Phase-change non-volatile memory structure concept (via University of Cambridge)
Chemical engineers from the University of Cambridge recently released a paper detailing a significant increase in speed for phase-change non-volatile memory (PCRAM). Phase-change memory has a distinct advantage over flash memory, it can write bits faster without the need to erase huge chunks of data beforehand. Degradation (or cell damage) is also a factor for both mediums over time; however phase-change memory can withstand roughly 100,000,000 write cycles as opposed to flash memory’s 5,000 writes per sector before noticeable damage starts to occur. PCRAM works by passing an electric current over chalcogenide glass making it transition between two states when heat is applied, crystalline to amorphous. This transition happens almost instantaneously which gives the memory an increase in speed over conventional flash memory. However, most of today’s PCRAM modules crystallize slower than it takes to write 1-bit of data for their DRAM counterparts (1 to 10 nano-seconds), not to mention that the heat needed to crystalize PCRAM tends to transition back to its organized state at room temperature (data erasure over time).
In an effort to overcome these limitations, the UOC’s engineers have figured out a way to not only counter the effect of data-loss at room temperature but also increase the speed of PCRAM, as well. To achieve their results, the team was able to achieve the PCRAM’s stability at room temperature using a weak electric field of 0.3 volts generated by 2 titanium electrodes placed in between the germanium, antimony and tellurium layers of the phase-change medium. They then found that they only needed a 500 picosecond jolt of 1 volt in order to cause crystallization, which is 10-times faster than previous PCRAM modules. They tested their findings by using a 6.5V jolt to continually erase data and found the PCRAM to be stable and damage resistant over the course of 10,000 re-writes. The team states that this development "could pave the way for mobile devices that could transfer non-volatile data at speeds over 1GHz." (0.3V refresh isn't quite "non-volatile," but it is a beginning.)