. Appl. Phys. 109, 07C301 (2011); 10.1063/1.3535426 Quantitative analysis of the angle dependence of planar Hall effect observed in ferromagnetic GaMnAs film

No abstract