The optical properties and coupling of excitons to surface plasmon polaritons (SPPs) in Ag, Au, and Al-coated In x Ga 1Àx N/GaN multiple and single quantum wells (SQWs) were probed with timeresolved cathodoluminescence. Excitons were generated in the metal coated SQWs by injecting a pulsed high-energy electron beam through the thin metal films. The Purcell enhancement factor (F p) was obtained by direct measurement of changes in the temperature-dependent radiative lifetime caused by the SQW exciton-SPP coupling. Three chosen plasmonic metals of Al, Ag, and Au facilitate an interesting comparison of the exciton-SPP coupling for energy ranges in which the SP energy is greater than, approximately equal to, and less than the excitonic transition energy for the InGaN/GaN QW emitter. A modeling of the temperature dependence of the Purcell enhancement factor, F p , included the effects of ohmic losses of the metals and changes in the dielectric properties due to the temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband critical point transition energies which involve the d-bands of Au and Ag. We show that an inclusion of both intraband and interband effects is essential when calculating the x vs k SPP dispersion relation, plasmon density of states (DOS), and the dependence of F p on frequency and temperature. Moreover, the "back bending" in the SPP dispersion relation when including ohmic losses can cause a finite DOS above x sp and lead to a measurable F p in a limited energy range above x sp , which can potentially be exploited in plasmonic devices utilizing Ag and Au.

The Zn 1-x Mn x Te nanosheets were synthesized by the one-pot RAPET (reaction under autogenic pressure at elevated temperature) approach. The efficient replacement of Zn by Mn within the Zn 1-x Mn x Te lattice was confirmed from electron paramagnetic resonance (EPR) experiments. The (111) facets form the main surfaces of the ∼38 nm thick nanosheet structures. Mn catalyzes the formation of a small amount of nanorods (diameter ∼2.6 nm) alongside the nanosheet structures. The magnetic measurements (EPR and SQUID) confirm the +II state of manganese in all the products. Two local environments with strong parallel or antiparallel coupling of the Mn spins exist, specially in the case of Mn:Zn ) 0.01 (T1). T1 exhibits a relatively large magnetic moment of 0.12 µ B at µ 0 H ) 1.0 T and reflects the contribution of a paramagnetic phase (with antiferromagnetic interactions) and of a ferromagnetic phase. Variable temperature cathodoluminescence measurements were performed for all samples and showed distinct ZnTe near-band edge and Mn-related luminescence. An intense and broad intra-Mn 2+ transition at relatively large Mn alloy compositions of 10-15% is further consistent with an efficient incorporation of Mn within the host ZnTe lattice. The template-free formation of the nanosheets and nanorods are explained with the help of controlled experiments. From the technological point of view, the organization of the spintronic nanomaterials into 2D or 3D architectures is important for their assemblage onto a microscopic chip and the Zn 1-x Mn x Te nanosheets is a major breakthrough toward realization of such functionality.

O ne of the important fields in nanotechnology research is the design of IIϪVI wide gap semiconductor composite structures to obtain novel properties for a variety of applications such as photonic devices, biological labeling, light-emitting diodes, and solar cells. 1Ϫ3 The most studied systems are the nanocrystals of CdSe and ZnSe, their core/shell structures or Zn x Cd 1Ϫx Se solid-solution nanocrystals and quantum dots. 4Ϫ6 It is important for the mixed nanocrystals to exhibit a wide tunable absorption spectra, high luminescence efficiency, and the ability to tune the emission characteristics by varying the size, shape, and inherent composition. However, the applicability of the luminescent nanocrystals, such as stability and high luminescent quantum efficiency under real operation conditions, suffer from the passivation of dangling bonds present on the nanocrystal surface. 7 To solve this problem, organic ligands were attached to the nanocrystal surface, which allowed high photoluminescence (PL) efficiency, but the PL efficiency was strongly dependent on the nanocrystal surroundings, due to oxidation of the particle surface. 8,9 The nanocrystals were also encapsulated with silica to make them hydrophilic for biological applications, but involved the use of toxic reactants such as tetraethyl orthosilicate (TEOS). 10 Recently, nanocrystals of diluted magnetic semiconductors were encapsulated with a carbon shell in order to reduce their toxicity for biological applications. 11,12 Moreover, carbon encapsulation of the semiconductor nanocrystals have shown to improve the optical properties and enhance the PL emission. 13,14 The ternary ZnϪCdϪSe system in the form of nanowires, 15 nanorods, 16 nanocrystals, 6 or quantum dots, 17 and the core/shell ZnSe/CdSe counterparts 18,19 were studied in great detail in the literature. The nanostructures were synthesized by a variety of techniques such as wet chemical synthesis which involve colloidal solutions, 16 cation exchange reactions, 20 and capping of the showed striations in the nanocrystals that are indicative of a composition modulation, and possibly reveal a phase separation and spinodal decomposition within the nanocrystals. Thermal quenching of the luminescence for both the near band-edge and defect related emissions were observed in the range 60؊300 K. The measured activation energies of ϳ50؊70 meV were related to the presence of shallow donors or acceptors, deep level emissions, and thermal activation and quenching of the luminescence due to the thermal release of electrons from shallow donors to the conduction band or a thermal release of holes from shallow acceptors to the valence band. Spatially integrated CL spectra revealed the existence of broadening and additional components that are consistent with the presence of a composition modulation in the nanocrystals. Spatial localization of the emission in isolated single nanocrystals was studied using monochromatic CL imaging and local CL spectroscopy. CL spectra acquired by a highly localized excitation of ...