We report propagation of exciton polaritons (EPs) in photoexcited nanofibers of thiacyanine dye over a few hundred micrometers at room temperature. We determine the complex refractive index along the nanofibers by fluorescence microscopy measurements on single nanofibers and observe its anomalous behavior due to the EP effect. The longitudinal-transverse splitting energy (ΔE(L-T)) is evaluated to be ∼1  eV. The large ΔE(L-T) and waveguide function of the nanofibers allow a millimeter propagation of EPs at room temperature, which is hardly realized in other systems.

Measurements of thickness using electron energy loss spectroscopy (EELS) are revised. Absolute thickness values can be quickly and accurately determined with the KramersKronig sum method. The EELS data analysis is even much easier with the log-ratio method, however, absolute calibration of this method requires knowledge of the mean free path of inelastic electron scattering k. The latter has been measured here in a wide range of solids and a scaling law k $ q 20.3 versus mass density q has been revealed. EELS measurements critically depend on the excitation and collection angles. This dependence has been studied experimentally and theoretically and an efficient model has been formulated. Microsc. Res. Tech. 71:626-631, 2008. V

Great suppression of fine-structure splitting (FSS) is demonstrated in self-assembled GaAs quantum dots (QDs) grown on AlGaAs(111)A surface. Due to the three-fold rotational symmetry of the growth plane, highly symmetric excitons with significantly reduced FSS are achieved. Scanning tunneling microscopy and cross-sectional transmission microscopy demonstrate a laterally symmetric dot shape with abrupt interface. Polarized photoluminescence spectra confirm excitonic transition with FSS smaller than ∼20 µeV, a substantial reduction from that of QDs grown on (100).

Mean free path of inelastic electron scattering has been measured with a 200 keV transmission electron microscope for the majority of stable elemental solids and their oxides. An oscillating behavior vs atomic number Z has been revealed, such that within one row of the Periodic Table, the minimum ͑maximum͒ of is observed for elements with completed ͑empty͒ outer d shells. A significantly weaker ͑Z͒ dependence is observed for the oxides. The ͑Z͒ variation is ascribed to the three major factors: atomic density, number of "free" electrons per atom, and contribution of atomic core-loss transitions.

Owing to its high theoretical capacity of~4200 mAh g −1 and low electrode potential (<0.35 V vs. Li + /Li), utilising silicon as anode material can boost the energy density of rechargeable lithium batteries. Nevertheless, the volume change (~300%) in silicon during lithiation/ delithiation makes stable cycling challenging. Since some of the capacity fading mechanisms do not function in solid electrolytes, silicon anodes exhibit better cycling performance in solid electrolytes than liquids. Nonetheless, capacity can fade rapidly because of the difficulties in maintaining mechanical integrity in thick/bulky electrodes, especially when high active material loading is employed to deliver practically useful areal capacity. By contrast, silicon nanostructures can relieve deformation-induced stress and enhance cycling performance. Here we report enhanced cycling performances achieved using nanostructured silicon films and inorganic solid electrolyte and show that amorphous porous silicon films maintain high capacity upon cycling (2962 mAh g −1 and 2.19 mAh cm −2 after 100 cycles).