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Transistors, and the conductive traces that connect them, are routinely created by the billions on the surface of silicon wafers, which are later cut into the individual “chips” that power our computers, phones, watches, and countless other electronic gadgets. But few people think much about how those silicon wafers are made in the first place. It’s quite tricky.


Very pure sand (silicon dioxide) has to be melted, at which point a seed crystal of elemental silicon is brought in contact with the melt, which slowly deposits silicon atoms on the seed, ones that extend the seed’s crystalline lattice. Masses of pure silicon are slowly grown this way, with an entire ingot, which might measure 30 centimeters or more in diameter, being one big well-oriented crystal. Such silicon ingots are then sliced thinly into wafers and polished, providing a substrate on which to build circuits made up of huge numbers of transistors, diodes, and other electronic devices.

No wonder electrical engineers have long sought easier ways to create the substrate on which to form their creations. Since the early 2000s, they've been able to produce transistors and similar devices using thin films of silicon and other semiconducting materials applied to insulating substrates. But that, too, requires rather complicated manufacturing techniques, often involving a high vacuum.

Another approach that has shown great promise in recent years is solution-processing of semiconductors. This is possible, for example with a class of hybrid organic-inorganic materials that have crystal structures matching that of the mineral perovskite. Such perovskite semiconductors can be formed simply by coating, say, a piece of glass with the proper chemical solution and letting it dry.

This approach has been used, in particular, to produce some remarkably efficient photovoltaic cells, ones that can compete with traditional silicon solar cells. It’s also been used to create perovskite-based photodetectors and light-emitting diodes.

Engineers are now extending the application of these easily fabricated perovskite semiconductors into a new realm: field-effect transistors. An international team led by Aram Amassian at North Carolina State University in Raleigh, N.C., has for the first time demonstrated the construction of field-effect transistors using a single crystal, hybrid perovskite semiconductor. A report of their work appeared on 17 December in the open-access journal Nature Communications.

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Category: Science