Fastest Semiconductor May Also be Most Expensive

Scientists have found what they think may be the fastest known semiconductor. Sounds great, right? But it happens to made from one of the rarest elements: rhenium. That rare element combines with selenium and chlorine to form a “superatom.” Unlike conventional semiconductor material, the superatom causes phonons to bind together and resist scattering. This should allow materials that can process signals in femtoseconds,

Rhenium was the last stable element to be found in 1925. It is primarily used in combination with nickel in parts of jet engines, although it is also known as a catalyst for certain reactions. It is very rare and has a high melting point, exceeded only by tungsten and carbon. When it was discovered, scientists extracted a single gram of the material by processing 660 kg of molybdenite. Because of its rarity, it is expensive, costing anywhere from $2,800 to $10,600 per kilogram.

So maybe we aren’t destined to have desktop computers with 100 terahertz processors in them. But maybe we will. While the structure now uses rhenium, it is possible that understanding this effect will lead to new high-speed semiconductors using more affordable materials.

This is one of those areas where we always hear about new materials, yet we rarely see any impact on the actual market. For example, where are our diamond transistors? GaN may be the exception that proves the rule.

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