Abram Fedorovich Ioffe (29.10.1880-14.10.1960) was a Soviet physicist, an academician (1920; corresponding member 1918) and vice-president (1926—29, 1942 — 45). He was born in the town of Romny. He graduated from the St Petersburg Technological Institute (1902). In 1903 —06 he was a trainee and then an assistant in W. Röntgen's laboratory at the University of Munich. In 1906 he began to work at the St Petersburg Polytechnic Institute. In 1913 —48 he was professor and in 1919 — 48 dean (with interruptions) of the institute's faculty of physics and mechanics. In 1918, on Ioffe's initiative, a physico-technical department was created at the Roentgenological and Radiological Institute (reorganised in 1923 into the Leningrad Physico-Technical Institute), and in 1919 a faculty of physics and mechanics at the Polytechnic Institute. On the basis of these centres of physical science in the USSR an extensive network of research institutes of physics was created in the years that followed (physico-technical institutes in Kharkov, Dnepropetrovsk, Sverdlovsk and Tomsk, the Institute of Chemical Physics, the Electrophysical Institute and others). Until 1951 he was director of the Leningrad Physico-Technical Institute of the USSR Academy of Sciences, in 1952-55 of the Semiconductor Laboratory of the USSR Academy of Sciences and from 1955 of the Institute of Semiconductors of the USSR Academy of Sciences (in 1932 —60 he was also director of the Agrophysical Institute).
His research concerned solid-state physics and general questions of physics. He made a particularly significant contribution to the physics and technology of semiconductors. Already in his doctoral dissertation (1905) he showed his mastery as an experimenter and settled the question, important at that time, of the elastic aftereffect in crystals. In 1913 he carried out a series of studies on measuring the charge of the electron in the external photoelectric effect and proved the statistical nature of the elementary photoelectric effect. He proved experimentally (1916) the existence of ionic conductivity in crystals — the passage of ions through the lattice of an ionic crystal under the action of a field. Ioffe's studies of plastic deformation by the X-ray method became classics. Studying the mechanical properties of crystals, he found that the manner in which crystals fracture at a given temperature is determined by the relation between the yield point and the ultimate strength. This discovery was of great importance for technology. He explained the real strength of crystals (1922). He was the first to clear up the question of the so-called electrical anomalies of quartz, showing that they are connected with the formation of space charges inside the crystal. He established that slight impurities strongly affect the electrical conductivity of dielectrics, and developed methods of purifying crystals. The work of Ioffe and his collaborators on the electric strength of thin layers of dielectrics culminated in the creation of new electrical engineering materials and in the development of methods of eliminating overvoltages.
At the beginning of the 1930s Ioffe's scientific interests became concentrated in the field of semiconductor physics, where he and his collaborators discovered a number of phenomena important for technical application. Having studied a number of semiconductors, he found that their electrical properties are strongly affected by impurities; in particular, it was established that impurities change the conductivity and the sign of the current carriers over a wide range. He formulated a new idea about the nature of the semiconducting properties of a large group of intermetallic alloys — the daltonides — and studied them in detail. This opened the way to the creation of semiconductor materials whose properties can be varied within wide limits. Another important problem of semiconductor physics with which Ioffe dealt was that of rectification. At the end of the 1930s he formulated a picture of the mechanism of rectification which in its general outlines is still accepted today and which contributed considerably to the success of the industrial manufacture of diodes. Ioffe also made a large contribution to the problem of using the thermoelectric and photoelectric properties of semiconductors to convert heat and light energy into electrical energy. He developed a theory of thermoelectric generators and thermoelectric refrigerators and put forward the idea of plasma thermoelectricity. On the very eve of the war he created a thallium sulfide photocell with an efficiency of more than 1%.
He created a large school of physicists, many of whom themselves became the founders of schools of their own (A. P. Alexandrov, A. I. Alikhanov, L. A. Artsimovich, P. L. Kapitza, I. K. Kikoin, G. V. Kurdyumov, I. V. Kurchatov, P. I. Lukirsky, N. N. Semenov, Yu. B. Khariton, Ya. I. Frenkel, A. K. Valter, A. F. Valter, Ya. G. Dorfman, A. I. Leipunsky, K. D. Sinelnikov, V. P. Zhuze, A. R. Regel, L. S. Stilbans and others).
Lenin Prize (1961, posthumously). Hero of Socialist Labour (1955). USSR State Prize (1942). A member of many academies of sciences and scientific societies. In 1924—30 he was editor-in-chief of the “Journal of Applied Physics”, in 1931—38 of the “Journal of Experimental and Theoretical Physics” and in 1931—59 of the “Journal of Technical Physics”. The Leningrad Physico-Technical Institute of the USSR Academy of Sciences bears Ioffe's name.