A focused review of the electrical conduction in phase change memory materials written by a University of Toledo physics professor was the most read article published in a recent issue of the Journal of Applied Physics.Dr. Victor Karpov, a UT physics professor since 2000, authored the article in the October issue of the journal about the recent technology called “phase change memory” to describe not only the physics behind the process, but also to chronicle the history of the discovery and efforts to better understand and perfect its underlying materials of chalcogenide glasses.
Most existing technology for computer and cell phone memory uses silicon or magnetic storages. The novel approach of phase change memory is just penetrating the market.
While the light-induced phase changes in chalcogenide glasses underlie the existing CD/DVD technology, the energetic extension to the computer phase change memory started only in 2000 by Intel based on the switching effect discovered by Stanford Ovshinsky in 1968.
Using electric pulses rather than light, it can record information by switching nano-size particles of chalcogenide alloys between their insulating and conductive phases. Phase change memory is unique in that it has a higher endurance with the ability to rerecord millions of times more than other technologies and it also is very robust.
“Even though phase change memory has been researched and improved, so too has silicon and other technology by leaps and bounds,” Karpov said. “While this is a strong and reliable form of memory storage, the market right now doesn’t support a great deal of investment in perfecting a new model when the current one is so successful.”
Karpov and his graduate students previously worked with Intel on research projects in this area; however, those now have expired due to a decrease in the demand.
The article in the Journal of Applied Physics, a publication of the American Institute of Physics, discusses the science behind the transport phenomena in glassy materials as the history of its understanding by English physicist Neville Mott and American physicist Phillip Anderson, who shared the 1977 Nobel Prize in Physics for their work on non-crystalline materials. Karpov himself has made contributions to this field since and has been recognized by Intel based on his results.
“The goal of the paper was to explain the physics, but also to put everything into perspective and appreciate where the mechanisms came from and how they evolved,” Karpov said.
Karpov came to the University from First Solar, where he was recruited by Harold McMaster as a researcher in the photovoltaics industry and he worked closely with Dr. Al Compaan, UT professor emeritus of physics. Their discovery of the red wine type of electrolyte treatments boosting solar cell efficiency, called the “red wine effect,” also received a great deal of attention and was patented.
Karpov’s current research in solar cell physics is supported by the National Science Foundation. He also continues his work on phase transformations in solid-state memory and other device physics.