Memory device technology can be broadly classified into three types - magnetic disks, Flash and dynamic random access memory (DRAM). All three have their own advantages and disadvantages and all three are extensively used to a varying degree in practically every electronic system.
Magnetic disks such as the ones found in computer hard disk drives (HDDs) are far cheaper than other options and are perfectly suited to the storage of large volumes of data. However, as these drives possess moving parts they are not as robust as their solid-state counterparts (Flash and DRAM).
DRAM has a very fast response time and is perfect for performing rapid calculations and temporarily storing data. However, DRAM requires constant refreshing in order to store data for extended periods, thus making it unusable as a permanent storage option.
Flash memory is extremely robust and can store data without power for long periods of time. However, its read/write times are very slow in comparison to DRAM.
Frost & Sullivan has therefore taken great interest in a recent proposal by researchers from IBM's Almaden Research Centre in California. They have proposed an innovative type of memory that appears to combine the characteristics of current memory technologies to give a universal memory that is far better than existing technologies.
The idea currently being studied by the team is to develop a nanowire-based memory device, which is a radical new area still deep in the research stage. Nanowire-based memory holds significant promise as its small size and unique properties could allow for low cost yet high performance memory devices. However, according to lead researcher Stuart Parkin, this technology is still in the very early stages and there are several problems to be ironed out.
The growing interest in nanowire-based memory is due to its ability to efficiently store huge amounts of data without the need for moving parts. A single nanowire can potentially store anywhere from 10 to 100 times more data than current Flash technology while operating at much higher speeds. These devices will store bits of data in a magnetic medium (similar to HDD technology). However, unlike hard drives, they would not require any mechanical parts, making them extremely rugged. Additionally, unlike DRAM, they would not require a continuous supply of energy to store data.
Nanowire-based memory will resemble solid-state memory in that it would use millions of tightly packed read-write devices arrayed in a grid on a memory chip. However, unlike conventional solid-state memory in which each read-write device can store between one and four bits, each would be paired with a nanowire that can store between 10 and 100 bits. These bits would be quickly shuttled along the length of the nanowire, propelled by electronic pulses, and then read or written at one point along the nanowire.
The idea is to grow individual nanowires perpendicularly to the surface of the chip, such that they grow vertically from the surface, or are deposited in wells carved into the chip. This would allow for the storage of 100 bits in the same space that 1 bit would normally occupy in a Flash-based memory system.
Critical to the technology is finding a way to shuttle bits along the length of a nanowire. IBM's approach is to allow bits to be stored by the creation or removal of magnetic boundaries called domain walls within magnetic nanowires. These domain-wall bits create distinctive magnetic fields that can be read with conventional devices.
Researchers have long known that these walls can be moved using magnetic fields, but the walls would move in the same direction, annihilating each other. The key to making the device work was the discovery that electronic currents in magnetic materials can move these walls along a nanowire, and move them all in the same direction. That makes it possible to shift bits around to be read by single reading and writing devices.
Currently, the major hurdle faced by Parkin's team is the current required to move the domain walls. Tests have revealed that the required current is high enough to make it impractical. Parkin says that he is making progress on this front, having discovered that the current can be reduced by adjusting the frequency of short bursts. He is also working with new materials that may require less current.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected]
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