Pioneering in Electronics
Chapter Eleven - The Great Transition: Vacuum to Solid
When the electron tube replaced the crystal as the standard detector of radio waves in the early 1920s, it would have taken a gift of prophecy bordering on the supernatural to foresee the triumphant return of the crystal some three decades later as a pillar of the new electronic science. With some allowance for overstatement, this is precisely what happened—thanks to a profound change in the technological climate during the intervening years.
Every revolution tends to reach back into the past in some important respect to reintroduce an old value or an old device in a new context. The role of the crystal in the electronics revolution of the mid-20th century is a classic illustration.
The ability of certain crystal substances, such as galena and pyrites, to rectify—i.e., to change an alternating current into a pulsating direct current—had been recognized since the early 1870s. With the advent of radio, pioneers in the art turned to this phenomenon as a potentially useful means for detecting radio waves. The happy result is familiar to all radio enthusiasts of the early 1920s and to all amateurs who have since built and operated their own crystal sets. The crystal element in the majority of these cases was galena, a metallic (p. 278) sulfide. But it was also known during these early years that there were other substances with similar ability to rectify—selenium, for example, and silicon.
Even after their replacement by the versatile three-element electron tube for standard radio wave detection, crystals continued to play a useful though subordinate role in electronics as rectifiers in the highest frequency ranges. At the same time, additional materials were found to have a similar rectifying ability—among them the element germanium. Then came World War II, with its heavy demands upon electronic technology. Under wartime pressure, the silicon crystal came into its own as a superior detector in microwave radar systems. Germanium, too, became the object of heightened interest for generally similar application. In addition, reliance upon natural crystals gave way to new methods for syn\thesizing and purifying both germanium and silicon in useful crystalline form.
This was an evolution in which useful application ran some distance ahead of basic knowledge. During the early years of radio and until around 1930, virtually nothing was known of the reasons why the crystals behaved as they did. Gradually, however, fundamental research began to fill in the gaps by exploring and explaining the phenomenon of conduction and the nature of conducting materials. Through the 1930s and into World War II, physicists in Germany, England, Russia, and the United States developed a clear conception of semiconduction, a property of certain materials that are neither good insulators nor good conductors. In this category of semiconductors lay the germanium, (p. 279) silicon and other crystals whose usefulness as rectifiers already had become apparent.
By the beginning of the postwar era, semiconductors had become the center of major interest in basic research. Studies of the crystal detector were in progress in many laboratories, particularly those of Purdue University, the University of Pennsylvania, and Bell Telephone. A point of specific attention was the interesting possibility of a three-element crystal device that might not only rectify, but perform amplifying functions as well—an ability belonging at this time only to the electron tube.
From this background came the development that perhaps best symbolizes the revolution in electronics. On July 1, 1948, Bell Telephone Laboratories announced a new three-element semiconductor amplifier called the transistor, developed by William Shockley, John Bardeen, and W. H. Brattain.
In the new transistor, a tiny crystal of germanium was associated with two contacts corresponding to the cathode and anode of the electron tube. The movement of electrons within the crystal between these two contacts was controlled by a small voltage applied through a third element, in a manner analogous to that of the grid in the three-element tube. In this way, it became possible to achieve with extreme economy of power in a small solid-state device the amplifying, oscillating and detecting functions basic to all electronic circuits.
The invention, whose importance was recognized by a Nobel Prize award to the three Bell scientists, launched a major research and development program throughout the electronic industry. The (p. 280) result of this broad effort, in which the scientists of RCA were to play a role of fundamental importance, was the establishment of the transistor as a new basic building block of electronic devices and systems of unprecedented compactness and versatility. In this sense, the transistor was the keystone in a solid-state revolution overtaking all of electronic science. Before exploring the RCA contribution to transistor development, however, it may be useful to look at some other principal aspects of this great change, including the intensification of basic research in order to reinforce the processes of discovery and development.
What is solid-state electronics? [Humboldt W.] Leverenz recently described it as “the utilization of electrons moving within solids, and even electrons that remain localized within a given atom in a solid.” This is in contrast to conventional vacuum-tube electronics, in which use is made of free electrons boiled from a hot cathode into a vacuum, where they are controlled to perform many useful functions. For a number of electronic applications, the potential advantage of solid-state methods is apparent in the definition. First, controlling electrons within a material is likely to require far less power than does the process of heating a cathode to the point where electrons are knocked out of the cathode material. Second, elimination of the need for a vacuum in which to manipulate electrons can reduce drastically the size and complexity of an electronic system or device.
Before these and other advantages could be realized, however, it was necessary to gain through basic research a better understanding of the so-called electronically active materials and how they function. With the steady increase in such understanding (p. 281) during recent years has come an ability to induce entirely new electronic effects, impossible to achieve by any previous methods.
As we have seen, performing useful tricks with electrons remaining within a solid material was not a new principle that came to light suddenly in the postwar years. The extensive use of crystal detectors was one earlier example. Another, within RCA itself, was the extensive prewar study and use of phosphors suitable for television and radar. These demonstrated yet another important solid-state phenomenon—the emission of light from a material bombarded by an electron beam.
During the war, still another solid-state technique had been studied and developed in useful form in a new class of magnetic materials known as ferrites, ceramic-like substances comprising a mixture of iron, oxygen and another metal in an appropriate structure. At the time, relatively little was known of these materials beyond the fact that they permitted major improvements in radio frequency cores and exhibited highly interesting and controllable magnetic properties.
Following Engstrom’s determination upon a course of long-range basic research for RCA Laboratories at the end of the war, a number of fundamental studies were started at Princeton relating both to materials and to presently or potentially useful effects. A notable example in the early postwar era was the pioneering work of W. D. Hershberger in the absorption of microwaves in gases, a phenomenon that offered promise of precise frequency stabilization for microwave communications. (p. 282)
Earlier basic work by university scientists in this field had led to the discovery and measurement of an interesting effect: i.e., the unfailing tendency of ammonia gas under high pressure to absorb microwaves over a broad range of frequencies. Pursuing the subject at RCA Laboratories with a research team including L. E. Norton, Elizabeth Bush, George W. Leck and others, Hershberger discovered and measured similar microwave absorption characteristics in a number of different gases. He determined that at lower pressures, the absorption occurred in precise and sometimes predictable narrow frequency bands at various points in the spectrum. He further determined the relationships among the degree and frequency of absorption, the nature of the gas, and the pressure under which the gas was maintained.
The work of Hershberger and his associates attracted wide interest and led to similar research programs by university and industry scientists elsewhere, resulting in a general advance in the development of microwave spectroscopy as a new analytical technique in the study of matter. A further result of the work at RCA was Hershberger’s development of experimental frequency stabilization methods of high precision for microwave systems, although these techniques were superseded by other advances in microwave technology before they were put to extensive use.
An important part of the expanding basic research at the David Sarnoff Research Center following the war related to phosphors and ferrites, and to the nature of such useful phenomena as thermionic, secondary and photo-emission, as employed in (p. 283) electron tubes. In connection with this work, complex research tools were added to the physical plant, emphasizing the management determination to back up the long-range effort with the best possible laboratory facilities.
Among the early results of the basic program were the development of a practical theory of phosphor constitution and performance by Leverenz and his associates, and the synthesis and study of many new types of ferrite materials by Robert L. Harvey, Imre J. Hegyi and others. The ferrite program produced immediate as well as long-range benefits. Experimental applications worked out in a program under [Wendell] Carlson led directly to a ferrite production program in the RCA Victor Division at Camden. By the end of 1949, some 10,000 ferrite deflection-yoke units were being turned out each week for television receivers. It was the advent of the new magnetic materials with their superior properties for this application that permitted the rapid postwar progress in development of shorter tubes with larger picture area.
The studies of electron emission fell to a group of physicists under L. P. Smith and [Dwight O.] North. An early and direct offshoot of this program was a monumental study of oxide cathodes, conducted over a five-year period by[Leon S.] Nergaard, [Henry] DeVore, and [R. L.] Matheson. Their findings, wrapped in a detailed report in 1952, were of lasting importance to electron tube technology in general.
During the first three postwar years, the study of materials and their possible applications formed an appreciable but far from dominant part of the research program at Princeton. It was (p. 284) evident, however, that the field would expand soon and rapidly. Pointing to this likelihood in a note to the corporate management in 1947, Engstrom stated that “this new science is unfolding, and we plan to have a full part in its development.”
The Program Is Transistorized
The Bell announcement of the transistor served as the catalyst in this situation. The immediate importance of the new device was evident to the RCA research staff. As E. W. Herold observed subsequently in a paper before the American Institute of Metals:
The first transistor was a long step toward an effective solid-state amplifier, but intensive research and development were required to turn the first rudimentary type into a reliable and versatile device suitable for application in electronic circuits. The fact that this evolution occurred within a remarkably few years is a tribute to the research organizations of the electronics industry. A substantial share of the credit must go, too, to the RCA research and engineering staffs at Princeton and Harrison, for a series of outstanding basic contributions to the new transistor technology.
The scope of RCA’s original transistor work is broad enough to deserve several books in itself. One such book has, in fact, been published by RCA REVIEW under the title Transistors I, (p. 285) describing some of the later contributions in the RCA research and development effort. The program represented in the papers comprising the book called for a combination of teamwork and ingenuity comparable to that applied to the color television project.
More than a score of research staff members at Princeton and an equal number of engineering specialists at Harrison and Camden were involved in the transistor program during the years from 1948 through 1954. The program itself ranged across a broad field from basic research in semiconductor phenomena to the design of new circuits employing transistors. It embraced the study and development of advanced production techniques, an area in which the transistor presented a host of complex problems of standardization and large-scale manufacture.
The first operating RCA transistor was built at Princeton by Herold and Jerome Kurshan in the summer of 1948, and further units were produced rapidly for experimental use. Initially, the work centered upon the type known as the point-contact transistor, in which two fine wire contacts touch the surface of a wafer of germanium to which is connected a base lead. The current between one of these contacts and the base is varied by current applied through the second point contact. At the start of the program, the point-contact transistor was the only practical known type holding promise of considerable usefulness in amplifying and oscillating functions.
During the first couple of years, however, the results were generally disappointing, for two principal reasons. In the first place, the germanium used in the transistors was prepared from (p. 286) polycrystalline ingots, cut into small pieces. Each transistor used a different section of the ingot, with the result that the small pieces of crystal varied from one transistor to the next in the characteristics affecting performance. In the second place, the mechanical structure of the point-contact transistor left room for further variation from one unit to the next and was so delicate that the chance of failure was relatively high.
During the 1950–51 period, a number of extremely important developments changed this picture. A number of research organizations were involved by now in transistor development, with important contributions coming particularly from Bell and General Electric as well as from RCA. However, each organization was following its own line of research toward solution of the common problems. One of these was the question of obtaining large single crystals of germanium, and substantial advances apparently were made concurrently at several laboratories. RCA’s own solution was developed by Schuyler Christian, Arnold Moore, and Bernard Selikson, who achieved the apparatus and techniques for growing single crystals of sufficient size to produce material for several hundred transistors having uniform characteristics. During the same period, the program at Harrison resulted in a plastic-impregnated point-contact transistor virtually immune to failure resulting from mechanical or electrical changes during the life of the unit.
These advances were overshadowed during 1951 by an even more significant development that ranks among the most important contributions to the transistor art. This was the achievement in (p. 287) practical form of a different type known as the junction transistor, whose operation was based on the electrical characteristics of a junction between the semiconductor and a different material. The junction type of device had been conceived by Shockley in 1948, but its achievement in practical form required further research and development. Here again, the work went forward simultaneously in the various laboratories, with each following its own line.
A major contribution came in 1951 with the successful development at Princeton of a greatly improved type known as the alloy junction transistor. Achieved by a research team including Jacques Pankove, Russell Law, Charles Mueller, and Dietrich Jenny, the new RCA type consisted basically of a crystal wafer of germanium to which small dots of a different material, such as indium, were alloyed to form the electrical junction.
The junction transistor appeared generally to be a far less temperamental device than the point-contact type. Furthermore, while it did not at first equal the high-frequency performance of the point-contact transistor, it promised to be far more effective and economical in the low and medium frequency ranges employed in radio and television receiving circuits and in audio amplifiers.
Within a few months, the research program at Princeton was concentrated heavily upon the further development of the alloy junction transistor and its various possible applications. While there was still little information as to the progress of the transistor work in other laboratories, there was every reason to believe (p. 288) that the achievements by the research staff had put RCA well ahead of others in the field. RCA itself, however, was now issuing as much information as possible to its licensees to keep them informed of its progress in this new field. Numerous bulletins were distributed by the Industry Service Laboratory, and in November, 1952, the fruits of the intensive program were disclosed in a week-long symposium for licensees at the David Sarnoff Research Center.
The Bell announcement of the transistor in 1948 had posted a new direction sign for the electronics industry. By the same token, the RCA Laboratories symposium in 1952 laid out a broad highway for the industry to follow. More than 450 engineering and administrative representatives of RCA’s tube and electronic equipment licensees were given details of the RCA work on germanium purification and the construction and testing of point-contact and alloy junction transistors. Moreover, they received a comprehensive view of the new and practical field that was now being opened with the application of transistors.
Twenty-four experimental applications developed by the RCA Laboratories technical staff during the previous months were demonstrated to the licensees and to the press. Among them were AM, FM and automobile radio receivers, a dynamic transistor microphone, a portable battery-operated public address system, a loud-speaking telephone attachment, a portable transistor phonograph, and a roving microphone containing a short-range transistorized transmitter. The piece de resistance, perhaps, was a (p. 289) glimpse into the more distant future—a battery-powered portable television receiver employing 37 transistors and a 5-inch picture tube. Developed by George Sziklai, Robert Lohman, and Gerald Herzog, the experimental set operated on a single channel with a direct pickup range of about five miles.
The impressive demonstration underlined three RCA Laboratories achievements of basic importance. These were a solution to the crystal-growing problem, the development of high-frequency point-contact transistors, and the achievement of practical alloy junction transistors for a wide variety of receiving circuit and audio applications. Furthermore, the symposium itself played a significant part in hastening the development of transistorized equipment by others in the industry.
Transistors: The Second Stage
After the 1952 symposium, the transistor program divided itself into two principal efforts. Now that the research program had advanced the transistor to the practical stage, emphasis was placed on the development of materials and techniques suited to the mass production of standardized and reliable units. At the same time, the research effort was aimed ahead at a broader understanding of semiconductor characteristics, the improvement of materials, and the invention of new transistorized devices.
The first phase of the production effort was devoted to making transistors for the use of RCA’s own scientists and engineers in developing new devices and techniques. Production for the commercial market was given a high second priority, and it was to (p. 290) be established on a firm basis only after a hard struggle with cost factors and reliability standards. Ultimate success was achieved in both cases through the interchange of ideas between RCA Laboratories and the product divisions.
To make new transistors available as swiftly as possible for RCA’s own use, a pilot operation was established at Harrison with the guidance and cooperation of RCA Laboratories. By the end of 1953, this enterprise became the source of high quality radio-frequency and intermediate-frequency transistors for radio and television applications at Princeton and Camden. Late in 1954, direction of the Harrison program was given to Malter, who had played a prominent role in the research effort at Princeton.
During the same period, closely coordinated efforts were under way at Harrison and in Dodge’s tube assembly group at Princeton to develop improved commercial production techniques. One result of this work was an ingenious continuous processing technique worked out by Ralph Sherwood and ultimately transferred with him to the Somerville, N.J., plant of the newly organized RCA Semiconductor Division in 1956. While satisfactory production techniques were being worked out, the market for transistors was developing rapidly. In 1954, transistor sales by the industry amounted to less than $5 million—by 1964 they were to total well over $300 million. The coordinated research and development effort within RCA enabled the corporation to enter this market with a line of high-performance transistors of outstanding quality.
In parallel with the development of production techniques, work at Princeton and Camden carried forward the development of (p. 291) new transistorized circuits and equipment. Among the noteworthy achievements in this direction were the pocket-size and portable radio receivers designed by Loy E. Barton, and a variety of audio amplifiers, automobile radios and other equipment devised at Princeton by A. A. Barco, David D. Holmes, Larry E. Freedman, H. C. Lin, and others. At the same time, as we have seen, Flory and his associates in Zworykin’s laboratory were successful in developing increasingly compact closed-circuit and portable television pickup equipment with transistorized circuits.
Looking beyond these activities in applied research and engineering was the extensive forward-looking basic research program. At first, the fundamental aspects of the transistor project were aimed at determining the feasibility of transistors for performing many of the functions handled by electron tubes. After 1953, the emphasis was shifted to the extension of knowledge concerning the phenomena occurring in transistors, with the objective of developing improved semiconductor materials and techniques for application in new and more versatile solid-state devices. This stage of the program was organized under Harwick Johnson, in Herold’s Electronic Research Laboratory, employing more than a dozen members of the technical staff.
Ranging over semiconductor theory and application, the effort led to notable advances in the high-frequency performance and power output of transistors, and at the same time opened the way for use of new materials and techniques. Exploring the use of alternative semiconductor materials, several members of the group—notably Jenny and Herbert Nelson—developed silicon transistors (p. 292) for effective operation at temperatures too high for germanium devices. Jenny went on subsequently to develop new compound semiconductor materials, including gallium arsenide, giving promise of combining the best features of germanium and silicon in respect to frequency response over a broad range of temperatures. Following Jenny’s research with the compounds, a development program based on gallium arsenide and other compound semiconductor diodes and transistors was carried forward by the RCA Semiconductor and Materials Division at Somerville with Air Force support.
Another outstanding achievement in the research group was the drift transistor, developed by Herbert Kroemer and further analyzed by other members of the group, including [William] Webster and L. J. Giacoletto. The drift transistor, employing a precise arrangement of impurities within the region between the emitter and the collector, made possible far more rapid operation and higher frequency performance than had been achieved previously with transistors. As if to emphasize the close cooperation between the research organization and the product divisions in the transistor program, the drift transistor became a part of the commercial line of RCA transistors within months after its development at Princeton.
The increased knowledge of semiconductor phenomena generated through continuing basic studies brought an accelerating flow of useful new devices as the program forged ahead. An important later development was the “thyristor,” a high-speed switching transistor developed by Mueller, Hilibrand and others as a supplement and perhaps an ultimate solid-state replacement for the thyratron tube in a number of systems applications. (p. 293)
By the end of 1955, the RCA Laboratories transistor project had reached a crossover point, with the burdens of advanced development and production resting largely upon the product division. In a review of the research program at this time, Ewing and Wolff reported that the laboratories could now "transfer the comparatively large proportion of our staff assigned to the production and advanced development problems into the longer range research activities in preparation for the next major advance."
The Birthday Presents
An electronic amplifier of light, a system for recording television pictures and sound on magnetic tape, and an electronic air conditioner with no moving parts—these were General Sarnoff's requests in 1951. At the time, none of these items existed in any form, although there was (p. 294) good reason to assume that they were feasible in light of the advances that were taking place in electronic technology.
The RCA scientists not only met the multiple challenge within the specified time, but they also produced interesting secondary “presents” that were not on the original agenda.
The performance was something of a tour de force in research and engineering as applied to an unusually specific set of objectives. It occurred not only because the talent and experience existed within the RCA research staff, but also because an important part of the necessary fundamental knowledge had been accumulated in earlier projects having to do with solid-state and communications techniques.
The television tape recording problem was assigned to Olson’s group because of its long and close acquaintance with the magnetic tape recording of sound and its familiarity with such key mechanical problems as the maintenance of constant speed in recording and reproduction equipment. But while the same basic principles applied to both sound and television tape recording, there was a vast difference in the requirements to be met.
The best audio tape systems were designed to handle signals up to a maximum of 15,000 cycles per second, in the audible range. A television magnetic tape system that could record and reproduce pictures as well as sound would have to accommodate signals up to a maximum of 4,000,000 cycles per second. Furthermore, the objective in this case (p. 295) was a system to handle not only black-and-white signals, but also color television signals carrying considerably more information.
The problem was tackled so energetically by Olson and his group that a color television tape recording system was demonstrated publicly at Princeton in December 1953, little more than two years after General Sarnoff had made his request. The credit was shared by a technical team that included Houghton, Morgan, Artzt, Joseph Zenel, J. G. Woodward, and J. T. Fischer, working under Olson’s direction. Their achievement demonstrated for the first time the feasibility of a high-speed recording and playback system that would permit a television station in Chicago, for example, to pick up and record a color program broadcast from New York at, say, 7 p.m. New York time, and to put it on the air an hour later, at 7 p.m. Chicago time. This was possible because the system could reproduce tape-recorded visual program material either instantly or at any time thereafter, without further processing, just as in the case of tape-recorded sound. Furthermore, magnetic tape could be played any number of times, in the manner of film, but it also could be erased and re-used for recording other program material.
After the initial demonstration, the RCA Laboratories team began development of an improved system for field testing with the NBC engineering staff. The equipment made communications history in the spring of 1955 with the first long-distance transmission of a color television program recorded on magnetic tape, over a closed-circuit from New York to St. Paul, Minnesota. (p. 296) In October 1956, NBC used the system to record and broadcast the first commercial color television program material reproduced from a prerecorded magnetic tape.
It is interesting to note that a development program was in progress concurrently at RCA Laboratories to achieve a new and rapid technique of color film recording for television. Kell and a group of his associates, including [Alfred] Schroeder and John P. Smith, with a Camden engineering group working in the Applied Research Program, devised a method and equipment for recording color programs on lenticular film, a special type having tiny cylindrical lenses embossed on its surface to accommodate the three types of color information.
The system offered two principal benefits. Since lenticular film required only standard black-and-white processing methods, its cost was considerably lower than that of standard color film. Moreover, the processing time was only two hours, in contrast to the much longer time needed to process color film. Three of the new lenticular film systems, completed at Camden, were installed during 1956 at the NBC studios in Burbank, California, to record network color programs.
As for the magnetic tape system developed by Olson’s group at Princeton, the demonstration equipment was superseded in commercial use by a different type of color tape system developed at Camden with the aid of Eric Leyton, George Olive, and W. L. Behrend at RCA Laboratories. However, the Princeton project developed an interesting by-product for presentation to General Sarnoff on his anniversary in 1956. This was a (p. 297) small television tape player for the home, about the size of a table model television set, to play pre-recorded tapes over a standard home television receiver.
Further work by Houghton and others in Olson’s group resulted during 1958 in a recording attachment for the unit, so that it could record as well as reproduce program material either from broadcast transmissions or from a television camera.
Electronic Air Conditioning
The tape recording project was a dramatic application of advances in communication techniques and engineering know-how. The remaining “birthday presents,” by contrast, employed new knowledge generated in solid-state research. In the case of the electronic air conditioner, the solution was found in a phenomenon that had been lying around, largely neglected and incompletely understood, for more than a century.
This development had been assigned to [Nils] Lindenblad, principally because of his demonstrated inventiveness and persistence in a variety of earlier research projects. He began with a study of all previously observed phenomena that related to cooling by other than mechanical means. The most promising approach seemed to be the so-called Peltier effect, in which passage of a current through a junction of two dissimilar materials produces a measurable drop or rise in the temperature at the junction, depending upon the direction of the current. The phenomenon had been discovered 120 years earlier by French physicist Jean Charles Peltier, but it had remained only a scientific curiosity of some interest but little apparent utility. (p. 298)
By the time Lindenblad began his investigation, he was able to draw upon new information supplied by advances in the understanding of electron behavior in solid materials. Aided by Charles J. Busanovich, he developed new types of junctions employing alloys comprised of bismuth, tellurium, antimony, and other promising materials in various combinations. Soon he was achieving 40 degrees or more of cooling below room temperature, as against the maximum of 10 degrees attained in occasional earlier experiments elsewhere.
Coupling the materials work with ingenious engineering, Lindenblad designed and completed in 1953 the world’s first electronic refrigerator, complete with cold storage chamber and ice-making compartments, and entirely without moving parts. The pioneer device demonstrated for the first time the feasibility of Peltier cooling for practical applications.
The next step was development of a larger refrigerator and a room air conditioning system, taking advantage of the continuing improvement in materials for the cooling junctions.
By October 1, 1956, the results were displayed at General Sarnoff’s 50th anniversary celebration—the world’s first electronically air-conditioned room, and a larger and more efficient electronic refrigerator, both entirely free of moving parts or circulating fluids.
Housed in a simulated living room built under G. D. Nelson’s direction in the basement recreation room of the David Sarnoff Research Center, the demonstration chamber contained two large wall panels fashioned of one-inch metal squares from which heat was extracted by thermoelectric (p. 299) junctions on the outside surface. Operating silently by air convection and radiation, the panels kept the room at a temperature about 25 degrees below that outside. Moreover, by reversing the current, the panels could be made to heat the small room.
The successful demonstration awakened lively interest in the possibilities of electronic cooling and helped to stimulate research in many laboratories. At RCA, swift progress was made in improving thermoelectric materials under the leadership of F[red]. D. Rosi and his metallurgical research group. Improved junctions were designed by Lindenblad’s group and by advanced development teams of the Electron Tube and Semiconductor and Materials Divisions.
Technical leadership in electronic cooling won for RCA a U.S. Navy contract for thermoelectric cooling equipment for use in submarines. Subsequently, a cooperative program of RCA Laboratories and the Applied Research organization of RCA Defense Electronic Products produced a number of thermoelectric cooling devices, including a 9-ton air conditioner, a water cooler, and special-purpose low temperature cooling units. By early 1964, this had led to multi-stage thermoelectric units capable of cooling from room temperature down to nearly 175° below zero (F), and the prospect of even more effective units that will cool down to 276° below zero (F) for use with special cryogenic devices, such as infrared detectors, that require a low-temperature environment.
The Light Amplifier
The third of the “birthday presents,“ the light amplifier, proved the most sophisticated in a technical sense. This project was undertaken (p. 300)
by [Frederic] Nicoll and [Benjamin] Kazan, who employed two of the new solid-state effects developed in materials research. One of these was photoconductivity, the property of materials that act as insulators when they are in the dark, but whose resistance diminishes when they are exposed to light. The other was electroluminescence, the phenomenon exhibited by certain man-made materials which emit light in response to the direct application of an electric field or current.
Using a large-area photoconductor material developed by S. M. Thomsen, and electroluminescent phosphors created by Simon Larach, Ross Shrader, and Imre Hegyi, Nicoll and Kazan built a thin panel capable of increasing by 1,000 times the visible brightness of a projected light image. The two materials were sandwiched in adjacent layers between transparent electrodes, and the device was operated by applying a voltage across the assembly and projecting an extremely dim light image against the photoconductive layer. Wherever light from the image struck the photoconductor, the electrical resistance of the material broke down in proportion to the amount of light, allowing current to flow through to the electroluminescent layer. Wherever the current affected the electroluminescent layer, the material emitted light in proportion to the strength of the current. The result was a re-creation of the original projected image by the electroluminescent layer, but in far brighter form.
The photoconductor material used in the panel was sensitive to x-rays as well as to visible light. Using this property, Kazan also developed for demonstration on General Sarnoff’s anniversary an amplifying panel (p. 301) for potential use in x-ray fluoroscopy. In its initial form, the device displayed a long-persistence image nearly 100 times brighter than that appearing on a conventional fluoroscope screen, permitting x-ray observation of static objects in lighted surroundings and with greater visual detail.
In the following year, Kazan developed a 12-inch amplifying panel for x-ray use, incorporating a special erasing technique that allowed the user to remove the image rapidly from the viewing screen. As a potential tool for certain medical x-ray applications, the device was used in experiments during 1957 and 1958 at Princeton Hospital and the University of Pennsylvania. It also was displayed at the American Roentgen Ray Society conference in 1958 and received a prize awarded for developments of outstanding interest and potential importance in x-ray technology.
As General Sarnoff accepted the “birthday presents” at his anniversary observance in 1956, he recalled the original request and expressed more pleasure than surprise at its fulfillment by RCA scientists:
Unquestionably, the “birthday presents” opened promising new areas for future electronic growth, and they demonstrated impressively the ingenious results that can be expected when first-rate technical talents (p. 302) are applied to specific goals. At the same time, they were a general departure from the growing trend of research at RCA Laboratories. This trend, gathering momentum from the increasing concern with solid-state materials and electronic effects, placed growing emphasis upon fundamental studies and basic applications, leaving the translation of this knowledge into new technology to the advanced development groups associated with the product divisions. (p. 303)
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