- My research activity concerns various aspects of nanoscience.Phenomena in surface and interface physics are explored ... moreMy research activity concerns various aspects of nanoscience.Phenomena in surface and interface physics are explored at nanometer-scale resolution by local probe microscopy and spectroscopy techniques, with strong emphasis to local surface dissipation effects. Main employed techniques are atomic force microscopy and electrostatic force microscopy.edit
A simple experimental method for piezoresponse force microscopy (PFM) measurements for reliable evaluation of piezoelectric surface displacements even on compliant surfaces is proposed based on atomic force microscopy (AFM) operated in... more
A simple experimental method for piezoresponse force microscopy (PFM) measurements for reliable evaluation of piezoelectric surface displacements even on compliant surfaces is proposed based on atomic force microscopy (AFM) operated in frequency-modulation (FM) dynamic mode with constant excitation (CE), by using non-contact mode cantilevers. Surface displacement by piezoelectric effect after application of an electric potential to the conductive AFM probe translates into a likewise variation of the probe oscillation amplitude, while the related electrostatic forces mainly affect the oscillator resonant frequency, and cantilever bending is limited due to their high stiffness. Our non-contact CE-FM-PFM method is shown to reduce electrostatic force contributions as compared to contact-PFM modes. Converse piezoelectric effect mapping is demonstrated on poly(vinylidenefluoride) (PVDF) nanofibers obtained by electrospinning.
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We demonstrate apertureless near-field optical imaging with material contrast on metal nanostructures, by local second-harmonic generation at a metal tip properly illuminated at grazing incidence by femtosecond pulses.
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ABSTRACT The influence on relaxation dynamics of poly(vinyl acetate) of SiOx nanoparticles dispersed in the polymeric matrix was investigated by Local Dielectric Spectroscopy, measuring the phase loss angle in the polymer as a function of... more
ABSTRACT The influence on relaxation dynamics of poly(vinyl acetate) of SiOx nanoparticles dispersed in the polymeric matrix was investigated by Local Dielectric Spectroscopy, measuring the phase loss angle in the polymer as a function of the distance from the nanoparticles. Both images of phase loss angle and acquisition of local dielectric spectra show two distinct features, namely, a faster relaxation dynamics when approaching the nanoparticle surface, and a rather large range of influence on polymer dynamics with respect to nanoparticle size, probe size, and gyration radius of the polymer.
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A quadrature optical detection technique, based on polarized balanced-homodyne interferometry, has been developed for specific application to apertureless near-field scanning optical microscopy (ANSOM). With such technique, multiplicative... more
A quadrature optical detection technique, based on polarized balanced-homodyne interferometry, has been developed for specific application to apertureless near-field scanning optical microscopy (ANSOM). With such technique, multiplicative background interference, inficiating quantitative optical imaging in standard homodyne-based ANSOM, can be suppressed. Periodic modulation of interferometric optical phase, typically employed in heterodyne-based ANSOMs even to such purpose, is not needed in the present configuration. Homodyne detection also facilitates detection of harmonic components of the ANSOM optical signal at the probe/sample distance modulation frequency, necessary for near-field discrimination and suppression of artifacts. Furthermore, since amplitude signal is not affected by phase fluctuations generated in the optical path of the interferometer, an optical fiber could be included in one interferometer arm, to couple the ANSOM head to the detection system, obtaining improved versatility of the instrument. A demonstration of the interferometer performance is given by a test confocal optical scan of a mirror surface. This technique, as applied to near-field microscopy, is anticipated to provide absolute values of optical contrast not depending on background interference and topography artifacts.
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The development of microminiaturized biosensors requires techniques for immobilizing biomolecules on solid substrates, in an ordered fashion, and techniques for the subsequent visualization of these patterns. Scanning force microscopy... more
The development of microminiaturized biosensors requires techniques for immobilizing biomolecules on solid substrates, in an ordered fashion, and techniques for the subsequent visualization of these patterns. Scanning force microscopy (SFM) is a useful technique for visualizing ordered patterns, but it requires suitable substrates and attachment techniques. Here we present a photolithographic method which gives ordered patterns of biomolecules. Both SFM topographic and lateral force images of these patterns are shown and discussed.
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ABSTRACT Voltage-modulated scanning force microscopy has been employed to investigate the dynamics of ferroelectric domains as a function of time and temperature in triglycine sulfate (TGS) single crystals. Branching of the domain... more
ABSTRACT Voltage-modulated scanning force microscopy has been employed to investigate the dynamics of ferroelectric domains as a function of time and temperature in triglycine sulfate (TGS) single crystals. Branching of the domain structure and nucleation of fine domain patterns by internal fields of thermal origin have been directly observed on the submicron scale. Domain coarsening after quenching TGS samples from the paraelectric phase into the ferroelectric one has been studied, revealing a nonlinear time dependence of the characteristic correlation domain length and supporting the validity of dynamical scaling law and the conservation of the total surface charge. Substantial differences in the evolution of the domain structure have been detected during cooling or heating treatment in the ferroelectric phase. Domain contrast is shown to monitor the ferroelectric phase transition through its temperature dependence, reflecting the competition between electrostatic and piezoelectric effects. © 2000 American Institute of Physics.
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Near-field optical spectroscopy has been used to investigate photoluminescence features of porous silicon microcavity samples with a subwavelength space resolution. The emission is found to be markedly dependent on the lateral position,... more
Near-field optical spectroscopy has been used to investigate photoluminescence features of porous silicon microcavity samples with a subwavelength space resolution. The emission is found to be markedly dependent on the lateral position, with the presence of relatively narrow spectral features peaked at different wavelengths in the range 610-690 nm. Furthermore, the spectrum obtained by summing up spectra taken at different
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... Massimiliano Labardi, Nicola Coppede`, Lucio Pardi, Maria Allegrini, and Marco Giordano INFM and Dipartimento di Fisica ''Enrico Fermi,'' Universita` di Pisa, Via F. Buonarroti 2, I-56127 Pisa (Italy) ... [4]... more
... Massimiliano Labardi, Nicola Coppede`, Lucio Pardi, Maria Allegrini, and Marco Giordano INFM and Dipartimento di Fisica ''Enrico Fermi,'' Universita` di Pisa, Via F. Buonarroti 2, I-56127 Pisa (Italy) ... [4] Patane`, S., Arena, A., Allegrini, M., Andreozzi, L., Faetti, M., & Giordano, M ...
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Abstract: Femtosecond pulses coupled to hollow-pyramid near-field probes allow achieving sufficient peak power to perform near-field nonlinear optics. We present second-harmonic generation images of nanostructured metal surfaces with... more
Abstract: Femtosecond pulses coupled to hollow-pyramid near-field probes allow achieving sufficient peak power to perform near-field nonlinear optics. We present second-harmonic generation images of nanostructured metal surfaces with spatial resolution better than 100 nm. © ...
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The paper reports on the achievement of material optical contrast on the nanoscale by means of apertureless near-field optical microscopy ANSOM with second-harmonic generation (SH-ANSOM). A grazing incidence illumination configurations... more
The paper reports on the achievement of material optical contrast on the nanoscale by means of apertureless near-field optical microscopy ANSOM with second-harmonic generation (SH-ANSOM). A grazing incidence illumination configurations adopted, with excitation of the tip dipole along its axis, and backscattering collection arrangement along the maximum emission direction. This optimized geometry resulted in a 2/3 orders of magnitude increase
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... (ii) Contrast in the optical image is rather high, up to 50%; (iii) Topography and optical images appear shifted by about 20 nm in the lateral direction; ... is plotted. Here, the lateral shift betweentopography and optical signal, as... more
... (ii) Contrast in the optical image is rather high, up to 50%; (iii) Topography and optical images appear shifted by about 20 nm in the lateral direction; ... is plotted. Here, the lateral shift betweentopography and optical signal, as well as the high optical contrast, are evident. ...
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Surface displacements of a few picometers, occurring after application of an electric potential to piezoelectric materials, can be detected and mapped with nanometer-scale lateral resolution by scanning probe methods, the most notable... more
Surface displacements of a few picometers, occurring after application of an electric potential to piezoelectric materials, can be detected and mapped with nanometer-scale lateral resolution by scanning probe methods, the most notable being piezoresponse force microscopy (PFM). Yet, absolute determination of such displacements, giving access for instance to materials’ piezoelectric coefficients, are hindered by both mechanical and electrostatic side-effects, requiring complex experimental and/or post-processing procedures for carrying out reliable results. The employment of quartz tuning-fork force sensors in an intermittent contact mode PFM is able to provide measurements of electrically-induced surface displacements that are not influenced by electrostatic side-effects typical of more conventional cantilever-based PFM. The method is shown to yield piezoeffect mapping on standard ferroelectric test crystals (periodically-poled lithium niobate and triglycine sulfate), as well as on ...
Abstract: Femtosecond pulses coupled to hollow-pyramid near-field probes allow achieving sufficient peak power to perform near-field nonlinear optics. We present second-harmonic generation images of nanostructured metal surfaces with... more
Abstract: Femtosecond pulses coupled to hollow-pyramid near-field probes allow achieving sufficient peak power to perform near-field nonlinear optics. We present second-harmonic generation images of nanostructured metal surfaces with spatial resolution better than 100 nm. © ...
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Scanning force microscopy in the dynamic contact mode with resonance enhanced domain contrast is applied to study in situ pattern formation and relaxation kinetics of ferroelectric domains on the cleavage surface of triglycine sulfate... more
Scanning force microscopy in the dynamic contact mode with resonance enhanced domain contrast is applied to study in situ pattern formation and relaxation kinetics of ferroelectric domains on the cleavage surface of triglycine sulfate subjected to successive annealing-cooling cycles. Substantial differences in the domain morphology and kinetics are disclosed upon cooling at temperatures close to Tc. Convolution of stripe domains with residual domain nuclei and random pinning forces due to intrinsic defects are suggested to account for variations in the domain structure and slowing down of domain kinetics.
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Voltage-modulated scanning force microscopy has been applied to investigate domain kinetics in triglycine sulfate single crystals, thermally quenched from the paraelectric to the ferroelectric phase. Temporal analysis of the equal-time... more
Voltage-modulated scanning force microscopy has been applied to investigate domain kinetics in triglycine sulfate single crystals, thermally quenched from the paraelectric to the ferroelectric phase. Temporal analysis of the equal-time correlation functions shows that the average domain size grows initially with a power law dependence close to that of conserved systems, whereas a crossover to the slower logarithmic growth law
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ABSTRACT Ultrathin film of poly (vinyl acetate) supported on different metallic substrates have been investigated to study confinement effects on relaxation dynamics. The characteristic frequency of structural relaxation increases on... more
ABSTRACT Ultrathin film of poly (vinyl acetate) supported on different metallic substrates have been investigated to study confinement effects on relaxation dynamics. The characteristic frequency of structural relaxation increases on decreasing thickness when the interfacial energy is less than roughly 3 mJ/m2, whereas it is thickness independent at about 3.5 mJ/m2. The growth of an interfacial polymer layer, insoluble in the commonly used solvent, has been found to grow during annealing for several days at a temperature much above the glass transition. The presence of such layer reduces the average confinement effect on the film. Such finding seems to reconcile several contradicting results previously reported.
ABSTRACT Superconductive/ferroelectric YBCO/PZT bilayer structures have been deposited by pulsed laser ablation on (100) MgO and substrates. Before the fabrication of the bilayer, optimization of the YBCO deposition parameters was carried... more
ABSTRACT Superconductive/ferroelectric YBCO/PZT bilayer structures have been deposited by pulsed laser ablation on (100) MgO and substrates. Before the fabrication of the bilayer, optimization of the YBCO deposition parameters was carried out to improve the electrical, morphological and structural characteristics of the films. The results of x-ray diffraction spectroscopy, resistance versus temperature measurements, atomic force and scanning electron microscopies demonstrate the growth of YBCO films suitable as bottom layers for subsequent PZT deposition. The superconductive/ferroelectric bilayers, as characterized by x-ray diffraction and scanning electron microscopy, demonstrate the presence of the correct lattice structures for both YBCO and PZT layers and a good surface morphology (i.e. the absence of cracks and holes and low droplet density). The ferroelectric capacitors realized by using the YBCO layer and evaporated gold dots as bottom and top electrodes, respectively, exhibit excellent ferroelectric behaviour (remanent polarization , coercive field ), suggesting that laser deposited YBCO/PZT bilayers are promising as candidates for the fabrication of non-volatile random access memory devices.
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Voltage-modulated scanning force microscopy is applied to study the temperature dependence of the ferroelectric domain structure of triglycine sulfate up to TC, the ferroelectric transition temperature. The polarization image contrast... more
Voltage-modulated scanning force microscopy is applied to study the temperature dependence of the ferroelectric domain structure of triglycine sulfate up to TC, the ferroelectric transition temperature. The polarization image contrast exhibits a power-law decrease as TC is approached, associated with the competition between Maxwell stress and the converse piezoelectric effect. Substantial differences in the static and dynamic domain patterns are detected for two samples of different aging conditions.
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Optical observation of the polarization domain structure of a ferroelectric material (triglycine sulfate) is achieved using a reflection apertureless near-field optical microscope operating with an electrical ac polarization of the tip.... more
Optical observation of the polarization domain structure of a ferroelectric material (triglycine sulfate) is achieved using a reflection apertureless near-field optical microscope operating with an electrical ac polarization of the tip. By showing that there is no detectable contribution of the converse piezoelectric effect of the sample nor of the electrical forces acting on the tip in the optical signal
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The effect of severe confinement on the dynamics of three different generations of hyperbranched polyesters of the Boltorn family is investigated by dielectric relaxation spectroscopy (DRS). The polymer chains are intercalated within the... more
The effect of severe confinement on the dynamics of three different generations of hyperbranched polyesters of the Boltorn family is investigated by dielectric relaxation spectroscopy (DRS). The polymer chains are intercalated within the galleries of natural montmorillonite (Na(+)-MMT), thus forming 1 nm polymer films confined between solid walls. The structure of the nanocomposites is studied with X-ray diffraction and the thermal behavior of the polymers in bulk and under confinement is determined by differential scanning calorimetry. The glass transition temperatures of the polymers show a clear dependence on the generation whereas the transition is completely suppressed when all the polymer chains are intercalated. The dynamic investigation of the bulk polymers reveals two sub-Tg processes, with similar behavior for the three polymers with the segmental relaxation observed above the Tg of each polymer. For the nanocomposites, where all the polymer chains are severely confined, the dynamics show significant differences compared to that of the bulk polymers. The sub-Tg processes are similar for the three generations but significantly faster and with weaker temperature dependence than those in the bulk. The segmental process appears at temperatures below the bulk polymer Tg, it exhibits an Arrhenius temperature dependence and shows differences for the three generations. A slow process that appears at higher temperatures is due to interfacial polarization.
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We propose an experiment to measure the dielectric function of a solid by employing as samples Atomic Force Microscopy cantilevers. The cantilevers are capable to reveal the radiation pressure due to reflection and absorption of the... more
We propose an experiment to measure the dielectric function of a solid by employing as samples Atomic Force Microscopy cantilevers. The cantilevers are capable to reveal the radiation pressure due to reflection and absorption of the light. This technique may be alternative to the simultaneous measurement of the reflectivity and transmissivity on thin samples, which is often hard to carry out. An assessment for silicon indicates the feasibility of the experiment.
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Single InxGa1-xAs/GaAs quantum dot photoluminescence spectra, obtained by low-temperature near-field scanning optical microscopy, are compared with theoretically derived optical spectra. The spectra show shell filling as well as... more
Single InxGa1-xAs/GaAs quantum dot photoluminescence spectra, obtained by low-temperature near-field scanning optical microscopy, are compared with theoretically derived optical spectra. The spectra show shell filling as well as few-particle fine structure associated with neutral and charged multiexcitons, in good agreement with the many-body calculations. There appears to be a greater tendency to charged-exciton formation, which is discussed in terms of
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... VV Afanas'ev, A. Stesmans 2027 Aluminum-seeded growth of microcrystalline Si thin film onto SnO2 substrate Chang Hyun Lee, Koeng Su Lim MAGNETISM AND SUPERCONDUCTIVITY 2030 Growth-induced... more
... VV Afanas'ev, A. Stesmans 2027 Aluminum-seeded growth of microcrystalline Si thin film onto SnO2 substrate Chang Hyun Lee, Koeng Su Lim MAGNETISM AND SUPERCONDUCTIVITY 2030 Growth-induced uniaxial anisotropy in grazing-incidence deposited magnetic films ...