The Hide-and-Seek of Grain Boundaries from Moire Pattern Fringe of Two-Dimensional Graphene

Grain boundaries (GBs) commonly exist in crystalline materials and affect various properties of materials. The facile identification of GBs is one of the significant requirements for systematical study of polycrystalline materials including recently emerging two-dimensional materials. Previous observations of GBs have been performed by various tools including high resolution transmission electron microscopy. However, a method to easily identify GBs, especially in the case of low-angle GBs, has not yet been well established. In this paper, we choose graphene bilayers with a GB as a model system and investigate the effects of interlayer rotations to the identification of GBs. We provide a critical condition between adjacent moire fringe spacings, which determines the possibility of GB recognition. In addition, for monolayer graphene with a grain boundary, we demonstrate that low-angle GBs can be distinguished easily by inducing moire patterns deliberately with an artificial reference overlayopen0

Materials advances through aberration-corrected electron microscopy

Over the last few years, the performance of electron microscopes has undergone a dramatic improvement, with achievable resolution having more than doubled. It is now possible to probe individual atomic sites in many materials and to determine atomic and electronic structure with single-atom sensitivity. This revolution has been enabled by the successful correction of the dominant aberrations present in electron lenses. In this review, the authors present a brief overview of these instrumental advances, emphasizing the new insights they provide to several areas of materials research

The benefits of energy-filtering in weak-beam microscopy

We have explored systematically the benefits of energy filtering to remove inelastically-scattered electrons with energy losses greater than about 10 eV from weak-beam images of dislocations. Digital weak-beam images were obtained of long dislocations in Ni3Ga using a Gatan Imaging Filter attached to a Jeol 3000F FEGTEM. The image quality was assessed in terms of three parameters: the image peak width; the peak-to-background ratio; and the signal-to-noise ratio. All three of these measures were significantly improved in "zero-loss" energy-filtered images compared with unfiltered images taken under the same imaging conditions particularly in thick areas of foil (> 100 nm), where unfiltered images were badly degraded by chromatic aberration. In a foil of thickness similar to180nm energy-filtered images were of comparable quality to those obtainable in thin areas of foil (< 50 nm)

Confocal operation of a transmission electron microscope with two aberration correctors

The authors demonstrate that confocal imaging trajectories can be established in a transmission electron microscope fitted with two spherical aberration correctors. An atomic-scale electron beam, focused by aberration-corrected illumination optics, is directly imaged by a second aberration-corrected system. The initial experiment described indicates how aberration-corrected scanning confocal electron microscopy will allow three-dimensional imaging and analysis of materials with atomic lateral resolution and with a depth resolution of a few nanometers. The depth resolution in the confocal mode is shown to be robust to the uncorrected chromatic aberration of the lenses, unlike depth sectioning using a single lens. © 2006 American Institute of Physics

HREM analysis of Sigma 3 {112} boundaries in gold bicrystal films

Gold bicrystal films, with foil normal along , have been observed in the Stuttgart JEOL ARM1250 and Oxford JEOL 300OF microscopes. Phase and modulus images of the Sigma3 {112} boundaries were reconstructed, images were simulated using models, and the arrangement of facets was considered

Aberration-corrected HREM/STEM for semiconductor research

Aberration correction leads to a substantial improvement in the resolution of transmission electron microscopes. The JEM-2200FS in Oxford (Begbroke site) is equipped with correctors for both TEM and STEM. Alignment of the TEM and STEM correctors is achieved through variations of the Zemlin tableaux. The microscope can be used to study the same or similar regions of a sample in both TEM and STEM modes