在具有Cu衬底层的Si（111）面上自组装Co团簇的研究

Nanodots as low dimensional surface structures exhibit interesting physical properties which can be exploited in numerous applications such as a single electron transistor, optoelectronic- and magnetic storage-devices etc. Since the top-down techniques used currently are reaching their limits, the bottom-up self-assembly is probably the most promising technique for the growth of nanoscale systems due to the striving of a system toward a minimal energy and the formation of nanosized structures down to the atomic level. Nevertheless, controlling and tailoring the size and distribution of these nanodotes for possible devices is a challenge and requires a thorough knowledge of the complex interaction between atoms and surface. Since cobalt is regarded as one of the most important elements used in magnetic materials for magnetic or magneto-optical devices and silicon is the key element used in the semiconductor industry, the combination of these two materials will promote the development of materials and devices for next-century magnetoelectronics. However, it is known that Co reacts easily with Si even at room temperature [1]. Nevertheless, recent works have shown that a buffer layer still strongly affects the surface diffusion of deposited atoms and the subsequent island nucleation [2-5]. Annealing of monolayer (ML) amounts of Cu on Si(111) leads to an (5.55×5.55) periodic reconstruction with excellent thermal stability. Although the Cu/Si(111) layer does not exhibit a true long range periodicity, its good stability, together with the significant removal of the Si dangling bonds, indicates that it is a good template for the fabrication of self-assembled Co nanoclusters. As far as we know, there are few studies of Co/Cu/Si(111) system. The present study provides the structural property of self-assembled Co nanoclusters on Cu/Si(111) surface using scanning tunneling microscopy (STM). STM and LEED results show that the Co nanolusters changes not only in the island size but also in the island shape and structures on the top of the islands with increasing substrate temperature from room temperature to 830K during deposition. It was confirmed that the ultrathin buffer layer on Si (111) surface has a significant influence on the surface morphology after subsequent depostiong of Co. On one hand it can partly prevent Co to form Co silicide. On the other hand the diffusion of Co atoms on the surface can be greatly enhanced. [1] J. M. Phillips, J. L. Batstone, J. C. Hensel, I. Wu. M. Cerullo, J. Mater. Res. 5, 1032 (1990). [2] X. Liu, T. Iimori, K. Nakatsuji, and F. Komori, Appl. Phys. Lett. 88, 133102 (2006). [3] T. Schmidt, J. I. Flege, S. Gangopadhyay, T. Clausen, A. Locatelli, S. Heun, and J. Falta, Phys. Rev. Lett. 98, 066104 (2007) [4] P. Aivaliotis, L. R. Wilson, E. A. Zibik, J. W. Cockburn, M. J. Steer, and H. Y. Liu, Appl. Phys. Lett. 91, 013503 (2007). [5] Y. Takagi, A. Nishimura, A. Nagashima, and J. Yoshino, Surf. Sci. 514, 167 (2002). Keywords: STM, Si surface, Co silicide, nanoclusters

正逆光電子分光によるFe(Se,Te)の電子状態研究(鉄系高温超伝導の物理,研究会報告)

この論文は国立情報学研究所の電子図書館事業により電子化されました