Surfaces and Interfaces of Electronic Materials
Starting with the fundamentals of electrical measurements on semiconductor interfaces, it then describes the importance of controlling macroscopic electrical properties by atomic-scale techniques. Subsequent chapters present the wide range of surface and interface techniques available to characterize electronic, optical, chemical, and structural properties of electronic materials, including semiconductors, insulators, nanostructures, and organics. The essential physics and chemistry underlying each technique is described in sufficient depth with references to the most authoritative sources for more exhaustive discussions, while numerous examples are provided throughout to illustrate the applications of each technique.
With its general reading lists, extensive citations to the text, and problem sets appended to all chapters, this is ideal for students of electrical engineering, physics and materials science. It equally serves as a reference for physicists, material science and electrical and electronic engineers involved in surface and interface science, semiconductor processing, and device modeling and design.
This is a coproduction of Wiley and IEEE
Free solutions manual available for lecturers at www.wiley-vch.de/supplements/
Leonard Brillson is a professor of Electrical & Computer Engineering, Physics, and Center for Materials Research Scholar at The Ohio State University in Columbus, OH, USA. Prior to that, he was director of Xerox Corporation's Materials Research Laboratory and had responsibility for Xerox's long-range physical science and technology programs at the company's research headquarters in Rochester, N.Y. He is a Fellow of IEEE, AAAS, AVS, and APS, and a former Governing Board member of the American Institute of Physics. He has authored over 300 scientific publications and received numerous scientific awards, including the AVS Gaede-Langmuir Award.
Surfaces and Interfaces of Electronic Materials
1.1 Surface and Interfaces in Everyday Life
Surfaces and interfaces are all around us. Their properties are important in our daily lives and are basic to many of today's advanced technologies. This is particularly true for the semiconductor materials that are used throughout modern electronics. The aim of this book is to present the physical principles underlying the electronic, chemical, and structural properties of semiconductor interfaces and the techniques available to characterize them. Surfaces and interfaces are a cross-disciplinary field of science and engineering. As such, this book emphasizes the principles common to physics, electrical engineering, materials science, and chemistry as well as the links between fundamental and practical issues.
Surfaces and interfaces play a central role in numerous everyday phenomena. These include (i) triboelectricity , the transfer of charge between two materials brought into contact - such as the static electricity built up on a comb after combing one's hair; (ii) corrosion , the oxidation of structural materials used in, for example, buildings, bridges, and aircraft; (iii) passivation , the prevention of such chemical or biological processes using special protective layers; (iv) colloid chemistry , the wetting of surfaces and the dispersion of particles within fluids as emulsions or colloids, for example, paints and time-release capsule medicines; (v) tribology , the friction between sliding objects in contact and their interface lubrication; (vi) cleaning and chemical etching , the removal of surface layers or adsorbed species; (vii) catalysis , the reduction in energetic barriers to speed up or improve the yield of chemical reactions, for example, refining oil or burning coal; and (viii) optical interference , the rainbow of colors reflected off thin oil layers or the internal reflection of light between stacks of materials only a few wavelengths of light thick. On a much larger scale are (ix) electromagnetic interfaces between the earth's atmospheric layers that bounce short-wave radio signals around the world and that alter the reflection or absorption of sunlight contributing to global warming.
1.2 Surfaces and Interfaces in Electronics Technology
Surfaces and interfaces are fundamental to microelectronics. One of the most important microelectronic devices is the transistor, all functions of which depend on the boundaries between electronic materials. Figure 1.1 illustrates the three aspects of this dependence. Here, current passes from a source metal to a drain metal through a semiconductor, in this case, silicon (Si). A gate metal between the source and the drain is used to apply voltages that attract or repel the charge carriers involved in the current flow. The result is control or "gating" of the current flow by this third electrode. This basic device element is at the heart of the microelectronics industry.
Figure 1.1 Source - gate - drain structure of a silicon transistor.
The surfaces and interfaces are the key to the transistor's operation, shown in Figure 1.1 . Thus, the contact between the metal and Si is a metal silicide. Barriers can form between metals and semiconductors that impede charge movement and introduce voltage drops across their interfaces. This barrier formation is a central topic of this book. Microelectronics researchers found that promoting a chemical reaction to form silicides, such as TiSi2 between Ti and Si, reduces such transport barriers and the contact resistivity ρc at these metal - semiconductor interfaces. This is illustrated, for example, in Figure 1.2a . Such interfacial silicide layers form low resistance, planar interfaces that can be integrated into the manufacturing