Sunday, June 3, 2007

43. Semiconductors

1 comment:

Mark said...

semiconductor section

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Amorphous semiconductor materials

In the 1950s, Stanford Ovshinsky created an entirely new realm of materials science, which in turn has given new life to the engineering of semiconductors, solar energy, and electric cars.

Stan Ovshinsky was born in Akron, Ohio in 1922. After graduating from high school, he went straight to work. In 1955, he began working the field of amorphous materials, that is, materials that lack a definite crystalline structure. Ovshinsky was the first engineer to devise a method, called "phase change," for crystalizing these disordered materials, with resulting novel uses: for example, films that gain metallic properties without losing their original optical capabilities. One result was amorphous semiconductors --- which the engineering community had previously considered an utter impossibility.

In 1960, Ovshinsky founded Energy Conversion Devices, Inc. (ECD), in order to continue and expand his work in amorphous semiconductors. Meanwhile, engineers nationwide had eagerly entered an entirely new field: "ovonics" (from Ovshinsky Electronics).

Ovshinsky earned numerous patents in the 1970s and '80s for amorphous semiconductor materials. These materials became essential to optoelectronic copying and fax machines, as well as large, flat-panel liquid crystal displays like those of computer monitors. As early as 1970, Ovshinsky had used his ovonic phase change principle to invent a reversible optical memory disk: that is, a prototype rewritable CD-ROM. Today, thirteen high tech companies around the world are developing rewritable CDs using Ovshinsky's technology.

Ovshinsky went on to use his thin-film amorphous silicon to invent a manufacturing method that might do for solar energy what the assembly line did for automobiles. In 1983, he patented a system that allowed photovoltaic solar panels to be manufactured in continuous rolls 1000 feet in length. Ovshinsky's "Continuous Amorphous Solar Cell Production System" operates much like a newspaper rollpress, speedily imprinting a plasma of amorphous silicon semiconductors in a continuous web onto a thin, anodized metal sheet.

The high energy-conversion efficiency of the thin-film cells and the high throughput of the process make Ovshinsky's photovoltaic cells a revolutionary leap forward for solar energy. They have been installed at various sites around and above the globe, from Mexican mountain villages to the Mir space station. Ovshinsky's "Uni-Solar" roofing tiles, for residential buildings, have won Popular Science's "Best of What's New" Grand Award (1996) and Discover Magazine's Discover Award in the Environment category (1997).

More recently, Ovshinsky has taken a strong step closer to a feasible electric car. After years of development, he earned a patent in 1994 for a high energy-storage, environment-friendly, maintenance-free, rechargeable battery. Although he is far from alone in the search for the perfect electric car battery, Ovshinsky's nickel metal-hydride (NiMH) model, when compared with its nickel-cadmium and lead-acid competitors, is twice as powerful, with none of their fatigue and discharge problems. In fact, Ovshinsky's battery shattered the Department of Energy's performance targets. Recently, ECD formed a joint venture with GM, whose EV1 features Ovshinsky's NiMH battery, to mass produce the battery for electric cars worldwide. A more modest version of the NiMH battery has been licensed by many of the world's major battery companies for retail consumption.

In total, Stan Ovshinsky has earned about 200 US patents, at a pace which has not flagged since the early 1970s: eight granted in 1999, and three more by February 1 of this year. He has also won many local, national and international awards for his work, which extends far beyond the products described above; and he will doubtless win further fame, as the once impossible products he has invented come into broader use.

[March 2000]