Formation of Fe Nano-Clusters on Si(111)7x7 Surface Modified with Molecules Liliany Noviyanty Pamasi * , Haoyu Yang, Shota Nishida, Shohei Takemoto, Ken Hattori, and Hiroshi Daimon Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan * e-mail: liliany.noviyanty.lc4@ms.naist.jp The selective deposition of metals on surfaces modified with molecules adsorption is one of the key techniques to create artificial electrode patterns in atomic scale. In order to develop the selective deposition techniques, the understanding of fundamental processes in atomic scale is important. In this contribution, we used NH3 gas to modified the Si(111)7×7 surface. On Si(111)7×7 surface, NH3 molecule dissociates in a pair of a Si adatom and adjacent Si rest-atom sites by forming Si-NH2 and Si-H in faulted and unfaulted half unit-cells [1]. Thus, three Si adatoms and three Si rest-atoms in every half unit- cell are reacted at the saturation, resulting in three intact adatoms but no intact rest-atom. On clean 7 × 7 surfaces adsorbed with single atoms, an atom of many metallic elements is trapped within a basin potential around a rest-atom resulting in the hopping in the basin or adjacent basin potentials in the same half unit-cell at room temperature (RT) [2]. The rest-atom with a dangling bond plays a role of holding a metal atom, which would become a nucleation growth center. When we cap all rest-atoms with molecules, these metal adsorption and growth scenarios should be drastically changed. Recently, Yang et al. [3] revealed that single Fe atoms adsorb at intact Si adatoms on C2H5OH- saturated 7 ×7 surface, where all rest-atoms and half adatoms are reacted similar to the NH3 saturation, using a statistical analysis in STM. At increasing Fe coverage they also found a cluster formation, however, the cluster structure is not clear yet. In this presentation, we report the cluster structure grown on NH3-saturated Si(111)7×7 surfaces by Fe deposition at RT using transmission pattern in RHEED. Fig. 1 shows a typical RHEED pattern taken at the [ͳͳʹ  ] incident direction. The patterns indicated bcc-Fe(111) || Si(111) and Fe[ͳͳʹ  ] || Si[ͳ  ͳ  ʹ] orientation as seen in the clean surface [4]. This result implies that Fe atom on intact Si adatom of the Si(111) 7×7 –NH3 surface will be the nucleation site for the growth of crystalline-oriented bcc-Iron nano-cluster. References [1] R. Wolkow and Ph. Avouris, Phys. Rev. Lett., 60, 1049 (1988). [2] R. Zhachuk, B. Olshanetsky, J. Coutinho and S. Pereira, Phys. Rev. B, 81, 165424 (2010). [3] H. Yang, K. Tanaka, F. Komori, D. Ju, K. Hattori and H. Daimon, (unpublished). [4] K. Kataoka, K. Hattori, Y. Miyatake and H. Daimon, Phys. Rev. B, 74, 155406 (2006). Fig. 1: RHEED pattern of Fe (10ML) deposited Si (111)7×7-NH3 surface at the Si [ͳͳʹ  ] incident direction.