Highly efficient electron vortex beams generated by nanofabricated phase holograms

Grillo, Vincenzo; Gazzadi, Gian Carlo; Karimi, Ebrahim; Mafakheri, Erfan; Boyd, Robert W.; Frabboni, Stefano

doi:10.1063/1.4863564

Cited by 126 publications

(118 citation statements)

References 24 publications

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“…An optimization of the grating thickness together with the trench depth allows improving the diffraction efficiency depending on electron energy [28]. Alternatively, since silicon nitride windows can be considered weak-phase objects to the electron beam, blazed gratings can be manufactured in order to boost the diffraction efficiency into the CS-corrected probe and even suppress the transmitted beam [27,28]. Also, we propose using on-axis aberration correction by means of zone plates (circular gratings) [17,42] to further improve the usability, efficiency, and performance of holographic aberration correction.…”

Section: Discussionmentioning

confidence: 99%

“…Very high diffraction efficiencies for a particular diffraction order have been reported already [27,28].…”

Section: Wavefront Manipulation By Diffraction Gratingsmentioning

confidence: 99%

“…Unfortunately, the diffracted beam intensities I(1) have a relative diffraction efficiency of rel(1) =3.3% which reduces to an absolute diffraction efficiency abs(1) =2.5% for the first order diffracted beams. This is quite small compared to recent advances in grating manufacturing [27,28], hence there is significant room of improvement for future experiments. At the time the experiments had been performed we unfortunately were not able to measure the absolute beam currents.…”

Section: Demonstration Of Spherical Aberration Correctionmentioning

confidence: 99%

“…Since electron waves have significantly smaller wavelengths compared to light, diffraction gratings for electrons require patterning capabilities with nanometer accuracy over micron length scales as provided e.g. by focused ion-beam (FIB) preparation tools [27,28].…”

Section: Wavefront Manipulation By Diffraction Gratingsmentioning

confidence: 99%

“…The idea was adapted from light optics [20][21][22] after preliminary work with electron beams had predicted this effect [23]. This kind of "wavefront engineering" has already been used to produce arbitrary phase structures in both light [13,14] and electron beams [24][25][26][27][28][29]. In principle, this approach had also been used already for light-optical wave front reconstructions of early off-axis electron holograms [29b].…”

Section: Introductionmentioning

confidence: 99%

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Aberration corrected STEM by means of diffraction gratings

Linck¹,

Ercius

Pierce

et al. 2017

Ultramicroscopy

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Abstract:In the past 15 years, the advent of aberration correction technology in electron microscopy has enabled materials analysis on the atomic scale. This is made possible by complex arrangements of multipole electrodes and magnetic solenoids to compensate the aberrations inherent to any focusing element of an electron microscope. Here, we describe an alternative method to correct for the spherical aberration of the objective lens in a scanning transmission electron microscopy (STEM) using a passive, nanofabricated diffractive optical element. This holographic device is installed in the probe forming aperture of a conventional electron microscope and can be designed to remove arbitrarily complex aberrations from the electron's wave front. In this work, we show a proof of principle experiment that demonstrates successful correction of the spherical aberration in STEM by means of such a grating corrector (GCOR). Our GCOR enables us to record aberration-corrected high-resolution HAADF STEM images, although yet without any improvement in probe current and resolution. Author Contact Information:Dr. Martin Linck, CEOS GmbH, Englerstr. 28, D-69126 Heidelberg, Germany

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Section: Discussionmentioning

confidence: 99%

“…Very high diffraction efficiencies for a particular diffraction order have been reported already [27,28].…”

Section: Wavefront Manipulation By Diffraction Gratingsmentioning

confidence: 99%

Section: Demonstration Of Spherical Aberration Correctionmentioning

confidence: 99%

Section: Wavefront Manipulation By Diffraction Gratingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Aberration corrected STEM by means of diffraction gratings

Linck¹,

Ercius

Pierce

et al. 2017

Ultramicroscopy

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Diffraction holography for the phase retrieval of vortex beams

Venturi

Grillo

Karimi

et al. 2016

European Microscopy Congress 2016: Proceedings

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The problem of phase retrieval in electron microscopy is generally related to the characterization of electric and magnetic fields in materials, to the retrieval of crystallographic structure or to the imaging of very weakly scattering objects. Recently, increasing attention is payed to the phase retrieval of electron vortex beams (EVB) i.e. beams carrying orbital angular momentum (OAM) [1] [2] [3]. The difficulty in this case arises due to the presence of an inherent phase singularity. There exist various kinds of phase retrieval schemes, and they mainly divide into off‐ and on‐axis, whether the electron beam is displaced from the electro‐optical axis or not. Furthermore, they can be computational (iterative or deterministic) or interferential. In this work, we use interferometry with synthetic beam shaping [4] to retrieve the phase of an EVB. In particular, we use an off‐axis interferential method, where a reference beam interferes with a vortex beam in the diffraction plane. From the interference pattern it is then possible to retrieve the phase with Fourier methods. This method overcomes the difficulties on in‐line methods and can be applied to the diffraction of many nanometer‐sized features. For this experiment, two holograms have been closely spaced and imprinted with focused ion beam (FIB) on a Si 3 N 4 membrane [5]. The two holograms are fabricated close to each other in the same membrane window, and their diffraction patterns superimpose in the diffraction plane. The first produces the aimed EVB in the form of a Laguerre Gauss with topological charge 10, and the other one is a hologram with a parabolic modulation that produces the reference wave. A scanning electron microscope (SEM) image of the two holograms can be observed in figure 1a (the parabolic hologram is on top and the LG hologram is at the bottom). Their separate diffractions are shown in figure 1b and 1c.The EVB shows the expected circular symmetry and the dark region in the central region. Conversely, the parabolic beam is characterized by a fully circular diffraction. The visible set of fringes here come from the interference with the 0 th order background. An image of superposition diffraction pattern is shown in figure 2. The parabolic wave hologram has the effect of adding a uniform phase ramp to the phase of the LG hologram, resulting in a pitchfork pattern typical of the superposition of beams with an azimuthal and linear phase ramp. The phase reconstruction then proceeds as in conventional holography: the interference (figure 3a) is Fourier transformed (figure 3b), a sideband is isolated and back Fourier transformed to obtain the phase shift as in figure 3c. Here the spiralling phase is visible, winding up by 10 x 2π in a cycle as expected for this EVB. The parabolic phase effect can be easily removed but does not alter the topologic charge consideration. This case study opens the way to a reliable solution of the phase problem in low angle electron diffraction.

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Multi-beam ultrafast laser processing of free-standing nanofilms

et al. 2023

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In this study, femtosecond laser-based multi-beam interference laser processing on nanofilms with nanometer thicknesses was demonstrated. The resulting multi-hole, two-dimensional lattice pattern reflected a laser interference fringe formed on the surface of the nanofilm, with no breaks or cracks. In anticipation of the actual nanostructure fabrication, additional laser processing was performed to drill additional holes in the spaces between the existing holes, resulting in high-density multi-point hole drilling beyond the interference fringe pitch. Notably, processing materials with thicknesses close to 100 nm or less is difficult even with a state-of-the-art focused-ion-beam system. The presented method, in contrast, allows instantaneous, submicrometer-scale multi-point hole drilling of nanofilms over a large area, opening up a new frontier of nanoengineering. Future applications will include the fabrication of electron phase plates, membrane-based optomechanical devices, microelectromechanical systems, and engineering of atomic layer materials.

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Highly efficient electron vortex beams generated by nanofabricated phase holograms

Cited by 126 publications

References 24 publications

Aberration corrected STEM by means of diffraction gratings

Aberration corrected STEM by means of diffraction gratings

Diffraction holography for the phase retrieval of vortex beams

Multi-beam ultrafast laser processing of free-standing nanofilms

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