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semiconductor, solid material whose electrical conductivity at room temperature is between that of a conductor and that of an insulator (see conduction; insulation). At high temperatures its conductivity approaches that of a metal, and at low temperatures it acts as an insulator. In a semiconductor there is a limited movement of electrons, depending upon the crystal structure of the material used. The substances first used for semiconductors were the elements germanium, silicon, and gray tin. It was found that the incorporation of certain impurities in them enhances their conductive properties. The impurities either add free electrons or create holes (electron deficiencies) in the crystal structures of the host substances by attracting electrons. Thus there are two types of semiconductor: the N-type (negative), in which the current carriers (electrons) are negative, and the P-type (positive), in which the positively charged holes move and carry the current. The process of adding these impurities is called doping; the impurities themselves are called dopants. Dopants that contribute mobile electrons are called donor impurities; those that cause holes to form are acceptor impurities. Undoped semiconductor material is called intrinsic semiconductor material. Certain chemical compounds, including gallium arsenide, indium antimonide, and aluminum phosphide are semiconductors. Semiconductors are used to produce such electronic devices as diodes, transistors, and computer memory devices. The field of solid-state physics includes the study of semiconductors. See also integrated circuit.
pharmacological and other agents that when injected into the body quickly and temporarily stimulate its physical and nervous activity.
Doping has been known since ancient times when it was used by cultists, shamans, and warriors in Africa, India, ancient Greece, Rome, and elsewhere. Beginning in the late 19th century doping became widespread in a number of countries as a means of increasing the speed of race horses. In the 20th century doping began to be used in sports in some capitalist countries. Studies have been published on the search for and use of dope in medicine, veterinary medicine, and so forth.
Among the agents that can be used as dope (depending on the specific nature of the sport or other activity) are sympathomimetic amines (amphetamine, methylamphetamine, ephedrine), central nervous system stimulants and analeptics (strychnine, transaminum, indopanum, leptamine), narcotics and pain relievers (morphine and its derivatives, opium), general stimulants (preparations of ginseng, Schizandra chinensis, and Rhaponticum carthamoides, and monoamine oxidase inhibitors), tranquilizers (Valium, Librium, Andaxin, Noxyronum), and ethyl alcohol in various mixtures.
The use of dope in sports makes conditions unequal, and it may do physical and mental harm to human beings. Many cases of poisoning of athletes are known abroad. Fatalities caused by taking dope have been recorded in international boxing and bicycling competitions. In some countries (for example, Belgium and Italy) where the use of dope is widespread, state laws forbidding it have been passed. Since the fight against dope is a matter of great moral, ethical, legal, and sports significance, the International Olympic Committee meeting in Lausanne on Dec. 20, 1967, decided to ban the use of dope in sports and to organize antidoping controls at international competitions. An athlete found using dope is disqualified.
V. A. SEMENOV, N. A. FROLOCHKINA and E. E. CHERKASOV