Nanodielectric mapping of a model polystyrene-poly(vinyl acetate) blend by electrostatic force microscopy

4 páginas, 4 figuras.-- PACS number(s): 61.41.+e, 62.23.-c.-- et al.We present a simple method to quantitatively image the dielectric permittivity of soft materials at nanoscale using electrostatic force microscopy (EFM) by means of the double pass method. The EFM experiments are based on the measurement of the frequency shifts of the oscillating tip biased at two different voltages. A numerical treatment based on the equivalent charge method allows extracting the values of the dielectric permittivity at each image point. This method can be applied with no restrictions of film thickness and tip radius. This method has been applied to image the morphology and the nanodielectric properties of a model polymer blend of polystyrene and poly(vinyl acetate).The financial support of Donostia International Physics Center (DIPC) is acknowledged. The authors would like to acknowledge the financial support provided by the Basque Country Government (Reference No. IT-436-07, Depto. Educación, Universidades e Investigación), the Spanish Ministry of Science and Innovation (Grant No. MAT 2007-63681), the European Community (SOFTCOMP program), and the PPF Rhéologie et plasticité des matériaux mous hétérogènes 2007–2010 Contract No. 20071656.Peer reviewe

Space Charge at Nanoscale: Probing Injection and Dynamic Phenomena Under Dark/Light Configurations by Using KPFM and C-AFM

International audienc

Vibration of the cantilever in Force Modulation Microscopy analysis by a finite element model

International audienceThe resonance frequency of the cantilever beam of a Force Modulation Microscope is studied in function of the beam shape, the sample stiffness, and the contact model. We used a one dimensional finite element model for the cantilever beam, which permits the exact vibration of the beam to be treated in the contact mode, whatever its shape (rectangular as well as triangular beams) and excitation mode (by the beam holder, by the sample, by a localized, or distributed force). Based on a classic finite element scheme, it is simple to program and as rapid as the usual analytical models. We demonstrate that the mode of excitation of the beam strongly influences the cantilever's frequency response in the contact mode. Anti-resonance is observed on the amplitude curves, which may perturb the measurements on some samples. We analyzed the true normal and tangential amplitude, for different beams and tip dimensions, in relation with the apparent amplitude of the vibration, as detected by the system. Experimental results on soft materials (polyurethane rubbers) give evidence of a nonsliding contact and underline the importance of an adequate treatment for the tangential forces, even in the linear domain. We assume a kind of viscosity of the contact, the effects of which are not visible for slow scan, but stick the tip and the sample together in the 10–100 kHz frequency range. This viscosity also induces an important damping of the resonance. ©2003 American Institute of Physics

Measuring dielectric properties at the nanoscale using Electrostatic Force Microscopy

14 páginas, 11 figuras, 1 tabla.-- et al.The financial support of Donostia International Physics Center DIPC is acknowledged. The authors would also like to acknowledge the financial support provided by the Basque Country Government Reference No. IT-43607, Depto. Educación, Universidades e Investigación, the Spanish Ministry of Science and Innovation Grant No. MAT 2007- 63681, the European Community SOFTCOMP program, the PPF Rhéologie et plasticité des matériaux mous hétérogènes 2007–2010, Contract No. 20071656 and the National Science Foundation (Grant No. NSF DMR-0606090).Peer reviewe

Dynamic atomic force microscopy operation based on high flexure modes of the cantilever

International audienc

A Promising Diagnostic Tool to Measure Interphase Properties

International audienc

HIGHER HARMONICS ATOMIC FORCE MICROSCOPE

The invention concerns a microscopic system with atomic force, comprising a probe tip placed on one end of a lever arm (2), oscillating means (1) adapted to oscillate said probe tip substantially based on the fundamental frequency of said lever arm, said system including control means (7) for controlling said oscillating means to vary the oscillation frequency of said tip based on a plurality of harmonics of said lever arm. The invention is characterized in that said control means comprise an input receiving a parameter representing an operating threshold of said system, to vary the oscillation frequency of said tip based on at least one harmonic of said lever arm when said signal corresponds to a state of said system higher than said operating threshold

Force gradient detection under vacuum on the basis of double pass method

International audienc

Sensitivity and resolution in noncontact electrostatic force microscopy in the case of a constant potential

International audienc

On the use of electrostatic force microscopy as a quantitative subsurface characterization technique: A numerical study

We present a numerical study on the use of electrostatic force microscopy (EFM) as a non invasive subsurface characterization technique. We discuss the ability to resolve a buried object in a dielectric matrix considering two parameters: the detectability (i.e., signal superior to the noise) and the lateral resolution. The effects of the dielectric constant, thickness of the sample, and depth at which the object is buried are quantified. We show that the sensitivity reached in EFM permits to characterize subsurface objects in a dielectric matrix. We demonstrate that both lateral resolution and detectability decreases when the tip object distance increases. On the other hand, these two quantities increase with the dielectric constant of the matrix. A first step toward EFM tomography is proposed for objects creating non correlated signals.Peer Reviewe