Silicon Has Metal-Like Behavior at Nanoscale

It bends, rather than break

By on 8 Oct 2009, 14:57 GMT
Silicon is the most widely used material in the semiconductor industry today, and experts have often said that the chemical is just as brittle as glass, and that it breaks easily. Apparently, that is entirely true, but only at the macroscale. As soon as researchers took the idea down to a smaller level – the nanoscale –, cracks began to appear in the theory. It immediately became obvious that, when pressure was applied to silicon nano-pillars, they did not break, but rather deformed in very much the same way metal did when pressured. This new-found knowledge may benefit industry partners considerably, AlphaGalileo reports.

From a material point of view, the new discovery could lead to altered manufacturing processes for a wide array of electronic goods, as well as to advancements in the watch industry. “Our pillar-bending tests are in principle the same as Tetmajer’s experiments, only our pillars are about a hundred thousand times smaller,” Johann Michler, the head of Mechanics of Materials and Nanostructures Laboratory, at the Swiss Federal Laboratories for Materials Testing and Research (EMPA) headquarters, in Thun, Switzerland, explains. Ludwig von Tetmajer was the founder of EMPA.

“Our results show that it might be possible to use silicon like a metal in mechanical applications, if the dimensions of the silicon structure are small enough,” the scientist adds. He and his team determined that the silicon started exhibiting the unusual properties when the diameter of the nano-pillars was brought down to less than 400 nanometers. The experts determined that it was not necessarily the internal structure of the silicon that was responsible for this behavior, but rather the flaws that the material had.

The Swiss team, together with colleagues from the universities of Uppsala and Minnesota, published the conclusions in the latest issue of the respected international scientific journal Advanced Functional Materials. The investigators also showed that, when the diameter of the pillars exceeded 400 nanometers, the structures cracked under pressure in the same way regular silicon did. Deformation only occurs when the dimensions of the column are smaller than the average distance between defects in the atomic structure, they conclude.

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A silicon pillar with a diameter of 310 nanometers a) before loading and b) after deformation. The column has yielded to the applied force and undergone plastic deformation
   A silicon pillar with a diameter of 310 nanometers a) before loading and b) after deformation. The column has yielded to the applied force and undergone plastic deformation