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Walter Brattain (Brattain), Walter

( The American physicist, Nobel Prize in Physics, 1956)

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Biography Walter Brattain (Brattain), Walter
February 10, 1902, Mr.. - October 13, 1987
The American physicist Walter Houser Brattain was born in g. Amoy (Xiamen) in the south-east China. Son of Ross P. Brattain, teachers, private school for Chinese children, and Ottilie (Hauser), Walter Brattain, he was the eldest of five children. In early childhood, B. family returned to Washington, where grew older Brattain, and settled in Tonaskete. His father bought a plot of land, became the owner of the cattle ranch and mill. The boy attended school in Tonaskete, then went to Whiteman College in Walla Balla, choosing as the main disciplines of mathematics and physics. He became a bachelor in 1924, received a master's degree in physics from the University of Oregon in 1926. and a doctorate in physics from the University of Minnesota in 1929. Although B. enjoyed life on the ranch, in the bosom of nature, farm labor, he hated. 'Walking in the dust for three horses and a harrow that's what made me a physicist' - he would say later.
As part of his doctoral program B. spent 1928/29 academic year at the National Bureau of Standards U.S., where he worked to increase the accuracy of measurements of time and frequency fluctuations, and also helped develop a portable generator with temperature control. In 1929, Mr.. he joined the laboratory of 'Bell Telephone' as a physics researcher and worked there until retirement in 1967, then returned to Whiteman College to teach physics and conduct research on living cells.
. The first 7 years in the laboratories 'Bell' B
. study phenomena, . as the influence of adsorption films on the electron emission by hot surfaces, . electronic collisions in mercury vapor, . engaged magnetometers, . infrared phenomena and Oscillator While primarily an electronic amplifying device was a three-electrode vacuum tube (triode), . invented by Lee de Forest in 1907,
. At the end of XIX century. Thomas Edison, dealing with the problems of the electric light, found that between the hot filament and the second electrode, if placed in a hermetic flask, pump out the air and connect the battery, an electric current. Thus was born the two-electrode tube (diode) Later physicists showed that the filament emits electrons, which carry a negative charge and are attracted to the positive electrode. Since the diodes conduct current in one direction, they were used as rectifiers, which turn a variable that changes the direction of current in the constant current flowing in one direction only. De Forest put in a wire mesh (grid) between the electron emitter (cathode) and the positive electrode (anode) A small change in voltage on the grid leads to large changes in current, . current through the grid between the cathode and anode, . thereby allowing you to amplify the signal, . attached to the grid,
. The high temperature needed for electron emission, reducing the lifetime of the cathode and the spoils of electron tubes. B. found that some of the thin cathode coatings provide satisfactory emissions at lower temperatures, adding to and prolonging the lifespan of the lamp.
When in 1936. in the laboratory 'Bell' came William Shockley, . He quickly joined in the investigation of material properties, . called semiconductors His goal was to replace vacuum tubes devices made of hard materials, . that would be less than the size, . less fragile and more energy-efficient electrical conductivity of semiconductors occupies an intermediate position between the electrical conductors (mainly metals) and insulators, and varies greatly in the presence of even small amounts of impurities,
. In the first semiconductor radios used by the contact between the turns of fine wire (rounded end) and a piece of the mineral galena (semiconductor) for the detection of small signals from the received radio antenna. Exploring semiconductors, B. and Shockley were looking for material that could both detect and enhance the signals Their studies were interrupted by the war. From 1942 to 1945. they worked in the Department of War Studies at Columbia University, where he engaged in the application of scientific developments in anti-submarine warfare. Shockley left the research is still early to work on radar.
When after the war, B. Shockley and returned to the laboratory 'Bell', they were joined by physicist John Bardeen. In this Commonwealth B. served as the experimenter, which determines the properties and behavior of the investigated materials and devices. Shockley has put forward a theoretical assumption that the current acting on the electric field of the applied voltage, the amplifier can be obtained with the field influence. This field should act similarly to the field, which occurs on the grid triode amplifier. Group has created a lot of devices to test the theory of Shockley, but all to no avail.
Here Bardin got the idea that the field can not penetrate the semiconductor layer due to electrons located on its surface. This has led to intensive studies of surface effects. Semiconductor surfaces were exposed to light, heat, cold, they are wetting liquid (insulating and conducting) and covered with metal films. In 1947, when a group of deeply understand the behavior of a semiconductor surface, B. and Bardeen constructed device, which first manifested what later became known as the transistor effect. This device, called point-contact transistor, consisted of a germanium crystal containing a small concentration of impurities. On one side of the crystal placed two pins of gold foil, on the other hand was the third contact. Positive voltage was applied between the first gold contact (emitter) and the third contact (base), and a negative voltage - between the second gold contact (collector) and base. Signal fed to the emitter, influenced the current in the circuit of the collector - base. Although this device amplifies the signal, as was intended, but the principle of his work could not find a satisfactory explanation, prompting a new round of research.
. Although the theory of semiconductors to a large extent already been developed with the help of quantum mechanics, the predictions of this theory has not yet been adequately quantified in the experiment
. Atoms in crystals are held together by electrons, the most weakly associated with their nuclei. In a perfect crystal of communication, as they say, 'saturated' or 'filled'. Electrons are hard to tear, they barely move, which leads to a very high electrical resistance. Such a crystal is a insulator. However, inclusions of foreign atoms, which are not well suited to this structure, lead to the emergence of a surplus of electrons that can participate in the electric current, or a deficit of electrons, known as the 'hole'. In the mathematical model of the hole are moving, as if they were positively charged electrons, albeit with different speed. In fact, the holes are the places, . abandoned electrons, . and, . hence, . everything looks, . as if the holes are moving in the opposite direction, . while the electrons are moving forward, . filling the previously empty seats and forming a new hole there, . where they left,
. It turns out that for an explanation of the transistor must take into account the complex interaction of impurities of various types and concentrations, the local nature of contacts between different materials and the contribution which gives a current of both electrons and holes. The important role of the holes was not sufficiently predict in advance.
. Shockley predicted that the device can be improved by replacing metallopoluprovodnikovye contacts with improved contacts between the different types of semiconductors, one of which is dominated by excess electrons (n-type), and another hole (p-type)
. A successful model, called the junction transistor was made in 1950, Mr.. It consisted of a thin layer of p-type, location - like a sandwich - between two layers of n-type metal contacts in each layer. This device worked exactly as predicted by Shockley. Planar transistors have been widely used instead of point-contact types, because they were easier to make and they work better. The early idea of Shockley, the transistor with field effect, something quite difficult to implement, since among the available material was not suitable. A working field-effect transistor was built on the basis of the silicon crystal, when the methods of cultivation and purification of crystals sufficiently far advanced.
. Like the electron tubes, transistors allow a small current flowing in one circuit to control a much larger current flowing in another circuit
. Transistors Tubes quickly drove everywhere, except in cases where you want to manage a very large capacity, such as in broadcasting or in industrial radio frequency heating installations. Bipolar transistors are typically used where you want high speed, as well as in high-frequency units, where there is no urgent need to use electron tubes. Field effect transistors - is the main type of transistors used in electronic devices. It is easier to manufacture, and the energy it consumes even less than the bipolar transistor. While some of the transistors are made of germanium, most of them made of silicon, which is more resistant to high temperatures. With further development of technology made it possible to have a single piece of silicon to one million transistors, and this number continues to grow. Such silicon blocks are the basis for the rapid development of modern computers, communications and management.
Nobel Prize in Physics for 1956. B. shared with Bardeen and Shockley. They were awarded 'for the study of semiconductors and the discovery of the transistor effect'. In his Nobel lecture, 'Surface properties of semiconductors' ( "Surface Properties of Semiconductors") B. stressed the importance of surfaces, 'where there are many, if not most, interesting and useful phenomena. In electronics, with the majority, if not all, elements of the contour associated non-equilibrium phenomena occurring on surfaces'.
. Further investigation B., . on the properties of semiconductors and their surfaces, . were extremely important for the field-effect transistors, . are very sensitive to surface defects, . for solar, . properties are determined by the electrical properties of the surface.,
. In 1935
. B. married Keren Gilmore, engage in physical chemistry, they had a son. In 1957. She died a year later B. married Emma Jane Kirsch Miller. B. known for his direct and sincere. Among his hobbies - golf, fishing and reading books.
Among other awards B. include medal Stuart Ballantyne Franklinovskogo Institute (1952), Mr. John Scott Award. Philadelphia (1955) and an honorary award graduates of the University of Oregon (1976). He has five honorary doctorates, . is a member of the National Academy of Sciences and the Honorable Society of Inventors, . and is a member of the American Academy of Arts and Sciences, . American Association for the Advancement of Science and the American Physical Society.,


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