The International Symposium on the Science and Technology of Mesoscopic Structures was held at Shin-Kohkaido in Nara from November 6-8, 1991. The symposium was sponsored by the International Institute for Advanced Study and partly by Nara Prefecture, Nara City, Nara Convention Bureau, and the Ministry of Education, Science and Culture of Japan, as well as industrial organizations. We would like to acknowledge the support of the symposium by these or ganizations. The scope of the symposium was planned by the organizing committee to cover outstanding contributors in the fields of (1) ballistic transport, (2) electron wave guides and interference effects, (3) quantum confinement effects, (4) tunneling phenomena, (5) optical nonlinearity, and (6) fabrication technology of meso scopic structures. Twenty-six invited speakers were selected from the United States, Europe, and Japan. In addition twenty-four contributed papers were accepted for presentation at the poster session. These papers are included in the proceedings. We are grateful to the organizing committee, Ms. Y oshiko Kusaki of the Inter national Institute for Advanced Study for the secretarial service, and Dr. Nobuya Mori, Osaka University, for his scientific cooperation. Thanks are also due to the authors and the participants for their contributions to a successful symposium."

The technique of ion implantation has become a very useful and stable technique in the field of semiconductor device fabrication. This use of ion implantation is being adopted by industry. Another important application is the fundamental study of the physical properties of materials. The First Conference on Ion Implantation in Semiconductors was held at Thousand Oaks, California in 1970. The second conference in this series was held at Garmish-Partenkirchen, Germany, in 1971. At the third conference, which convened at Yorktown Heights, New York in 1973, the emphasis was broadened to include metals and insulators as well as semiconductors. This scope of the conference was still accepted at the fourth conference which was held at Osaka, Japan, in 1974. A huge number of papers had been submitted to this conference. All papers which were presented at the Fourth International Conference on Ion Implantation in Semiconductors and Other Materials are included in this proceedings. The success of this conference was due to technical presentations and discussions of 224 participants from 14 countries as well as to financial support from many companies in Japan. On behalf of the committee, I wish to thank the authors for their excellent papers and the sponsors for their financial support. The International Committee responsible for advising this conference consisted of B.L. Crowder, J.A. Davies, G. Dearna1ey, F.H. Eisen, Ph. G1otin, T. Itoh, A.U. MacRae, J.W. Mayer, S. Namba, I. Ruge, and F.L. Vook.