We present a method to determine the local dielectric permittivity of thin insulating layers. The measurement is based on the detection of force gradients in electric force microscopy by means of a double pass method. The proposed experimental protocol is simple to implement and does not need any modification of standard commercial devices. Numerical simulations based on the equivalent charge method make it possible to carry out quantification whatever the thickness of film, the radius of the tip, and the tip-sample distance. This method has been validated on a thin SiO 2 sample for which the dielectric permittivity at the nanoscale has been characterized in the literature. We also show how we can quantitatively measure the local dielectric permittivity for ultrathin polymer film of poly͑vinyl acetate͒ and polystyrene.

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).

Nowadays, the multi-scale modelling of wood has a great need for measurements of structural, chemical and mechanical properties at the lowest level. In this paper, the viscoelastic properties in the layers of a wood cell wall are investigated using the contact resonance mode of an atomic force microscope (CR-AFM). A detailed experimental protocol suitable for obtaining reproducible and quantifiable data is proposed. It is based on three main steps: sample preparation to obtain a good surface state, calibration of the contact modulus using reference samples, and image processing to produce the viscoelastic images. This protocol is applied on chestnut tension wood. The obtained topography and semi-quantitative viscoelastic maps are discussed with respect to the cell wall structure, sample preparation effects, and AFM measurement specificity compared with nanoindentation.

Electron paramagnetic resonance investigation of polar nanoregions mobility in the relaxor PbMg1/3Nb2/3O3 and solid solutions PbMg1/3Nb2/3O3 -PbTiO3 J. Appl. Phys. 111, 014104 (2012) The dielectric relaxation behavior of (Na0.82K0.18)0.5Bi0.5TiO3 ferroelectric thin film J. Appl. Phys. 110, 124109 (2011) Dielectric and spin relaxation behaviour in DyFeO3 nanocrystals J. Appl. Phys. 110, 124301 (2011) Dielectric relaxation and alternating current conductivity of polyvinylidene fluoride doped with lanthanum chloride J. Appl. Phys. 110, 114119 (2011) Defects control for improved electrical properties in (Ba0.8Sr0.2)(Zr0.2Ti0.8)O3 films by Co acceptor doping Appl. Phys. Lett. 99, 232910 (2011) Additional information on Appl. Phys. Lett.

In this work we present a new AFM based approach to measure the local dielectric response of polymer films at the nanoscale by means of Amplitude Modulation Electrostatic Force Microscopy (AM-EFM). The proposed experimental method is based on the measurement of the tip-sample force via the detection of the second harmonic component of the photosensor signal by means of a lock-in amplifier. This approach allows reaching unprecedented broad frequency range (2-3 × 10(4)Hz) without restrictions on the sample environment. The method was tested on different poly(vinyl acetate) (PVAc) films at several temperatures. Simple analytical models for describing the electric tip-sample interaction semi-quantitatively account for the dependence of the measured local dielectric response on samples with different thicknesses and at several tip-sample distances.

Atomic Force Microscopy in force modulation mode was used to study the elastic properties of the different fibre wall layers of the tension wood of holm oak and normal wood of boco. The method is based on the measurement of the resonance frequency of the microscope lever in contact with the sampie. This frequency is related to the reduced Young modulus E* = E/(I-v2) of the material, supposed to be isotropie. 'Elastic' images of the cell are obtained simultaneously with the topographie images, which allows the observation of the mechanical properties of the cells at a nanometric scale. Layers G, S1, S2 and ML can clearly be distinguished. By comparison with known materials an estimation of the absolute modulus is given in the range 5-20 GPa, but should be considered with caution, because the inherent anisotropy of the materials has not been taken into account.

Electrostatic force spectroscopy (EFS) operated in a conventional force gradient detection method allows determining local surface charges in epoxy samples. This is made possible through a detailed analysis of gradient versus DC voltage curves. The parabolic dependence of these curves is closely related to the charge density. Both maximum and origin-ordinate are key data from which it is possible to extract quantitative information on the detected charge. The study is based on the combined use of numerical and analytical simulations of the probe sample interaction. Excellent sensitivities to very low surface charge densities are reported.

The feasibility of detecting electrostatic gradients in the linear regime is shown under vacuum by combining intermittent contact atomic force microscopy and a double pass method. To achieve our goal, different flexure mode orders were employed. We show that the sensitivity of the frequency or phase shifts to a given gradient was reduced when the order was increased. This behavior is theoretically explained in quantitative agreement with the experiments. Thus, on the basis of different flexure mode orders, gradient detection can now be extended to other forces plus various environments, i.e., under vacuum or controlled atmosphere.