This book is an outcome of the NATO institute on surface modification which was held in Trevi, 1981. Surface modification and alloying by ion, electron or laser beams is proving to be one of the most burgeoning areas of materials science. The field covers such diverse areas as integrated circuit processing to fabricating wear and corrosion resistant surfaces on mechanical components. The common scientific questions of interest are the microstructures by the different energy deposition techniques. and associated physical properties produced The chapters constitute a critical review of the various subjects covered at Trevi. Each chapter author took responsibility for the overall review and used contributions from the many papers presented at the meeting; each participant gave a presentation. The contributors are listed at the start of each chapter. We took this approach to get some order in a large and diverse field. We are indebted to all the contributors, in particular the chapter authors for working the many papers into coherent packages; to Jim Mayer for hosting a workshop of chapter authors at Cornell and to Ian Bubb who did a sterling job in working over some of the manuscripts. Our special thanks are due to the text processing center at Bell Labs who took on the task of assembling the book. In particular Karen Lieb and Beverly Heravi typed the whole manuscript and had the entire book phototypeset using the Bell Laboratories UNIXβ’ system.