Low-noise cold-field emission current obtained between two opposed carbon cone nanotips during <i>in situ</i> transmission electron microscope biasing

Knoop, Ludvig de; Gatel, Christophe; Houdellier, Florent; Monthioux, Marc; Masseboeuf, Aurélien; Snoeck, E.; Hÿtch, Martin

doi:10.1063/1.4923245

Cited by 8 publications

(2 citation statements)

References 19 publications

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“…Bright field electron holography can be used to map the sample thickness [5], the mean inner potential of a sample [6], the electrostatic field [7] as well as the magnetic field [8] with sub nanometric resolution. More re-Preprint submitted to Elsevier cently, it has been shown that electron holography allows the charge on individual nanoparticles to be measured to a precision of one elementary unit of charge [9] or monitor in-situ the field emission from carbon cone nanotips [10]. In addition, based on the interference of one diffracted beam originating from two areas with different strain states, darkfield electron holography allows mapping the strain field with nanometer scale spatial resolution [4].…”

Section: Off-axis Electron Holography In a Transmissionmentioning

confidence: 99%

Optimization of off-axis electron holography performed with femtosecond electron pulses

et al. 2019

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We report on electron holography experiments performed with femtosecond electron pulses in an ultrafast coherent Transmission Electron Microscope based on a laser-driven cold field emission gun. We first discuss the experimental requirements related to the long acquisition times imposed by the low emission/probe current available in these instruments. The experimental parameters are first optimized and electron holograms are then acquired in vacuum and on a nano-object showing that useful physical properties can nevertheless be extracted from the hologram phase in pulsed condition. Finally, we show that the acquisition of short exposure time holograms assembled in a stack, combined with a computer-assisted shift compensation of usual instabilities encountered in holography, such as beam and biprism wire instabilities, can yield electron holograms acquired with a much better contrast paving the way to ultrafast time-resolved electron holography.

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Section: Off-axis Electron Holography In a Transmissionmentioning

confidence: 99%

Optimization of off-axis electron holography performed with femtosecond electron pulses

et al. 2019

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“…Off-axis electron holography, in combination with in situ electrical measurements, has previously been used to map local variations in electrostatic potential in samples that include electrically biased W microtips, 13 field emitting C nanotubes, 14 C cone nanotips 15 and p−n junctions in semiconductors. 16 In such applications, careful experimental design can be used to determine and subtract the contribution to the measured phase shift from the mean inner potential (MIP) of the specimen in order to retrieve the electrostatic potential associated with additional charge redistribution, such as that resulting from the presence of an applied voltage.…”

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confidence: 99%

Single Electron Precision in the Measurement of Charge Distributions on Electrically Biased Graphene Nanotips Using Electron Holography

et al. 2019

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We use off-axis electron holography to measure the electrostatic charge density distributions on graphene-based nanogap devices that have thicknesses of between 1 and 10 monolayers and separations of between 8 and 58 nm with a precision of better than a single unit charge. Our experimental measurements, which are compared with finite element simulations, show that wider graphene tips, which have thicknesses of a single monolayer at their ends, exhibit charge accumulation along their edges. The results are relevant for both fundamental research on graphene electrostatics and applications of graphene nanogaps to single nucleotide detection in DNA sequencing, single molecule electronics, plasmonic antennae, and cold field emission sources.

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Structural changes of Au nanocones during in situ cold‐field emission observed by high‐resolution TEM

Knoop

Voskanian

Yankovich

et al. 2016

European Microscopy Congress 2016: Proceedings

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In situ transmission electron microscopy (TEM) allows imaging on the atomic scale of complex physical phenomena, which are induced by an externally applied stimuli. This provides a directly observed correlation between material structure and properties, which promotes the understanding of the material and the triggered phenomena. Here, a Nanofactory in situ TEM biasing holder with a nanomanipulator has been used to both manipulate Au nanostructures and also to enable the studies of electron cold‐field emission (CFE). The conical shaped Au nanostructures are produced by hole‐mask colloidal lithography on an electron‐transparent carbon film in macroscopic short‐range‐ordered arrays [1]. Individual nanocones typically feature a tip radius of around 5 nm and a height of around 180 nm. The entire macro‐array is then transferred to a mechanically cut Au‐wire that subsequently was inserted into the in situ TEM holder (Fig. 1). The nanomanipulator of the TEM holder can move in 3D, with both coarse and fine motion. The coarse control utilizes a slip‐stick mechanism for a mm‐ranged motion. The piezo‐driven fine control has a range of 10 μm and a resolution on the sub‐Å level. The Au nanocones in Fig. 1 were transferred to the nanomanipulator, making the configuration seen in Fig. 2. The nanomanipulator was thereafter positioned opposite a nanocone that was in direct contact with the Au‐wire (Fig. 2). During the experiment, the electrical potential between the two cones was increased until the electric field around the cathode nanocone was sufficiently high (several volts per nm) to initiate CFE. Earlier work using a similar TEM holder reports about in situ CFE experiments using carbon‐based nanotips over a distance of a few hundreds of nanometer [2–4]. Here, the distance between the two Au nanocones is around 20 nm, allowing for simultaneous imaging at high resolution of both cones during CFE. This allows a better understanding of the CFE process and the effects of electron bombardment. At 115 V applied voltage with a CFE current, i e , of 4 μA, structural changes of the anode Au nanocone were observed. The change in structure started with a faceting at the apex of the anode nanocone. At the same time, the anode nanocone material was redistributed forming an elongated structure, making the anode nanocone thinner over a region that stretched over more than 30 nm from the tip towards the base. The elongation was a multi‐stage process, taking about 5 s to complete. See images in Figs. 3a and 3b, which are separated by 0.4 s. The electron bombardment current was kept in the μA‐range and resulted in an amorphization of the outmost atomic layers of the anode apex around 7 s after the structural changes of the nanocone had occurred. During these events, no structural changes were observed on the cathode. This indicates that the structural changes to the anode Au nanocone is an effect of electron bombardment by the emitted and accelerated electrons.

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Low-noise cold-field emission current obtained between two opposed carbon cone nanotips during in situ transmission electron microscope biasing

Abstract: Low-noise cold-field emission current obtained between two opposed carbon cone nanotips during in situ transmission electron microscope biasing.

Cited by 8 publications

References 19 publications

Optimization of off-axis electron holography performed with femtosecond electron pulses

Optimization of off-axis electron holography performed with femtosecond electron pulses

Single Electron Precision in the Measurement of Charge Distributions on Electrically Biased Graphene Nanotips Using Electron Holography

Structural changes of Au nanocones during in situ cold‐field emission observed by high‐resolution TEM

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