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Mobility of charge carriers in self-assembled monolayers
摘要： We present a new approach to study charge transport within 2D layers of organic semi-conductors (OSCs) using atomic force microscopy (AFM)-based lithography applied to self-assembled monolayers (SAMs), fabricated from appropriate organothiols. The extent of lateral charge transport was investigated by insulating pre-defined patches within OSC-based SAMs with regions of insulating SAM made from large band gap alkanethiolates. The new method is demonstrated using a phenyl-linked anthracenethiolate (PAT), 4-(anthracene-2-ylethynyl)benzyl thiolate. I–V characteristics of differently shaped PAT-islands were measured using the AFM tip as a top electrode. We were able to determine a relationship between island size and electrical conductivity, and from this dependence, we could obtain information on the lateral charge transport and charge carrier mobility within the thin OSC layers. Our study demonstrates that AFM nanografting of appropriately functionalized OSC molecules provides a suitable method to determine intrinsic mobilities of charge carriers in OSC thin films. In particular, this method is rather insensitive with regard to influence of grain boundaries and other defects, which hamper the application of conventional methods for the determination of mobilities in macroscopic samples.
关键词： organic semiconductor,self-assembled monolayer,lateral charge transport,nanografting,conducting atomic force microscopy
更新于2025-09-12 10:27:22
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High-selectivity NOx sensors based on an Au/InGaP Schottky diode functionalized with self-assembled monolayer of alkanedithiols
摘要： This work was devoted to fabricating high-selectivity NOx gas sensors based on an Au/InGaP Schottky diode. In order to enhance the sensing selectivity and sensing response, a self-assembled monolayer (SAM) of alkanedithiol was used to modify the Schottky contact with an S-Au covalent bond based on the self-assembled property and terminal functional group. The studied SAM/Au/InGaP Schottky diodes were fabricated by semiconductor processes and immersion treatment. The effects of the carbon number (CN) of SAM, the SAM immersion time, and immersion dithiol concentrations were comprehensively studied in this work. In addition, the selectivity and sensing performance of dithiol functionalized Au/InGaP Schottky diodes under different temperatures and NOx concentrations were studied for comparison. In order to obtain the optimal NOx sensing performance, cyclic voltammetry (CV) was employed to study the self-assembled performance of the dithiol monolayer on the Au surface. The sensing responses of 16.5 and 7.2 were obtained under 100 ppm NO2/N2 and NO/N2 at 30oC, respectively, for the studied 1,10-decanedithiol (DDT)/Au/InGaP device. Moreover, compared to other sensing gases, the DDT/Au/InGaP sensing device showed high selectivity toward NOx gas. Furthermore, the theoretical first-order kinetic and thermodynamic theoretical analysis were consistent with the experimental transient and steady-state sensing results. Therefore, the studied SAM/Au/InGaP Schottky diode demonstrated promising results for NOx sensing applications.
关键词： Nitrogen oxides,Gas sensors,Schottky diode,Self-assembled monolayers (SAM),InGaP,Alkanedithiol
更新于2025-09-12 10:27:22
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Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers
摘要： Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.
关键词： four-dimensional (4D) functional nano-materials,nano-optics,non-paraxial light fields,self-assembled monolayers (SAMs),polarization nano-tomography
更新于2025-09-12 10:27:22
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Production of Three-Dimensional ZnO Multilayered Structures from Self-Assembled ZnO Microdiscs
摘要： Three-dimensional (3D) zinc oxide (ZnO) multilayered structures with diameters as large as 26.7 lm are obtained in this work in thin-?lm form. The 1-lm-thick ?lms are produced using the spray pyrolysis method on glass substrates at a substrate temperature of 350 ± 5(cid:2)C. X-ray diffraction, scanning electron microscopy (SEM), and x-ray energy-dispersive spectroscopy are used to characterize the ?lms. X-ray diffraction revealed that the ZnO ?lms display hexagonal phase with high crystallinity. Scanning electron microscope (SEM) observations showed that the three-dimensional structures are formed from self-assembled ZnO microdiscs. Assembling of the microdiscs and formation of the multilayered structures occurred spontaneously during the deposition process without the aid of any surfactant. This route for the production of ZnO three-dimensional structures is cheap, very simple, and can be used in industrial applications such as gas sensors, electronic devices, and solar cells.
关键词： ZnO,self-assembled microdiscs,three-dimensional structures,spray pyrolysis,multilayered structures
更新于2025-09-12 10:27:22
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Towards scalable fabrication of atomic wires in silicon by nano-patterning self-assembled molecular monolayers
摘要： Developing a scalable method to fabricate atomic wires is an important step for building solid-state semiconductor quantum computers. In this work, we developed a selective doping strategy by patterning the self-assembled monolayer to a few nanometers using standard nanofabrication processes, which significantly improves the lateral doping resolution of monolayer doping (MLD) from microscale to nanoscale. Using this method, we further explore the possibility to fabricate phosphorus wires in silicon by patterning self-assembled diethyl vinylphosphonate monolayers into lines with a width ranging from 500 nm to 10 nm. The phosphorus dopants are driven into silicon by rapid thermal annealing, forming dopant wires. Four-probe and Hall effect measurements are employed to characterize the dopant wires. The results show that the conductance is linear with the width for the wires, showing the success of the monolayer patterning process to nanoscale. To fabricate atomic wires made of one or a few lines of phosphorus atoms, we need to significantly shorten the thermal diffusion length and increase the dopant incorporation rate at the same time. Pulsed laser annealing may be a promising solution. The present work provides a promising pathway for mass fabrication of atomic wires in silicon that may find important applications in quantum computing.
关键词： atomic wires,semiconductors,nanoelectronics,Monolayer doping,self-assembled monolayers
更新于2025-09-12 10:27:22
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Influence of MBE growth parameters on GaSb/GaAs quantum dot morphology
摘要： In this paper, growth of self-assembled type-II GaSb/GaAs quantum dots by molecular beam epitaxy technique is presented. The effect of various growth parameters such as substrate temperature, Sb/Ga beam equivalent pressure ratio, growth rate and total mono-layer coverage on surface morphology is analyzed. The GaSb quantum dots exhibit high anisotropy along <110> and <1-10> directions under specific growth conditions. The anisotropy is discussed on the basis of incorporation of background Arsenic and anisotropic diffusion of Gallium adatoms on the GaSb surface. The low temperature photoluminescence measurements in GaAs capped samples show recombination in the type-II quantum dots and the wetting layer.
关键词： Self assembled process,Anisotropy,Molecular beam epitaxy,Type-II quantum dots,Stranski-Krastanov growth
更新于2025-09-12 10:27:22
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Self-assembled naphthalimide derivatives as an efficient and low-cost electron extraction layer for n-i-p perovskite solar cells
摘要： Based on self-assembly, novel electron extraction layers (EELs) composed of naphthalimide (NPI) derivatives are constructed for application in n-i-p perovskite solar cells. Upon molecular energy level modulation, the power conversion efficiencies have been largely improved from 5.4% to 16%. Such low-cost and highly regulable EELs are promising for future commercial applications.
关键词： electron extraction layer,molecular energy level modulation,perovskite solar cells,Self-assembled naphthalimide derivatives
更新于2025-09-12 10:27:22
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A biomimetic self-assembled cobaloxime@CdS/rGO hybrid for boosting photocatalytic H <sub/>2</sub> production
摘要： A biomimetic CoPe@CdS/rGO hybrid that self-assembles via the integration of a molecular cobalt catalyst and CdS nano-semiconductor on reduced graphene oxide was constructed for boosting photocatalytic H2 production. Photoinduced electron transfer from CdS/rGO to the molecular catalyst occurs and a long-lived charge-separation state forms for high H2 production.
关键词： self-assembled,cobaloxime,CdS/rGO,photocatalytic H2 production,biomimetic
更新于2025-09-12 10:27:22
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Combined SERS/DFT studies of push–pull chromophore self-assembled monolayers: insights into their surface orientation
摘要： Having clear and deep information on the surface/interface of deposited molecules is of crucial importance for the development of efficient optoelectronic devices. This paper reports on a joint experimental/theoretical hybrid approach based on Raman spectroscopy in order to provide information on the orientation of push–pull chromophores deposited onto a gold surface. In addition, several parameters can strongly control or impede the orientation of such molecules on the surface such as: the molecular structure, the surface itself, the method of deposition and the solvents used. From this approach, additional information has been highlighted such as perpendicularly depositing the molecule on the surface, the bithiophene compounds displaying more solvent effects compared to terthiophene molecules and so on. According to the results, the joint SERS/DFT study proves to be an effective tool for probing the arrangement of push–pull chromophores and selecting the right experimental conditions to tune the surface properties.
关键词： SERS,DFT,push–pull chromophores,surface orientation,self-assembled monolayers
更新于2025-09-12 10:27:22
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Dimethylaniline functionalised pyrene fluorophores; dual colour pH switching in solution and self-assembled monolayers
摘要： A pyrene charge transfer fluorophore with three ionizable N,N-dimethylaniline moieties was explored as an interfacial pH switch. The parent carboxylate compound and the thiolated derivative were shown by spectroscopy combined with DFT calculation to be successively and reversibly protonated. Protonation leads to progressive decrease of intensity of the 550 nm centered N,N-dimethylaniline to pyrene charge transfer emission which on protonation of the third site, leads to extinction of this transition and evolution of an intense blue (450 nm) pyrene-centered emission. Concomitant loss of the charge transfer absorbance was observed and the changes are reversed on neutralization of pH. A self-assembled monolayer of the thiolated derivative was prepared on gold and found from voltammetry of ferricyanide/ferrocyanide probe to form close packed monolayers. The probe voltammetry, label-free electrochemical impedance spectroscopy of the film was monitored as a function of pH and progressive, but reversible protonation steps were reflected in decreasing film resistance. The Stokes shift of the probe prevents self-quenching so a broad, charge transfer fluorescence centered around 540 nm was recorded for the self-assembled monolayer where as per solution, progressive and reversible reduction in intensity was observed. The facile assembly, impedance and optical switching make these materials potentially interesting as on–off or two colour on–off–on fluorescence switches with potential applications in logic gates or in responsive surface applications.
关键词： DFT calculation,self-assembled monolayer,fluorescence,charge transfer,pH switch,pyrene
更新于2025-09-12 10:27:22