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

我们一直在研究控制电荷从半导体表面转移到吸附膜的新方法，这是基于我们最近利用同步辐射和激光的新的芯能级光电子能谱以及负电子亲和势表面的形成的成就。这与半导体表面势的瞬态变化、光生电荷转移动力学、自旋极化电子、光生相变等重要问题密切相关，本研究的目的是将上述技术应用于半导体与智能材料的界面，控制材料的性质和自旋特性。此外，还介绍了与界面动力学有关的重要基础课题，如界面势、非平衡动力学、光致电荷转移、新性质的产生等。(1)In今年我们总结了GaAs上的负电子阿米蒂表面。我们还对GaAs和GaAsP-GaAs超晶格的表面光电压效应进行了时间分辨测量，并建立了表面光电压效应的动力学模型。研究结果已发表在期刊上。（2）在此基础上，我们进一步研究了表面和界面的光致效应。在p-GaAs（100）/Cr系统中，尽管有抑制的预期，但仍观察到明显的变化。虽然预期在p-GaN上会有很大的光效应，但表面光电压效应的光子通量依赖性并不简单，并且显示出异常行为。分析工作正在进行中。(3)In为了研究表面的快速动力学，我们还测试了由强飞秒激光器和稀有气体室组成的新系统。新的显微镜系统正在建设中。

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.