New, Unusual Semiconductor is a Switch-Hitter

Jan 30, 2009 By Laura Mgrdichian feature

(PhysOrg.com) -- A research group in Germany has discovered a semiconducting material that can switch its semiconducting properties -- turning from one type of semiconductor to another -- via a simple change in temperature. This intriguing behavior may make the material useful in efforts to create better performing integrated circuits, which form the backbone of almost all electronic devices.

Semiconductors are essential to integrated circuits, and any significant advances in semiconductor materials could mean big changes for the future of electronic technologies. For example, this new finding may further developments in data-storage technology. At a more fundamental level, the material could change how semiconductor chips are designed.

"This new material may be able to help simplify chip production in the future," the study's corresponding researcher, chemist Tom Nilges of the University of Muenster, in Germany, said to PhysOrg.com. "Instead of using two materials to build transistors for integrated circuits, there is now a reasonable chance that this job could be performed by a single material."

The material is a compound containing silver, tellurium, and bromine, abbreviated Ag10Te4Br3. At three distinct temperatures—290 degrees Kelvin (K), 317 K, and 390 K (62, 111, and 242 degrees Fahrenheit, respectively)—the material changes from a p-type semiconductor (excess positively charged "holes," or electron absences) to an n-type (excess negative carriers), and back to a p-type. These changes are reversible.

Silver-based semiconducting compounds tend to have many interesting electrical properties, mainly because they can conduct both electrons and silver ions exceptionally well. This makes them useful in a variety of electronics applications. For example, they are being eyed as good candidates for a certain type of memory device.

Another possible application for these materials is in the relatively cheap production of electricity without the simultaneous emission of planet-warming greenhouse gases. Ag10Te4Br3 may be particularly suited to this, as it has interesting thermal properties. For example, over the temperature range 355 K - 410 K, the material displays a strong and broad endothermic response, meaning it absorbs a large amount of heat from its surroundings.

In addition, it does not rapidly adjust its temperature in relation to its surroundings -- it has a very low "thermal diffusivity" -- and displays a huge thermopower drop, meaning the voltage across the material changes rapidly in response to changing temperature. Such a large thermopower change has not before been observed.

The ability of Ag10Te4Br3 to switch from p-type to n-type and back again is the result of several complex structural changes it undergoes in response to the changing temperature. In combination, these changes allow the material's electrical properties to morph so dramatically. Some of the tellurium ions form mobile chains; the silver ions coordinate to those chains. There is also a shift in the concentration of charge carriers—electrons and holes—which is connected with the chain-forming tendency of tellurium.

Future research into Ag10Te4Br3 may focus on its potential to allow fine-tuning of its physical properties, beyond the changes caused by temperature alone.

Citation: Nilges et al. Nature Materials 8, 101-108 (2009); advance online publication, (doi:10.1038/nmat2358)

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Pseudoparticles travel through photoactive material

Related Stories

When temperature goes quantum

Mar 06, 2015

A UA-led collaboration of physicists and chemists has discovered that temperature behaves in strange and unexpected ways in graphene, a material that has scientists sizzling with excitement about its potential ...

Hybrid memory device for superconducting computing

Jan 26, 2015

A team of NIST scientists has devised and demonstrated a novel nanoscale memory technology for superconducting computing that could hasten the advent of an urgently awaited, low-energy alternative to power-hungry conventional ...

Recommended for you

Pseudoparticles travel through photoactive material

Apr 23, 2015

Researchers of Karlsruhe Institute of Technology (KIT) have unveiled an important step in the conversion of light into storable energy: Together with scientists of the Fritz Haber Institute in Berlin and ...

From metal to insulator and back again

Apr 22, 2015

New work from Carnegie's Russell Hemley and Ivan Naumov hones in on the physics underlying the recently discovered fact that some metals stop being metallic under pressure. Their work is published in Physical Re ...

Electron spin brings order to high entropy alloys

Apr 22, 2015

Researchers from North Carolina State University have discovered that electron spin brings a previously unknown degree of order to the high entropy alloy nickel iron chromium cobalt (NiFeCrCo) - and may play ...

Expanding the reach of metallic glass

Apr 22, 2015

Metallic glass, a class of materials that offers both pliability and strength, is poised for a friendly takeover of the chemical landscape.

Electrons move like light in three-dimensional solid

Apr 22, 2015

Electrons were observed to travel in a solid at an unusually high velocity, which remained the same independent of the electron energy. This anomalous light-like behavior is found in special two-dimensional ...

Quantum model helps solve mysteries of water

Apr 20, 2015

Water is one of the most common and extensively studied substances on earth. It is vital for all known forms of life but its unique behaviour has yet to be explained in terms of the properties of individual ...

User comments : 7

Adjust slider to filter visible comments by rank

Display comments: newest first

holoman
4 / 5 (1) Jan 30, 2009
Looks to be a new chalcogenide or multiferroic formulation.
El_Nexus
3 / 5 (2) Jan 30, 2009
It's a pity two of those critical temperatures are close to room temperature (17 and 44 degrees celsius), which would make any electronics made with this stuff highly sensitive to weather conditions.
h0dges
3 / 5 (2) Jan 31, 2009
It's a pity two of those critical temperatures are close to room temperature (17 and 44 degrees celsius), which would make any electronics made with this stuff highly sensitive to weather conditions.

I'm sure they'll be able to tweak the temps with shifter dopants.

@holoman: how is Ag10Te4Br3 either chalcogenic or multi-ferroic? It doesn't contain any chalcogens or iron.
nanomvp
5 / 5 (1) Jan 31, 2009
"Silver-based semiconducting compounds tend to have many interesting electrical properties, mainly because they can conduct both electrons and silver ions exceptionally well."

Silver diffusion seems difficult to integrate into conventional semiconductor devices.
gongii
5 / 5 (1) Feb 01, 2009
This is a silver-doped chalcogenide (chalcogen is Te). Chalcogenides have unstable microstructure, so will distort easily below 500 C.

The doping change is nice, but can you really make a p-n junction from this material? It probably contains too many structural defects that cause excess leakage.
semicon
not rated yet Feb 02, 2009
Hello all together,
the material changes pnp only at 390 K and
the transition can be changed to room temperature by chemical tuning. Also this feature is reversible.

Alizee
Feb 03, 2009
This comment has been removed by a moderator.
semicon
not rated yet Feb 04, 2009
It is a mixed conductor. The electronic cond. exeeds the ionic one by one order of magnitude.
The high silver mobility makes the phase transitions reversible. All structures were determined from one single crystal. That means no volume jump.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.