Incoherent illumination method with conventional electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 174-175
Author(s):  
Fumio Nagata ◽  
Tsuyoshi Matsuda ◽  
Tsutomu Komoda ◽  
Kiyoshi Hama
Keyword(s):  
Electron Microscope ◽  
Contrast Effect ◽  
Phase Contrast ◽  
Carbon Film ◽  
Large Angle ◽  
Image Resolution ◽  
Experimental Investigations ◽  
Objective Lens ◽  
Glancing Angle ◽  
Strong Excitation

When fine details of thin films are observed, the image are generally composed of both amplitude and phase contrast. The image resolution is sometimes limited by the granular background noise of supporting film which is due to the phase contrast effect by fairly coherent illumination(CI).In the present work, incoherent illumination(ICI) method has been studied to avoid the phase contrast effect using a conventional electron microscope(Hitachi HU-12A).The ICI method was made by enlarging the illumination angle(β) to be equivalent to the glancing angle(α=1.4x10-2 radians) of objective aperture. The large angle illumination was achieved by the strong excitation of an objective lens.At first, the properties of phase contrast in ICI image were studied as functions of beam divergence angle and defocus using a carbon film. Both analytical and experimental investigations show that the granular noise in a phase contrast image decreases as β is increased from l×l0-4 to l×l0-2radians.

Magnetic Domain Observation of an Amorphous Fe-Si-B Ribbon by Means of a High Voltage Scanning Electron Microscope

1981 ◽  
Vol 39 ◽  
pp. 320-321
Author(s):  
K. Tsuno ◽  
Y. Harada ◽  
T. Sato
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
High Voltage ◽  
Amorphous Ribbon ◽  
Image Resolution ◽  
Objective Lens ◽  
Magnetic Domains ◽  
Scattered Electron ◽  
Voltage Scanning ◽  
Scanning Electron

Magnetic domains of ferromagnetic amorphous ribbon have been observed using Bitter powder method. However, the domains of amorphous ribbon are very complicated and the surface of ribbon is not flat, so that clear domain image has not been obtained. It has been desired to observe more clear image in order to analyze the domain structure of this zero magnetocrystalline anisotropy material. So, we tried to observe magnetic domains by means of a back-scattered electron mode of high voltage scanning electron microscope (HVSEM).HVSEM method has several advantages compared with the ordinary methods for observing domains: (1) high contrast (0.9, 1.5 and 5% at 50, 100 and 200 kV) (2) high penetration depth of electrons (0.2, 1.5 and 8 μm at 50, 100 and 200 kV). However, image resolution of previous HVSEM was quite low (maximum magnification was less than 100x), because the objective lens cannot be excited for avoiding the application of magnetic field on the specimen.

Towards 1-Ångstrom-resolution STEM

1993 ◽  
Vol 51 ◽  
pp. 996-997
Author(s):  
H.S. von Harrach ◽  
D.E. Jesson ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
A Priori ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Annular Dark Field ◽  
First Results

Phase contrast TEM has been the leading technique for high resolution imaging of materials for many years, whilst STEM has been the principal method for high-resolution microanalysis. However, it was demonstrated many years ago that low angle dark-field STEM imaging is a priori capable of almost 50% higher point resolution than coherent bright-field imaging (i.e. phase contrast TEM or STEM). This advantage was not exploited until Pennycook developed the high-angle annular dark-field (ADF) technique which can provide an incoherent image showing both high image resolution and atomic number contrast.This paper describes the design and first results of a 300kV field-emission STEM (VG Microscopes HB603U) which has improved ADF STEM image resolution towards the 1 angstrom target. The instrument uses a cold field-emission gun, generating a 300 kV beam of up to 1 μA from an 11-stage accelerator. The beam is focussed on to the specimen by two condensers and a condenser-objective lens with a spherical aberration coefficient of 1.0 mm.

User Access to Lorentz Microscopy at the NCEM, LBNL, Berkeley.

1998 ◽  
Vol 4 (S2) ◽  
pp. 472-473
Author(s):  
K. Verbist ◽  
C. Nelson ◽  
K. Krishnan
Keyword(s):  
Electron Microscope ◽  
Phase Contrast ◽  
Limited Range ◽  
Objective Lens ◽  
Image Filter ◽  
Lorentz Microscopy ◽  
Differential Phase ◽  
Free Sample ◽  
User Access ◽  
Differential Phase Contrast

A standard Philips CM200FEG electron microscope, without the special Lorentz lens, has been optimized for Lorentz imaging. The necessary field-free sample region is obtained by switching off the objective lens in the free lens mode. The limited range of magnification is compensated for by a post-column Gatan image filter (GIF) which magnifies by a factor of _ 20. Fresnel imaging is performed by defocusing with the diffraction lens. The use of low angle diffraction, in combination with the apertures located at the selected area aperture plane, allow Foucault imaging. The TEM analog of differential phase contrast (DPC) imaging has been implemented. This method makes it possible to obtain quantitave induction maps of the in-plane magnetization. TEM DPC is based on a series of Foucault images, recorded with different incremental beam tilts, which are processed to yield images equivalent to the quadrant signals obtained by the STEM DPC technique.

Sideband imaging for sub-Å image resolution with an intermediate voltage conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 412-413
Author(s):  
William Krakow
Keyword(s):  
Electron Microscope ◽  
Transfer Function ◽  
Amorphous Materials ◽  
Image Features ◽  
Image Resolution ◽  
Objective Lens ◽  
Contrast Transfer Function ◽  
Image Artifact ◽  
Cornell University ◽  
The Many

The impetus for achieving sub-angstrom resolution in a CTEM was put in place several years ago at Cornell University in the laboratory of Professor Benjamin Siegel. Amongst the many activities in his laboratory was the mission to retrieve and restore the information contained in HREM images by correcting the deleterious effects of the objective lens contrast transfer function. At this time, micrographs of amorphous materials such as Ge were being studied elsewhere with the premise that tilting the illumination would lead to improved resolution. This in fact led to the observation of fringe-like image features which could not be explained in terms of an amorphous material's microstructure. At this time we were able to demonstrate in Professor Siegel's laboratory that the appearance of pseudo fringe structures was an image artifact produced by spatial filtering in the electron microscope of elastically and inelastically scattered electrons.

Phase contrast and interference microscopy with the electron microscope

1971 ◽  
Vol 261 (837) ◽  
pp. 95-104 ◽  
Keyword(s):  
Electron Microscope ◽  
Phase Contrast ◽  
Carbon Film ◽  
Optical Diffraction ◽  
Interference Microscopy ◽  
Phase Plate ◽  
Bright Field ◽  
Thin Carbon ◽  
Thin Carbon Film ◽  
Electron Interference

A simple electrostatic device has been constructed which, when inserted in the optical system of an electron microscope, functions as an absorbing phase plate. Its operation depends on the central portion of a thin poorly conducting thread generating a stable potential under the influence of the electron beam and creating a particular form of electric field. An electron interference technique is employed to study the stabilizing mechanism and to develop a method for achieving the required magnitude of potential. The performance of this device is gauged by optical diffraction of electron micrographs of a thin carbon film; its application is illustrated by examining some negatively stained biological specimens. The results indicate that such an ‘electrostatic phase plate’ can provide significant improvements in contrast and signal/noise ratio over normal bright field images without loss in resolution.

Image resolution in conventional transmission electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 468-469
Author(s):  
Mehmet Sarikaya ◽  
James M. Howe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Contrast Imaging ◽  
Conventional Transmission Electron Microscopy ◽  
Transmission Electron

The image resolution in bright-field (BF) and dark-field (DF) conventional transmission electron microscopy (TEM) is given by: r = 0.66 CS¼¾¾, where Cs and ¾ are the spherical aberration coefficient of the objective lens and electron wavelength, respectively. Based on this formula, it should be possible to resolve single atoms or clusters of atoms by phase contrast imaging with a highly coherent electron beam and a properly defocused objective lens; this has been demonstrated for both BF and DF imaging. However, for most situations encountered in conventional TEM, the type of information that can be obtained about the specimen is the most important, rather than the instrumental resolution. Atomicresolution microscopy of crystalline specimens relies on phase contrast produced when two or more beams interfere to form an image and this is discussed elsewhere in this symposium. This paper discusses the contrast and resolution when either a single beam or diffuse scattering is used to form an image.

Recent Development in Hitachi Transmission Electron Microscope

1983 ◽  
Vol 31 ◽  
Author(s):  
Shigeto Isakozawa ◽  
Isao Matsui ◽  
Shoji Kamimura ◽  
Akira Tonomura
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Image Resolution ◽  
Objective Lens ◽  
High Grade ◽  
Resolution Limit ◽  
Transmission Electron

The 200 kV electron microscope has been extensively utilized as a high grade model for diversified applications. This paper reports image resolution available at present with the Hitachi 200 kV Electron Microscope Model H-800 and possible techniques for improving present resolution limit which depends on the aberrations of objective lens.

A Technique For The Rapid Determination of the Contrast Transfer Characteristics of an Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 278-279 ◽  
Author(s):  
William Krakow ◽  
Kenneth H. Downing ◽  
Benjamin M. Siegel
Keyword(s):  
Rapid Determination ◽  
Carbon Film ◽  
Large Angle ◽  
Objective Lens ◽  
Transfer Characteristics ◽  
Thin Carbon ◽  
Family Of Curves ◽  
Relative Contrast ◽  
Thin Carbon Film ◽  
The Fourier Transform

A focal series of a thin carbon film in bright-field phase contrast has been used by Thon to obtain a family of curves that represent the contrast transfer characteristics of a particular objective lens as a function of the defocus value. The thin carbon film is assumed to be a weak phase object, and the light optical diffractogram gives the Fourier transform of each micrograph from which the relative contrast at each spatial frequency can be obtained for the corresponding amount of defocus.We have obtained the equivalent information from a single electron micrograph of a thin carbon film specimen tilted at a large angle (65°), see Fig. 1.

Dynamic Observation of a Surface Reconstruction of Au-Deposited Si Particle

1996 ◽  
Vol 54 ◽  
pp. 984-985
Author(s):  
T. Kamino ◽  
T. Yaguchi ◽  
M. Tomita ◽  
H. Saka
Keyword(s):  
Electron Microscope ◽  
Surface Reconstruction ◽  
High Vacuum ◽  
Metal Deposition ◽  
Image Resolution ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Sem Images ◽  
Analytical Tem ◽  
Electron Microscopes

Metal deposition is one of the most effective methods to reconstruct the surface structure of Si, and a number of studies using electron microscopes have been carried out. Endo et al. have studied Au-deposited Si(111) surface by ultra-high vacuum(UHV) scanning electron microscope(SEM), and obtained SEM images of 7 × 7 and 5 × 2-Au structure at 600°C. Ozawa et al. have observed Audeposited Si(111) surface by UHV-transmission electron microscope(TEM) and observed the formation of 5 × 2-Au structure at 700°C. Marks et al. have studied the structure of Au-deposited Si(lll) surface to reconstruct electronic potential on the surface.Recently, we developed a direct heating type- specimen heating holder consists of two heating elements, for use with a conventional analytical TEM, and applied to an in-situ study of the surface reconstruction of Au-deposited Si at high temperature. A schematic drawing of the heating holder is shown in Fig. 1. Tungsten wire with a diameter of 25εm was used as the heating elements. The upper heating element was used for metal deposition, in this case Au, and lower one for the heating of substrate material, in this case Si. The microscope used in the study is a H-9000NAR analytical TEM operated at 300kV. The spherical and chromatic aberration coefficients of the objective lens were 0.69 and 1.4mm, respectively, and the TEM image resolution was 0.175nm

Phase Contrast Images of Periodic and Quasi-Periodic Objects

1967 ◽  
Vol 25 ◽  
pp. 234-235
Author(s):  
T. Komoda
Keyword(s):  
Contrast Effect ◽  
Phase Contrast ◽  
Periodic Structures ◽  
Present Report ◽  
Objective Lens ◽  
Electron Microscopic ◽  
Contrast Transfer Function ◽  
Electron Microscopic Image ◽  
Optical Transfer ◽  
Illuminating Beam

The phase contrast effect due to defocussing of an objective lens is decisive factor for imaging of molecular details in electron microscopy. The effect was intensively investigated by Thon) for amorphous objects. The present report is concerned with the phase contrast effect for the objects having periodic structures such as crystals and that of quasiperiodic ones.The contrast of the electron microscopic image has been theoretically treated by Hanszen) within the frame of the optical transfer theory. Phase contrast images are explained with a phase contrast transfer function, which shows the selective imaging of Fourier spectrum of spacial frequencies (reciprocal of periods) in the potential distribution in the object. The function diminishes under the conventional operating condition of the electron microscope. Fluctuation of focus and angular divergence of the illuminating beam are predominant factors for the diminishing.

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