Manipulation of Atoms and Molecules by Electronic Excitation

在1998-2001财政年度开展的这一优先领域项目旨在与共享共同材料系统和思想的8个研究小组合作，阐明电子激发诱导半导体中原子运动的机制的全貌，从而开发出操纵固体材料中高度可控(选择性)和高效的原子和分子的新技术，有望有助于实现下一代器件。实际研究的材料包括典型的半导体材料，如硅、碳和砷化镓，电子激发方法有基于光子照射(激光和X射线)、粒子束(电子和离子)、电流注入和电荷状态控制。今年的活动致力于总结三年项目，包括两次小组组长委员会会议，一次公开研讨会，以及出版一份通讯。通过这些活动，我们提出了一个提高效率和电子激发对原子和分子操纵的选择性的一般指导方针：有效可控的材料系统应该是由于轨道简并激发态而具有固有结构不稳定性的半导体中的缺陷中心，在激发态中具有高迁移率的氢等轻元素，具有结构柔性的缺陷或表面，以及具有柔性轨道杂化的碳固体。利用高密度激发、合作激发和平行过程产生的长寿命双空穴态也将提高初级激发的效率。此外，为了在局域激发中达到预期的位置选择性，有必要抑制扩展带态中激发电子(空穴)的空间扩散。

This priority area project carried out in 1998- 2001 FY aimed to elucidate, with cooperation of 8 research groups sharing common material systems and thoughts, the whole picture of the mechanisms of electronic excitation induced atomic movements in semiconductors thereby developing novel techniques for manipulating atoms and molecules with high controllability (selectivity) and efficiency in solid materials that are expected to be useful for realization of next generation devices. The materials actually studied have included typical semiconductors such as Si, C and GaAs, and the electronic excitation methods have been based on photon illumination (laser and X-ray), particle beams (electron and ion), current injection, and charge state control. The activities this year, devoted to summarizing the 3 years project, have included two committee meetings of group leaders, an open workshop, and publication of a News Letter. Through these activities, we have proposed a general guide line for enhancing the efficiency and : the selectivity of atomic and molecular manipulation by electronic excitations : The material systems efficiently controllable should be defect centers in semiconductors possessing inherent structural instability due to orbitally-degenerate excited states, light elements such as hydrogens with high mobility in the excited states, defects or surfaces with structural flexibility, and carbon solids with flexible orbital hybridization. The use of long lifetime two-hole states generated by high density excitations, cooperative excitations and parallel processes will also promote the efficiency of the primary excitations. Further, to attain the site-selectivity expected in localized excitations, it is necessary to suppress the spatial spread of the excited electrons (holes) in the extended band states.