Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

Abstract

Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle J. Appl. Phys. 116, 024305 (2014) Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with $10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.

In-situ visualization of the space-charge-layer effect on interfacial lithium-ion transport in all-solid-state batteries

“…Consequently, an SCL with separation of lithium-ion-depleted (electrolyte side) and lithium-ion-enriched (cathode side) regions on opposite sides of the interface is formed at the LCO/LPSCl interface. However, it should be noted that thus far, there have been no feasible methods to remove the electric field component due to the MIP difference from the DPC-STEM images at 0 V because the electric field due to the MIP difference at the interface changes after cathode/electrolyte contact 20 , 35 – 37 . Therefore, there is no doubt that the electric field due to the MIP difference interferes with the DPC-STEM result (only from the SCL) at 0 V to some extent.…”

“…To eliminate the extraneous interferences of the electric fields due to the MIP difference and possible DDE, the electric field result at 0 V is subtracted from that at the bias voltage. This goal of removing the electric field (MIP difference) effect at a bias voltage can be easily achieved because the formed electric field due to the MIP difference after cathode/electrolyte contact is constant 20 , 35 – 37 . That is, …”

Oxidation of Carbon Nanotubes in an Ionizing Environment

“…It is well-known that in the latter situations that the electrons or ions depart close to radially and that the electric field, being proportional to the applied voltage divided by the local tip radius, is highest at the points of highest curvature of the tip, which has been recently confirmed by electron holography. 67 Moreover, here the ions would be attracted over a large solid angle at the approximately hemispherical cap, again the reverse of the field ionization process. Field-ion images for instance typically cover an angle of more than 120° 66 showing that the high electric field emanates from an angular range of $1\frac{4}{3}\pi$ steradians or more.…”

In situ transmission electron microscopy of resistive switching in thin silicon oxide layers

“…In a specimen of uniform thickness, in the absence of electrostatic fringing fields, the measured phase is directly proportional to the potential averaged through the thickness of the specimen. In order to subtract the mean inner potential contribution from the recorded signal, differences between phase images recorded with different voltages applied across the SiO x layer were evaluated, as reported elsewhere [24].…”