This Week’s Citation Classic________Ovshlnsky S R. Reversibleelectricalswitchingphenomenain disorderedstructures.

Phys.Rev.Lett. 21:1450-3,1968.tEnergyConversionDevices,Inc., Troy, MI]

A rapid reversible transition between ahighly resistive and conductive state effect-ed by an electric field, which we have ob-served in various types of disordered semi-conducting material, is described. Theswitching parameters and chemical compo-sition are presented, and microscopic mech-anisms for the conduction phenomena sug-gested. [The SCI® indicates that this paperhas been cited over 410 times since 1968.]

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Stanford R. OvshinskyEnergy Conversion Devices, Inc.

1675 West Maple RoadTroy, Ml 48084

“When I started my work in amorphousmaterials, crystalline symmetry was the sinequa non of solid-state physics. Amorphousmaterials were considered to be, if theywere considered at all, ununderstandable,unusable, and unimportant.

“My 1968 paper had its origins in work Ihad started in 1955 to understand how exter-nal energy events could be transformed in adisordered material into detectable infor-mation. I was particularly interested in un-derstanding neuronal mechanisms.

“1 made models in 1958 which I thoughtcould have analogous mechanisms demon-strating energy conversion processes innerve cells and how they affected switchingevents and information encoding. The keywas to understand surface phenomena in-volving disorder, and, therefore, I con-centrated on amorphous materials, In 1960,my wife, Iris, and I founded Energy Conver-sion Laboratories to work in amorphous ma-terials in both the energy and informationfields, feeling that they were thermodynami-cally the opposite sides of the same coin.We built chalcogenide devices chosen fortheir biological-like, more flexible, helical

structures. We made thin film, rapidly re-versible threshold and memory deviceswhich changed from insulating to conduct-ing upon the application of an electric field.In the memory, either state remained indefI-nitely without sustaining power.

“Using a polymeric chemical approach. Iwas able to design materials in which anelectronic switching action could take placein a thin film of less than one micron ofamorphous material at speeds faster thanany oscilloscopes we had-—that is, thepicosecond range.

“As my patents started issuing, I dis-cussed my work at international meetings,and through my -collaborator, HellmutFritzsche, University of Chicago, we interest-ed Sir Nevill Mott in this area. My col-leagues urged me to publish what they feltwas a very important effect and open up anunderstanding of what was considered thelast frontierof solid-state physics, the amor-phous state.

“At the time of publication, we an-nounced our results at a small press confer-ence. The New York Times1

and the Wa/IStreet Journal2 checked with prominentscientists and gave us important coverage.There was a furious reaction from crystal-line-based companies. However, our workcontinued and expanded, and the amor-phous field is now fully accepted and rapid-ly growing. A Nobel prize was given in amor-phous materials to Mott only nine yearsafter the attempts to discredit the validity ofamorphous materials. Our field has gonefrom early international conferences ofabout 30 people with no proceedings to themost recent one with over 500 people fromover 40 countries and two volumes of pro-ceedings.

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“The terms ovonic, Ovonics, and Ovshin-sky effect are in many major dictionaries. In1968, I received the Diesel Cold Medal forInvention for my work, and have recently re-ceived several honorary degrees.

“I believe that this paper was quoted sofrequently because it was contrary to theconventional wisdom of its time and yetturned out to be right in its findings andimplications, creating a great impetus foramorphous materials research.”

I. StevensW K. Glassy electronic devicemay surpass transistor. NY Times 11 November 1968. p. 1,42.2. NøcoIakifG A. Recognition has arrivedlike a tidal wavefor inventor.45.of the ‘glass transistor.’

Wall Ssreeil.14 November1968,p.?.3. OwablnskyS R. Principles and applications of amorphicity, structural change, andoptical information

encoding. Proceedings of theNinth 1~te,-no:ionalConference on Amorphous& LiquidSemiconductors.Grenoble,France,2-8July 1981.To be publishedin Journalde Physique. -

18 PC&ES CURRENT CONTENTS®©1982bylSl®

December 9, 1981

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