John Bardeen, William B. Shockley, and Walter H. Brattain and the Invention of the Transistor John Bardeen, William Shockley, Walter Brattain Invention of the Transistor - Bell Laboratories More By Alaina G. Levine On December 14, 2006, the American Physical Society presented a plaque to Bell Laboratories in honor of John Bardeen (1908-1991), William B. Shockley (1910-1989), and Walter H. Brattain (1902-1987) for their invention of the transistor, which has been called “the most important invention of the 20th Century.”1 Developed from semiconductor material, the transistor was the first device that could both amplify an electrical signal, as well as turn it on and off, allowing current to flow or to be blocked.2 It was small in size, generated very low heat, and was very dependable, making possible a breakthrough in the miniaturization of complex circuitry.3 The transistor heralded in the “Information Age” and paved the way for the development of almost every electronic device, from radios to computers to space shuttles.

For their monumental “researches on semiconductors and their discovery of the transistor effect,"4 Bardeen, Shockley and Brattain were presented with the Nobel Prize in Physics in 1956. The genesis of the transistor emanates, interestingly enough, from a marketing problem. In the early part of the 20th Century, AT&T was engrossed in expanding its telephone service across the continent in an effort to beat the competition. The company turned to its research and development arm, Bell Laboratories, to develop innovations to meet this need. At the time, telephone technology was based on vacuum tubes, which were essentially modified light bulbs that controlled electron flow, allowing for current to be amplified. But vacuum tubes were not very reliable, and they consumed too much power and produced too much heat to be practical for AT&T’s needs. Furthermore, as scientists at Bell Labs discovered, transcontinental telephone communication required the use of ultrahigh frequency waves and the vacuum tubes were incapable of picking up rapid vibrations.5 An all-star team of scientists was assembled at Bell Labs to develop a replacement for the vacuum tubes based on solid-state semiconductor materials.6 Shockley, who had received his Ph.D.

in physics from the Massachusetts Institute of Technology in 1936 and joined Bell Labs the same year, was selected as the team leader. He recruited several scientists for the project, including Brattain and Bardeen. Walter Brattain had been working for Bell Labs since 1929, the year he received his Ph.D. in physics from the University of Minnesota. His main research interest was on the surface properties of solids.7 John Bardeen was a theoretical physicist with an industrial engineering background. With a Ph.D. in physics from Princeton University, he was working as an assistant professor at the University of Minnesota when Shockley invited him to join the group.8 The team commenced work on a new means of current amplification. In 1945, Shockley designed what he hoped would be the first semiconductor amplifier, an apparatus that consisted of “a small cylinder coated thinly with silicon, mounted close to a small, metal plate”.

The device didn't work, and Shockley assigned Bardeen and Brattain to find out why.9 In 1947, during the so-called “Miracle Month” of November 17 to December 23, Brattain and Bardeen performed experiments to determine what was preventing Shockley’s device from amplifying. They noticed that condensation kept forming on the silicon. Could this be the deterrent? Brattain submerged the experiment in water “inadvertently creating the largest amplification thus far.” Bardeen was emboldened by this result, and suggested they modify the experiment to include a [gold] metal point that would be pushed into the silicon surrounded by distilled water. At last there was amplification, but disappointingly, at a trivial level. But the scientists were galvanized by the meager result, and over the next few weeks, experimented with various materials and set ups. They replaced the silicon with germanium, which resulted in amplification 330 times larger than before. But it only functioned for low frequency currents, whereas phone lines, for example, would need to handle the many complicated frequencies of the human voice10. Next, they replaced the liquid with a layer of germanium dioxide.

When some of the oxide layer accidentally washed away, Brattain continued the experiment shoving the gold point into the germanium and voila! Not only could he still achieve current amplification, but he could do so at all frequencies. The gold contact had put holes in the germanium and the punctures "canceled out the effect of the electrons at the surface, the same way the water had."11 Their invention was finally increasing the current at all frequencies. Bardeen and Brattain had achieved two special results: the ability to get a large amplification at some frequencies, and a small amplification for all frequencies. Their goal now was to combine the two. The essential components of the device thus far were the germanium and two gold point contacts that were fractions of a millimeter apart. With this in mind, Brattain placed a gold ribbon around a plastic triangle, and cut it through one of the points. When the point of the triangle touched the germanium, electric current entered through one gold contact and increased as it rushed out the other. They had done it – it was the first point-contact transistor.

On December 23, Shockley, Bardeen and Brattain presented their “little plastic triangle” to the Bell Labs VIPs and it became official: the super star team had invented the first working solid state amplifier12. Following the triumph of the transistor, the three amplifying architects went their separate ways. Shockley left Bell Labs in 1955 to become the Director of the Shockley Semi-Conductor Laboratory of Beckman Instruments, Inc. in Mountain View, Ca. His company was one of the first of its kind in Northern California and quickly attracted more semiconductor labs and related computer firms to the area. Soon the region had a new moniker: Silicon Valley. Bardeen left Bell Labs in 1951 for a professorial appointment in electrical engineering and physics at the University of Illinois. He was named a member of the Center for Advanced Study of the University in 1959. He continued his research in solid state physics and in 1972 shared a second Nobel Prize in physics for the first successful explanation of superconductivity.

Brattain remained at Bell Labs and received various honorary degrees and awards for his work, including being named a Fellow of the APS, the American Academy of Arts and Sciences and the American Association for the Advancement of Science. Copyright © 2008, Alaina G. Levine 1 According to Ira Flatow, Host of Transitorized! , a PBS special Shockley, Brattain and Bardeen: Clashing Egos to the End What is that BOX on this page? Walter Brattain in 1974 on Shockley's ideas for who should get credit for the transistor: "He called both Bardeen and I in, shortly after the demonstration, and told us that sometimes the people who do the work don't get the credit for it. He thought then that he could write a patent, starting with the field effect, on the whole damn thing." Shockley, Brattain and Bardeen Clashing Egos to the End Although many scientists contributed along the way, it was three men who really brought the transistor to life, and each played a different role: the thinker, the tinkerer, and the visionary.

John Bardeen was the thinker, a man who could look at an event no one else comprehended and go beyond common understanding to explain it. Walter Brattain was the tinkerer, a builder who could put together any contraption asked. William Shockley was the visionary, a seer who predicted how important the transistor would be long before anyone else. All three were top-class scientists, and their unique skills brought together in one laboratory created the perfect environment for their grand invention. But their unique perspectives also made them ill fit to continue working together. They joined for a few years of brilliance and then went their separate ways due to a colossal clashing of egos. The three met just after World War II, when Bell Labs charged Shockley with the job of building a solid state amplifier. Brattain and Bardeen were members of his team, and the two began a tight-knit collaborationBrattain ran the experiments, Bardeen interpreted the results. Shockley was the overseer. He offered direction and made comments, but by and large he let the other two work by themselves. It was an ideal arrangement for maximum creativity, with no one stepping on the others' toes.

But when they reached their goal of building a working transistor, the issue of who deserved the credit became muddled. Shockley believed that since he had given the initial direction the idea for the transistor was wholly his. Shockley began a major campaign with the company's lawyers to patent the transistor exclusively under his own name. He called Bardeen and Brattain separately into his office and explained what he was doing. Brattain shouted at him: "There's more than enough glory in this for everybody!" Bardeen said nothing, but began to fume silently. The rift had begun. Shockley truly believed the other two had betrayed him, had taken his ideas and received credit where none was due. To get some of his own back, Shockley conceived of a substantially better transistor within a month. That transistor, a junction transistor , was destined to have more commercial success than that first point-contact transistor ever would. As Shockley kept his lab working on his own ideas, he kept Bardeen and Brattain as far removed from the work as possible. Bardeen would soon describe the situation as "intolerable." Feelings rose to a fever pitch of animosity as Shockley continued to claim sole responsibility for the transistor.

A classic Bell Labs press photo shows Shockley seated at a microscope, with the other two behind himas if Shockley had regularly sat down at a lab bench while Bardeen and Brattain merely watched. Brattain would later admit to hating that photo. The three could not continue to work together. Brattain soon asked to be transferred to a different lab at AT&T, where he stayed until retiring to be a professor at Whitman College. Bardeen took a job elsewhere within a couple yearsat the University of Illinoiswhere he could concentrate on physics theory and direct his own work instead of following someone else's lead. He and Brattain always kept in touch, often meeting up to play golf. Shockley soon hit a wall at AT&T. He became paranoid, a micromanager, not nearly as effective as he once was. He left to form a semiconductor company in California called Shockley Semiconductor. The company is known both for being the first of its kind in what was to become Silicon Valley; and for never producing a viable commercial producta situation for which Shockley's leadership was largely responsible.

The three men met up just a few other times in their lives, most notably in Stockholm to receive the 1956 Physics Nobel Prize for their joint invention. While Brattain and Bardeen spent much of the time there together, Shockley wasn't included in the group. But for one evening, the truth of Brattain's claim that there was enough glory here for everyone came true. Bumping into each other after the awards ceremony all three men spent a cordial evening together toasting their success. And then they flew back to the U.S. to separate lives once more: Brattain the tinkerer to Bell Labs' experiments; Bardeen the thinker to tackle his next set of hypotheses (he would win a second Nobel for his superconductivity theories); Shockley the visionary to launch an entire new semiconductor industry in Silicon Valleyand never to get credit for a single product built. ________________________________________________ Walter Brown debunks the myth created by the Bell Labs press photo: "Bardeen was not at all a laboratory experimentalist. He was a theorist. And he was the guy that provided the theoretical ideas for Brattain. It was Brattain who went in the lab and wired up the stuff and put the pieces together.

And Bardeen really didn't play a part in the laboratory scene at all. Their association was primarily outside the laboratory. Of course, there is the famous picture of Bardeen, Brattain and Shockley that's taken in Brattain's laboratory. But that really was not a very commoncertainly having the three of them together would be very uncommonbut having Brattain and Bardeen together in the laboratory wouldn't have been, that wouldn't have ordinarily happened. It would have happened in Bardeen's office more than it would have been in Brattain's lab." Resources: Walter Brattain interview by Lillian Hoddeson, copyright American Institute of Physics . John Bardeen - Educator, Physicist, Scientist, Inventor - Biography.com John Bardeen John Bardeen was co-winner of the Nobel Prize for Physics in 1956 for inventing the transistor and in 1972 for the theory of superconductivity. IN THESE GROUPS Famous University of Wisconsin at Madison Alumni Synopsis John Bardeen shared the 1956 Nobel Prize for Physics with William B. Shockley and Walter H. Brattain for their joint invention of the transistor.

In 1972, with Leon N. Cooper and John R. Schrieffer, Bardeen was awarded the Nobel Prize for Physics again, this time for the first successful explanation of superconductivity. Focusing on such areas as electrical conduction in semiconductors and metals, and surface properties of semiconductors, Bardeen was elected to the National Academy of Sciences in 1954. Early Years John Bardeen was born in Madison, Wisconsin, on May 23, 1908, the son of Dr. Charles R. Bardeen, the dean of the University of Wisconsin medical school. His intelligence apparent at an early age, Bardeen's parents had him skip from third grade right into junior high. He enrolled at the University of Wisconsin when he was 15 and majored in engineering, later getting his master's in engineering at UW as well. When Bardeen emerged from UW with his advanced degree, jobs were scarce, as the Depression was in full swing, and he ended up accepting a position with Gulf Oil as a geophysicist. After three years, Bardeen realized that his interests lay elsewhere and he went back to school, this time to Princeton for his Ph.D.

in mathematical physics. At Princeton, Bardeen began his serious studies of metals under Professor E.P. Wigner, using new theories of quantum mechanics to help further understanding of semiconductors. He finished his dissertation in 1935 and was offered a junior fellow position at Harvard, where he spent the next three years. During his stint at Harvard, Bardeen married Jane Maxwell. The couple would go on to have three children. The Nobel Prizes In 1945, after World War II came to an end, Bardeen took a position with Bell Telephone Laboratories, where he engaged in further research on semiconductors, specifically on how they conduct electrons. Two years later, Bardeen, William Shockley and Walter Brattain unveiled the transistor to the world, kick-starting a revolution in electronics. Besides replacing the vacuum tube, which was bulky and much larger, the transistor allowed for the miniaturizing of components needed for the eventual evolution of computers. The invention would lead to Bardeen and his fellow researchers winning the Nobel Prize for Physics in 1956. Meanwhile, Bardeen had returned to his earlier research on superconductivity, research that eventually explained the disappearance of electrical resistance when materials reach temperatures close to absolute zero.

His work with L.N. Cooper and J.R. Schrieffer resulted in the BCS theory of superconductivity (named for the trio's initials), which became the foundational theory for all later work in superconductivity. It also led to Bardeen's second Nobel Prize for Physics, which he shared with Cooper and Schrieffer. Legacy Nobel prizes aside, John Bardeen was one of the most decorated and influential scientists of his time. He was a fellow of the American Physical Society and a member of the President's Science Advisory Committee. He was elected to the National Academy of Sciences in 1954 and was awarded the Buckley Prize of the American Physical Society in 1955 and the Fritz London Award for work in low-temperature physics in 1962. Fact Check We strive for accuracy and fairness. If you see something that doesn't look right, contact us ! Citation Information William Shockley William Shockley 13 February 1910 - 1989, London, England principal papers Co invented the transistor with John Bardeen and Walter Brattain in 1947 Dr. John Bardeen, Dr. Walter Brattain, and Dr.

William Shockley discovered the transistor effect and developed the first device in December, 1947, while the three were members of the technical staff at Bell Laboratories in Murray Hill, NJ. They were awarded the Nobel Prize in physics in 1956. Biography William Shockley was born in London to American parents who were in England for several years on business. His father was a mining engineer and his mother a federal deputy surveyor of mineral lands. They returned to California when William was a toddler. His interest in science was encouraged from early on, through his parents' professions and by a neighbor who taught physics at Stanford. He graduated from Cal Tech in 1932 and then received his PhD from MIT in 1936. He began work immediately at Bell Labs. His research in solid state physics, especially vacuum tubes, made many theoretical advances in the company's goal to use electronic switches for telephone exchanges instead of the mechanical switches used up until then. During World War II, Shockley worked on military projects, particularly refining radar systems. As soon as the war ended, he was back doing solid-state research, now investigating semiconductors.

One of his major contributions to the electronics industry was to apply quantum theory to the development of semiconductors. In 1947, with colleagues John Bardeen and Walter Brattain, he made the first successful amplifying semiconductor device. They called it a transistor (from transfer and resistor). Shockley made improvements to it in 1950 which made it easier to manufacture. His original idea eventually led to the development of the silicon chip. Shockley, Bardeen, and Brattain won the 1956 Nobel Prize for the development of the transistor. It allowed electonic devices to be built smaller and lighter and even cheaper. He left Bell Labs in 1955 and served as visiting professor and consulant at various universities and corporations. He started his own lab to develop transistors and other devices. The business changed hands a few times and finally folded in 1968. In 1963, Shockley was appointed professor of engineering at Stanford University where he taught until 1975. Teaching made him think a great deal himself about the thought process and how scientific thinking might be improved.

His general ideas got more specific with time, becoming very similar to the theories of the eugenics movement of the 1910s and 1920s. He argued that the future of the population was threatened because people with low IQs had more children than those with high IQs. His views became increasingly controversial and race-based. While people continued to respect his achievements in physics and engineering, many public figures and scientists pointed out that "his contributions to physics did not lend scientific credence to his judgments on genetics." Shockley was married twice, and had two sons and one daughter. Mountain climbing was his chief hobby, which he did not pursue so much for relaxation, family members noted, as for a problem to be solved. "The half-baked ideas of people are better than the ideas of half-baked people." Chronology 1932 graduated from Cal Tech 1936 eceived his PhD from MIT 1940-45 worked on military projects, particularly refining radar systems 1947, December Dr. John Bardeen, Dr. Walter Brattain, and Dr.

William Shockley discovered the transistor effect and developed the first device 1955 Left Bell labs and started a career as visiting professor in various universities 1956 Nobel Prize in physics with Dr. Walter Brattain, and Dr. William Shockley for the invention of the transitor 1963 - 1975 Professor of engineering at Stanford University 1989 Died in London, England 1956 Received the Nobel prize for his co-invention of the transistor John Bardeen click on home button to go to mainpage John Bardeen 23 May 1908, Madison, Wisconsin, USA 30 Jan1991 Co invented the transistor with Walter Brattain and William Shockley in 1947 Dr. John Bardeen, Dr. Walter Brattain, and Dr. William Shockley discovered the transistor effect and developed the first device in December, 1947, while the three were members of the technical staff at Bell Laboratories in Murray Hill, NJ. They were awarded the Nobel Prize in physics in 1956. John Bardeen also received a Nobel prize for his work on superconductivity.

Biography A brilliant theorist, Dr. Bardeen brought his keen understanding to the transistor team by explaining effects found in early transistor experiments. Dr. Bardeen, born and raised in Madison, Wisconsin, obtained his Ph.D. in mathematics and physics from Princeton University in 1936. A staff member of the University of Minnesota, Minneapolis, from 1938 to 1941, he served as principal physicist at the US Naval Ordinance Laboratory in Washington, DC, during World War II, after which he joined Bell Telephone Laboratories, Inc. My introduction to semiconductors came just after the war, in late 1945, when I joined the Bell Laboratories research group on solid-state physics, which was being formed under the leadership of Stanley Morgan and William Shockley, Dr. Bardeen once related. Following a Ph.D. under Eugene Wigner at Princeton and post-doctoral years with John H. Van Vleck at Harvard, I had been interested in the theory of metals before the war and was anxious to go back to solid-state physics after five years at the Naval Ordnance Laboratory in Washington. While at Harvard, Dr.

Bardeen had become friends with James B. Fisk, who in 1945 was director of research at Bell Labs. Bardeen also knew Shockley when he was a graduate student at M.I.T. It was they who persuaded me to join the group rather than return to my academic post at Minnesota. I was the first outsider to be recruited; the rest of the initial group had been at Bell Laboratories for some years. There he conducted research on the electron-conducting properties of semiconductors. This work led to the invention of the transistor. Conditions were rather crowded when I arrived at the Murray Hill, NJ, laboratory. The wind-up of World War II research was still going on. He said a new building was under construction, so he was asked to share an office with Walter Brattain and Gerald Pearson. I had known Walter since my graduate student days at Princeton. Although at that time I had not decided what field of solid-state physics I would work in, they soon got me interested in their problems and I became deeply engrossed in trying to learn what was known about semiconductor theory. Dr.

Bardeen won the Nobel prize in 1956 as co-inventor of the transistor, and again in 1972 as co-developer of the theory of superconductivity at low temperatures. Dr. Bardeen left Bell Labs in 1951 to join the faculty at University of Illinois, where he dedicated himself to research superconductivity. He died at age 78.( 2 ) 1936 obtained his Ph.D. in mathematics and physics from Princeton University 1938 to 1941 Staff member of the University of Minnesota, Minneapolis 1945 Joined the Bell Laboratories on solid-state physics 1947, December Dr. John Bardeen, Dr. Walter Brattain, and Dr. William Shockley discovered the transistor effect and developed the first device 1951 Faculty of physics at University of Illinois, conducted research superconductivity.

1956 Received the Nobel prize for his co-invention of the transistor 1972 Received the Nobel prize as co-developer of the theory of superconductivity at low temperatures 1987 Died at 78 Honors and awards 1956 Nobel Prize in physics with Dr. Walter Brattain, and Dr. William Shockley for the invention of the transitor 1972 Nobel prize as co-developer of the theory of superconductivity at low temperatures Transistor History - Invention of the Transistor Fascinating facts about the invention of Transistors by John Bardeen, Walter Brattain, and William Shockley in 1947. TRANSISTOR Almost every piece of equipment that stores, transmits, displays, or manipulates information has at its core silicon chips filled with electronic circuitry. These chips each house many thousands or even millions of transistors. The history of the transistor begins with the dramatic scientific discoveries of the 1800's scientists like Maxwell, Hertz, Faraday, and Edison made it possible to harness electricity for human uses.

Inventors like Braun, Marconi, Fleming, and DeForest applied this knowledge in the development of useful electrical devices like radio. Their work set the stage for the Bell Labs scientists whose challenge was to use this knowledge to make practical and useful electronic devices for communications. Teams of Bell Labs scientists, such as Shockley, Brattain, Bardeen, and many others met the challenge.--and invented the information age. They stood on the shoulders of the great inventors of the 19th century to produce the greatest invention of the our time: the transistor. The transistor was invented in 1947 at Bell Telephone Laboratories by a team led by physicists John Bardeen, Walter Brattain, and William Shockley. At first, the computer was not high on the list of potential applications for this tiny device. This is not surprisingwhen the first computers were built in the 1940s and 1950s, few scientists saw in them the seeds of a technology that would in a few decades come to permeate almost every sphere of human life. Before the digital explosion, transistors were a vital part of improvements in existing analog systems, such as radios and stereos.

When it was placed in computers, however, the transistor became an integral part of the technology boom. They are also capable of being mass-produced by the millions on a sliver of siliconthe semiconductor chip. It is this almost boundless ability to integrate transistors onto chips that has fueled the information age. Today these chips are not just a part of computers. They are also important in devices as diverse as video cameras, cellular phones, copy machines, jumbo jets, modern automobiles, manufacturing equipment, electronic scoreboards, and video games. Without the transistor there would be no Internet and no space travel. In the years following its creation, the transistor gradually replaced the bulky, fragile vacuum tubes that had been used to amplify and switch signals. The transistor became the building block for all modern electronics and the foundation for microchip and computer technology. TO LEARN MORE The Transistor - History The Transistor in a Century of Electronics A Three Terminal Device Vacuum tubes were made containing several three terminal devices called triodes. The transistor is a three terminal, solid state electronic device. In a three terminal device we can control electric current or voltage between two of the terminals by applying an electric current or voltage to the third terminal.

This three terminal character of the transistor is what allows us to make an amplifier for electrical signals, like the one in our radio. With the three-terminal transistor we can also make an electric switch, which can be controlled by another electrical switch. By cascading these switches (switches that control switches that control switches, etc.) we can build up very complicated logic circuits. These logic circuits can be built very compact on a silicon chip with 1,000,000 transistors per square centimeter. We can turn them on and off very rapidly by switching every 0.000000001 seconds. Such logic chips are at the heart of your personal computer and many other gadgets you use today. Light Bulbs and Vacuum Tubes The transistor was not the first three terminal device. The vacuum tube triode preceded the transistor by nearly 50 years. Vacuum tubes played an important role in the emergence of home electronics and in the scientific discoveries and technical innovations which are the foundation for our modern electronic technology. Thomas Edison's light bulb was one of the first uses of vacuum tubes for electrical applications.

Soon after the discovery of the light bulb, a third electrode was placed in the vacuum tube to investigate the effect that this electrode would have on "cathode rays," which were observed around the filament of the light bulb. Joseph John Thomson developed a vacuum tube to carefully investigate the nature of cathode rays, which resulted in his discovery, published in 1897. He showed that the cathode rays were really made up of particles, or "corpuscles" as Thomson called them, that were contained in all material. Thomson had discovered the electron, for which he received the Nobel Prize in Physics 1906 . Lee De Forest and The Radio Radio brought information rapidly to the masses and was the first widely used electronic device in the home. At the same time as physicists were trying to understand what cathode rays were, engineers were trying to apply them to make electronic devices. In 1906, an American inventor and physicists, Lee De Forest, made the vacuum tube triode, or audion as he called it. The triode was a three terminal device that allowed him to make an amplifier for audio signals, making AM radio possible. Radio revolutionized the way in which information and entertainment reached the great majority of people.

The vacuum tube triode also helped push the development of computers forward a great deal. Electronic tubes were used in several different computer designs in the late 1940's and early 1950's. But the limits of these tubes were soon reached. As the electric circuits became more complicated, one needed more and more triodes. Engineers packed several triodes into one vacuum tube (that is why the tube has so many legs) to make the tube circuits more efficient. Early Computers The largest computers based on vacuum tubes had racks and racks of tubes filling large rooms. The vacuum tubes tended to leak, and the metal that emitted electrons in the vacuum tubes burned out. The tubes also required so much power that big and complicated circuits were too large and took too much energy to run. In the late 1940's, big computers were built with over 10,000 vacuum tubes and occupied over 93 square meters of space. The problems with vacuum tubes lead scientists and engineers to think of other ways to make three terminal devices. Instead of using electrons in vacuum, scientists began to consider how one might control electrons in solid materials, like metals and semiconductors.

Already in the 1920's, scientists understood how to make a two terminal device by making a point contact between a sharp metal tip and a piece of semiconductor crystal. These point-contact diodes were used to rectify signals (change oscillating signals to steady signals), and make simple AM radio receivers (crystal radios). However, it took many years before the three terminal solid state device - the transistor - was discovered. The First Transistor The first point contact transistor made use of the semiconductor germanium. Paper clips and razor blades were used to make the device. In 1947, John Bardeen and Walter Brattain, working at Bell Telephone Laboratories, were trying to understand the nature of the electrons at the interface between a metal and a semiconductor. They realized that by making two point contacts very close to one another, they could make a three terminal device - the first "point contact" transistor. They quickly made a few of these transistors and connected them with some other components to make an audio amplifier. This audio amplifier was shown to chief executives at Bell Telephone Company, who were very impressed that it didn't need time to "warm up" (like the heaters in vacuum tube circuits).

They immediately realized the power of this new technology. This invention was the spark that ignited a huge research effort in solid state electronics. Bardeen and Brattain received the Nobel Prize in Physics, 1956, together with William Shockley, "for their researches on semiconductors and their discovery of the transistor effect." Shockley had developed a so-called junction transistor, which was built on thin slices of different types of semiconductor material pressed together. The junction transistor was easier to understand theoretically, and could be manufactured more reliably. Limits of Individual Transistors Individual electronic components were soldered on to printed circuit boards. For many years, transistors were made as individual electronic components and were connected to other electronic components (resistors, capacitors, inductors, diodes, etc.) on boards to make an electronic circuit. They were much smaller than vacuum tubes and consumed much less power. Electronic circuits could be made more complex, with more transistors switching faster than tubes. However, it did not take long before the limits of this circuit construction technique were reached. Circuits based on individual transistors became too large and too difficult to assemble. There were simply too many electronic components to deal with.

The transistor circuits were faster than vacuum tube circuits, and there were noticeable problems due to time delays for electric signals to propagate a long distance in these large circuits. To make the circuits even faster, one needed to pack the transistors closer and closer together. The Integrated Circuit Integrated circuits placed all components in one chip, drastically reducing the size of the circuit and its components. In 1958 and 1959, Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Camera, came up with a solution to the problem of large numbers of components, and the integrated circuit was developed. Instead of making transistors one-by-one, several transistors could be made at the same time, on the same piece of semiconductor. Not only transistors, but other electric components such as resistors, capacitors and diodes could be made by the same process with the same materials. For more than 30 years, since the 1960's, the number of transistors per unit area has been doubling every 1.5 years. This fantastic progression of circuit fabrication is known as Moore's law, after Gordon Moore, one of the early integrated circuit pioneers and founders of Intel Corporation.

The Nobel Prize in Physics 2000 was awarded to Jack Kilby for the invention of the integrated circuit. From the dawn of the vacuum tube triode, to the discovery of the transistor and the development of the integrated circuit, the 20th century has certainly been the century of electronics. By Professor David B Haviland First published 19 December 2002 biography John Bardeen. The Nobel Prize in Physics John Bardeen The Nobel Prize in Physics 1972 biography John Bardeen was born in Madison, Wisconsin, May 23, 1908. He attended the University High School in Madison for several years, and graduated from Madison Central High School in 1923. This was followed by a course in electrical engineering at the University of Wisconsin, where he took extra work in mathematics and physics. After being out for a term while working in the engineering department of the Western Electric Company at Chicago, he graduated with a B.S. in electrical engineering in 1928. He continued on at Wisconsin as a graduate research assistant in electrical engineering for two years, working on mathematical problems in applied geophysics and on radiation from antennas.

It was during this period that he was first introduced to quantum theory by Professor J.H. Van Vleck. Professor Leo J. Peters, under whom his research in geophysics was done, took a position at the Gulf Research Laboratories in Pittsburgh, Pennsylvania. Dr. Bardeen followed him there and worked during the next three years (1930-33) on the development of methods for the interpretation of magnetic and gravitational surveys. This was a stimulating period in which geophysical methods were first being applied to prospecting for oil. Because he felt his interests were in theoretical science, Dr. Bardeen resigned his position at Gulf in 1933 to take graduate work in mathematical physics at Princeton University. It was here, under the leadership of Professor E.P. Wigner, that he first became interested in solid state physics. Before completing his thesis (on the theory of the work function of metals) he was offered a position as Junior Fellow of the Society of Fellows at Harvard University. He spent the next three years there working with Professors Van Vleck and Bridgman on problems in cohesion and electrical conduction in metals and also did some work on the level density of nuclei. The Ph.D.

degree at Princeton was awarded in 1936. From 1938-41 Dr. Bardeen was an assistant professor of physics at the University of Minnesota and from 1941-45 a civilian physicist at the Naval Ordnance Laboratory in Washington, D.C. His war years were spent working on the influence fields of ships for application to underwater ordnance and minesweeping. After the war, he joined the solid-state research group at the Bell Telephone Laboratories, and remained there until 1951, when he was appointed Professor of Electrical Engineering and of Physics at the University of Illinois. Since 1959 he has also been a member of the Center for Advanced Study of the University. Dr. Bardeen's main fields of research since 1945 have been electrical conduction in semiconductors and metals, surface properties of semiconductors, theory of superconductivity, and diffusion of atoms in solids. The Nobel Prize in Physics was awarded in 1956 to John Bardeen, Walter H. Brattain, and William Shockley for "investigations on semiconductors and the discovery of the transistor effect," carried on at the Bell Telephone Laboratories.

In 1957, Bardeen and two colleagues, L.N. Cooper and J.R. Schrieffer, proposed the first successful explanation of superconductivity, which has been a puzzle since its discovery in 1908. Much of his research effort since that time has been devoted to further extensions and applications of the theory. Dr. Bardeen died in 1991. An Industrious Job Offer Brattain and Bardeen on the golf course John Bardeen had met William Shockley when they were both in school in Massachusetts. In 1945, when World War 2 ended, Shockley was put in charge of a new research group at Bell Labs and he wanted Bardeen on the team. Since Bell offered Bardeen twice his salary at Minnesota, Bardeen didn't have to think long about the offer. John and Jane Bardeen, along with their three young children, moved to New Jersey. Bardeen also knew another member of the group, Walter Brattain, from his grad school days. Bardeen was introduced to Walter Brattain by Bardeen's good friend Bob, Walter's brother.

Over the years their friendship grew, both in the lab and on the golf course where they spent time on the weekends. The two made a great team, with Brattain putting together the experiments and Bardeen weaving theories to explain the results. The First Transistor In the spring of 1947, Shockley set Brattain and Bardeen a task: explain why an amplifier he'd devised didn't work. At the heart of this amplifier was a crystal of silicon (they would switch to germanium several months later). To figure out what was going on, Bardeen had to remember some of the quantum mechanics research that had been done on semiconductors while he was at Princeton in the 1930s. He had also come up with some new theories himself. By observing Brattain's experiments, Bardeen realized that everyone had been assuming electrical current traveled through all parts of the germanium in a similar way. That was wrong: electrons behaved differently at the surface of the metal. If Brattain and Bardeen could control what was happening at the surface, the amplifier should work. It took them until the end of 1947, but on December 23 the pair succeeded.

They had built the first point-contact transistor. Things Begin to Sour After the invention of the transistor, the mood in the lab took a turn for the worse. Shockley resented the fact that he missed the invention. He went to work on his own, developing the improved, more stable junction or sandwich transistor. Relationships fell apart completely when Shockley blocked Bardeen from working on things that interested him. By 1951 Bardeen had started looking for a new job. When his friend Fred Seitz convinced the University of Illinois to make Bardeen an offer of $10,000 a year, he left Bell Labs with little regrets. In a memo to Mervin Kelly he wrote: "My difficulties stem from the invention of the transistor. Before that there was an excellent research atmosphere here." Bardeen at University of Illinois Allowed to Follow His Own Path The University of Illinois lured John Bardeen with the one thing he wanted most � the right to research whatever he wanted. Bardeen decided to work on superconductivity, which had begun to interest him in his last days at Bell Labs.

The Nobel Prize On the morning of Thursday, November 1, 1956, John Bardeen was making breakfast and listening to the radio. As he scrambled his eggs, he heard a newscaster announce that the Nobel Prize in physics had been awarded to him, Brattain, and Shockley for the invention of the transistor. Bardeen dropped the frying pan and ran into the bedroom to tell his wife Jane the news. The Nobel ceremony took place in Sweden on the evening of Monday, December 10. Shockley arrived late, with his wife and mother in tow. Bardeen and Brattain spent the time together getting ready. Bardeen had to borrow an extra white vest and white tie for his formal suit from Brattain since Bardeen's had turned green at the laundry. Then the nervous pair shared a bottle of quinine to settle their stomachs. They received their awards that night from King Gustav VI and then adjourned for a great banquet in their honor. After dinner, Brattain, Bardeen, their families, and Swedish friends sat around a table at their hotel celebrating. Towards the end of the night, Shockley walked in and was invited to join the party.

For one night, the group was together again. The three men remembered the days when they had been friends and a phenomenal research team. John Bardeen brought only one of his three children to Stockholm so as not to disrupt the other two sons' studies at Harvard. King Gustav scolded Bardeen about leaving his family behind on such an important occasion. He assured the King that the next time he would bring all his children. A Second Nobel By then, Bardeen was much more fascinated by the research that was taking up his time in Illinois: superconductivity. In 1957, along with post-doctoral student Leon Cooper and graduate student Bob Schrieffer, Bardeen developed the first theory on how extremely cold metals are able to conduct electricity so efficiently. To this day, this theory is known as the BCS theory (for Bardeen, Cooper, and Schrieffer). In 1972, the three men were awarded a Nobel for their work. John Bardeen became the only person in history to have received two Nobel Prizes in physics. And he did bring all his children to the next Nobel ceremony.

Bardeen lived out the rest of his years in Urbana, teaching, researching, and playing his favorite sport: golf. He died in 1991 at the age of eighty-two. sponsors link ������ ���� Research Profile - John Bardeen Research Profile Nobel Prize in Physics 1956 together with William B. Shockley and Walter H. Brattain "for their researches on semiconductors and their discovery of the transistor effect". John Bardeen occupies a unique place in the pantheon of Nobel Prize Laureates. Up to this day, he is the only scientist to have won two Nobel Awards in the same category: physics. The successes Bardeen achieved were in large part related to the circumstance that his research enterprises were situated at the boundary between industrial and academic environments, which Bardeen crossed more than once during his life. Believing that there was no fundamental distinction between pure and applied science, Bardeen was a theoretical physicist who since the beginning of his career focused on the application of quantum mechanics to solid-state physics. In this field, Bardeen made several major contributions, but he is especially remembered for the achievements that gained him the two Nobel Prizes in physics.

The first was the discovery of the point-contact transistor in 1947, along with his co-worker Walter Brattain at the AT&T Bell Telephone Laboratories (Bell Labs in short). After the discovery of the transistor had dramatically transformed the field of electronic communications, the two Bell Labs physicists shared the 1956 Nobel Prize in Physics with their colleague William Shockley who invented the junction transistor in 1948. Worsening of the working conditions led Bardeen to leave Bell Labs and accept an academic position at the University of Illinois at Urbana-Champaign in 1951. There, he conducted research aimed at understanding the phenomenon of superconductivity. In 1957, along with the postdoctoral associate Leon Cooper and his PhD student John Schrieffer, Bardeen put forward the first successful microscopic theory of superconductivity. The Bardeen-Cooper-Schrieffer theory, better known as BCS theory, was able to make precise predictions about many empirical phenomena concerning superconductivity as well as the phase transition between the normal and the superconducting states. After a number of physicists contributed to clarify its deep implications, the BCS theory became the orthodox microscopic description of superconductivity.

In 1972, fifteen years after the publication of their breakthrough paper, Bardeen received the second Nobel Award in Physics, along with his co-workers Cooper and Schrieffer. Looking for a non-academic career path John Bardeen was born in Madison¬—the capital of Wisconsin—on the 23rd of May 1908, to the Professor of Anatomy and Dean of the Medical School of the University of Wisconsin at Madison Charles R. Bardeen and his wife Althea Harmer. Since an early age, Bardeen showed great inclination for natural sciences graduating from Madison Central High School at the remarkably young age of fifteen. Confronted with the decision about his undergraduate studies, Bardeen chose electrical engineering, the main rationale being that he did not want to follow his father’s steps and become an academic. Electrical engineering, in his view, offered the opportunity to follow his natural inclination towards natural sciences, while, at the same time, allowing him to pursue a rewarding career in industry. In 1923, Bardeen enrolled at the University of Wisconsin at Madison and, five years later, he earned his bachelor after having gained some experience at the engineering laboratory of the Western Electric Company in Chicago.

After graduation, Bardeen continued as a graduate student at the same university, mainly working on mathematical problems in applied geophysics. In this period, Bardeen was introduced to quantum mechanics by John H. van Vleck—at the time one of the few American theoretical physicists working on the recently developed quantum mechanics and an expert of the application of the theory to the solid state. Van Vleck would receive the Nobel Prize in Physics, along with Philip W. Anderson and Nevill F. Mott, “for their fundamental theoretical investigations of the electronic structure of magnetic and disordered systems” in 1977. Bardeen earned his M.Sc. with a thesis on electrical prospecting for oil under the supervision of the American geophysicist Leo J. Peters in 1929. Unfortunately, the 1929 stock market crisis had rapidly deteriorated the job prospect for a young and brilliant electrical engineer as Bardeen undoubtedly was. Thus, Bardeen decided to remain at the university making research on theoretical problems concerning antennas. After having evaluated the very few job offers, Bardeen eventually followed his thesis advisor to the Gulf Research Laboratories in Pittsburgh, Pennsylvania.

There, Bardeen worked the next three years on the development of methods for the interpretation of magnetic and gravitational surveys. Return to pure science The experience at the Gulf Research Laboratories was not completely satisfying, and Bardeen resolved to enrol at Princeton University to pursue PhD studies in mathematical physics in 1933. In Princeton, Bardeen became interested in solid-state physics and in the application of quantum mechanical laws to many-body systems. His supervisor was the Hungarian Jewish physicist Eugene Wigner, who was working at Princeton University since 1930 and had recently decided to stay in the United States because of the growth of anti-Semitism and the worsening of the political climate in Germany after the rise to power of the Nazis. Wigner had been working on the development of the theory of groups and its application to quantum mechanics since 1927. Recently, Wigner had got interested in the application of quantum mechanics to the theory of solids and Bardeen made his PhD research on such a topic. Along with other two PhD students of Wigner’s—Frederick Seitz and Conyers Herring—Bardeen was part of the first generation of American physicists trained to apply quantum mechanics to real solids together with the group of John Slater’s graduate students at MIT.

Building on the work Wigner was carrying on with Seitz on the quantum mechanical computation of the approximate band structures of sodium, Bardeen developed a method for calculating the work function of metals; i.e., the minimum energy necessary to remove an electron from the surface of a metal to infinity. Even before receiving his PhD, Bardeen became Junior Fellow in the eminent Harvard’s Society of Fellows. At Harvard, Bardeen remained three years from 1935 to 1938 pursuing research on the application of quantum mechanics to many-body problems. At that time, one of the most important targets was the development of theoretical tools that allowed the extension of quantum mechanical laws to large aggregates of simple entities. Bardeen struggled to work out meaningful expressions for the description of the interactions between electrons as well as between electrons and the ionic lattice with the hope to develop a reliable theory of superconductivity—the phase transition of certain metals and alloys that completely lose their electrical resistance below a certain temperature, called critical temperature. However, all his attempts met with frustration because of the lack of adequate theoretical techniques.

Nevertheless, his Harvard experience was very fruitful, especially because he worked in close contact with two eminent physicists who had a long-lasting influence on Bardeen’s future works: Van Vleck and Percy Bridgman. Van Vleck continued to be a guiding light for what concerned the most novel advancements of quantum theory. Bridgman, on the other hand, was an American experimental physicist who had already been appreciated as the World’s leading expert on high-pressure physics, for which he would be awarded the Nobel Prize in 1946. Bardeen worked together with Bridgman in order to provide theoretical models for the experimental data that Bridgman was recording. This kind of close connection with the experimenter’s work would rapidly become a key feature of Bardeen’s style of doing research, which would play a fundamental role in the discovery of the point-contact transistor. While at Harvard, he became acquainted with Shockley who was also working on the application of quantum mechanics to materials, after having pursued a doctoral research entitled Electronic Bands in Sodium Chloride under Slater at MIT. In 1938, Shockley accepted a research position at Bell Labs where he was later invited to build a research group devoted to the study of the properties of semiconductors.

Shockley was instrumental in bringing Bardeen to Bell Labs after the Second World War, when Bardeen was called to become a member of the newly born group. Research at Bell Labs and the invention of the transistor After a two-year period spent at the University of Minnesota and another three years devoted to war-related research in electrical engineering at the Naval Ordnance Laboratory during World War II, Bardeen joined the semiconductor group headed by Shockley at Bell Labs in late 1945. Since its establishment in 1925, Bell Labs had been strongly committed to pure research. One of the convictions of Bell Labs’ first president—Frank B. Jewett—was that research not strictly related to short-term needs of the firm should be pursued because it would provide new technologies that might become fundamental in the long run. In the early 1930s, the newly appointed director of research of Bell Labs—Mervin J. Kelly—began creating a group of theoretical physicists who would explore novel theoretical advancements that might possibly be useful for communication technology. One of the most important targets was to find a better alternative to vacuum tubes as amplifier for telephone lines.

Since the beginning of the 20th century, vacuum tubes had been successful in providing a reasonably economic means for the amplification of electrical signals. Various technological improvements had made these devices more and more efficient, but they still had several shortcomings—the most important of which were their fragility, their large dimension and the fact that they consumed a lot of power. Shockley had begun investigating solid-state amplifiers in 1938. After the end of the war, he was invited to build a small research group whose target was to explore semiconductors as possible amplifiers, an alternative to vacuum tubes. Bardeen was one of the members of the small group along with the experimental physicist W. Brattain, G.L. Pearson (who was mainly concerned with bulk properties), the physical chemist Robert Gibney, and the circuit expert Helbert Moore. None of them had worked on semiconductors during the war. However, the group could make good use of the several improvements made in war-related research activities. In particular, since semiconductors had been employed in radar detectors, several techniques had been developed to obtain highly purified germanium and silicon.

Because of the development of these novel techniques, germanium and silicon were considered the ideal elements for conducting research on semiconductor amplifiers. It was, indeed, relatively easy to control the electrical properties of these materials by introducing appropriate amounts of donor and acceptor impurities. Soon after his hiring, Bardeen focused on the development of the theory of semiconductors building on the advancements made before the war; especially, Alan Wilson’s quantum mechanical theory of the energy band model, Victor Frenkel’s theory of photoconductive phenomena, and Walter Schottky’s mathematical theory of contact rectification—the modification of current from direct to alternate. Although the idea that semiconductors could be used as amplifiers seemed reasonable, there were strong uncertainties about how to build this kind of device. In 1945, Shockley suggested to apply a strong transverse electric field to a slab of semiconductor material in order to modify its conductance—an effect that came to be called field effect. According to Shockley, a strong transverse electric field would have produced a significant amplification in an alternating current signal. Various experimental tests of Shockley’s hypothesis were performed at the Bell Labs, which showed negligible or null amplification.

Shortly afterwards, Bardeen was asked to investigate why Shockley’s theory did not work as expected. This series of events led Bardeen to investigate the theory of surfaces—a topic he had already encountered during his PhD research. Bardeen suggested that a large part of the surface electrons in semi-conductors were immobilized in specific states and that, for this reason, they could not participate to conduction. After intensive experimental research conducted at Bell Labs and elsewhere showed that there was enough evidence for the existence of free surface states in semi-conductors, Bardeen began working with Brattain to modify the levels of surface barriers. The employment of an electrolyte seemed a possible method to overcome the surface states and construct an amplifier. Instead of working with a thin film of semiconductor material obtained by evaporation, Bardeen and Brattain used a slab of p-type silicon and produced an inversion layer of n-type conductivity by oxidising the surface. After further modifications of the apparatus, Bardeen and Brattain produced a device that actually amplified electric signals in a very effective way, but different from the field effect on which they were working. The apparatus they created allowed holes (empty electron states that acted as positive charges) to flow into the block of n-type germanium.

The final design, suggested by Bardeen, was based on the linking of the germanium to two slightly separated metal point contacts made of gold. In this way, the holes introduced into the germanium through the positively charged point contact (the emitter) could flow rapidly away through the negatively charged point-contact (the collector). The new device was tested on December 16, 1947 and it showed considerable voltage, current, and power amplification. The Bardeen-Brattain device was the first solid-state electronic transistor ever created—an invention that would rapidly change the field of electronics. Shockley—who was not directly involved in the discovery of the point-contact transistor—made many efforts to produce a new device, at the same time preventing his collaborators Bardeen and Brattain from further improving the newly discovered transistor. In a few months, Shockley put forward a second type of transistor called junction device, to the development of which he had worked secretly, while Bardeen and Brattain were busy in drafting patent applications.

In June 1948, to the surprise of his collaborators, Shockley announced the discovery of the junction transistor, which would rapidly supersede the Bardeen-Brattain point-contact transistor for the majority of commercial applications of solid-state amplifiers. The discovery of the transistor was soon considered one of the major technological advancements of the 20th century, and transistors became ubiquitous in the matter of a few years. For this momentous discovery, Bardeen, along with Brattain and Shockley, was awarded the Nobel Prize in Physics in December 1956. The BCS theory of superconductivity Notwithstanding the enormous success of the transistor, the working environment at Bell Labs rapidly deteriorated because of Shockley’s behaviour following Brattain and Bardeen’s invention of the point-contact transistor. Bardeen decided to dedicate himself to the theoretical understanding of superconductivity, which was one of the most important open problems of solid-state physics. The Dutch physicist Heike Kamerlingh Onnes—one of the pioneers of low-temperature physics—discovered the phenomenon of superconductivity in his laboratory in Leiden on April 8, 1911.

Kamerlingh Onnes’ collaborator Gilles Holst observed that the resistance of a solid mercury wire went abruptly to zero at 4.2 K. In his 1913 Nobel lecture, Kamerlingh Onnes emphasised the importance of the discovery maintaining that mercury had “entered a new state,” which he christened superconductivity. Further experiments showed that various metals and alloys became superconductors once they were cooled below the critical temperature, which depended on the material. In 1913, another important property of superconducting states was discovered: Superconductivity disappeared once the material was immersed in a sufficiently strong magnetic field. After the development of quantum mechanics, many of the pioneers of the novel theoretical framework, along with their students and younger associates, saw the properties of solids as a natural field for the application of the quantum theory to complex systems, in which the interactions between many particles played a major role. Between 1928 and 1933 important progresses in the quantum theoretical understanding of solid-state physics were made. A. Sommerfeld, W. Heisenberg, W.

Pauli, along with their PhD students and research associates, put forward many of the building blocks of the theory of solids on the basis of the laws of quantum mechanics and their applications to the interactions between the ionic lattice and the electrons. Since 1929, superconductivity was considered a fundamental part of the research programme aiming at the quantum theory of solids, and there was much hope that a reliable microscopic theory of superconducting states would shortly emerge. Between 1929 and 1933, more than a dozen theoretical physicists, including founding fathers of quantum mechanics such as N. Bohr, Pauli and Heisenberg and brilliant younger experts of the application of the new theory to the properties of solids, like F. Bloch and L. Landau, tried to put forward a microscopic theory of superconductivity. But all these attempts failed. In 1933, superconductivity still maintained the status of an unsolved problem, while many other many-body phenomena had been successfully dealt with in the quantum mechanical framework. In 1933, the German physicists W. Meissner and R. Ochsenfeld discovered that a material in the superconducting state was a perfect diamagnet.

It was soon recognized that the Meissner effect—as the expulsion of weak magnetic fields from a superconductor when it is cooled below the critical temperature was shortly baptised—was a fundamental feature of the phase transition between normal and superconducting states. To many, perfect diamagnetism seemed the best way to characterize the superconducting states rather than the vanishing resistance. The discovery of the Meissner effect, indeed, led to the development of the first successful phenomenological theory of superconductivity put forward by the German physicists Fritz and Heinz London in 1935, which, a posteriori, was regarded as a major step towards the theoretical understanding of the phenomenon. Of Jewish family, the London brothers had recently fled from Nazi Germany and begun working at the Clarendon Laboratory in Oxford, where they collaborated with other refugees in the establishment of the first Oxford low-temperature physics programme. The London theory was based on a two-fluid model—according to which electrons were separated in normal and superconducting, and the proportion between them depended on the temperature—and an equation relating the superconducting current density and the vector electromagnetic potential A within the superconductor, for an appropriate choice of gauge (the Coulomb gauge divA=0).

The combination of London and Maxwell equations explained various properties of superconductors including the vanishing resistance and the exponential decay of the magnetic field inside the superconductor with a characteristic penetration depth. In the diamagnetic picture provided by the London theory, supercurrents were determined by the magnetic fields and were metastable phenomena; i.e., configurations in which the system spent an extended time, but that were different from the state of least energy of the system. To provide some microscopic grounds to their phenomenological theory, the London brothers hypothesised that the ground-state wave function of a superconductor remained independent (“rigid” as they defined it), at least to a first approximation, from an impressed weak magnetic field. Although the London theory provided a phenomenological account of some of the most relevant properties of superconducting states, it was considered largely unsatisfying for several reasons. From the experimental perspective, the London theory did not account for the different empirical properties of the various metals and alloys that showed the property of superconductivity. On the theoretical side, the necessity was strongly felt to find a microscopic theory of superconductivity based on quantum mechanical laws. Significant theoretical advancements occurred only after World War II.

In 1950, building on his theory of general second order phase transitions, the Soviet theoretical physicist Lev Landau along with Vitaly L. Ginzburg proposed a theory of superconductivity based on the power series expansion of the free energy difference between normal and conducting states in a complex order parameter ω, which was defined so that ω is 0 in the normal state, while ω=1 in the superconducting state at T=0°K. The order parameter was identified as the square of an effective wave function ψ, defined so that the absolute value of ψ2 was equal to the density of superconducting electrons. By minimizing the free energy, Ginzburg and Landau derived a series of equations relating the order parameter, the supercurrent and the vector potential. The Ginzburg-Landau equations allowed for the treatment of the boundary between normal and superconducting regions. Moreover, it was the first theoretical approach to suggest that there were two different kinds of superconductors, with different reactions with respect to the applied magnetic fields.

As was later recognized, type-I superconductors were those superconductors in which the superconducting phase is abruptly destroyed as soon as the applied magnetic field reaches a certain critical value. In type-II superconductors, instead, there is an intermediate phase characterised by the formation of magnetic vortices when the magnitude of the applied magnetic field lies between two different critical values H1 and H2, while the material comes back to the normal state for values of the magnetic field greater than H2. On the experimental side, several groups made important progress in the clarification of various aspects of the phenomenon, including the correlation between penetration depth and amount of impurities, and the relations between the transition temperature and the isotopic mass of atoms in the lattice. In 1950, two experiments carried out in the United States to explore the latter point by measurements on samples of different mercury isotopes showed a surprising result. There was a proportional relation between the critical temperature and the mass of the isotopes: The value of the critical temperature varies inversely with the square root of the mass of the atomic lattice.

This isotope effect—as the experimental finding was shortly named—suggested that the phenomenon of superconductivity depended on the coupling between conduction electrons and the lattice vibrations. This latter result was instrumental in revitalising Bardeen’s interest in superconductivity. Unsatisfied with the working environment at Bell Labs, where there was scant interest in supporting theoretical research on superconductivity, Bardeen decided to pursue an academic career, accepting a professorship at the University of Illinois at Urbana-Champaign in 1951. There, he carried on the project to develop the microscopic theory of superconductivity with various collaborators. Bardeen began exploring the techniques developed by D. Bohm and D. Pines to treat the electron-electron interactions in plasmas. From 1951 to 1953, Bohm and his graduate student Pines had published a series of important papers on the collective behaviour of electron-electron interactions providing the building blocks for the theoretical description of the quantum electron gas. Bardeen was successful in securing Pines as his postdoctoral assistant at the University of Illinois.

With Pines, Bardeen worked on the extension of the Bohm-Pines theoretical framework to the description of superconducting states by taking into account the ionic motion. After having developed their formalism for the phonon-electron interaction, Bardeen and Pines showed that, for interactions in which the energy transfer was small, the coupling of lattice vibrations and electrons resulted in an attractive force between electrons that overcomes the screened Coulomb repulsion, suggesting in this way a microscopic mechanism for superconductivity. In 1953, Bardeen was asked to write a review on the theoretical research on superconductivity for the recently established series Handbuch der Physik edited by S. Flügge. At that time, Bardeen was already convinced that the properties of superconducting states might be derived by means of a reasonable energy-gap model, a model that implies an energy gap between the superconducting ground state and the single electron first excited state. Bardeen’s work on the long review allowed him to deeply study all the available scientific literature on the theory of superconductivity.

In his 96-page long article Bardeen stated that it was necessary to put forward “radically new ideas” to get a good physical picture of the superconducting states. Bardeen was determined in developing the new theory and the needed novel concepts with his group. In particular, he was recognizing that field theoretical techniques could be the right theoretical tools for the description of the quantum Fermi gas in superconductors and its interconnection with the ionic lattice. The new quantum electrodynamics developed by the late 1940s was a model on which one could perhaps rely in order to describe superconductivity in quantum field theoretical fashion. To achieve this target, Bardeen brought to Urbana as a postdoctoral associate Leon Cooper, who had recently completed his PhD on theoretical nuclear physics. Cooper joined the Bardeen group soon after Pines had left the University of Illinois in 1955 to accept a teaching position at Princeton. The third member of the small group working on superconductivity was J. Robert Schrieffer—a graduate student who was pursuing his PhD under Bardeen’s supervision. After the group joined their talents, they were able to make quick progress in the matter of months.

The first important step towards the resolution of the problem was made by Cooper in 1956. Cooper demonstrated that if the net force between two electrons lying outside the Fermi surface is attractive, then the two electrons form a bound state separated by an energy gap from the continuum state however weak the attractive force might be. The Cooper pairs—as Copper’s result was shortly christened—were considered as a possible essential ingredient of the microscopic theory of superconductivity. It was, however, still necessary to find a many-body wave function that took into account the large number of overlapping electron pairs. While Bardeen was travelling in Europe to receive his Nobel Prize for the discovery of the transistor he gave his co-workers the task to find the ground state wave function of superconductors with Cooper pairs. In January 1957, Schrieffer solved this problem while riding on a subway in New York City. He wrote down a many-body wave function as a product of creation operators acting on vacuum, which gave terms with changing total number of Cooper pairs. The BCS theory of conductivity was born.

After Schrieffer announced his result when Bardeen came back from Sweden, the three physicists began applying the new theory to a series of specific cases to check if the theoretical predictions were confirmed by the empirical data. Bardeen decided to publish a short letter with the outline of the theory in Physical Review in order to secure priority for their discovery, even though they had not been able to derive the second-order phase transition between the normal and superconducting states at the critical temperature. Bardeen was invited to present the theory to the March 1957 meeting of the American Physical Society, but he decided to send Cooper and Schrieffer, because he did not want to overshadow his collaborators and wished that the young people got the right credit. (Eventually, the two talks were presented by Cooper alone, because Schrieffer could not arrive in time). After further progress had been made and some experimental confirmation had increased the confidence of the authors in their theory, Bardeen, Cooper and Schrieffer published the 30-page version of their discovery in the paper “Theory of Superconductivity,” published in Physical Review on December 1, 1957.

By the time the paper was printed, the essential elements of the theory were already known, and several debates on its validity had taken place in various settings. Notwithstanding its immediate success, the theory was not well received by other theoreticians. Some of the terms in the theory seemed unsound from a physical perspective, and it required some years before the physical implications of the theory were fully understood, especially in terms of broken symmetry—a perspective that was not explicitly present in the original papers by Bardeen, Cooper and Schrieffer. After the theory had finally gained consensus within the physics community and the BCS theory had also become a model for the application of symmetry breaking to particle physics, Bardeen, Cooper and Schrieffer were awarded the Nobel Prize in Physics in 1972, “for their jointly developed theory of superconductivity, usually called the BCS-theory.” A career between academia and industry After having left the Bell Labs for a professorship at the University of Illinois, Bardeen did not completely abandon the world of industry. This was perfectly coherent with Bardeen’s general view that the most meaningful scientific researches were those that promised of having practical applications.

He continued to maintain a series of working connections with industrial firms, especially with the Haloid Company of which he was a scientific consultant from 1952 onward. In 1961—the year in which Haloid was renamed Xerox Corporation—Bardeen became a member of its board of directors. He eventually stepped down from all his roles within the firm in 1980 after almost thirty years of strong commitment to the technological innovations and long-terms goals of the company. When he was already recognized as one of the most outstanding American physicists working on theoretical physics devoted to useful practical applications, Bardeen was asked to serve in national advisory panels. Among other duties, from 1959 to 1962, he served as a member of the President science Advisory Committee of D. Eisenhower and J. F. Kennedy. Notwithstanding his hesitancy, Bardeen was also convinced to sit in President Reagan’s White House Science Council from 1981 onward, but he rapidly resigned after Reagan began the missile program called Strategic Defence Initiative (SDI) without consulting the Council.

On the scientific side, after the development of the BCS theory and its acceptance as the most valuable microscopic theory of superconductivity, Bardeen became one of the most influential authorities in solid-state physics and his opinions had a major impact in various debates about further discoveries about many-body problems. During the 1980s, he became primarily interested in the development of a new quantum mechanical theory of charge density waves (CDWs)—a periodic modulation of the electronic charge density. According to Bardeen, the CDWs might be explained as a macroscopic quantum phenomenon on the same ground as superconductivity. While initially interested in Bardeen’s theory, the condensed matter community eventually came to prefer more classical approach to the CDWs, which led to a predictable relationship between the level of impurities and the threshold voltage above which the sliding of the CDWs occurs. This evaluation of his theory led Bardeen to feel increasingly isolated in the community he had contributed to shape. He continued to publish papers on the theoretical description of CDWs and on the newly discovered phenomenon of high-temperature superconductivity till January 1991, when he died of massive heart attack at the age of 82.

Bibliography Bardeen, J (1956) Theory of Superconductivity. Theoretical Part, Handbuch der Physik 15: 274-369. Bardeen, J. (1956) Nobel Lecture: Semiconductor Research Leading to the Point Contact Transistor. Nobelprize.org. Nobel Media AB 2014. Retrieved 10 December 2014. Bardeen J. (1972) Nobel Lecture: Microscopic Quantum Interference Effects in the Theory of Superconductivity. Nobelprize.org. Nobel Media AB 2014. Retrieved 10 December 2014. John Bardeen - Biographical. Nobelprize.org. Nobel Media AB 2014. Retrieved 16 December 2014. Hoddeson, L. (1981) The Discovery of the Point-Contact Transistor. Historical Studies in the Physical Sciences 12: 41–76. Hoddeson L.

(1981) The Emergence of Basic Research in the Bell Telephone System, 1875–1915. Technology and Culture 22: 512–544. Hoddeson L. (2008) Bardeen, John. Complete Dictionary of Scientific Biography. Encyclopedia.com. (retrieved December 10, 2014). Hoddeson, L., Braun, E., Teichmann, J., & Weart, S. (eds.) (1991) Out of the Crystal Maze: Chapters from the History of Solid-State Physics. Oxford University Press, New York. Hoddeson, L., and Daitch, V. (2002) True Genius: The Life and Science of John Bardeen. Joseph Henry Press, Washington, DC. Riordan, M., and Hoddeson, L. (1997) Crystal Fire: The Birth of the Information Age. W. W. Norton, New York. Schrieffer R. (1972) Nobel Lecture: Macroscopic Quantum Phenomena from Pairing in Superconductors. Nobelprize.org.

Nobel Media AB 2014. Retrieved 10 December 2014. Cite

Question: What did Bardeen, Shockley and Brattain invent in 1947, and for which they were awarded the Nobel Prize for Physics in 1956?
Answer: TRANSISTOR