Ultrakorte lichtflitsen van 0,00000000000002 seconde zorgen ervoor dat oppervlakte van een halfgeleider metaalvormig wordt
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A group of researchers from the Max-Planck Institute and the Berlin Humboldt University have discovered that semiconductors can be converted to metals and back again much more easily than previously thought with the help of laser light.

According to these knowledge institutes, the discovery could potentially boost the computational power of numerous electrical devices and simplify their design.


Almost all smartphones, computers and technical devices we use today are equipped with transistors. They connect the various materials in a computer chip and are as such essential for information transfer.

Transistors are usually made up of semiconductors. These are substances that conduct electricity, although not as well as metals. Often several substances are used for this purpose in order to direct the electric current as optimally as possible. However, this is not an ideal solution.

“Where computational power and size of electrical equipment are concerned, it would be better if just one substance was needed,” says project leader Julia Stähler. “And preferably only when you need that substance too.”

Zinc oxide

And that’s where the subject of the study comes in. The researchers were able to figure out that if the commonly used semiconductor material zinc oxide is irradiated with laser light, then the semiconductor’s surface changes to a metal that is a better conductor.

As soon as the light switches off, the surface changes back again.
It is a process that is called “light doping.”

The researchers say that only extremely small laser pulses are needed to achieve this effect. This ‘turning on and off’ of the metal happens at lightning speed. All in the space of 20 femtoseconds – whereby a femtosecond equals one trillionth of a second.

It is not ruled out that light doping also works on substances besides zinc oxide. The researchers believe their work could be instrumental in making electrical devices smaller and faster.

The Max-Planck Institute, like Fraunhofer, Jülich and Helmholtz, is one of Germany’s leading institutes for fundamental research. You can read other articles featuring Max-Planck here.