New Technology For Converting a Metal To a Semiconductor With a Laser 42
rtoz writes "Researchers at MIT have succeeded in producing and measuring a coupling of photons and electrons on the surface of an unusual type of material called a topological insulator. This type of coupling had been predicted by theorists, but never observed. The researchers suggest that this finding could lead to the creation of materials whose electronic properties could be 'tuned' in real time simply by shining precise laser beams at them. This work opens up a new avenue for optical manipulation of quantum states of matter. Their findings suggest that it's possible to alter the electronic properties of a material — for example, changing it from a conductor to a semiconductor — just by changing the laser beam's polarization. For example, a property called a bandgap — a crucial characteristic for materials used in computer chips and solar cells — can be altered by shining a polarized laser beam at the material."
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Re:photoelectric effect (Score:5, Interesting)
We've known about this since the turn of the last century. It's the photoelectric effect. Every material has a wavelength where if it is struck by a charged particle at or above that, it will absorb it and then emit an electron. This isn't news.
What's news is that we've now reached a sufficient level of understanding regarding the engineering of electro-optical systems that we are starting to build devices where the primary logic is based on optics, not electronics. This is an advancement of technology, not of understanding.
I am a bit confused by what you said. An incident photon at wavelength (Lamda) or smaller will eject an electron ( photo electric) and thermal excitation of a material like the cathode of a tube will also eject electrons. I am not getting where the charged particle comes in. From TFA:
In other situations, light can modify a material’s behavior — but only when it’s absorbed, transferring its energy to the material. In this experiment, Gedik says, the light’s energy is below the absorption threshold. This is exciting, he says, because it opens up the possibility of switching a material’s behavior back and forth without inducing other effects, such as heating — which would happen if the light were absorbed.
What they are talking about is changing the bandgap with the incident angle of polarized infrared laser light.
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Re:photoelectric effect (Score:5, Informative)
no, this is not the photoelectric effect. the "bandgap" is range of energy levels where no electron exists. Thisproperty separates insulators, semiconductors and conductors. They are altering the bandgap with polarization of light
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No, you are confused. The photoelectric effect ejects an election. Altering bandgap can be done without ejecting electron.
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OMG, you know just enough Physics to be dangerous.
Photoelectric effect has NOTHING to do with the bandgap of materials. The former only concerns the energy difference between a bound electron (bound in the material as a whole, or bound to an atom, doesn't matter) and the free electron states. The latter comes entirely from the aggregated properties of the material, usually in the form of a crystal structure.
You can have photoelectric effect on free atoms or molecules, e.g. on a gas. There is no bandgap i
Egad! (Score:2)
So... you're saying that the whole "we've got to alter the polarity on the deflector array" technobabble on Star Trek, may be retconned... as reality? With lasers, onto metals?
Daaaayyym.
Seriously though - neat new twist on material science, and great exploration of particle coupling/entanglement! Could result in some rather odd, but promising advances in chip design and layout.
Ryan Fenton
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Wait, I thought we needed to reverse the polarity of the neutron flow.
Re: Egad! (Score:2)
I'm sure we'll discover that next year.
Just to clarify (Score:1)
Does the material exhibit these properties while the laser is hitting it, or is it affected permanently?
Re: Just to clarify (Score:1)
I don't know but is there anything lasers and bacon can't do?
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I'm very disappointed there's absolutely no mention of sharks in this article.
Can this be used for graphene semiconductors? (Score:2, Interesting)
The article mentions that one can change the bandgap of a material with the laser. Isn't this what has been holding back graphene semiconductors--that they have a zero bandgap? Could this technique be used to produce practical graphene semiconductors?
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le sigh
From TFA:
"Gedik says that while this experiment was done using bismuth selenide crystals, a basic topological insulator, “what we have done is not specific to topological insulators. It should also be realizable in other materials as well, such as graphene.” "
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Can it be used to print CPUs? (Score:2)
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That is not how this would be used- printing millions of circuits one at a time would take too long which is why lithography works so well- you can print billions of circuits with a single exposure. Most likely the application would be some sort of self assembling or dynamic cpu.
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