Search results for "Force microscopy"

Switching direction of laterally ordered monolayers induced by transfer instability

2007

Langmuir-Blodgett monolayers may show nanoscopic periodic patterns parallel and/or perpendicular to the transfer direction. The experimental findings are interpreted by a nonequilibrium model based on the stability of surfactant concentration and film thickness coupled fluctuations near the meniscus of a surfactant-covered receding thin film. In the high and low transfer speed limits, periodic fluctuations of the fluid subphase thickness, respectively perpendicular and parallel to the transfer, are selected. A qualitative phase diagram shows how transfer speed and film density manage the pattern shape.

Aluminum oxide nucleation in the early stages of atomic layer deposition on epitaxial graphene

2020

In this work, the nucleation and growth mechanism of aluminum oxide (Al2O3) in the early stages of the direct atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H-SiC) has been investigated by atomic force microscopy (AFM) and Raman spectroscopy. Contrary to what is typically observed for other types of graphene, a large and uniform density of nucleation sites was observed in the case of EG and ascribed to the presence of the buffer layer at EG/SiC interface. The deposition process was characterized by Al2O3 island growth in the very early stages, followed by the formation of a continuous Al2O3 film (2.4 nm thick) after only 40 ALD cycles due to the isla…

Membrane Stiffness of Animal Cells Challenged by Osmotic Stress

2006

Synthesis of multi-color luminescent ZnO nanoparticles by ultra-short pulsed laser ablation

2020

Abstract Crystalline ZnO nanoparticles (NPs) are synthesized by ultra-short femtosecond (fs) pulsed laser ablation (PLA) of a zinc plate in deionized water, and are investigated by optical absorption and time resolved luminescence spectra in combination with the morphology and structure analysis. The comparison with previous experiments based on short nanosecond (ns) PLA highlights that pulse duration is a crucial parameter to determine the size and the optical properties of ZnO NPs. While short PLA generates NPs with average size S ‾ of ~ 30 nm, ultrashort PLA allows to achieve much smaller NPs, S ‾ ⩽ 10  nm, that evidence weak quantum confinement effects on both the absorption edge and th…

Second-harmonic Generation Microscopy of Carbon Nanotubes

2012

We image an individual single-walled carbon nanotube (SWNT) by second-harmonic generation (SHG) and transmission electron microscopy and propose that SHG microscopy could be used to probe the handedness of chiral SWNTs.

Atomic Force Microscopy and Spectroscopy

2021

Atomic force microscopy (AFM) is probably the most celebrated technique falling into the family of experimental methods known as scanning probe microscopy. AFM is primarily designed to obtain the morphology of the surface of a solid material by using the force of interaction between an inert probe and the sample. The AFM microscope can generally be operated in many ways for morphology investigations, but they can be roughly classified into two main groups: static- and dynamic-deflection modes. Since atomic force microscopy makes use of tip-surface interaction to reconstruct the surface morphology of materials, it is of fundamental importance to fully understand the nature and properties of …

Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water

2014

Abstract We report the investigation of luminescent nanoparticles produced by ns pulsed Nd:YAG laser ablation of silicon in water. Combined characterization by AFM and IR techniques proves that these nanoparticles have a mean size of ∼3 nm and a core–shell structure consisting of a Si-nanocrystal surrounded by an oxide layer. Time resolved luminescence spectra evidence visible and UV emissions; a band around 1.9 eV originates from Si-nanocrystals, while two bands centered at 2.7 eV and 4.4 eV are associated with oxygen deficient centers in the SiO 2 shell.

High-Density Arrays of Germanium Nanowire Photoresistors

2006

Here we present for the first time a study of the photoresistive properties and dynamics of ordered, high-density arrays of germanium nanowire photoresistors. Germanium is a wellknown semiconducting material with an indirect bandgap, Eg, of approximately 0.66 eV (temperature T = 300 K) and has been widely used for the fabrication of photodetectors, radiation detectors, charged particle and photon tracking devices, far-infrared photoresistors, and numerous other devices. During the last few years there has also been increasing interest in the use of nanostructures (quantum dots and wires) of both germanium and silicon as materials for potential applications in sensors, nanophotonics, and nan…

Microscopic observation of unworn siloxane-hydrogel soft contact lenses by atomic force microscopy

2006

In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 m2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 m2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; …

Mechanical recycling of polylactide, upgrading trends and combination of valorization techniques

2016

[EN] The upcoming introduction of polylactides in the fractions of polymer waste encourages technologists to ascertain its valorization at the best quality conditions. Mechanical recycling of PLA represents one of the most cost-effective methodologies, but the recycled materials are usually directed to downgraded applications, due to the inherent thermomechanical degradation affecting its mechanical, thermal and rheological performance. In this review, the current state of mechanical recycling of PLA is reported, with special emphasis on a multi-scale comparison among different studies. Additionally, the applications of physical and chemical upgrading strategies, as well as the chances to b…