Control of material properties with photo-induced charge transfer using negative electron affinity surface

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We have been investigating the new way to control the charge transfer from semiconductor surfaces to the adsorbed films, which is based on our recent achievement of the new core-level photoelectron spectroscopy using, synchrotron radiation and laser light and also of the formation for, the negative-electron affinity surfaces. This is closely related the important problems such as transient change in the surface potential, dynamics of the photo-induced charge transfer, spin-polarized electrons, photo-induced phase transitions.The purpose of the present study is to apply the techniques mentioned above for the interface between the semiconductors and intelligent materials and control the material properties and spin,characters. Moreover, the important basic subjects related to the interfacial dynamics such as interfacial potential, non-equilibrium dynamics, photo-induced charge transfer, and production of new properties.(1)In this year, we have summarized the negative electron amity surfaces on GaAs. Also we have conducted the time-resolved measurements of surface photo-voltage effect and constructed the dynamical model for surface photo-voltage effects on GaAs and GaAsP-GaAs superlattices. The results have been published in the journals.(2)Based on the above results, we have developed our studies to the photo-induced phenomena on surfaces nad interfaces. The appreciable change was observed on p-GaAs(100)/Cr system in spite of the expectation for the suppression. Although the large photo-effect is expected on p-GaN, the photon-flux dependence of the surface photovoltage effect is not simple and shows the anomalous behavior. The analyses are under progress.(3)In order to investigate the fast dynamics of the surfaces, we have also been testing the new system consisted of an intense femt-second laser and a rare-gaseous chamber. The new microscopy system is under construction.