Dynamic Behavior in Piezoresponse Force Microscopy

Frequency dependent dynamic behavior in Piezoresponse Force Microscopy (PFM) implemented on a beam-deflection atomic force microscope (AFM) is analyzed using a combination of modeling and experimental measurements. The PFM signal comprises contributions from local electrostatic forces acting on the tip, distributed forces acting on the cantilever, and three components of the electromechanical response vector. These interactions result in the bending and torsion of the cantilever, detected as vertical and lateral PFM signals. The relative magnitudes of these contributions depend on geometric parameters of the system, the stiffness and frictional forces of tip-surface junction, and operation frequencies. The dynamic signal formation mechanism in PFM is analyzed and conditions for optimal PFM imaging are formulated. The experimental approach for probing cantilever dynamics using frequency-bias spectroscopy and deconvolution of electromechanical and electrostatic contrast is implemented.Comment: 65 pages, 15 figures, high quality version available upon reques

Разработка имитационной модели системы электропитания тяжелого самолета

Работа посвящена проектированию модели системы электроснабжения тяжелого самолета в пакете прикладных программ Matlab Simulink и создания автоматизированного рабочего места в среде разработки Microsoft Visual Studio на языке программирования C++.This work is devoted to designing an electrical power generating system (EPGS) model for heavy aircrafts in the Matlab Simulink application package and creating an automatized working place within the Microsoft Visual Studio development environment in the programming language C +

Electrode size dependence of piezoelectric response of lead zirconate titanate thin films measured by double beam laser interferometry

The electrode size dependence of the effective large signal piezoelectric response coefficient (d(33,f)) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed electrode size dependence is shown to arise from a contribution from the substrate. The intrinsic PZT contribution to d(33,f) is independent of electrode size and is equal to the theoretical value derived assuming a rigid substrate. The substrate contribution is strongly dependent on the relative size of the electrode with respect to the substrate thickness. For electrode sizes larger than the substrate thickness, the substrate contribution is positive and for electrode sizes smaller than the substrate thickness, the substrate contribution is negative. In the case of silicon substrates, if the electrode size is equal to the substrate thickness, the substrate contribution vanishes, and the measured value of d(33,f) is equal to the theoretical value under the rigid substrate assumption. (C) 2013 AIP Publishing LLC.This is the publisher’s final pdf. The published article is copyrighted by AIP Publishing LLC and can be found at: http://www.aip.org/. Copyright Statement Basic Permissions Limited license IS GRANTED to individuals accessing this document and its component documents and/or files for the following personal, noncommercial uses: 1. Retrieving or printing a copy of any document or file mounted on this server 2. Establishing a link or links to any document or file mounted on this server Individuals accessing this document and its component documents and/or files are NOT GRANTED license to: 1. Alter a copy of any retrieved or printed document or file from this server 2. Distribute a copy (electronic or otherwise) of any document or file from this server without permission from the American Institute of Physics (direct requests to [email protected] 3. Charge for a copy (electronic or otherwise) of any document or file from this server. This server and its contents, unless otherwise indicated, are the property of the American Institute of Physics

Intercomparison of the northern hemisphere winter mid-latitude atmospheric variability of the IPCC models

We compare, for the overlapping time frame 1962-2000, the estimate of the northern hemisphere (NH) mid-latitude winter atmospheric variability within the XX century simulations of 17 global climate models (GCMs) included in the IPCC-4AR with the NCEP and ECMWF reanalyses. We compute the Hayashi spectra of the 500hPa geopotential height fields and introduce an integral measure of the variability observed in the NH on different spectral sub-domains. Only two high-resolution GCMs have a good agreement with reanalyses. Large biases, in most cases larger than 20%, are found between the wave climatologies of most GCMs and the reanalyses, with a relative span of around 50%. The travelling baroclinic waves are usually overestimated, while the planetary waves are usually underestimated, in agreement with previous studies performed on global weather forecasting models. When comparing the results of various versions of similar GCMs, it is clear that in some cases the vertical resolution of the atmosphere and, somewhat unexpectedly, of the adopted ocean model seem to be critical in determining the agreement with the reanalyses. The GCMs ensemble is biased with respect to the reanalyses but is comparable to the best 5 GCMs. This study suggests serious caveats with respect to the ability of most of the presently available GCMs in representing the statistics of the global scale atmospheric dynamics of the present climate and, a fortiori, in the perspective of modelling climate change.Comment: 39 pages, 8 figures, 2 table

Diurnal changes in middle atmospheric H2O and O3: Observations in the Alpine region and climate models

International audienceIn this paper we investigate daily variations in middle atmospheric water vapor and ozone based on data from two ground-based microwave radiometers located in the Alpine region of Europe. Temperature data are obtained from a lidar located near the two stations and from the SABER experiment on the TIMED satellite. This unique set of observations is complemented by three different three-dimensional (3-D) chemistry-climate models (Monitoring of Stratospheric Depletion of the Ozone Layer (MSDOL), Laboratoire de Météorologie Dynamique Reactive Processes Ruling the Ozone Budget in the Stratosphere (LMDz-REPROBUS), and Solar Climate Ozone Links (SOCOL)) and the 2-D atmospheric global-scale wave model (GSWM). The first part of the paper is focused on the first Climate and Weather of the Sun-Earth System (CAWSES) tidal campaign that consisted of a period of intensive measurements during September 2005. Variations in stratospheric water vapor are found to be in the order of 1% depending on altitude. Meridional advection of tidal nature is likely to be the dominant driving factor throughout the whole stratosphere, while vertical advection becomes more important in the mesosphere. Observed ozone variations in the upper stratosphere and lower mesosphere show amplitudes of several percent in accordance with photochemical models. Variations in lower stratospheric ozone are not solely governed by photochemistry but also by dynamics, with the temperature dependence of the photochemistry becoming more important. The second part presents an investigation of the seasonal dependence of daily variations. Models tend to underestimate the H2O diurnal amplitudes, especially during summer in the upper stratosphere. Good agreement between models and observations is found for ozone in the upper stratosphere, which reflects the fact that the O3 daily variations are driven by the photochemistry that is well modeled

Dynamic leakage current compensation in ferroelectric thin-film capacitor structures

We report on a measurement procedure to separate ferroelectric switching current and dielectric displacement current from the leakage current in leaky ferroelectric thin-film capacitor structures. The ac current response is determined for two adjacent frequencies. Taking advantage of the different frequency dependencies of the ferroelectric switching current, dielectric displacement current and ohmic current, the hysteresis loop is calculated without performing a static leakage current measurement, which causes a high dc field stress to the sample. The applicability of the proposed measurement procedure is demonstrated on a Pt/Pb(Zr,Ti)O-3/IrO2 ferroelectric capacitor revealing a high leakage current. (C) 2005 American Institute of Physics

Piezoresponse in the light of surface adsorbates: Relevance of defined surface conditions for perovskite materials

We report on the influence of a surface layer prevailing on perovskites on the piezoelectricity measured by piezoresponse force microscopy. Surface sensitive measurements show that this layer consists of chemisorbates and physisorbates. The surface layer can be removed to a large extent by heating the sample under ultrahigh vacuum conditions. It is shown that the effect of this treatment on the piezoresponse of the material is significant as the potential difference applied to the sample is no longer reduced by a voltage drop across the adsorbate layer. As a consequence the internal electric field is higher in comparison to the presence of a layer and so the piezoresponse is higher as well. (C) 2004 American Institute of Physics