N. Bruce Hannay

N. Bruce Hannay. Courtesy the Electrochemical Society (ECS).

N. Bruce Hannay. Courtesy the Electrochemical Society (ECS).

The invention of the transistor in 1947 ushered in the modern age of microelectronics. Prior to this, the basic electronic device was the electron tube, or vacuum tube, and electronic devices were quite large compared to what we have today. The effort to continually shrink the size of electronic components, allowing for smaller and more powerful devices, is the field of microelectronics. It started with trying to develop better and smaller vacuum tubes, but soon shifted away from vacuum tubes altogether to transistors made from semiconductors. Semiconductors, such as germanium and silicon, are substances that fall somewhere between good conductors and poor conductors, and have special properties that make them excellent for use in electronic devices. They allow but still resist the flow of electricity. By the end of the 1950s, transistors had replaced hot, unreliable vacuum tubes in nearly every type of electronic system, making devices smaller, cooler, and less expensive. Chemists like N(orman) Bruce Hannay (1921–1996) made a profound contribution to microelectronics as this transition from vacuum tube to transistor progressed.

Hannay came from a family of bankers—grandfather, father, and uncles. Unfortunately, his father was killed in an accident shortly after the family left the small town of Mount Vernon, Washington State, for Seattle. But banking held no attraction for Hannay. Instead he fell in love with the possibility of becoming a chemist. His teachers at a large public high school in Seattle let him and other gifted students study ahead and do experiments on their own in the back room. He sallied forth to Swarthmore College outside Philadelphia, for the first time in his life crossing the Mississippi River, intent on completing a chemistry major. He then proceeded to Princeton University for a Ph.D. in physical chemistry, which he completed in 1944.

During World War II, Hannay worked on gaseous diffusion for the Manhattan Project at nearby Bell Laboratories. His first civilian project at Bell Labs was to investigate the mechanism by which electrically charged particles are emitted from the incandescent cathodes of vacuum tubes. But at the end of 1947 Hannay’s colleagues at Bell Labs—Walter H. Brattain, John Bardeen, and William B. Shockley—invented the transistor, and Hannay’s research program changed radically to support the development of this new invention.

Hannay’s new job was to develop a mass spectrograph (see J. J. Thomson) to analyze solids for trace impurities, ensuring a high level of purity in the semiconductors used to make the new transistors and, later, integrated circuit chips. Then he was chosen to lead both chemical and physical aspects of Bell’s silicon program. Although the first transistors were made from germanium, industry soon targeted silicon, with its lower cost and potential for developing a good oxide layer. To avoid contact with any other substance that would contribute impurities to silicon, Hannay’s group devised a method of growing silicon crystals in a vacuum, relying on mere surface tension to suspend the crystals. (This method is still used to make substrates for integrated circuit chips.) In 1953 Bell Labs and Texas Instruments simultaneously heralded the arrival of the silicon transistor.

Through the 1950s Hannay and his colleagues investigated other semiconductors, including gallium arsenide, the preferred material for semiconductor lasers, which are the basis for optical communication systems and have many other purposes today.

Hannay eventually rose to the position of vice president for research and patents at Bell Labs. He was a member of both the National Academy of Sciences and the National Academy of Engineering and won the prestigious Perkin Medal from the Society of Chemical Industry.

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