Boffins build bendy Flash array
Organic floating-gate transistors employed
Japanese boffins have created a flexible sheet of Flash memory out of organic transistors.
The team, led by Takao Someya of the University of Japan's Applied Physics, and Electrical and Electronic Engineering departments, built the transistors using a dielectric material composed of a 2nm-thick polymer layer and a 4nm-thick sheet of aluminium oxide.
The layers insulate each transistor's 'floating' metal gate from the rest of the structure - a control gate above and the source and drain below. The metal gate can retain a charge, allowing to 'store' a binary memory value.
Someya told the journal Science that each transistor - there are 676 in the group's test array - can last for 1000 write cycles. Silicon Flash has a longevity of more than 100,000 write cycles, of course, but these are early days for Someya's process, and his transistor sheet is both flexible and considerably cheaper to mass-produce than silicon Flash.
While the organic transistors are not likely to replace Flash chips any time soon, they may find a role in devices that need to bend or be fitted to an irregular shape. Disposable memory products are another possibility.
Memory for a foldable e-newspaper, anyone?
To show one possible application and to test the transistors' storage longevity, Someya's team bonded the sheet to a pressure sensor forming a plastic device that's less than 700µm thick and can record pressure patterns. The patterns are retained completely for 20 minutes, but begin to degrade after that until, 24 hours or so later, they are gone.
Someya believes that these figures can be improved significantly, as can the memory cells' write-cycle lifetime. ®
COMMENTS
So, let me get this straight?
Does this mean that I will be able to scrunch up my computer into a small paper ball and swallow it whole after work, excrete it the next morning, unfold it, and carry on working? ... or is that not what he's saying?
@MinionZero
"This technology sounds ideal for cheap electronics, rather than high performance electronics"
Yes and no.
The lack of high performance is very likely. IIRC all the flexible electronics approaches have fairly unimpressive (by modern standards) clock speeds. 100KHz definite, I *think* some could (or were talking) up to 5MHz.
The 2 obvious ways to counter that would be to ditch the clock and go asynchronous and/or to stack multiple logic layers one over the other and use the third dimension. This was looked at back in the day for wafer scale logic (Hughes were big in airborne processors). Interconnect methods exist for Silicon but not so sure about floppier substrates. The architecture was also described for imaging sensors using multiple layers of CCD electronics (analogue processing) Programming would have been done by switching different logic blcks into the processing chain and varying their individual clocks, possibly with nearest neighbour I/O. Processing clock rate <1Mhz but all pixels done *together*.
You might like to think about some other applications of this.
"Cheap" is more doubtful. It's what this article did not say. What are the device sizes? magazine publishing does 4 layer registration at IIRC 1200DPI. Roughly 21microns. PCB layouts do about 70microns. Magazine production is relevant because big production -> small cost, which you want if you want to talk cheap enough to throw away, rather than cheap as a flat screen display But it also sets limits on transistor size, which hurts clock speed a *lot* given that basic properties are a long way below silicon.
The other question is how many steps took place in vacuum. AFAIK most organic compnenets are sensitive to water vapour. In the real world every vacuum cycle would add a lot of time and money to production cost.
"So once some kind of support and protective layers are added, I wonder how think the whole device becomes?. "
Actually it would have to get a *lot* thicker before you would even realise you were holding something in your hand. Writing paper is roughly 40-60microns, stiff card 100microns. Metal shim stock (standard industrial material) is metal sheet in the thousandths of an inch range. 2 thou (50microsn) is fairly common. The layers in the report are namometres, 1000x smaller.
A credit card is roughly 700 microns.
If you stacked all the active layers together even a *very* high layer count would be difficult to see. However your back to getting all those layers to line up almost perfectly. device layers on substrate you align to each other seems the safer option. The odds are most of the device would be a battery anyway.
Disposable paper based batteries already exist. Actually there are multiple other technologies which could serve as volatile or non volatile memory (MIT "Things that Think" project for example). It seems the technology is approaching the critical mass needed to field complete devices of some kind.
The issue is to do what?
Just glue it together.
E-paper on top of some electronics in bendy fpga form and some of this storage, on top of paintable batteries. Add the obligatory RFID (nobody explained yet why, but it's obligatory), and you have readable smart tags, a viable e-newspaper, what-have-you. This could make mobile computing very interesting indeed, chinese or otherwise.
As always, usable for good and goog^H^Hvernment both.
Memory isn't the only application...
1000 write cycles is more than enough for programmable logic, like FPGA and microcontrollers.
This technology sounds ideal for cheap electronics, rather than high performance electronics.
"built the transistors using a dielectric material composed of a 2nm-thick polymer layer and a 4nm-thick sheet of aluminium oxide"
So once some kind of support and protective layers are added, I wonder how think the whole device becomes?. As I was wondering, this sounds like it would be easy to print multi-layer devices like a tower block of layers sandwiched together. That would vastly increase its storage capacity and as its cheap, it would be cost effective to make.
