Tellurium’s main uses — as a component in vehicles and solar panels — rely on its ability to conduct energy with little resistance. Its role as a semiconductor is now taking it into one of the key computing industries: digital storage.
Tellurium’s role in a changing market
Digital storage is a $50 billion industry that is preparing for change, and tellurium could play a leading role. At the cutting edge of the industry is phase-change memory (PCM), a memory technology capable of increasing computing devices’ storage capacity, reducing their physical size and integrating their long- and short-term memory.
PCM technology stores information by reorganizing materials’ atomic-level structure in microchip cells. Using chalcogenides — “glass-like materials … typically made of a mixture of germanium, antimony and tellurium” — as its medium, PCM orders nano-scale materials into 1 and 0 phases that send data to a processor.
Phase change memory works by sandwiching chalcogenide cells between two electrodes and varying the burst electricity passing through the material. A gentle burst of electricity will melt and cool the chalcogenide into an ordered crystal structure. In contrast, a larger current will not allow the material to cool into a defined crystal structure; instead it results in a melted, “disordered” amorphous structure.
The amorphous and crystallized structures differ in their electrical resistance; this allows computers to differentiate between the two states and thus code information into the cells on which the process takes place. The crystallized state corresponds to the memory cell storing a 1, while the amorphous melted state corresponds to a 0.
Traditionally, the chalcogenides used to create the cell structure have been a germanium-tellurium material, but researchers have enhanced the process by adding antimony. As a result the speed of crystallization (data memorization) of these chalcogenide cells (commonly known as Ge2Sb2Te5, or GST) has increased by a factor of 10.
The evolving ability to determine the size of the amorphous region in GST cells also allows the process to encode more data into the cell, creating “multi-level cells” capable of storing an increased amount of data.
Changing an industry
The application of phase-change memory is not new. Current rewriteable optical storage devices, such as CD-RW and DVD-RW discs, which also use tellurium as the phase-change material, apply this memory system to write and rewrite information on discs.
What is different is the application of this technology on a much smaller scale. Current microchip memory relies on flash memory, which traps electrons in small compartments to indicate a 1 or 0. But with the push towards the miniaturization of techonolgy, the ability to increase flash memory capacity while decreasing its size is running up against physical barriers. As a result, existing flash-based memory chips are expected to hit a physical limit within the next five years, which, as Reuters’ chief technology correspondent, Jeremy Wagstaff, notes, will pose barriers to the evolution of the industry.
The use of flash in iPods, smartphones and tablets boosted the flash industry into a US$21 billion business last year, “double what it was worth in 2005,” Wagstaff notes. By 2016, revenues are expected to hit $31 billion.
Multi-level cells hold the greatest potential for PCM. A recent article published in The Economist notes that IBM (NYSE:IBM) is now working with SK Hynix to bring to market multi-level PCM-based memory chips that can bridge the gap between flash storage and short-term random access memory, which is erased when a device is shut off.
The creation of a device that can incorporate “universal memory” — both storage and short-term memory — could lead to a radical change in one of the most essential features of computing devices.
But despite the potential held by PCM technology, challenges remain, and widespread implementation may be a few years off. Specifically, multi-level cells have difficulty maintaining their electrical resistance over time.
In 2010, Samsung announced that PCM would be “widely embraced by next year as the successor to NOR flash in consumer electronics.” But Samsung’s first efforts at the technology proved unsuccessful. It rolled out PCM memory in at least one cellphone brand in 2010 and promptly removed it.
But digital storage producers Micron Technology, Samsung and SK Hynix are leading the charge to bring these game-changing storage technologies to the market. Micron started selling its first PCM-based memory chips for mobile phones in July, offering storage capacity of 512 megabits and 1 gigabit.
The impact for tellurium producers could be significant if GST becomes a cornerstone of storage technology.
Securities Disclosure: I, James Wellstead, hold no direct investment interest in any company mentioned in this article.
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