Write speeds for phase-change memory reach record limits
June 28, 2012 | Source: Ars Technica
Fast phase-change (credit: D. Loke/Science)
By pre-organizing atoms in a bit of phase-change memory, information can be written in less than one nanosecond, the fastest for such memory.
With write speeds comparable to the memory that powers our computers, phase change memory could one day help computers boot up instantly.
Phase-change memory stores information based on the organization of atoms in a material, often a mixture of germanium, antimony, and tellurium (Ge2Sb2Te5 or GST). A voltage pulse heats the metal and disordered atoms in the crystal rearrange into an ordered crystal. Restoring the disordered arrangement by melting the glassy material erases the information. A computer reads each bit by detecting the lower electrical resistance of the ordered crystal.
Phase-change memory could one day replace flash memory in our cellphones, just as Samsung briefly tried in a commercial smartphone. PRAM can top the density and write times of flash memory. And like flash, PRAM is nonvolatile, meaning that it retains its information even when a device is powered off.
That makes phase-change memory an intriguing candidate to replace the volatile DRAM that powers our computers. But a computer that boots up instantly using PRAM is still a long way off, partly because the materials can’t be switched from disordered to ordered, or written quickly enough.
Most phase-change materials crystallize slower than the 1-10 nanoseconds it takes to write a bit of DRAM. And materials that crystallize faster at PRAM operating temperatures tend to naturally organize at lower temperatures too, says Stephen Elliott of the University of Cambridge. Therefore, they slowly crystallize and erase themselves over time.
Elliott and his colleagues have boosted the crystallization time, and thus the write speed, of a stable PRAM bit. They pre-organized the atoms in a chunk of Ge2Sb2Te5 using a weak electric field. The scientists sandwiched a 50nm-wide cylinder of GST between two titanium electrodes and applied 0.3V of potential across the material. A 500-picosecond burst of 1V electrical potential triggered the crystallization, which is about 10 times faster than the best speed using a germanium-tellurium material.
Comments (3)
by Chrispium
Planetary Resources are not likely to be able to bring to market industrial amounts of rare metals in the next couple decades.
If it was that easy NASA would have done it long ago.
And in two decades? who knows what kind of tech will be available by then. Might have found more new ways to use carbon.
That the Chinese have cornered the market on this resource just means we have to find another resource to make progress with.
Onwards with the eternal war of evolution.
by Gorden Russell
This is what I found at wiki. Looks like Planetary Resources has to get busy to give us phase change memory drives.:
In the Earth’s crust, it is as rare as platinum, but it is in abundance in space.
by Gorden Russell
I really got excited when I started reading this. A computer that boots up instantly! Yay! I haven’t got all minute. It’s such a bother waiting for the computer to boot up every morning that I multiplex by spending the time tying my shoes.
This was good news until I saw that this phase change memory was made with antimony and tellurium.
Most of the antimony in the world comes from a single mine in China. First they got all the neodymium for wind turbines and air conditioner motors and now this! They are gonna sock it to us.
And tellurium is as rare as platinum. Is it going to be in the NEO asteroids with the platinum group metals? Maybe Planetary resources will bring some back in time to give us these phase change memory drives.
You all just wait here while I go look up the platinum group metals.