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NEW BOOKS
Ergebnisse der exakten Naturwissenschaften. Sonderabdruck aus Bd X I I I . Uber den ausseren Photoeffekt a n adsorbierten Schichten. By R. SUnRmmN. 23 x 16 cm.; 74 pp. Berlin: J. Springer, 1934. Obtainable only in complete issue. Price: unbound, 28 RM; bound, 29.40 RM. I n this section of the Ergebnisse Dr. Suhrmann has given a survey of work on measurements of the external photoeffect for adsorbed layers. The outlook of the survey is for the most part experimental, and apparatus and results are illustrated in sixty-four diagrams. Until very recently the necessity for a really first class vacuum technique in work of this kind was not universally appreciated. As a result much of the older work is of little value. Dr. Suhrmann, however, steers a careful course through the maze of results available. After a preliminary historical survey he deals very briefly with the fundamental photoelectric laws. Many aspects of adsorbed layer problems are dealt with in the main section of the report, and of these we may mention the influence of gases and of outgassing technique on the photoelectric properties of the layers, the properties of adsorbed metal films, such as cesium on tungsten, the effects of temperature and of the electric field. Over two hundred references to original papers are appended. J. T. RANDALL. Ergebnisse der exakten. Naturwissenschajten. Sonderabdruck aus Bd X I I I . Elektrische Leitfah.igkeit elektronischer Halbleiter. By B. GUDDEN.23 x 16 cm.; 33 pp. Berlin: J. Springer, 1934. Obtainable only in complete issue. Price: unbound, 28 RM; bound, 29.40 RM. Semiconductors have long been one of the mysteries of physics, but during the last year or two the general advances of quantum mechanics have gone far towards sketching in the main outlines of the fundamental conducting mechanism in these bodies. These theoretical advances are for the most part due to A. H. Wilson and R. H. Fowler, but a great deal of fundamental experimental work has been done by Gudden and Pohl from 1920 onwards. The work of greatest importance has been done on single crystals, such as zinc blende, while much of practical import has been carried out on copper oxide, selenium, and the associated rectifying contacts. The general division of work falls naturally into two classes. On the one hand there are single crystals, on the other powdered crystals, and both these types have been investigated with and without the stimulation of incident light. I n the present reprint Professor Gudden has not attempted an exhaustive survey of the subject, but all who wish to obtain a good idea of the experimental results and their interpretation will do well to consult it, for it is written in a clear and simple way and is confined to main issues. The main items dealt with in the survey are: the existence of ionic or electronic conduction in semiconductors; the validity of Ohm’s Law and the question of specific conductivity; the effect of temperature on the conductivity; photoelectric effects; and an outline of modern theory. A point of interest to chemists is the fact that the physical properties of semiconductors are largely dependent on impurities which may frequently be difficult or impossible to detect by ordinary chemical means. J. T. RANDALL.
