Giant piezoresistance in a silicon nanocrystal
Researchers have demonstrated the origin of the great variation of electric resistance in a commercial silicon-on-insulator wafer under mechanical stress.
The microelectronics industry is always looking to improve the performance of integrated circuits. The most widely used approaches include reducing the size of devices to the nanoscale and mechanical stress. Mechanical stress has the ability to modify the electrical resistance of the perfect crystals of silicon, a physical effect called “piezoresistance” which underpins the so-called “strained silicon” technologies, in which the silicon atoms are stretched beyond their normal interatomic distance.
In recent years, a wide variety of contradictory piezoresistive effects in silicon nanoobjects have appeared in scientific literature. Some claim that the piezoresistance of nanosilicon can be much greater than that of the usual “strained silicon,” others – the majority – maintain that it is comparable. The origin and the very existence of such a giant piezoresistance effect was therefore in question.
Using impedance spectroscopy, an experimental technique commonly applied in electrochemistry, physicists from the Laboratory of Condensed Matter Physics (LPMC, CNRS / École Polytechnique) and the Institute of Electronics, Microelectronics and Nanotechnology (IEMN, CNRS / ISEN Lille, Polytechnic University Hauts-de-France / École Centrale de Lille / Lille University) in France, and the University of Melbourne in Australia demonstrated a giant piezoresponse in an ultra-thin silicon layer.
This result brings a new perspective to bear on the debate over the piezoresistance of nanosilicon and, because it was observed in a commercial wafer, it paves the way for the development of strained-defect technologies for applications such as ultra-sensitive nano-strain sensors, fast-switching diodes, or electrical readout protocols for quantum technologies.
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