MIT News December 14, 2020 LEDs can be used as proximity sensors in smartphones, distance measurement in autofocus cameras, and gesture recognizers. As they are difficult to make from silicon, the LED sensors must be manufactured separately from their device’s silicon-based processing chip making them prohibitively expensive. Researchers at MIT have designed a silicon-based LED with specially engineered junctions to enhance brightness. The LED operates at low voltage, but it still produces enough light to transmit a signal through 5 meters of fiber optic cable. They envision a day when LED technology can be built right onto a device’s silicon […]
Physics breakthrough of the year
EurekAlert December 17, 2020 Silicon crystallized in the usual cubic (diamond) lattice structure has dominated the electronics industry for more than half a century. However, cubic silicon, germanium and SiGe alloys are all indirect-bandgap semiconductors that cannot emit light efficiently. An international team of researchers (Canada, the Netherlands, Germany, Austria) has demonstrated efficient light emission from direct-bandgap hexagonal Ge and SiGe alloys. They measured a sub-nanosecond, temperature-insensitive radiative recombination lifetime and observed an emission yield similar to that of direct-bandgap group-III–V semiconductors. They demonstrated that, by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously […]
Physics discovery leads to ballistic optical materials
Nanowerk December 14, 2020 The mismatch between electronic systems and optical systems means that every time a signal converts from one to the other, inefficiency creeps into the system. A team of researchers in the US (UT Austin, UMass Lowell, Purdue University) has found a way to create more efficient metamaterials using semiconductors and a novel aspect of physics that amplifies the activity of electrons. They have demonstrated optical phenomenon of “ballistic resonance” resulting from the interplay between free charge motion in confining geometries and periodic driving electromagnetic fields, which can be utilized to achieve negative permittivity at frequencies well […]
Quantum insulators create multilane highways for electrons
Nanowerk December 16, 2020 In quantum anomalous Hall (QAH) insulators, electron flow is constrained to the edges, and electrons on one edge can only go in one direction and those on the other edge can only go the opposite direction. In prior studies, the QAH effect had been experimentally realized only in materials where the Chern number had a value of 1, essentially with a single two-lane highway for electrons. They observed some dissipation of current at connection points between QAH insulators and metallic electrodes, which occurs in the form of heat. However, by increasing the thickness of the QAH […]
Researchers create entangled photons 100 times more efficiently than previously possible
Phys.org December 17, 2020 Current methods of creating entanglement are inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end. Based on their earlier research, researchers at the Stevens Institute of Technology carved extremely high-quality racetrack-shaped microcavities into flakes of lithium niobate crystal. The cavities internally reflect photons with very little loss of energy, enabling light to circulate longer and interact with greater efficiency. By fine-tuning additional factors such as temperature, the team was able to create an unprecedentedly bright source of […]
Toward imperceptible electronics that you cannot see or feel
Phys.org December 14, 2020 Transparent electronics—such as head-up displays that allow pilots to read flight data while keeping their eyes ahead of them. For healthcare applications the electronics should be sufficiently flexible to conform to skin. Although silver nanowire networks meet these criteria, the current methods of development create random nanowire alignment that is insufficient for advanced applications. Researchers in Japan used high-resolution printing to fabricate centimeter-scale cross-aligned silver nanowire arrays, with reproducible feature sizes from 20 to 250 micrometers. The microelectrodes-based organic field-effect transistors exhibited excellent multi-functionality. The sheets were well-suited for transparent electronics. As a proof-of-concept for functionality, […]
Ultra-thin designer materials unlock quantum phenomena
Science Daily December 17, 2020 Exotic states such as topological insulators, superconductors and quantum spin liquids are often challenging or impossible to create in a single material. The problem can be circumvented by deliberately selecting the combination of materials in heterostructures so that the desired physics emerges from interactions between the different components. An international team of researchers (Finland, Poland, Japan) used molecular-beam epitaxy to grow 2D islands of ferromagnetic chromium tribromide on superconducting niobium diselenide. They used low-temperature scanning tunneling microscopy and spectroscopy to reveal the signatures of one-dimensional Majorana edge modes. The fabricated 2D van der Waals heterostructure […]
UMBC team reveals possibilities of new one-atom-thick materials
EurekAlert December 15, 2020 Researchers at the University of Maryland demonstrated theoretically and experimentally that properties of two-dimensional group-III nitride semiconductors can be controlled by alloying. They found that by changing the alloying concentration, the band gap and exciton binding energies of each structure can be tuned accordingly, and for certain concentrations, a high thermoelectric performance was reported with strong dependence on the effective mass of the given alloyed monolayer. In addition, they explained contribution of each electron–hole (e-h) pair by investigating the e–h coupling strength projected on the electronic band structure. They found that the exciton binding energy decreases […]
Wireless, ultra-thin and battery-free strain sensors that are 10 times more sensitive
EurekAlert December 15, 2020 Performance of conventional strain sensors has always been limited by the nature of sensing materials used, and users have limited options of customizing the sensors for specific applications. Researchers in Singapore have developed flexible, stretchable, and electrically conductive nanomaterials called MXenes and fabricated strain sensors which are ultra-thin, battery-free and transmit data wirelessly. The sensors are 10 times more sensitive when measuring minute movements of industrial robotic arms, compared to existing technology. In precision manufacturing it helps improve the overall safety of robotic arms by providing automated feedback on precise movements with an error margin below […]
World’s First Successful Transmission of 1 Petabit per Second Using a Single-core Multimode Optical Fiber
NICT Japan December 18, 2020 Researchers in Japan have demonstrated the possibility of combining highly spectral efficient wideband optical transmission with an optical fiber guiding 15 fiber modes that had a cladding diameter in agreement with the current industry standard of 0.125 mm. This was enabled by mode multiplexers and an optical fiber that supported wideband transmission of more than 80 nm over 23 km. The study highlights the large potential of single-core multi-mode fibers for high-capacity transmission using fiber manufacturing processes like those used in the production of standard multi-mode fibers. The results of this study were accepted for […]