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- 2018
- electron-transparent membranes
- micropump
- field emission electron source
- ion source
- ion mobility spectrometry
- Optoelectronic Information Science and Engineering
- Wroclaw University of Science and Technology
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Board‐like Fused‐Thiophene Liquid Crystals and Their Benzene Analogues: Facile Synthesis, Self‐assembly, p‐Type Semiconductivity, and Photoluminescence
摘要： Novel fused-thiophene discotic liquid crystals were designed and easily synthesized by Suzuki coupling and FeCl3 oxidized tandem cyclo-dehydrogenation reactions, including homo- and cross-coupling reactions. The resulting hexagonal and rectangular columnar mesomorphic supramolecular structures formed were characterized by polarizing optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. Charge carrier transport properties in the mesophases of two of the synthesized fused-thiophene discogens were measured by transient photocurrent time-of-flight (TOF) technique, revealing fast hole transport values in the range of 10-3 to 10-2 cm2 V-1s-1, thus demonstrating potential applications in electronic devices. The luminescent sanidic mesogens, having different extended π-conjugated systems, also emit blue, green or red light, with absolute photoluminescent quantum yields as high as 18%.
关键词： thiophene,luminescence,mesophase,cyclo-hydrogenation,charge mobility
更新于2025-09-04 15:30:14
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Tunable Direct Semiconductor Gap and High Carrier Mobility of Mo <sub/>6</sub> Br <sub/>6</sub> S <sub/>3</sub> Monolayer
摘要： Two-dimensional materials with direct semiconductor gaps and high mobilities can play an important role in future electronic and optical applications. Here we propose that Mo6Br6S3 monolayer as a new two-dimensional material is stable and can be exfoliated from corresponding layered bulk. Our first-principles results show that the monolayer has a direct semiconductor gap beyond 1 eV (between PBE and HSE values) and a very high electron mobility (6880 cm2V?1s?1), and these can be tuned through in-plane strain by applying uniaxial stress. Furthermore, we show that the Mo6Br6S3/graphene heterostructure makes a p-type Schottky barrier and the amplitude of band bending (0.03 eV) is extremely low compared to other similar junctions because the Mo6Br6S3 monolayer has a close work function to graphene. With all these useful properties and functions, the Mo6Br6S3 monolayer can be very promising for nanoelectronic and optical applications.
关键词： Mo6Br6S3 monolayer,p-type Schottky barrier,optical applications,Two-dimensional materials,electron mobility,high mobilities,first-principles,direct semiconductor gaps,nanoelectronic
更新于2025-09-04 15:30:14
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Electron Transport with Mobility, μ > 86 cm2/Vs, in a 74 nm Long Polyfluorene
摘要： The mobility of charges on conjugated polymers is a fundamentally important feature of these materials, but most fall far short of transport that might lead one to call them “molecular wires”. A commonly identified bottleneck is flexible dihedral angles between repeat units. Here we find a very high mobility, μ > 86 cm2/Vs, for electrons attached to polyfluorene polymers in isooctane, despite the presence of varied dihedral angles. The present data suggests that interactions with the surrounding medium may be a principal determinant of charge mobility.
关键词： mobility,molecular wires,conjugated polymers,polyfluorene,electron transport
更新于2025-09-04 15:30:14
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The Role of Humidity in Tuning the Texture and Electrical Properties of Cu <sub/>2</sub> O Thin Films Deposited via Aerosol‐Assisted CVD
摘要： A study on the effect of carrier gas (CG) humidity on the texture and the resulting electronic properties of Cu2O thin films deposited using aerosol-assisted chemical vapor deposition (AA-CVD) at low temperatures (<365 °C) is reported. By increasing the CG humidity, the preferred orientation of the films can be tuned from [110] to [111]. By studying the initial stages of film deposition, a different growth mode is found for dry and humid conditions, which in turn directs the final texture of the films. The analysis of the electric properties of the films by Hall effect shows that carrier concentration remains in the order of 1015 cm?3 when using both dry and humid conditions. Conversely, Cu2O samples deposited with humid CG generally present a higher mobility, up to 17 cm2 V?1 s?1. [111]-textured Cu2O films with high mobility were used to fabricate a diode by depositing a ZnO layer on top using atmospheric pressure spatial atomic layer deposition (AP-SALD). The diode shows an excellent rectifying behavior with a high asymmetry close to 104 between ?1 and +1 V.
关键词： textured thin films,copper oxides,aerosol-assisted CVD,carrier mobility,atmospheric pressure processing
更新于2025-09-04 15:30:14
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Research on Time Jitter of GaAs Photoconductive Semiconductor Switches in the Negative Differential Mobility Region
摘要： Time jitter of GaAs photoconductive semiconductor switches (PCSS) is investigated at an optical excitation of 1053 nm wavelength and 500 ps pulse duration. The experimental results indicate that the time jitter of the GaAs PCSS exhibits a nonmonotonic variation in negative differential mobility (NDM) region. All of these time jitters are lower than the 4% of the rise time of the switching waveform. The optimum time jitter of ~15 ps is achieved at the onset of the NDM region. The theoretical relationship between the optical excitation parameters, the bias electric field and the time jitter of the GaAs PCSS are built up. The nonmonotonic behavior of the time jitter with electric field is attributed to the instability of the relative fluctuation of drift velocity caused by inter-valley transition of carriers in GaAs.
关键词： inter-valley transition of carriers,photoconductive semiconductor switches,gallium arsenide (GaAs),negative differential mobility (NDM),time jitter
更新于2025-09-04 15:30:14
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Quantitative mobility evaluation of organic semiconductors using quantum dynamics based on density functional theory
摘要： We present an order-N methodology to evaluate mobilities of charge carriers coupled with molecular vibrations using quantum dynamics based on first-principles calculations that can be applied to micron-scale soft materials. As a demonstration, we apply it to several organic semiconductors and show that the calculated intrinsic hole mobilities and their temperature dependences are quantitatively in good agreement with those obtained in experiments. We also clarified which vibrational modes dominate the transport properties. The methodology paves the way for quantitative prediction of the transport properties of various soft materials.
关键词： quantum dynamics,density functional theory,charge-carrier mobility,organic semiconductors,molecular vibrations
更新于2025-09-04 15:30:14
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Impact of Low‐Frequency Vibrations on Charge Transport in High‐Mobility Organic Semiconductors
摘要： Despite decades of intensive studies of charge transport in organic semiconductors (OSs), understanding of mechanisms underpinning efficient charge transport in them remains elusive. Recently, it has been suggested that low-frequency (LF) vibrations are a limiting factor of charge transport in high-mobility OSs. Nevertheless, the relationship between the molecular structure, crystal packing, LF vibrations, and charge transport is still obscured. This hinders the focused search of high-mobility OSs so that researchers rely mainly on trial-and-error method. This review presents theoretical and experimental approaches to studying the LF vibrations and their role in charge transport with a focus on recent results. It is anticipated that tight cooperation between experimentalists and theorists will yield an advanced understanding of LF vibrations in OSs and their impact on charge transport. This will guide the design of novel high-mobility organic semiconductors for organic electronics.
关键词： structure–property relationship,organic electronics,Raman spectroscopy,electron–phonon interaction,charge mobility
更新于2025-09-04 15:30:14
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Confocal Fluorescence Microscopy and Kinetics of the Cr3+-Chromate Ion Oxidation Equilibria at the Solid Liquid Interface
摘要： Silica-borax pearl samples impregnated with 0.17 and 0.64% Cr3+ were characterized by specific surface area measurements, UV-Vis spectroscopy, energy-dispersive X-ray fluorescence and laser-scanning confocal microscopy. Pearl stability against oxidizing conditions was tested by adding samples to an aqueous hydrogen peroxide solution. The reaction was examined by UV-Vis spectroscopic measurements of the supernatant and laser-scanning confocal microscopy images of the substrate. Overall, hydrogen peroxide-induced Cr3+ to Cr6+ oxidation across the solid-liquid interface promoted solid matrix cleavage pearl degradation and concomitant formation of multiple scattering centers was observed. A dual-detection scheme was employed in the confocal microscopy measurements allowing us to separate scattering and absorptive contributions to the observed signals. The confocal microscopy images indicate that Cr3+ oxidation induced by hydrogen peroxide solutions occurs throughout the entire pearl sample and indicate that oxidation reactions induce leakage of chromate ion into aqueous solutions.
关键词： energy dispersive X-ray fluorescence,confocal fluorescence microscopy,chromium mobility,H2O2 oxidation equilibria,mass transfer phenomena,solid liquid interfaces
更新于2025-09-04 15:30:14
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Ultra-wide bandgap, conductive, high mobility, and high quality melt-grown bulk ZnGa <sub/>2</sub> O <sub/>4</sub> single crystals
摘要： Truly bulk ZnGa2O4 single crystals were obtained directly from the melt. High melting point of 1900 ± 20 ?C and highly incongruent evaporation of the Zn- and Ga-containing species impose restrictions on growth conditions. The obtained crystals are characterized by a stoichiometric or near-stoichiometric composition with a normal spinel structure at room temperature and by a narrow full width at half maximum of the rocking curve of the 400 peak of (100)-oriented samples of 23 arcsec. ZnGa2O4 is a single crystalline spinel phase with the Ga/Zn atomic ratio up to about 2.17. Melt-grown ZnGa2O4 single crystals are thermally stable up to 1100 and 700 ?C when subjected to annealing for 10 h in oxidizing and reducing atmospheres, respectively. The obtained ZnGa2O4 single crystals were either electrical insulators or n-type semiconductors/degenerate semiconductors depending on growth conditions and starting material composition. The as-grown semiconducting crystals had the resistivity, free electron concentration, and maximum Hall mobility of 0.002–0.1 ?cm, 3 × 1018–9 × 1019 cm?3, and 107 cm2 V?1 s?1, respectively. The semiconducting crystals could be switched into the electrically insulating state by annealing in the presence of oxygen at temperatures ≥700 ?C for at least several hours. The optical absorption edge is steep and originates at 275 nm, followed by full transparency in the visible and near infrared spectral regions. The optical bandgap gathered from the absorption coef?cient is direct with a value of about 4.6 eV, close to that of β-Ga2O3. Additionally, with a lattice constant of a = 8.3336 ?, ZnGa2O4 may serve as a good lattice-matched substrate for magnetic Fe-based spinel ?lms.
关键词： high mobility,melt growth,high quality,ultra-wide bandgap,conductive,single crystals,ZnGa2O4
更新于2025-09-04 15:30:14