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New Technology For Converting a Metal To a Semiconductor With a Laser

samzenpus posted about a year ago | from the presto-chango dept.

Shark 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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I would like to know (2)

For a Free Internet (1594621) | about a year ago | (#45252283)

I have been researching the same systems in my lab, but I wonder how the MIT researchers overcame the Koslowsky effect. If this is not examined in their paper, it's a sham.

Re: I would like to know (0)

Anonymous Coward | about a year ago | (#45252549)

They tune to eliminate the residual phonon quanta at the surface density of interest.

Re: I would like to know (-1)

Anonymous Coward | about a year ago | (#45255101)

Troll much?

um, so after reading the summary (0)

Anonymous Coward | about a year ago | (#45252319)

there is no actual "technology" here and it seems like an awfully complex and resource intensive way to make a single bit.

photoelectric effect (0, Offtopic)

girlintraining (1395911) | about a year ago | (#45252363)

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.

Re:photoelectric effect (0, Interesting)

Anonymous Coward | about a year ago | (#45252469)

Photons aren't charged you fuckwit. You don't know what the hell you're talking about. Surprise.

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45252893)

Oh look! someone made an error, I'm going to make them look as much of a fool as possible, just to boost my own ego!

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45253451)

Oh look! We live in an era of instant information access and I can't be bothered to spend 30 seconds to verify facts before making professorial-sounding statements!

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45255359)

This particular person either makes errors over and over again and someone by shear luck or dumbness always mods her up, or she is a troll that has a away of modding her own posts up. Ones like this which are either completely incorrect and/or off-topic still get modded up, and it happens on nearly every science topic with her posts.

Re:photoelectric effect (1)

romons (2767081) | about a year ago | (#45262661)

And anybody who points it out gets modded down to 0. Sigh.

Re:photoelectric effect (4, Interesting)

moteyalpha (1228680) | about a year ago | (#45252593)

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.

Re:photoelectric effect (2, Insightful)

Anonymous Coward | about a year ago | (#45252831)

That's girlintraining's schtick. He comes in, makes some kind of pseudo-intellectual post full of wrongness, and the uneducated slobs mod him up. It really shows how uninformed the average slashdotter is.

Re:photoelectric effect (-1, Flamebait)

girlintraining (1395911) | about a year ago | (#45252969)

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:

Uhh, this isn't about what was said in the TFA. My statement applies to the photoelectric effect. The underlying math behind the statement is available [wikipedia.org] . Wavelength is directly coupled with the specific energy of a photon -- shorter wavelengths mean higher specific energy. Once enough specific energy is present, an electron will strike the material, and a photon will be emitted, or vice versa. Below the threshold, and no particle will be emitted.

What the article is dicussing is about what happens below that threshold. This behavior is a consequence of the photoelectric effect -- it deals with how a given material deals with the absorption of energy, instead of the conversion of it.

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45253583)

Please show us where the charged photons come in, you revisionist goal-post-changing liar. Don't forget, you went through the trouble of italicizing "charged".

" if it is struck by a charged particle at or above that, it will absorb it and then emit an electron. "

Just admit you don't know what the hell you're talking about, as usual. Your posting history speaks for itself.

Re:photoelectric effect (4, Informative)

iggymanz (596061) | about a year ago | (#45252919)

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

Re:photoelectric effect (-1, Flamebait)

girlintraining (1395911) | about a year ago | (#45254513)

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

Sounds like it's the same phenomenon to me. You're confusing a property with an effect.

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45254693)

Show us again how the photons are charged? Your italics, remember.

Re:photoelectric effect (1)

Anonymous Coward | about a year ago | (#45255349)

You might be surprised to learn there are a wide variety of effects and principles involving the interaction two words you put in bold, photons and electrons, that have nothing to do with the photoelectric effect. This has to do with altering the electronic structure, not ejecting electrons, or just giving them energy less than excitation. The creation and tuning of a bandgap when there was no before, creating a region in an energy diagram where electrons can't get to by use of light is something rather different. Might as well conflate the principle of buoyancy with the operation of something like an adsorption pump, after all they both involve movement of fluids, never mind one involves vertical forces against gravity and another has to do with confining something to a surface.

Re:photoelectric effect (1)

iggymanz (596061) | about a year ago | (#45276257)

No, you are confused. The photoelectric effect ejects an election. Altering bandgap can be done without ejecting electron.

Re:photoelectric effect (0)

Anonymous Coward | about a year ago | (#45253635)

I guess the associated annalogy would be 3d printing. Prior to 3d printing, it was known that one could create objects by combining a group of things.
3d printing technology allows one to do it without human labor.
Actually, it'd be interesting to use the above effect to 3d print a circuit with a given material && use the appropriate "laser blast" to change the
material into the required digital / optical circuit all in a single 3d printed pass(es).

Re:photoelectric effect (1)

Anonymous Coward | about a year ago | (#45253767)

Jesus Christ you people have an obsession with 3D printing, combined with a hilarious naivete about what it actually does.

Re:photoelectric effect (1)

Anonymous Coward | about a year ago | (#45255547)

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 in a gas (there isn't even bands to begin with).

Being able to alter the bandgap means changing the energy levels within a crystal, which has a meaning even if those bands are all empty (i.e. no electrons in the bands), nor does it absolutely requires absorption or emission of photons (even though it may).

In comparison, there is no meaning to photoelectric effect without any electrons, or without photon absorption.

Egad! (1)

RyanFenton (230700) | about a year ago | (#45252403)

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

Re:Egad! (1)

Theovon (109752) | about a year ago | (#45253343)

Wait, I thought we needed to reverse the polarity of the neutron flow.

Re:Egad! (0)

Anonymous Coward | about a year ago | (#45255277)

Aren't there dylithium crystals involved as well?

Re: Egad! (1)

Inigo Montoya (31674) | about a year ago | (#45256311)

I'm sure we'll discover that next year.

Just to clarify (1)

Anonymous Coward | about a year ago | (#45252441)

Does the material exhibit these properties while the laser is hitting it, or is it affected permanently?

Re: Just to clarify (1)

Anonymous Coward | about a year ago | (#45252463)

I don't know but is there anything lasers and bacon can't do?

Re: Just to clarify (0)

Anonymous Coward | about a year ago | (#45252643)

I don't know but looking at the pictures made me wonder if there isn't anything tin foil can't do!!!

Re: Just to clarify (2)

93 Escort Wagon (326346) | about a year ago | (#45253155)

I'm very disappointed there's absolutely no mention of sharks in this article.

Re: Just to clarify (0)

Anonymous Coward | about a year ago | (#45253807)

My God! Think of the damage sharks with lasers could do to innocent metal ships! First, a ship minding its business, avoiding corrosion and magnetic mines. Here comes the hungry shark with a laser, lasing the ships hull and ripen it for corrosion and mines. Holes, explosions, water in, people right out to the waiting mouth of the beast!

Re: Just to clarify (0)

Anonymous Coward | about a year ago | (#45258311)

Here's [slashdot.org] the story about sharks. And I'm sure the Koch brothers have friggin' lasers.

COCK (-1)

Anonymous Coward | about a year ago | (#45253181)

clothEs or be a

Can this be used for graphene semiconductors? (1, Interesting)

Forever Wondering (2506940) | about a year ago | (#45253559)

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?

Re:Can this be used for graphene semiconductors? (1)

afxgrin (208686) | about a year ago | (#45254681)

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.” "

Re:Can this be used for graphene semiconductors? (1)

Chris Katko (2923353) | about a year ago | (#45254937)

Perhaps, but there's a huge difference between changing a band gap and creating one.

Re:Can this be used for graphene semiconductors? (1)

syockit (1480393) | about a year ago | (#45256495)

Is the bandgap of graphene zero, or is there no bandgap on graphene?

Can it be used to print CPUs? (1)

Yvanhoe (564877) | about a year ago | (#45256731)

The article is very light on details. I wonder if that could make it possible to produce small series of microchips. It would be an incredible tool for your local fablab...

Re:Can it be used to print CPUs? (1)

avandesande (143899) | about a year ago | (#45258231)

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.

Re:Can it be used to print CPUs? (1)

Yvanhoe (564877) | about a year ago | (#45265673)

I agree that a chip factory does not want a machine that takes hours to print a single chip but fablabs do want a possibility to make only one or two chips of a custom design. It makes sense for this niche.

Repairs can be made (0)

Anonymous Coward | about a year ago | (#45256947)

Wait. What? We can soon repair our transistors again?

Imagine, instead of buying a new cellphone/memory chip/cpu, you just need one of those lasers and a very steady hand..

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