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- 2020
- Purcell factor
- Plasmonics
- Single-molecule
- Nano-assembly
- Nanocavities
- Lipid bilayers
- Physics
- University of Cambridge
- University of Leeds
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Composition and Strain Evolution of Undoped Si <sub/>0.8</sub> Ge <sub/>0.2</sub> Layers Submitted to UV-Nanosecond Laser Annealing
摘要： Ultraviolet Nanosecond Laser Annealing (UV-NLA, XeCl laser, 308 nm, 145 ns) was performed on 30 nm-thick Si0.8Ge0.2 epitaxial layers. The various regimes encountered after single pulse UV-NLA are described and discussed, including submelt, SiGe layer partial and total melt, as well as melt beyond the SiGe epi-layer. Energy densities around 2.00 J/cm2 and above led to the formation of pseudomorphic layers with strong Ge redistribution. Starting from uniform Si0.8Ge0.2 layers, Ge segregation towards the surface resulted in the formation of a Ge-rich surface layer with up to 55% Ge for 2.00 J/cm2. Such pseudomorphic SiGe layers with graded composition and a Ge-rich surface layer may find some promising applications such as contact resistance lowering in doped layers.
关键词： SiGe,pseudomorphic,contact resistance,Ge redistribution,Ultraviolet Nanosecond Laser Annealing
更新于2025-11-14 14:32:36
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Double- and Multi-Femtosecond Pulses Produced by Birefringent Crystals for the Generation of 2D Laser-Induced Structures on a Stainless Steel Surface
摘要： Laser-induced textures have been proven to be excellent solutions for modifying wetting, friction, biocompatibility, and optical properties of solids. The possibility to generate 2D-submicron morphologies by laser processing has been demonstrated recently. Employing double-pulse irradiation, it is possible to control the induced structures and to fabricate novel and more complex 2D-textures. Nevertheless, double-pulse irradiation often implies the use of sophisticated setups for modifying the pulse polarization and temporal profile. Here, we show the generation of homogeneous 2D-LIPSS (laser-induced periodic surface structures) over large areas utilizing a simple array of birefringent crystals. Linearly and circularly polarized pulses were applied, and the optimum process window was defined for both. The results are compared to previous studies, which include a delay line, and the reproducibility between the two techniques is validated. As a result of a systematic study of the process parameters, the obtained morphology was found to depend both on the interplay between fluence and inter-pulse delay, as well as on the number of incident pulses. The obtained structures were characterized via SEM (scanning electron microscopy) and atomic force microscopy. We believe that our results represent a novel approach to surface structuring, primed for introduction in an industrial environment.
关键词： metal surface texturing,2D-LIPSS,femtosecond,micro/nanostructuring,birefringent crystals,double pulses
更新于2025-11-14 14:32:36
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Anisotropic infrared light emission from quasi-one-dimensional layered TiS<sub>3</sub>
摘要： Atomically thin semiconductors hold great potential for nanoscale photonic and optoelectronic devices because of their strong light absorption and emission. Despite progress, their application in integrated photonics is hindered particularly by a lack of stable layered semiconductors emitting in the infrared part of the electromagnetic spectrum. Here we show that titanium trisulfide (TiS3), a layered van der Waals material consisting of quasi-one-dimensional chains, emits near infrared light centered around 0.91 eV (1360 nm). Its photoluminescence exhibits linear polarization anisotropy and an emission lifetime of 210 ps. At low temperature, we distinguish two spectral contributions with opposite linear polarizations attributed to excitons and defects. Moreover, the dependence on excitation power and temperature suggests that free and bound excitons dominate the excitonic emission at high and low temperatures, respectively. Our results demonstrate the promising properties of TiS3 as a stable semiconductor for optoelectronic and nanophotonic devices operating at telecommunication wavelengths.
关键词： infrared luminescence,transition metal trichalcogenides,titanium trisulfide,linear polarization anisotropy,layered semiconductors
更新于2025-11-14 14:32:36
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Nano-Heteroepitaxy: An Investigation of SiGe Nano-Pillars Coalescence
摘要： In this paper, SiGe nano-pillars coalescence was investigated using industrial Reduced Pressure-Chemical Vapour Deposition integration scheme based on diblock copolymer patterning provided nanometer size templates for the selective epitaxy of SiGe 25% nano-pillars. In order to study merging, thicknesses ranging from 20 to 35 nm were grown and samples characterized by AFM, XRD, SSRM and TEM. The evolution in terms of grains shape, size and number was examined, with individual pillars merging into larger grains above 30 nm thickness. High degrees of macroscopic strain relaxation were obtained at the different stages of nano-pillars merging. Defects such as stacking faults and twins were identified as occurring at the early stages of nano-pillar coalescence.
关键词： SSRM,TEM,coalescence,AFM,SiGe nano-pillars,Reduced Pressure-Chemical Vapour Deposition,XRD
更新于2025-11-14 14:32:36
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Single process CVD growth of hBN/Graphene heterostructures on copper thin films
摘要： In this study, we have successfully grown hBN/graphene heterostructures on copper thin films using chemical vapor deposition in a single process. The first and most surprising result is that graphene grows underneath hBN and adjacent to the Cu film even though it is deposited second. This was determined from cross-sectional TEM analysis and XPS depth profiling, which chemically identified the relative positions of hBN and graphene. The effect of various growth conditions on graphene/hBN heterostructures was also studied. It was found that a pressure of 200 torr and a hydrogen flow rate of 200 sccm (;1 H2/N2) yielded the highest quality of graphene, with full surface coverage occurring after a growth time of 120 min. The resulting graphene films were found to be approximately 6–8 layers thick. The grain size of the nanocrystalline graphene was found to be 15–50 nm varying based on growth conditions.
关键词： XPS depth profiling,copper thin films,TEM analysis,hBN/graphene heterostructures,chemical vapor deposition
更新于2025-11-14 14:32:36
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Dynamically Switching the Electronic and Electrostatic Properties of Indium Tin Oxide Electrodes with Photochromic Monolayers: Toward Photo-Switchable Optoelectronic Devices
摘要： The chemical modification of electrodes with organic materials is a common approach to tune the electronic and electrostatic landscape between interlayers in optoelectronic devices, thus facilitating charge injection at the electrode/semiconductor interfaces and improving their performance. The use of photochromic molecules for the surface modification allows dynamic control of the electronic and electrostatic properties of the electrode and thereby enables additional functionalities in such devices. Here, we show that the electronic properties of a transparent indium tin oxide (ITO) electrode are reversibly and dynamically modified by depositing organic photochromic switches (diarylethenes) in the form of self-assembled monolayers (SAMs). By combining a range of surface characterization and density functional theory calculations, we present a detailed picture of the SAM binding onto ITO, the packing density of molecules, their orientation, as well as the work function modification of the ITO surface due to the SAM deposition. Upon illumination with ultraviolet and green light, we observe a reversible shift of the frontier occupied levels by 0.7 eV, and concomitantly a reversible work function change of ca. 60 meV. Our results prove the viability of dynamic switching of the electronic properties of the electrode with external light stimuli upon modification with a monolayer of photochromic molecules, which could be used to fabricate ITO-based photo-switchable optoelectronic devices.
关键词： self-assembled monolayer,diarylethene,ITO,photochromic switch,interface electronic properties
更新于2025-11-14 14:32:36
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TiO2-Coated Core-Shell Ag Nanowire Networks for Robust and Washable Flexible Transparent Electrodes
摘要： Silver nanowires (AgNWs) are the most promising materials to fabricate flexible transparent electrodes (FTEs) used in next-generation electronics. However, there are several bottlenecks for AgNWs-based FTEs to achieve large-scale applications, which are the thermal instability and rough surface topography of AgNWs and the poor interfacial adhesion between AgNWs and used substrate. To simultaneously address these aforementioned issues, a robust and washable FTE is prepared based on AgNW@TiO2 core-shell network embedding in polyimide (PI) substrate through a facile and scalable solution-based process. After treating with TiO2 sol, an ultra-thin, conformal, and continuous TiO2 shell is coated on AgNWs, which can effectively suppress the atomic surface diffusion. In comparison with pristine AgNW network that breaks into nanorods and nanospheres at 250 °C for 10 min, the AgNW@TiO2 core-shell network is stable at 300 °C, and its resistance just increases by a factor of 11 after annealing at 400 °C for 1 h. Furthermore, the TiO2 shell simultaneously increases the electrical and optical properties of AgNW network. After flowing PI precursors, drying, and thermally curing, the AgNW@TiO2 core-shell network is embedded on the surface of PI substrate with surface roughness of 1.9 nm. In addition to high thermal stability, the conductivity of the AgNWs@TiO2-PI composite FTE remains almost unchanged after repeated 3M tape peeling off cycles and mechanical bending cycles. It is also demonstrated that the AgNWs@TiO2-PI composite FTE is washable, and the relative change in resistance (?R/R0) is ~12% after 100 washing cycles in which a variety of stress situations occurring in combination.
关键词： flexible transparent electrodes,peeling off and mechanical stabilities,TiO2 sol,silver nanowire@TiO2 core-shell network,thermal and washing stabilities
更新于2025-11-14 14:32:36
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Synchronous surface and bulk composition management for red-shifted light absorption and suppressed interfacial recombination in perovskite solar cells
摘要： Organic small molecules ammonium halide salts (AHSs) are widely used to suppress the non-radiative charge recombination of solution-processed halide perovskite films with defective surface and unfavorable energy level for enhanced photovoltage, but more often than not at a cost of enlarging the bandgap of perovskite materials, which limits the light absorption and thus photocurrent density. In addition, there is still a lack of fundamental understanding and visual characterization of the surface and bulk composition change upon subsequent surface treatment with heterogeneous ingredients. Herein, we report and identify that AHS soaking treatment enables the formation of δ-FAPbI3 on the surface of the perovskite film for defect passivation function, thus reducing the interfacial recombination loss and increasing photovoltage. Meanwhile, the AHS molecules diffuse and alloy with the bulk perovskite material to reduce the bandgap, red-shifting the absorption region and thus increasing the photocurrent. Blade-coated perovskite solar cells (PSCs) prepared via AHS treatment achieved a champion power conversion efficiency (PCE) of 21.9% with a high open-circuit voltage (Voc) up to 1.18 V under AM 1.5G sun illumination, which is remarkably higher than the pristine PSCs without any treatment (19.2%), and outperforms other blade-coated PSCs, regardless of their perovskite compositions. Surface treatment of perovskite films with functional, organic small molecules is a promising strategy for rational composition management and favorable gradient distribution, which are beneficial for realizing efficient and stable PSCs.
关键词： light absorption,perovskite,charge transfer,defect passivation,solar cells
更新于2025-09-23 15:19:57
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Out-of-Plane Nanoscale Reorganization of Lipid Molecules and Nanoparticles Revealed by Plasmonic Spectroscopy
摘要： Lipid bilayers assembled on solid substrates have been extensively studied with single-molecule resolution as the molecules diffuse in 2D, however the out-of-plane motion is typically ignored. Here we present sub-nanometer out-of-plane diffusion of nanoparticles attached to hybrid lipid bilayers (HBLs) assembled on metal surfaces. The nanoscale cavity formed between Au nanoparticle and Au film provides strongly-enhanced optical fields capable of locally probing HBLs assembled in the gaps. This allows us to spectroscopically resolve the nanoparticles assembled on bilayers, near edges, and in membrane defects, showing the strong influence of charged lipid rafts. Nanoparticles sitting on the edges of the HBL are observed to flip onto and off the bilayer, with flip energies of 10 meV showing how thermal energies dynamically modify lipid arrangements around a nanoparticle. We further resolve the movement of individual lipid molecules by doping the HBL with low concentrations of Texas-red (TxR) dye-labeled lipids.
关键词： Purcell factor,Plasmonics,Single-molecule,Nano-assembly,Nanocavities,Lipid bilayers
更新于2025-09-23 15:19:57
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Multicolor nanobubbles for FRET/ultrasound dual-modal contrast imaging
摘要： Engineering compositions, structures, and defects can endow nanomaterials with optimized catalytic properties. Here, we report that cobalt oxide (CoOx) ultrathin nanosheets (UTNS, ～1.6 nm thick) with a large number of oxygen defects and mixed cobalt valences can be obtained through a facile one-step hydrothermal protocol. The large number of oxygen defects make the ultrathin CoOx nanosheet a superior OER catalyst with low overpotentials of 315 and 365 mV at current densities of 50 and 200 mA cm?2, respectively. The stable framework-like architectures of the UTNS further ensure their high OER activity and durability. Our method represents a facile one-step preparation of CoOx nanostructures with tunable compositions, morphologies, and defects, and thus promotes OER properties. This strategy may find its wider applicability in designing active, robust, and easy-to-obtain catalysts for OER and other electrocatalytic systems.
更新于2025-09-19 17:15:36