LARK-HOROVITZ, KARL

(b. Vienna, Austria, 20 July 1892; d West Lafayette, Indiana, 14 April 1958)

physics.

Karl Lark-Horovitz was a son of Moritz Horovitz and Adelle Hofmann. His father was a noted dermatologist and a man of wide-ranging scholarly interests, including botany and classical poetry. Karl Horovitz attended a humanistic high school and entered the University of Vienna in 1911 to study chemistry, physiology, physics, and pre-Socratic philosophy. During World War I he served as an officer in the signal corps of the Austrian Army, acquiring practical experience with the use of crystal detectors. In 1919 he returned to his studies and later that year received his Ph.D. in physics from the University of Vienna, where he stayed to teach and conduct research until 1925. In 1916 he married Betty Friedländer, a printmaker whose pseudonym was Lark, and in 1926 formally changed his family name to Lark-Horovitz.

From the beginning of his scientific career Karl Lark-Horovitz was attracted by newly opened fields of research and, in particular, by interdisciplinary subjects. One of his first publications, in 1914, dealt with the historical development of the principle of relativity, and he always remained interested in the history of science. His other early investigations included the use of radioactive materials in the study of crystals, the physics of image formation by the human eye, and the electrochemistry of glasses.

In 1925 Lark-Horovitz was awarded an International Research Council Fellowship by the Rockefeller Foundation. He first went to the University of Toronto to conduct X-ray diffraction studies at low temperatures and subsequently spent some time at the University of Chicago (1926), Rockefeller Institute (1926–1927), and Stanford University (1927– 1928). Invited to Purdue University in the spring of 1928 to deliver a series of lectures, Lark-Horovitz returned to West Lafayette in the fall of 1929 to assume a permanent position at Purdue as the director of the Physical Laboratory. In 1932 he was appointed head of the department, a position he held until his death.

During his tenure at Purdue, Lark-Horovitz was very actively involved in a number of diverse activities that can roughly be divided into four areas. Prior to World War II, he conducted research in a variety of subfields of physics, including X rays, physics of surfaces, and, from 1936 to 1942, nuclear physics (a small cyclotron was constructed in 1938); he created at Purdue a highly regarded graduate program in physics; he actively participated in the creation, development, and fruition of the American Association for the Advancement of Science (AAAS) Cooperative Committee on the Teaching of Science and Mathematics; and he established at Purdue one of the leading centers of solid-state physics in the United States.

It was in this last field of research, in particular in the study of semiconductors, that Lark-Horovitz made his most important contributions to physics. His interest in solid-state physics was prompted by the wartime mobilization of science for national defense. The Radiation Laboratory, established in 1940 at the Massachusetts Institute of Technology to develop the microwave radar for the military, was seeking in early 1942 laboratories that would assume subcontracts to investigate various technical aspects of the new device. The contract LarkHorovitz brought to Purdue was concerned with the development of crystal rectifiers, and his experience as a chemist led him to the choice of germanium as a material for investigation.

At the time the Purdue group started its wartime project, very little was known about the electrical properties of germanium. Proper methods of purification and controlled doping had first to be developed, and once relatively pure samples of the material became available, Lark-Horovitz and his collaborators pursued research along two lines. First of all, the measurements of the resistivity, Hall effect, and thermoelectric power provided the basis for seeking answers concerning the mechanisms of electric conductivity in germanium. Results of these experiments led Lark-Horovitz to the conclusion that germanium was an intrinsic semiconductor.

Thesecond line of research was aimed directly at the production of operational crystal rectifiers intended for use as microwave radar detectors. Lark-Horovitz and his group developed a high-back-voltage germanium diode, a successful device that found many applications, but went into mass production too late to be used during the war.

A sense of urgency and strong emphasis on application prevented Lark-Horovitz from following up, with appropriate thoroughness, on some of the discoveries made at Purdue while working on the germanium wartime project. Some observed phenomena, such as the spreading resistance anomaly, or negative resistance, as it became clear only a few years later, anticipated the discovery of the transistor effect made by a team of Bell Labs researchers in 1947.

After the end of the war, Lark-Horovitz’s interests turned temporarily away from solid-state physics, but after the development of the transistor, he resumed his research in this area with new vigor. His major contribution from this period was his work on the impact of radiation on semiconductors, which threw much light on the mechanism of production and effect of lattice defects in crystals.

Lark-Horovitz was very actively involved in the work of the AAAS. He was general secretary from 1947 to 1949 and a member of the editorial board from 1949 to the time of his death. He was an original member of the AAAS Cooperative Committee on the Teaching of Science and Mathematics, and chairman of the committee from 1945 to 1950.

Karl Lark-Horovitz became a naturalized American citizen in 1936. His children, Caroline Betty and Karl Gordon (who used the family name Lark), were born in 1929 and 1930, respectively. He died of a heart attack on 14 April 1958, while at work in his office at Purdue.

BIBLIOGRAPHY

I. Original Works. A bibiography of Lark-Horovitz’ research publications is in Vivian Annabelle Johnson, Men of Physics: Karl Lark-Horovitz, Pioneer in Solid State Physics (Oxford and New York, 1969). The list of his scholarly contributions consists of eighty-three entries, and a selection of nineteen of his most important works in physics is reprinted in the book.

II. Secondary Literature. Johnson’s book includes a biography of Karl Lark-Horovitz (46 pages long). Brief obituaries appeared in Science, 127 (1958), 1487–1488, by Hubert M. James, and in Proceedings of the Indiana Academy of Sciences, 68 (1958), 35–37.

Kris Szymborski