Observation of Dislocations in Metals by Means of Moiré Patterns on Electron Micrographs

Pashley, D. W.; Menter, J. W.; Bassett, G. A.

doi:10.1038/179752a0

Cited by 132 publications

(25 citation statements)

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“…[12,13] Figure 2A shows a Moiré pattern of the PS-b-PDMS spherical microdomains, over a 5 mm Â 5 mm patterned area, as measured by SEM. The L 0 of the copolymer was $24 nm, while the period of the surface pattern was 72 nm long.…”

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A Novel Approach to Addressable 4 Teradot/in.² Patterned Media

et al. 2009

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The application of block copolymers (BCPs) for the fabrication of ultra-high-density addressable arrays, such as bit-patterned media (BPM), has been hampered by the poor intrinsic limit of thin film technology for long-range lateral ordering and orientation control over microdomains. [1][2][3][4][5][6] Chemically patterned substrates have been used to induce lateral ordering and to control the orientation of microdomains. [7][8][9][10] However, the resolution scalability, defined here as the ratio of the period patterned onto the surface and the natural period of the BCP, was limited to about a factor of 2. Additionally, when anisotropic BCP microdomains, such as cylinders or lamellae, are used, their orientation normal to the film surface (necessary for pattern transfer) requires the use of surfaces having balanced interfacial interactions with the blocks of the BCP and the use of BCPs with blocks having near-equal surface energies. Alternatively, the BCPs must be in nonequilibrium states that are susceptible to relaxation during thermal conditioning. In addition, to achieve small features, the microdomains of the BCP must be small, requiring the BCP to be in the strong segregation limit. This restricts the number of BCPs that are useful in achieving such small size scales; otherwise, additives must be used to enhance the microphase separation. It would be far more desirable to develop a process using BCPs with symmetric microdomains (spherical), so that it would be possible to take advantage of the differences in the interaction of the blocks with the substrate and in the surface energies of the blocks. This would make the process far more versatile and applicable to many different BCPs.Here, we used a BCP with spherical microdomains and a patterned substrate comprising a semidense hole-tone pattern in an ultrathin preferential wetting layer. As shown in Figure 1, the substrate was pretreated with a preferential wetting layer with a thickness of <10 nm consisting of a polymer brush with selective affinity for the major block of the copolymer. The surface energy of the minor component is lower than that of the major component, forcing a preferential segregation of the minor component to the free surface. The minor component also has a preferential affinity for the shallow patterned hole areas, which were formed by selectively removing the brush layer via an electron-beam lithography (EBL) process. Under these conditions, the equilibrium, and thus thermodynamically stable, structure of a film having a thickness 1.5 times the centerto-center distance of the spherical microdomains in the bulk (1.5 L 0 ), will consist of the lower surface energy component at its surface, pinned spherical microdomains of the minor component block covering the patterned features, and an array of spherical microdomains imbedded within the thin film. The pinned spherical microdomains may be spherelike, hemispherical, or even pancakelike, depending on the relative sizes of the patterned features and the natural BCP spherical domains. The...

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A Novel Approach to Addressable 4 Teradot/in.² Patterned Media

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“…Crystal diffraction moiré fringes were discovered by Mitsuishi et al (1951) in an electron micrograph of a graphite crystal and have been actively studied in the field of electron diffraction (Hashimoto & Uyeda, 1957;Pashley et al, 1957;Bassett et al, 1958). In the X-ray field, Bonse & Hart (1965, 1966 observed moiré fringes with X-ray interferometers from a silicon crystal, Chikawa (1965Chikawa ( , 1967 observed them with an epitaxically grown CdS crystal and Lang & Miuscov (1965) observed them from a quartz crystal with a crack.…”

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Theoretical study of the properties of X-ray diffraction moiré fringes. I

Yoshimura

2015

Acta Cryst Sect A

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A detailed and comprehensive theoretical description of X-ray diffraction moiré fringes for a bicrystal specimen is given on the basis of a calculation by planewave dynamical diffraction theory. Firstly, prior to discussing the main subject of the paper, a previous article [Yoshimura (1997). Acta Cryst. A53, 810-812] on the two-dimensionality of diffraction moiré patterns is restated on a thorough calculation of the moiré interference phase. Then, the properties of moiré fringes derived from the above theory are explained for the case of a plane-wave diffraction image, where the significant effect of Pendellö sung intensity oscillation on the moiré pattern when the crystal is strained is described in detail with theoretically simulated moiré images. Although such plane-wave moiré images are not widely observed in a nearly pure form, knowledge of their properties is essential for the understanding of diffraction moiré fringes in general.

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“…ii t x y w x y  (1) where   , i w x y is the two-dimensional Dirac comb-function, i = 1,2 is the lattice number, and   , xy is the coordinate in the sample plane. The transmission function of the sample is given by the product of the two transmission functions corresponding to the two lattices       12 , , , , t x y t x y t x y  (2) which can be expanded as:…”

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Moiré structures in twisted bilayer graphene studied by transmission electron microscopy

2019

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We investigate imaging of moiré structures in free-standing twisted bilayer graphene (TBG) carried out by transmission electron microscopy (TEM) in diffraction and in-line Gabor holography modes.Electron diffraction patterns of TBG acquired at typical TEM electron energies of 80 -300 keV exhibit the diffraction peaks caused by diffraction on individual layers. However, diffraction peaks at the scattering angles related to the periodicity of the moiré structure have not been observed in such diffraction patterns. We show that diffraction on moiré structure can create intense diffraction peaks if the energy of the probing electrons is very low, in the range of a few tens of eV.Experimental diffraction patterns of TBG acquired with low-energy electrons of 236 eV exhibiting peaks attributed to the moiré structure periodicity are shown. In holography mode, the intensity of the wave transmitted through the sample and measured in the far-field can be enhanced or decreased depending on the atomic arrangement, as for example AA or AB stacking. Thus, a decrease of intensity in the far-field must not necessarily be associated with some absorption inside the sample but can simply be a result of a particular atomic arrangement. We believe that our findings can be important for exploiting graphene as a support in electron imaging.

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Observation of Dislocations in Metals by Means of Moiré Patterns on Electron Micrographs

Cited by 132 publications

References 6 publications

A Novel Approach to Addressable 4 Teradot/in.² Patterned Media

A Novel Approach to Addressable 4 Teradot/in.² Patterned Media

Theoretical study of the properties of X-ray diffraction moiré fringes. I

Moiré structures in twisted bilayer graphene studied by transmission electron microscopy

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Observation of Dislocations in Metals by Means of Moiré Patterns on Electron Micrographs

Cited by 132 publications

References 6 publications

A Novel Approach to Addressable 4 Teradot/in.2 Patterned Media

A Novel Approach to Addressable 4 Teradot/in.2 Patterned Media

Theoretical study of the properties of X-ray diffraction moiré fringes. I

Moiré structures in twisted bilayer graphene studied by transmission electron microscopy

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A Novel Approach to Addressable 4 Teradot/in.² Patterned Media

A Novel Approach to Addressable 4 Teradot/in.² Patterned Media