Tutorial on Off-Axis Electron Holography

Abstract

Multiphoton laser scanning microscopy offers advantages in depth of penetration into intact samples over other optical sectioning techniques. To achieve these advantages it is necessary to detect the emitted light without spatial filtering. In this nondescanned (nonconfocal) approach, ambient room light can easily contaminate the signal, forcing experiments to be performed in absolute darkness. For multiphoton microscope systems employing mode-locked lasers, signal processing can be used to reduce such problems by taking advantage of the pulsed characteristics of such lasers. Specifically, by recovering fluorescence generated at the mode-locked frequency, interference from stray light and other ambient noise sources can be significantly reduced. This technology can be adapted to existing microscopes by inserting demodulation circuitry between the detector and data collection system. The improvement in signal-to-noise ratio afforded by this approach yields a more robust microscope system and opens the possibility of moving multiphoton microscopy from the research lab to more demanding settings, such as the clinic.

Electron holography of thin amorphous carbon films: Measurement of the mean inner potential and a thickness-independent phase shift

“…Data analysis was performed using the DALI program package [13], which was extended for the reconstruction of holograms. The details of the reconstruction procedure are outlined elsewhere [14]. Holograms were also taken at elevated specimen temperature using a Gatan 652 double-tilt heating holder operated by a Gatan 901 SmartSet hot-stage controller.…”

Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle

“…Vacuum reference holograms were acquired and used to remove distortions associated with the imaging and recording system of the microscope. 16 A mask with radius 0.2 nm À1 was used in reconstructing the hologram, resulting in a nominal spatial resolution of 5 nm. Figure 2 shows an off-axis electron hologram of the end of the W tip, recorded before a bias was applied to it, alongside reconstructed 2Â amplified phase images corresponding to bias voltages of 0, 10, and 20 V, respectively.…”

Growth of Au/Ag nanowires in thin surfactant solution films: An electron microscopy study

“…HRTEM and Electron holography were carried out on a Tecnai F20 Field Emission Gun TEM at 200 kV, equipped with a Möllenstedt biprism inserted in the Selected Area aperture [21]. Additional phase shifts of the beam due to the effect of the microscope optic elements were removed by acquiring a reference hologram (i.e.…”