Nanoclast iconNanoclast

Next Step in Flexible Electronics: Self-Healing Dielectrics

Flexible electronics seem to be a continually expanding area of electronics. However, a half-century of focus on silicon-based electronics has left the shelf set aside for materials that can be used for these new flexible electronics a bit bare.

Of late, there has been a big research push aimed at developing self-repairing, electrically conductive materials that can withstand the damage caused by the twisting and deformation of the materials. But thus far, most of that research has focused on self-repairing electrical conductors.

Now researchers at Penn State University have looked at developing a self-healing dielectric material. Dielectrics are just as important as conductors in that they provide electronic insulation and packaging.

Read More

Nanosilver Ink Written in Midair for 3-D Printing

While the growth of 3-D printing has led us to believe we can produce just about any structure with it, the truth is that it still falls somewhat short.

Researchers at Harvard University are looking to realize a more complete range of capabilities for 3-D printing in fabricating both planar and freestanding 3-D structures and do it relatively quickly and on low-cost plastic substrates.

In research published in the journal Proceedings of the National Academy of Sciences (PNAS),  the researchers extruded a silver-nanoparticle ink and annealed it with a laser so quickly that the system let them easily “write” free-standing 3-D structures.

Read More

Spintronic Devices From Topological Insulators Inch Closer

Topological insulators (TIs) are materials that are insulators on the inside but conductors on the outside. They have been both a great hope and a head scratcher for scientists and engineers in fields such as “spintronics” and quantum computing who have been trying to make practical devices with the materials. The inability to combine TIs with a material that has a controllable magnetic property has proven to be a major roadblock.

Now in joint research, led by a team at the Massachusetts Institute of Technology, researchers have combined several molecular layers of a topological insulator material called bismuth selenide (Bi2Se3) with an ultrathin layer of a magnetic material, europium sulfide (EuS).

Read More

2-D Semiconductor Glows 20,000 Times as Brightly as Ever Before

Researchers at the National University of Singapore (NUS) have developed a way to give a massive boost to the photoluminescent efficiency of tungsten diselenide. In so doing, they may have paved the way for this two-dimensional semiconductor—which belongs to a class of 2-D crystals known as transition metal dichalcogenides—to have a greater impact on optoelectronics and photonics, including applications such as photovoltaics, quantum dots, and LEDs.

Read More

Silicon Nanoparticles Could Be a Boon for Fiber Optic Telecommunications

An international team of researchers from the Moscow Institute of Physics and Technology (MIPT), ITMO University (St Petersburg), and the Australian National University have demonstrated that silicon nanoparticles can significantly increase the intensity of the Raman effect. The results could be a boon to nanoscale light emitters and nanoscale amplifiers used in fiber optic telecommunications.

Read More
A black and white micrograph show protruding rows of closely spaced needle-like tips.

Single-Atom Sensor Offers New View of the Nanoscale

It was a eureka moment when IBM researchers first realized that they were imaging the surface of an atom with what came to be known as the scanning tunneling microscope (STM). Many believe that invention triggered the field of nanotechnology. Now researchers at the University of California Santa Barbara (UCSB) have created a next-gen microscope that can image phenomena like magnetism on the atomic scale across a huge range of temperatures. The heart of the microscope is a single atom or, perhaps more accurately, the absence of a single atom.

Read More

Shining a Light on Phosphorene's Crystal Structure

Black phosphorus—sometimes referred to as phosphorene in a nod to its 2-D cousin, graphene—has been on a research tidal wave since 10- to 20-atom-thick sheets of the material were first exfoliated back in 2014.

The research community has been excited by a number of its properties, like its tunable band gap, which opens up all sorts of photonic applications. But they have also perceived its intrinsically strong in-plane anisotropy, which means its properties are dependent on the orientation of the crystal, as being at once a strength and a weakness.

Now a joint research project involving scientists from MIT, Tohoku University in Japan, Oak Ridge National Laboratory, the University of Pennsylvania, and Rensselaer Polytechnic Institute in New York, have developed a method for determining the orientation of the crystal that should make it easy to deduce the properties of a given sample of black phosphorous and help pave the way for greater use of phosphorene.

Read More

DNA Creates Tiniest Thermometer Yet

Taking measurements of nanoscale objects is no easy task. Last month, researchers at IBM Zurich reported a breakthrough that leveraged an atomic force microscope (AFM) to measure the temperature of an object at the nanoscale. For the IBM researchers, the advance came when they stopped trying to make a nanoscale thermometer and instead focused on a macroscale thermometer for the nanoscale.

Now, researchers at the University of Montreal have turned that back around and produced the smallest thermometer yet. They had a skilled accomplice in accomplishing this feat: nature. The Canadian researchers have built a thermometer out of DNA that takes advantage of the molecule’s tendency to unfold in response to heat.

Read More

Plasmonics Make Electrochromic Polymers Fast Enough for Video

Electrochromic polymers that change color when a voltage is applied already have a pretty impressive wow factor, turning windows from clear to tinted with a flip of a switch.

Now researchers at Sandia National Laboratories have put this impressive feat to shame. They have devised a way to make the usually slow responding electrochromic polymers change colors fast enough so that they could be used as a material for flat-panel TVs.

The problem that has handicapped electrochromic polymers up to now has been that in order for them to achieve a good contrast between bright and dark pixels it has been necessary for them to be relatively thick. While this is good for creating contrast, it slows down the diffusion times for ions and electrons to change the polymer’s charge state. This has limited their use to static displays or darkening windows.

The Sandia researchers overcome this limitation by making the electrochromic polymer only nanometers thick and relying on plasmonics, which exploits the waves of electrons (plasmons) that are created on the surface of a metal when it is struck by photons.

Read More

Nanostructures Give Infrared Photodetectors Three Colors to See In

The nanostructured materials known as Type-II indium arsenide/gallium antimonide/aluminum antimonide (InAs/GaSb/AlSb) superlattices have been around since the 1970s and have served in infrared detection applications since the late 1980s. Since then, Type-II Sb-based superlattice materials have evolved drastically with many variants suited for different applications.

Now researchers at Northwestern University, led by Manijeh Razeghi, have developed a new superlattice design, called M-structure superlattice. It can be used to make devices that operate as a shortwave/mid-wave/long-wave infrared photodetector. Shortwave infrared wave (SWIR) bands make it possible to detect reflected light. Mid-wave detection picks up hot plumes and long-wave infrared detects cooler objects.

The researchers claim that a device designed around this new material can detect any of these infrared wavebands by simply adjusting the applied bias voltage. In terms of actual applications, the researchers claim this device could make possible infrared color televisions and three-color infrared imaging.

In research described in the Nature journal Scientific Reports, the researchers produced this superlattice by alternating the InAs, GaSb, and AlSb layers (with thicknesses of a few angstroms to a few nanometers) over several periods. The result is a one-dimensional periodic structure like that of the periodic atomic chain in naturally occurring crystals.

“The beauty of Type-II superlattice is the gap engineering capability which allows us to artificially manipulate and create novel ‘materials’ like the way natural semiconductors are created,” said Razeghi in an e-mail interview with IEEE Spectrum.

There are currently only a few material systems that are suitable for multi-spectral detection, according to Razeghi. The current state-of-the-art, mercury cadmium telluride (HgCdTe) and quantum well infrared photodetectors (QWIPs), are commercially available for infrared dual-band detection. However, mercury cadmium telluride technology is expensive and hard to make, while quantum well detectors suffer from low quantum efficiency and require low operating temperatures.

“In that context, Type-II InAs/GaSb/AlSb superlattices have proved to be an excellent alternative,” says Razeghi. “Controlling the electronic structure by managing the layer thicknesses as they are grown on GaSb substrate [yields] superlattices with the capability of tuning from SWIR to very-long wavelength infrared (VLWIR), covering the whole infrared spectrum.”

Despite the immense promise of the M-structure superlattices, this developing new material system has been the focus of considerably less development than II-VI based mercury cadmium telluride photodetectors, according to Razeghi.

“The current state-of-the-art in infrared detection technology is still based on HgCdTe, and relatively little effort has been expended developing dual- and triple-band T2SL based focal plane arrays (FPAs),” Razeghi told Spectrum. “There is a unique opportunity to mature this material system and realize a new generation of dual- and triple-band FPA sensors.”

However, Razeghi concedes that, responsivity, which dictates how sensitive a photodetector is, and the dark current, which is related to the noise, must be further improved. This means the optimization of many parameters, including device design, material growth, and all of the processing steps, must result in high reproducibility and high yield.

“We need to reduce the bias dependency of the long-wavelength channel to a reasonable range so that it could be compatible with the currently available readout integrated circuit,” says Razeghi.

The next step in the research, she says, will be to fabricate a three-color infrared camera. She added: “Our long term goal is to improve both electrical and optical performance of the detectors in order to make cheap high-performance infrared cameras for different applications.”



IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

Dexter Johnson
Madrid, Spain
Rachel Courtland
New York City
Load More