Observation of Electric Potential Distribution in Model Capacitor Sample Using Electron Holography

Abstract

The electrical potential distribution in a model capacitor specimen, made of single-crystalline BaTiO3 and thin Pt plates, has been revealed by electron holography. In order to represent the inherent potential distribution related to the capacitance, undesired phase information was eliminated by the analysis of electron holograms acquired in various conditions of applied voltage; the undesired information includes signals due to electrical charging, thickness variation, and modulation of the reference electron wave by a long-range electric field. The observation of electric potential showed reasonable agreement with simulation for the model specimen. (doi:10.2320/matertrans.MBW201108) depth electron holography studies on capacitor samples. These include unwanted phase information due to electrical charging which occurs during electron exposure to a non- conductive BaTiO3 region, significant change in the mean inner potential at the position of precipitates, thickness variation in the sample, Bragg reflections, and modulation of the reference electron wave caused by a long-range electric field. 5­8) These effects superpose artificial phase information on the observations. In order to reveal the inherent electric field distribution related to the capacitance, we need to reduce these undesired signals by using appropriate techniques. The purpose of this study was to obtain a method of precise electric-field imaging based on electron holography for electronic components, such as capacitors, containing stacked thin ferroelectric and metallic layers. In order to show the usefulness of electron holography for studies of capacitors, we employed a simple model specimen made of single-crystalline BaTiO3 layers and Pt electrodes, as shown in Fig. 1(a): this specimen reduces undesired phase informa- tion due to Bragg reflections in the BaTiO3 layers, which are particularly significant in polycrystalline materials. The model specimen did not include precipitates in the ferro- electric layer. We demonstrate that the inherent electric potential distribution in the capacitor can be obtained by suppressing the effects due to electric charging, modulation of the reference electron wave, thickness variations etc.