Small-angle lattice rotations in graphene on Ru(0001)

Man, Ka Lun; Altman, Michael S.

doi:10.1103/physrevb.84.235415

Cited by 33 publications

(37 citation statements)

References 41 publications

(89 reference statements)

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“…The former determines the information depth, the latter is inversely related in a nontrivial way via the electron source characteristics (source extension, energy spread) to the smallest lateral dimension that can be resolved in imaging 27 and to sample perfection. Compared to the transfer width of ∼300Å achieved with the LEEM on atomically flat surfaces, 25,28 the small effective transfer width observed here is due mainly to the roughness of the W(111) surface, which appears structureless in LEEM.…”

Section: Methodscontrasting

confidence: 73%

Growth, magnetism and ferromagnetic thickness gap in Fe films on the W(111) surface

Zdyb

Bauer

et al. 2013

Phys. Rev. B

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The growth, structure, and magnetism of Fe films on the W(111) surface were investigated using low energy electron microscopy (LEEM) and diffraction (LEED), spin polarized LEEM (SPLEEM), and work function measurements. In contrast to an earlier report that Fe grows with fcc structure following initial pseudomorpic layer growth, we observe no evidence of the formation of fcc Fe over the entire thickness range studied, up to 18 monolayers (ML). Observations are instead consistent with the formation of a well-ordered, laterally (tensile) strained bcc Fe layer that gradually relaxes vertically and develops increasing disorder with increasing thickness. Ferromagnetic order appears at 6 ML, but surprisingly vanishes at 8 ML, and reappears just as suddenly at 9 ML during Fe deposition at room temperature. Ferromagnetism between 6 and 8 ML also vanishes at only 5 deg above room temperature. The magnetization direction of a monodomain structure remains constant before and after the ferromagnetic thickness gap at 8-9 ML until the formation of a multidomain structure at about 12 ML. Variations of exchange asymmetry in spin-polarized elastic electron scattering are also observed with increasing film thickness, particularly above 12 ML, that indicate changes in the spin-polarized electron band structure above the vacuum level. The evolution of magnetism and exchange asymmetry with increasing thickness and the appearance of the ferromagnetic gap are attributed to structural and morphological changes in the strained Fe layer, which eventually lead to a relaxed although highly disordered bcc Fe layer.

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Section: Methodscontrasting

confidence: 73%

Growth, magnetism and ferromagnetic thickness gap in Fe films on the W(111) surface

Zdyb

Bauer

et al. 2013

Phys. Rev. B

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“…Each of the LEED images shown in this sectionare generated by the described summation procedure. Similar to the study of g/Ru(0001) by Man and Altman [41], we can analyze the LEED pattern of monolayer graphene phases on the Cu(111) facet and precisely determine the rotational alignment of the graphene layer. This can be achieved by measuring the rotational orientation of the first-order moiré beating spots and the fact that first-order moiré spots perform an augmented rotation Φ moiré,Cu =A×j in k-spaceif the graphene lattice is rotated by an angle j with respect to the underlying Cu(111) lattice.…”

Section: Indexing Moiré Cells Using Leeddatamentioning

confidence: 96%

“…We should point out that this resemblance addresses the k-space position but not the intensity of the spots. Man and Altman used the described 1:1 relation for first-order moiré diffraction spots in order to analyze minor variations of the lattice alignment of chemical vapor deposited (CVD)graphene with respect to the Ru(0001) substrate in a LEEM experiment, achieving a spatial resolution within the several nm range [41]. In this analysis, the approximatelyten-fold augmented rotation of first-order moiré spatial frequencies with respect to the rotation of the graphene lattice versus the Ru(0001) substrate allowed to precisely determine the orientation of the supported graphene layer.…”

Section: Indexing Moiré Cells Using Leeddatamentioning

confidence: 99%

Indexing moiré patterns of metal-supported graphene and related systems: strategies and pitfalls

Zeller

Günther

2017

New J. Phys.

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Recent citationsImaging the confined surface oxidation of Ni3Al (111) AbstractWe report on strategies forcharacterizing hexagonal coincidence phases by analyzing the involved spatial moiré beating frequencies of the pattern. We derive general properties of the moiré regarding its symmetry and construct the spatial beating frequency é K moir  as the difference between two reciprocal lattice vectors k i  of the two coinciding lattices. Considering reciprocal lattice vectors k i  , with lengths of up to ntimes the respective (1, 0) beams of the two lattices, readily increases the numberof beating frequencies of the nth-order moiré pattern. We predict how many beating frequencies occur in nth-order moirés and show that for one hexagonal lattice rotating above another the involved beating frequencies follow circular trajectories in reciprocal-space. The radius and lateral displacement of such circles are defined by the order n and the ratio x of the two lattice constants. The question ofwhether the moiré pattern is commensurate or not is addressed by using our derived concept of commensurability plots. When searching potential commensurate phases we introduce a method, which we call cell augmentation, and which avoids the need toconsider high-order beating frequencies as discussed using the reported´ ( )R 6 3 6 3 30 moiré of graphene on SiC(0001). We also show how to apply our model for the characterization of hexagonal moiré phases, found for transition metal-supported graphene and related systems. We explicitly treat surface x-ray diffraction-, scanning tunneling microscopy-and low-energy electron diffraction data to extract the unit cell of commensurate phases or to find evidence for incommensurability. For each data type, analysis strategies are outlined and avoidable pitfalls are discussed. We also point out the close relation of spatial beating frequencies in a moiré and multiple scattering in electron diffraction data and show how this fact can be explicitly used to extract high-precision data.

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“…SXRD studies, which allowed unprecedented resolution, have shown that the moiré structure has a periodicity of (25 × 25)C/(23 × 23)Ru [303,104]. Using LEEM coupled to micro-LEED experiments, it was found that the actual structure of the samples varies slightly about this second order R0 commensurability, with small deviations from R0 [316].…”

Section: Ru(0001)mentioning

confidence: 99%

Growth of epitaxial graphene: Theory and experiment

et al. 2014

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A detailed review of the literature for the last 5-10 years on epitaxial growth of graphene is presented. Both experimental and theoretical aspects related to growth on transition metals and on silicon carbide are thoroughly reviewed. Thermodynamic and kinetic aspects of growth on all these materials, where possible, are discussed. To make this text useful for a wider audience, a range of important experimental techniques that have been used over the last decade to grow (e.g. CVD, TPG and segregation) and characterize (STM, LEEM, etc.) graphene are reviewed, and a critical survey of the most important theoretical techniques is given. Finally, we critically discuss various unsolved problems related to growth and its mechanism which we believe require proper attention in future research.

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Small-angle lattice rotations in graphene on Ru(0001)

Cited by 33 publications

References 41 publications

Growth, magnetism and ferromagnetic thickness gap in Fe films on the W(111) surface

Growth, magnetism and ferromagnetic thickness gap in Fe films on the W(111) surface

Indexing moiré patterns of metal-supported graphene and related systems: strategies and pitfalls

Growth of epitaxial graphene: Theory and experiment

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