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- 实验方案
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Manipulating and probing the distribution of excess electrons in an electrically-isolated self-assembled molecular structure
摘要： Exploiting single electrical charges and their mutual interactions for computation has been proposed as a concept for future nanoelectronics. Controlling and probing charge transfer in electrically isolated atomic-scale structures are fundamental to push its experimental realization. Here, we controllably inject individual excess electrons and study their distribution in a self-assembled structure supported on a non-conductive substrate. The self-assembly ensures structural order down to the atomic scale. Depending on the charge state of the molecular assembly, intermolecular electron hopping and specific electron distributions have been resolved by atomic force microscopy, clarifying the charge-transfer pathways in the tunnel-coupled structure. Exploiting the mutual charge interactions, control over specific charge distributions in the self-assembled structure has been achieved with single-molecule precision, paving the way towards the design of data processing platforms based on molecular nanostructures.
关键词： self-assembly,atomic force microscopy,dissipation,single electron charging
更新于2025-09-23 15:19:57
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Development of All-Diamond Scanning Probes Based on Faraday Cage Angled Etching Techniques
摘要： We are proposing a novel fabrication method for single crystal diamond scanning probes for atomic force microscopy (AFM), exploiting Faraday cage angled etching (FCAE). Common, oxygen-based, inductively coupled plasma (ICP) dry etching processes for diamond are limited with respect to the achievable geometries. The fabrication of freestanding micro- and nanostructures is therefore challenging. This is a major disadvantage for several application fields e.g., for realizing scanning magnetometry probes based on nitrogen vacancy (NV) centres and capable of measuring magnetic fields at the nanoscale. Combining a planar design with FCAE and state-of-the-art electron beam lithography (EBL) yields a reduction of process complexity and cost compared to the established fabrication technology of micro-opto-mechanical diamond devices. Here, we report on the direct comparison of both approaches and present first proof-of-concept planar-FCAE-prototypes for scanning probe applications.
关键词： Faraday cage angled etching,scanning magnetometry,atomic force microscopy,diamond scanning probes,nitrogen vacancy centres
更新于2025-09-23 15:19:57
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Digital holography for non-invasive quantitative imaging of two-dimensional materials
摘要： Digital holography has found applications in many walks of life, from medicine to metrology, due to its ability to measure complex fields. Here, we use the power of digital holography to quantitatively image two-dimensional Transition Metal Dichalcogenides (TMDs) such as MoS2 and WS2 placed on a SiO2/Si substrate and determine their complex refractive indices or layer thicknesses. By considering the different refractive indices of the TMDs as they are thinned down from bulk to monolayers and by holographically capturing both the amplitude and the phase of reflected light, single atomic layers of TMDs, about 0.7 nm thick, can be resolved. Using holography, we also predict the number of layers contained within a thick TMD flake, which shows agreement with results obtained using Atomic Force Microscopy (AFM). A Bland–Altman analysis was performed to compare our experimental results with the standard AFM measurements, yielding a limit of agreement <5 nm for samples with thicknesses ranging from 15 to 60 nm. Our technique is non-contact, non-invasive, does not require scanning, and produces a field of view of a few hundred micrometers by a few hundred micrometers in a single capture. To further our study, we also perform simulations to demonstrate how the thickness of the SiO2 layer and the laser wavelength are critical in optimizing the amplitude and phase response of a two-dimensional material. These simulations can be used as a roadmap to determine the ideal wavelength and SiO2 layer thickness that should be used to accurately determine the refractive index or thickness of any given sample.
关键词： digital holography,Atomic Force Microscopy,layer thicknesses,Bland–Altman analysis,Transition Metal Dichalcogenides,two-dimensional materials,complex refractive indices
更新于2025-09-23 15:19:57
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Nanostructures of functionalized zinc phthalocyanines prepared with colloidal lithography: Evaluation of surface orientation and dimensions using scanning probe microscopy
摘要： Patterned arrays of nanoholes and nanorings were prepared using colloidal lithography combined with steps of solution immersion and vapor deposition of organosilanes. Samples prepared with colloidal lithography exhibit millions of reproducible test structures with a periodic arrangement throughout areas of the surface according to the dimensions and spacing of the particle mask. Views of the size and morphology of nanopatterns obtained with atomic force microscopy (AFM) can provide information of progressive steps of chemical reactions as nanostructures are grown within spatially confined areas surrounded by a resist film. A surface mask of colloidal latex or silica spheres was used to protect discrete areas of a Si(111) substrate from the deposition of organosilanes. When the mask was removed, the uncovered areas of the surface revealed regularly-shaped, small sites of uncovered substrate available for further reaction steps to build hierarchical surface structures. Nanostructures of zinc phthalocyanines (ZnPcs) were constructed using amine-terminated nanopatterns as sites for binding. Spatial selectivity was achieved for directing the attachment of ZnPcs to the surface using resist films of 2-[methoxy(polyethyleneoxy)propyl]trichlorosilane (PEO-silane) and also with octadecyltrimethoxysilane (OTMS). The molecule chosen as a linker was (3-aminopropyl)triethoxysilane (APTES) which presents an amine group at the interface. In general, phthalocyanine molecules tend to bind in a coplanar orientation by physisorption to the surface and can stack together through pi-pi interactions between adjacent macrocycles. However, the nature of the substituents will also influence whether the molecules assemble on surfaces in a side-on orientation or with the macrocycle oriented in a coplanar arrangement. Hydroxyl and isothiocyanate pendant groups were attached to the macrocycles of ZnPcs chosen for this study, to investigate conformational differences when attached to APTES nanopatterns. The size and morphology of nanostructures was visualized and sensitively measured with tapping-mode AFM. The elastic response of samples patterned with ZnPc was mapped with force modulation AFM. Changes in the height of nanostructures indicate whether the macrocycles are oriented upright or parallel to the surface plane, or if multilayers were formed.
关键词： Atomic force microscopy,Colloidal lithography,Nanopatterning,Phthalocyanines
更新于2025-09-23 15:19:57
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Variations of the elastic modulus perpendicular to the surface of rubrene bilayer films
摘要： Investigations exploring the inherent mechanical properties of electronic materials have grown rapidly in recent years largely because they are important in developing flexible electronics, organic displays and sensors. However, our understanding of the mechanical properties of organic semiconductors with a thin-film form remains limited. We report herein on an investigation of the structures and related elastic moduli perpendicular to the surface of a rubrene thin film. A rubrene/Si(100) film typically has a cluster-type morphology mainly comprised of crystalline nanodomains within the film. We propose a structural bilayer model that can be used to explain the layered nature or characteristics of the rubrene films. As the film thickness is increased, the enhancement in elastic modulus can be attributed to the presence of a soft surface layer on a hard underlayer. Based on four-point probe measurements, the bilayered nature of such materials can be used to characterize their electrical resistive behavior while interfacial roughness is sensitive to the transport paths of conduction electrons. This information is valuable for future applications of organic semiconductors in flexible devices.
关键词： four-probe measurement,atomic force microscopy,rubrene,stress
更新于2025-09-19 17:15:36
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Elastic Properties of Suspended Conducting GaAs/AlGaAs Nanostructures by Means of Atomic Force Microscopy
摘要： This paper demonstrates the applicability of nanoindentation technique using atomic-force microscope cantilever for studying the elastic properties of suspended semiconductor structures on the basis of relatively thick GaAs/AlGaAs membranes in the case when their stiffness significantly exceeds that of the cantilever of atomic-force microscope, which is confirmed by the agreement between the experimentally determined values of both relative and absolute stiffness measured at different points of the investigated structure with theoretical predictions.
关键词： nanoelectromechanical systems,GaAs/AlGaAs,atomic-force microscopy,suspended nanostructures
更新于2025-09-19 17:15:36
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Simultaneous photoreduction and Raman spectroscopy of red blood cells to investigate the effects of organophosphate exposure
摘要： Simultaneous photoreduction and Raman spectroscopy with 532 nm laser has been used to study the effects of organophosphate (chlorpyrifos) exposure on human red blood cells. Since in red blood cells, auto-oxidation causes oxidative stress, which, in turn, is balanced by the cellular detoxicants, any possible negative effect of chlorpyrifos on this balance should results in an increased level of damaged (permanently oxygenated) hemoglobin. Therefore, when 532 nm laser, at a suitable power, was applied to photoreduce the cells, only common oxygenated form of hemoglobin got photoreduced leaving the permanently oxygenated hemoglobin detectable in the Raman spectra simultaneously excited by the same laser. Using the technique effects of chlorpyrifos to build up oxidative stress on red blood cells could be detected at concentrations as low as 10 ppb from a comparison of relative strengths of different Raman bands. Experiments performed using simultaneously exposing the cells, along with chlorpyrifos, to H2O2 (oxidative agent) and/or 3-Aminotriazole (inhibitor of anti-oxidant catalase), suggested role of chlorpyrifos to suppress the cellular anti-oxidant mechanism. Since the high level of damaged hemoglobin produced by the action of chlorpyrifos (at concentrations > 100 ppm) is expected to cause membrane damage, atomic force microscopy was used to identify such damages.
关键词： atomic force microscopy,Photoreduction,optical trap,Raman spectroscopy,red blood cells,chlorpyrifos
更新于2025-09-19 17:15:36
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The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on <i>Poly</i> -Si/SiO <i> <sub/>x</sub></i> Contacts for Silicon Solar Cells
摘要： High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured surface to reduce carrier recombination is difficult. Here, we relate the electrical properties of cells fabricated on a KOH-etched, random pyramidal textured Si surface to the nanostructure of the passivated contact and the textured surface morphology. The effects of both microscopic pyramidal morphology and nanoscale surface roughness on passivated contacts consisting of a polycrystalline Si (poly-Si) deposited on top of an ultrathin, 1.5–2.2 nm, SiOx layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) plane to be significantly rougher than a polished Si(111) surface. This roughness results in a nonuniform SiOx layer as determined by transmission electron microscopy (TEM) of a poly-Si/SiOx contact. Our device measurements also show an overall more resistive, and hence thicker SiOx layer over the pyramidal surface as compared to a polished Si(111) surface, which we relate to increased roughness. Using electron-beam-induced current measurements of poly-Si/SiOx contacts we further show that the SiOx layer near the pyramid valleys is preferentially more conducting, and hence likely thinner than over pyramid tips, edges and faces. Hence, both the microscopic pyramidal morphology and nanoscale roughness lead to nonuniform SiOx layer, thus leading to poor poly-Si/SiOx contact passivation. Finally, we report >21% efficient and ≥80% fill-factor front/back poly-Si/SiOx solar cells on both single-side and double-side textured wafers without the use of transparent conductive oxide layers and show that the poorer contact passivation on a textured surface is limited to boron-doped poly-Si/SiOx contacts.
关键词： passivated contact,tunneling,silicon oxide,electron beam induced current,silicon solar cell,surface orientation,atomic force microscopy
更新于2025-09-19 17:13:59
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Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells
摘要： Metal halide perovskite materials, benefiting from a combination of outstanding optoelectronic properties and low-cost solution-preparation processes, show tremendous potential for optoelectronics and photovoltaics. However, the nanoscale inhomogeneities of the electronic properties of perovskite materials cause a number of difficulties, such as recombination, stability, and hysteresis, all of which seriously restrict device performance. Scanning probe microscopy, as a high-resolution imaging technique, has been widely used to connect local properties and micro-area morphologies to overall device performance. Conductive atomic force microscopy (C-AFM) can realize a real-space visualization of topography coupled with optoelectronic properties on a microscopic scale and thereby is uniquely suited to probe the local effects of perovskite materials and devices. The fundamental principles, alternative operation modes, and development of C-AFM are comprehensively reviewed, and applications in perovskite solar cells (PSCs) for electronic transport behavior, ion migration and hysteresis, ferroelectric polarization, and facet orientation investigation are discussed. A comprehensive understanding and summary of up-to-date applications in PSCs is beneficial to further fully exploit the potential of such an emerging technique, so as to provide a novel and effective approach for perovskite materials analysis.
关键词： ferroelectricity,perovskite solar cells,conductive atomic force microscopy,ion migration,perovskite materials,electronic transport behavior
更新于2025-09-19 17:13:59
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Epitaxial Fe3O4 Films Grown on R-Plane Sapphire by Pulsed Laser Deposition
摘要： We have studied the influence of growth temperature and molecular oxygen pressure on the properties of thin (≤180 nm) epitaxial magnetite (Fe3O4) (001) films grown by pulsed laser deposition on R-plane single-crystal sapphire (Al2O3 ( 012)) with and without MgO seed layer. The electrical, morphological, and structural characteristics of the films have been investigated as functions of growth conditions. Fe3O4 has been shown to have a stable growth plateau at pressures in the range (4–9) × 10–5 Torr. The properties of the epitaxial Fe3O4 films grown on a MgO seed layer (5 nm thick) approach those of magnetite films grown on single-crystal MgO substrates and are superior to those of films grown on pure R-plane sapphire. The best electrical characteristic of the films and the corresponding crystal structure can be obtained at elevated growth temperatures, whereas reduced growth temperatures minimize the roughness of their surface and maximize its homogeneity. These conditions can be reconciled by high-temperature high-vacuum annealing of magnetite films grown at reduced temperatures.
关键词： epitaxial growth,atomic force microscopy,magnetite,thin films
更新于2025-09-19 17:13:59