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Non-radiative recombination at dislocations in InAs quantum dots grown on silicon
摘要： We study the impact of misfit dislocations on the luminescence from InAs quantum dots (QDs) grown on Si substrates. Electron channeling contrast imaging is used together with cathodoluminescence mapping to locate misfit dislocations and characterize the resulting nonradiative recombination of carriers via near-infrared light emission profiles. With a 5 kV electron beam probe, the dark line defect width due to a typical misfit dislocation in a shallow QD active layer is found to be approximately 1 lm, with a 40%–50% peak emission intensity loss at room temperature. Importantly, we find that at cryogenic temperatures, the dislocations affect the QD ground state and the first excited state emission significantly less than the second excited state emission. At the same time, the dark line defect width, which partially relates to carrier diffusion in the system, is relatively constant across the temperature range of 10 K–300 K. Our results suggest that carrier dynamics in the QD wetting layer control emission intensity loss at dislocations, and that these defects reduce luminescence only at those temperatures where the probability of carriers thermalizing from the dots into the wetting layer becomes significant. We discuss the implications of these findings toward growing dislocation-tolerant, reliable quantum dot lasers on silicon.
关键词： silicon substrates,nonradiative recombination,quantum dot lasers,InAs quantum dots,cathodoluminescence,misfit dislocations
更新于2025-09-16 10:30:52
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Sandwiching analytes with structurally diverse plasmonic nanoparticles on paper substrates for surface enhanced Raman spectroscopy
摘要： This report describes the systematic combination of structurally diverse plasmonic metal nanoparticles (AgNPs, AuNPs, Ag core–Au shell NPs, and anisotropic AuNPs) on flexible paper-based materials to induce signal-enhancing environments for surface enhanced Raman spectroscopy (SERS) applications. The anisotropic AuNP-modified paper exhibits the highest SERS response due to the surface area and the nature of the broad surface plasmon resonance (SPR) neighboring the Raman excitation wavelength. The subsequent addition of a second layer with these four NPs (e.g., sandwich arrangement) leads to the notable increase of the SERS signals by inducing a high probability of electromagnetic field environments associated with the interparticle SPR coupling and hot spots. After examining sixteen total combinations, the highest SERS response is obtained from the second layer with AgNPs on the anisotropic AuNP paper substrate, which allows for a higher calibration sensitivity and wider dynamic range than those of typical AuNP–AuNP arrangement. The variation of the SERS signals is also found to be below 20% based on multiple measurements (both intra-sample and inter-sample). Furthermore, the degree of SERS signal reductions for the sandwiched analytes is notably slow, indicating their increased long-term stability. The optimized combination is then employed in the detection of let-7f microRNA to demonstrate their practicability as SERS substrates. Precisely introducing interparticle coupling and hot spots with readily available plasmonic NPs still allows for the design of inexpensive and practical signal enhancing substrates that are capable of increasing the calibration sensitivity, extending the dynamic range, and lowering the detection limit of various organic and biological molecules.
关键词： SERS,surface enhanced Raman spectroscopy,interparticle coupling,microRNA detection,plasmonic nanoparticles,paper substrates,signal enhancement,hot spots
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Is Damp Heat Degradation of c-Si Modules Essentially Universal?
摘要： A pentacene (C22H14)-based high-voltage organic thin-film transistor (HVOTFT) was demonstrated on both a rigid and a flexible substrate. The HVOTFT showed minimal degradation of the current–voltage (I–V ) characteristics under flexure. Consistent with the previous reports on amorphous silicon (a-Si) TFTs, the offset drain/source structure enabled high-voltage operation, allowing for the HVOTFT to switch very large drain-to-source voltages (VDS > 300 V) with a relatively lower controlling voltage (0 V < VG < 20 V). The HVOTFT was evaluated with three different gate insulators to assess how the dielectric constant and interface states influence device performance. Due to the high electric field generated in the device, the HVOTFT suffered from impeded charge injection into the gated semiconductor channel, similar to that reported in a-Si-based high-voltage TFTs, as well as from a nonsaturating I–V characteristic behavior similar to the short-channel effects found in FETs. A field plate was implemented to improve charge injection into the gated semiconductor channel. Output characteristics of the HVOTFT were numerically corrected to demonstrate that the device I–V can be modeled with the existing Si-based FET models.
关键词： Flexible substrates,high-κ gate dielectrics,organic thin-film transistors (HVTFTs),high-voltage semiconductors
更新于2025-09-16 10:30:52
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[IEEE 2019 49th European Microwave Conference (EuMC) - Paris, France (2019.10.1-2019.10.3)] 2019 49th European Microwave Conference (EuMC) - Optimizing the Conductivity of Ink-Jet Printed Microwave Components on Polymer Substrates by Laser Sintering
摘要： In this work, microwave components were printed on a Kapton (polyimide) substrate using a Drop-On-Demand (DOD) ink jet printer with silver nanoparticle ink. Two different laser curing strategies are presented by implementing selective sintering. The measured improvement of the achieved conductivity is between 70 and 100% for such resonators from 5 to 15 GHz.
关键词： Kapton (PI),Electrical conductivity,Polymer substrates,laser sintering,Microwave components,Inkjet printing
更新于2025-09-16 10:30:52
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Demonstration of low forward voltage InGaN-based red LEDs
摘要： Here we report InGaN-based red light-emitting diodes (LEDs) grown on (201) β-Ga2O3 substrates. AlN/AlGaN strain-compensating layers and hybrid multiple-quantum-well structures were employed to improve the crystalline-quality of the InGaN active region. A bare LED showed that peak wavelength, light output power, and external quantum efficiency were 665 nm, 0.07 mW, and 0.19% at 20 mA, respectively. As its forward voltage was 2.45 V at 20 mA, the wall-plug efficiency was 0.14%. The characteristic temperature of the LEDs was 222 K at 100 mA evaluated from the temperature dependence of electroluminescence.
关键词： InGaN,β-Ga2O3 substrates,red LEDs,multiple-quantum-well structures,strain-compensating layers
更新于2025-09-16 10:30:52
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Remarkable Improvement in Foldability of Polya??Si Thina??Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Polya??Si Thina??Film Transistor Used for Foldable Displays
摘要： Highly robust poly-Si thin-film transistor (TFT) on polyimide (PI) substrate using blue laser annealing (BLA) of amorphous silicon (a-Si) for lateral crystallization is demonstrated. Its foldability is compared with the conventional excimer laser annealing (ELA) poly-Si TFT on PI used for foldable displays exhibiting field-effect mobility of 85 cm2 (V s)-1. The BLA poly-Si TFT on PI exhibits the field-effect mobility, threshold voltage (VTH), and subthreshold swing of 153 cm2 (V s)-1, -2.7 V, and 0.2 V dec-1, respectively. Most important finding is the excellent foldability of BLA TFT compared with the ELA poly-Si TFTs on PI substrates. The VTH shift of BLA poly-Si TFT is ±0.1 V, which is much smaller than that (±2 V) of ELA TFT on PI upon 30 000 cycle folding. The defects are generated at the grain boundary region of ELA poly-Si during folding. However, BLA poly-Si has no protrusion in the poly-Si channel and thus no defect generation during folding. This leads to excellent foldability of BLA poly-Si on PI substrate.
关键词： grain boundary,polyimide substrates,protrusions,flexible low-temperature poly-Si thin-film transistors,blue laser annealing
更新于2025-09-16 10:30:52
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High Performance Flexible Transparent Electrode via Onea??Step Multifunctional Treatment for Ag Nanonetwork Composites Semia??Embedded in Lowa??Temperaturea??Processed Substrate for Highly Performed Organic Photovoltaics
摘要： For ideal flexible transparent electrodes, the features of good electrical/optical properties, low surface roughness, efficient charge transportation, robust electrical stability under simultaneously continuous operation bias, and mechanical bending are critical. Herein, a flexible transparent electrode fulfilling all these features is demonstrated by silver (Ag) nanonetwork composites semi-embedded in low-temperature-processed colorless polyimide (cPI), which shows a figure of merit over 1000 (5.4 Ω sq?1 sheet resistance and >94% diffused transmission at 550 nm wavelength), extremely smooth topography (<1 nm root-mean-square roughness and <3 nm peak-to-valley roughness), remarkable bending stability under continuous operation bias, and increased work function favoring the band alignment with typical charge transport layers for efficient devices. These characteristics are attributed to one-step multifunctional chemical treatment on the composite of Ag nanowires and an example polymer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The strategic one-step process simultaneously offers selective welding at nanowires cross junctions to form an Ag nanonetwork, and removing polyvinylpyrrolidone surfactant from Ag nanowires and PSS from PEDOT:PSS. The flexible electrode also favors the residue-free cPI transfer for applications. Flexible organic solar cells (OSCs) made from the electrode achieve an averaged power conversion efficiency of 14.46% (best, 15.12%), which is the best flexible OSCs reported so far.
关键词： low-temperature substrates,silver nanonetworks,organic solar cells,chemical treatment,flexible transparent electrodes
更新于2025-09-16 10:30:52
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Plasmonic Gold Templates Enhancing Single Cell Lipidomic Analysis of Microorganisms
摘要： Single cell lipid profiling is a powerful tool to connect membrane composition and its changes within individual cells to specific biochemical functions or stimuli, but current approaches are inadequate due to the complex nature of the cells and technical limitation in analysis. Herein we report a new method with plasmonic substrates capable of cell localization and enhanced lipid ionization through thin-gold-film MALDI-MS. We performed lipidomic profiling of algae single cells with a 120-well microarray and identified more than 50 lipids in C. reinhardtii without an extraction process. The substrate was used for probing toxicological effect of herbicide atrazine on the algae’s lipidome, demonstrating molecular changes in glycerol lipid profiles. Fast location of cells with metal-enhanced fluorescence (MEF) and subsequent precise and direct ionization of the LDI process contribute to the enhanced performance, allowing for assessment of lipid changes concurrent with atrazine affected populations. This method that combines microarrays, MEF and MALDI-MS presents an effective platform for lipidomic study of single cells and for environmental toxicity study with microorganisms.
关键词： plasmonic substrates,MALDI-MS,atrazine,environmental toxicity,lipidomic profiling,single cell lipid profiling
更新于2025-09-16 10:30:52
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Direct Laser Annealing of Surface‐Enhanced Raman Scattering Substrates
摘要： A laser-annealing technique for the fabrication of surface-enhanced Raman scattering (SERS) substrates consisting of closely packed gold nanoparticles (AuNPs) with high densities and small separation distances is reported. Laser annealing enables strongly localized interaction between the laser spot and the colloidal AuNPs within the irradiation area. Multiple stages of the alternative spin-coating of colloidal AuNPs and laser-annealing processes enable filling of the gaps between the AuNPs by newly produced ones in the subsequent stages. Thus, both the fill factor and the distribution density of the AuNPs are increased largely with increasing the number of fabrication stages, which favors the improvement of the SERS performance. In contrast, the conventional furnace or hot-plate annealing heats the substrate and the colloidal film simultaneously, and the melted AuNPs tend to aggregate to form larger ones with large separation distance. Thus, compared with the SERS effective by furnace-annealed substrates, laser-annealed substrates supply a further enhancement factor larger than 3.7. Thus, laser annealing is proved as a more effective approach for the fabrication of SERS substrates through annealing colloidal AuNPs.
关键词： direct laser annealing,furnace annealing,gap widths,surface-enhanced Raman scattering substrates,fill factors,closely packed gold nanoparticles
更新于2025-09-12 10:27:22
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A linear D–π–A based hole transport material for high performance rigid and flexible planar organic–inorganic hybrid perovskite solar cells
摘要： A facile and less expensive hole transport material is essential to enhance the power conversion efficiency (PCE) of perovskite solar cells (PSC) without compromising the ambient stability. Here, we designed and synthesized a new class of HTM by introducing donor–π–acceptor (D–π–A). The HTM was synthesized by combining the moieties of triphenylamine, biphenyl and oxadiazole derivatives as electron donating, π-spacer and electron withdrawing moieties, respectively, named 4′-(5-(4-(hexyloxy)phenyl)-1,3,4-oxadiazol-2-yl)-N,N-bis(4-methoxyphenyl)-[1,1′:4′,1′′:4′′,1′′′-quaterphenyl]-4-amine (TPA-BP-OXD). The π–π conjugation is increased by introducing the biphenyl π-spacer. The HTM was terminated with an OXD-based moiety and framed as a D–π–A-based HTM that trigged improvement in the charge transportation properties due to its π–π interactions. We rationally investigated the HTM by characterizing its photophysical, thermal, electrochemical, and charge transport properties. The great features of the HTM stimulated us to explore it on rigid and flexible substrates as a dopant-free HTM in planar inverted-perovskite solar cells (i-PSCs). The device performance in solution processed dopant-free HTM based i-PSC devices on both rigid and flexible substrates showed PCEs of 15.46% and 12.90%, respectively. The hysteresis is negligible, which is one of the most effective results based on a TPA-BP-OXD HTM in planar i-PSCs. The device performance and stability based on the TPA-BP-OXD HTM are better due to higher extraction and transportation of holes from the perovskite material, reduced charge recombination at the interface, and enhanced hydrophobicity of the HTM to compete for a role in enhancing the stability. Overall, our findings demonstrate the potentiality of the TPA-BP-OXD based HTM in planar i-PSCs.
关键词： perovskite solar cells,hole transport material,donor–π–acceptor,power conversion efficiency,flexible substrates
更新于2025-09-12 10:27:22