Professor of Physics Emeritus, The University of Chicago, IL, USA
Stanford R. Ovshinsky – A sketch†
Version of Record online: 1 OCT 2012
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
physica status solidi (b)
Special Issue: Phase-change memory: Science and applications
Volume 249, Issue 10, pages 1827–1830, October 2012
How to Cite
Fritzsche, H. (2012), Stanford R. Ovshinsky – A sketch. Phys. Status Solidi B, 249: 1827–1830. doi: 10.1002/pssb.201200574
Dedicated to Stanford R. Ovshinsky on the occasion of his 90th birthday
- Issue online: 8 OCT 2012
- Version of Record online: 1 OCT 2012
- Manuscript Accepted: 14 AUG 2012
- Manuscript Received: 12 AUG 2012
- amorphous semiconductors;
- chalcogenide glasses;
- flexible solar panels;
- hydrogen storage;
- nickel-metalhydride batteries
Some path breaking inventions of Stan Ovshinsky that benefitted society will be described. His electrical phase change memories are entering the market, poised to be used in many devices. His optical phase change memories are used in rewritable digital video discs. His pioneering work in thin film electronics led to flexible and light solar panels. His Nickel-metal hydride batteries are the enabling batteries for hybrid and electric vehicles. His new alloys allow safe and efficient transport, storage, and release of hydrogen, satisfying the needs of a future hydrogen economy. His work has opened non-crystalline semiconductors as a new field of material science.
1 The many reasons for celebration
This special volume honors an unusually creative person, a prolific inventor, a superb scientist, a successful entrepreneur and an admirable human being, Stanford R. Ovshinsky. In these few pages I will try to give a glimpse into the rich and productive life of this unique person. Any such attempt will fall short but not doing it will leave a void in this collection dedicated to him. A richer and more detailed portrayal of Ovshinsky can be found in a recently published book that explains the new ideas that led to the broad spectrum of his inventions 1.
As you know, Ovshinsky's discovery in the early 1960s of the switching and phase change memory effects in chalcogenide glasses opened a new field of material science. According to the textbooks of that time, amorphous semiconductors could not exist at all. A periodic crystalline arrangement of atoms is, we believed and taught, the prerequisite of semiconducting properties. One had never heard of chalcogenide glasses. How can one understand the electronic properties of non-crystalline materials comprising three, four, or even five elements? One did not even know where the atoms were located in these novel glasses and all the physical concepts commonly used in solid state physics applied only to ordered periodic structures.
When I met Ovshinsky in 1963 I saw on his oscilloscope the current–voltage characteristic of two wires covered with his new material, a chalcogenide glass, as seen in Fig. 1 photograph. One remarkable feature is the symmetry for negative and positive voltages.
John Bardeen was astonished when he heard about this. Ovshinsky remembered Bardeen saying: “this is absolutely new; there is no solid state device that behaves the same for both polarities of the voltage.” This and the unique feature of reproducible and repeatable changes between amorphous and crystalline phases of select groups of chalcogenide compositions identified by Ovshinsky caught the solid state community by surprise. The success of the transistor and of silicon technology had persuaded solid state scientists that purified semiconducting crystals with controlled doping were the only ones worth studying. Ovshinsky's discoveries made scientists aware of a huge gap in the understanding of materials in general.
Ovshinsky's small laboratory became a sort of Mecca for those scientists drawn to the challenge of exploring this virgin territory (see Fig. 2). Ovshinsky always believed that progress could be achieved in any field only by thoroughly understanding the materials. New exciting physics emerged under his leadership and new concepts for understanding electronic transport and excitations in amorphous materials were formulated. A novel defect chemistry in glasses with defects having negative correlation energies was discovered based on Ovshinsky's emphasis on the importance of lone pair electrons for understanding chalcogenides.
Ovshinsky's work on switching and memory devices followed his attempt to build a mechanical model of a nerve cell, an effort that grew out of his interest in smart machines and of the nature of intelligence more generally. Years later the circle nearly closed with his proposal of a cognitive computer using these devices (in the meantime highly miniaturized) capable of three-dimensional stacking and offering multi-level information storage. His advanced three terminal devices offer a way to control the switching voltage.
Ovshinsky's mind always overflowed with ideas and problems needing solutions. Over 50 years ago he first worked to develop a lithium ion battery and a fuel cell (Fig. 3).
His successful inventions of non-silver photography and rewritable microfiche information storage on metallo-organic films were unfortunately rendered obsolete by charge coupled devices and digital photography. His 400 patents include also inventions of X-ray focusing elements consisting of curved multi-film super-lattices having contrasting X-ray scattering factors, magnetic materials with ultrahigh remanence obtained by optimizing their nanostructure by cooling appropriate alloy melt at very high quench rates and hard coats that lengthen the life of cutting tools.
The switching and memory devices opened the door to thin film electronics. His vision at that time of flat panel displays and televisions “as thin as pictures hanging on the wall” were met with laughter. A few years later he filed fundamental patents for flat panel displays and demonstrated their impressive energy savings and efficiency. The present ubiquity of flat screen televisions proves how clearly he saw the future usefulness of thin film electronics.
The superior semiconducting properties of hydrogenated amorphous silicon made thin film solar cells possible. But to help solve the emerging fossil fuel crisis, which, remarkably, Ovshinsky foresaw even before 1960, Ovshinsky understood that inexpensive, large scale production of solar panels should be done using a revolutionary production process that involved depositing them on thin substrates by the mile, similar to the printing of newspapers. Using his machine tool background, he invented a new manufacturing process which in its latest form simultaneously feeds six rolls of 14 in. wide and 1.5 mile long stainless steel webs in parallel to each other through a vacuum deposition machine. In the deposition machine radio frequency plasmas are used to decompose feedstock gases to deposit each of the thin film semiconductor layers needed for the solar cell. Three solar cells responding to different parts of the solar spectrum are sequentially deposited in this way without breaking vacuum. The 0.005 in. thick stainless steel substrate allows the solar panel to be flexible and very light. Among other honors Ovshinsky was inducted into the US based Solar Hall of Fame, see Fig. 4.
Ovshinsky realized that the lithium-ion battery was dangerous because of its potential fire hazard. Two decades later, the completely safe and reliable nickel-metalhydride (NiMH) battery evolved from Ovshinsky's laboratory. Its many advantages over the lead-acid and NiCd batteries made it the preferred battery for power tools and electric vehicles. At present it is the power battery in essentially all hybrid and electric vehicles. Ovshinsky and his team met the challenges of long cycle life, of high power and energy density of this battery by utilizing multi-element metallurgy, designing a desired microstructure and porosity of the electrode materials, and taking advantage of their surface chemistry and new catalytic reactions of nanoparticles. His ideas of structural and chemical disorder for increasing the catalytic activity of surfaces were first widely dismissed. Ovshinsky dared to question scientific dogma and succeeded.
In 1996 a NiMH battery powered car, the Solectria, shown in Fig. 5, won the Tour de Sol road rally with an astonishing 373 mile range on a single charge using an Ovshinsky's NiMH battery pack.
Ovshinsky received the 2005 Innovation Award for Energy and the Environment from the prestigious magazine The Economist for “his pioneering work in the development of the high-powered NiMH battery.” He has also become the finalist for the European Inventor Award 2012 for his fundamental patent on this battery.
Ovshinsky realized that the negative electrode of the NiMH battery is a very good hydrogen storage alloy that can not only be filled with hydrogen from an electrolyte during charging of the NiMH battery but also from an outside source of hydrogen gas. This is because the surface layer with its nickel-alloy nanoparticles contains the catalytic sites that dissociate molecular hydrogen into atoms that then diffuse into the alloy matrix. By modifying the alloy to be lighter and able to release hydrogen at waste temperatures available on automobiles an ideal hydrogen storage medium was developed that is stable at room temperature without the danger of fire and combustion.
In 2007, the New York Times invited ten companies to demonstrate their hydrogen powered vehicles at the location where the Zeppelin aircraft, the Hindenburg, exploded on May 6, 1937. Ovshinsky entered the race by replacing the gas tank of a Toyota hybrid car with his hydrogen storage material and using hydrogen as fuel for the Toyota combustion engine. His converted Toyota Prius drove 190 miles with 7.9 pounds of hydrogen safely contained in two metal alloy hydrogen storage tanks. He won the competition against General Motors' HydroGen3 which carried 6.8 pounds of hydrogen compressed to 10.000 psi for a driving range of 168 miles and the Ford E-450 which carried 6.6 pounds of hydrogen compressed to 5000 psi driving 150 miles.
A common denominator of Ovshinsky's inventions is their benefit to society. When he and his wife Iris founded Energy Conversion Devices, Inc. in 1960 they vowed “to use creative science to solve societal problems,” to work for a better world. On the one hand, the use of clean renewable solar energy, his NiMH batteries and his hydrogen storage alloys enabling hydrogen powered cars, reduce a large fraction of the carbon dioxide emission problem. On the other hand, thin-film electronics incorporating three-dimensionally his advanced switching and memory devices might lead to artificial intelligence computer architecture. Ovshinsky considers energy and information to be two sides of the same coin.
The excitement caused by the discovery of high-temperature superconductivity in cuprates ignited Ovshinsky's imagination. Bose condensation and Cooper pairing were common knowledge but Ovshinsky had a special understanding of the crucial role played by d- and f- orbitals of transition metal elements and the strong effect of substituting new elements. He prepared cuprates with the addition of fluorine and obtained what was the highest superconducting transition temperature at that time of 155 K. Since only a small fraction of his material, which was fluorinated along a gradient, became superconductive, he was unfortunately not able to identify its crucial composition.
The Federation of American Scientists awarded Stan Ovshinsky the 2012 Hans Bethe Prize for his outstanding research and development of materials science that have been applied to solar photovoltaic technologies, superconductors, and electric vehicles.
How can one explain the amazing success of one person, who had to run his company, raise money for his research, build machines for manufacturing and also filed over 400 US patents? One reason, besides being extraordinarily intelligent and talented, might be the fact that no academic training confined his creative thinking to a narrow academic discipline. He combined what he needed from physics, chemistry, engineering and materials science, patent law and business administration. He is a scientist, inventor, machine builder, and entrepreneur all in one person. He probably is the only person elected Fellow of the American Physical Society and of the American Association for the Advancement of Science without a college or university education, and I bet the only person who is also a member of a trade union, The International Association of Machinists and Aerospace Workers.
He worked without the supportive backing of an established research laboratory. Self-taught and without special training he could compete with well-funded establishments of learning and industry. His library covers every important subject and contains over 20 000 volumes, each carefully annotated and alive in his remarkable memory. Figure 6 shows him in his favorite den.
His fascinating personality and unconventional insights attracted great minds with diverse expertise and broad talents as friends, supporters, and collaborators. He created a corporate culture that brought out the best in every one. People in his company felt less as employees than as collaborators participating in his thought process and sharing the excitement of his success. Most people working with him felt their lives changed to the better. He and his wife Iris encouraged and helped many employees to further their education, to widen their experience and to take greater responsibilities. Their humanistic ideals formed the foundation and every aspect of their lives.
We all join in congratulating him to his important 90th birthday and express our gratitude, respect, and admiration.
- 1The Science and Technology of an American Genius – Stanford R. Ovshinsky, edited by H. Fritzsche and B. Schwartz ( World Scientific Publishing Co., Singapore, 2008).