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Effects of Strategically Placed Water Droplets on Monolayer Growth of Molybdenum Disulfide
摘要： Two-dimensional (2D) molybdenum disulfide (MoS2) films with a tunable bandgap hold great promise for next-generation electronic and optoelectronic devices. Synthesis of large areas of high-quality MoS2 monolayers lacks experimental reproducibility. Moreover, the outcome of MoS2 growth by chemical vapor deposition is dependent on several interconnected growth parameters. In this study, we present results of MoS2 monolayer growth by strategically placing water droplets on the growth substrate and/or in the source prior to its loading in the growth chamber. The volume and distribution of water on the growth substrate and in the source had a direct impact on the morphology of the as-grown MoS2. Characterized by scanning electron microscopy (SEM), Raman microscopy, and atomic force microscopy (AFM), the number and size of MoS2 layers as well as its distribution on the growth substrate were found to have a strong dependence on the positioning of the water droplet. This study on MoS2 monolayer growth using water droplets as a promoter provides a simple and reproducible experimental technique enabling growth with high reliability.
关键词： molybdenum disulfide,water droplets,Raman microscopy,scanning electron microscopy,chemical vapor deposition,atomic force microscopy,monolayer growth
更新于2025-09-09 09:28:46
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Noninvasive diagnostic imaging using machine-learning analysis of nanoresolution images of cell surfaces: Detection of bladder cancer
摘要： We report an approach in diagnostic imaging based on nanoscale-resolution scanning of surfaces of cells collected from body fluids using a recent modality of atomic force microscopy (AFM), subresonance tapping, and machine-leaning analysis. The surface parameters, which are typically used in engineering to describe surfaces, are used to classify cells. The method is applied to the detection of bladder cancer, which is one of the most common human malignancies and the most expensive cancer to treat. The frequent visual examinations of bladder (cytoscopy) required for follow-up are not only uncomfortable for the patient but a serious cost for the health care system. Our method addresses an unmet need in noninvasive and accurate detection of bladder cancer, which may eliminate unnecessary and expensive cystoscopies. The method, which evaluates cells collected from urine, shows 94% diagnostic accuracy when examining five cells per patient’s urine sample. It is a statistically significant improvement (P < 0.05) in diagnostic accuracy compared with the currently used clinical standard, cystoscopy, as verified on 43 control and 25 bladder cancer patients.
关键词： diagnostic imaging,cancer diagnostics,atomic force microscopy,machine learning,noninvasive methods
更新于2025-09-09 09:28:46
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Investigations of properties of opal-like photonic crystals using combined methods
摘要： We propose a technique that combines atomic force microscopy, optical spectrophotometry and di?raction method for characterization of photonic crystals. These materials are promising for the creation of various devices, as well as for the observation of new e?ects due to their unique properties. Photonic crystals were synthesized by self-assembly of colloidal silica particles with low deviation in size. It is shown that the developed technique allows to increase the accuracy of determining the parameters of the photonic crystal.
关键词： diffraction method,photonic crystals,self-assembly,colloidal silica particles,atomic force microscopy,optical spectrophotometry
更新于2025-09-09 09:28:46
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Changing Times: Fluorescence-Lifetime Analysis of Amyloidogenic SF-IAPP Fusion Protein
摘要： In a number of conformational diseases, intracellular accumulation of proteins bearing non-native conformations occurs. The search for compounds that are capable of hindering the formation and accumulation of toxic protein aggregates and fibrils is an urgent task. Present fluorescent methods of fibrils’ detection prevent simple real-time observations. We suppose to use green fluorescent protein fused with target protein and fluorescence lifetime measurement technique for this purpose. The recombinant proteins analyzed were produced in E. coli. Mass spectrometry was used for the primary structure of the recombinant proteins and post-translational modifications identification. The fluorescence lifetime of the superfolder green fluorescent protein (SF) and the SF protein fused with islet amyloid polypeptide (SF-IAPP) were studied in polyacrylamide gel using Fluorescent-Lifetime Imaging Microscopy (FLIM). It was shown that the SF average fluorescence lifetime in gel slightly differs from that of the SF-IAPP monomer under these conditions. SF-IAPP does not lose the ability to form amyloid-like fibrils. Under the same conditions (in polyacrylamide gel), SF and SF-IAPP monomers have similar fluorescence time characteristics and the average fluorescence lifetime of SF-IAPP in fibrils significantly decreases. We propose the application of FLIM to the measurement of average fluorescence lifetimes of fusion proteins (amyloidogenic protein-SF) in the context of studies using cellular models of conformational diseases.
关键词： FLIM,IAPP,amyloid-like fibrils,green fluorescent protein,atomic force microscopy,conformational diseases
更新于2025-09-09 09:28:46
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Unlocking higher harmonics in atomic force microscopy with gentle interactions
摘要： In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.
关键词： composition,phase,heterogeneity,chemistry,higher harmonics,atomic force microscopy
更新于2025-09-09 09:28:46
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Nucleation of diindenoperylene and pentacene at thermal and hyperthermal incident kinetic energies
摘要： The authors have examined the nucleation of diindenoperylene (DIP) on SiO2 employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (Ei ? 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the maximum island density on the growth rate is described by a power law. A critical nucleus of approximately two molecules is implicated by our data. A re-examination of the nucleation of pentacene on SiO2 gives the same major result that the maximum island density is determined by the growth rate, and it is independent of the incident kinetic energy. These observations are readily understood by factoring in the size of the critical nucleus in each case, and the island density, which indicates that diffusive transport of molecules to the growing islands dominate the dynamics of growth in the submonolayer regime.
关键词： thermal,SiO2,supersonic sources,diindenoperylene,hyperthermal,kinetic energies,nucleation,atomic force microscopy,pentacene
更新于2025-09-09 09:28:46
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Effects of N2 and NH3 plasma exposure on the surface topography of p-GaN under quasi-atmospheric pressure
摘要： We used atomic force microscopy to characterize the surface topography of p-GaN exposed to N2 and NH3 plasma under quasi-atmospheric pressure using a microwave-excited plasma source with a microstrip line structure. The exposure time was varied from 2 to 20 min at a substrate temperature of 700 °C. Under both N2 and NH3 plasma exposure for 2 min, the ridge-shaped features on the surface of as-grown p-GaN dulled immediately and the surface roughness decreased remarkably, whereas the atomic step structure of the surface was maintained. The step crossing and bunching of the surface disappeared with increasing exposure time to both types of plasma. However, increasing the NH3 plasma exposure time to 20 min led to the formation of pits and appearance of particles along the step edges, resulting in drastic roughening of the surface. Thus, GaN surfaces can be smoothed without the destruction of their step structures via moderate plasma exposure under quasi-atmospheric pressure, and these plasma sources could prospectively be used in metal-organic chemical vapor deposition systems for nitride semiconductor growth.
关键词： microwave-assisted plasma,surface topography,N2 and NH3 plasma,atomic force microscopy,metal organic chemical vapor deposition,GaN
更新于2025-09-09 09:28:46
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Metal-insulator transition in V <sub/>2</sub> O <sub/>3</sub> thin film caused by tip-induced strain
摘要： We have demonstrated pressure-induced transition in a c-axis oriented vanadium sesquioxide (V2O3) thin film from a strongly correlated metal to a Mott insulator in a submicrometric region by inducing a local stress using contact atomic force microscopy. To have an access to a pressure range of sub-gigapascal, a tip with a large radius of 335 nm was prepared by chemical vapour deposition of platinum onto a commercial tip with a focused ion beam (FIB). The FIB-modified tip gives a good electrical contact at low working pressures (0.25–0.4 GPa) allowing unambiguously to evidence reversible metal-insulator transition in a pulsed laser-deposited V2O3 thin film by means of local investigations of current-voltage characteristics. A finite element method has confirmed that the diminution of the c/a ratio under this tip pressure explains the observed phase transition of the electron density of states in the film.
关键词： tip-induced strain,Mott insulator,metal-insulator transition,V2O3 thin film,atomic force microscopy
更新于2025-09-09 09:28:46
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Nonlinear Optical Properties of Oxide Thin Films
摘要： This work contains description of the oxide thin films fabricated by Physical Vapor Deposition technique in high vacuum on transparent (quartz) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. Titanium, tin and indium oxides were chosen as the material for investigation. Selected films were annealed after fabrication in ambient atmosphere for 12 hours at the temperature equal to 100 °C, 150 °C, 250 °C and 450 °C. Structural properties were examined by optical images and AFM measurements. The films exhibit high structural dependence on the temperature of the annealing process. Quality of the films can be improved by using an appropriate temperature during the annealing process. Nonlinear optical effects were studied using Third Harmonic Generation with Nd:YAG laser at 1064 nm wavelength as a fundamental beam. The values of third-order NLO susceptibilities were calculated and analyzed. We find that the nonlinear optical properties were strictly connected with the morphology. Moreover the temperature of annealing process can change the structural and optical properties of the tested oxide thin films.
关键词： third harmonic generation,atomic force microscopy,oxide thin films,physical vapor deposition
更新于2025-09-09 09:28:46
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Customized MFM probes with high lateral resolution
摘要： Magnetic force microscopy (MFM) is a widely used technique for magnetic imaging. Besides its advantages such as the high spatial resolution and the easy use in the characterization of relevant applied materials, the main handicaps of the technique are the lack of control over the tip stray field and poor lateral resolution when working under standard conditions. In this work, we present a convenient route to prepare high-performance MFM probes with sub-10 nm (sub-25 nm) topographic (magnetic) lateral resolution by following an easy and quick low-cost approach. This allows one to not only customize the tip stray field, avoiding tip-induced changes in the sample magnetization, but also to optimize MFM imaging in vacuum (or liquid media) by choosing tips mounted on hard (or soft) cantilevers, a technology that is currently not available on the market.
关键词： magnetic materials,AFM probes,high-resolution microscopy,atomic force microscopy (AFM),magnetic force microscopy (MFM)
更新于2025-09-04 15:30:14