A versatile ultra high vacuum sample stage with six degrees of freedom

Ellis, A W; Tromp, R. M.

doi:10.1063/1.4813739

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…To enable high resolution, large field-of-view LEEM imaging, the LEEM sample stage 52 was scanned in a rectangular pattern over the sample, taking an image at each position, leaving sufficient overlap (2 μm steps at a 4.7 μm field-of-view). To obtain meaningful deformation information from this, care needs to be taken to use a stitching algorithm that does not introduce additional deformation, i.e., as faithfully reproducing reality as the constituting images.…”

Section: Methodsmentioning

confidence: 99%

Imaging moiré deformation and dynamics in twisted bilayer graphene

et al. 2022

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In ‘magic angle’ twisted bilayer graphene (TBG) a flat band forms, yielding correlated insulator behavior and superconductivity. In general, the moiré structure in TBG varies spatially, influencing the overall conductance properties of devices. Hence, to understand the wide variety of phase diagrams observed, a detailed understanding of local variations is needed. Here, we study spatial and temporal variations of the moiré pattern in TBG using aberration-corrected Low Energy Electron Microscopy (AC-LEEM). We find a smaller spatial variation than reported previously. Furthermore, we observe thermal fluctuations corresponding to collective atomic displacements over 70 pm on a timescale of seconds. Remarkably, no untwisting is found up to 600 ∘C. We conclude that thermal annealing can be used to decrease local disorder. Finally, we observe edge dislocations in the underlying atomic lattice, the moiré structure acting as a magnifying glass. These topological defects are anticipated to exhibit unique local electronic properties.

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Section: Methodsmentioning

confidence: 99%

Imaging moiré deformation and dynamics in twisted bilayer graphene

et al. 2022

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“…To enable high resolution, large field-of-view LEEM imaging, the LEEM sample stage [47] was scanned in a rectangular pattern over the sample, taking an image at each position, leaving sufficient overlap (2 µm steps at a 4.7 µm field-of-view). To obtain meaningful deformation information from this, care needs to be taken to use a stitching algorithm that does not introduce additional deformation, i.e.…”

Section: Stitchingmentioning

confidence: 99%

Imaging moiré deformation and dynamics in twisted bilayer graphene

de Jong,

Benschop,

Chen

et al. 2021

Preprint

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“…2a). A bayonet fitting at the side of the cap allows for in situ mounting of the puck on the macor carrier piece [19].…”

Section: Leep Sample Holder and Electronicsmentioning

confidence: 99%

“…It contains an electron bombardment heater for temperatures up to 1450 K, fits onto the existing SPECS sample holder (described in Ref. [19]) and is only ≈ 1 cm 3 small (cf. Fig.…”

Section: Leep Sample Holder and Electronicsmentioning

confidence: 99%

Low-energy electron potentiometry

et al. 2017

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In a lot of systems, charge transport is governed by local features rather than being a global property as suggested by extracting a single resistance value. Consequently, techniques that resolve local structure in the electronic potential are crucial for a detailed understanding of electronic transport in realistic devices. Recently, we have introduced a new potentiometry method based on low-energy electron microscopy (LEEM) that utilizes characteristic features in the reflectivity spectra of layered materials [1]. Performing potentiometry experiments in LEEM has the advantage of being fast, offering a large field of view and the option to zoom in and out easily, and of being non-invasive compared to scanning-probe methods. However, not all materials show clear features in their reflectivity spectra. Here we, therefore, focus on a different version of low-energy electron potentiometry (LEEP) that uses the mirror mode transition, i.e. the drop in electron reflectivity around zero electron landing energy when they start to interact with the sample rather than being reflected in front of it. This transition is universal and sensitive to the local electrostatic surface potential (either workfunction or applied potential). It can consequently be used to perform LEEP experiments on a broader range of material compared to the method described in Ref[1]. We provide a detailed description of the experimental setup and demonstrate LEEP on workfunction-related intrinsic potential variations on the Si(111) surface and for a metal-semiconductor-metal junction with external bias applied. In the latter, we visualize the Schottky effect at the metal-semiconductor interface. Finally, we compare how robust the two LEEP techniques discussed above are against image distortions due to sample inhomogeneities or contamination.

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A versatile ultra high vacuum sample stage with six degrees of freedom

Cited by 8 publications

References 13 publications

Imaging moiré deformation and dynamics in twisted bilayer graphene

Imaging moiré deformation and dynamics in twisted bilayer graphene

Imaging moiré deformation and dynamics in twisted bilayer graphene

Low-energy electron potentiometry

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