Mixed-valence states of 11, 1111-dialkyl- and 11, 1111-bis(methylbenzyl)biferrocenium triiodides

It was found that the packing of cations and anions influences the electronic structures of mixed-valence binuclear ferrocene derivatives. Temperature-dependence of the mixed-valence state of 1¹, 1¹¹¹-diisobutylbiferrocenium triiodide was observed in a crystalline state, whereas only a trapped-valence state was found in a dispersed state. The packing effect was also observed for a series of 1¹, 1¹¹¹-dialkyl- and 1¹, 1¹¹¹-bis(methylbenzyl)biferrocenium triiodides by means of ESR spectroscopy.     

Application of a self-sensing conductive probe for Si device imaging

For the evaluation of two-dimensional carrier profiles in semiconductor devices, we have developed a novel form of probe–sensor combined unit that uses an etched tungsten wire as a conductive probe, and commercially available quartz tuning fork as the force sensor. This unit has a self-sensing capability due to the piezoelectric effect of quartz tuning fork, thus obviating optical setup, and its conductivity is higher and more stable than that of conventional metal-coated Si cantilever. In addition, this probe–sensor combined unit is inexpensive and easy to use, when compared to the well-known optical methods of Si-based cantilever vibration detection system. Our scanning probe microscope using this probe–sensor combined unit is able to mapping the capacitive gradient signal (dC/dZ image) and internal damping of quartz tuning fork oscillation (dissipation image) while scanning the sample surface. In this letter, we show the results of visualization of the p–n junction locus of a Si metal–oxide–semiconductor field effect transistor in both dC/dZ and dissipation images.     

Sorption of water vapor into polyelectrolyte complex of poly(styrenesulfonic acid)/poly(4-vinyl-N-ethylpyridinium bromide)

Successive differential and integral sorptions of water vapor into the polyelectrolyte complex of poly (sty renesulfonic acid) / poly(4-vinyl-N-ethylpyridinum bromide) have been measured; films of stoichiometric (1/1 molar ratio) and nonstoichiometric (2/1 molar ratio) complex were employed in the experiments. Sorption isotherms have been also determined by using the values obtained from integral sorption experiments. The sorption data have suggested the following. (i) The rearrangement of polymer chains plays a relatively unimportant role in sorption of water. (ii) The relaxation motion of network chains is suppressed. (iii) The change of morphological structure caused by vapor sorption is obscure. (iv) The ionic character of the 1/1 complex is higher than that of 2/1 complex. (v) A small amount of water can be dispersed on specific polymer sites, but the sorption of a large amount of water is accompanied by an expansion of network structure. Points (i)-(v) have been consistently interpreted on the basis of the network structure and ionic character of this complex.     

Eu-Doped KCl storage phosphor for erasable and rewritable optical memory utilizing photostimulated luminescence phenomenon

Intense photostimulated luminescence (PSL) with a peak at 420 nm is observed in ultraviolet (UV) Iight-irradiated europium-doped potassium chloride (KCl: Eu) crystalline phosphors. The PSL characteristics of UV-irradiated KCl: Eu phosphor for optical memory application were studied. The excitation and emission mechanisms of the 420 nm PSL, which are consistent with the results obtained, are discussed.     

Transformation of resonant Raman scattering into luminescence in CdxZn1−xTe mixed crystals: Time-resolved spectroscopy

We report an experimental study of time characteristics of secondary emission in Cd_xZn_1-xTe mixed crystals (x = 0.32) under resonant excitation with a picosecond dye laser. When the incident laser frequency is tuned on to the luminescence maximum of localized excitons, the decay curve of the intensity of “Raman-like” lines exhibits a single exponential decay. Off resonance, however, a short-lived component corresponding to Raman scattering appears in addition to the long-lived component. The intensity of the Raman component relative to that of the luminescence component increases with increase of the off-resonance frequency. From these temporal behaviors, we have found, for the first time, the transformation of resonant Raman scattering into luminescence in mixed crystals as a function of incident frequencies.     

Photoinduced Ordering Transition in Microdroplets of Liquid Crystals with Azo‐Dendrimer

Ordering transitions are observed in azo‐dendrimer‐dissolved nematic liquid crystal (NLC) droplets dispersed in a glycerol matrix. The dendrimer molecules are spontaneously attached at the interface between NLC and glycerol, so that the nematic directors orient perpendicular to the interface, in the radial configuration. Photoisomerization makes the directors be tangential to the interface, in a photoinduced ordering transition from radial to bipolar structure. Similar experiments are conducted both in cholesteric (Ch) and smectic‐A (SmA) LC droplets. Complicated photoinduced ordering transitions are also observed in Ch and SmA droplets, and the associated molecular orientation changes are discussed. Photoisomerizable azo‐dendrimer molecules provide a possible way to control orientation, even in microdroplet systems in which the interface cannot be treated by conventional surface agents.