shows SEM and SAM images of an array of bimetallic dots composed of Au and Ag. In the SEM image in Figure 3a, the Au deposits are observed as brighter ellipsoidal dots than Ag. The SAM image in Figure 3b shows more clearly the alter- nately arranged ordered array of Au and Ag dots on the Si sub- strate. Figure 4 shows the high spatial resolution of this process for a dot array of three components. This structure was fabricated by three-step evaporation of Au by changing the incident an- gle. The nominal thickness of each deposit was 20 nm. In the circles of ca. 80 nm diameter, three deposits can be clearly ob- served. This result confirms that the present process offers high controllability of the site of the components in each dot via the adjustment of the incident angle of the beam. Fig. 4. SEM image of the array of multiple dots of three deposits of Au. The fabrication of an array of ordered multiple dots could be achieved in nanometer dimensions. The dimensions of the hole array structure used as a mask are dependent on the fab- rication conditions. Anodization under low-voltage conditions generates a through-hole membrane with reduced dimen- sions. [7] Application of such membranes as a mask will gener- ate multiple dot arrays with finer dimensions. Received: March 20, 2000 ± [1] K. Douglas, G. Devaud, N. Clark, Science 1992, 257, 642. [2] H. Deckman, J. H. Dunsmuir, Appl. Phys. Lett. 1982, 41, 377. [3] M. Park, C. Harrison, P. M. Chaikin, R. A. Register, D. H. Adamson, Science 1997, 276, 1401. [4] H. Masuda, M. Satoh, Jpn. J. Appl. Phys. 1996, 35, L126. [5] F. Keller, M. S. Hunter, D. L. Robinson, J. Electrochem. Soc. 1953, 100, 411. [6] H. Masuda, K. Fukuda, Science 1995, 268, 146. [7] H. Masuda, F. Hasegawa, S. Ono, J. Electrochem. Soc. 1997, 144, L127. [8] H. Masuda, K. Yada, A. Ohsaka, Jpn. J. Appl. Phys. 1998, 37, L1340. [9] O. Jessensky, F. Muller, U. Gosele, Appl. Phys. Lett. 1998, 72, 1173. [10] L. Zhang,H. S. Cho, F. Li, R. M. Metzger, W. D. Doyle, J. Mater. Sci. Lett. 1998, 17, 291. [11] F. Sharifi, A. V. Herzog, R. C. Dynes, Phys. Rev. Lett. 1993, 71, 428. [12] E. Olson, G. C. Spalding, A. M. Goldman, Appl. Phys. Lett. 1994, 65, 2740. [13] J. Brunner, T. S. Rupp, H. Gossener, R. Ritter, I. Eisele, G. Abstreiter, Appl. Phys. Lett. 1994, 64, 994. [14] S. Santucci, P. Picozzi, L. Paoletti, F. Tangucci, Thin Solid Films 1981, 79, 133. [15] R. M. Bright, D. G. Ealter, M. D. Musick, M. A. Jackson, K. J. Allison, M. J. Natan, Langmuir 1996, 12, 810. [16] K. J. Klabunde, Y.-X. Li, A. Khaleel, in Nanophase Materials (Eds: G. C. Hadjipanayis, R. W. Siegel), Kluwer Academic, Dordrecht, The Nether- lands 1994, p. 757. One-Dimensional Silicon Chain Architecture: Molecular Dot, Rope, Octopus, and Toroid** By Kazuaki Furukawa,* Keisuke Ebata, and Michiya Fujiki A methodology for connecting functional polymer chains to a solid surface and controlling their structures is indispensable for molecular electronic device architecture. Recently, the structures of end-grafted polymers on a substrate surface were visualized [1,2] and single polymer dynamics were extensively studied [3] by atomic force microscopy (AFM). If the polymer were conductive or semiconductive, optoelectronic measure- ments would also be an attractive subject for fundamental studies of single-polymer electronics. [4] The structure of an isolated end-grafted polymer should re- flect the polymer chain rigidity. When the surface density is appropriately high and an end-grafted polymer can reach neighboring polymers, the end-grafted polymers are expected to affect each other by means of non-covalent interaction and form supramolecular structures. If we could control these structures by using conductive polymers, we could propose a molecular wiring methodology for complex molecular device architectures. This paper describes such supramolecular struc- tures formed by end-grafted one-dimensional silicon chains, together with single-molecule structures of an isolated end- grafted silicon chain. We used polysilane, a linear silicon catenated polymer pos- sessing organic substituents (Scheme 1), as a one-dimensional silicon chain. Polysilane exhibits such semiconducting proper- ties as photoconductivity, hole transport, and electrolumines- cence in its solid thin films, which are based on the delocaliza- tion of s-electrons forming Si±Si bonds. [5] Polysilane also exhibits an intense s±s* transition in the ultraviolet region, which is closely related to the conformation of the silicon main chain. We have found that the logarithmic molar absorp- tion coefficient per Si±Si bond, e [cm ±1 mol ±1 L], in polysilanes is proportional to their viscosity index, a, which is a scale for evaluating chain rigidity. [6] The experimentally determined a values for polysilanes range from 0.51 to 1.35, which includes flexible and semiflexible chains. We chose three polysilanes with different organic substituents (1, 2, and 3), and thus dif- Adv. Mater. 2000, 12, No. 14, July 19 Ó WILEY-VCH Verlag GmbH, D-69469 Weinheim,2000 0935-9648/00/1407-1033 $ 17.50+.50/0 1033 COMMUNICATIONS ± [*] Dr. K. Furukawa, Dr. K. Ebata, Dr. M. Fujiki NTT Basic Research Laboratories 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan) E-mail: furukawa@will.brl.ntt.co.jp [**] We thank Dr. Y. Y. Suzuki, Dr.M. Morita, Dr. H. Takayanagi, and Dr. N. Matsumoto for fruitful discussions.