Phys.org September 6, 2023 In the visible spectrum, electroluminescence from colloidal quantum dots is highly efficient, wavelength tunable and cost effective, which motivates using the same approach in the infrared. Despite the promising performances of colloidal quantum dots light-emitting diodes in the near-infrared, mid-infrared devices show quantum efficiencies of about 0.1% due to the much weaker emission. These devices relied exclusively on the interband transition, restricting the possible materials. Researchers at the University of Chicago showed electroluminescence at 5 µm using the intraband transition between 1Se and 1Pe states within the conduction band of core–shell HgSe–CdSe colloidal quantum dots. The 4.5% […]
Category Archives: Quantum dot
Qubits on strong stimulants
Science Daily January 27, 2023 Optically active semiconductor quantum dots have unparalleled photonic properties, but also modest spin coherence limited by their resident nuclei. The nuclear inhomogeneity has thus far bound all dynamical decoupling measurements to a few microseconds. An international team of researchers (UK, Austria) eliminated the inhomogeneity using lattice-matched GaAs–AlGaAs quantum dot devices and demonstrated dynamical decoupling of the electron spin qubit beyond 0.113(3) ms. Leveraging the 99.30(5)% visibility of our optical π-pulse gates, we use up to Nπ = 81 decoupling pulses and find a coherence times hundreds of microseconds. This scaling manifests an ideal refocusing of strong interactions between the electron and the […]
Study achieves the coherent manipulation of electron spins in silicon
Phys.org January 26, 2023 Electron spins in silicon quantum dots are excellent qubits because they have long coherence times and high gate fidelities, and compatible with advanced semiconductor manufacturing techniques. A team of researchers in the US (University of Rochester, industry) has shown that spin–valley coupling in Si, which drives transitions between states with different spin and valley quantum numbers, enables coherent control of single- and multi-electron spin states without oscillating electromagnetic fields. They demonstrated Rabi oscillations between effective single-spin states in a Si/SiGe double quantum dot that are driven by spin–valley coupling. Together with the exchange coupling between neighbouring electrons, […]
Quantum dots form ordered material
Science Daily November 1, 2022 It is possible to accurately design the electronic properties of quantum dots just by changing their size. However, to create functional devices, many dots have to be combined into a new material. During this process, the properties of the dots are often lost. Researchers in the Netherlands have made a highly conductive optoelectronic metamaterial through controlled ordering of colloidal quantum dots in three dimensions and over large areas achieving outstanding transport properties. The measured electron mobilities are the highest ever reported for a self-assembled solid of fully quantum-confined objects. This ultimately demonstrated that optoelectronic metamaterials […]
Getting quantum dots to stop blinking
Science Daily November 22, 2021 Quantum dots tendency to blink off at random intervals has hampered its use for biochemical applications. Researchers at MIT have come up with a way to control this unwanted blinking by firing a beam of mid-infrared laser light for an infinitesimal moment which eliminates the quantum dot’s blinking for a relatively long period. According to the researchers the cause of the blinking phenomenon probably has to do with extra electrical charges, such as extra electrons, attaching to the outer part of the quantum dots, altering the surface properties providing alternative pathways for the extra energy […]
Improving quantum dot interactions, one layer at a time
Science Daily November 20, 2020 Controlling interaction between quantum dots could greatly improve charge transport, leading to more efficient solar cells. Researchers fabricated CdTe quantum dot superlattices via the layer-by-layer assembly of positively charged polyelectrolytes and negatively charged CdTe quantum dots to control the dimension of the quantum resonance by independently changing the distances between quantum dots in the stacking (out-of-plane) and in-plane directions. They experimentally verified the miniband formation. The fabrication method can be used with other types of water-soluble quantum dots and nanoparticles. Combining different types of semiconductor quantum dots, or combining semiconductor quantum dots with other nanoparticles, […]
Nanocrystal ‘factory’ could revolutionize quantum dot manufacturing
Phys.org March 15, 2019 Researchers at North Carolina State University have developed a microfluidic system (called NC Factory) which starts with cesium lead bromide perovskite quantum dots and introduced various halide salts to precisely tune their fluorescence color across the entire spectrum of visible light. Anions in these salts replace the bromine atoms in the green-emitting dots with either iodine atoms (to move toward the red end of the spectrum) or chlorine atoms (to move toward blue). Coupled with continuous process monitoring, the system can precisely control both chemical composition and processing parameters. It can be used to continuously manufacture […]