Auger electron spectroscopy (AES) is based on the Auger total secondary electron energy distribution, and an ion gun to process, which involves the core-level ionization of an atom with provide depth profiling capability. subsequent deexcitation occurring by an outer-level electron de The high surface sensitivity of Auger spectroscopy which dictates caying to fill the core hole. The excess energy is transferred to the need for an ultrahigh-vacuum system is due to the limited and causes the ejection of another electron, which is by definition mean free path of electrons in the 0-3000 e V kinetic energy an Auger electron. The Auger electron transition, denoted by range. The Auger peaks decay exponentially with overlayer cov the electron levels involved, is independent of the excitation erage, which is consistent with an exponential dependence of source and leaves the atom with a constant kinetic energy. The escape probability on the depth of the parent atom. A compila kinetic energy is given by the differences in binding energies for tion of data from a variety of sources has been used to generate the three levels (for example, EK-E L, - EL ) minus a correction 2 an escape depth curve which falls in the range of 5-30 A in the term for the work function and electron wave function relaxation. energy range from 0 to 3000 eV. The observed escape depth does When the Auger transition occurs within a few angstroms of the not show a strong dependence on the matrix.

In 1970 when I first seriously contemplated writing a book on electron spectroscopy, I recognized the impossibility of completely reaching my desired goals. First, the field was expanding (and still is) at such a rate that a definitive statement of the subject is not possible. The act of following the literature comprehensively and summarizing its essential content proved to be a diver gent series. On the other hand, the field has increased to such a size that violent changes in its basic makeup no longer occur with the frequency that was present in its early days. Furthermore, the excitement of electron spectro scopy lies in its many-faceted interrelationships. In the era of specialization, electron spectroscopy is an open-ended subject continually bringing together new aspects of science. I wished to discuss not just one type of electron spectro scopy, but as many as would be possible. The book as it stands concentrates its attention on x-ray photoelectron spectroscopy, but also presents the basis of Auger electron spectroscopy and uv photoelectron spectroscopy, as well as mentioning many of the other branches of the field. A large, many-author volume might be an answer to some of these problems. However, though anyone person possesses only a limited amount of expertise, I have always enjoyed books by a single author since what they lack in detailed knowledge they gain in a unified viewpoint. I hope the final product, though limited in its attainment of these goals, will still be of some merit.