Common silicon electronic circuit board.
Image: Flickr/Creativity103
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
The switches in most electronic circuits are made of silicon, one of the commonest elements. But their successors might contain materials that, for now, are lab-grown oddities: strongly correlated metal oxides.
The allure of these materials lies in the outer shells of electrons surrounding their metal atoms. The shells are incomplete, leaving the electrons free to participate in coordinated quantum-mechanical behavior. In some materials, electrons pair up to produce superconductivity, or coordinate their spins to produce magnetism. Other materials can switch from being an insulator to a conductor.
Unlike transitions to superconductivity, which happen as temperatures approach absolute zero, the insulating-to-conducting transition typically happens as temperature increases, and sometimes occurs near room temperature. That has raised hopes that metal oxides could be used instead of silicon to make transistors. A spate of results is now making that look feasible. “People are interested in seeing if oxides can make it to applications,” says Manuel Bibes, a physicist at the Joint Physics Unit in Palaiseau, France, which is run by the French National Research Center and electronics company Thales.
Metal oxide transistors have the potential to consume less power than silicon switches, because the phase transition frees electrons from their localized state near each atom, without moving them through the bulk material. By contrast, silicon switches work by pulling electrons through the material to a channel where they conduct current (see ‘Go with the flow’).
Image: Courtesy of Nature Magazine
In the past 5–10 years, researchers have succeeded in growing high-quality thin films of the metal oxides — overcoming one of the major barriers to applications. In July 2012, for example, a group in Japan reported that it had deposited a thin film of vanadium dioxide that underwent a phase transition in response to an applied electric field — proof that the material could be used as an electronic switch.
And last month, a group led by Shriram Ramanathan, a materials scientist at Harvard University in Cambridge, Massachusetts, addressed a fabrication challenge by growing a thin film of samarium nickelate on top of a substrate made of silicon and silicon dioxide.
The nickelate was deposited at a relatively low temperature that did not disturb the underlying silicon layers, raising the possibility of manufacturing metal oxides on top of silicon wafers to form three-dimensional chips, says Andrew Millis, a solid-state theorist at Columbia University in New York. Not only would that allow computing power to be packed much more densely, says Millis, but it would also permit metal oxide switches to be built on top of existing circuit architectures.
Other groups are trying to understand the nature of the phase transition. In January, Ivan Schuller, a solid-state physicist at the University of California, San Diego, and his colleagues showed that in vanadium oxide, the transition is in large part caused by micrometer-scale heating by the applied electric field.
See what we're tweeting about
16 Comments
Add CommentI'm not clear on what this means. Metal oxide transistors are not new at all.
Reply | Report Abuse | Link to thisCMOS (Complementary metal-oxide semiconductor) technology has been commercially available since the sixties/seventies, and the more sophisticated MOSFET (Metal-Oxide field effect transistors) not far behind, with much lower power consumption and high resistance to interference (or noise).
Although the general tone of the article suggests MOS is being invented now, I assume the actual work is about something else - higher integration? Better performance? Cannot tell for sure from this piece.
"But given recent progress, he feels that researchers need to start trying to implement them in devices" Heh, I've built CMOS and MOSFET based devices since the 80's - do I get a Nobel?
NOT a good article here, sorry.
"... addressed a fabrication challenge by growing a thin film of samarium nickelate on top of a substrate made of silicon and silicon dioxide."
Reply | Report Abuse | Link to thisThe article seems to be attempting to discuss the use of rare-Earth element oxides rather than more common aluminum or poly-silicone to fabricate circuits.
On a related subject, what ever happened to silicone-on-sapphire as a promising 'new' substrate material? These new, rare metal oxides couldn't fall into similar cost and implementation rabbit holes, could they?
Besides, it sounds like we'd have to warm up our computers on those cold winter mornings...
Your hubristic suggestion that the semiconductor researchers at Harvard University never heard of CMOS makes you the obvious fool. Between them and you, I have a guess who misunderstands the article.
Reply | Report Abuse | Link to thisNo doubt the researchers know that they're still producing CMOS circuits - but this seems to have been lost in translation by the author of this report. IMO, Acoyauh2's comments regarding this article are accurate and valid - making you the obvious, well, author's dupe...
Reply | Report Abuse | Link to thisBad hair day, huh?
Reply | Report Abuse | Link to thisI'm sure the scientists are aware of last century's CMOS tech, and that they're probably either trying to improve it or seeking other alternatives.
However, that is not what the article says, and that's what my comment refers to. The article suggests they're trying to invent metal oxide semiconductors, which is, to say the least, misleading.
Relax, have a break, have a chocolate, or something that improves your mood...
Actually, I'm likely in error referring to the fabrications mentioned in the article as CMOS - MOSFET, as Acoyauh2 implies, is probably a more applicable description, if not precisely accurate.
Reply | Report Abuse | Link to thisNice try, but no. The article states they're trying to invent metal oxide based semiconductors, not just oxide insulators on silicon (It's in the first sentence). I though you said you knew what your were talking about.
Reply | Report Abuse | Link to thisThe author says nothing about "trying to invent" anything anywhere, and in CMOS & MOSFET integrated circuits the metal oxides form the conducting circuits, not insulators. As I understand, doped silicon in those devices provides the semiconducting/semi-insulating gated circuit function.
Reply | Report Abuse | Link to thisThe inset illustration, "GO WITH THE FLOW", can help explain what the author is trying to describe. In the new devices, a thin layer of metal oxide on an insulating silicon substrate provides the semiconducting gated circuit function.
However, even here the illustration states:
"Metal oxide transistors have the potential to consume less power than silicon ones, because switching does not require the atoms to be relocated."
I have no idea what atoms ever get relocated in any form of transistor - I think this is additional misinformation...
As best I can guess from this report _and_ the research report abstract,
Reply | Report Abuse | Link to thishttp://www.nature.com/nature/journal/v487/n7408/full/nature11296.html
- the new switches consume less power because the electrons don't have to travel as far to produce a current flow, due to some quantum state phase transition effect.
A _very_ important feature - incredibly, not even mentioned in this article - is that the nature of this switch makes it state persistent. In other words, these circuits could be used to produce low power non-volatile memory!
As Acoyauh2 stated initially:
"NOT a good article here, sorry."
P.S. the enlarged inset illustration is located at
http://www.nature.com/polopoly_fs/7.9335.1362498861!/image/metal-oxides.jpg
Actually, no. The metal oxides in CMOS and MOSFET devices are not conductors. The MOS in MOSFET refers to the stack of layers forming the gate: a metal layer on top of a layer of Si02 on top of the semiconductor channel that actually carries current when the device is switched on. CMOS stands for Complementary metal oxide semiconductors refering to the fact that such devices use MOSFET transistors of both P and N types. This article is about research into using metal oxides AS semiconducting matrerials.
Reply | Report Abuse | Link to thisA couple grammatical mistakes in the article:
Reply | Report Abuse | Link to this1) Commonest - should be "more common" or "most common", not "commoner" and "commonest."
2) The subheading says, "the metals are not yet close to 'completing' with silicon." I believe that should say, "competing."
Aside from those issues, I would like to see one of these theoretical applications actually be put use in the real world, not just as a lab result.
Thanks for the correction - I was confusing the terms conducting metal and metal oxides with the dielectric (silicon dioxide) insulating layer.
Reply | Report Abuse | Link to thisThat being said, I did understand that the article was describing attempts to use special rare-Earth element oxides as semiconductors, rather than doped silicon.
If you understand the following statements made in the article, _please_ explain:
"Metal oxide transistors have the potential to consume less power than silicon switches, because the phase transition frees electrons from their localized state near each atom, without moving them through the bulk material. By contrast, silicon switches work by pulling electrons through the material to a channel where they conduct current (see ‘Go with the flow’)."
and
"Metal oxide transistors have the potential to consume less power than silicon ones, because switching does not require the atoms to be relocated."
Please see
http://www.nature.com/polopoly_fs/7.9335.1362498861!/image/metal-oxides.jpg
Also, what do you think of an article that fails to mention that the switch being described is persistent? Please see
http://www.nature.com/nature/journal/v487/n7408/full/nature11296.html
Yes, Gizmo. I'm sad to see a comment (not yours) where someone is criticizing the accuracy of the facts in the article (incorrectly) and providing incorrect information of their own. Metal–oxide–semiconductor refers to the structure of certain (field effect) transistors, with a metal gate electrode placed on top of an oxide _insulator_, on top of a semiconductor material. That is what CMOS is.
Reply | Report Abuse | Link to thislampora,
Reply | Report Abuse | Link to thisDoes CMOS switching "require the atoms to be relocated" as stated in the article?
Please explain the article's statements:
"Metal oxide transistors have the potential to consume less power than silicon switches, because the phase transition frees electrons from their localized state near each atom, without moving them through the bulk material. By contrast, silicon switches work by pulling electrons through the material to a channel where they conduct current (see ‘Go with the flow’)."
and (especially)
"Metal oxide transistors have the potential to consume less power than silicon ones, because switching does not require the atoms to be relocated."
It is the misinformation and missing information that confuse even somewhat knowledgeable readers and cause them to search the provided incomplete information (in vain) for more complete understanding. That is, in the case of critical readers...
BTW - no one ever 'hubristically' suggested that the researchers "never heard of CMOS" - except when you were 'hubristically' 'putting words into the mouth' of Acoyauh2:
Reply | Report Abuse | Link to this"Your hubristic suggestion that the semiconductor researchers at Harvard University never heard of CMOS..."
The article states that "electrons near atoms" are freed up to move. So it is the electrons that are moving.
Reply | Report Abuse | Link to this