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Critical factors in quantitative Atomic Force Acoustic Microscopy
No full textAtomic Force Acoustic Microscopy (AFAM) is a scanning probe technique for advanced research in nanomechanical properties, using local elasticity to provide direct and non-destructive mapping of Young's modulus and related surface parameters.In this work, an experimental study is presented, addressing the performance of quantitative AFAM characterization. Different influencing factors are analysed, mainly arising from probe characteristics (such as cantilever geometry, force constant and ultimately resonance frequency) and scan settings (speed and sample vibration frequency). Investigations encompassed a commercial instrument equipped with three different probes, featuring different dimensions and mechanical properties
Thermal drift study on different commercial scanning probe microscopes during the initial warming-up phase
No full textScanning probe microscopy (SPM) allows surface topography imaging with the highest resolution, as a result of accurate actuation combined with the sharpness of tips. The scanning process is inherently slow and commonly suffers from instrumental drift. Drift evaluation and control is an important issue for quantitative metrology. Drift characterization is essential in order to establish an appropriate method for eliminating, compensating or correcting it, allowing the improvement of measurement quality and accuracy. Drift distortions are often regarded as temperature-dependent phenomena, associated with temperature gradients and transients that may occur both in the single components of the equipment and in the measuring volume. Commercial SPMs are designed and manufactured with different approaches, e. g. combining different scanners' architectures, with selected hardware, software and materials, in order to optimize specific instrument performances such as accuracy and scanning speed. Hence, different SPMs on the market have different drift depending on instrument design and materials. In this work, a set of experiments was conducted on different instruments operating under varying controlled environmental conditions, for drift estimation, with particular reference to the initial warming-up phase. The experimental procedure for drift evaluation was based on repeated measurements on a structured reference grating. Temperature was monitored using an infrared camera. Six different SPMs were compared based on the analysis of the evolution of horizontal and vertical drift over time, allowing correlation of the drift trend with instrument architecture
Critical factors in cantilever Near-Field Scanning Optical Microscopy
Full text linkAn important technique for high resolution optical imaging, beyond the diffraction limit, of nanostructured surfaces is aperture Near-field Scanning Optical Microscopy (NSOM). Even though NSOM has already demonstrated its good performance in a number of different applications, its quantitative application is still a challenge, due to a number of factors which commonly influence the quality of the measurement output and consequently extrapolation of quantitative parameters. In the present paper a systematic study is reported, analysing the effect of the most critical factors in cantilever NSOM measurements, with particular attention to tip geometry and aperture, scanning configuration and scan mode. Investigations have been carried out on a commercial instrument, in combination with reference standard for NSOM calibration (as for instance the Fisher pattern) and other samples opportunely produced for the present wor
A new combined process based on MWCNT spray deposition and atmospheric pressure plasma jet fixing for large scale production of transparent and flexible conductive coatings
No full textLuminescent dye-doped or rare-earth-doped monodisperse silica nanospheres as efficient labels in DNA microarrays
No full textLuminescent nanoparticles are gaining more and more interest in bio-labeling and bio-imaging applications, like for example DNA microarray. This is a high-throughput technology used for detection and quantification of nucleic acid molecules and other ones of biological interest. The analysis is resulting by specific hybridization between probe sequences deposited in array and a target ss-DNA usually expressed by PCR and functionalized by a fluorescent dye. These organic labels have well known disadvantages like photobleaching and limited sensitivity. Quantum dots may be used as alternatives, but they present troubles like blinking, toxicity and excitation wavelengths out of the usual range of commercial instruments, lowering their efficiency. Therefore in this work we investigate a different strategy, based on the use of inorganic silica nanospheres incorporating standard luminescent dyes or rare earth doped nanocrystals. In the first case it is possible to obtain a high luminescence emission signal, due to the high number of dye molecules that can be accommodated into each nanoparticle, reduced photobleaching and environmental protection of the dye molecules thanks to the encapsulation in the silica matrix. In the second case, rare earths exhibit narrow emission bands (easy identification), large Stokes shifts (efficient discrimination of excitation and emission) and long luminescence lifetimes (possibility to perform time-delayed analysis) which can be efficiently used for the improvement of signal to noise ratio. The synthesis and characterization of good luminescent silica spheres either by organic dye-doping or by rare-earth-doping are investigated and reported. Moreover, their application in the DNA microarray technology in comparison to the use of standard molecular fluorophores or commercial quantum dots is discussed. The cheap and easy synthesis of these luminescent particles, the stability in water, the surface functionalization and bio-compatibility makes them very promising for present and future applications in bio-labeling and bio-imaging
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