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PCM also has the ability to achieve a number of distinct intermediary states, thereby having the ability to hold multiple bits in a single cell, but the difficulties in programming cells in this way has prevented these capabilities from being implemented in other technologies (most notably flash memory) with the same capability. Newer PCM technology has been trending in a couple different directions. Some groups have been directing a lot of research towards attempting to find viable material alternatives to Ge2Sb2Te5 (GST), with mixed success, while others have developed the idea of using a GeTe - Sb2Te3 superlattice in order to achieve non thermal phase changes by simply changing the coordination state of the Germanium atoms with a laser pulse, and this new Interfacial phase change memory (IPCM) has had many successes and continues to be the site of much active research.
Phase-change memory (also known as PCM,PCME, PRAM, PCRAM, Ovonic Unified Memory, Chalcogenide RAM and C-RAM) is a type of non-volatile random-access memory. PRAMs exploit the unique behavior of chalcogenide glass. In the older generation of PCM heat produced by the passage of an electric current through a heating element generally made of TiN would be used to either quickly heat and quench the glass, making it amorphous, or to hold it in its crystallization temperature range for some time, thereby switching it to a crystalline state.
"These binary waveforms use three levels, instead of two, to encode the binary data.
- Di code-NRZ: Pulse is full bit interval wide, a data transition: one-to-zero or zero-to one, changes pulse polarity without a data transition, the zero level is sent.
- Di code-RZ: Pulse is half-bit interval wide, a data transition: one-to-zero or zero to- one changes polarity of transmitted pulse. Without a data transition, the zero level is sent.
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