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Note after publication:

The October 2012 issue of physica status solidi (b) was dedicated to the 90th birthday of Stanford Robert Ovshinsky. After the publication of the online version of the special issue, sad news came: on 17 October 2012, Stan Ovshinsky passed away, a month short of his 90th anniversary. - Read the Obituary in the November issue [Phys. Status Solidi B 249(11), 2055–2056 (2012)].

To Stanford R. Ovshinsky, a brilliant scientist and a great inventor, in honour of his pioneering contributions to the science and technology of disordered materials and his compassion to create a better world through science and technology.

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This issue is dedicated to Stanford Robert Ovshinsky, a pioneer of science and applications of disordered materials. Stan appreciated the importance of disordered materials in the mid 1950 s, when most scientists did not believe that amorphous semiconductors could exist. Being ahead of his time, he was often criticised for his novel ideas which were initially denigrated but later proved valid. In the late 1950 s–early 1960 s, Stan observed reversible switching phenomena in certain compositions of chalcogenide glasses which, depending on the composition of the material used, resulted in either a dynamic (threshold switch) or a stable (memory device) change in conductivity. This effect is now known as the Ovonic effect and the word Ovonics appears in many dictionaries. The Merriam–Webster dictionary defines Ovonics as a branch of electronics that deals with applications of the change from an electrically nonconducting state to a semiconducting state shown by glasses of special composition upon application of a certain minimum voltage.

The invention of the phase-change memory, which has been commercially implemented as re-writable optical discs such as digital versatile discs and is now the leading candidate to replace flash memory, is just one of Stan's numerous inventions. His other inventions that revolutionised our lives relate to flat-panel displays, hydrogen storage materials, thin-film solar cells and the nickel-metal hydride battery, to name a few. His current goal is to make solar power cheaper than coal.

It is astonishing that all this has been achieved by an individual without a university education. Or was it thanks to the absence of the established way of thinking that allowed him to see what others could not? Stan is often compared to Thomas Edison but this is only partially true. The great Nobelist I. I. Rabi said in an interview, which appeared in the Nova television program Japan's American Genius: “Stan is not an Edison; he is an Ovshinsky – a brilliant scientist!” What he meant was that Edison was usually considered as a great inventor, but not a scientist, Ovshinsky is both. As a brilliant scientist and a great inventor, he laid the grounds for important advances of science and technology of the 21st century.

Another fascinating thing about Stan is his charisma that attracts people into his sphere and leads to the establishment of life-long friendships. His continuous compassion to create a better society attracts not only scientists but people of different professions who share his great humanistic ideas. In his office at the Institute of Amorphous Studies that he founded back in the 1980 s, there are dozens of photographs of his numerous friends and admirers ranging from Nobel Prize winners to prominent political figures.

For the most part of Stan's life his closest friend was his wife Iris, the great woman next to the great man. After her tragic death in 2006, Stan is supported with dedication by Rosa Young, now Rosa Ovshinsky, without whom, Stan admits, he could not live further.

A person like Stan may be written about on hundreds of pages and his biography is yet to be published, but the space for this introduction is limited and we have to stop here. We would like to especially encourage the audience to read the two memoirs papers by Hellmut Fritzsche and Genie Mytilineou included in this issue that describe Stan's great personality (see pp. 1827–1834) , as knowing and understanding his way of life is crucial to appreciate fully his scientific and technological achievements.

Scientific papers in this issue are written by Stan's admirers and followers and represent the latest progress in the field of science and applications of amorphous chalcogenides. The issue sets in with the two already mentioned memoirs papers followed by a description of the Ovshinsky award for excellence in amorphous chalcogenides. The scientific part of the issue starts with Feature Articles by Noboru Yamada, Matthias Wuttig, and by J. Akola and R. O. Jones, describing recent progress in the physics and applications of phase-change materials. The subsequent part of the issue presents Original Papers on phase-change materials and on chalcogenide glasses, starting with basic research papers followed by the description of applied results, respectively. The authors address various aspects of the phase-change phenomenon such as the role of electronic excitation, the origin of the property contrast, and emerging topological insulator behaviour. Structure and properties of the disordered phase remain an important issue including such aspects as fragility of the liquid phase, crystallisation, and the local structure of Ge atoms. Local and global structures of the crystalline phase, including epitaxially grown layers and multilayered structures also continue to attract attention. Several papers are dedicated to threshold switching whose mechanism remains a matter of debate despite years of studies. On the application side, of special interest is the experimental demonstration that phase-change materials can be used for cognitive computing. Papers describing a successful use of phase-change alloys for PC-RAM devices, including the search for new materials, conclude this part of the issue. The remaining papers are devoted to chalcogenide glasses where structure and defects as well as photo-induced phenomena and Ag-diffusion are discussed. An interesting new application of chalcogenide glasses reported in this issue is their use for the photoalignment of liquid crystals using the effect of photo-induced anisotropy.

On behalf of all authors, we would like to use this occasion to wish Stan a happy 90-year birthday and many happy returns of the day, to express to him our sincere gratitude for his great contributions to the field, and wish him new achievements on his demanding and challenging road to better the world through science and technology.

Note after publication:

The October 2012 issue of physica status solidi (b) was dedicated to the 90th birthday of Stanford Robert Ovshinsky. After the publication of the online version of the special issue, sad news came: on 17 October 2012, Stan Ovshinsky passed away, a month short of his 90th anniversary. - Read the Obituary in the November issue [Phys. Status Solidi B 249(11), 2055–2056 (2012)].