| 1. |
- Chen, Yang, et al.
(författare)
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Compact spin-valley-locked perovskite emission
- 2023
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Ingår i: Nature Materials. - : NATURE PORTFOLIO. - 1476-1122 .- 1476-4660.
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Tidskriftsartikel (refereegranskat)abstract
- Circularly polarized light sources with free-space directional emission play a key role in chiroptics(1), spintronics(2), valleytronics(3) and asymmetric photocatalysis(4). However, conventional approaches fail to simultaneously realize pure circular polarization, high directionality and large emission angles in a compact emitter. Metal-halide perovskite semiconductors are promising light emitters(5-8), but the absence of an intrinsic spin-locking mechanism results in poor emission chirality. Further, device integration has undermined the efficiency and directionality of perovskite chiral emitters. Here we realize compact spin-valley-locked perovskite emitting metasurfaces where spin-dependent geometric phases are imparted into bound states in the continuum via Brillouin zone folding, and thus, photons with different spins are selectively addressed to opposite valleys. Employing this approach, chiral purity of 0.91 and emission angle of 41.0 degrees are simultaneously achieved, with a beam divergence angle of 1.6 degrees. With this approach, we envisage the realization of chiral light- emitting diodes, as well as the on-chip generation of entangled photon pairs.
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| 2. |
- Dick, K. A., et al.
(författare)
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Measuring the properties of semiconductor nanowires with transmission electron microscopy
- 2015
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Ingår i: Semiconductor Nanowires : Materials, Synthesis, Characterization and Applications - Materials, Synthesis, Characterization and Applications. - 9781782422532 - 9781782422631 ; , s. 203-219
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Bokkapitel (refereegranskat)abstract
- The extremely small feature size and total sample volume of semiconductor nanowire materials has meant that advanced techniques have been required for even the most routine sample characterization since the structures were first reported. Electron microscopy has been the technique of choice for fast and reliable determination of nanowire morphology, structure, and composition since the earliest reports. In particular, the high resolution of transmission electron microscopy (TEM), together with the reasonably high throughput and relatively simple sample preparation, has made this technique necessary for characterization of all reported nanowire materials.On the other hand, TEM is also a powerful technique not only for routine analysis, but for detailed characterization of specific structural, compositional, and physical properties of semiconductor nanowires. The relative flexibility of the technique has also allowed it to be combined with a wide variety of experiment types for in situ investigations of nanowire growth, properties, and response to stimuli.In this chapter the use of TEM to characterize a variety of nanowire properties will be reviewed. The most widely used methods will be described, together with a survey of more advanced measurements performed using the wide array of measurement possibilities that the TEM has to offer. Indeed, it will be clear that the extreme versatility of this instrument is one of the most important reasons for its central role in the development of semiconductor nanowire materials today.
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| 3. |
- Li, Guohui, et al.
(författare)
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Localized Bound Multiexcitons in Engineered Quasi-2D Perovskites Grains at Room Temperature for Efficient Lasers
- 2023
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:20
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the excitation threshold to minimize the Joule heating is critical for the realization of perovskite laser diodes. Although bound excitons are promising for low threshold laser, how to generate them at room temperature for laser applications is still unclear in quasi-2D perovskite-based devices. In this work, via engineering quasi-2D perovskite PEA2(CH3NH3)n-1PbnBr3n+1 microscopic grains by the anti-solvent method, room-temperature multiexciton radiative recombination is successfully demonstrated at a remarkably low pump density of 0.97 µJ cm−2, which is only one-fourth of that required in 2D CdSe nanosheets. In addition, the well-defined translational momentum in quasi-2D perovskite grains can restrict the Auger recombination which is detrimental to radiative emission. Furthermore, the quasi-2D perovskite grains are favorable for increasing binding energies of excitons and biexcitons and so as the related radiative recombination. Consequently, the prepared phase quasi-2D perovskite film renders a threshold of room-temperature stimulated emission as low as 13.7 µJ cm−2, reduced by 58.6% relative to the amorphous counterpart with larger grains. The findings in this work are expected to facilitate the development of solution-processable perovskite multiexcitonic laser diodes.
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| 4. |
- Li, Guohui, et al.
(författare)
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Room-Temperature Single-Mode Plasmonic Perovskite Nanolasers with Sub-Picosecond Pulses
- 2024
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Ingår i: Advanced Functional Materials. - 1616-301X.
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Tidskriftsartikel (refereegranskat)abstract
- With the explosive growth of communication traffic, increasing the modulation bandwidth of semiconductor lasers has attracted significant attention. However, after rapid progress is achieved, further increasing the modulation bandwidth of semiconductor lasers is hampered by the slow charge-carrier dynamics. Here, a room temperature, single-mode perovskite nanolaser with sub-picosecond pulses, enabled by high Purcell enhancement is reported. This enhancement is achieved via transferring an atomically smooth perovskite nanoplatelet onto the surface of an ultra-smooth SiO2/Ag film. This nanolaser features a low mode volume (V) as low as 0.137 µm3, a high-quality factor (Q) up to 2180, and a low lasing threshold of 36.65 µJ cm−2. The Q value of the laser is one order of magnitude higher than that of state-of-the-art nanolasers. The smoothness of both the nanoplatelet and the SiO2/Ag film in the laser is critical to achieving a high Purcell enhancement. Polarization analysis reveals that the laser emission consists of a transvere-magnetic (TM) polarized surface plasmon mode and a transverse-electric (TE) polarized photonic mode. Furthermore, ultrafast charge-carrier dynamics indicate the surface plasmon decay time can be as short as 0.6 ± 0.4 ps due to the high Purcell enhancement. This work opens up the possibility of developing nanolasers with high bandwidths and ultra-small sizes.
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