Electronic states of Ni(7 9 11) surfaces were studied by angle-resolved ultraviolet photoelectron spectroscopy using synchrotron radiation. The existence of a surface electronic state characteristic of the step and one associated with the terrace is shown from studies of the effect of alkali metal adsorption and the polarization dependence of photoelectron spectra.PACS numbers: 73.20.At, 79.60.Bm Electronic states of plane surfaces of metal single crystals have been extensively investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). The existence of surface electronic states with twodimensional nature on those surfaces has been revealed through studies of photon energy dependence and angular distribution of photoelectron spectra [1], On a stepped surface of a metal crystal, there are periodical rows of monatomic steps or kinks separated by terrace planes. One could expect the formation of some new electronic states localized at step edges. Such electronic states might exhibit more or less one-dimensional character. Although ARUPS experiments were carried out on stepped metal surfaces, experimental identification of the electronic state specific to steps has been unsuccessful so far [2][3][4][5]. Therefore it is widely believed that no specific electronic state exists at steps possibly because of the derealization of electrons in metals. However, there is the possibility that the photoelectron signals due to step electronic states overlap those of the bulk and terrace electronic states, and are hard to separate from the latter in the ARUPS experiments utilizing an inert-gas discharge lamp as the stimulating light. When the synchrotron radiation (SR) is used, one could obtain much information by tuning the photon energy of stimulating light and by changing the polarization direction. In this Letter, we report the results obtained by ARUPS experiments utilizing SR on a Ni(79 11) =5(11 l)x(TOl) stepped surface and its alkali-adsorbed states. We have found for the first time evidence for the existence of new electronic states localized at step edges [6].Experiments were carried out by use of an ARUPS apparatus based on beam line ADES 400 (VG Scientific) at BL7-B [7] in Photon Factory, National Laboratory for High Energy Physics by using linearly polarized radiations in the photon energy range from 5 to 50 eV, the base pressure of the apparatus being under 1 x 10 " 8 Pa. Samples of Ni(79 11) were obtained by spark cutting a Ni single crystal rod (Johnson Matthey, 5N). Sample surfaces were first polished mechanically and electrochemically in air and then cleaned by repeated cycles of Ar + sputtering and annealing at 800 °C within the experimental apparatus. It was confirmed by means of the incident energy dependence of the LEED pattern that, on the clean surface, the periodical rows of monatomic steps expected for Ni(79 11) surfaces were arranged along [T2l] as illustrated in Fig. 1. The geometry of ARUPS measurements is also shown in Fig. 1. The electric vector of incident light and the direction...

We have observed the electronic states at conducting polymer/conducting oxide interfaces using a low-energy photoelectron spectroscopic method. The electronic states of conducting polymer/indium tin oxide (ITO) interfaces were different from those of conducting polymer/metal interfaces. The electron transfer from a conducting polymer to ITO occurred at the interfaces, and is not related to the difference of the ionization potential between conducting polymers and ITO. Although the origin of this electron transfer is not clear at this stage, we speculate that the surface states of ITO play a major role. Moreover, the electron transfer at the interfaces is enhanced at higher temperatures. Other conducting oxides such as indium oxide (In2O3) and tin oxide (SnO2) also show a similar tendency to that of ITO.

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The thermochromic behaviors of poly(2,5-dialkoxy-p-phenylene vinylene)s (ROPPVs) have been studied. The temperature dependence of electrical and optical properties and the variation of properties with the side chain length have been compared with those of poly(3-alkylthiophene)s (PATs). The band-gap energy of ROPPV16 increases gradually from about 2.2 eV at room temperature to about 2.4 eV at 200°C. This temperature dependence of band-gap energy is different from those of PATs, and the difference can be tentatively interpreted in terms of the main chain structure. The photoluminescence intensities of ROPPVs decrease monotonically with increasing temperature. To explain this mechanism, we speculate on the separation of the excited species due to the reduction of distance between polymer main chains and the enhancement of the overlap of π-electrons with the twist of polymer main chains. The ionization potentials of ROPPVs decrease slightly with increasing temperature. However, the origin of this temperature dependence is not clear at this stage.